Influence of the Amount of Instability on the Leg Muscle Activity During a Loaded Free Barbell Half-Squat

Abstract

This study aimed to understand the acute responses on the muscular activity of primary movers during the execution of a half-squat under different unstable devices. Fourteen male and female high-standard track and field athletes were voluntarily recruited. A repeated measures design was used to establish the differences between muscle activity of the primary movers, the body centre of mass acceleration and the OMNI-Perceived Exertion Scale for Resistance Exercise (OMNI-Res) in a half-squat under four different stability conditions (floor, foam, BOSU-up and BOSU-down). A significant correlation was found between the highest performance limb muscle activity and body centre of mass acceleration for half-squat floor (r = 0.446, p = 0.003), foam (r = 0.322, p = 0.038), BOSU-up (r = 0.500, p = 0.001), and BOSU-down (r = 0.495, p = 0.001) exercises. For the exercise condition, the half-squat BOSU-up and BOSU-down significantly increased the muscle activity compared to half-squat floor (vastus medialis: p = 0.020, d = 0.56; vastus lateralis: p = 0.006, d = 0.75; biceps femoris: p = 0.000–0.006, d = 1.23–1.00) and half-squat foam (vastus medialis: p = 0.005–0.006, d = 0.60–1.00; vastus lateralis: p = 0.014, d = 0.67; biceps femoris: p = 0.002, d = 1.00) activities. This study contributes to improving the understanding of instability training, providing data about the acute muscular responses that an athlete experiences under varied stability conditions. The perturbation offered by the two BOSU conditions was revealed as the most demanding for the sample of athletes, followed by foam and floor executions.

Effects of 8-weeks of stable vs unstable surface destabilizing training on shot outcome in elite golfers (Efectos de 8 semanas de entrenamiento desestabilizador en superficies estables vs inestables sobre el resultado de los golpes en golfistas de élite)

“…Likewise, a high level of training is a variable that can reduce the effectiveness of training on unstable surfaces (Chulvi-Medrano et al, 2010), and higher degrees of instability may be necessary to achieve better adaptations (Wahl & Behm, 2008). Buscà et al, study showed that some unstable exercises in the same population and anatomic region have a higher effect on muscle activation than others (Busca et al, 2020). For that reason, a proper selection of exercises for every training program also seems a crucial aspect.…”

Biomechanical analysis of lifting on stable versus unstable surfaces—a laboratory-based proof-of-concept study

“…Although some balance was required to remain still on the psoas pillow, there was a low risk for the participants to lose their balance, which we felt was important for safety reasons. In our main study, we plan to use a BOSU-up and BOSU-down approach as in the study of Busca et al [ 15 ]. For further studies of unstable surfaces, we believe that researchers should study surfaces with higher demands on balance, for example, a larger gym mat, or tests in an authentic work environment, such as on a boat.…”

“…EMG electrodes were attached bilaterally to the mm. Erector Spinae and above the muscle bellies of m vastus medialis, according to Seniam guidelines [ 15 ]. The same test leader attached the EMG electrodes to all participants.…”

Superimposed vibration on suspended push-ups

“…However, this might not happen in less experienced populations, where motion control should be guaranteed. Other protocols used accelerometers for this purpose ( Buscà et al, 2020 ).…”

“…Beyond the physiological markers, reporting the perception of how hard the load is lifted has been a recurrent method to guide and monitor the strength training programs. For this purpose, OMNI Perceived Exertion Scale for Resistance Exercise (OMNI-Res) has been developed by Robertson et al (2003) and validated in several strength and conditioning contexts with promising results ( Robertson et al, 2005 ; Lagally & Robertson, 2006 ; Colado et al, 2012 ; Bautista et al, 2014 ; Buscà et al, 2020 ). Indeed, the mentioned studies reported that the scale is strongly connected to 1RM, muscle activity, or total weight lifted in different training environments.…”