THE EFFECTS OF CONCENTRIC, ECCENTRIC AND COMBINED CONCENTRIC AND ECCENTRIC MUSCLE ACTIONS ON SHORT-TERM FATIGUE

205 Many studies have shown the effects of eccentric muscle actions on eccentric force and long-term concentric force generation, however little work has been done examining the effects of eccentric or combined concentric-eccentric muscle actions on short-term concentric force generation. Nine healthy men performed three bench press workouts, separated by at least one week; 1) 3 sets of concentric muscle actions only 2) 3 sets of eccentric muscle actions only and 3) 3 sets of combined concentric/eccentric muscle actions. The total number of muscle actions was kept constant among the three workouts. Peak force was measured for all of the concentric and eccentric workouts repetitions. Peak concentric force was determined as the peak force during the first repetition of the concentric workout. Concentric force generation was measured 1 minute after the completion of the final set and 10 minutes after the final set. Eccentric force was greater than concentric force for all repetitions and showed very little decline in force when compared to the concentric workout (11% decline in force from first eccentric repetition to the last compared to 25% decline in force from the first concentric repetition to the last repetition). There were no significant differences among the workouts after 1 minute of rest (concentric: 1,042 N, eccentric: 1,052N and coupled concentric and eccentrics: 1,006N) Ten minutes post-exercise the eccentric workout had shown no significant increase in force from the 1 minute timepoint (1,081N), the concentric group had recovered so that there was no significant difference between the 10 minute post-workout (1,178N) and the pre-workout force generation, and the combined concentric eccentric workout had significant improvement from the 1 minute post-workout value, but had not fully recovered to the pre-training value (1,110N). These results demonstrate that the mechanisms of fatigue are different for concentric and eccentric muscle actions, and that the fatigue due to these different types of muscle actions is dose dependent and may be cumulative between different types of muscle actions.