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Dolphin Kicking

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

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

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

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

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

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

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

"Case Study #1

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

Case Study #2

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

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

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

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

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

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

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

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

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

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

What was done

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

Results

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

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

Discussion

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

Practical Implications

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

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

Reference:


  1. Pacholak S, Hochstein S, Rudert A, Brücker C. Unsteady flow phenomena in human undulatory swimming: a numerical approach. Sports Biomech. 2014 Jun;13(2):176-94. PubMed PMID: 25123002.
  2. Marinho DA, Reis VM, Alves FB, Vilas-Boas JP, Machado L, Silva AJ, Rouboa AI. Hydrodynamic drag during gliding in swimming.J Appl Biomech. 2009 Aug;25(3):253-7.
  3. Cohen RC, Cleary PW, Mason BR. Simulations of dolphin kick swimming using smoothed particle hydrodynamics. Hum Mov Sci. 2012 Jun;31(3):604-19. doi: 10.1016/j.humov.2011.06.008. Epub 2011 Aug 12.
  4. von Loebbecke A, Mittal R, Fish F, Mark R. A comparison of the kinematics of the dolphin kick in humans and cetaceans. Hum Mov Sci. 2009 Feb;28(1):99-112. doi: 10.1016/j.humov.2008.07.005. Epub 2008 Nov 4.
  5. von Loebbecke A, Mittal R, Fish F, Mark R. Propulsive efficiency of the underwater dolphin kick in humans. J Biomech Eng. 2009 May;131(5):054504. doi: 10.1115/1.3116150. 
  6. von Loebbecke A, Mittal R, Mark R, Hahn J. A computational method for analysis of underwater dolphin kick hydrodynamics in human swimming. Sports Biomech. 2009 Mar;8(1):60-77. doi: 10.1080/14763140802629982.
  7. B. Gillett Underwater Kicking and Foil Movement Personal communication. 2013 February 24.
  8. M. Russell Dolphin Kicking. USA Swimming. 2012 April 12.
By Dr. G. John Mullen received his Doctorate in Physical Therapy from the University of Southern California and a Bachelor of Science of Health from Purdue University where he swam collegiately. He is the owner of COR, Strength Coach Consultant, Creator of the Swimmer's Shoulder System, and chief editor of the Swimming Science Research Review.

Cammile Adams Discusses Training and Biomechanics

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

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

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

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

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

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

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

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

5) What about your meet preparation behind the block?

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

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

Hasn’t changed at all.

7) What are your goals for 2015 and 2016?

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

Daniel Marinho Discusses Finger Position in Swimming

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

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

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

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

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

3. What did your study look at?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

11. What makes your research different from others?

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

12. Which teachers have most influenced your research?

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

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

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

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

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


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

Interview: Roland Schoeman Discusses Swimming Biomechanics and Training

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

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

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

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

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

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

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

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

5) What do you do for dryland training

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

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

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

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

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

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

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

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

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

10) What are you goals for 2015 and 2016?

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

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

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

12) What are you working biomechanically for your butterfly?

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

Follow @rolandschoeman and Instagram is Roland-Schoeman

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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



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

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

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

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

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

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

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

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

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

Future of Swimming Training

Take Home Points on the Future of Swimming Training:


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

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

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

Future of Swimming Training

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

Biomechanics, Injury Prevention and Coaching

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

Dryland and Recovery

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


Sleep and Recovery

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


Nutrient Levels

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

Summary

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!

Reference
  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: http://www.ncbi.nlm.nih.gov/pubmed/25114741

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. 

References:

  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.