Differences in activation amplitude between semitendinosus and biceps femoris during hamstring exercises: A systematic and critical review with meta-analysis.

The aim of this systematic review and meta-analysis was to compare the amplitude of electromyographic (EMG) recordings for the semitendinosus (ST) and biceps femoris (BF) muscles during selected exercises. Searches were conducted in PubMed, Web of Science, and Scopus databases up to 31 August 2024. Included studies focused on healthy adults, reported ST and BF muscle activation during hamstring strengthening exercises, and presented outcomes as a percentage of maximal voluntary contraction. The analysis included 619 participants. No overall significant difference in activation was observed between ST and BF across knee- and hip-based exercises. However, EMG amplitude was greater in ST during the Nordic hamstring exercise (Standardized mean difference, SMD: -0.33, p = 0.01), whereas EMG amplitude was greater in BF during prone-lying curls (SMD: 0.94, p = 0.0076). Among hip-based exercises, EMG amplitude was greater in BF during back extensions (SMD: 0.34, p = 0.0092), whereas EMG amplitude was greater in ST during kettlebell swings (SMD: -0.59, p = 0.0007). Nonetheless, the variability in the methods used to record and analyze EMG as well as the properties of the signal itself make it difficult to reach firm conclusions on whether specific exercises can preferentially recruit ether ST or BF.