Systematic review and meta-analysis finds acute increases but no long-term changes in hamstring muscle stiffness among athletes, suggesting limited chronic structural adaptation.
Key Points
To systematically review and analyze the acute and long-term training effects of Nordic hamstring exercise on hamstring muscle stiffness in healthy individuals and athletes.
Conducted a systematic search across Embase, Medline, SPORTDiscus, Cochrane CENTRAL, Scopus, and Web of Science databases.
Screened 459 unique records and evaluated study quality using a modified Downs and Black quality assessment tool.
Included 12 studies (10 high quality, 2 low quality) evaluating acute effects (6 studies) or chronic training lasting 6 to 10 weeks (6 studies).
Nordic hamstring exercise acutely and transiently increases hamstring muscle stiffness immediately following a single training session.
Chronic training across 6 to 10 weeks showed no significant effect on hamstring stiffness compared to controls, with a mean difference of −2.25 (95% CI, −5.13 to 0.63; P = 0.13; I² = 80%).