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 .
Skeletal muscle collagen content in humans after high-force eccentric contractions.
The purpose of this study was to investigate the effects of high-force eccentric muscle contractions on collagen remodeling and on circulating levels of matrix metalloproteinases ( MMP ) and tissue inhibitors of metalloproteinases ( TIMP ) in humans . Nine volunteers [ 5 men and 4 women , mean age 23 ( SD 4 ) yr ] each performed a bout of  100 maximum voluntary eccentric contractions of the knee extensors . Muscle biopsies were taken before exercise and on days 4 and 22 afterward . Image analysis of stained tissue sections was used to quantify endomysial collagen staining intensity . Maximum voluntary contractile isometric force was recorded preexercise and on days 1 , 2 , 3 , 4 , 8 , 11 , and 14 postexercise . Venipuncture blood sample s were also drawn on these days for measurement of serum creatine kinase activity and concentrations of MMP-9 , TIMP-1 , TIMP-2 , and the MMP-2/TIMP-2 complex . Maximum voluntary contractile force declined by 39 + /- 23 % ( mean + /- SD ) on day 2 postexercise and recovered thereafter . Serum creatine kinase activity peaked on day 4 postexercise ( P < 0.01 ) . Collagen type IV staining intensity increased significantly on day 22 postexercise to 126 + /- 29 % ( mean + /- SD ) of preexercise values ( P < 0.05 ) . Serum MMP-9 levels increased on day 8 postexercise ( P < 0.01 ) , and serum TIMP-1 was also significantly elevated on days 1 , 2 , 3 , 4 , and 14 postexercise ( P < 0.05 ) . These results suggest that a single bout of eccentric muscle contractions results in remodeling of endomysial type IV collagen , possibly via the MMP pathway
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 .