Effects of Heating on Tendon Mechanical Properties and Performance during Stretch-Shortening Cycle Exercises.

Abstract

Purpose: The purpose of this study was to investigate the effects of heating on Achilles tendon mechanical properties (elongation, elastic energy, and hysteresis) and performance during stretch-shortening cycle exercise (pre-stretch augmentation and efficiency).

Methods: Fifteen males participated in this study. Before and after heating (30 min) and nonheating (control) conditions, the mechanical properties of the Achilles tendon during ramp and ballistic contractions and two kinds of jumps (no-countermovement and countermovement jumps) were measured. In addition, electromyographic activities of the plantar flexor muscles (medial gastrocnemius, lateral gastrocnemius, and soleus muscles) and oxygen consumption were measured during 5 min of submaximal repetitive jumps after both interventions (heating and control).

Results: Although no changes in tendon elongation at all force levels and elastic energy during ramp and ballistic contractions were observed, tendon hysteresis decreased by 14.2% during ramp contraction ( P = 0.015 according to the paired t -test) and 8.0% during ballistic contraction ( P = 0.006 according to the paired t -test) after heating. No changes in no-countermovement and countermovement jump heights were found after both interventions. The electromyographic activities of gastrocnemius muscles at the first half and soleus muscle at all time points were significantly lower for heating than for control conditions. No difference in oxygen consumption was found between heating and control conditions.

Conclusions: These results suggest that heating reduces tendon hysteresis and enhances efficiency (assessed by electromyographic activity) during repetitive submaximal jumps.