Neuromuscular fatigue and recovery in male and female athletes during heavy resistance exercise.

To examine neuromuscular fatigue and recovery ten male and nine female athletes performed a strenuous heavy resistance exercise protocol. The subjects strained their leg extensor muscles with the same maximal relative intensity by performing one maximal squat-lift with a load of 100% of 1 RM (one repetition maximum) 20 times (20 x 1 x 100%). Maximal voluntary neural activation (integrated EMG), maximal bilateral isometric force, force-time and relaxation-time curves of the leg extensor muscles were measured before and immediately after the exercise session as well as after resting for 1 hour, 2 hours, 1 day and 2 days. The session resulted in considerable gradual decreases in maximal force in the males by 24.1 +/- 14.4% (p < 0.001) and in the females by 20.5 +/- 11.8% (p < 0.01) as recorded immediately after the session. Significant (p < 0.05-0.01) decreases also took place in the males in the maximal IEMGs of the exercised muscles, while the corresponding decreases in the females were minor. The force-time curve shifted greatly to the right both in the males (p < 0.001) and in the females (p < 0.01) but the average change of 27.8 +/- 13.8% in the males was greater (p < 0.05) than that of 18.7 +/- 8.3% recorded for the females. The time of force relaxation lengthened (p < 0.05) in both groups. Maximal force recovered during the first hour of rest was more (p < 0.05) in the females than in the males but thereafter the recovery took place gradually in both groups to the same degree.(ABSTRACT TRUNCATED AT 250 WORDS)