ABSTRACT

　The purpose of this study was to compare changes in muscle strength and hypertrophy after low-intensity torque-matched isometric training at long muscle length （LL） and short muscle length （SL） . Thirty healthy young volunteers （16 men and 14 women; 25.2 ± 3.4 years） were assigned either to LL group or SL group, which performed isometric knee flexion training at 90ﾟ hip flexion and 30ﾟknee flexion or 90ﾟhip and knee flexion, respectively. The training program consisted of 30% of maximal voluntary contraction （MVC） with 5 sets of 20 repetitions of 5-s isometric contraction. Muscle cross-sectional area of the hamstrings and the MVC torque at 30ﾟand 90ﾟknee flexion were measured before and after 8-week training intervention. Passive torque was calculated from the knee flexion torque at rest. Active torque was calculated by subtracting passive torque from the total torque generated during training. There was no between-group difference in the total torque during training （LL group,22.2 ± 8.1 Nm; SL group, 28.2 ± 11.2 Nm） . However, the active torque generated by muscle contraction during training was significantly lower in the LL group than SL group（ LL group, 10.1 ± 6.8 Nm; SL group, 28.2 ± 11.2 Nm） . The cross-sectional area and the MVC torque at 30ﾟknee flexion significantly increased after intervention regardless of the groups. The MVC torque at 90ﾟknee flexion significantly increased after intervention in both groups, and greater increase was observed in the SL group. These results suggest that low-intensity isometric training at LL can induce similar muscle hypertrophy and strengthening as that at SL, even in cases where active torque production is lower than that at SL.

DECENTE SPORTS SCIENCE Vol.42/The DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE