I was going to simply tweet this out, but being that the half-life of a tweet is roughly 4.2 minutes, and the fact that there is some really good stuff in here, I'm reposting this interview from SwimmingScience.net.
Ryan Atkinson Breaks Down Dolphin Kicking
1. Please introduce yourself to the readers (how you started in the profession, education, credentials, experience, etc.).
I completed both B.Sc. (2008) and M.Sc. (2010) in Kinesiology at the University of Western Ontario, specializing in sport biomechanics, and am a certified strength and conditioning specialist with the NSCA. Currently, I provide biomechanics and performance analysis support for swimming based out of the Toronto National Training Centre. I am a former swimmer and coached for several years at the club and varsity level before taking my first full time job as a sport biomechanist. While coaching, I also provided strength and conditioning programming and biomechanics consultations and clinics for regional swimming programs. Through the help of my colleagues, I became connected with Swimming Canada’s Senior Biomechanist, Dr Allan Wrigley. I hadn’t been exposed to that career path before, but it appealed to me and I was fortunate to be offered a job as a biomechanist for winter sport programs, supporting freestyle skiing and snowboarding. While it was a departure from swimming, I found that it really challenged my assumptions from a coaching perspective and has allowed me to better analyze swimming in an unbiased way.
2. You recently published an article on underwater dolphin kicking (Importance ofsagittal kick symmetry for underwater dolphin kick performance also see Brief Swimming Review Edition 16), could you briefly discuss what is well known about UDK?
When performed well, underwater dolphin kicking (UDK) can be faster than surface swimming. This is because surface swimming speeds are limited to a length-determined “hull speed” of each individual swimmer, whereas there is no upper-limit for speed underwater due to the absence of wave resistance.
From a technical standpoint, it has been well established that human swimmers are more effective at the downkick phase than the upkick phase. Humans are somewhat limited in their ability to perform the upkick phase due to anatomical restrictions about the hip, knee and ankle joints; however, swimmers with hypermobile knee and ankle joints that allow them to hyperextend beyond 180 degrees have an anatomical advantage that may allow them to better perform the UDK.
3. What are some of the biggest questions remaining about UDK?
It is important to know how to optimize UDK technique for an individual, based on various anthropometric, strength and flexibility parameters. Much of the recent research on UDK has relied on computer simulations to evaluate technique; however, these studies have been limited in scope and applicability to the general swimming public. Thus, training studies are required to test findings from simulations. For example, it has been shown through computer simulations that swimmers with limited passive plantarflexion range of motion are able to improve UDK performance by increasing their ankle flexibility, yet this has not been confirmed directly through practical research.
Another area that requires immediate attention is injury risk associated with increased UDK training. In certain populations, UDK training has been thought to increase the incidence of low-back pain. Research is required to determine which movements specifically are related to low-back pain, and if UDK teaching can be improved so that less stress is placed on the lower-back without compromising performance.
4. What did your study specifically look at?
We investigated the mechanics of the UDK across a range of swimmers, including varsity swimmers and Olympians, to determine how symmetry between the downkick and upkick phases is related to performance. Using a twelve-segment model, we evaluated various kinematic parameters during downkick and upkick phases, including joint marker paths, joint angles, vertical toe velocities, and whole body displacements and horizontal velocities.
5. What were your main findings?
Symmetry between downkick and upkick phases is highly related to high UDK velocity, and swimmers who are more effective at the upkick phase tend to have a faster UDK velocity. Specific movements that are highly related to faster UDK are: greater peak vertical toe velocity during the upkick phase, reduced upkick duration, and less knee flexion at the end of the upkick/start of the downkick.
6. How should coaches use this information for teaching beginners UDK?
It is evident that novice swimmers have more difficulty performing the upkick phase than the downkick phase. Coaches should emphasize teaching the upkick phase of the dolphin kick, specifically recruiting the muscles of the posterior chain without excessive lower back flexion or knee flexion. Training the kick on the side will allow the swimmers to focus on kicking in both directions. Larger amplitude kicks are more appropriate for this stage of learning than high frequency kicks. This can be taught on the land as well by performing single or double leg lifts in a prone, streamlined position, paying close attention to recruiting the gluteal muscles for leg lifts rather than the lower back.
7. What about more advanced swimmers, how should UDK biomechanics be advanced?
Coaches of advanced swimmers should focus on reducing the amplitude of the UDK, especially at the upper body segments (torso, head and arms) and increasing kick frequency. Particular attention should be placed on maximizing toe velocity during the upkick and limiting the duration of the upkick. Similarly with beginners, swimmers should be encouraged to recruit the muscles of the posterior chain without excessive lower back flexion or knee flexion. This can be advanced on the land by performing single leg lifts in a plank position, paying close attention to recruiting the gluteal muscles for leg lifts and keeping the hips level.
8. You note exceptional thoracic spine, knee, and ankle mobility as some elite characteristics. Do you feel these characteristics are innate or developed?
Both. Some humans are gifted with exceptionally mobile joints that allow them to move through extra-ordinary ranges of motion with relative ease. Some of this mobility can be trained through targeted stretching and mobility exercises instructed by a qualified coach or health care professional, especially at the thoracic spine, ankles and hips. Prior to engaging in this type of training, athletes should be screened to determine the source of the athletes’ limitations and what, if any, training or treatment modalities may be effective in improving their mobility [perhaps the Swimming Troubleshooting System].
9. Were there any outliers in your study (some elite kickers who didn't have the same characteristics)?
The fastest swimmers, based on FINA point scores, weren’t necessarily the fastest UDK performers. Furthermore, several of the high level UDK performers had larger velocity fluctuations than expected. This can be partly explained by the greater resistance experienced at higher velocities, but may also indicate that these swimmers have room to improve. Conversely, the swimmer with the apparently “best” UDK technique (most stable velocity) wasn’t the fastest at UDK, but did have the highest body length-normalized velocity and ranked much higher among his peers in UDK velocity compared with his overall swim performance.
10. Do you think UDK is faster prone or on the side?
Swimmers will be fastest in the position that they train in most often at high speeds. Either position has a tradeoff; when kicking in a supine or prone position at shallower depths (less than one-half metre) some energy from the kick is lost to the creation of surface waves (observed as ripples on the surface); when kicking on the side, swimmers may have difficulty staying symmetrical in the frontal plane due to their natural buoyancy torque, which would inhibit their maximal force production. Ultimately, UDK position should be part of a complete start or turn strategy, so factors such as push-off position and breakout timing need to be considered. A useful strategy for freestyle and butterfly swimmers is to push-off on the side, and to begin kicking on the side and use the kick to facilitate a transition to the front without any sudden twists or changes of direction.
11. Do you think there will be any big progressions in UDK, if so what do you predict?
Several of the best UDK performers in the world are anomalies, in that they achieve success mostly due to incredible anatomical or strength advantages rather than superior technique. Improved knowledge of UDK technique by coaches and trainers, and increased emphasis during training will lead to widespread improvements in UDK performance and strategy. A major shift will occur when freestyle sprint swimmers accept that they can be faster remaining underwater to 15m, and will extend their start and turn breakout distances to nearly 15m underwater during 50m and 100m events.
12. What research or projects are you currently working on or should we look from you in the future?
Recently, I collaborated with regional research partners on a swimming start study, looking at the effect of body lean on start performance. I am currently not involved in any research projects, but am working on applying research methods to develop better tracking, monitoring, and evaluation criteria and methods for starts, turn and underwater skills. This includes basic coaching resources, such as benchmarks and checklists, and more sophisticated biomechanical methods using instrumented starting blocks and accelerometers.
Follow Ryan on Twitter @Swimmingsmarter