Effects of sling location and knee posture on gluteus maximus, biceps femoris, and multifidus activity during sling bridge in subjects with non-specific lower back pain

BackgroundSling bridge exercise is an important exercise for closed-chain strength training used in clinical settings. Sufficient strengths of the various hip muscles are needed for accurate movement of the hip joint.ObjectiveTo compare the difference in the electromyographic activities of the gluteus maximus (GM), GM/biceps femoris (BF), and the rating of perceived exertion (RPE), the visual analogue scale (VAS) in individuals with non-specific lower back pain (NSLBP) among four different sling-bridge exercises.MethodsTwenty NSLBP participants were included. They were asked to perform different sling-bridge exercises as follows: (1) Sling on the heel with knee extension; HKE, (2) Sling on the heel with knee flexion; HKF, (3) Sling on the knee with knee extension; KKE, (4) Sling on the knee with knee flexion; KKF] in random order. GM, BF, and MF muscle activities were measured by surface electromyography during the exercises. One-way repeated analysis of variance and Bonferroni post hoc test were used to compare normalized muscle activities. The significance level was set at α = 0.01.ResultsThe muscle activity of GM and the ratio of GM/BF muscle activity were significantly different among four different conditions (HKE, HKF, KKE, KKF) (adjusted p-value; P_adj < 0.01). The muscle activity of GM was higher during the KKF sling-bridge exercise than the HKE, HKF, and KKE sling-bridge exercises (P_adj < 0.01). The ratio of GM/BF muscle activity during the KKF sling bridge exercise was higher than the HKE, HKF, and KKE sling-bridge exercises (P_adj < 0.01). In contrast, the visual analogue scale (VAS) and rating of perceived exertion (RPE) during the KKF sling-bridge exercise were smaller than the HKE, HKF, and KKE sling-bridge exercises (P_adj < 0.01).ConclusionKKF sling-bridge exercise can be recommended to selectively facilitate the muscle activity of GM and improve the ratio of GM/BF muscle activity without an increase in VAS and RPE in individuals with NSLBP.