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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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Kick Timing in Butterfly

Take Home Points on Kick Timing in Butterfly

  1. The kick helps counteract the actions of the arms and orients the body horizontal, an ideal position for forward propulsion.
  2. The first kick occurs at the arm entry.
  3. The second kick occurs at the arm exit. 
Many realize swimmers do not pull their arm past their body, but anchor their arm and move their body past their arm. Despite this knowledge, implementing this strategy is difficult, especially on butterfly. Now, everyone around a pool deck has heard the comment "anchor the arm, then swim past it", but often times this cue falls short of improvement.

In swimming, understanding physics may help highlight ideal biomechanics. For me, physics and knowledge of forces helped me understand a "hip-driven" freestyle stroke and is now unlocking the idea of swimming past my arms on butterfly. Before you move on, make sure to read "How to swim the butterfly" for an indepth review of butterfly biomechanics. This piece goes over a lot of information, yet the timing of the kick and role of the kick with the catch is absent, a vital flaw. The kick, as written, should be small and fast. Ideally, the kick helps counteract the actions of the arms and orients the body horizontal, an ideal position for forward propulsion.

First Kick

Just before hand entry, the first kick occurs. This motion helps counteract the action of the arms, but also raises the hips and body for the first propulsive phase. Once again, orienting the body in a horizontal position is a must, as this provides streamline for the swimmer as their arms gain propulsion. The kick during the entry counteracts the vertical forces which act upon the arms. 

Second Kick

The second kick happens as the hands finish the catch phase. This kick maintains an elevated hip position. This kicks helps keep the hips high, the body in a relative streamline, as the chest and head rose for a breath.


Many perform large kicks during the butterfly, but this is likely unnecessary, bringing the body out of streamline. Although it may help some swimmers time their streamline during propulsion of the catch, it is still wasteful and beneficial if eliminated. Remember, small, fast kicks which counterbalance the arms and streamline the body optimize butterfly horizontal velocity.

Written by G. John Mullen who 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.

Dolphin Kicking Data Case Study

Take Home Points on the Dolphin Kicking Data Case Study

  1. Underwater kicking tempo variability does exist requiring individualized recommendations.  
Implementing data is highly specific. Unfortunately, it is easy to put your body in an elite swimmers and expect the same outcomes. I'll never forget playing basketball in my driveway as a youngster and imaging I was Anfernee "Penny" Hardaway. I'd imagine shooting, dribbling, and scoring just like him, unfortunately I was a scrawny, short white kid, not a 6'7" NBA all-star. 

It is easy to compare yourself to great athletes in any sport and the age of data, it is easy to use elite swimmer data for your programs. I was working with an elite National level team who was using kicking tempos during an underwater kicking set. This team had each swimmer locked into a goal tempo for their dolphin kick which was the grabbed from Russell Mark's great USA Swimming Webinar. Each swimmer was busting their hump for a 0.4 dolphin kicking tempo, with many failing. 

I'd assume most coaches took this data and told their kids to kick with a 0.4 tempo, but is that truly best for sub-Olympic swimmers? Sure, 0.4 is a great goal tempo for some, but gradual progressions and realistic goals based on the anthropocentric and skill levels are needed.

Individualized Dolphin Kicking

In order for individualization, testing is required. Scott Colby of USA Swimming performed a "pseudo-study" timing 15-meter kicking time and 0-5 m glide time. Similar testing is easy and is possible by testing a swimmer at the beginning of workout each day. Another option is to perform 20x15-m underwater fast @:30 seconds and time one swimmer per repetition. On this trial, time the time from 0 - 5 meters, 0 - 15 meters, and their kicking tempo. If you're good with a watch, getting one person for repetition is simple, if you don't have your Masters in watch skills, do as best as you can. 

With this data you can determine if each swimmer is kicking to their true potential, provide goal times, and biomechanical instruction.

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.


Once again, one size doesn't fit all for elite swimmers. In the age of data, there is no reason not to use the data as a guide, but individualization remains king and is required. Remember to test, intervene, and re-test under race conditions. These methods will benefit your swimmers greatly by engaging them and pushing them towards their full potential as they strive for improvements. Small improvements results in great change.

Written by G. John Mullen who 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.

Friday Interview: Dr. Marc Epilot, Ph.D Discusses Underwater Kicking

1. Please introduce yourself to the readers (how you started in the profession, education, credentials, experience, etc.).
My current profession is at the French Institute of Sport in Paris (INSEP). The INSEP is a campus where some of the best French top athletes train to prepare the next international competitions and Olympic Games. I’m in charge of some aspects of the performance observation which mainly includes the video analysis and biomechanics. 

I have a Ph.D in biomechanics and motor control from the University of Paris Descartes. During the last years, I have been collaborating with the research department of the French Swimming Federation on different projects involving motor control and learning, biomechanics and engineering. My main field of expertise is about to understand the underwater phases of the starts and turns; both the glide and the underwater undularoty swimming.

I started working with the French Swimming Federation on that topic in 2005 during my master degree. I was coming back from Canada where I had spent the first year of my master and discovered biomechanics. Being myself a swimmer, I wanted to apply what I was learning on biomechanics and motor control to what is a passion for me. I wanted to help the athletes and the coaches to become more efficient and reach higher performances. At that time French swimming was starting a brand new research program focused on the starts and turns. Studying the race analysis of the 2000 and 2004 Olympic Games, it indeed appeared that French swimmers were loosing a big amount of time during those parts of the race. I was hired to work on that project and more especially on the underwater phases of the start; to improve and update our knowledge on that topic and to collaborate with the French coaches. My job was then to work on fundamental scientific program, to develop tools for accurate underwater analysis and to have poolside applied working sessions with coaches and athletes.

2. You published an article on the ideal time to start kicking after a start. Why is the timing of this important?
It is well known that swimmers experience the highest velocities during the start after water entry or during the turns after having pushed on the wall. The main aim of the gliding phase of the start or turns is to maintain as long as possible that extra-speed by holding a streamlined position. When the swimmer’s gliding velocity becomes lower than what he can produce using underwater legs propulsion, the swimmer is supposed to start kicking. If the swimmer waits to long and starts to kick too late, his velocity will be lower than expected. Consequently, he will loose time and will have to spend more energy to reach again that maximum speed. On the opposite, if the swimmer starts kicking to early, the speed will be decreased faster than expected. The swimmer will loose energy producing undulatory movement without succeeding to produce higher velocities than if he had hold the streamlined position. It would be waste of time and energy.
Previous studies have shown that the average maximum speed reached by a top swimmer is included between 1.9 and 2.2 m.s-1. One of the aims of our article was to convert that velocity threshold into a distance, which is much more easily identifiable for a coach or even an athlete. Nevertheless, the ideal time to start kicking we have presented in our article strictly depends on each swimmer’s skills to produce velocities during the underwater undulatory swimming. We wanted to give to coaches a global frame of reference to start working. That frame of reference has to be adjust for each swimmers.

3. Did your swimmers only perform freestyle and do you think breaststroke and butterfly would have a different ideal time to start kicking?
Our swimmers only perform freestyle. The ideal time to start kicking strictly depends on the maximal velocity that the swimmer is able to reach using only legs propulsion. Consequently, the results would have been the same for butterfly but would have been different for breaststroke.

4. What were the main findings from your study?
That study was a part of the whole program we have tried to lead on the understandings of the underwater phases of the starts and turns. The program was built in 3 stages: 1- To identify the causes of the French swimmers inefficiency and propose immediate and basic solutions, 2- To identify what the optimal motor coordination that have to be produced by the swimmers to reach higher velocities during underwater swimming phases, 3- To experiment a motor learning program headed to improve swimmers’ skills and measure the factors that may have been modifies during the program.

During the first stage, we asked to the swimmers two realize two types of starts: 1- The same as if they were in a competition, 2- A start during which they had to hold the streamlined position as long as they can or until they reached the surface (no leg movements). It clearly appeared that the swimmers were all starting kicking way to early. The glide phase was interrupted almost immediately after water entry and some swimmers started to kick more than 2m before what they were supposed to be. Measuring the mechanical energy spent by the swimmers during those two types of starts, it clearly appeared, that initiating underwater propulsion to early swimmers were loosing lots of time and were just wasting energy producing movement but without succeeding to produce higher velocities. Indeed the figures below show that during 70% (i.e. the first 2.5m after complete immersion) of the underwater phase of the start, the swimmer spends lots of energy producing movements (graphic on the left) but has the same velocity (or even slower) than if he was just gliding (graphic on the right).

The aim of the second stage of our work was to have a new sight on how the swimmers are controlling their limbs and joins during the underwater phases of the starts and turns. Talking with the coaches or reading different books and scientific articles, two elements clearly appeared. First, the idea of the top-down control of the limbs was widely spread; i.e. the concept that the dolphin kick is a sequential movement begun with the shoulders or the hips and headed to the feet. The second element was that the control of one specific joint, usually the knee, was supposed to be the key stone of the swimmer’s efficiency during the dolphin kick. Our work clearly showed that those two concepts are inaccurate. The motor coordination during the underwater undulatory swimming aims to build articular and muscular synergies during which all the joins are involved, coordinated and synchronized depending the the phase of the movement (upbeat or downbeat). No top-down organization appeared.

Finally the third stage of our work aimed to understand what kind of adaptations may appear on young good swimmers (French national level) if they were involved in a short motor learning program to develop skills during the underwater undulatory swimming. The program lasted 9 weeks with 3 sessions of 30 minutes per week. Those sessions were sometimes directly integrated to the “regular training” or presented as specific and independent exercises. Work was done in and out of the water as well and the program was oriented around 3 main axes: 1- Exercises headed to improve the swimmers’ sensory-motricity (improvement of the bind between what they feel and what they do). 2- Biofeeback exercise (give objective information in return after doing an exercise… video feedback, oral information, …). 3- Exercises to improve the postural and dynamic interaction of the joints, limbs and muscles. Our results showed that even for such a short program performance can be greatly improved (average increase of underwater velocity: 30%). Swimmers having a large amplitude and a small frequency tend to adjust their amplitude/frenquency ratio. Angles of attack of the superior limbs (trunk, arms and fore-arms) are all reduced which lower the resistances. Actions of the joints and the muscles are modified and resynchronized on each phase of the kick to produce a more efficient propulsion. And finally, the type of contraction of the muscles is also modified. Lumbar muscles present a more tonic pattern of contraction while the legs muscles present a more phasic pattern of contraction.

5. What is the biggest mistake you see in swimming starts, in regards to 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.
Adapted from Arellano et al. (2008)

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.

6. Do you think your results would differ based on the Omega kick-back starts?
The new Omega start blocks change indeed some parameters of the start, such as the water entry velocity or the angle of entry which are two parameters that can have an impact on the time to initiate the kicking part of the underwater phase of the start. So I guess that the glide would have to be a bit longer than what we founded during our works. Nevertheless, the time to initiate kicking is also determines by the swimmer’s capacity not to lose the extra-velocity given by the aerial phase of the start during the glide. If his velocity becomes higher at water entry thanks to the new blocks but that the swimmer loses all that velocity at water entry and during the glide, the results would be the same.

7. How would pool depth alter your results?
Pool depth effect on the swimmers efficiency during the starts and turns is still unclear. The idea of having a deeper pool, like the Cube during the Beijing Olympic Games, is to think that swimming deeper the starts and turns, the swimmers will experience less hydrodynamic resistances (decrease of the wave drag) and will be more efficient. The first researches studying the effect of the pool depth on the swimmer’s efficiency pointed out that hydrodynamic resistance were significantly reduced until reaching a 1m-depth (Lyttle et al., 1999; Vennel et al. 2006). Below that threshold, the effects of the wave drag drag on the swimmer can be ignored. In that case, the pool depth won’t have any effect on our results.

On the opposite, some recent studies published from 2010 (Marinho et al., 2010) and based on different simulations, showed that drag force is twice lower when the swimmer is at a 3m depth than at the water surface. In that case, swimmer experiencing less resistance, the time to initiate kicking would be a bit delayed.

8. What is still uncertain about underwater kicking off the start?
They are still many questions unsolved about underwater kicking. As we said, the effect of the pool depth is still uncertain. Moreover, if the swimmers decide to have a deeper trajectory, the question of the optimal trajectory to return to the surface can be a problem and a source of unknown.

The propulsion mechanisms involved in underwater swimming (i.e. the vortices of Karman) are particularly unknown either, while they directly determine the swimmers’ efficiency. Those vortices are affected by many factors and those relationships are quite unclear so far. And the underwater kicking during backstroke events has almostly never been investigated.

To my point of view, the new improvements of computational fluid dynamics (CFD) will also provide some very interesting findings on underwater kicking but will also generate some more questions either.

9. What research or projects are you currently working on or should we look from you in the future?
I have finished the last stage of the research program on motor learning I was describing a bit above. I have now to focus on working with the coaches on how to apply those results on top athletes instead of young good swimmers.

Moreover working now at the French Institute of Sports, I will mainly focus on swimming applied engineering to design, develop tools for accurate, non-invasive, and fast video and biomechanical analyses and to ingrate them into our new pool. 

Friday Interview: Ryan Atkinson Breaks Down Dolphin Kicking

1. Please introduce yourself to the readers (how you started in the profession, education, credentials, experience, etc.).
I completed both B.Sc. (2008) and M.Sc. (2010) in Kinesiology at the University of Western Ontario, specializing in sport biomechanics, and am a certified strength and conditioning specialist with the NSCA. Currently, I provide biomechanics and performance analysis support for swimming based out of the Toronto National Training Centre. I am a former swimmer and coached for several years at the club and varsity level before taking my first full time job as a sport biomechanist. While coaching, I also provided strength and conditioning programming and biomechanics consultations and clinics for regional swimming programs. Through the help of my colleagues, I became connected with Swimming Canada’s Senior Biomechanist, Dr Allan Wrigley. I hadn’t been exposed to that career path before, but it appealed to me and I was fortunate to be offered a job as a biomechanist for winter sport programs, supporting freestyle skiing and snowboarding. While it was a departure from swimming, I found that it really challenged my assumptions from a coaching perspective and has allowed me to better analyze swimming in an unbiased way.

2. You recently published an article on underwater dolphin kicking (Importance of
sagittal kick symmetry for underwater dolphin kick performance also see Brief Swimming Review Edition 16), could you briefly discuss what is well known about UDK?
When performed well, underwater dolphin kicking (UDK) can be faster than surface swimming. This is because surface swimming speeds are limited to a length-determined “hull speed” of each individual swimmer, whereas there is no upper-limit for speed underwater due to the absence of wave resistance.

From a technical standpoint, it has been well established that human swimmers are more effective at the downkick phase than the upkick phase. Humans are somewhat limited in their ability to perform the upkick phase due to anatomical restrictions about the hip, knee and ankle joints; however, swimmers with hypermobile knee and ankle joints that allow them to hyperextend beyond 180 degrees have an anatomical advantage that may allow them to better perform the UDK.

3. What are some of the biggest questions remaining about UDK?
It is important to know how to optimize UDK technique for an individual, based on various anthropometric, strength and flexibility parameters. Much of the recent research on UDK has relied on computer simulations to evaluate technique; however, these studies have been limited in scope and applicability to the general swimming public. Thus, training studies are required to test findings from simulations. For example, it has been shown through computer simulations that swimmers with limited passive plantarflexion range of motion are able to improve UDK performance by increasing their ankle flexibility, yet this has not been confirmed directly through practical research.

Another area that requires immediate attention is injury risk associated with increased UDK training. In certain populations, UDK training has been thought to increase the incidence of low-back pain. Research is required to determine which movements specifically are related to low-back pain, and if UDK teaching can be improved so that less stress is placed on the lower-back without compromising performance.

4. What did your study specifically look at?
We investigated the mechanics of the UDK across a range of swimmers, including varsity swimmers and Olympians, to determine how symmetry between the downkick and upkick phases is related to performance. Using a twelve-segment model, we evaluated various kinematic parameters during downkick and upkick phases, including joint marker paths, joint angles, vertical toe velocities, and whole body displacements and horizontal velocities.

5. What were your main findings?
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.

6. How should coaches use this information for teaching beginners UDK?
It is evident that novice swimmers have more difficulty performing the upkick phase than the downkick phase. Coaches should emphasize teaching the upkick phase of the dolphin kick, specifically recruiting the muscles of the posterior chain without excessive lower back flexion or knee flexion. Training the kick on the side will allow the swimmers to focus on kicking in both directions. Larger amplitude kicks are more appropriate for this stage of learning than high frequency kicks. This can be taught on the land as well by performing single or double leg lifts in a prone, streamlined position, paying close attention to recruiting the gluteal muscles for leg lifts rather than the lower back.

7. What about more advanced swimmers, how should UDK biomechanics be advanced?
Coaches of advanced swimmers should focus on 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.

8. You note exceptional thoracic spine, knee, and ankle mobility as some elite characteristics. Do you feel these characteristics are innate or developed?
Both. Some humans are gifted with exceptionally mobile joints that allow them to move through extra-ordinary ranges of motion with relative ease. Some of this mobility can be trained through targeted stretching and mobility exercises instructed by a qualified coach or health care professional, especially at the thoracic spine, ankles and hips. Prior to engaging in this type of training, athletes should be screened to determine the source of the athletes’ limitations and what, if any, training or treatment modalities may be effective in improving their mobility [perhaps the Swimming Troubleshooting System].

9. Were there any outliers in your study (some elite kickers who didn't have the same characteristics)?
The fastest swimmers, based on FINA point scores, weren’t necessarily the fastest UDK performers. Furthermore, several of the high level UDK performers had larger velocity fluctuations than expected. This can be partly explained by the greater resistance experienced at higher velocities, but may also indicate that these swimmers have room to improve. Conversely, the swimmer with the apparently “best” UDK technique (most stable velocity) wasn’t the fastest at UDK, but did have the highest body length-normalized velocity and ranked much higher among his peers in UDK velocity compared with his overall swim performance.

10. Do you think UDK is faster prone or on the side?
Swimmers will be fastest in the position that they train in most often at high speeds. Either position has a tradeoff; when kicking in a supine or prone position at shallower depths (less than one-half metre) some energy from the kick is lost to the creation of surface waves (observed as ripples on the surface); when kicking on the side, swimmers may have difficulty staying symmetrical in the frontal plane due to their natural buoyancy torque, which would inhibit their maximal force production. Ultimately, UDK position should be part of a complete start or turn strategy, so factors such as push-off position and breakout timing need to be considered. A useful strategy for freestyle and butterfly swimmers is to push-off on the side, and to begin kicking on the side and use the kick to facilitate a transition to the front without any sudden twists or changes of direction.

11. Do you think there will be any big progressions in UDK, if so what do you predict?
Several of the best UDK performers in the world are anomalies, in that they achieve success mostly due to incredible anatomical or strength advantages rather than superior technique. Improved knowledge of UDK technique by coaches and trainers, and increased emphasis during training will lead to widespread improvements in UDK performance and strategy. A major shift will occur when freestyle sprint swimmers accept that they can be faster remaining underwater to 15m, and will extend their start and turn breakout distances to nearly 15m underwater during 50m and 100m events.

12. What research or projects are you currently working on or should we look from you in the future?
Recently, I collaborated with regional research partners on a swimming start study, looking at the effect of body lean on start performance. I am currently not involved in any research projects, but am working on applying research methods to develop better tracking, monitoring, and evaluation criteria and methods for starts, turn and underwater skills. This includes basic coaching resources, such as benchmarks and checklists, and more sophisticated biomechanical methods using instrumented starting blocks and accelerometers.

Thanks Ryan
Follow Ryan on Twitter @Swimmingsmarter

Brief Swimming Review Volume 1 Edition 10

In an attempt to improve swimming transparency, a brief swimming related literature review will be posted on Saturday. If you enjoy this brief swimming review, consider supporting and purchasing the Swimming Science Research Review

Changes in Peak Swim Speed in Elite Freestyle

Most believes Masters swimmers decrease in speed as they age from strength losses. However, the decreases in velocities for each age are not well known or understood. A Swiss study looked at data of 70,059 freestylers aged 10 - 40 from 50 to 1,500 m.

"For women, age of peak swimming speed increased in 50 m from 18.9 (s = 2.3) to 20.4 (s = 4.2) years but decreased in 1,500 m from 25.0 (s = 13.1) (1996) to 18.1 (s = 3.7) years. For 100-800 m, age remained at 19.1 (s = 1.1), 19.3 (s = 1.1), 18.7 (s = 1.5) and 18.5 (s = 1.3) years, respectively. For men, age of peak swimming speed decreased in 50 m from 23.0 (s = 4.0) to 23.0 (s = 3.5) but remained for 100-1,500 m at 22.5 (s = 1.4), 21.4 (s = 0.9), 20.3 (s = 0.9), 20.3 (s = 0.9) and 20.3 (s = 1.1) years, respectively. Age was positively associated with swimming speed for 50-800 m, but negatively for 1,500 m (Rüst 2013)."
Unlike other sports (specifically distance running), distance swimmers do not age well. This is likely due to burn out and decreased training volume/intensity with aging.

Vitamin D Insufficiency not Linked with Reduced Performance!
Many feel vitamin D is associated with strength and performance, but little research has analyzed performance and vitamin D levels.

"Performance parameters were also compared between vitamin D sufficient (n=27), insufficient (25(OH)D ranging 20-29.9 ng/ml, n=42) and deficient (25(OH)D less than 20 ng/ml, n=11) participants. No significant associations were found between serum 25(OH)D concentrations and any of the performance measures (Dubnov-Raz 2013)."

"Vitamin D insufficient/deficient swimmers did not have reduced performance (Dubnov-Raz 2013)", similar to what we concluded in March: "vitamin D supplementation does not improve strength and athletic performance (Mullen 2013)".

Related Reading

Kicking and Sprint Freestyle
There is much debate about the role of the legs in freestyle, most notably by Dr. Rushall suggesting kicking provides no forward propulsion, while others, like Gary Hall, Sr., feels the legs are crucial. A recent study had nine female swimmers perform two maximal 25-m freestyle swims without and with leg kicking.

"Using the legs, the mean swimming velocity increased significantly. On the contrary, the velocity and the orientation of the hand, the magnitude and the direction of the propulsive forces, as well as the Froude efficiency of the arm stroke were not modified. The hip intra-cyclic horizontal velocity variation was also not changed, while the index of coordination decreased significantly. A significant decrease (13%) was also observed in the inclination of the trunk. Thus, the positive effect of leg kick on the swimming speed, besides the obvious direct generation of propulsive forces from the legs, could probably be attributed to the reduction of the body's inclination, while the generation of the propulsive forces and the efficiency of the arm stroke seem not to be significantly affected (Gourgoulis 2013)."

Wow, a lot of conclusions in the abstract and unfortunately, not much can be taken from this abstract, as the methods are not clear (I mean, did they simply not kick or use a pull buoy?). However, the claim "the obvious direct generation of propulsive forces from the legs" seems a bit bearish. Other than that, the decrease coordination and increased inclination make a case for the legs balancing the body (or the actions of the arms) during freestyle. Unfortunately, I don't think (I need to read this whole study) this study brings the answers to this long debate, especially since they only looked at 25-m speed, a non-Olympic distance.
The use of hypoxic training is extremely common in the sport. Unfortunately, the differences between hypercapnea and hypoxia are not understood by many in the swimming community. "This study used an innovative technique of pulse oximetry to investigate whether swimmers can train under hypoxic conditions through voluntary hypoventilation (VH) (Woorons 2013)". 

In this study, ten trained swimmers perform freestyle under three conditions:

  1. Normal breathing
  2. Hypoventilation at high pulmonary volume
  3. Hypoventilation at low pulmonary volume
"In VHlow [hypoventilation at low pulmonary volume], SpO2 fell down to 87% at the end of the series whereas it remained above 94% in VHhigh during most part of the series. Ventilation, oxygen uptake and end-tidal O2 pressure were lower in both VHhigh and VHlow than in NB. Compared to NB, [La] significantly increased in VHlow and decreased in VHhigh (Woorons 2013)."

These results are from suggesting hypoxic training is essential for swimming, all it suggests is oxygen levels are decreased during breathing at low pulmonary volume and this increases lactate concentration. Clearly, more studies on the effects of hypoventilation training are necessary.

Related Reading
Breathing and Swimmers' Posture
Individual Breathing Patterns are King!
Friday Interview: Dr. Mitch Lomax


  1. Rüst CA, Knechtle B, Rosemann T, Lepers R. The changes in age of peak swim speed for elite male and female Swiss freestyle swimmers between 1994 and 2012. J Sports Sci. 2013 Sep 9. [Epub ahead of print]
  2. Dubnov-Raz G, Livne N, Raz R, Rogel D, Cohen A, Constantini N. Vitamin D Concentrations and Physical Performance in Competitive Adolescent Swimmers. Pediatr Exerc Sci. 2013 Aug 29. [Epub ahead of print]
  3. Gourgoulis V, Boli A, Aggeloussis N, Toubekis A, Antoniou P, Kasimatis P, Vezos N, Michalopoulou M, Kambas A, Mavromatis G. The effect of leg kick on sprint front crawl swimming. J Sports Sci. 2013 Sep 9. [Epub ahead of print]
  4. Woorons X, Gamelin FX, Lamberto C, Pichon A, Richalet JP. Swimmers can train in hypoxia at sea level through voluntary hypoventilation. Respir Physiol Neurobiol. 2013 Sep 4. doi:pii: S1569-9048(13)00304-2. 10.1016/j.resp.2013.08.022. [Epub ahead of print]
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 founder of Mullen Physical Therapy, the Center of Optimal Restoration, head strength coach at Santa Clara Swim Club, creator of the Swimmer's Shoulder System, and chief editor of the Swimming Science Research Review.

Friday Interview: Dr. Yves Jammes Discusses Fin Kicking

1. Please introduce yourself to the readers (how you started in the profession, education, credentials, experience, etc.)
I work since 42 years in the field of exercise physiology. My double formation of MD and scientist (DSci of physiology and biochemistry) has allowed me to make a multidisciplinary approach of exercise physiology. Moreover, my implication in several military research programs with the French Navy has obliged me to develop new devices to explore working activities in immersion and deep dives.

2. You have published three articles on fin kicking, could you please explain what we now know about fin kicking?
The three articles were supported by a new device allowing to continuously measure the force propulsion during swimming which does not impede the swimming motion. This allowed us to reproduce a protocol similar to those measuring the cardiorespiratory function and surface electromyographic (EMG) activities when cycling or running in dry air condition. The main result is that no “ventilatory threshold” occurs during maximal fin kicking. This indicates that the aerobic mechanisms are only involved in fin swimming (
Jammes, Y., Coulange, M., Delliaux, S., Jammes, C., Gole, Y., Boussuges, A., Brerro-Saby, C. et al. (2009). Fin swimming improves respiratory gas exchange. Int J Sports Med 30: 173-181). This was also the first time that EMG activities in muscles participating to fin swimming were recorded, showing patterns of motor units recruitment similar to those described during incremental cycling (Jammes Y, Delliaux S, Coulange M, Jammes C, Kipson N, Brerro-Saby C, Bregeon F. EMG changes in thigh and calf muscles in fin swimming exercise. Int J Sports Med. 2010 Aug;31(8):548-54).

3. What are some of the unknowns about fin kicking?
The main unknowns concern biochemical changes that are lactic acid and oxygen free radicals production during swimming. This obliges to place a venous catheter to sample blood during immersion which might be responsible for some infectious risks.

4. How much transference is there in fin to non-fin kicking?

I have no answer to this question. In particular, I do not know if the aerobic metabolism also prevails in non-fin kicking.

5. Do you think fin kicking transfers to swimming?

Same answer

6. How do you think swim coaches should implement fin kicking?

Yes, because the maximal aerobic power is increased in fin kicking

7. Who is doing the most interesting research of kicking? What are they doing? Very few scientific teams work on fin kicking since the princeps work by Donald, K.W. and W.M. Davidson (1954) (Oxygen uptake of booted and fin swimming divers. J Appl Physiol.7:31-37).

Since, interesting data have been reported on oxygen uptake during fin swimming by others (Morrison, J.B.
Oxygen uptake studies of divers when fin swimming with maximum effort at depths of 6-176 feet. Aerosp Med. 1973; 44:1120-1129; McNeill, A.W. Measuring instrument for the determination of the oxygen consumption of scuba divers in open water. Aviat Space Environ Med 1979; 50: 742-744; Pendergast, D.R., Tedesco, M., Nawrocki, D.M., and N.M. Fisher. Energetics of underwater swimming with 1SCUBA. Med Sci Sports Exerc 1996; 28: 573-580; Zamparo, P. Pendergast, D.R., Termin, B., and A.E. Minetti. How fins affect the economy and efficiency of human swimming. J Exp Biol 2002; 205: 2665-2676).

8. What makes your research different from others?
The main originality consists in the simultaneous measurements of force propulsion, respiratory function, and quantitative EMG activities. This was never performed before.

9. Which teachers have most influenced your research? My master Pierre Dejours (CNRS, Strasbourg, France) who died 4 years ago.

10. What mistakes still exist with fin kicking on swim teams? I think that a lot of work must be done to evaluate the interest of the changes in length and shape of fins in terms of appropriateness between ventilation and oxygen uptake and the quantitative EMG signals which allow to make the part of the different limb muscles at work .

11. What research or projects are you currently working on or should we look from you in the future? Unfortunately, I will be retired from academic position in few months and this research field will not be continued in my laboratory.

The Serape Effect and Swimming

One common theme in sports is returning to past lessons, like the serape effect and swimming.  

Sometimes innovation takes us to uncharted territory, while other times it brings back to where we had been.  Although recently popularized by Vern Gambetta, The Serape Effect was first noted in the 1960’s in a kinesiology text by Logan and McKinney.

What is it?
The Serape Effect for swimming is commonly discussed in and around the pool, but often without the formal terminology.   Essentially, the Serape Effect describes the functional anatomical interrelationship between the upper and lower limbs: the left arm is tied to right leg, while the right arm is tied to the left leg.  When we frame the limbs in this interrelationship, the torso acts as a “relay center” to transmit “messages” from the outer limbs. 

A serape is an outer garment commonly worn across the torso in many Hispanic cultures.  The anatomy of muscles, fascia, and other tissues flows along this pattern, yet also extends into the lower body, as depicted in the photo below.  You might describe these anatomical patterns as slings across the torso.  In this post we’ll explore in greater detail how The Serape Effect for swimming can help us gain a clearer understanding of the stroke, injury prevention, and dryland methods. 

Below Coach Gambetta describes the Serape Effect in context for terrestrial sports.  However, those familiar with his work know these concepts transfer directly into swimming rotation for free/back (and possibly the prevention of rotation in fly/breast).

“In ballistic actions such as throwing and kicking, the serape muscles add to the summation of internal forces. They also transfer internal force from a large body segment, the trunk, to relatively smaller body parts, the limbs. For example, the serape effect functions in throwing by summating, adding to, and transferring the internal forces generated in the lower limbs and pelvis to the throwing limb. 

There is a definite interaction between the pelvic girdle on the left and the throwing limb on the right by way of concentric contraction of the left internal oblique, right external oblique, and serratus anterior on the right at the initiation of the throw. The pelvic girdle is rotating to the left and the rib cage is rotating to the right.”

How can we understand and exploit the Serape Effect for swimming, both in the water and on land?  Below are a few possibilities:

Stroke teaching – Faults such as crossing over and hula hooping are often seen as arm or hip issues, but are best viewed and arm AND hip issues.  Whereas we might focus on the arms for crossing over, many recognize poor arm position may result from compensating for unstable hips.  Likewise, sloppy hip action may result from poor arm movements (see, Lats on Lats) Deciphering the exacts will vary by swimmer, but creating lasting stroke fixes (and not merely band aids) will depend on treating the body as a whole.  Understanding this effect for swimming can accelerate the learning process.

Power – Although the serape effect itself has not been the subject of any formal studies on power generation in swimming (to the best of my knowledge), the interplay between the lower and upper body has been studied.  Dr. John covered one recent study in which strengthening the lower body increased upper body strength even with no additional upper body training ( see Kicking Improves Arm Strength).  It is unclear if this result came from a generalized effect on the nervous system or if it indeed relates to an interrelationship between opposing upper and lower body limbs.  However, strengthening the plant (leading) leg for throwing is often associated with increased velocity.  A similar effect may be at work in swimming given the findings from Dr. Prins' lab showing the role of stable hips during long axis strokes.

Kick timing – The interaction of the kick and arms is the most critical application of the Serape Effect in swimming.  Consider Glen Mills’  description of kick timing and hand entry: You'll feel your hand enter the water and at that point, the opposite leg should be kicking down. Think of it almost like a corkscrew in the water, you're twisting down the entire length of your body, hoping that the opposing actions will snap back to the other side, and help both the initiation of the pull, and the kick.” 

Dryland – The Serape Effect for swimming likely won’t change anything drastically in your programming (unless your program is nothing more than rotator cuff exercises and crunches).  Everything from medicine ball rotations, to bird dogs, to certain yoga poses will involve the Serape Effect.  Even saggital plane movements involve the Serape Effect in preventing rotation.  Understanding the Serape Effect can help you assess weaknesses and imbalances for individualized exercise selection. 

Pain – How the body compensates in response to pain may affect movement.  Be aware that protective movement in the presence of shoulder pain may cause residual effects elsewhere.   If the shoulder is injured, the hips may adopt compensatory movements; it’s also possible the hips may cause problems in the shoulder.   These answers aren’t always obvious, but know that the body is designed with close interrelationships via the Serape Effect in various movements.

What’s old is new, and what’s new is old.  Consider the functional anatomy behind the Serape Effect and swimming to optimize interventions both in and out of the water.  Above all, the Serape Effect is one conceptual model to help explain interrelationships between different areas of the body. 

  1. McKinney, G.  Logan.  W.  Kinesiology (1960)
  2. Gambetta, V.  Functional Path Training
By Allan Phillips. Allan and his wife Katherine are heavily involved in the strength and conditioning community, for more information refer to Pike Athletics.

Ankle Range of Motion in Swimming and Plyometrics

Take home points:
  1. Vertical leap and size supposedly does not influence flutter kick speed
  2. Plyometric training is highly beneficial in adolescents and should be implemented, however this must be done under strict supervision and on appropriate surfaces. Future studies must compare plyometric training to equal volume of swimming training.
The University of Connecticut looked at factors that influence flutter kick speed. They compared recreational swimmers to NCAA athletes and discovered some obvious swimming news to anyone in the swimming community:
  • Plantar flexion (pointing your toes) positively influences flutter kick capability.

Ankle Range of Motion in Swimming and Plyometrics

The study did not find a positive correlation with the athlete's size or their vertical jump power, and more embarrassing is that the recreational swimmers had a higher vertical jump then the NCAA athletes (8 inches)! Another note, the NCAA swimmers mean 50 meter time was 32.1 seconds.

The vertical leap test measures the ability to assess power, explosive strength and the use of strength. Future studies should look at vertical leap between sprint swimmers vs. distance swimmers. One would expect sprinters to have a higher vertical leap due to their higher concentration in type II muscle fibers.

The second relevant article was done in the UK and studied how a 8 week plyometric training program influenced swimming start variables. This plyometric program was closely monitored, progressive, and used proper (high) intensities to have maximum changes. On a safety note, plyometric training can be dangerous if used too aggressively too soon or on improper surfaces. The plyometric training enhanced the swimmer's time from start to head entrance, distance off start and 5.5 meter time. 5.5 meters was used, because in their pre-findings this distance was before children had influences from kicking and breakout. The children averaged a decrease by .59 seconds in 5.5 meters! This is a 15% improvement. The habitual training group also improved, but only .12 seconds. This .49 second difference would easily influence any race in swimming.

The only variable that was unaffected was angle of entrance from the dive. I would have guessed this angle would have changed too, but if only velocity was increased then it makes sense that no significant changes were noted.

  1. McCullough AS, Kraemer WJ, JS, Solomon-Hill GF Jr, Hatfield DL, Vingren JL, Ho JY,Fragala MS, Thomas GA, Häkkinen K, Maresh CM. Factors affecting flutter kicking speed in women who are competitive and recreational swimmers. J Strength Cond Res. 2009 Oct;23(7):2130-6.
  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):2137-4.
By G. John Mullen founder of the Center of Optimal Restoration, Swimming World Magazine Columnist, creator of the Swimmer's Shoulder System, and chief editor of the Swimming Science Research Review.