Muscle thickness measurements to estimate gluteus medius and minimus activity levels

• Published in: Manual therapy 2014-10, Vol.19 (5), p.453-460
• Main Authors: Dieterich, Angela V, Pickard, Christine M, Strauss, Geoffrey R, Deshon, Louise E, Gibson, William, McKay, Janice
• Format: Article
• Language: English
• Subjects: Adult; Buttocks; Electromyography; Female; Hip; Humans; Male; Muscle; Muscle Contraction - physiology; Muscle, Skeletal - diagnostic imaging; Muscle, Skeletal - physiology; Physical Medicine and Rehabilitation; Torque; Ultrasonography; Ultrasound
• ISSN: 1356-689X; 1532-2769
• DOI: 10.1016/j.math.2014.04.014

Abstract The clinical assessment of gluteus medius and minimus force sharing requires non-invasive measurements of individual activity levels. Do ultrasound measurements of change of muscle thickness substitute invasive electromyography (EMG)? Isometric hip abduction in 20–80% maximal voluntary isometric contraction (MVIC) was measured using dynamometry, M-mode ultrasound for gluteus medius and minimus thickness and EMG using (1) surface electrodes on gluteus medius, n  = 15, (2) fine-wire electrodes in deep gluteus medius and minimus, n  = 6. Gluteus medius thickened by 5.0 (SD 2.5) mm at 80% MVIC while gluteus minimus thickness was constant in the surface EMG study and decreased by 1.6 (SD 1.6) mm at the more ventral location in the fine-wire EMG study. Thickness change of gluteus medius enabled prediction of torque ( r2 0.66) and of surface EMG amplitude ( r2 0.57). Surface EMG enabled higher torque prediction ( r2 0.84) than thickness change. Thickness change of gluteus minimus did not enable a practically relevant estimation of torque production. Ultrasound examination revealed a differential thickening behaviour of gluteus medius and minimus which enabled estimation of isometric torque production only for gluteus medius but with lower precision than surface EMG.