The squat is a notoriously complex exercise both in terms of its biomechanics and its neuromuscular demands. Given that the resisted portion of the movement, the ascent, involves concentric actions of muscle groups with antagonist functions (e.g. the quadriceps and the hamstrings at the knee and the hip) [
51], perfecting the squat requires much practice which fine-tunes the timing and the extent to which different contributing muscles are engaged. Considering this complexity, it is of no surprise that a sticking point has been repeatedly observed in the squat in numerous studies. Indeed, in the academic literature, the phenomenon of the sticking point was first reported and studied in the squat [
52]. In particular, McLaughlin et al. [
52] examined kinematic characteristics of the squat performed by highly skilled powerlifters, and observed that the sticking point across the studied sample occurred at approximately a thigh angle relative to the ground of
\(30^\circ\). What is more, they observed a remarkable uniformity across the sample in this regard, as witnessed by the standard deviation of the angle of only
\(\pm 2^\circ\). A virtually identical finding was recently reported by Hales et al. [
53], who observed the sticking point at a thigh angle of
\(32^\circ \pm 2.0^\circ\) in a sample of competitive powerlifters of varying skill levels. In this study, the authors also measured the positions of other body segments. Of particular importance in the context of the present paper were the findings that both the trunk and shank angles relative to the ground exhibited much greater variation between different lifters, of
\(\pm 6.3^\circ\) and
\(\pm 7.3^\circ\) respectively, which highlights the interaction between the squatting style adopted by an athlete, the athlete’s biomechanics, and the point in the lift at which the athlete is most likely to exhibit a sticking point. This interaction was examined in depth by Escamilla et al. [
44], who also performed a stratification of the studied sample into three groups by their stance width (normalised by shoulder width): narrow, medium, and wide. The first interesting finding of this work is the much greater thigh angle at the sticking point than that reported by McLaughlin et al. [
52] and Hales et al. [
53]: approximately
\(49^\circ\). Also contrasting the findings summarised before, Escamilla et al. observed a significantly greater variability of the sticking point thigh angle across lifters of
\(\pm (5^\circ\)–
\(6)^\circ\). Particularly surprising was that much greater variation was found within the three groups (narrow, medium, and wide) than across groups (approximately
\(\pm 2^\circ\)). Considering that the parameters of the studies by Escamilla et al. and McLaughlin et al. were very similar (they both used highly skilled powerlifters who wore one-piece squatting suits), an insight which would explain this discrepancy has yet to emerge; indeed, Escamilla et al. did not discuss this aspect of their findings.
Interestingly, in comparison with the bench press, studies of electromyographic muscle activity in the squat in the context of the sticking point are lacking. One of the few studies in this realm is that by van den Tillar et al. [
54]. In contrast to the portion of the lift surrounding the sticking point in the bench press wherein significant changes (decreases for some and increases for others, see Sect.
3.1) to EMG muscle activity were observed, no similar trends were noticed in the squat. The rectus femoris and vastus lateralis, both significantly active in the squat, exhibited a steady decrease in activity throughout the lift (as previously reported by Escamilla et al. [
55] and McCow and Melrose [
56]), while biceps femoris, a lesser contributor, showed a slight and steady increase. The only muscle which did show some (albeit slight) change at the sticking point was the vastus medialis, the most activated muscle in the lift, which demonstrated a transient increase in activity. However, the authors’ statistical analysis as well as previous findings recorded in the literature [
55,
56] suggest that this was a chance occurrence rather than a genuine pattern.