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.

Friday Interview: Stefan Szczepan Ph.D. Discusses Immediate Feedback in Swimmers

1. Please introduce yourself to the readers (how you started in the profession, education, credentials, experience, etc.).
Hi, my name is Stefan Szczepan. I'm a scientist at University School of Physical Education in Wroclaw, Poland and I work at the Department of Swimming. This year I received a doctor degree. I'm interested in motor control and learning included motor skill acquisition processes in water environment, especially teaching communication, forms of instruction, augmented feedback, and practice schedules. My mentor is Professor Krystyna Zaton, the head of Institute of Physical Activity in Water Environment in my University. She guides me in the science. I’m very proud with this relationship and I am very thankful for the trust and the knowledge transfer. My most recent research is about the impact of immediate verbal feedback and concurrent visual feedback on the improvement of swimming technique. I am the author or co-author of few articles in research journals. I connect theory with practice while teaching swimming and swimmers trainer.

2. You recently published an article immediate feedback and swimming. What are the different types of feedback?
Feedback is sensory information that results from movement. There are two types of feedback: intrinsic (integral) and extrinsic (augmented feedback). Intrinsic feedback is the sensory information arising as a result of physical activity by the means of sensory mechanisms (exteroreceptors and proprioreceptors). Information that derives from the receptor allows for movement regulation as well as the adjustment of motor task completion to the desired model of physical activity. Extrinsic feedback is formed after the completion of a motor activity and is transmitted by a third. Examples of extrinsic information are verbal communication, gestures, video, timer displays. There are several distinct types of feedback which are categorized according to the time of its transmission: concurrent feedback (provided during motor task concern continuous information), immediate feedback (provided during motor task concern discrete information) and delayed (transmitted after the completion of the motor action). Types of feedback are the most important for me. The most effective information is verbal and immediate. If you are interested in it – follow this link:

3. In your study you worked on improving the swimmers stroke length, can you explain how
you did this?
This study that we conducted together with Professor Zaton concerns the issues related to the importance of the transfer of feedback in an immediate manner to the learner during the learning swimming process. The work shows that the time in which the feedback reaches the learner is important in the motor control and that it improves swimming technique. The feedback communicated to the learner in real time manner regarding a performed motor function allows for the removal of errors in the short-term memory or prevents their formation. I chose a simple kinematic parameter of swimming movement as stroke length to confirm the importance of immediate verbal feedback. In this way the emergence of an error in the time-space structure of swimming motility was eliminated. The objective numerical dimension of the mistakes made allowed for a quantified relationship between the shortening of the swimming stroke length and the constant frequency of the propulsive movements. These factors led to a decrease in the efficiency of swimming, which was noted in the swimming velocity and a decrease in the economization of the swimming techniques, as indicated by the index SI. For these purpose I used special wireless tools including a system, transmitter and receiver for swimmer and teacher. This gave a possibility of a verbally and immediately control of swimming movement. It's an amazing technology that I spent significant money to develop and it works incredibly well.

4. What were the main results of your study?
The use of these tools in an experiment conducted on the experimental group, in which the information regarding the execution of the performed activity was transferred to students in an immediate manner, indicated that the swimming stroke is significantly improved along with an increased swimming speed while maintaining the same frequency of movements. This resulted in an effective movement in the aquatic environment. In the control group, however, where such information was not given, there was no observed swimming stroke elongation while maintaining the same frequency of movements. The transmission of immediate feedback in order to prevent the occurrence of errors or to eliminate them entirely, this also resulted in an improvement in the economization of swimming motor functions. The economization of swimming techniques was assessed using the index of SI [stroke index], which was considered as its measurement. Increase in the index SI values will see a decrease in the physiological cost of effort. In the control group this increase was not observed. It looks like that work tool and the assumptions of study can be used in any other motor swimming motor activity, not only stroke length. An example would be learning and improving movements of the legs and hands, body position in the water or coordination aspects, as well as other swimming motor elements.

5. What were the practical implications for coaches and swimmers from your study?
With the breaking of communication barriers, the following improve:
  1. Preventing the occurrence of errors and removing them from the motor memory.
  2. Improving motor structures and the cost reduction of physiological effort.
  3. Conditions will be created to improve the quality of swimming techniques with various degrees of accomplishment of utilitarian.
  4. Recreational values of physical culture, as well as antagonistic values noticeable in the competitive sports oriented towards maximizing achievement. 
The applied value of the method used, in which the verbal feedback was transmitted instantaneously in an immediate manner, in the practice of teaching and coaching is the enrichment of the communication technology regarding the correct structure of swimming motor functions. This is the main principle. The above assumptions are based on the physiological structure of human memory, whose different types are classified depending on how long information is stored in them. At first site, takes include human motor memory and second site augmented immediate verbal feedback. I give a method with used immediate verbal feedback for improves swimming technique and effectively the swimming learning process.
6. Do you think the results would be different if you had older, elite or untrained swimmers?
For sure people perceive information differently, due to age, sex or seniority. Probably we would observe differences between elite and non swimmers. This study showed the impact of immediate feedback on young swimmers. It can be apply for all swimmers, but the results may be a little different. In the future, I will plan other studies that answer on this question clearly.

7. Do you think immediate tactile or visual feedback would have different results?
Teaching and improvement of swimming technique is effective when external information is transmitted in three forms: words, images and practical actions. In case of the tactile I need to appeal to kinesthetic differentiation. It is one of the most important motor abilities. This ability is a precise perception of strength, time, and space. Feeling spatial movements, feeling of movement speed, what it’s called "water feeling” makes precise control of the movements. Tactile feedback can improve kinesthetic differentiation and makes to decrease energy cost and achieving better results. We deal this issue at my University. As regards the visual feedback I use special device. For example, it is the optical fiber giving the swimmer concurrent visual information. The light beam also provides the swimmer with the information on swimming speed. The ability to control the speed of swimming is an important part of preparation during swimming training. This is especially important when the desire is to obtain a pure training stimulus. Swimming with a defined - constant speed impacts on economical labor, and allows for maintaining a low physiological cost. Therefore, the development of a method that allows for acquisition and improvement of that skill is an important methodical goal in the process of swimming training optimization.

8. When working on biomechanics, how do you suggest tapering down feedback when the swimmer is progressing?
The role of the teacher is to provide feedback as long as the swimmer will acquire motor habit. Motor habit in human motor memory are formed after several thousand repetitions, therefore, the time of their acquisition is different. The next step in order to improve the quality of swimming mobility is multiple individual repetitions of the correct structure for motion, which was acquired by the use of immediate, verbal regulation regarding the swimming motor structures. Of course, if there are errors the teacher must again respond. Feedback can be addictive. In order to avoid the negative effects of frequent augmented feedback various techniques have been applied such as faded, bandwidth, summary, average or self-controlled schedules have been used.

9. Should teams utilize immediate auditory feedback?
I have a plan to develop my device and bring it to the swimming team. This allows the delivers of the individual swimmer and for the whole group. It will be easier to conduct training.

10. What makes your research different from others?
An innovative aspect of the subject undertaken is to identify empirically, that the time in which the information reaches the learner is important in the learning process and that it improves swimming technique. My work examines important aspect impeding the process of teaching of swimming and technique improvement. The interference in didactic communication – it is particularly noticeable when an exercise is executed in an atypical environment, for example in water. The aquatic environment hinders the reception of information because a number of disruptive factors such as the distance between the teacher and the learner or ambient noise favors errors in a given exercise. Thus, the environmental factors make it hard to use verbal feedback to its full communicative potential in the process of swimming acquisition or technique improvement. It may also be challenging to immediately eliminate or prevent (within short-term memory) errors as or before they appear, as I said early. I believe that the results of the present research work should contribute to defining the actual significance of immediate verbal feedback in swimming acquisition and improvement.

11. Which teachers have most influenced your research?
The person who influenced the most on my research has been my professor Krystyna Zatoń. For me she is a really big scientist. All the time she teaches me how to be better. It requires a lot of my sacrifices. Since I started working with her at Department of Swimming my life sped up, but I like it. I can learn a lot from a great biomechanic of swimming, a professor Marek Rejman too. We work together. I guess that we are good scientific team. Also I take inspiration from different scientists who are engaged in motor control and learning. There are many in the world, so I need to check of the database brand new publications.

12. What research or projects are you currently working on or should we look from you in the future?
I’m currently working on the evaluation of the achievements of swimmers. This evaluation is performed during motor activity in real time. Ability to take correct feedback to evaluation swimming technique can increase swimming performance. Usually, data are obtained from delay, e.g. with using movement analysis software. In addition, the aquatic environment interferes common available device for the evaluation, e.g. Infrared. Therefore I develop telemetry measuring swimming techniques. It enables in real-time provide feedback on the structure of the swimming movement. Wireless method of assessing swimming techniques can be used for research purposes to create maps of swimming techniques, to quantify. In addition, I’m interested in biofeedback and the implementation of transcranial magnetic stimulation (TMS) in the verification of feedback in swimming learning. Both issues seem to be good for my future. Many questions pertaining to increase the process of swimming acquisition and teaching remain unanswered and further research appears necessary. I hope it finishes successfully. I have one rule in my life, that says never stop.

Thanks Stefan!

Breast Size and Swimming

Take Home Points on Breast Size and Swimming:
  1. Swimming suits are ineffective in reducing breast displacement in freestyle and breaststroke.
Few in the swimming community are comfortable discussing today's topic: influence of trunk and breast during swimming. Considering the biomechanical influence of these body parts, it is an obvious research need. Also, if you talk or have worked with female swimmers, you'd likely agree the trunk and breast can influence swimming biomechanics and velocity. However, having research on the subject and understanding the effects of varying size breast with varying support helps coaches and swimmers make individual adjustments for each swimmer and their anthropomorphics.

There has been research on breast displacement in different bras during varying land activities (walking, running, etc.). This research found an obvious assumption: increased breast support caused decreases in breast displacement. Unlike most other sports, swimming is unique as it is in the horizontal plane, performed in water, both influencing breast displacement.

The breast likely influence body rotation during freestyle and backstroke. Previous work by Payton (1999) suggest rotation is approximately (66°) when taking a breath  than when breath holding (57°) whilst swimming at 1.8 m/s.

During short axis strokes (breaststroke and butterfly), results in breast displacement in the sagittal plane. Breaststroke causes approximately 63 degrees of trunk extension, causing resistance and slowing the swimmer (Colman 1998).

Understanding breast displacement is also important for non-elite swimmers, as some women experience pain during land exercise.

Mills (2014) had six large-breasted females (34 F, 34 F, 30 G, 34 G, 36FF and 34HH; age: 29; mass: 78.9 kg;  height:1.66 m) perform two swimming trials (one freestyle and one breaststroke). Each swimmer was recorded while swimming in the flume with multiple underwater markers on anatomical landmarks. Participants’ bra size was established by a trained bra fitter and fitted in the sports bra used for testing (using the fit criteria as set out by White and Scurr, 2012). The testing consisted of front crawl swimming at 1.08 m/s and breaststroke swimming at 0.94 m/s (water temperature: 30.5°C).

Breast Displacement During Freestyle

Mediolateral breast displacement (side to side), has a temporal pattern of medial, then lateral movement. These patterns were consistent, no matter the breast support condition. Breast displacement in the anterioposterior (forward and backward) varied with different support conditions. 

Overall, the greatest displacement occured mediolaterally in the swimsuit condition (7.8 cm), while the least displacement occurred in the sports bra condition (3.3 cm). Overall, the sports bra condition decreased breast movement, but not significantly. 

There was greater trunk roll in the sports bra condition, while the swimsuit had the lowest trunk rotation (43.1 vs. 39.3). However, different strategies were obtained with varying support for the participants. There was a strong negative relationship between trunk roll and anteriorposterior breast displacement and superiorinferior breast displacement. Overall, more trunk roll results in less breast displacement in freestyle. 

Breast Displacement During Breaststroke

Trunk extension exhibited a single peak of 55-60% of the stroke cycle. Superiorinferior displacement peaks inferiorly at 70% through the stroke in the bare-breasted condition, but not in the swimsuit and sports bra condition. 

Like freestyle, the bare-breasted condition had the greatest displacement in the superioinferior direction (3.7 cm) and the least in the mediolateral direction while wearing the sports bra (1.4 cm). This difference was significant. 

The least amount of trunk extension occurred in the swimsuit condition, but there were no significant differences between conditions. 

Breast Displacement Considerations for Swimming

This study notes minimal difference between the swimsuit and bare-breasted condition, suggesting current swimwear minimally supports women with larger breasts. Overall, the displacement of the breast was approximately half the displacement of land based sports. Unlike land sports, breast size did not impair body roll. However, more water becomes trapped in the the the swimsuit condition opposed to the sports bra condition. Overall, swim suit manufactures should consider swimwear with more breast support for maximizing performance. 

"The relationship between trunk roll and breast displacement was an interesting and unexpected finding as it was anticipated that women who exhibit greater trunk roll would induce significantly greater mediolateral breast displacement. There may be several reasons for this; first, the flow velocity of the water in the flume may not be uniform with changes in water depth. This may mean that the flow velocity is greater nearer the surface and decreases with depth, therefore affecting the drag on the swimmer. With increased trunk roll, the breast may be closer to the water’s surface and exposed to higher flow velocities resulting in a “pinning” effect on the breast, pushing it closer to the trunk, decreasing anterioposterior breast displacement and consequently minimising superioinferior displacement. Similarly, the breast being closer to the surface of the water may also cause an increase in wave drag (Vennell, Pease, & Wilson, 2006). An increase in wave drag may also have a similar “pinning” effect to that associated with an increase in flow velocity. Finally, flume construction may mean that the wave energy cannot be dissipated and is rebounded back off the side of the flume wall towards the swimmer. An increase in trunk roll may expose more of the trunk and breast to this rebound wave, again acting to “push” or “pin” the breast towards the trunk minimising breast anterioposterior and superioinferior displacement. It would be beneficial for a future study to examine any differences in breast motion during swimming both in the flume and in pool environments and also to manipulate trunk roll from low to high to determine its effect on breast displacement using an intra-participant design (Mills 2014".

Conclusions on Breast Displacement in Swimming

Greater breast displacement occurred in freestyle compared to breaststroke. The swimsuit was ineffective for reducing breast displacement. More research on elite swimmers and more advanced swimwear (ie high tech suits) will help suit manufactures optimize swim suits for women with varying breast size. Overall, breast size did not impair swimming trunk motion. 


  1. Mills C, Lomax M, Ayres B, Scurr J. The movement of the trunk and breast during front crawl and breaststroke swimming. J Sports Sci. 2014 Sep 5:1-10. [Epub ahead of print]
  2. Payton CJ, Bartlett RM, Baltzopoulos V, Coombs R. Upper extremity kinematics and body roll during preferred-side breathing and breath-holding front crawl swimming. J Sports Sci. 1999 Sep;17(9):689-96.
  3. Vennell R, Pease D, Wilson B. Wave drag on human swimmers. J Biomech. 2006;39(4):664-71.
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.

Adam Peaty´s Word Record at the 50m Breaststroke: Drag Force Analysis

Take Home Message Adam Peaty´s Word Record: 

  1. Adam Peaty took one second to enter the water after the starting signal. For the remaining 25.62s, he was gliding 39.85% of the time and 60.15% producing thrust by the limbs
  2. The gliding is related to passive drag and ranged between 42.30-75.44 N over the 50m
  3. The propulsion by the limbs is related to active drag and ranged between 75.17-103.36N
  4. The active drag was almost 56% higher than the passive drag.

Adam Peaty made a splash breaking the men’s 50m Breaststroke WR at the European Championships held last August in Berlin (final time: 26.62s). In the semi-final Adam shaved 0.05s to 2009 Cameron van der Burgh´s record (WC, Rome). Watching the race there are several things that I could highlight, but for today the focus is: (i) the start (reaction time of 0.62s; water entry at approximately 3.5m and 1.0s after the starting signal; water break at almost 15m); (ii) the gliding in each stroke cycle and; (iii) the last kick and final glide of almost 2.5m. You can compare this start with Ruta Meilutyte WR at the 100m Breaststroke last October.

I decided to measure the total time Adam Peaty was gliding (during the start after the water entry, in each stoke cycle and finish) or producing thrust by the limbs. Surprisingly, the new world record holder spent 39.85% gliding and 60.15% producing thrust (figure 1). 

One of the main challenges in Breaststroke is the drag force acting upon the swimmer. It is known that at a given speed, Breaststroke is the technique submitted to the highest resistance of the four strokes (Kolmogorov et al., 1997). The drag force can be broken down into passive drag and active drag. Passive drag is the resistance acting upon the swimmer being towed or gliding, without any further limb actions (Barbosa et al., 2013). The active drag is the resistance submitted to the swimmer when he is performing limb action to propel himself in the water (Barbosa et al., 2013). So, based on the data reported in figure 1, I estimated the active and passive drag over the race. Procedures are similar to what was reported in an earlier piece. Theoretical models were selected, hence no experimental or numerical simulations were conducted.

The water break happened at roughly 15m. He did one single stroke cycle before the 15m mark. So, for that first 15m, the active drag is almost neglectable (figure 2, dash line). As expected the fastest splits happened at the beginning (2.26 m/s) and end of the race (1.97 m/s). Speed was measured having the top of the head (i.e. vertex) as reference. This imposes a bias for the finish because the hands reach the wall first than the head. So, unfortunately the speed for the last 5m is overestimated. 

That said, the passive drag ranged between 42.30N and 75.44N over the 50m race and the active drag between 75.17N and 103.36N (figure 2). These figures are higher than what is reported in the literature (Kolmogorov et al., 1997; Vilas-Boas et al., 2010) which is kind of obvious since we are analyzing a WR… 

Another interesting thing to pinpoint is that the active drag was almost 56% higher than the passive drag. Even though some care should be taken, similar relationship was found for young swimmers at front-crawl (Barbosa et al., 2013). The ratio between active drag and passive drag is called “total drag index”. The rationality behind the “total drag index” is that it can be considered as a swimming efficiency index. For a given speed, if two swimmers with similar passive drag are compared, the one with lower active drag could be considered as having a better technique. In Adam´s case, his “total drag index” was approximately 1.78. Some other time I might benchmark several swimmers so that we have a better understanding on this parameter.


  1. Barbosa TM, Costa MJ, Morais JE, Morouço P, Moreira M, Garrido ND, Marinho DA, Silva AJ (2013). Characterization of speed fluctuation and drag force in young swimmers: a gender comparison. Hum Mov Sci. 32: 1214-1225
  2. Kolmogorov S, Rumyantseva O, Gordon B, Cappaert JM (1997). Hydrodynamic characteristics of competitive swimmers of different genders and performance levels. J Appl Biomechanics. 13: 88-97
  3. Vilas-Boas JP, Costa L, Fernandes RJ, Ribeiro J, Figueiredo P, Marinho DA, Silva AJ, Rouboa AI, Machado L (2010). Determination of the drag coefficient during the first and second gliding positions of the Breaststroke underwater stroke. J Appl Biomech 26: 324-331
By Tiago M. Barbosa PhD degree recipent in Sport Sciences and faculty at the Nanyang Technological University, Singapore.

Dryland and Stroke Biomechanics

Take Home Points:

  1. Strength training may have a positive effect on swimming biomechanics.
  2. Individualized dryland programs are necessary, considering the effects of dryland on future biomechanics.
  3. More research on the effects of land strength and dryland are required.

This is an example chapter of Dryland for Swimmers. Order your copy to day for $59.99!
Biomechanics are the largest contributor for swimming success. A possible explanation for this might lie in the nature of swimming; forces being applied against a fluctuate element with the posture of the human body being the most important vector against propulsion. Swimming performance is thus determined by the athletes’ ability to produce forward motion while reducing water friction, or drag (Toussaint 1990; Pate 1984). The possible biomechanical effects (propulsive abilities and drag) from drylandmust also be considered. Unfortunately, many resistance training studies do not compare biomechanics, making the results of each study impossible to extrapolate the biomechanical results of training. 

Four studies observed improvements in stroke mechanics, specifically increased stroke length, (Toussaint 1990; Strass 1986), increased stroke rate (Girold 2006) and decreased stroke depth (Girold 2007) after strength training. None of the included studies investigated whether there was a possible training effect on active or passive drag.

Girold et al. (2006) found that improved swimming performance was positively associated with an increased stroke rate of the last 50m of a 100m freestyle time trial after 3 weeks of in-water resistance training (tethered to an elastic tube). Swimming velocity is the product of stroke rate and stroke length, (Craig 1985) and both factors should be optimized for maximal performance. Although stroke rate has been associated with maximal swimming velocity, (Wakayoshi 1995) stroke length is likely more important (Wakayoshi 1993).

For instance Craig and colleagues (1985) observed that stroke length was the factor that differentiated finalists from non-finalists during the US Olympic trials in 1984, and another study suggested that increased maximal velocity was an effect of increased stroke length (Wakayoshi 1993).

Girold et al. (2006) found decreased stroke depth after both combined resisted- and assisted-sprint swim training (tethered to an elastic tube pulling against or towards swimming direction), and dryland strength training. The researchers found increased stroke rate both in the combined resisted- and assisted-sprint group and in the control group, but not in the strength training group. Although the findings were not fully consistent, the authors concluded that the decreased stroke depth was a consequence of maintained stroke length when stroke rate was increased. However, if body rotation remains stable, decreased stroke depth may reduce the biomechanical momentum of the propulsive muscles, and thus decrease the potential for propulsion.

In the study from Toussaint and Vervoorn, (1990) they observed increased stroke lengths at equal maximal swimming velocities after resistance training on the MAD system. The observed change was suggested to come from increased maximal swimming power, although maximal swimming velocity was unchanged. Similar observations were also made after dryland maximal strength training in the study from Strass, (1986) but not in the studies from Aspenes et al., (2009) Trappe and Pearson, (1994) Tanaka et al. (1999) or Roberts et al. (1991). Faude et al. (2008) compared the effects of low volume training with high-intensity versus high- volume training with low intensity, and observed no differential effects on mean stroke rates in either 100m or 400m maximal freestyle. High volume, low-intensity training is sometimes recommended for improving swimming economy, but none of the studies included in this review support that notion. However, the hypothesis needs more studies before any conclusion can be drawn.

Strength training may have positive effects on stroke characteristics, but so far the evidence is inconclusive. Future RCT studies can probably be designed to study the effect of, or preservation of, stroke characteristics with strength training.

Order Dryland for Swimmers 


  1. Girold S, Maurin D, Dugué B, Chatard JC, Millet G. Effects of dry-land vs. resisted- and assisted-sprint exercises on swimming sprint performances. J Strength Cond Res. 2007 May;21(2):599-605
  2. Girold S, Jalab C, Bernard O, Carette P, Kemoun G, Dugué B. Dry-land strength training vs. electrical stimulation in sprint swimming performance. J Strength Cond Res. 2012 Feb;26(2):497-505.
  3. Aspenes S, Kjendlie PL, Hoff J, et al. Combined strength and endurance training in competitive swimmers. J Sports Sci Med 2009 Sept; 8 (3): 357-65.
  4. Aspenes ST, Karlsen T. Exercise-training intervention studies in competitive swimming. Sports Med. 2012 Jun 1;42(6):527-43
  5. Toussaint HM, Vervoorn K. Effects of specific high resistance training in the water on competitive swimmers. Int J Sports Med 1990 Jun; 11 (3): 228-33
  6. Craig Jr AB, Skehan PL, Pawelczyk JA, et al. Velocity, stroke rate, and distance per stroke during elite swimming competition. Med Sci Sports Exerc 1985 Dec; 17 (6): 625-34
  7. Wakayoshi K, Yoshida T, Ikuta Y, et al. Adaptations to six months of aerobic swim training: changes in velocity, stroke rate, stroke length and blood actate. Int J Sports Med 1993 Oct; 14 (7): 368-72
  8. Trappe S, Pearson D. Effects of weight assisted dry-land strength training on swimming performance. J Strength Cond Res 1994 Nov; 8 (4): 209-13.
  9. Tanaka H, Costill DL, Thomas R, et al. Dry-land resistance training for competitive swimming. Med Sci Sports Exerc 1993 Aug; 25 (8): 952-9
  10. Strass D. Effects of maximal strength training on sprint performance of competitive swimmers. In: Ungerechts BE, Wilke K, Reischle K, editors. Vth International Symposium of Biomechanics and Medicine in Swimming; 1986 Jul 27-31. Bielefeld: Human Kinetics Books, 1986: 149-56
  11. Faude O, Meyer T, Scharhag J, et al. Volume vs. intensity in the training of competitive swimmers. Int J Sports Med 2008 Nov; 29 (11): 906-12
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.

Race Analysis and Video: Katie Ledecky 400 Free World Record

Take Home Points on Race Analysis and Video: Katie Ledecky 400 Free World Record
  • Katie Ledecky broke the 400, 800 and 1500m freestyle world records in roughly one and a half month, being the first American swimmer holding the big-three middle- and long-distance records after Janet Evans.
  • She swam the 1500m at a 1:02 pace, the 800m in negative split and the 400m with two splits bellow one minute.
  • There is a trend for the number of strokes per lap decrease with increasing distance (1500m: first half 38 and second half 39-40; 800m: 40-41; 400m: first half 39 and second half 40-41).
A good piece of news is when a man bites the dog. Katie Ledecky breaking another world
record is not a surprise or comes out of the blue. But to be the first woman after Janet Evans holding the 400, 800 and 1500m freestyle records, that is truly… remarkable. We are talking about three world records broken in roughly one and a half month, wearing textile swimsuits and still on the road to the season´s major competition. On top of that, she posted the 2nd best time in the world at the 200m event (as on 10 August 2014; table 1).

As you can imagine I did not have much time to carry a deep analysis. So, my purpose for today is to compare the split times and number of strokes per split in the four events. Split times were retrieved from the competitions´ websites. I will report both the 50m (figure 1) and 100m (main text) split times. The stroke count (number of strokes per 50m split) was done after downloading the videos from the web. Unfortunately for the 1500m event, I failed to find the full race. There is one video available that is a 7 minutes condensed version of the race from beginning to end. So, I had to interpolate some missing data (dash line in figure 2). If you wish the number of stroke cycles rather than the number of strokes, just divide the figures reported by two.

Regarding the split times (figure 1): (i) a very stable swim pace at the 1500m (around 1:02) and she end the race in 1:00.7; (ii) we can see clearly the negative split at the 800m event; (iii) in the 400m, two splits bellow one minute (57.74; 59.98) and remaining two inside the “double-0” (1:00.68; 1:00.46); (iv) in the shortest event, splits where 56.64 and 58.52, respectively. Probably several countries would like to have their top-sprinters doing these 200m splits.

The partial difference (table 2) of Ledecky´s split times in the 1500m in comparison with the: (i) 800m is between -0.44% and 3.89%; (ii) 400m, 3.05-4.20%; (iii) 200m, 5.60-6.80%. I.e. the first half of the 1500m and the 800m paces are fairly similar (on average a 0.40s difference per 100m split). In the last 100m of both races (i.e. 1400-1500m and 700-800m) she clocked 1:00.7 and 1:00.12 (difference: 0.58s).

Concerning to the stroke counts: (i) there is a trend for the number of strokes per lap decrease with increasing distance; (ii) number of strokes increases in the second half of the 1500m event from 38 to 39-40; (iii) in the 800m event the number of strokes was rather stable, between 40 and 41; (iv) in the 400m event, we can see again that the number of strokes increases in the second half from 39 to 40-41; (v) as expected the 200m is the race with the highest number of strokes per split (38-41); (vi) it might be interesting to pinpoint that Katie did 33, 34 and 35 strokes (first split) and 38, 38 and 29 strokes (second and third splits) in the 1500, 800 and 400m events, respectively.

My guess (my bet?) is that the figures I report here might be of no use by the end of the summer. After the Pan Pacs, to be held in late August, we may need to update this post. I hope you enjoyed the analysis though.

By Tiago M. Barbosa that earned a PhD degree in Sport Sciences and holds a faculty position at the Nanyang Technological University, Singapore.

Drills to Ditch: Side kicking and 6-beat switch

Take Home Points on Drills to Ditch
    1. Hip rotation may contribute less to rotation than previous belief
    2. Hip stability is crucial for energy transfer
    3. Reconsider drills that teach hip rotation beyond the degree used in the full stroke
      Many non-scientific beliefs exist in swimming. One form of dogma is the role of hip

      rotation in long axis strokes.  Conventional wisdom says that increasing hip rotation is critical for propulsion, hydrodynamics, and healthy biomechanics.  While most would agree that a completely flat stroke devoid of any rotation is suboptimal, there’s great uncertainty in how much is optimal, both in general terms and for each individual.

      Some factors that may dictate hip rotation include:
      • Individual stroke preferences: Different types of freestyle (Body Roll in Freestyle)
      • Injury patterns: Some swimmers must adjust their strokes to avoid pain, as everyone brings different alignment to the pool.
      • Event: It has been suggested that sprinters require less hip rotation than middle distance and distance swimmers.
      • Kicking patterns: 2 beat versus 6 beat kick may dictate body roll patterns.
      Unfortunately, most data on hip rotation comes from the naked eye and from 2D still and video images.  Unlike land based sports such as baseball, golf, and tennis, there is far less data on swim strokes readily available to the coach.  Still there has been enough research for authors such as Maglischo (2003) to conclude,

      "Rolling the body from side to side is essential to efficient front-crawl and backstroke swimming, although not for the reasons usually espoused.  Body roll does not add to propulsive force, except indirectly."

      In an interview on this site, Dr. Jan Prins noted from research in his own lab (paraphrased):

      "Because water is unstable, stability must come from the hips. Hips are translators of velocity and roll in reaction to movements of the hands and feet. Hip velocity tells us how fast you are going. People assume you roll your body but that is incorrect. Previous biomechanical models were based on fixed resistance (land), but water is an unstable medium. Hip stability allows force transfer initiated by the hands and feet. Roll occurs naturally via arm extension. Don’t try to swim on your side like a fish." 

      Previously, Dr. John had begun a series on drillsto ditch segment focusing on traditional drills that deserve rethinking.  The discussion here begs the question whether drills involving side kicking merit continued use in light of what we know (or don’t know) about hip rotation.  Now, if the purpose of the drill is to improve side kicking (such as out of a wall), then perhaps that is more defensible.  But if the goal is to teach a swimmer to swim on their side mid-pool, the latter justification seems to sit on shakier ground. 

      Two drills coming to mind are side kicking and 6-kick switch on side.  Both drills may have merit for coaching beginners with zero concept of body rotation, but do they have merit for anyone beyond the beginner level (if even for novices?)?  Ultimately, there is no definitive answer, but given what the trends are regarding hip stability, perhaps any attempt to exaggerate hip rotation may infect the overall stroke pattern that we are aiming for. 


      While part of this post is as much theory and conjecture as the drills themselves, it does reflect how much is still unknown in this area.  Anecdotally there seems to a movement away from emphasizing hip rotation for the sake of hip rotation, as many now recognize that more factors come into play.  Ultimately, our drill selection should follow accordingly with changes in knowledge.    

      1. Maglischo, E.  Swimming Fastest.  Human Kinetics.  2003
      Written by Allan Phillips is a certified strength and conditioning specialist (CSCS) and owner of Pike Athletics. He is also an ASCA Level II coach and USA Triathlon coach. Allan is a co-author of the Troubleshooting System and was selected by Dr. Mullen as an assistant editor of the Swimming Science Research Review. He is currently pursuing a Doctorate in Physical Therapy at US Army-Baylor University.