Hip abductor muscle activity during walking in individuals with gluteal tendinopathy

The external hip adduction moment during walking is greater in individuals with gluteal tendinopathy (GT) than pain-free controls. Although this likely represents a greater demand on the hip abductor muscles implicated in GT, no study has investigated activation of these muscles in GT. For this purpose, fine wire electrodes were inserted into the segments of the gluteus minimus and medius muscles, and surface electrodes placed on the tensor fascia lata, upper gluteus maximus, and vastus lateralis muscles of eight individuals with, and eight without, GT. Participants underwent six walking trials. Individual muscle patterns were compared between groups using a wavelet-based linear effects model and muscle synergy analysis performed using non-negative matrix factorization to evaluate muscle activation patterns, within- and between-participant variability. Compared to controls, individuals with GT exhibited a more sustained initial burst of the posterior gluteus minimus and middle gluteus medius muscle segments. Two muscle synergies were identified; Synergy-1 activated in early-mid stance and Synergy-2 in early stance. In GT participants, posterior gluteus minimus and posterior gluteus medius and tensor fascia lata contributed more to Synergy-1 active during the period of single leg support. Participants with GT exhibited reduced within-participant variability of posterior gluteus medius and reduced between-participant variability of anterior gluteus minimus and medius and upper gluteus maximus. In conclusion, individuals with GT exhibit modified muscle activation patterns of the hip abductor muscles during walking, with potential relevance for gluteal tendon loading.