The squat variations were performed on the force plate and during the bilateral squat the participants placed their feet in their preferred position (to avoid extra stress upon the participant and increase the external validity towards training). To reduce the technique and balance requirement while performing 4RM loads, a 90 ° knee angle during all lifts was used to ensure that the heel was in contact with the floor at all times. Furthermore, participants practiced the unilateral squat techniques during these sessions, since they were less familiar with these two techniques with these loads. 23 Furthermore, greater gluteus and erector spinae activation during the unilateral lifts with the foot backwards than with the foot forwards was hypothesized due to more flexion of the trunk.īefore the test session, participants were given a two-week familiarization period (two to three training sessions) to establish and train with loads that approached their assumed 4-RM for bilateral squat (descent to 90 ° knee angle). However, greater muscle activity of the leg muscles in the unilateral lifts was expected, which would be affected by an increase balance requirement during single-leg lifts. It was hypothesized that force output per leg would be the same between bilateral and unilateral back squats due to the same external load per leg being used. A secondary purpose was to analyze muscle activity between unilateral squats with the lifted foot forwards vs. Therefore, the purpose of this study was to compare muscle activity, kinetics, and barbell kinematics between unilateral and bilateral squats with the same external load per leg in experienced resistance-trained participants. This information could help researchers, trainers and physiotherapists to gain insight into what happens when performing squatting exercises and thereby could help in designing rehabilitation or strength programs. These facets of single-leg squatting have not been studied before, to the authors knowledge. Unilateral squats can be performed with the non-weight bearing foot positioned either forwards or backwards, which could influence weight distribution and thereby muscle activation and kinematics. 19- 22 To the authors’ knowledge, no studies have compared heavy weight (>80% of 1 repetition maximum) bilateral squats with unilateral, single-leg squats (with foot forwards or backwards) when the same external load per leg is used. Limited studies have performed analysis of single-leg squats, and these studies were focused on unilateral squats without extra load for rehabilitation purposes. 17, 18 Thus, in fact they are not truly unilateral squats. rear foot on a box) force is produced by the front and rear leg, which is helped by the increase in the base of support. 12- 16 In addition, these studies comparing bilateral with unilateral squats have used different protocols for both conditions (split legs and rear foot elevated) and different loads between bilateral and unilateral squats, and neither of these studies compared unilateral squats without any support on the rear leg with bilateral squats. Yet, few studies exist that have compared force output and muscle activity between bilateral and unilateral squats. Therefore, to improve these performances most effectively, resistance training should closely resemble the mechanics and forces required to perform these necessary skills. 6, 8, 9 Furthermore, running, kicking, changing running direction, and jumping are all unilateral movement patterns that are performed in a unilateral weight-bearing phase. 5- 7 Consequently, including unilateral instead of bilateral exercises in training may be favorable to increase power and strength of the muscles, but the evidence is not conclusive. two-legged squat), is referred to as bilateral deficit. one-legged squat) than in a bilateral exercise (i.e. The ability to generate more force in sum performing two unilateral exercises (i.e. 4 Still, little is known regarding the effects of performing these unilateral exercises on muscle recruitment compared with unilateral exercises. 4 However, these unilateral exercises, are regularly included within strength programs as additional exercises to the two-legged back squat to increase volume load or variation. 1- 3 In recent years, the use of unilateral exercises such as lunges, step-ups and one-legged squats have become popular in strength and conditioning practice. Bilateral exercises, such as snatches, deadlifts and two-legged back squats are frequently implemented as an important part of resistance training programs to improve strength, hypertrophy and power for the lower body.
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