Biomechanical analysis of the single-leg decline squat

Abstract

Background: The single-leg squat on a 25˚decline board has been described as a clinical assessment tool and as a rehabilitation exercise for patients with patellar tendinopathy. Several assumptions have been made about its working mechanism on patellar load and patellofemoral forces, but these are not substantiated by biomechanical evaluations. Aim: To investigate knee moment and patellofemoral contact force as a function of decline angle in the singleleg squat. Methods: Five subjects performed single-leg eccentric squats at decline angles of 0˚, 5˚, 10˚, 15˚, 20˚and 25( with/without a backpack of 10 kg), and 30˚on a board that was placed over a forceplate. Kinematic and forceplate data were recorded by the Optotrak system. Joint moments of ankle, knee and hip were calculated by two-dimensional inverse dynamics. Results: Knee moment increased by 40% at decline angles of 15˚and higher, whereas hip and ankle moment decreased. Maximum knee and ankle angles increased with steeper decline. With a 10 kg backpack at 25d ecline, the knee moment was 23% higher than unloaded. Both patellar tendon and patellofemoral forces increased with higher decline angles, but beyond 60˚, the patellofemoral force rose steeper than the tendon force.Conclusions: All single-leg squats at decline angles .15˚result in 40% increase in maximum patellar tendon force. In knee flexions .60˚, patellofemoral forces increase more than patellar tendon forces. Higher tendon load can be achieved by the use of a backpack with extra weight.

A Biomechanical Investigation of A Single-Limb Squat: Implications for Lower Extremity Rehabilitation Exercise

“…Again, this finding can be related to the movement of the center of pressure in a posterior direction, which increases the flexion moment ( Figure 3). The finding is interesting to compare with the findings of Zwerver et al, 13 who noted that a 156 change in angle of inclination can result in a 40% increase in kneeflexion moment. Our findings indicate that a 166 change in the decline angle can result in a 30% increase in kneeflexion moment.…”

“…[10][11][12][13][14][15] Four comparisons were considered to be within the limits of the participants beginning to fatigue. To enable the participants to achieve these angles, we placed an adjustable board on top of the force platform.…”

“…[10][11][12] The concept of increased work of the knee extensors is supported by evidence suggesting that performing single-limb squats on a decline board at inclinations greater than 156 can increase the knee-flexion moments by up to 40%. 13 However, little additional evidence is available to suggest what other characteristics might be associated with these exercises, particularly in relation to passive and active tension of the calf muscles. Although empirical data relating to the biomechanics of single-limb squats are limited, researchers recently have documented interesting biomechanical characteristics associated with double-limb squats.…”

“…10,11 Investigators have documented only the use of 256 decline angles [10][11][12]14,15 and 306 decline angles. 13 To begin to understand the biomechanics of single-limb squat exercises, researchers must investigate the biomechanical demands associated with several decline angles. As with the suggested angle of inclination, the suggested depth of squat based on the angle of knee flexion 9,11,16 varies between 506 and 906.…”

“…Although many researchers have highlighted the effectiveness of decline squats as a rehabilitative tool [8][9][10][11][12][13] and have documented the biomechanical characteristics associated with double-limb squats, 14 very little is known about the biomechanics of these exercises. The purpose of our study was to investigate the biomechanical characteristics of and muscular involvement during single-limb squats performed on a flat surface and at different decline angles.…”