Change of Optimum Angle for Torque Production after Repeated Bouts of Maximal Intensity Eccentric Exercises

The purpose of the present study was to evaluate the effect of repeated bouts of maximal intensity eccentric exercise at knee extensors on optimum angle and eccentric exercise-induced muscle damage indicators.
A total of 15 untrained healthy females performed two bouts of maximal intensity eccentric exercises (6 sets*20 repetitions) at knee extensors with the time interval of two weeks. Isometric and concentric extensor torques, optimum torque angles, delayed onset muscle soreness, knee range of motion, and thigh circumference were measured before and immediately, 48 hours, and 5 days after two bouts of eccentric exercises.
Reduction of torques and range of motion, increase in optimum angle, and delayed onset muscle soreness were significant after the first bout of eccentric exercise. After the second bout, reductions in concentric torques and range of motion were less. Optimum angle at the velocity of 60 degree per second was increased and delayed onset muscle soreness was decreased at 48 hours after the second bout compared with that after the first bout (P Eccentric exercise induced muscle damage was evident after the first bout of eccentric exercise. Also, repeated bout effect was observed after the second bout. A change of optimum angle indirectly indicates the roll of cellar mechanisms in adaptation process to eccentric exercises.