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 .
Subcellular movement and expression of HSP27, alphaB-crystallin, and HSP70 after two bouts of eccentric exercise in humans.
The aims of this study were to investigate the sarcomeric accumulation and expression of heat shock proteins ( HSPs ) after two bouts of maximal eccentric exercise .  Twenty-four subjects performed two bouts of 70 maximal voluntary eccentric actions using the elbow flexors in one arm . The bouts were separated by 3 wk . The changes in concentric ( 60 degrees/s ) and isometric ( 90 degrees ) force-generating capacity were monitored for 9 days after each bout , and biopsies were taken 1 and 48 h and 4 and 7 days after bout 1 and 1 and 48 h after bout 2 . The content of HSP27 , alphaB-crystallin , HSP70 , and desmin in the cytosolic and cytoskeleton/myofibrillar fractions of homogenized muscle sample s was determined by immunoassays , and the cellular and subcellular localization of the HSPs in the myofibrillar structure was analyzed by conventional and confocal immunofluorescence microscopy and quantitative electron microscopy . The force-generating capacity was reduced by approximately 50 % and did not recover completely during the 3 wk following bout 1 . After bout 2 , the subjects recovered within 4 days . The HSP levels increased in the cytosolic fraction after bout 1 , especially HSP70 ( approximately 300 % 2 - 7 days after exercise ) . Increased levels of HSP27 , alphaB-crystallin , and HSP70 were found in the cytoskeletal/myofibrillar fraction after both bouts , despite reduced damage after bout 2 . At the ultrastructural level , HSP27 and alphaB-crystallin accumulated in Z-disks , in intermediate desmin-like structures ( alphaB-crystallin ) , and in areas of myofibrillar disruption . In conclusion , HSP27 and alphaB-crystallin accumulated in myofibrillar structures , especially in the Z-disks and the intermediate structures ( desmin ) . The function of the small HSPs is possibly to stabilize and protect the myofibrillar structures during and after unaccustomed eccentric exercise . The large amount of HSP27 , alphaB-crystallin , and HSP70 in the cytoskeletal/myofibrillar fraction after a repeated bout of exercise suggests a protective role as part of the repeated-bout effect
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 .