Trunk Position Influence H:Q RATIO of Lead Lower Extremity During Bulgarian Split Squat Exercise

Abstract

This study aimed to investigate the variation in the H:Q ratio by comparing two trunk angles during the Bulgarian Split Squat (BSS) exercise. It has been shown that the ratio of quadriceps muscle activity to hamstring muscle activity is important, affecting knee joint function and injury risk. Twenty-one healthy male participants were recruited in this study. The participants were guided to repeat the BSS three times at normal posture and 30° trunk anterior tilt. The surface electromyography (EMG) activity was measured for 5 sec on the rectus femoris and hamstring muscles during a phase of BSS when the participant's knee touched the mat to be lifted again. The EMG activity was normalized via the maximal voluntary isometric contraction (MVIC) estimated using the manual muscle test. To examine the variation in the H:Q ratio, the paired sample t-test was used and the significance level was set to .05. The result showed that the H:Q ratio was higher at 30° trunk anterior tilt. The findings of this study indicate that the 30° trunk anterior tilt during the BSS could increase the H:Q ratio and positively control the stress on the anterior cruciate ligament (ACL), compared to the normal posture. It is suggested that experts should always evaluate the relative muscle strength of the femoral quadriceps and hamstrings in addition to H:Q RATIO for injury prevention purposes.