Paraffin therapy induces a decrease in the passive stiffness of gastrocnemius muscle belly and Achilles tendon: A randomized controlled trial

BACKGROUND: The purposes of this study were to examine the feasibility of using the MyotonPRO digital palpation device in measuring the passive stiffness of gastrocnemius muscle belly and Achilles tendon; to determine between-days test–retest reliability of MyotonPRO; and to evaluate the acute effect of paraffin therapy on stiffness measurements in healthy participants. METHODS: It is a randomized controlled trial. Twenty healthy participants (male, n = 10; female, n = 10; total, n = 20) were recruited to evaluate the passive stiffness of gastrocnemius muscle belly and Achilles tendon. Dominant and nondominant legs were randomly divided into an experimental side (20 cases) and a control side (20 cases). The experimental side received 20 minutes of paraffin therapy. RESULTS: The stiffness of muscle and tendon in the experimental side decreased significantly after paraffin therapy (P < .01), whereas no significant differences in stiffness measurements were found in the control side (P > .05). The passive stiffness of muscle and tendon was positively correlated with the ankle from 30° plantar flexion to10° dorsiflexion for dominant legs. Between-days test–retest reliability in stiffness measurements was high or very high (ICCs were above 0.737). CONCLUSION: Paraffin therapy induces a decrease in the passive stiffness of gastrocnemius muscle belly and Achilles tendon. Furthermore, the MyotonPRO can reliably determine stiffness measurements.