The effect of thoracic spine high-velocity low-amplitude thrust manipulation on myoelectric activity of the lower trapezius and posterior deltoid muscles during treadmill walking

**Objectives** To investigate the effect of thoracic spine thrust manipulation on the EMG activity of posterior deltoid and lower trapezius during treadmill walking. **Methods** Volunteers (n = 40; 19 males and 21 females) were randomly assigned to a ‘sham ultrasound’ control group (n = 20) or a thoracic spine high-velocity thrust (HVLAT) manipulation group (n = 20). Surface EMG recordings were collected from the right posterior deltoid and lower trapezius muscles whilst participants walked on a treadmill for 2 min, at 2.8 mph, both prior to and immediately post-intervention. EMG recordings were analysed by evaluating the difference of integral values for pre and post data using repeated measures ANOVA. **Results** Both control (sham ultrasound) and experimental groups (HVLAT) exhibited small non-significant reductions in post-intervention EMG activity of lower trapezius (p = 0.201) and a significant reduction in posterior deltoid (p = 0.003) during treadmill walking. No significant difference was found in the integrated EMG (IEMG) power between control and experimental group in either the ‘before’ or ‘after’ measurements for both target muscles. **Conclusions** Manipulation of the thoracic spine does not significantly alter the myoelectric activity of lower trapezius and posterior deltoid muscles during treadmill walking.