No 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 (r(2) 0.66) and of surface EMG amplitude (r(2) 0.57). Surface EMG enabled higher torque prediction (r(2) 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.

Increased gluteus minimus motion during the swing phase and earlier gluteus minimus and superficial gluteus medius motion in individuals with hip pain suggest an overall increase of muscle activity, possibly a protective behavior.

, J. 2014. Separate assessment of gluteus medius and minimus: B-mode or M-mode ultrasound? Physiotherapy Ultrasound imaging of hip abductors 2 ABSTRACTThe hip abductors gluteus medius (Gmed) and minimus (Gmin) differ slightly in function and how they are affected by hip joint pathology. A separate assessment of Gmed and Gmin is feasible by ultrasound (US) imaging. B-mode and M-mode US can be used to measure muscle thickness. Two B-and two M-mode scans of Gmed 5and Gmin thickness were taken in relaxation on sixteen asymptomatic volunteers, repeated within four days on eleven subjects. Three types of intra-rater reliability of muscle thickness measurements were examined: within-session reliability comparing two scans from the same session, between-days reliability comparing thickness from two scanning occasion within four days, and reliability of taking thickness 10 measurements by re-measuring the same US scans after one week. Thickness