Comparison Of Deep Spine Stabilizing Musculature Activity During Common Low Back Exercises

Chronic low back pain (CLBP) is a major cause of participation restriction and disability worldwide. Rehabilitation for CLBP typically includes exercises to combat muscle disuse and subsequent morphological changes, yet it is unclear which specific exercises are most beneficial. Literature suggests exercises which stimulate and strengthen the deep and superficial multifidus may improve CLBP symptoms. Yet few studies have investigated activation of these deep spine stabilizers during exercise. PURPOSE: To determine if activation of the deep and superficial multifidus differs between bodyweight trunk extension, bodyweight reverse hyperextension, and weighted trunk extension exercises. METHODS: Thirteen healthy participants (8 males, aged 23.8 ± 7.1 years, mass 80.4 ± 14.3 kg) completed five repetitions of trunk extension, reverse hyperextension, and weighted trunk extensions with a five second isometric hold while activity of the deep and superficial multifidus were measured with indwelling electrodes. The weighted trunk extension was loaded to provide an equivalent torque on the extensor musculature as the reverse hyperextension exercise. Repeated measures ANOVAs were used to compare activity of the deep and superficial multifidus during both isometric (mean activation) and concentric (integrated activation) phases between exercises. RESULTS: During the isometric phase, the only significant difference between exercises was the superficial multifidus produced greater activation [50.9 ± 27.7% maximal voluntary contraction (MVC)] during the weighted trunk extension than bodyweight trunk extension (38.8 ± 30.4% MVC) (p < .05). However, during the concentric phase, the weighted trunk extension produced greater activity in the deep fibers (70.4 ± 29.1% MVC*s) than either bodyweight trunk extension (50.1 ± 18.1% MVC*s) or reverse hyperextension (44.9 ± 21.0% MVC*s) (p < .05). Similarly, superficial fibers achieved greater activation during the weighted trunk extension than during bodyweight trunk extension (52.0 ± 34.2 % MVC*s) or reverse hyperextension (46.9 ± 21.2% MVC*s) (p < .05). CONCLUSION: Greater activation of the multifidus occurred when an external load was applied, and the deep multifidus fibers may require both motion and an external load to achieve their greatest activation.