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RER Value Guide

Slow (0.7)
A1 band - warm-up, recovery, cool-down sets
Moderate (0.85)
A2 band - aerobic capacity sets
Intense (1.00)
A3 band - aerobic power, VO2max sets

Data Source: Zamparo P, Bonifazi M (2013). Bioenergetics of cycling sports activities in water.

Coded for Swimming Science by Cameron Yick

Freestyle data

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Does Greater Force Production Equal Faster Swimming?

Measuring force in the water is difficult, let alone the contribution of force in swimming success.
Before we can address if force production equals faster swimming, we must review how force is calculated in swimming research. Must of this piece is taken from Sacilotto (2014), if you are interested in reading more.

Unfortunately, only a limited number of reviews identify resisted, or drag forces, in swimming.

The drag force is the force component parallel to and in the same direction as the relative fluid force. Drag force D is calculated by: Df = 1/2CDrv2A, Cd is the drag coefficient, and r is the density of fluid, v is the velocity of the object and a is the frontal surface area of the object. 

The resistive forces the swimmer interacts with in the water are form, wave, and frictional drag. These are influenced by the swimmer's velocity, boundary layer, shape, size, and the frontal surface area. In swimming, the resistive forces are termed the active and passive drag. 

  • Active drag is the water resistance associated with the dynamic swimming motion.
  • Passive drag is the water resistance that a human body experiences in a fixed or unchanging posture.
Komogorov (1992) determined active drag varies between individuals and seems to related to swim technique and anthropometry. For swimming, drag can be active or passive. However, we will only discuss active drag.

Active Drag and Swim Performance

The two most commonly identified factors for swimming speed are propulsion and drag. The ability to reduce the active drag encountered allows propulsive forces to be efficiently applied, increasing swimming velocities. Elite swimmers are more able to reduce active drag than nonelite swimmers (Kolmogorov 1992). This efficiency allows elite swimmers to minimize wasted kinetic energy. 

However, Hollander (1985) did not find a significant correlation in active drag and swim velocity at a constant velocity. 

Mechanical Power Output in Swimming

Some suggest swimming performance is defined by the relationship between the useful mechanical power output, active drag, the hydrodynamic force coefficient (drag coefficient) and the maximal free swim velocity. The mechanical power is the power delivered to overcome drag. Swimming power is evaluated as the product of swimming drag (D) and velocity (v):
P= Dv
The ratio between the useful power and the wasted kinetic energy is defined as the propelling efficiency of a swimmer: 
hP = Pd/PO

hP is the propelling efficiency and Pd is the useful power.

Techniques of Drag Assessment

Measurements of active and passive drag have been attempted through the years. However, there is much controversy on the techniques. The energetics approach, numerical solutions and experimental techniques have been developed and use to estimate or measure drag forces in swimming.

Energetics Approach

The energetics approach is also coined theoretical calculations, investigates the relationship between
energy costs of swimming, the velocity, and the overall mechanical efficiency of the swimmer and the body drag. This is used for deciphering the mechanical power output of a swimmer during free swimming. This approach tows a swimmer at a given pace, which is maintained by a towing carriage with known additional weights to provide assistance/resistance. The maximal oxygen consumption is then recorded. The body drag is determined by adding (or subtracting) extra loads to (or from) swimmers moving at a known speed. The extra drag was measured and related to the swimmer's energy expenditure to calculate the drag and swimmer's mechanical efficiency. 

Di Prampero (1974) identified a linear relationship between drag and maximal oxygen consumption at constant swim velocities, which led to this technique of determining drag as a function of VO2net. Clarys stated “extrapolated the linear regression between VO2net and the added propulsion and added drag to VO2net = 0.” At a constant mean velocity, the mean propulsive force exerted by the swimmer will be equal and opposite to the active drag produced.

Similar values of active drag were found when comparing propelling efficiency values as a percentage. In this studies the drag values were similar, but the authors assumed propelling efficiency did not change where active drag was calculated. It is likely propelling efficiency will change, even at a constant speed, when external loads are applied, as is this case in this approach. Also, small changes in VO2net values due to small deviations in propelling efficiency will be amplified by the extrapolations that are a basis for these studies. Van de Vaart believes this form of testing overestimates active drag. Also, a snorkel is used to measure VO2net, altering the frontal surface area which likely modifies the active drag.

Numerical Simulations

These models use the computational modeling of the water flow surround the swimming to determine
the resistive forces. This is typically through computational fluid dynamics (CFD). CFD solves the analyses problems using fluid flow by means of computer-based simulations. It creates a 3D model of a swimmer and simulates their movement patterns. CFD simulations eliminates within-subject variability, allowing the same input you always have the same output. Bixler (2007) studied the water flow and drag force characteristics on a human, a CFD, and a mannequin. Although the study only assessed passive drag, the results were positive, as the submerged human body had similar passive drag. For CFD to become a readily available method of resisted force assessment, basic kinematic measures during free swimming need to be collected, like the ability to collect instantaneous swim velocity, or knowing where the center of gravity is while a swimmer is swimming. A further limitation is that CFD simulations require a lot of computer time and knowledge of the process, making it difficult for coaches and scientist.

Experimental Techniques

Experimental techniques attempt to accurately determine the resistive forces encountered by a swimmer. This often uses the measuring active drag system (MAD-system), and the indirect techniques of collecting active drag values, the pertubation method (VPM), and the assisted towing method (ATM).

Measuring active drag system 

Hallander (1986) developed this system which measures the drag force generated by a swimmer, which enables the calculation of the propulsive force production during the trial. The assumption is made that the mean propulsive force would be equal to the mean active drag values when the swim velocity is constant.

The MAD-system, requires the swimmer to push off from fixed pads underneath the water. Originally this technique different but constant velocities. The swimmer's legs were restricted by a small buoy. The depths of the pads were able to be adjusted for the swimmer’s height as well as the distance between pads. For each trial, the registered output signal of the force transducer was transmitted telemetrically to determine mean force. The average propulsive force was calculated by integration from the force registrations at a constant swim velocity. The swim velocity was determined from the sample frequency and the pad distance (between the second and final pad).

Toussaint (2011) represents the calculation for drag as Da=Kv2, where Da represents total active drag, K is the constant (incorporating the density, coefficient of drag, and frontal surface area), and v equals swimming speed. 

Although this technique has been used extensively, it has much criticism. For one, it limits the swimmer's natural stroke mechanics, and it can only be used at a constant velocity. Also, this technique should only be compared against itself or if a swim velocity is the same between techniques. It also uses pads and doesn't allow the swimmer to be in contact with the water. This may alter the normal hand trajectories. Having the pads requires more coordination to constant the pads and may slow down effort. Also, the use of a pull buoy alters swimming biomechanics.

Velocity Perturbation Method 

The VPM method is based on the assumption that a swimmer is capable of producing an equal amount of useful mechanical power output and that the simmer will swim at a constant velocity. This technique is seen as a progression from the energetics approach in estimating active drag, without the use of maximal oxygen consumption. In the VPM, a swimmer must produce two equal maximal efforts. This is typically used over 25 m, but has been used in other distances. The first swim is freely, without any attachments, and the second is swum with a hydrodynamic body attached to the swimmer, creating extra resistance. The maximal mean velocity when swimming with the hydrodynamic body was compared with the maximal mean free swimming velocity, which along with the a known addition resistance is used to calculate active free drag for free swimming:
Db is the additional resistance from the pertubation buoy and vb and v are the swimming velocities with and without the hydrodynamic body. 

This method is frequently criticized, as it is an indirect measurement of active drag, and may overestimate active drag. It is also assumed participants use the same velocity level. This is difficult due to the added device and it is found that the maximal error due to stroke cycle fluctuations is around 6 - 8%. The other error is that it is difficult for non-elite swimmers to swim with this added device. 

To allow different skill levels, different hydrodynamic bodies were developed. However, no matter the size, a hydrodynamic body will still alter swimming skill. Xin-Feng (2007) created an apparatus which stayed in a steady position and minimizes the floating movement of the hydrodynamic body. During Xin-Feng's study they measured the variation in tension of the tread when the gliding block was moved by the swimmer. The results revealed that the tension of the thread fluctuates, revealing the additional resistance does not have a constant value as assumed. 

Despite the limitations of the VPM, there are benefits. For one, the VPM method is easily set-up at a pool, allowing coaches and athletes use. It also doesn't need adaptations for different strokes.

Assisted Towing Method

The assisted towing method (ATM) technique is essentially the reverse of the VPM method, by assisting, instead of resisting the swimmer. The ATM is also based on the equal power assumption and the constant velocity assumptions. However, as outlined by Xin-Feng (2007), a swimmer will not be swimming at a constant velocity at any point throughout a maximal effort due to the intrastroke fluctuations in the swimming. Such fluctuations are a result of the intrastroke forces that are generated during a natural arm cycle. kicking also leads to fluctuations. 

Mason (2011) compared constant active drag values with fluctuating active drag values. During these trials, the mean velocity maximal free swims (individual swimming without any attachments) and the mean velocity of the towed swims (towed from the hip using the dynamometer) are used to calculate for drag with respect to the drag force required to tow the swimmer. This helped create the VPM equation:
Da=Fbv2v1^2/v2^3 - v1^3
Fb is the force required to tow the athlete at the increased speed as measured from the force platform, v2 is the increased tow velocity, and v1 is the maximal free swimming velocity. Similar to the VPM approach, when using this system with a constant velocity, the dynamometer is set to 5% faster than the swimmer's mean maximum free swim velocity with a high force selection to allow for a near constant tow. To allow the swimmer's intrastroke fluctuations, the force setting on the dynamoeter is reduced and the velocity setting is increased to 120% of the swimmer's maximum free swim velocity. Along with these changes in set force and velocity settings, a paramter on the towing dynamometer is
altered so that when the force setting is reached it will fluctuate the tow velocity to maintain that force setting, therefore allowing the intrastroke fluctuations. The force setting used is a predetermined fraction of the swimmer’s passive drag tow (streamlined tow at the swimmer’s maximal free swim velocity) and is different for every individual swimmer. Despite the increase in the velocity, setting the mean tow velocity will still equal between 5% and 10% greater than the swimmer’s maximal mean free swim velocity; however, when calculated, the velocity profile will demonstrate the intrastroke fluctuations. The results from the fluctuating trials seem to demonstrate a smoother drag profile, more repeatable results, more resembling free swimming characteristics. The ATM allowing a fluctuating tow velocity in active drag estimation, is still in its infancy. However, the results shown thus far are positive in being able to decipher exactly what affects performance during free swimming. When towing with a constant velocity it has been assumed that drag was equal but opposite in direction to propulsion. However, when utilizing a tow allowing for instrastroke fluctuations, this can't be true. A recent study using ATM attempted to calculate a swimmer's propulsive profile, net force, and acceleration curves while allowing intrastroke velocity fluctuations:
P=d/dt (mv)-DA
P is propulsion, m is the passive drag force of the swimmers (as a substitute for the mass of a swimmer), v is the velocity profile, and Da is the active drag. 

Although ATM is promising, validation is needed. Although a small sample, a recent study revealed very good reliability value for within-subject mean active drag values (interclass correlation of 0.91, at a confidence limit of 95% and a likely range of 0.58 and 0.98). Future studies must investigate into whether the velocity/force profiles obtained during this technique mimic real stroke mechanics. However, until accurate measurements of basic kinematics while a swimmer is submerged in water, research with the method is under scrutiny. Also, the use of this system for other strokes is not well established due to the intracyclic variations between strokes.

So Does Great Force Production Equal Faster Swimming?

The simple answer is no. Elite male sprinters have a peak force of 50 – 80 pounds and on average 20
– 31 pounds of resultant force (Havrulik 2013). Compare this to the ~800 pounds of force created by Olympic track sprinters. Another way to look at it, if simply increasing force resulted in faster swimming, then the strokes with the highest force production (fly and breast), would be the fastest (Morouço 2011). 

Instead, it seems variation in force production plays a larger role in swimming speed. This isn't to say, if you improve your swimming force production, then you won't be a better swimmer, as you may improve your force production as you decrease your variation in force production. 

Also, we must consider the timing and displacement of force. Sometimes, a swimmer will create force, but in a wasted manner, ie when their hand is not facing perpendicular to their body or as their arm is out of the water. This is a wasted increase in force production.

Overall, a careless increase in force production doesn't necessarily increase swimming velocity. However, increasing force production in a vacuum will increase swimming velocity.

Now the question is how can you improve this force production with altering the rest of their biomechanics...

  1. Mason B, Sacilotto G, Menzies T. Estimation of active drag using an assisted tow of higher than max swim velocity that allows fluctuating velocity and varying tow force. Paper presented at: 29th International Society of Biomechanics in Sports; July, 2011; Porto, Portugal.
  2. Bixler B, Pease D, Fairhurst F. The accuracy of computational fluid dynamics analysis of the passive drag of a male swimmer. Sports Biomech. 2007 Jan;6(1):81-98.
  3. Xin-Feng W, Lian-Ze W, We-Xing Y, De-Jian J, Xiong S. A new device for estimating active drag in swimming at maximal velocity. J Sports Sci. 2007;25(4):375–379.
  4. Toussaint HM, Roos PE, Kolmogorov S. The determination of drag in front crawl swimming. J Biomech. 2004;37(11):1655–1663.
  5. Sacilotto GB, Ball N, Mason BR. A biomechanical review of the techniques used to estimate or measure resistive forces inswimming. J Appl Biomech. 2014 Feb;30(1):119-27. doi: 10.1123/jab.2013-0046.
  6. Hollander AP, De Groot G, Van Ingen Schenau GJ, et al. Measurement of active drag during front crawl arm stroke swimming. J Sports Sci. 1986;4:21–30.
  7. Di Prampero PE, Pendergast DR, Wilson DW, Rennie DW. Energetics of swimming in man. J Appl Physiol. 1974;37(1):1.
  8. Kolmogorov SV, Duplishcheva OA. Active drag, useful mechanical power output and hydrodynamic force coefficient in different swimming strokes at maximal velocity. J Biomech. 1992;25(3):311–318.
  9. Toussaint HM, Beelen A, Rodenburg A, Sargeant AJ, de Groot G, Hollander AP, van Ingen Schenau GJ. Propelling efficiency of front-crawl swimming. J Appl Physiol (1985). 1988 Dec;65(6):2506-12.
  10. Havruilk, R. Personal Communications. San Jose CA. September 2013.
  11. Morouço P, Keskinen KL, Vilas-Boas JP, Fernandes RJ. Relationship between tethered forces and the four swimming techniques performance. J Appl Biomech. 2011 May;27(2):161-9.

Dolphin Kicking

Take Home Points:
  1. Elite swimmers may not use a symmetrical dolphin kicking strategy.
The undulatory underwater sequence, dolphin kick, is one of the most important but unexplored phases in competitive swimming. Swimmers use this kick for butterfly and starts/ turns in freestyle and backstroke.

Unfortunately, we still have a lot of questions regarding the effectiveness of underwater kicking, as well the ideal kicking biomechanics.

In the past, I've written a lot about dolphin kicking. In these posts, I've discussed ideal depth, as Marinho (2009) looked at drag coefficients at different depths.

I've also discussed ideal kicking tempo, referencing great work by Coach Bob Gillett and Russell Mark, as well as Cohen (2012). Coach Gillett has analyzed elite male and female swimmers and suggests both groups should have a kicking tempo around 0.45 (Gillett 2013), where Russell Mark (2012) notes a tempo around 0.40 is utilized. Many feel this kicking tempo is extremely fast, but one study by Cohen (2012) indicates faster kicking tempo is correlated with net higher streamline force.

Russell Mark has even analyzed the amount of kicks by elite swimmers, noting the following kick number and time.

I've  also discussed the importance of dolphin kicking with Scott Colby, in his "pseduo-study" or elite youth swimmers, finding the 5-meter streamline, the range (depending on age) of the top times was 2.3-3.1 for boys and 2.7-2.8 for girls. For 15-Meter Dolphin Kick the ranges were 6.1-6.9 for boys and 7.1-7.3 for girls.

In another case, I've broken down a case study of dolphin kicks:

"Case Study #1

You have a 5"2" 16-year old female swimmer who goes :58 100 back and is known for her good underwaters. Her results from the aforementioned test were:
  • 0-5 m: 2.8 seconds
  • 0 - 15 m: 8.0 seconds
  • Kick Count: 16 kicks
  • Kick Tempo: 0.35
Intervention: This is a clear case of a swimmer who performs too many kicks to 15-m. For her, changing her tempo isn't needed, as high tempos are correlated with kicking speed, but instead decreasing her kick total by encouraging her to follow through her kick was advised. "Short kicking" and not following through prevents a full activation of her quadriceps and impairing forward propulsion. She was challenged to progressively decrease her kick total from 16 - 12 kicks over the course of several weeks, not progressing until she mastered her new kick count at the same or faster pace which would be tested at frequent underwater kicking tests.

Case Study #2

A 6'1" 15-year old male swimmer who goes a :49 in the 100 back. His results were:
  • 0-5 m: 2.7 seconds
  • 0-15 m: 8.2 seconds
  • Kick Count: 12
  • Kick Tempo: 0.75
Intervention: It is clear he has too slow of a tempo. However, simply giving him a 0.4 tempo will discourage and potentially impede progress. Instead, gradual increases in tempo is necessary during progression, increasing 0.05 after mastery during kicking trials.

Swimming Science has also had the opportunity to talk with some of the great minds in research of dolphin kicking Ryan Atkinson and Marc Epilot.

Dr. Epilot breaks down top speed from pushing off the start, 1.9 - 2.2 m/s and when to begin dolphin kicking. He also discusses three errors in dolphin kicking:
"To my point of view, there are 3 main mistakes that swimmers, even top athletes, do. First of all, many swimmers initiate or try to initiate underwater kicking way to soon. As I said a bit before, such mistake has huge consequences on swimmer’s efficiency. Moreover those swimmers don’t even know that they start kicking so early. They are sure to have a long and efficient gliding phase, while they start kicking immediately after water entry.

A second common mistake is to produce to large kicking movements. During a long time, trainers thought that swimmers had to push on the water with their feet, underwater propulsion being the result of that action on the water (Action-reaction Newton law). An increasing number of studies, made on different mechanical simulations, on fish swimming, or on swimmers, have shown that underwater propulsion is mostly explained by a mechanism, named the formation of a reverse Street of Karman Vortices located in the trailing edge of the swimmer. Those vortices create a backward ejection of water that leads to project the swimmer frontward. To create a coherent and propulsive street of Karman vortices, swimmers have to adjust their amplitude/Frequency ratio; usually by decreasing the amplitude and increasing the frequency.

The third mistake I would point out is the undulatory movements of the trunk and arms. In many swimmers, we can observe that their whole body is undulating, which has deleterious effects on the propulsive efficiency. The upper part of the body has to stay streamlined not to absorb the energies produce by the lower limbs. Moreover swimmer’s upper limbs have to be aligned to the orientation of his path. If the swimmer is swimming under the water straight forward, his upper limbs have to stay horizontal. If the swimmers is returning to the water surface with an angle of 30°, his upper limbs have to be at 30° regarding to the horizontal."

Ryan Atkinson mainly discussed symmetry between the downkick and upkick. He said: "Symmetry between downkick and upkick phases is highly related to high UDK velocity, and

swimmers who are more effective at the upkick phase tend to have a faster UDK velocity. Specific movements that are highly related to faster UDK are: greater peak vertical toe velocity during the upkick phase, reduced upkick duration, and less knee flexion at the end of the upkick/start of the downkick."

He also stressed the importance of "reducing the amplitude of the UDK, especially at the upper body segments (torso, head and arms) and increasing kick frequency. Particular attention should be placed on maximizing toe velocity during the upkick and limiting the duration of the upkick. Similarly with beginners, swimmers should be encouraged to recruit the muscles of the posterior chain without excessive lower back flexion or knee flexion. This can be advanced on the land by performing single leg lifts in a plank position, paying close attention to recruiting the gluteal muscles for leg lifts and keeping the hips level."

Ryan Atkinson's work feeds directly into the topic today. The results are somewhat contradictory to Ryan's statements, nonetheless a very important topic and discussion point.

The aim of this research study was to demonstrate the formation and interaction of forces near the swimmer’s body and in the swimmers wake during the dolphin kick in hopes of finding energy-saving mechanics.

What was done

A female swimmer with a 200-m butterfly time of 2:12.0 was selected. Her body was scanned with a 3D laser and subdivided into joints of the arms, torso, upper legs, lower legs, and feet. The swimmer underwater kick from a push was recorded and analyzed


Maximum thrust was generated during the down kick, and was approximately twice the maximum
thrust recorded for the up kick. Both maximum values were reached at the instant when stroke velocity was at its highest within the kick cycle. The results indicate a slight increase in propulsion of 8% over the six cycles. Maximum drag was during an active dolphin kick, 208 N (~46 lbs), and at the same speed drag was ~16 N (~3.6 lbs) during the gliding motion.

Transitioning from the gliding phase to the first kick cycle creates two vortex structures, an upstroke (upper ring) and a downstroke (lower ring). Theses vortexes are shed into the swimmers wake at the end of each cycle. These forces grow in size and strength with each cycle, with cycle 6 demonstrated larger values than cycle 2 of the underwater dolphin kick.


Optimum performance was only reached after a number of kick cycles. The dynamic drag force was ~12x higher during the kick than during the gliding phase. The mean drag and mean propulsion in cycle 6 were about 8% higher than those in cycle 2 of their dolphin kick. During the kicking cycles, the vortex created was recaptured along the body’s surface to a position where the feet would hit the vortex with the next kick

Practical Implications

Additional research is needed, but this case study shows that optimum performance was reached after 6 kick cycles, in which propulsion forces reach a constant value. This 8% increase may be explained by vortex recapturing; which may be increased with fine-tuning of body kinematics off the wall/turn.

Overall, the results are somewhat conflicting towards Ryan, but not really. Although this swimmer demonstrated a much stronger downkick, we don't know if a more symmetrical kick would improve this swimmer's dolphin kicking velocity. Looks like we need more research!


  1. Pacholak S, Hochstein S, Rudert A, Brücker C. Unsteady flow phenomena in human undulatory swimming: a numerical approach. Sports Biomech. 2014 Jun;13(2):176-94. PubMed PMID: 25123002.
  2. Marinho DA, Reis VM, Alves FB, Vilas-Boas JP, Machado L, Silva AJ, Rouboa AI. Hydrodynamic drag during gliding in swimming.J Appl Biomech. 2009 Aug;25(3):253-7.
  3. Cohen RC, Cleary PW, Mason BR. Simulations of dolphin kick swimming using smoothed particle hydrodynamics. Hum Mov Sci. 2012 Jun;31(3):604-19. doi: 10.1016/j.humov.2011.06.008. Epub 2011 Aug 12.
  4. von Loebbecke A, Mittal R, Fish F, Mark R. A comparison of the kinematics of the dolphin kick in humans and cetaceans. Hum Mov Sci. 2009 Feb;28(1):99-112. doi: 10.1016/j.humov.2008.07.005. Epub 2008 Nov 4.
  5. von Loebbecke A, Mittal R, Fish F, Mark R. Propulsive efficiency of the underwater dolphin kick in humans. J Biomech Eng. 2009 May;131(5):054504. doi: 10.1115/1.3116150. 
  6. von Loebbecke A, Mittal R, Mark R, Hahn J. A computational method for analysis of underwater dolphin kick hydrodynamics in human swimming. Sports Biomech. 2009 Mar;8(1):60-77. doi: 10.1080/14763140802629982.
  7. B. Gillett Underwater Kicking and Foil Movement Personal communication. 2013 February 24.
  8. M. Russell Dolphin Kicking. USA Swimming. 2012 April 12.
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.

Cammile Adams Discusses Training and Biomechanics

1) Since your last interview you began training at SwimMac Carolina. What have biggest
transitions with your in-water training?

I'm actually still in school. Im in my last semester right now. So being back in Aggieland has been great! I really missed the girls team this summer so it’s been fun being back!

2) Currently, what are the biggest biomechanical aspects you're working on in your butterfly?

I’ve been working mainly on getting more out of my kicks and keeping that second kick in my stroke throughout the race. David had me doing some different things this summer and I’m still working on those things back here at school.

3) What specific training aspects are you working on for your 200 fly (improving take out
speed, finishing, etc.)?

I’m working on trying to get a little more front half speed. I’m usually really good back half so just trying to lay in on the line a little earlier has been my focus here lately.

4) Has your dryland training changed in the past few years, if so how?

It has quite a bit! Haven’t done a lot outside of the water besides dryland, cardio and weights. This summer I added in some yoga and pilates and really loved both of those. I felt like that really helped my body position in the water and I had a ton of fun doing it!

5) What about your meet preparation behind the block?

Meet preparation behind the blocks kind of changes depending on the meet. Some international meets you’re in the ready room for 20 or so minutes before you actually race. So then I try to just stay relaxed…I usually bring my music with me so that helps. I also like to stretch a bit before and just make sure I’m feeling loose. As far as right before the race starts…I usually splash some water in my face and just take in the atmosphere of the meet.

6) Last time you only took iron supplementation, has this changed at all?

Hasn’t changed at all.

7) What are your goals for 2015 and 2016?

My goals for 2015 and 2016…I’m really excited to have made the Worlds team! So that meet will be my main focus for the summer. Ill be going to SC words here pretty soon in late November so that will be a great time racing short course meters. As far as after that, I just want to continue training in order to put myself in a good place to medal in 2016.

Daniel Marinho Discusses Finger Position in Swimming

1. Please introduce yourself to the readers (how you started in the profession, education, credentials, experience, etc.).

My name is Daniel Marinho, I was a swimmer and a coach for many years. I started my PhD in 2005 regarding the analysis of swimming propulsion using CFD methodology. Since then we have been able to participate in several research projects but also to work in straight cooperation with the swimmers, the clubs, namely with the Portuguese Swimming Federation.

At this moment I am working at University of Beira Interior and at CIDESD Research Center, in Portugal.

2. You recently co-authored a paper regarding finger position during swimming. Has there been much research on this subject?

In the past there has been a great interest under this field, namely with the studies carried-out by Schleihauf. However, recently there has been again an increase interest on the analysis of the best finger position, namely with the use of CFD.

3. What did your study look at?

We analyzed the effect of finger spreading and thumb abduction on the hydrodynamic force generated by the hand and forearm during swimming. We would like to understand what could be the best finger position to increase the propelling force.

4. Did your team consider any other methods for monitoring finger position?

At this moment we were very interested in using CFD to conduct this study, especially to improve our previous studies regarding this field, although we believe the combination of different methods and different studies could be the best solution to improve our knowledge under this field.

5. How did you ensure the swimmers had the same finger position throughout their trial?

It is the advantage of CFD analysis. As we are using computational simulations, one can add some input data into the system and to be sure that this input data will remain the same during the analysis. We used 3D models of the swimmers, obtained with a 3D scanner, so after that procedure one can manipulate and insert the desired data into the system and verify what is the result.

6. What were the practical implications for coaches and swimmers from your study?

I would state that finger and thumb positioning in swimming is determinant for the propulsive force produced during swimming; indeed, this force is dependent on the direction of the flow over the hand and forearm, which changes across the arm’s stroke. Therefore, coaches should be aware that the most appropriate technique must include changes in the relative positions of the fingers and thumbs during the underwater path.

However, when referring to finger spreading, it seems fingers should be grouped or even slightly separated to maximize lift and propulsive drag force production for most sweepback and attack angles.

7. Do you think ideal finger position varies on the swimming stroke?

Yes, we do. The geometry of the hand circumstantially used by a swimmer, especially the position of the thumb, appears to be dependent on and determined by the predominance of the lift and drag forces in each phase of the propulsive action, aiming to best orient the resultant force and thus the effective propulsive force. Thus, thumb abduction and adduction tend to favor propulsive drag or lift under different conditions. It is interesting to notice this situation in high-level swimmers, who changed the position of the fingers, especially the thumb, during the stroke cycle (for instance, Alexander Popov seemed a good example of that).

8. How do you recommend teaching finger position from age-group through Olympic level swimmers?

Coaches should be aware that the most appropriate technique must include changes in the relative positions of the fingers and thumbs during the underwater path and that attention should be paid to the training of swimmers’ specific sensitivity to the hydrodynamic effects of water flow over the propulsive segments.

In age-group swimmers it is very important to allow the swimmer to test different finger position,
different hand position, different “sculling” and propelling drills, to allow improve the “feel of the water”. We believe this is the most important part regarding this issue. Later on, they will be ready and prepared to change the finger position, to be aware of the importance of these small changes during the stroke cycle to improve swimming velocity.

9. Do you think finger position varies much during a stroke cycle or is it static?

Yes, as stated before, we do believe there are important variations during the stroke cycle, allowing the swimmer to improve the capability of producing propelling force, especially regarding to changes in thumb abduction/adduction.

10. Who is doing the most interesting research currently in your field? What are they doing?

There are a lot of good works in swimming research. Fortunately swimming community is very active, as noticed in the last Biomechanics and Medicine in Swimming Conference (Canberra, April 2014). Each year one can observe different research groups with good ideas, using interesting methods to allow a better understanding of swimming performance, thus it is always very difficult to highlight someone or some research group because at this moment it can be appearing an interesting study on a specific field.

Nevertheless, if you allow me I would like to say that I am very proud to be part of the Portuguese Research Team Network who has been doing very interesting works on swimming research.

11. What makes your research different from others?

Basically, one can point out two main things: (i) the use of CFD with realistic models, and the use of different hand/forearm models, and (ii) combining different finger spreading and different thumb positions within the same CFD simulation, which was a step forward in the analysis of swimming propulsion.

12. Which teachers have most influenced your research?

A lot of people have been influencing my work, some of them were my teachers and some cooperated with me in different research projects. All of them played an important role on my education process and I have the pleasure to keep working with them in different projects.

I would refer by a chronological order professor João Paulo Vilas-Boas and Professor Ricardo Fernandes, from the Faculty of Sport in Oporto, who were very important during my undergraduate studies and the ones who integrated me in swimming research projects. Later on Professor António José Silva and Professor Abel Rouboa, from the University of Trás-os-Montes and Alto Douro and CIDESD Research Centre, for allowing me to be part on the CFD project applied to swimming research and supervised my work during the PhD. I would also indicate my colleague at CIDESD Research Centre Professor Tiago Barbosa and my colleague at University of Beira Interior (where I am working nowadays) Professor Mário Marques for the sharing of new ideas regarding swimming research and training methods.

I can not forget my father (Fernando Marinho), a swimming coach and teacher, who helped me think out of the box regarding swimming training, and my swimming coach professor António Vasconcelos (Tonas) who were always up to date regarding swimming training methods and enjoyed to share his knowledge with the others.

13. What research or projects are you currently working on or should we look from you in the future?

We want to continue improving the use of CFD in swimming research, and this should be one of our main focuses in the following years with some PhD students working under this scope and with some projects shared with different Research Centers.

On the other hand, we are very interested in developing and testing new ideas regarding swimming training methods, especially related to strength training and the effects of the use of different warm up routines in swimming performance. We have at this moment at University of Beira Interior and at CIDESD some PhD and Master degree students working under these topics, so we believe in a new future we can present some interesting results.

Interview: Roland Schoeman Discusses Swimming Biomechanics and Training

1) When did you begin swimming and get involved in the sport?

I only started swimming after I had turned 14 (I knew how to swim, because of some lessons when I was a kid), my entire life however had been spent playing a wide variety of other sports, Soccer, Rugby, Cricket, Tennis, track and field, Field hockey and even Karate. I was my happiest in a sporting arena.

2) As a "late starter", what do you think about kids specializing in sports (particularly swimming) at such a young age?

Personally I don’t see the need in specializing at a young age, kids need to be kids, I believe they need to build their athleticism and concept of self by participating in individual sports as well as team sports. There is definitely a need for variety as it allows the kids to see exactly where they will succeed. I believe allowing kids to specialize later in life will allow for increased longevity.

3) In the past year, have you tried any new things in your swimming training? 

I’ve never been afraid of experimenting and trying something new. After the hype surrounding USRPT I decided that I would give it a try. While the science behind it may be sound and while there may have been success for some swimmers with this modality I found it impossible to buy into. It is my experience that most coaches succesfully incorporate elements of USRPT into their “well balanced” programs. Ultimately I have a problem with anyone functioning in absolutes. In everything in life, as in swimming there is a need for balance. Since Commonwealth games I have switched back to a more balanced swimming program and I couldn’t be happier.

4) What items are you currently working on with your freestyle technique

We made some changes before Barcelona in 2013 and while there were some benefits I believe I lost the “connection” especially as I started fatiguing. Lately we’ve been focusing on trying to be a bit flatter in the water and trying to avoid too much shoulder rotation

5) What do you do for dryland training

I’ve been working with Nick Folker and Train FASST for quite some time now. Nick and I go back to 1999 and he’s one of the best in the business. He tailor makes our workouts based on our specific needs and weaknesses. I have also been working with two Ki-Hara practitioners here in Phoenix. I love the difference the Ki-Hara resistance stretching has helped me with recovery and injury prevention

6) How about nutrition, do you follow any program for food and supplements? 

I’ve gone back and forth with various diets. PH Balanced diet, High Fat Low Carb, Blood type diet etc. I’ve found that at this point in time as long as I am eating healthy, avoiding excess sugar that I will recover properly and feel great on a day to day basis. I believe I had a tendency to over think my dietary requirements but now I just trust my body and intuition about what I need and how much of it I need.

7) As a veteran swimmer, what things do you wish you knew 10 years ago?

I wish I’d had a chance to help the overall development of South African swimming from a far earlier stage, after 2004 we had a huge platform to improve the professionalism and marketability of swimming. We unfortunately didn’t capitalize on that. Secondly I wish I’d done better to market myself and my successes. Unfortunately at this point in time with 2016 Olympics less than 2 years away I do not have a single sponsor.

8) Do you perform any particular injury prevention or recovery techniques? 

I have spent quite a bit of time talking to Kelly Starrett and have been following his principles for mobility. He’s an unbelievable guy with a wealth of knowledge, I feel fortunate that I’ve been able to tap into that.

9) What are some of the most important things you've implemented into your training? 

I think one of the most underrated things in terms of training is recovery. I have tried to ensure that I get as much sleep as possible at night. I have a device called an Earthpulse, it is an electromagnetic sleep device that helps improve sleep and overall performance.

10) What are you goals for 2015 and 2016?

Between now and 2016 I’d like to find several sponsors who will be willing to walk on this Olympic journey with me. If I attend the Olympics in Rio I will be the first South African to ever attend 5 Olympic games. It is an honor that I would like to achieve more than anything else. When it comes to the Rio games, I would like to represent South Africa in the 50 freestyle and I would like to be a part of the 4x100 free and 4x100 medley relays.

11) Why do you think there is resistance in adding 50 meter stroke events during international competition? 

Ultimately I can only speculate as to the real rational behind not including the 50m of strokes. In all honesty it makes no sense, if you want the crowd involved you have to cater to them. Modern sport is about the excitement, creating characters, setting events apart. As far as I am concerned there is a need for the 50’s of stroke and a 4x50 medley relay. I think we should question the current event order and scheduling. The World Championship schedule works fairly flawlessly and caters to the 50’s. At the end of the day it would be foolish not to include 50’s of stroke. Smaller nations who may not have top 100m swimmers all of a sudden also have the opportunity to compete for medals.

12) What are you working biomechanically for your butterfly?

For butterfly I am trying to improve my thoracic mobility as well as improve my shoulder flexibility. I need to improve my initial catch on the water so everything we are doing is geared towards that right now.

Follow @rolandschoeman and Instagram is Roland-Schoeman

Friday Interview: Shinichiro Moriyama, PhD, Discusses Intra-Abdominal Pressure

1. Please introduce yourself to the readers (how you started in the profession, education,
credentials, experience, etc.).
My name is Shinichiro Moriyama. I am an associate professor and competitive swimming coach at Japan Women’s College of Physical Education in Japan. I was awarded my PhD from National Institute of Fitness and Sports in 2014. My mentors are Department director of Sports Science Yuichi Hirano at Japan Institute of Sports Sciences and Professor Futoshi Ogita at National Institute of Fitness and Sports. Professor Hirano granted the advice about the importance of trunk training in human performance, and Professor Ogita guided me in the swimming science. It was the splendid experience for me to have studied under them.

I started coaching of the swimming club from 2002 at Japan Women’s College of Physical Education. I want to take a role to relate competition swimming to science.

2. You recently published an article on intra-abdominal pressure (IAP) and swimming. What is IAP and how is it tested?
IAP changes as a result of synchronous contraction of the abdominal muscles, diaphragm and pelvic floor muscles and, through synergistic action with muscle activity of the trunk, contributes to lumbar spine stability.

We measured intra-rectal pressure as IAP using 1.6-mm-diameter catheter-type pressure transducer. Intra-rectal pressure that is more than 10cm from anus gives almost the same value as IAP measured using a laparoscope.

3. What did your study look at?
We hypothesized that IAP during front crawl swimming is affected by stroke rate, one of the factors affecting swimming velocity, and increases with swimming velocity.

We investigated to ascertain IAP during front crawl swimming at different velocities in competitive swimmers using swimming flume and to clarify the relationships between stroke indices and changes in IAP.

4. What were the practical implications for coaches and swimmers from your study?
It is difficult to suggest the practical implications from our study. Because it was no relationships between IAP and stroke indices. Additionally IAP during swimming was less than 15% of maximum voluntary IAP.

On the other hand, within-subject, IAP tends to increase with increased swimming velocity. Therefore the training to increase IAP during swimming may be effective means to swim faster.

5. Do you think the results would be different if you had older, elite or untrained swimmers?
We compared IAP of elite swimmers with untrained swimmers. As results, under their maximal efforts, we could not see significant difference between elite and untrained.

From this result, significant difference may not be accepted between the elite swimmer with older swimmer.

6. What if you had the swimmers perform around 2.0 m/s?
I instruct the swimmer who advanced to the A finals by the 50m free-style at Japan championship. Her IAP is not remarkably different from other swimmers.

7. Would other strokes change the results?
We are very interested in about IAP during other strokes. We are making an experiment plan now. Crawl stroke and back stroke have rolling motion, and butterfly stroke and breast stroke have up-down motion. Therefore we expect that the former’s (crawl stroke and back stroke) IAP waveforms are remarkably different from the latter’s (butterfly stroke and breast stroke). Additionally IAP development during butterfly strokes that are the highest load to trunk are highest in all strokes.

8. How should the results of your study be used for dryland and core training?
This question is very difficult for us. Recently, including me, many coaches and swimmers work on core training. We wanted to solve the meaning of core training by measuring IAP during swimming. But as results, IAP during swimming was much lower than we expected. Therefore, at least, our findings do not appear to support the effectiveness of core training performed by competitive swimmers aimed at increasing maximal IAP.

9. What research or projects are you currently working on or should we look from you in the future?
Even now, we are continuing experiment of IAP during swimming. We want to solve the meaning of core training and roles of trunk during swimming someday.

Friday Interview: Dr Chris Mills and Dr. Mitch Lomax Discusses Breast Influence on Biomechanics

1. Please introduce yourself to the readers (how you started in the profession, education,
credentials, experience, etc.).
Dr Chris Mills
I completed my PhD in 2005 at Loughborough University in the UK, where I was funded by British Gymnastics to investigate force dissipation characteristics of landing mats and gymnasts with the aim of reducing injury. I continued to focus my research on lower and upper body soft tissue motion and for the past 6 years have worked closely with the research group in breast health at the University of Portsmouth. As a part of this group we work closely with garment manufactures to improve their design, as well as conducting fundamental scientific research studies. Most of the research within breast biomechanics to date has been land based however recently a swimwear manufacturer approached our group with an interesting project. We combined our experience of breast biomechanics, swimming mechanics and physiology (via Dr Mitch Lomax, who has contributed to your website in the past) to investigate the effect of breast support on trunk motion during swimming.
I’m a Sport and Exercise Scientist and a Senior Lecturer in Sport and Exercise Physiology at the University of Portsmouth, UK. I gained both my PhD (2007) and MSc (with distinction, 2001) from Brunel University, UK, and my BSc (Hon) from Luton University (1998). I’m an accredited Sport and Exercise Scientist with the British Association of Sport and Exercise Sciences (BASES), Chartered Scientist (Science Council). I have been an advisor to the Amateur Swimming Association of England and was involved in the preparations of the English Pistol Shooting squad for the Commonwealth Games in Glasgow. My main sporting research interest is in swimming and predominantly breathing limitations.

2. You recently published an article on breast displacement in freestyle and breaststroke. Is there any other research on this area in swimming?
At present there is very limited research on breast mechanics, let alone the movement behavior of the breasts in water and the impact breast support has on swimming technique. Clearly more research is needed in this area to ascertain whether swimming costume design modifications could benefit performance.

3. What did your study look at?
We were interested in investigating whether varying levels of breast support influence swimming technique. On land, a lack of sufficient breast support has been shown to decrease performance and increase pain, however we did not know if the same was true in water. We were also particularly interested to understanding whether regular swimsuits afforded any support to the breast during swimming.

4. What were the results of your study?
Key findings suggested that although trunk motion was not altered with varying levels of breast support, a swimsuit was no more effective at reducing the movement of the breasts than not wearing one at all! Despite trunk motion not being effected by breast support conditions, ongoing research hopes to determine whether other aspects of swim stroke mechanics (such as hand path etc.), that may influence swim performance, are effected by the amount of breast support.

5. What were the practical implications for coaches and swimmers from your study?
Female swimmers with larger breasts may wish to consider wearing an additional sports bra under their swimsuit to reduce breast motion and compress the breasts against the chest wall (decreasing the trunk moment of inertia and the possibility of the breasts obstructing the desired hand path during swimming). Our findings revealed that a sports bra (traditionally used for landing based activities) was more effective as reducing breast motion than a swimsuit.

6. Do you think the same results would have occurred with faster women? Hi-tech suits? Women of smaller breast size?
This is difficult to answer however if the women swim faster the drag created would also increase. If the breasts are not ‘restrained’ sufficiently this may increase the ‘bagging’ effect (from our paper) and increase form drag and hence decrease performance. Hi Tech suits usually have a higher level of compression (similar to compression garments on land), however we have not tested this. Unpublished research from the group has found that upper body compression garments do reduce breast motion during land based running. It may be possible that a similar increase in compression may also reduce breast motion (similar to that of the sports bra in this study). Women with smaller breasts do not experience the same magnitudes of breast motion (on land) therefore in the water they are also likely to experience reduced magnitudes of breast motion when compared to women with larger breasts. The ‘bagging’ effect and potential increases in form drag may not be as great for women with smaller breasts.

7. Does male pec size influence swimming? Could this be one reason why "bulkier" male swimmers anecdotally did better with the full body suits?
This is a difficult one to comment on and really outside our area of expertise. The only aspect to consider is that men pecs are mainly muscle and hence are used to generate joint motion; however the female breast does not contain any muscle (just mainly fat and glandular tissue), hence minimizing their form drag may be beneficial to swimming performance.

8. What can swim suit manufactures do to improve swim suits for women?
I would recommend an increase the amount of compression afforded around the breasts to move their center of mass closer to the trunk and help to streamline their shape to decrease form drag. A higher neckline may also help to decrease the ‘bagging’ effect described in our paper. Possibly some structured support, similar to an encapsulation bra. Finally, appropriate sizing, that can cater more for trunk circumference and breast sizes variations, within a, for example, UK size 12 swimsuit.

9. What research or projects are you currently working on or should we look from you in the future?
We currently have two more papers under review associated with breast motion during water based activities. We are also seeking collaborative links with garment manufacturers interested in developing this area of research.

Future of Swimming Training

Take Home Points on the Future of Swimming Training:

  1. Smart technology is on the verge of dramatically enhancing swimming performance, be ready for the revolution.
Swimming is one of the most biomechanically difficult sports. Unlike other sports, swimming works against water while in a horizontal position. The unfamiliar horizontal position makes all stroke corrections more difficult. Water also creates resistance during any motion, making improvements harder! This motion creates drag impeding performance to a greater degree than air resistance.This makes receiving feedback difficult. In fact, Stefan Szczepan beautifully described his work and the role of immediate feedback in swimming.

We reviewed Szczean and Zatoń (2014) research in the latest Swimming Science Research Review. Zatoń (2014) split sixty-four male swimmers into a control and an experimental group. The experiment consisted of 4 freestyle swimming trials of 25 meters. The first two trials were pretest and the third and fourth trials were the experimental trials. In the experimental trials, the swimmers were instructed to "reach out further". 

There was significant improvement in stroke length, stroke rate and swimming velocity.

Future of Swimming Training

Overall, there is a lack of immediate feedback in the sport of swimming despite the shown benefit. As technology decreases prices, these methods must be integrated more in swimming. Whether the feedback is through telemetry systems or visual cues, having immediate feedback will reduce errors. As technology, systems my provide automatic feedback based on performance

Biomechanics, Injury Prevention and Coaching

For example, MOOV has created a "smart watch" which provides instantaneous feedback during running. Full disclosure, I consult with MOOV, so I first hand understand the potential of this product. Imagine a device which you wear on your wrist and lets you know when your hand speed is slowing, force production is decreasing, or hand path is altering, then coaches you for improvement! This can improve biomechanics, reduce injuries, increase motivation, and other improve swimming!

Dryland and Recovery

Athos, a smart clothing, is capable of measuring muscular activity when worn! If Athos, or another company, can create waterproof clothing, then huge advancements in muscular training and recovery are possible. Imagine knowing when a muscle is completely fatigued from the resting neuromuscular activity...pretty cool! If this product isn't made waterproof, it still a beneficial product for dryland, knowing exactly which muscles are activity during each exercise. 

Sleep and Recovery

Sleep and recovery have huge potential for swimming improvement. Currently, recovery and sleep and not individualized, although everyone is unique and individual recovery patterns are needed. There are products like BioForce HRV and other smart watch technologies which track sleep and heart rate variability, a potential marker for monitoring recovery. 

Nutrient Levels

One possibility for training and monitoring is blood analysis without skin penetration. As far as I know, this technology doesn't exist. However, if someone can create a device which continuously monitors nutrient levels in the blood or via saliva, exact nutrient levels is possible. This can maximize energy, recovery, and performance!


If these products are accurate, then the world of swimming and coaching will be transformed. For example, a swimmer is held responsible throughout the main set, not allowing them to "slack" or take an unnoticed break. For the coach, the device will monitor biomechanics more accurately and continuously than the coach. For injuries, knowing when pain starts during a set and seeing the muscular activity or biomechanical deviation at this point in time will influence technique and reduce injuries. Also, knowing when and what to eat for maximal performance, as well as knowing how much sleep is needed for maximal performance has exciting potential! Once again, this will change the sport, so harnessing technology and analyzing data will become even more paramount for success. Make sure you are ready for the next phase of sports enhancement!

  1. Zatoń K, Szczepan S. The impact of immediate verbal feedback on the improvement of swimming technique. J Hum Kinet. 2014 Jul 8;41:143-54. doi: 10.2478/hukin-2014-0042. eCollection 2014 Jun 28.
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.