# The Use of Free Weight Squats in Sports: A Narrative Review--Terminology and Biomechanics
## 4 Defining Squat Depth by Knee Angle
Full squat: A full squat, or deep squat as it is sometimes termed, is classified as being performed until a depth where a 40-45\({}^{\circ}\) internal knee angle is achieved [2; 45; 66; 74]. Full squats can be performed with either the high bar back squat or the front squat. Typically, the front squat requires the athlete to go into a deeper squat position and will result in a substantially smaller knee angle and a more upright trunk position when compared to the high bar back squat [2]. Conversely, the low bar back squat typically does not allow for as great a depth to be performed as in the front squat; because of the posterior shifting of the hip and forward trunk lean typically noted in this movement, only a \(\approx\)68\({}^{\circ}\) internal knee angle can be achieved [41]. As such, the low bar squat typically cannot be performed to a full squat position. Parallel squat: A parallel squat is performed to an internal knee angle between 60 and 70\({}^{\circ}\), where a straight horizontal line can be drawn between in the inguinal fold and the top of the knee musculature, just proximal to the patella [2; 45; 67; 68; 69]. The parallel squat can be performed with either variant of the back squat or the front squat. This depth (parallel) is commonly associated with the low bar or powerlifting squat [41]. While the high bar squat can be performed to parallel, it is often performed to a full squat position. Overall, the parallel squat is one of the most common exercises performed when targeting the development of lower body strength [2; 76]. Half squat: A half squat is generally performed to a depth in which an 80-100\({}^{\circ}\) internal knee angle is achieved [2; 40; 66; 77; 78; 79]. Half squats can be performed using the back, front, or Smith machine squats [12]. Because of the lesser degree of knee flexion associated with the half squat, substantially higher training loads can be used than loads in either the parallel or full back squat. The ability to handle higher loads in this range of knee \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Type** & **Common Variant** & **Internal Angle of Knee** & **Description of Bottom Position** & **References** \\ \hline Jump Squat & Parallel squat & 60-70\({}^{\circ}\) & The tops of the thighs are positioned so that they are below parallel when compared to the floor. Additionally, a straight horizontal line can be drawn from the top of the knee to the inguinal fold. & [71] \\  & Half squat & 80–100\({}^{\circ}\) & In this position the bottom of the thigh is approximately parallel to the floor. & [72; 73] \\ \hline Front Squat & Full squat & 40–45\({}^{\circ}\) & Tops of the thighs are positioned so that they are below parallel when compared to the floor. Tops of the thighs are positioned so that they are slightly below parallel when compared to the floor. Additionally, a straight horizontal line can be drawn from the top of the knee to the inguinal fold. & [35] \\  & Parallel squat & 60-70\({}^{\circ}\) & In this position the bottom of the thigh is approximately parallel to the floor. & [27; 35] \\  & Half squat & 80–100\({}^{\circ}\) & In this position the bottom of the thigh is approximately parallel to the floor. & [27; 35] \\  & & & Often categorized as halfway between a full squat and an upright standing position. Often used as part of strength–power–potentiating complexes. & [70] \\  & Quarter squat & 110–140\({}^{\circ}\) & In this position the top of the thigh is slightly below parallel to the floor. Additionally, a straight horizontal line can be drawn from the top of the knee to the inguinal fold. & [38; 58; 59] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._angles is related to the higher force production capacities that occur closer to the apex of the ascending strength curve for this movement pattern [80]. Quarter squat: A quarter squat is typically performed at a knee angle between 110-140\({}^{\circ}\)[66]. The quarter squat is often performed from a dead stop and would represent a concentric squat movement [70].