The purpose of this investigation was to determine whether the concept of the critical power could be applied to competitive swimming by using critical swimming velocity (CV) as determined both in the swimming flume (CV-flume) and in the normal swimming pool (CV-pool) and could be utilized as a practical index for assessing swimmer's endurance performance. CV defined as the swimming velocity which could be theoretically maintained and continued for a very long time without exhaustion was expressed as the slope of a regression line between swimming distance (D) and its duration (T) obtained at various swimming velocities. Eight highly trained swimmers were instructed to swim until onset of the fatigue at predetermined four swimming velocity levels using the swimming flume and the four different swimming distances at maximal effort using the swimming pool. In the results of CV-flume and CV-pool, the regression relations between D and T were expressed in the general form, D=a+b×T, with r² showing higher than 0.998 (P< 0.001), respectively. These results indicate extremely good linearity regardless of the flume or the pool.
　Furthermore, maximal oxygen uptake (Vo₂max) during incremental exercise test, swimming velocity corresponding 4 mM of blood lactate concentration (V-OBLA) and mean velocity in the 400 m free-style (V-400) were measured on each subject. Significant correlations were found between CV-pool and CV-flume (r= 0.834, P< 0.01), CV-pool and V-400 (r= 0.996, P< 0.01), V-OBLA and CV-pool (r= 0.895, P< 0.01), V-OBLA and CV-flume (r= 0.856, P< 0.01), and CV-flume and V-400 (r= 0.823, P< 0.05). These data suggest that CV can be determined by relationship between swimming distance and its time (record) measured not only in the flume but also in the normal swimming pool, and CV can be adopted as an index for assessing the endurance performance.

DESCENTE SPORTS SCIENCE Vol.13/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE