Effects of ankle joint cooling on peroneal short latency response

While cryotherapy has direct physiological effects on contractile tissues, the extent to which joint cooling affects the neuromuscular system is not well understood. The purpose of the study was to detect changes in ankle dynamic restraint (peroneal short latency response and muscle activity amplitude) during inversion perturbation following ankle joint cryotherapy. A 2x3 factorial design was used to compare reaction time and EMG amplitude data of treatment conditions (cryotherapy and control) across time (pre-treatment, post-treatment, and 30 min post-treatment). Thirteen healthy volunteers (age 23 +/- 4 yrs, ht 1.76 +/- 0.09 m, mass 78.8 +/- 16.6 kg), with no history of lower extremity joint injury participated in this study. Surface EMG was collected from the peroneus longus (PL) of the dominant leg during an ankle inversion perturbation triggered while walking. Subjects walked the length of a 6.1 m runway 30 times. A trap door mechanism, inducing inversion perturbation, was released at heel contact during six randomly selected trials for each leg. Following baseline measurements, a 1.5 L bag of crushed ice was applied to the lateral ankle of subjects in the treatment group with an elastic wrap. A bag similar in weight and consistency was applied to the lateral ankle of subjects in the control group. A repeated measures ANOVA was used to compare treatment conditions across time (p < 0.05). Maximum inversion range of motion was 28.4 +/- 1.8 degrees for all subjects. No overall condition by time difference was detected (p > 0.05) for PL reaction time. Average RMS EMG, normalized to an isometric reference position, increased in the cryotherapy group at the 30 min post-treatment interval relative to the control group (p < 0.05). Joint cooling does not result in deficiencies in reaction time or immediate muscle activation following inversion perturbation compared to a control.