The influence of hip angle on dorsiflexion range of motion, passive angle moment and neuromuscular reflex activity of the triceps surae

Adopting a slumped position in the spine stretches the neuromeningeal tract, which is a common method to identify signs of neural tension including a pain response and limited range of motion (ROM) at the hip and knee (Boland & Adams, 2000). However, this phenomenon has not been examined at the ankle; therefore, the aims of the present study were to examine whether hip position, likely to illicit neural tension, would influence ankle dorsiflexion ROM, passive moment and electromyographic muscle activity of the triceps surae. Eighteen recreationally active participants (10 men and 8 women: mean ± SD age = 28.6 ± 6.3 yr, mass = 73.3 ± 12.9 kg, height = 1.7 ± 0.1 m) volunteered for the study after giving written, informed consent, with ethical approval from the University of Northampton. Passive dorsiflexion ROM trials were performed on an isokinetic dynamometer across three hip positions (supine = 10°; semi-reclined = 55°; upright = 85°). Dynamometry data measuring dorsiflexion ROM and passive ankle moment were recorded during the trials with electromyographic (EMG) activity of the triceps surae also recorded; simultaneous 3D motion analysis also measured ROM. Separate repeated measures ANOVA’s with post-hoc analysis determined the location of any significant differences between conditions; significance accepted at p<0.05. Significant differences were detected in dorsiflexion ROM (p<0.01), passive moment (p<0.05) and EMG (Sol, GM) (p<0.01) between hip flexion conditions. Post-hoc analyses revealed no difference between supine and semi-reclined hip positions in any measure, while the upright position had significantly lower dorsiflexion ROM, significantly lower passive moment but significantly higher EMG activity at peak ROM than both supine and semi-reclined conditions. Paired analyses between dynamometry and motion analysis ROM data revealed dynamometry significantly (p<0.01) overestimated ROM in each condition although this did not explain the differences across hip conditions. Despite the reduction in dorsiflexion ROM in the upright position there was a significant increase in EMG activity. As ROM was reduced it is unlikely that this was a stretch-reflex response from type Ia muscle afferents but may be the result of type IV nocireceptors. The reduction in dorsiflexion ROM clearly has implications for dynamometry testing protocols and subject positioning when examining ankle kinematics and mechanics. Similarly, the motion analysis data also revealed that dynamometry analysis overestimated ROM, with significantly greater overestimation in the two reclined positions due to increased heel displacement from the dynamometer footplate.