Effect of modified bridge exercise on trunk muscle activity in healthy adults: a cross sectional study

DESIGN: This is a cross-sectional study. SETTING: University research laboratory. PARTICIPANTS: Fifteen healthy adults (mean age: 27.47 years) volunteered for this study. INTERVENTION: The individuals performed standard bridge exercise and modified bridge exercises with right leg-lift (single-leg-lift bridge exercise, single-leg-lift bridge exercise on an unstable surface, and single-leg-lift hip abduction bridge exercise). MAIN OUTCOME MEASURES: During the bridge exercises, electromyography of the rectus abdominis, internal oblique, erector spinae, and multifidus muscles was recorded using a wireless surface electromyography system. Two-way repeated-measures analysis of variance (exercise by side) with post hoc pairwise comparisons using Bonferroni correction was used to compare the electromyography data collected from each muscle. RESULTS: Bilateral internal oblique muscle activities showed significantly greater during single-leg-lift bridge exercise (95% confidence interval: right internal oblique = −8.99 to −1.08, left internal oblique = −6.84 to −0.10), single-leg-lift bridge exercise on an unstable surface (95% confidence interval: right internal oblique = −7.32 to −1.78, left internal oblique = −5.34 to −0.99), and single-leg-lift hip abduction bridge exercise (95% confidence interval: right internal oblique = −17.13 to −0.89, left internal oblique = −8.56 to −0.60) compared with standard bridge exercise. Bilateral rectus abdominis showed greater electromyography activity during single-leg-lift bridge exercise on an unstable surface (95% confidence interval: right rectus abdominis = −9.33 to −1.13, left rectus abdominis = −4.80 to −0.64) and single-leg-lift hip abduction bridge exercise (95% confidence interval: right rectus abdominis = −14.12 to −1.84, left rectus abdominis = −6.68 to −0.16) compared with standard bridge exercise. In addition, the right rectus abdominis muscle activity was greater during single-leg-lift hip abduction bridge exercise compared with single-leg-lift bridge exercise on an unstable surface (95% confidence interval = −7.51 to −0.89). For erector spinae, muscle activity was greater in right side compared with left side during all exercises (95% confidence interval: standard bridge exercise = 0.19–4.53, single-leg-lift bridge exercise = 0.24–10.49, single-leg-lift bridge exercise on an unstable surface = 0.74–8.55, single-leg-lift hip abduction bridge exercise = 0.47–11.43). There was no significant interaction and main effect for multifidus. CONCLUSIONS: Adding hip abduction and unstable conditions to bridge exercises may be useful strategy to facilitate the co-activation of trunk muscles.