Purpose: Alterations in lower extremity muscle activation patterns (MAPs) of the gluteal, hip abductors, and erector spinae muscles have been associated with the presence of myofascial trigger points (TPs). TPs are focal tender areas in muscles and are associated with musculoskeletal pain. Latent myofascial TPs (Latent TPs) are tender areas in the muscle that do not cause familiar pain when palpated but have been shown to contribute to altered MAPs in scapular muscles and gluteal muscles. This study compared changes in MAPs under three test conditions in subjecets who present with latent TPs in the gluteus medius muscle. Methods: A single blind, randomized controlled block design with subjects stratified based on gender was used to compare changes in MAPs in three groups of subjects who presented with Latent TPs. Group 1 received no treatment, Group 2 was treated with a stretch of the gluteus medius muscle and Group 3 was treated with dry needling of Latent TPs in the gluteus medius muscle. This study quantified, using surface electromyography (sEMG), changes in MAPs during prone leg lift. MAPs were collected at two points in time: immediately before and after the intervention. For the dry needling group, qualitative data were gathered including subjective responses of the sensation experienced and descriptions of referral patterns. Subjects: Using a sample of convenience, 64 volunteers, ages 22-43, were recruited from the Georgia State University Division of Physical Therapy and assessed for the presence of gluteus medius latent TP(s). From that pool of eligible participants, 47 were randomly selected in a consecutive manner until all 3 groups were filled. Outcomes: Repeated measures analysis of variance with the Greenhouse-Geisser correction was used. No changes were found in MAPS from before to after the three interventions of rest, gluteus medius stretch, and dry needling during the prone leg raise, and there were no between group effects. The relative prevalence of latent trigger points in the non-symptomatic sample was similar to that presented in other studies. Subjective responses to dry needline were consistent with published reports of referral patterns. The lead researchers observed local twitch responses with dry needling, an unexpected finding given that a local twitch response is more commonly associated with active TPs rather than latent TPs. Relevance: Latent TPs are associated with movement dysfunction. The results may help in the design of future studies of latent TPs using sEMG as a measurement.
