Effects Of Voluntary Abdominal Contraction On Scapulothoracic Muscle Activation In Prone Scapular Retraction Exercises

Scapular retraction exercises (SRE) in the prone position are commonly utilized in shoulder rehabilitation. Anterior pelvic tilt tends to increase during prone SRE. However, the effects on scapular muscle activation remain unclear when the lumbar spine is stabilized by voluntary abdominal contraction (VAC). PURPOSE: This study aimed to investigate scapulothoracic muscle activations during SRE performed in the prone position, with lumbopelvic stability maintained by VAC. METHODS: 30 healthy physically active (Tegner score of 5 and above) university students(15 males and females), (age: 23 ± 2.65 years, body mass index: 22.2 ± 1.81 kg/m2) were included. In random order, participants performed SRE in the prone position with 00, 45°, 90°, and 120° abductions. Exercises were performed both with and without VAC. A pressure biofeedback unit was used to measure VAC, while surface electromyographic recorded the activity of the upper trapezius (UT), lower trapezius (LT), and serratus anterior (SA) muscles during the concentric, eccentric, and isometric phases. A 2-way repeated measures ANOVA with two within factors (phase by condition) was employed to compare the activity levels (%MVIC). RESULTS: SRE at 00 and 450 increased the UT/LT muscle ratio when performed with VAC (ps < 0.05). Muscle activations during SRE with/without VAC are given in Table 1. CONCLUSIONS: At 00 and 450 SRE increases the UT/LT ratio, so its use with VAC is not recommended in the early phase of shoulder rehabilitation. The 120° SRE can be included in exercise programs, as it elicits the highest LT activation and enhances SA activation when performed with VAC. Table 1. - Muscle activation values with and without VAC Arm position Phase Without VACUT-(MVIC%)X(SD) With VACUT-(MVIC%)X(SD) p Without VACLT-(MVIC%)X(SD) With VACLT-(MVIC%)X(SD) p Without VACSA-(MVIC%)X(SD) With VACSA-(MVIC%)X(SD) p Without VAC UT/LTX(SD) With VACUT/LTX(SD) 00 abdSRE Con 9.18(9.6) 11.3(9.95) 0.46 13.2(6.5) 11.75(7.15) 0.02* 12.01(10.73) 12.18(11.31) 0.2 0.88(1.03) 1.25(1.31) * Iso 12.25(10.2) 13(9.64) 15.28(7.65) 15.31(8.61) 19.02(21.93) 18.5(19.14) 1.05(1.12) 1.34(1.93) Ecc 4.9(3.4) 7.06(5.6)a 6.94(3.76) 8.91(5.82)a 10.53(11.03) 12.65(14.15) 0.9(0.95) 1.31(1.66) 450 abdSRE Con 15.82(11.08) 14.82(8.1) 0.18 15.24(8.6)a 11.95(5.58) 0.04* 9.59(10.17) 9.7(9.37) 0.65 1.43(1.74) 1.78(2.47) * Iso 20.74(13.01) 20.87(10.9) 19.04(12.01)a 15.63(7.09) 15.5(22.5) 15.27(21.5) 1.55(1.56) 2.07(3.14) Ecc 8.78(5.43) 10.45(6.31)a 10.47(6.11) 9.83(5.2) 9.48(12.93) 9.2(12.13) 1.31(1.71) 1.76(2.84) * 900 abdSRE Con 25.61(17.39) 20.9(14.7) 0.08 20.26(10.4) 18.63(9.04) 0.18 6.06(5.06) 6.96(5.62) 0.24 1.43(1.10) 1.43(1.44) Iso 32.11(20.8) 27.2(14.4) 23(13.46) 20.94(11.5) 10.08(9.53) 9.23(7.25) 1.8(1.76) 1.69(1.59) Ecc 14.56(10.66) 13.23(6.86) 13.07(6.8) 12.7(6.44) 6.01(4.9) 6.42(5.24) 1.32(1.06) 1.3(1.09) 1200 abdSRE Con 29.63(17.24) 32.61(18.5) 0.78 35.6(16.3) 32.96(13.21) 0.36 5.62(4.24) 7.8(6.86)a 0.32 0.9(0.5) 1.04(0.51) Iso 38.19(25.21) 42.68(22.92) 41.41(22.36) 40.42(16.8) 7.53(6.89) 9.47(11.38) 1.07(0.82) 1.17(0.66) Ecc 18.28(10.81) 21.06(10.85) 22.65(12.12) 22.54(9.82) 4.53(3.68) 5.17(4.19)a 0.94(0.67) 1.02(0.58)