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 .
Anatomical and mechanical changes following repetitive eccentric exertions.
BACKGROUND Submaximal eccentric exertions occur occupationally when rapidly rising tool-generated forces exceed the operator 's capacity to react against them . The purpose of this study was to investigate the effects of short duration repetitive submaximal eccentric forearm exertions at levels comparable to industrial power h and tool use on dynamic mechanical properties ( stiffness , effective mass and damping ) and on forearm edema . METHODS This study investigated changes following short term repetitive submaximal eccentric exertions comparable to occupational levels . Eight male participants  exercised eccentrically for 30 min at 50 % of isometric maximum voluntary contraction forearm supination in a posture and loading similar to power h and tool use in the workplace . Dynamic mechanical properties ( stiffness , effective mass and damping ) of the upper limb were measured before , immediately following , and daily for three days after the activity . An MRI scan to assess edema was also performed for five of the participants before , on day one and day three following the activity . FINDINGS Mechanical stiffness decreased 51 % ( P < 0.05 ) and effective mass decreased 43 % ( P = 0.052 ) immediately following eccentric exercise .  Average isometric strength also decreased 42 % immediately following exercise ( P < 0.01 ) and pain persisted for two days . The recovery of static strength however was not correlated with changes in mechanical stiffness ( r = 0.56 ) or effective mass ( r = 0.30 ) . The exercised arms had a 360 % increase ( P < 0.01 ) in supinator-extensor T(2 ) relaxation time difference , a quantifiable measure of edema , one day after exercise while the non-exercised arms had no significant changes . INTERPRETATION Changes in both T(2 ) relaxation time , indicative of edema , and forearm mechanical properties , were observed following short duration submaximal repetitive exercise . If similar changes in dynamic mechanical properties of the upper extremity occur following repetitive submaximal eccentric activity in the workplace , they could negatively impact the ability of the arm to react to rapid forceful loading during repetitive industrial work activities and increase mechanical loading of the upper limb
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 .