Trunk Muscle Activity Increases With Unstable Squat Movements

Abstract

The objective of this study was to determine differences in electromyographic (EMG) activity of the soleus (SOL), vastus lateralis (VL), biceps femoris (BF), abdominal stabilizers (AS), upper lumbar erector spinae (ULES), and lumbo-sacral erector spinae (LSES) muscles while performing squats of varied stability and resistance. Stability was altered by doing the squat movement on a Smith machine, a free squat, and while standing on two balance discs. Fourteen male subjects performed the movements. Activities of the SOL, AS, ULES, and LSES were highest during the unstable squat and lowest with the Smith machine protocol (p < 0.05). Increased EMG activity of these muscles may be attributed to their postural and stabilization role. Furthermore, EMG activity was higher during concentric contractions compared to eccentric contractions. Performing squats on unstable surfaces may permit a training adaptation of the trunk muscles responsible for supporting the spinal column (i.e., erector spinae) as well as the muscles most responsible for maintaining posture (i.e., SOL).

Trunk Muscle Activity During Lumbar Stabilization Exercises on Both a Stable and Unstable Surface

“…2,13 In contrast, trunk muscle activity increased when performing a squat on an unstable surface. 1 From these findings, the influence of surface stability on muscle activity appears to be muscle and exercise dependent. The exercises increased the perturbation to the trunk when the body's center of mass was over an unstable surface and further away from the stable surface.…”

“…17 Additionally, decrease of the contact area between the individual and the unstable surface increased the perturbation of the trunk, as demonstrated by increased muscle activity. 1,16,17 However, previous researchers have limited their measurement of muscle activity to the use of surface electrodes. There appears to be no published report describing the activity of local muscles during lumbar stabilization exercises.…”

Muscle Activation in the Loaded Free Barbell Squat

“…As a consequence, this exercise and a selection of variants have been subjected to research. For example, training studies have measured the impact of barbell squat loading schemes (14) on selected training adaptations including maximal strength (30) and power changes in the squat (29,31,14,18,2). Squat exercise training adaptations and their impact on a variety of performance parameters, in particular countermovement jump, acceleration and running speed (7,34) have also been reported.…”

“…There have also been studies (36) on the impact of squatting with or without a weight belt on trunk muscle activation. More recently a number of researchers have reported the effect of instability on trunk muscle activation and squat performance (20,21,23,2,3,33,13,27) The barbell squat was established as a key exercise in the physical preparation of athletes prior to the growing body of scientific evidence describing muscle activation in variations of this exercise. The organic manner in which this research has been conducted and published necessitates a review of the findings as they relate to athletic training and therefore inform practice.…”

Electromyographic and kinetic comparison of a flexible and steel barbell

“…These results have not been previously reported in the literature. Anderson and Behm (Anderson & Behm, 2005) found increased trunk muscle activity increases with unstable squat movements.…”