Performance Level Differences in Swimming:
Relative Contributions of Strength and Technique
Rod Havriluk, Ph.D.
XIth International Symposium on Biomechanics and Medicine in Swimming
Oslo, Norway, 2010.
The drag equation explains swimming performance as: v ≈ √(F/Cd), where v is swimming velocity, F is force, and Cd is the active drag coefficient. Consistent with this equation, previous research found that v increases with √F (Havriluk, 2004), and that faster swimmers have a lower Cd than slower swimmers (Havriluk, 2003). The purpose of this study was to determine how faster swimmers perform better than slower swimmers due to the relative contributions of strength (F) and technique (Cd), so that coaches can implement the most appropriate interventions for continued improvement.
Male (n=40) and female (n=40) swimmers were tested with Aquanex+Video swimming four trials (one of each stroke) over a 20 m course (e.g. Havriluk, 2003). Underwater video, hand force data, and swim time were collected over the last 10 m of each trial. The Cd was calculated. The swimmers were stratified into faster and slower groups based on the v for each stroke.
Regression analyses found significant (p<.01) curvilinear relationships with v for both F and Cd for all strokes for both genders. The magnitude of the difference between faster and slower swimmers in both F and Cd was calculated as an effect size for all 8 combinations of gender and stroke. In 7 of 8 gender/stroke combinations, the effect size for Cd was greater than for F. The mean effect size was .54σ for the F values and .90σ for the Cd values.
The mean Cd effect size was almost double the F effect size, indicating that the advantage faster swimmers have over slower swimmers is derived more from technique than strength. Coaches can help slower swimmers improve by emphasizing technique instruction and regularly measuring their Cd. Because of the large gains in v that result from small decreases in Cd, even the fastest swimmers can continue to benefit from improving technique. Faster swimmers can also gain a greater advantage from a more effective use of strength. A detailed hand force analysis is necessary to help coaches identify wasted motion and provide options that increase average force to achieve maximum performance potential.
Havriluk, R. (2004). Hand force and swimming velocity. Paper presented at the XVth FINA World Sports Medicine Congress, Indianapolis, IN.
Havriluk, R. (2003). Performance level differences in swimming drag coefficient. Paper presented at the VIIth IOC Olympic World Congress on Sport Sciences, Athens.