Effects of Suspension Training and Unstable Surface on the Lower Limb

Abstract

Unstable surfaces have been used to enhance the muscle activity (MA) in different strength and conditioning exercises. Some evidence supports that the unstable surface increases the motor unit recruitment and improves the neuromuscular coordination in order to maintain balance. Thus, an emerging trend is the utilization of suspension devices to increases the amount of instability. PURPOSE: To examine the MA of the lower limb when perform a Bulgarian squat, suspended lunge and suspended lunge-Bosu. METHODS: Seventeen physically active university students (age = 24±3.31y, height = 1.78±0.06 m, weight= 74.99±9.39 kg) were recruited to perform a Bulgarian squat, suspended lunge and a suspended lunge-Bosu. The MA was assessed using sEMG on the front leg (FL) to measure the rectus femoris_FL (RF_FL), biceps femoris (BF), gluteus medius (Gmed), vastus medialis (VM), vastus lateralis (VL) and the RF of the rear leg (RF_RL). The activity of all analyzed muscle was expressed as percentage of maximum voluntary isometric contraction (% MVIC). A one-way repeated-measures ANOVA was carried out to determine the effect of exercise condition on MA. RESULTS: A main effect was found for exercise condition on muscle activation for RF_FL [F(2,32) = 7.678 p=0.002], BF [F(2,32) = 4.076 p=0.026], Gmed [F(2,32) = 33.878 p=0.000], VL [F(2,32) = 3.508 p=0.042] and RF_RL [F(2,32) = 5.704 p=0.008], except for VM [F(2,32) = 2.346 p=0.112]. The suspended lunge-Bosu showed a higher activation for RF_FL, Gmed, and VL (44.25%±4.78; 66.56%±4.84; 75.58%±4.48, respectively) respect Bulgarian squat (RF_FL: 33.13%±3.87 p=0.024; Gmed: 47.97%±4.41 p=0.000) and suspended lunge (RF_FL: 33.86%±3.82 p=0.006; Gmed: 47.89%±3.21 p=0.000; VL: 63.87%±4.69 p=0.041). However, the suspended lunge-Bosu reached a lower activity for RF_RL (25.98%±2.60) in comparison with Bulgarian squat (RF_RL: 35.69%±4.19 p=0.025). CONCLUSIONS: These findings suggested that leaning the RL on the suspension device did not provoke the sufficient stimuli to increases the muscle demands of the FL, but adding the unstable device on the FL in a suspended lunge could be a challenge to increase the MA. Funding for this project was provided by Secretaria d’Universitats i Recerca del Departament d’Empresa i Coneixement de la Generalitat de Catalunya i als Fons Socials Europeus.