An investigation into the effect of stretching frequency on range of motion at the ankle joint
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Stretching is a widely prescribed technique that has been demonstrated to increase range of motion. Consequently it may enhance performance and aid in the prevention and treatment of injury. Few studies have investigated the frequency of stretching on a daily basis. The purpose of this study was to investigate the effect of stretching frequency on range of motion at the ankle joint. The detraining effect was also investigated after a period without stretching. Thirty-one female subjects participated in this study. They were randomly assigned to a control group who did not stretch a group who stretched two times per week (Stretch-2) or a group who stretched four times per week (Stretch-4). The stretching intervention was undertaken over four weeks and targeted the gastrocnemius and soleus muscles. Each stretch was held for duration of 30 seconds and repeated five times. Prior to the intervention (PRE), dorsiflexion was measured using a weights and pulley system that passively moved the ankle joint from a neutral position into dorsiflexion. After the four week stretching period (POST), dorsiflexion was measured once again to determine the change following the stretching programme. Following a further four week period where no stretching took place (FINAL), dorsiflexion was measured to determine the detraining effect. Electromyography was used to monitor the activity of the plantarflexors and dorsiflexors during the measuring procedure. The results of the study showed a significant increase in ankle joint range of motion for the Stretch-4 group (p<0.05) when comparing PRE and POST measurements. The Stretch-2 and control groups did not show significant differences (p>0.05) between PRE and POST measurements. When comparing the PRE and FINAL measurements of the Stretch-4 group, no significant differences were recorded (p>0.05). The POST and FINAL measurements were significantly different (p<0.05). After the detraining period the Stretch-4 group lost 99.8% of their range of motion gains. The present data provide some evidence that the viscoelastic properties of the muscle stretched were unchanged by the four week static stretching programme. The mechanism involved in the observed increase in range of motion for the Stretch-4 group is possibly that of enhanced stretch tolerance of the subject. Further research is required to support this conjecture.