By Dr. G. John Mullen, PT, DPT, CSCS of Swimming Science, Owner of COR PT , Creator of Swimmer's Shoulder System, Swimming Science Research Review, Swimming Troubleshooting System , and Mobility for Swimmers System , Swimming World correspondent
Courtesy of: Christopher Rattray
Courtesy of: Christopher Rattray
SANTA CLARA, California, February 7. THE backstroke start is progressing rapidly. Not long ago, swimmers grabbed on the gutter with their feet low in the water, making it difficult to get their body out of the water. Now, swimmers get their hips high and lock their feet high on the wall. Yet, what condition is ideal for most swimmers? Luckily, there is great research on the topic of foot position and the backstroke start, specifically for foot position.
Backstroke Start Biomechanics
De Jesus (2011) broadly looked the effective backstroke start strategies and had six male high-level swimmers performed different starting positions during backstroke to identify features that create the fastest start to 15m. These swimmers were within 87.58% +/-3.32% of the 100m backstroke long course world record. Feet positions comprised of parallel and entirely submerged (BSFI) and parallel and above water (BSFE) and all swimmers had mastered both start variations. These swimmers performed two sets of four maximal intensity backstroke starts for each variation. Dual video analysis, underwater extension platform, handgrip load cell, and electromyography (EMG) recording of rectus femoris and gastrocnemius medialis were used to analyze the starts. Swimmers swam with the Speedo Fastskin swimsuit.
This study found the following significantly important to start time:
-- Center of mass velocity at glide phase
-- Horizontal impulse at hands-off and take-off
Moderate association with start time:
-- Center of mass vertical displacement and velocity at take-off
-- Center of mass horizontal velocity at first water touch, entry,
-- Take-off angle
-- EMG activity of gastrocnemius and rectus femoris at take off
-- EMG activity of rectus during glide phase
No significance to start time:
-- Center of mass resultant displacement and velocity at take off
-- Entry angle
Foot Position on the Backstroke Start
In another study lead by de Jesus (2013), six elite male swimmers (about 22.5 years old; 87.58% of the male 100m backstroke world record) performed two sets of four maximal 15m bouts with the feet either emerged (above) or immersed (below) the water. The starts were videotaped and analyzed.
The center-of-mass was more horizontal during the feet immersed condition. Feet immersed also increased the horizontal velocity at the hands-off instant.
"Backstroke start with feet immersed displayed greater center-of-mass horizontal starting position (and) center-of-mass horizontal velocity at hands-off and take-off angle. Backstroke start with feet emerged showed greater wall contact time, center-of-mass horizontal and downward vertical velocity at take-off, lower limbs horizontal impulse, and center-of-mass downward vertical velocity during flight phase. Backstroke start with feet immersed and emerged displayed similar center-of-mass horizontal water reach, back arc angle and 5m starting time" (Jesus 2013)
Although kinematic and kinetic differences occurred between these two conditions, the time to 5 meters was not significantly different. It appears the feet emerged condition allows greater force generation, where the immersed conditions allows a shorter time of first upper limbs maximal force.
Four Keys for the Backstroke Start
Since the time to 5 meters was not significantly different between conditions, one could theoretically use either style successfully. However, swimmers should strive to:
-- Move your body fast off the wall!
-- Get your hips high off the wall.
-- Extend your hips quickly.
-- Get streamlined during the glide phase!
Center of mass velocity at glide phase and entry phase is important for starts with the feet emerged. Center of mass velocity at glide phase and horizontal impulse at take-off benefits start with the feet immersed in the water. Swimmers should focus on creating greater horizontal velocity while entering the water with body position that minimizes hydrodynamic drag forces. Greater contractions of the rectus femoris at glide phase can be detrimental if they lead to exaggerated kick amplitude. Start times can be hindered by greater take-off angles and a higher center off horizontal mass approximation during a start position with feet above water. The disadvantage occurs because the greater angle and approximation to the wall creates a longer race for the swimmer.
Future of Backstroke Starts
With Nick Thoman breaking the American record in the 100-yard back , one must wonder what the future holds for backstroke swims. In a recent interview, Dr. Fernandes notes:
"[w]e are certain that those performances will appear in a short time particularly if during the training process the start performance can dispose of a little bit more of attention. In fact, the actual best female backstroke swimmers have around 7.5 (seconds) at the 15m mark and 58.3 (seconds) on the 100m backstroke race, and, as the best women's 15 m starting time is under 7.0 (seconds) (recently recorded at the 50m event), it is evident that some amazing performances will come soon."
Combine this with the new addition of the Omega foot platforms, we are certain to see some fast backstroke swims in the future! Any predictions? I think a 57 in the women's 100 backstroke is around the corner!
If you enjoyed this review, consider purchasing the Swimming Science Research Review from the month of January for only $10. This edition provides a comprehensive review of all the research on start.
1. de Jesus K, de Jesus K, Figueiredo P, Gon?alves P, Pereira SM, Vilas-Boas JP, Fernandes RJ. Backstroke start kinematic and kinetic changes due to different feet positioning. J Sports Sci. 2013;31(15):1665-75. doi: 10.1080/02640414.2013.794298. Epub 2013 May 20.
2. de Jesus K, de Jesus K, Figueiredo P, Gon?alves P, Pereira SM, Vilas-Boas JP, Fernandes RJ.Biomechanical Analysis of Backstroke. Int J Sports Med 2011; 32:546-551.
3. Takeda T, Itoi O, Takagi H, Tsubakimoto S. Kinematic analysis of the backstroke start: differences between backstroke specialists and non-specialists. J Sports Sci. 2013 Oct 9. [Epub ahead of print]
By Dr. G. John Mullen received his Doctorate in Physical Therapy from the University of Southern California and a Bachelor of Science of Health from Purdue University. He is the owner of COR PT, strength and conditioning consultant, creator of the Swimmer's Shoulder System, and chief editor of the Swimming Science Research Review.