Conclusion Overall , our findings do not support the presence of a secondary loss of strength following an acute muscle injury , and strongly suggest that strength , on average , recovers steadily over the first 3 days post-injury
Background An immediate loss of strength follows virtually all types of muscle injury but there is debate whether the initial strength loss is maximal or if a secondary loss of strength occurs during the first 3 days post-injury .
Objective The objective of this analysis was to conduct a systematic review and meta- analysis of the research literature to determine if a secondary loss of strength occurs after an injurious initiating event .
Electromyographic analysis of exercise resulting in symptoms of muscle damage
Surface  electromyographic ( EMG ) signals were recorded from the hamstring muscles during six sets of  submaximal isokinetic ( 2.6 rad s -1 ) eccentric ( 11 men , 9 women )  or concentric ( 6 men , 4 women )  contractions . The EMG per unit torque increased during eccentric ( P < 0.01 ) but not during concentric exercise . Similarly , the median frequency increased during eccentric ( P < 0.01 ) but not during concentric exercise . The EMG per unit torque was lower for submaximal eccentric than maximum isometric contractions ( P < 0.001 ) , and lower for submaximal concentric than maximum isometric contractions ( P < 0.01 ) . The EMG per unit torque was lower for eccentric than concentric contractions ( P < 0.05 ) . The median frequency was higher for submaximal eccentric than maximum isometric contractions ( P < 0.001 ) ; it was similar , however , between submaximal concentric and maximum isometric contractions ( P = 0.07 ) . Eccentric exercise result ed in significant isometric strength loss ( P < 0.01 ) , pain ( P < 0.01 ) and muscle tenderness ( P < 0.05 ) . The greatest strength loss was seen 1 day after eccentric exercise , while the most severe pain and muscle tenderness occurred 2 days after eccentric exercise . A lower EMG per unit torque is consistent with the selective recruitment of a small number of motor units during eccentric exercise . A higher median frequency during eccentric contractions may be explained by selective recruitment of fast-twitch motor units . The present results are consistent with the theory that muscle damage results from excessive stress on a small number of active fibres during eccentric contractions
Conclusion Overall , our findings do not support the presence of a secondary loss of strength following an acute muscle injury , and strongly suggest that strength , on average , recovers steadily over the first 3 days post-injury
Background An immediate loss of strength follows virtually all types of muscle injury but there is debate whether the initial strength loss is maximal or if a secondary loss of strength occurs during the first 3 days post-injury .
Objective The objective of this analysis was to conduct a systematic review and meta- analysis of the research literature to determine if a secondary loss of strength occurs after an injurious initiating event .