Ribeiro, L. F., Lima, M. C., & Gobatto, C. A. (2008). Changes in physiological and stroking parameters during interval swims at the slope of the d-t relationship. Journal of Science and Medicine in Sport, December 30, [E-publication].

"The slope of the distance-time relationship from maximal 200 and 400 m bouts (S(200-400)) has been increasingly employed for setting training intensities in swimming. However, physiological and mechanical responses at this speed are poorly understood." This study investigated blood lactate, heart rate, stroke rate, stroke length, and rating of perceived exertion responses to an interval swimming set at S(200-400) in trained swimmers (N = 12) in a 50-m pool. Ss performed maximal 200 and 400 m crawl trials for S(200-400) determination. Thereafter, Ss were instructed to perform an interval set of 5 x 400 m at the determined speed with 1.5 minutes rest between repetitions.

Three Ss could not complete the set. For the remaining Ss, significant increases in blood lactate, stroke rate, heart rate, and ratings of perceived exertion were observed through the interval set. Stroke length decreased significantly from the first to the fifth repetition.

Implication. These results suggest that interval swimming at S(200-400) represents an intense physiological, mechanical, and perceptual stimulus that can be sustained for a prolonged period by most swimmers.

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