Effect of Individual Difference in Maximal Strength and Number of Repetitions at Relative Intensity on Muscle Oxygenation During Knee Extension Exercise

Abstract

The purpose of this study was to investigate muscle oxygenation during intense dynamic knee extension exercise, after a classification into four groups based on the relative merit of one repetition maximum (1RM) and the total number of repetitions loaded at 90%, 70% and 50% of 1RM (N_total). Thirty six male university undergraduate and graduate students with experience in various sports participated in the study. Subjects performed knee extension exercise at 1RM and a number of repetitions loaded at 90%, 70% and 50% of 1RM. Subjects were divided into four groups based on the results of 1RM and N_total (SN group : 1RM-high / N_total-high, Sn group : 1RM-high / N_total-low, sN group : 1RM-low / N_total-high, sn group : 1RM-low / N_total-low). Muscle oxygenation on the vastus lateralis muscle was measured during the repetition exercises. The minimum value and rate of decrease at onset of repetition exercise (4-9 seconds after the start of exercise) were calculated to estimate muscle oxygenation. The major findings were: (1) The relative merit of 1RM and number of repetitions at relative intensity affected the muscle oxygenation during repetition exercise. (2) A significant negative correlation between N_total and rate of decrease of muscle oxygenation was observed with loads at 70% and 50% 1RM, but not at 90% 1RM. These results suggest that it is important to focus on the improvement of aerobic capacityin resistance training to increase the number of repetitions at relative intensity.