The effect of therapeutic muscle stretch on neural processing

Therapeutic muscle stretch is a commonly used procedure despite little evidence in support of efficacy or information about the mechanisms underlying the various methods. The purpose of this work was to compare the sequential application of static and ballistic muscle stretch with static muscle stretch alone, using the electrically elicited Hoffmann reflex (H-reflex) as a measure of excitability of homonymous motoneurons. The foot was passively dorsiflexed and either maintained in this position or rapidly and repeatedly dorsiflexed at a velocity of 1.0 radian/sec. Hoffmann reflexes were taken using established criteria under control conditions and during stretch conditions. An analysis of variance indicated a significant difference (p < 0.05) between condition means, with H-reflex amplitude reducing to 60 and 15% of the control value during static and ballistic stretch, respectively. Since reductions in alpha-motoneuron pool excitability correlate with increased flexibility, ballistic stretch applied following static stretch appears more effective than static stretch alone.