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3 Tips for Elite Swimming Turns

A swim race is broken down into a start, turn, and free swimming phases. Although shorter, the start and turn are vital aspects of the race, especially races of shorter distances. Practicing the start and turn can improve ~0.1 seconds per phase, a large sum in longer races.

The easiest method for measuring start and turn performance is to measure speed and time to a fixed distance, typically 7.5 and/or 15 meters from the wall. Unfortunately, these methods do not isolate the start and turn, as each swimmer must perform stroking before the 15-meter park. If using the 15-meter distance overestimates the start and turn race segments. 

Veiga (check out his great interview on backstroke turns) has a new produced for individually measuring the distance on the start and turn. This method measures exactly when the swimmer's head breaks the surface of the water. Previous work using this individualized turn method have not analyzed elite swimmers or race situations. 

Differences in Turns between Elite and Regional Swimmers

Knowing differences between elite and regional caliber swimmers is essential for helping regional swimmers become more elite. Veiga (2014) analyzed races from the 2008 Open Comunidad de Madrid for 100 and 200-m events (long course meters). The elite swimmers had FINA scores between 700 - 900 points and the regional swimmers had FINA scores between 500 - 700 points. 
  1. Traveled longer off the walls during butterfly and backstroke start and turns and the 200-m breaststroke turn.
  2. Male swimmers had longer distances in all race segments, regardless of skill. 
  3. The start and turn distances represented less than 24% for the 100-m and 22% of the 200-m races.
  4. The average velocity was faster for all the elite swimmers than the regional swimmers during all races.
  5. Differences in average velocity between race segments were obtained for all the events, regardless of the swimmers’ performance level or gender. The starting speed was 0.5–0.8 m/s faster than the free swimming speed, and average turning speed was 0.1–0.3 m/s faster than the free swimming speed.

What the Individual Test Demonstrated

These results showed measuring simply to 15-meters accounts for 2 - 5 meter of excessive measurement. 

Another important observation was that swimmers traveled longer than previously reported. This difference may be from the evolution and greater stress on dolphin kicking over the past few decades. 

3 Tips for Elite Swimming Turns

  1. If you are a butterfly or backstroke specialist seeking improvements, improving your dolphin kick speed and distance is essential.
  2. Also, swimmers can improve their underwater kicking by starting their kicking after gliding in the speed range of 1.9 - 2.2 m/s. This could enhance their kicking distance ~1 meter. 
  3. For breaststroke swimmers, perform longer glides during your underwater phase for the 200-meter distance. 

However, it is likely these elite swimmers only maximize the start and turn distances when a net gain in average velocity results. 


  1. Veiga S, Cala A, G Frutos P, Navarro E. Comparison of starts and turns of national and regional level swimmers by individualized-distance measurements. Sports Biomech. 2014 Sep;13(3):285-95. doi: 10.1080/14763141.2014.910265. Epub 2014 Jun 13.
By Dr. G. John Mullen received his Doctorate in Physical Therapy from the University of Southern California and a Bachelor of Science of Health from Purdue University where he swam collegiately. He is the owner of COR, Strength Coach Consultant, Creator of the Swimmer's Shoulder System, and chief editor of the Swimming Science Research Review.

Elite Swimmer Dolphin Kick Analysis

Take Home Points:
  1. A qualitative, kinematic and hydrodynamic analysis of Thiago Pereira (Brazil, 2012 OG silver
    medalist at the 400IM) underwater kick in a flume.
  2. In this trial, Thiago´s maximal knee and hip flexions were 112 and 148 degrees, respectively. The feet, knees, hip and shoulders vertical displacement were 0.49m, 040m, 0.16m and 0.21m;
  3. His Strouhal number was 0.54-0.40 between 1.5 and 2.0m/s making him almost as efficient as some cetaceans (dolphins and whales).

Researchers and sport analysis must adhere to ethic guidelines. For instance, in most countries we are not allowed to disclose the identity of our subjects. Not so long ago, researchers would share what they have done only after the study being concluded. These days, we live in such fast-paced world that people are eager to share what they are up to. The temptation to post on social media pictures and videos of testing sessions and data collections is very high. In several countries, if one posts this kind of audio/video recording will be in troubles with the Institutional Review Board or Ethic Committee. If such posts involve underage participants, things will be nasty for the researchers. Can you image to be the parent or guardian of a swimmer that was invited to be part of a research, you authorized and a few days later pictures of your child in trunks or swimsuit are online and his/her identity is not protected? I guess the answer depends from which region of the world you are reading this post. In several countries a lawsuit would be filed against the researchers and the university. Other countries have more relaxed guidelines though.

It is not only the researchers that are sharing information on social media. Swimmers also do it on regular basis. It is a nice way to keep in touch with the fans. As long as they are adults, the ones posting the audio/video recordings and it is a public post, there are no ethical concerns. A few weeks ago, Thiago Pereira (Brazil) was generous enough to share a couple of videos over some testing sessions that took place in a flume in Tenerife (Spain). In one post we can watch him performing the underwater kick. Eventually this video became viral among the Brazilian and Portuguese swimming fraternity. It was shared by more than 2,400 people. Just a little bit of History: Brazil is a former Portuguese colony that is independent since 1822. Both countries share the same language (Portuguese) and have a common cultural heritage. 

We can perform a three-fold analysis of Thiago´s underwater kick: (i) qualitative analysis (as a coach would do); (ii) basic kinematics (as done on regular basis by sports analysts); (iii) hydrodynamics (carried out mainly but not exclusively by researchers).

Analysis of Thiago Pereira

  • You may want to recap the main tips for a good underwater kick over here. You can also find
    some thoughts on the butterfly kick by Dana Vollmer (USA) and an analysis to her technique here.
  • Thiago shows a nice body alignment (head´s in neutral position; arms fully extended; upper part of the body is streamlined for as much as possible)
  • Wave motion (it seems to move all the way back to the feet; wave motion is not too wide so that would increase the drag force or impair the propulsion)
  • Kicking (feet are in plantarflexion, i.e. tiptoes; seem to be pointing slightly inwards to increase the propulsive area; ankles are flexible enough; there is a quick change of direction from the upbeat to the downbeat and from the downbeat to the upbeat; he bent slightly the knees and hip to help the kicking; kick is short, fast and seems to have a good tempo).

    Dolphin Kick Kinematics

    • The kinematic analysis of the underwater kick involves mainly the assessment of joint angles and joint vertical displacements.  
    • At least in this trial, Thiago´s maximal knee flexion was 112 degrees. Interestingly, in a sample of 19 international level swimmers Arellano (2002) reported an average angle of 113 degrees. His maximal hip flexion was 148 degrees.
    •  The feet, knees, hip and shoulders vertical displacement were 0.49m, 0.40m, 0.16m, 0.21m, respectively. So, we can see that the extremities of the body have a higher vertical displacement.  Hence, wave motion moves all the way back (i.e. caudal direction). We can find in the literature a few papers reporting the same thing (e.g., Hochstein and Blickhan, 2011).

      Dolphin Kick Hydrodynamics

      • The questions that most of you will have right now are: “why should we perform the wave motion? What is the advantage?” and “Is it possible to measure it? To quantify it?”
      • The wave motion (i.e. the vertical displacement of all major joints up and down as described earlier) will help to produce a vortex-wake. The same way fishes and cetaceans do it. When Thiago performs underwater kick the wake generated is very specific in the form of a sequence of vortices that alternate the direction of the rotation. While the feet moves one direction, creates a clockwise vortex, and then to the other, causing a counter-clockwise one (Arellano, 2002). Interestingly it was found that swimmers create this vortex in the front part of the body and then it will travel backwards (Mason et al., 1992) (Fig 1, bottom). Long story short: the vortex on the feet will produce thrust due to jet propulsion. That is why swimmers should perform the upbeat-downbeat and the downbeat-upbeat changes as fast as possible. A little bit of math: the circulation vortex increases with the angular speed and area. The induced velocity increases with the circulation vortex. Bottom line: if you are fast enough changing from up-down and down-up (i.e., short and fast kick) you increase the speed, likewise the circulation vortex and the induced velocity. Small and translating vortices are created in the end of the downbeat and no vortices at all are created in the end of the upbeat by poor swimmers (Arellano, 2002). Good swimmers created a big static vortex in the end of the downbeat and a small vortex in the end of the upbeat (Fig 1, top).
      • To quantify the efficiency of the wave motion we can compute the Strouhal number (St). In fluid mechanics St is defined as a “dimensionless number describing oscillating flow mechanisms” or “the ratio between unsteady and steady motion”. For the layman I would say that it is the ratio of tip-toe speed to body speed and enables us to monitor the optimal creation of thrust associated with jet and vortices. So, the lower the St (i.e. less jet needed for a given same speed) the better.
      • We can benchmark Thiago Pereira against other national and international level swimmers (Arellano 2002; von Loebbecke 2009 et al., 2009; Hochstein and Blickhan, 2011) and even against other animals such as cetacean (i.e., dolphins and whales) (Rohr and Fish, 2004). As expected, human swimmers were outperformed by their cetacean counterparts (fig 2). Overall the international level swimmers are better than the national counterparts.
      • I am not completely sure of the flow speed in Thiago´s trial. I got values between 1.7 and 2.2m/s over several attempts, but most of them at 2.0m/s (mode=2.0m/s). So my guess is that the trial was performed at around 2.0m/s. Anyway, I estimated his Strouhal number for a range of speed between 1.5 and 2.0m/s. Each red dot is his trial at different hypothetical speeds. As speed increases his Strouhal number decreases. He is clearly better than the swimmers reported in the literature. What is surprising is that at higher speeds he reaches values similar to some cetaceans. He is within the range of values often reported for dolphins and whales, i.e., between 0.2 and 0.4 (Taylor et al., 2003).
      • Short question for a short answer: “Why is the Strouhal number lower in cetaceans than humans?” Cetaeans have many vertebrae leading up to the end of the tail, which allow them to pass a much smoother wave. Humans have a very limited number of joints. So the increase of displacement along the length of the body is not smooth. Humans also have smaller propulsive areas and a few muscle-skeletal constrains. Elite swimmers, as Thiago are not cetaceans albeit are more flexible, have more strength and larger surface areas than poor swimmers.
      • How can one improve the Strouhal number (i.e. the wave motion efficiency during underwater kicking)? To start, the body speed must be the same or higher. Anything that would you make impair the forward speed, not good at all. So make sure that the forward speed is the same or increases. After that, improve the kicking tempo (i.e. less time to perform the kick) and decrease the kicking amplitude (i.e. less vertical displacement). Follow-up question: how can one improve kicking tempo and amplitude? There are several ways, I´ll cover only two key-factors: strength and conditioning and technique. The swimmer must build-up strength power (e.g., to improve the kicking tempo) and enhance the kicking technique (e.g. decrease the joints range of motions, notably the knee flexion and therefore the kicking amplitude).

      1. Arellano, R., Pardillo, S., & Gavilán, A. (2002). Underwater undulatory swimming: Kinematic characteristics, vortex generation and application during the start, turn and swimming strokes. In Proceedings of the XXth International Symposium on Biomechanics in Sports, Universidad de Granada
      2. Hochstein, S., & Blickhan, R. (2011). Vortex re-capturing and kinematics in human underwater undulatory swimming. Human movement science, 30(5), 998-1007
      3. Loebbecke, A. V., Mittal, R., Fish, F., & Mark, R. (2009). A comparison of the kinematics of the dolphin kick in humans and cetaceans. Human Movement Science, 28(1), 99-112
      4. Rohr, J. J., & Fish, F. E. (2004). Strouhal numbers and optimization of swimming by odontocete cetaceans. Journal of Experimental Biology, 207(10), 1633-1642
      5. Taylor, G. K., Nudds, R. L., & Thomas, A. L. (2003). Flying and swimming animals cruise at a Strouhal number tuned for high power efficiency. Nature, 425(6959), 707-711
      By Tiago M. Barbosa PhD degree recipient in Sport Sciences and faculty at the Nanyang Technological University, Singapore.

      Friday Interview: Dr. Ludovic Seifert Discusses Swimming Starts

      1. Please introduce yourself to the readers (how you started in the profession,
      education, credentials, experience, etc.).
      After a PE certificate in 1998 and swim coach certificate in 1999, I used to teach PE and to coach swimming in France for 4 years. Then I achieved a PhD degree in Sport Sciences in 2003, in the field of Biomechanics and Motor control. I mostly focus on coordination dynamics both for clean swimming part and start-turn. The starting point of my research question, which feeds my view of teaching and coaching, roots in systemic approach, and more precisely Complex dynamical system. In clear, it says « the whole is more that the sum of parts » ; to me it means that all internal components (limbs, joints, muscles, etc) but also external components (environmental and task constraints) interact and should be considered as coupled…so finally without internal-external view relating to an individual. In practice, it means I won’t try to correct a swimmer technique by giving a lot of instructions, in order to correct his technique in a microscopic way. Instead I approach the problem with a macroscopic view that focus on the main parameter of the behaviour…often the perceptual motor coordination (because coordination already means interaction between and within elements). Doing that means that I manipulate constraints, i.e., I set boundaries to the swimmers in order to prohibit unexpected behaviour instead of to prescribe desired behaviour. In fact I set a problem to involve problem solving in practice (and not through cognitive process) rather than telling them what to do (… the solution).

      2. You have done a lot of research on swimming, but I want to start by discussing your research on starts. What are some common flaws in swimming starts?
      Swimming start is a big compromise for me; a compromise between several choices: 
      1. React rapidly versus take time to provide high impulse. 
      2. Flat aerial trajectory for lower entry and gliding phase, which often means short aerial trajectory, risk of large hole and lead your to swim early versus pike trajectory to later encounter aquatic resistance, which often corresponds to deep dive, higher CoM speed at the entry, cleaner entry but the need to recover parallel position to the water surface, so potentially lost of speed.
      3. Last swimmer has to deal with more or less glide part before kicking and swimming, with the need of hydrodynamic and effective swimming. 
      3. Do you think there are any kinetic or kinematic differences between breast, fly, or freestyle starts?
      I see the main differences during the aquatic part, especially time dedicated to glide …particularly in breaststroke where you perform a complete arm strike, then glide with the arms at the tight before moving them forward. I would say, that there is also the great interest of doing leg undulation in both fly and freestyle that need a particular attention to perform effective leg undulation 

      4. With the evolution of underwater kicking, do you think starts will change at all to accommodate more underwater kicking?
      I think it would depend on the capability of swimmer to perform effective leg undulation personally I would favour high acceleration through a medium vertical amplitude, so involving stroke rate rather ample undulation.

      5. You published on an article on the kinetic and kinematic differences between elite sprinters, what were the main findings?
      The main findings related to the need of considering individual characteristics to have an individual approach of start. I does not mean necessary individual style but to lead swimmer to discover his most efficient technique. Indeed, it’s quite different to swing the arms forward or backward during the impulse. While the first solution favours flight, the second favour rotation so different aerial trajectories may happen. According to the compromise I presented earlier, swinging the arms forward or backward will lead you to solve differently the compromise. 

      6. Do you think these starting styles and differences still exist with the new Omega OSB 11 kick back starts?
      The new Omega OSB 11 only stop previous debates between grab and track start, but not the debate between forward or backward swing of the arms. So there is still place for exploring his own feeling of performing start. However, a the legs push off could be really support by the block, it would increase the importance of a good arm-leg coordination. 

      7. What progressions or areas do you think elite sprinters can still improve in their start?
      As stated previously, one way of improvement is the good co-ordination between arms swing and leg impulse…still with a compromise between quick start or long push off.

      8. In your discussion you stress the importance of individualization, are there any parameters or anthropomorphics to help a coach prescribe a starting style to each individual?
      Individualized training mostly relates to have an individual approach of training (instead of applying theory in practice with a consideration of expert model in mind that should be imitated) rather than looking for the individual characteristics to prescribe a style. I’m not comfortable with « prescribing » strongly what to do. I’m confident with the ability of swimmers to explore and to solve the perceptual motor task I request.

      9. What drills or practices do you think are best for improving a start?
      I like disrupting with routine, so I like introducing variability in practice. It does mean « always different » but very slight differences in the instructions every 3 or 4 trials…instructions being mostly on the movement outcome rather than on the movement form. I usually formulate my instructions as « find the way of… ». I also like using analogy, i.e., giving biomechanical metaphor.

      10. Do you think starts are practiced enough on swim teams? If not, how often would you suggest practicing starts?
      I’ve not a clear idea of how start is performed over sea, but around me, we don’t take enough time to practice start. I would prefer to practice it more often to stabilize learning and under different conditions (fresh, fatigue, following by sprint or not, under temporal pressure or long concentration).

      11. What research or projects are you currently working on or should we look from you in the future?
      As I stopped coaching swimming, I also move my research topics to learning especially following what we call non-linear pedagogy (see recent publication of Jia Yi Chow and colleagues for a good example). It’s more or less what I explain previously about using constraints-led approach rather than prescriptive approach.

      I also focus on how using technology in swimming to provide rapid feedback, especially using IMU (inertial measurement unit combing 3D accelerometer, 3D gyroscope, 3D magnetometer) to assess joint angle, instantaneous speed etc. For an example, see recent paper of Farzin Dadashi with whom I collaborated.

      Leg Force During Swimming Starts

      Take Home Points on Leg Force During Swimming Starts

        1. Swimmers, who possess greater isometric maximum force and specific rate of force development at absolute and relative levels, tend to be able to swim faster on initial 10m swim start performance

        It has been suggested lower body strength and starting performance are correlated. Yet, research on elite swimmers is scarce, specifically sprint swimmers. The swimming start has been significantly correlated with 50m freestyle performance in elite male swimmers, as it accounts for 7.7 – 15% of the total race.

        Beretic (2013) had twenty-seven high-level trained male competitive swimmers (~21.1 years; mean 50 LCM 24.36) perform two trials of standing leg extensors isometric muscle force testing and three swimming start trials corresponding to 10m distances.

        Beretic et al. found the average start time significantly correlated with variables of leg extensors maximum voluntary force, leg extensors relative muscle voluntary force, leg extensors specific rate of force development, and leg extensors relative value of specific rate of force development.

        Leg extensors maximum voluntary force, leg extensors specific rate of force development, relative voluntary isometric force of the leg extensors, and relative leg extensors specific rate of force development showed significant correlation with times to 10m.
        These results suggest  having greater isometric force development of the hip extensors correlates with a faster initial 10m swim start performance. It seems the relative force production is more important than maximum force, as the short period on the block likely doesn’t allow maximal force to be achieved.

        The author's note the following key points:

        • Leg extensors maximum voluntary force, leg extensors relative value of maximum muscle voluntary force, leg extensors specific rate of force development and leg extensors relative value of specific rate of force development positively associated with the start time measured on 10m mark.
        • Time at 10m-mark was not associated with legs extensors basic level of rate of force development at absolute and relative level.
        • Obtained multi-regressional model is defined by variables which measure the development of maximum voluntary isometric leg extensor muscle force on the absolute and relative level, as well as variables which measure the development of specific explosive force of the same muscle group on absolute and relative level, this could use as a tool for swimming coaches to control the direction and extent of development of a given force characteristics for providing conditions for start improvement in highly trained elite male sprint swimmers.

        Future studies must assess if improving this force production improves starting performance, as well as look at the omega track starts and their correlation with performance. Once again, the we cannot differentiate correlation and causation, however as Bishop (2009) noted, improving on land power compared to no other form of training in moderately trained adolescent swimmers improves starting performance. However, the lack of specificity questions the use of resistance training for swimming starts, yet more research is needed. 

        1. Beretic I, Durovic M, Okicic T, Dopsaj M. Relations Between Lower Body Isometric Muscle Force Characteristics and Start Performance in Elite Male Sprint Swimmers. J of Sports Sci and Med. 2013 Dec; 12, 639 – 645.
        2. Bishop DC, Smith RJ, Smith MF, Rigby HE. Effect of plyometric training on swimming block start performance in adolescents. J Strength Cond Res. 2009 Oct;23(7):2137-43. doi: 10.1519/JSC.0b013e3181b866d0.
        3. Blanksby, Brian, Lee Nicholson, and Bruce Elliott. "Swimming: Biomechanical analysis of the grab, track and handle swimming starts: an intervention study." Sports Biomechanics 1.1 (2002): 11-24.

        Written by G. John Mullen received his Doctorate in Physical at University of Southern California (USC) and is a certified strength and conditioning specialist (CSCS). At USC, he was a clinical research assistant performing research on adolescent  diabetes, lung adaptations to swimming, and swimming biomechanics. G. John has been featured in Swimming World Magazine, Swimmer Magazine, and the International Society of Swim Coaches Journal. He is currently the owner of COR, providing Physical Therapy, Personal Training, and Swim Lessons to swimmers and athletes of all skills and ages. He is also the creator of the Swimmer's Shoulder SystemSwimming ScienceSwimming Science Research Review, and the Swimming Troubleshooting System.

        2014 NCAA Swimming Championship Relay Performances

        Take Home Points on 2014 NCAA Championship Relay Performances

          1. Team relay performances correlated with overall team finish for the men
          2. Georgia overcame a relay deficit to capture the women's title
          3. Men's teams placing 7-10 overall were not among top 10 relay teams

          Relays are undoubtedly among the most exciting races in college swimming, particularly in national championships.  With much publicity added this year due to a rash of disqualifications, relay performance has come under additional scrutiny. 

          Though relays are often assumed to be a deciding factor in many championships, it is worth closer examination to determine to what extent relays may affect point totals.  Now, it is difficult to completely separate relay performance from individual performance due to individuals also making up relay teams.  But looking at the point total breakdown may also lend perspective into the relative importance relays for the meet's outcome. 

          For additional discussion on technical elements of relay starts and finishes, see Relay Starts: Championship Implications, and How the New Omega Starting Blocks Affect Relay Takeoffs.

          In the chart below, we list both the final point total for the top 10 squads and top 10 relay placings for the five total relay events.  

          Though the top three times were identical in relays and total points, Michigan and Georgia both improved their overall placing above Auburn on the strength of individual events.  Also of note is that Arizona, USC, Stanford, and Indiana all cracked the top 10 despite not being among the top 10 relay scoring teams for the meet.  

          The chart below summarizes the women's breakdown.

          What stands out most here is that Georgia resoundingly made up the relay performance gap through consistent individual performances throughout the meet, despite Stanford almost sweeping the relay events.  Unlike the men, where several teams entered the overall top 10 without being among the top 10 relay scoring teams, each of the top 9 women's squads was also among the top 9 relay scoring teams.  

          Though relays are critical for overall outcome, it is still possible to make up placing if a team is outperformed in relays for the meet.  Relays and individual events both reward team depth, but in different ways.  Putting together a winning relay and stacking an individual event final are both potential winning strategies. 

          Written by Allan Phillips is a certified strength and conditioning specialist (CSCS) and owner of Pike Athletics. He is also an ASCA Level II coach and USA Triathlon coach. Allan is a co-author of the Troubleshooting System and was selected by Dr. Mullen as an assistant editor of the Swimming Science Research Review. He is currently pursuing a Doctorate in Physical Therapy at US Army-Baylor University.

          Relay Starts: Technique and Championship Implications

          Take Home Points on Relay Starts

          1. Relay exchanges can improve team standing at national championship meets.
          2. Literature has shown little significant difference in different start styles, indicating personal preference may be the deciding factor.
          3. Perfecting relay exchanges requires practice with the same teammates.

          A few months ago, Herbie Behm offered an insightful post on how the new Omega start platforms may affect relay start technique.  In this post, we’ll follow up with some descriptive statistics on the implications of relay performance and practical strategies for teams to utilize. 

          Relays are among the most exciting events in the pool, especially with championship season now upon us.  Though swimming is one of the most individual sports around, relays offer swimmers the chance to truly feel part of a team in the heat of competition.  Championship meets can literally come down to perfectly executed relay exchanges and also relay disasters with the dark cloud of disqualifications always looming darkly around the natatorium.

          We all know relays are important, but just how important are relay exchanges?  Siders (2010) compiled statistics from 2007 and 2008 NCAA Division I and II championships.  Data included 1292 teams in covering all relay events.  Key findings included…
          • Mean relay exchange time was 0.248 seconds for individuals and 0.746 seconds for teams. 
          • Relay exchanges catapulted a team ahead in the rankings in 15.8% percent of races. 
          • This study also examined disqualifications and found that 91% of DQ’s were by margins smaller than 0.09 seconds.  Most disqualifications were in medley races with 65% of DQ’s occurring in these events.  Including both freestyle and medley relays, 200 yard races (4 x 50yd) accounted for 56% of DQ’s. 


          What does the literature say about optimal relay start technique?  This site has covered starts in great depth, but relay starts have some unique factors, most notably timing with the in-water swimmer. 

          McLean (2000) examined three types of relay starts: one step approach, two step approach, and no step. Findings included:
          • Time to 10m was not significantly different between conditions.
          • Double step increased horizontal velocity by 0.2m/s.
          • Single step decreased vertical takeoff velocity by 0.2m/s but increased takeoff height by 0.16m
          • Horizontal velocity was significantly reduced by 0.1m/s in the double step start but vertical takeoff velocity was increased by 0.2m/s in single-step condition.
          • Conclusion: (Single and double) step stars offered some performance improvements over no-step start, but improvements were not widespread, and in the case of the double-step start, were dependent on the ability to take longer steps. 
          With the research somewhat inconclusive on optimal technique, we are left to observation to select the best strategy.  Russell Mark at USA Swimming (2011) argues for the “track to two feet jump” start as the ideal balance between speed and risk management.  Notably, of the 15 different Americans competing in championship finals at 2011 Worlds, 12 utilized this approach. 

          Practical Implication

          Also consider this reminder from Rowdy Gaines (1994): “Three words of advice for the incoming swimmer: Stick the wall! Do not ever let up the last five meters of any race, especially in a relay where timing is so critical. I do not breathe the last four or five strokes so I can keep my rhythm and zero in on the wall like radar. If you have to be one or the other, be long on the wall rather than taking an extra half-stroke. That is where most of the problems exist, especially in a fly-free exchange. 

          Relays can decide a meet, but relay exchanges are often overlooked at practices.  Though we often focus on the swimmer on the blocks, the swimmer in the water is equally crucial for a quick exchange.  Relay technique and team coordination are both crucial to fast and legal relay exchanges.    


          1. Siders, W.   Research Notes: Competitive Relay Exchange Times: A Descriptive Study.  International Journal of Sports Science and Coaching (1747-9541), 5 (3), p.381.
          2. Gaines, Rowdy.  Freestyle Relay Starts.  http://www.swimmingworldmagazine.com/articles/swimmagazine/articles/199407-01swim_art.asp
          3. Mark, Russell.  Relay Starts: Which Approach is Best http://www.usaswimming.org/ViewNewsArticle.aspx?TabId=1&itemid=3965&mid=8712
          4. McLean, S.P., Holthe, M., Vint, P.F., Beckett, K.D., and Hinrichs, R.N. (2000). Addition of an approach to a swimming relay start. Journal of Applied Biomechanics, 16, 343-356.
          Written by Allan Phillips is a certified strength and conditioning specialist (CSCS) and owner of Pike Athletics. He is also an ASCA Level II coach and USA Triathlon coach. Allan is a co-author of the Troubleshooting System and was selected by Dr. Mullen as an assistant editor of the Swimming Science Research Review. He is currently pursuing a Doctorate in Physical Therapy at US Army-Baylor University.

          Friday Interview: Dr. Jose M. Saavedra, Ph.D. Discusses the Omega Track Starts

          1. Please introduce yourself to the readers (how you started in the profession,

          education, credentials, experience, etc.).
          My name is Jose M. Saavedra. I am Associate Professor of the Faculty of Sports Sciences (University of Extremadura, Spain), and I am the coordinator of the AFIDES Research Group.

          I did my Bachelor’s degree in Physical Education at the Universidade da Coruña, Spain (1994), and my Doctorate in Physical Education (2002) in that same university with the Thesis entitled: “Multidimensional assessment and performance in national swimmers” I was Head Coach of the Swimming Club “Club Fluvial de Lugo” (1994-1999).

          I've been teaching both BSc and MSc classes related to water activities and swimming for over 15 years. I have been participating in different research projects, and so far these have resulted in 29 articles published in JCR indexed journals. Of these articles, 11 are related to swimming, water polo, and water activities.

          On a personal level, I was in the swim team of the Club Natación Coruña, and participated in various Absolute Championships of Spain.

          2. You recently published an article on the trends relationship between the block times in the traditional vs. new starting platforms. Why is it important to understand this trend?
          The new platform has led swimmers – especially those who use the two-footed grab start – to adapt their start technique to the new circumstances. This has necessarily influenced block times. Also, knowledge of the relationship between block time and final performance in these events would allow coaches to consider in greater depth the potential of conducting specific training to improve the start [Omega Track Start Tragedies Part I and Part II].

          3. What do we know about the new starting platforms?
          We know that, with the new platform, the block time is shorter than with the old one, but also that this time block is less relevant for the final performance. Also, recent studies have confirmed that the new starting platform allows a greater horizontal force to be generated (Honda et al., 2010).

          4. What were the main findings in your study?
          From our point of view, the four main findings of our study were: (i) the men had shorter block times than the women in both events (50-m and 100-m freestyle) and with both platforms (new and old); (ii) for both distances, the swimmers had shorter block times in their starts from the new starting platform with back plate than with the old platform; (iii) for the 50-m event with the old starting platform, the medalists had shorter block times than the semifinalists; and (iv) the new starting platform block time was only determinant in the women's 50-m event.

          5. Why do you think you had the differences between sexes?
          There could have been two reasons. On the one hand, women's reaction time to auditory stimuli has a greater variability than that of men (Deary and Der, 2005), and, on the other, there is the importance of lower limb muscle power at the start. For the first of these, a recent study has shown men to have a shorter auditory stimulus reaction time when large muscle groups are involved (Spierer et al., 2010). Nevertheless, our work apparently contradicts the results of other studies, but perhaps this is due to the methods used since they each only considered a single championship – 1982 Commonwealth Games, 1996 Olympic Games, and 2000 Olympic Games.

          6. Do you think changes in starting style over the years could confound the results?
          This is the main limitation of the study. No analysis was made of the set-up

          of the position and inclination of the new starting platforms used by each of the swimmers. This could have influenced both the block time and the start phase in general (take-off angle, horizontal take-off velocity, vertical take-off velocity, flight distance, inter alia) (Slawson et al., 2011; 2012; 2013; Takeda et al., 2012). However, analysis of the trend in the last thirteen years (2000-2012) and of the 1657 records allowed us to draw conclusions that should be relevant for applications to training.

          7. Do you think the new blocks will make the two-footed grab start extinct?
          In international competitions, it seems that this will be the trend. However, the two-footed grab will continue to be used in categories of formation of young swimmers or of lower performance since it is easier to execute properly.

          8. How do you think swimmers can improve their start with the new blocks?
          As I said, while the study found block times to indeed be shorter with the new platform, it also found that this had no direct positive influence on the final performance. Indeed, it may even have a contrary effect. Instead, it appears that the important thing is for the swimmer to aim at getting the centre of gravity forward as fast as possible while the feet are in contact with the starting platform so as to most effectively generate force against the platform.

          9. With the new backstroke starting platforms approved this year, what sort of changes should be expected?
          This platform allows the swimmer to take a more upright initial stance, which will allow greater possibilities for the flight phase. But it is still too early to guess what changes to expect. In this regard, there are some very interesting studies being done at the University of Porto in Portugal (Professors JP Vilas-Boas and R. Fernandes and their co-workers) on the initial position of the feet.

          10. What research or projects are you currently working on or should we look from you in the future?
          Among other projects, other colleagues (University of Extremadura, Spain: Y. Escalante, A. Dominguez; Autonomous University of Chile, Chile: A. García-Hermoso; University of Granada, Spain: R. Arellano; and University of Castilla-La Mancha, Spain: F. Navarro) and me will be continuing to work on swimming performance analysis based on studying generic data of international championships, since a temporal analysis of any trends should allow us to draw conclusions that will be both reliable and of relevant application to the field of performance.

          1. de Jesus K, de Jesus K, Figueiredo P, Gonçalves P, Pereira SM, Vilas-Boas JP, Fernandes RJ (2013). Journal of Sports Sciences, 31:1665-1675
          2. Deary, I.J. and Der, G. (2005). Aging Neuroscience and Cognition, 12:187-215.
          3. Honda KE, Sinclair PJ, Mason BR, Pease DL (2010). In: Biomechanics and Medicine in Swimming XI. Eds: Kjendlie P, Stallman RK, Cabri J. Oslo, Norwegian School of Sport Science. 94-96.
          4. Slawson SE, Chakravorti N, Conway PP, Cossor J, West AA. (2012). Procedia Engineering, 34, 801-806.
          5. Slawson SE, Conway PP, Cossor J, Chakravorti N, Le-Sage T, West AA. (2011) Procedia Engineering, 13, 141-147.
          6. Slawson SE, Conway PP, Cossor J, Chakravorti N, West AA. (2013). Journal of Sports Science, 31: 468-478.
          7. Spierer DK, Petersen RA, Duffy K, Corcoran BM, Rawls-Martin T. (2010). The Journal of Strength and Conditioning Research, 24: 957-963.
          8. Takeda T, Takagi H, Tsubakimoto S. (2012). Sports Biomechanics, 11: 370-381.

          When to Start Kicking on a Swimming Start?

          Take Home Point for when to Start Kicking off a Swimming Start

          1. Elite swimmers should initiate their kick between 5.63 - 6.01 m.

          The moment a swimmer loses their speed after a start is a critical moment to begin stroking, as it is likely velocity will only decrease at this moment. This is vitally important for sprint swimming, as the 50 and 100-m races are strongly linked to starting performance. When should a swimmer start to kick off the start?

          Eight swimmers (~24.41 mean 50 m freestyle) on the French national team performed three grab starts as efficiently as possible. The swimmers were filmed using a 4 mini-DV cameras during the entire underwater phase.

          Nine anatomical landmarks were identified on the swimmer’s body. To minimize the error during the digitizing process, both sides of the swimmers were assumed to be symmetric.

          When to Start Kicking

          The swimmers reached a velocity between 2.2 and 1.9 m/s after their center of mass covered between 6.02 – 6.51 m. The main change in speed occurred between 5.63 - 6.01 m. 


          Elite swimmers must find the ideal time to initiate their underwater kick to maintain horizontal velocity. Elite swimmers should start their kick between 5.63 - 6.01 m. This should be a guide as individualized starting plans are necessary for elite success.


          1. Elipot M, Hellard P, Taïar R, Boissière E, Rey JL, Lecat S, Houel N. Analysis of swimmers' velocity during the underwater gliding motion following grab start. J Biomech. 2009 Jun 19;42(9):1367-70. doi: 10.1016/j.jbiomech.2009.03.032. Epub 2009 Apr 24.

          G. John Mullen received his Doctorate in Physical at University of Southern California (USC) and is a certified strength and conditioning specialist (CSCS). At USC, he was a clinical research assistant performing research on adolescent diabetes, lung adaptations to swimming, and swimming biomechanics. G. John has been featured in Swimming World Magazine, Swimmer Magazine, and the International Society of Swim Coaches Journal. He is currently the owner of COR, providing Physical Therapy, Personal Training, and Swim Lessons to swimmers and athletes of all skills and ages. He is also the creator of the Swimmer's Shoulder SystemSwimming ScienceSwimming Science Research ReviewMobility System and the Swimming Troubleshooting System.

          Resistance Training and Dive Start Performance

          Take Home Points on Resistance Training and Dive Start Performance

          1. Resistance training and plyometric programs lack specific neuromuscular properties are unlikely to directly improve dive starts.
          2. Regular dive start practice has been found to improve the start performances of elite athletes.
            In competitive swimming, it is impossible to deny the importance of the start. Mujika and colleagues reported that the difference between the gold medal and fourth place in swimming at the Sydney Olympics was only 1.62% and the difference between third and eighth was only 2.02% (Mujika et al, 2002). Therefore, increasing our chances of success by only 1-2% can dramatically change the outcome of a season or even a career. With starts taking up significant portions of the race in sprint events, improving athlete’s starting ability is likely to increase that athlete’s chances for success.

            It is typical to see complex resistance training and plyometric programs incorporated into swim training in order to maximize the results in the pool. These programs are typically measured by testing vertical jump, broad jump or some type of isokinetic exercise. The assumption is often made that an increase in these exercises is positively correlated with an increase of dive start ability. In 2003 Breed and Young performed a study looking at the effectiveness of a resistance training program on the grab, track and swing starts in swimming. Six dry-land tests were performed: two countermovement jumps, two isokenetic squats, and two overhead throws. After 8 weeks of resistance training it was found that resistance training significantly improved performance on the dry-land tests. However, no significant improvements due to training were found for any temporal, kinematic or kinetic variables with the grab or swing start. This study concluded that 

            “Non-significant trends towards improvement were observed within all starts for the vertical force components, suggesting the need to practice the dives to retrain the changed neuromuscular properties” (Breed et al., 2003).

            Regular dive start practice has been found to improve the start performances of elite swimmers (Blanksby, 2007). This same study concluded that “Coaches only need to slightly alter the training programme to incorporate three dive practice sessions per week of approximately 15 minutes each to significantly improve the starting performances of their swimmers” (Blanksby, 2007). 

            These findings suggest that regular specific dive start practice and coaching does benefit the athlete. It seems that resistance training and/or plyometrics lack the specificity needed for directly improving dive start performance. If these statements are valid, it would appear that resistance training and plyometrics are inferior forms of training than simply practicing dive starts when attempting to directly improve dive starts. It is likely that specific dive start practice will increase jumping ability in ways specific to that needed when executing a dive start in a race. It is also known that angle of entry, streamline, along with several other skills are required to improve racing times. The transitions between all previously listed skills are important for increasing overall swimming success and it is unlikely to improve those transitions without practicing those skills directly. With resistance training and plyometric programs appearing as an inferior form of training when attempting to improve dive starts it is the opinion of this writer that inferior forms of training have no place in program design if the superior form of training is possible.


            It seems very simple but the most effective way of improving dive starts is by simply practicing dive starts. Although there is mixed evidence supporting the use of resistance training and/or plyometric programs to improve dive starts the principle of specificity reveals itself again and exposes how truly specific training should be. With regular dive start practice revealing itself as the superior form of training coaches should consider including regular dive start practice sessions of approximately 15 minutes to improve dive start performances.

            If you liked this piece, consider purchasing the January Edition of the Swimming Science Research Review on Swimming Starts.



            1. Mujika, I., S. Padilla, and D. Pyne. Swimming Performance changes during the final 3 weeks of training to the Sydney 2000 Olympic Games. Int J Sports Med 23:582-587, 2002.
            2. Breed, Ray VP, and Warren B. Young. "The effect of a resistance training programme on the grab, track and swing starts in swimming." Journal of sports sciences 21.3 (2003): 213-220.
            3. Blanksby, Brian, Lee Nicholson, and Bruce Elliott. "Swimming: Biomechanical analysis of the grab, track and handle swimming starts: an intervention study." Sports Biomechanics 1.1 (2002): 11-24.
            Written by Herbert Behm, a long time swimmer and coach, currently Assistant Coaching the Senior and Age Group programs at Phoenix Swim Club in Phoenix, Arizona. He is completing his Bachelor of Arts degree in Psychology and Communications at Arizona State University where he is a school record holder in the 400 Medley Relay.

            Friday Interview Ricardo Jorge Pinto Fernandes, PhD Discusses Backstroke Starts

            1. Please introduce yourself to the readers (how you started in the profession, education, credentials, experience, etc.).
            My name is Ricardo J. Fernandes and my education is:
            • Habilitation in Sport Sciences (2013).
            • PhD in Sport Sciences (2006).
            Current scientific and/or professional activities:
            • Head of the Swimming Department of the Faculty of Sport of the University of Porto.
            • Auxiliary Professor with Habilitation.
            • Member of the Centre of Research, Education, Innovation and Intervention in Sport: http://www.fade.up.pt/cifi2d
            • Member of the Porto Biomechanics Laboratory (LABIOMEP), University of Porto, Porto, Portugal www.labiomep.up.pt
            • Editor-in-Chief of The Open Sports Sciences Journal http://www.benthamscience.com/open/tossj/
            Area of scientific activity:

            Sport Sciences. Biophysical characterization specially centred on the availability and use of energy in aquatic activities (e.g. swimming, rowing and surfing): (i) determination of the athlete’s bioenergetical profile by understanding the kinetics of oxygen consumption and lactate production, which allow assessing the energy cost of the movement and, therefore, the definition of exercise economy profiles for athletes of different levels and gender and (ii) relationship of these physiological parameters with biomechanical and coordinative variables, particularly with the stroke parameters (stroke frequency, stroke distance and stroke index), the index of coordination, the intracyclic velocity fluctuations and the electrical muscular activity. Planning and periodization, and training control and evaluation of athletes in cyclic and team sports (e.g. swimming, running, cycling, rowing, kayaking and water polo).

            Other skills/activities:

            Author and co-authorship of 1 book, 16 book chapters, 211 papers in scientific journals with peer-review (from which 56 manuscripts indexed on SCOPUS/ISI Web of Knowledge), 20 papers in journals without peer-review and 271 full papers/abstracts in congresses proceedings. H index of 11.

            Over than 100 invited manuscripts’ reviews.
            • Participation in several professional and scientific meeting with over 115 podium and poster presentations.
            • Supervision of 9 doctoral students, 15 master students, 5 license students, some post-doctoral students and 2 grant holders.
            • Integration in juries of different level academic theses, particularly of 11 doctoral (8 as opponent), 25 master (5 as opponent) and 87 license (25 as opponent) academic dissertations.
            • Awarded as the best podium presentations in swimming related meetings.
            • Swimming coach 1994-2008, in the Portuguese Age-Group National Team, the University of Porto Team and Club Teams.
            • Member of the Scientific Committee of the International Lifesaving Congress (La Coruña’ 2007), of the XIth International Symposium on Biomechanics and Medicine in Swimming (Oslo’2010) and XXIX Annual International Symposium of the International Society of Biomechanics in Sports (Porto’ 2011).
            • Member of the Organizing Committee of the XXIX Annual International Symposium of the International Society of Biomechanics in Sports (Porto’ 2011), 4th International Conference Swimming Pool & Spa (Porto’2011), Xth International Symposium on Biomechanics and Medicine in Swimming (Porto’2006) and Portuguese Swimming Coaches Association Congress (Porto’1998).
            • Director of Courses of Swimming Coaches Education (level 1 and 2 of the Portuguese Swimming Federation).

            2. Your team has been the main drivers of research on backstroke starts [see their latest full article here]. Could you please explain your group's interest in the backstroke start?
            Studies regarding starting techniques evaluation focused on the different ventral starts. Our group acknowledge the backstroke start as important as ventral starts, since small temporal differences in short and middle distance backstroke events might also be explained by starting efficiency. In the latte Barcelona 2013 Swimming World Championships the second-placed at men’s 100 m backstroke at was 0.20 s slower than the winner at the 15 m mark (after the start) and the final race time differed on 0.19 s; this demands higher attention from the swimming technical-scientific community. In fact, most studies dealing with backstroke starting technique were conducted based on FINA or NCAA old rules, and only our group has considered the effects of the new FINA actual rules, particularly on its combined effects with the recent starting block configuration, since several starting variants have been performed by backstroke swimmers.

            3. What has your group found between feet in the water and out of water starts?
            Firstly, we have analyzed some relevant biomechanical variables that could explain the reduction of the backstroke starting time when performing with feet parallel and completely submerged or emerged. Our main findings indicated that in both starting variants, swimmers should increase the horizontal velocity at the gliding phase: for the variant with feet positioned parallel to each other and completely submerged, swimmers are advised to increase their respective lower limbs horizontal impulse at pushing the wall, and, for the variant with feet parallel and completely emerged, swimmers are advised to avoid a great horizontal pool wall approximation during “set position” that might imply a flatter take-off angle.

            Then, we aimed to compare the two above mentioned backstroke starting variants using a
            more detailed biomechanical approach. We found that both variants had similar 5 m starting time, recommending that, irrespective of the swimmer’s feet positioning, coaches should emphasize the mechanical advantages of each variant during the wall contact phases. Moreover, we have suggested that the maintenance of those advantages throughout the flight should be stressed, aiming to better backstroke start performance.

            Meanwhile, we are studying the underwater phases in the backstroke start, namely the gliding and undulatory underwater kicking cycle. We did not observe any statistically relevant difference between the starting variants with feet parallel and submerged and emerged. On the Biomechanics and Medicine in Swimming Symposium (to be held in Canberra April’ 2014, http://www.bms2014.com.au/index.asp?IntCatId=14), we will show our recent findings regarding the underwater phase of one of the most used backstroke starting variant, particularly that backstroke swimmers do not perform a gliding phase after the body is in full immersion (which was a surprise to us).

            4. How much does comfort level or starting preference style play a role?
            Beside our main research findings, we have recommended that swimmers should experiment different starting variants before the selection of a specific one. For instance, swimmers with higher height and mass might find more difficult to position their feet completely above the water surface, even though some proficient swimmers are using it. Furthermore, the actual FINA rules and the recent starting block configuration allow swimmers to assume several combinations of feet and hands positioning, evidencing that swimmers should experiment in their training sessions which starting variants fits the best.

            5. Do you think dry-land exercises (resistance training or plyometrics) could benefit elite backstroke swimmer's starts?
            Previous studies about this topic have only focused on the swimmers’ lower limbs (e.g. Kilduff et al., 2011; Potdevin et al., 2011). We knowledge that the high-velocity muscle actions characteristics of the backstroke start could benefit from specific resistance training, essentially the core muscles and the upper and lower limbs muscles, since we have analyzed the electromyographic activity of these muscles. In a near future, we will have data to share on this topic.

            6. How much do you think the new Omega foot placements will help backstroke swimmers?
            The metal plate with a non-slip coating for foot placement might really help backstroke swimmers, particularly by the increase of the friction force, allowing a better grip. However, swimmers along the years have developed strategies to avoid slipping when performing backstroke start, independently of the existence of the metal plate. Therefore, more research is welcome to assess the advantages of this new device on backstroke start performance.

            7. When do you think we'll see another sub-:52 100-m back for men? When do you think a woman will enter the: 57 zone?
            We are certain that those performances will appear in a short time particularly if during the training process the start performance can dispose of a little bit more of attention. In fact, the actual best female backstroke swimmers have around 7.5 s at the 15 m mark and 58.3 s on the 100 m backstroke race, and, as the best women’s 15 m starting time is under the 7.0 s (recently recorded at the 50 m event), it is evident that some amazing performances will come soon.

            8. What are the common mistakes in backstroke starts?
            Considering the most recently used backstroke starting variants (from the 2012 Olympic Games and 2013 Swimming World Championships), we have been surprised with the number of elite swimmers (from both genders) that perform a flat flight phase, leading to a high-resistance water entry. Thus, the combination of FINA rules with the new starting block configuration should be better explored so swimmers can take as much advantage as possible.

            9. Do you think there will be any big progressions to the backstroke starting style?
            We have noticed that elite swimmers use, at least, seven backstroke starting variants (combining different hands and feet positioning). Therefore, we think that with the application of new biomechanical tolls (e.g. automatic motion capture systems and underwater force plats), one or two main starting techniques will be selected in short time.

            10. What makes your research different from others?
            In general our research follows two main aims: (i) to conduct an integrated analysis of the phenomenon, particularly by carrying out a biophysical approach of swimming performance and training (here we suggest the readying of Figueiredo et al., 2013 for a better understanding of this physiological and biomechanical combined assessment) and (ii) to approach relevant topics to be used by coaches and swimmers in their daily work at the poll and gym (it is why we try to use a writing style as coach friendly as possible, and to participate in swimming science related events). In addition, we aim to implement innovative and appropriated biomechanical measurements and research methodologies to explain simple research questions that coaches and swimmers can use to better refine their training programs.

            11. Which teachers have most influenced your research?
            The contributions from Profs. J. Counsilman, E. Maglischo and D. Chollet, as well as from expert swimming coaches like B. Sweetenham, have been often considered regarding the backstroke start. Interesting descriptions of this specific starting technique exists since the 1960s, mainly included in books. Off course, as a researcher I have been influenced by several other personalities, but my academic mentor (Prof. J. P. Vilas-Boas) has been decisive in all my scientific path and in the sustained growth that our group has been presenting.

            12. What research or projects are you currently working on or should we look from you in the future?
            Our research group has recently submitted a literature review concerning the kinematics of the backstroke start, highlighting the gaps and limitations and defining topics for future research. We have written a manuscript describing the most used backstroke starting variants in elite level events, considering the FINA rules and the actual starting block configuration. So, next year we hope to publish some new texts regarding the new starting variants and corresponding advantages and disadvantages that are based on a home-made instrumented starting block for 3D upper and lower limbs force analysis, 3D kinematics (from the starting signal instant until the 15 m mark) and electromyographic profile. Other topics of swimming research are also assumed as focus of interest of our research group, both considering biomechanical, physiological, EMG and thermographyc approaches.

            1. de Jesus, K., de Jesus, K., Figueiredo, P., Gonçalves, P., Pereira, S., Vilas-Boas, J.P., Fernandes, R.J. (2011). Biomechanical analysis of backstroke swimming start. International Journal of Sports Medicine, 32, 546-551.
            2. Figueiredo, P., Pendergast, D.R., Vilas-Boas, J.P., Fernandes, R.J. (2013). Interplay of biomechanical, energetic, coordinative, and muscular factors in a 200 m front crawl swim. Biomed Research International, art. nº 897232. doi: 10.1155/2013/897232.
            3. Hohmann, A., Fehr, U., Kirsten, R., Krueger, T. (2008). Biomechanical analysis of the backstroke start technique in swimming. E-J Bew Train, 2008; 2: 28-33.
            4. Kilduff, L.P., Cunningham, D. J., Owen, N.J., West, D.J., Bracken, R.M. Cook, C.J. (2011). Effect of postactivation potentiation on swimming starts in international sprint swimmers. Journal of Strength and Conditioning, 25, 2418-2423.
            5. Martuscello, J.M, Nuzzo, J.L:, Ashley, C.D., Campbell, B.I, Orriola, J.J., Mayer, J.M. (2013). Systematic review of core muscle activity during physical fitness exercises. Journal of Strength and Conditioning, doi: 10.1519/JSC.0b013e318291b8da.
            6. Potdevin, F.J., Alberty, M.E., Chevutschi, A., Pelayo, P., Sidney, M.C. (2011). Effects of a 6-week plyometric training program on performances in pubescent swimmers. Journal of Strength and Conditioning, 25, 80-86.