Fluctuations of isometric force after eccentric exercise of the elbow flexors of young, middle-aged, and old men

This study compared force fluctuations during isometric contraction following eccentric exercise of the elbow flexors between young, middle-aged, and old subjects. Ten young (20 +/- 2.0 years), 12 middle-aged (48 +/- 7.3 years), and 10 old (71 +/- 4.1 years) men performed six sets of five eccentric actions of the elbow flexors using a dumbbell weighing 40% of maximal voluntary isometric contraction strength (MVC) at an elbow joint angle of 90 degrees (1.57 rad). MVC was measured before, immediately after, and 1-5 days following exercise, and the force fluctuations were assessed at 30, 50, and 80% of the corresponding time point MVC using coefficient of variation (CV) of force data collected at a frequency of 100 Hz for 4 s. Changes in MVC and CV over time were compared between groups by a two-way repeated measures ANOVA. Changes in MVC following exercise were not significantly different between the young and middle-aged groups, but the old group showed significantly (P < 0.05) smaller decreases in MVC compared with other groups. CV increased significantly (P < 0.05) only immediately after exercise without a significant difference among the three intensities, and no significant differences between groups were evident. It was concluded that force fluctuations during submaximal isometric tasks after eccentric exercise were not affected by age.