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. The present findings suggest that strenuous heavy resistance loading may result in considerable acute fatigue in the neuromuscular system leading not only to the decreased force production capacity of the muscles but also to a decrease in the voluntary neural activation of the exercised muscles. In males neuromuscular fatigue during strenuous loading may be greater and acute recovery from fatigue slower than in females.