Squatting is a common movement in daily activities, athletic training, rehabilitation programs, and even in the workplace. Identifying the effects of various foot wedges on thigh muscle activity during squatting can help specialists in terms of rehabilitation, injury prevention, physical preparation, and occupational optimization. In this study, systematic literature searches in six electronic databases (Cochrane Library, PubMed, Google Scholar, Web of Science, ScienceDirect, and Scopus) were conducted up to December 2023. Fifteen studies met the inclusion criteria (total n = 269 subjects). The results showed that posterior wedges significantly increased the overall activity of thigh muscles (p < 0.001, 12 studies). No significant change was observed for anterior (p = 0.730, six studies), medial (p = 0.169; three studies), and lateral wedges (p = 0.989, two studies). Compared with a non-wedge condition, the activity of the vastus medialis (p < 0.001, eight studies) was significantly higher using a posterior wedge during squatting, as was the activity of the rectus femoris (p = 0.021, five studies) using the anterior wedge. It seems that thigh muscle activation is modifiable with a change in footwear design, which may be useful during sports training, rehabilitation, or daily work routines.
