Tor, E., Pease, D. L., & Ball, K. A. (2015). How does drag affect the underwater phase of a swimming start? Journal of Applied Biomechanics, 31(1), 8-12.

During the underwater phase of the swimming start drag forces are constantly acting to slow the swimmer down. This study attempted to quantify total drag force as well as the specific contribution of wave drag during the underwater phase of the swimming start. Swimmers were towed at three different depths (surface, 0.5 m, 1.0 m) at four speeds (1.6, 1.9, 2.0, 2.5 m/s) (12 conditions). Wave drag and total drag were measured for each trial. Mixed modeling and plots were then used to determine the relationships between each towing condition and the amount of drag acting on the swimmer.

As depth increased and regardless of speed, total drag decreased (-19.7% at 0.5 m and -23.8% at 1.0 m). This phenomenon is largely due to a significant reduction in wave drag as the swimmers traveled at greater depth.

Implication. It is recommended that swimmers travel at least 0.5 m below the surface to avoid excessive wave-drag forces. Swimmers should also perform efficient breakouts when transitioning into free swimming to reduce time spent just below the surface where drag values are their highest.

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