Abstract
The aim of this study was to examine the long-term effects of static stretching of the plantar-flexor muscles on eccentric and concentric torque and ankle dorsiflexion range of motion in healthy subjects. Seventy five healthy male volunteers, with no previous history of trauma to the calf that required surgery, absence of knee flexion contracture and no history of neurologic dysfunction or disease, systemic disease affecting the lower extremities were selected for this study. The participants were divided into three equal groups. The control group did not stretch the plantar-flexor muscles. Two Experimental groups (trained and untrained) were instructed to perform static stretching exercise of 30 second duration and 5 repetitions twice daily. The stretching sessions were carried out 5 days a week for 6 weeks. The dorsiflexion range of motion was measured in all subjects. Also measured was the eccentric and concentric torque of plantar-flexors at angular velocities of 30 and 120°/s pre and post stretching. Analysis of variance showed a significant increase in plantar-flexor eccentric and concentric torque (p < 0.05) of trained and untrained groups, and an increase in dorsiflexion range of motion (p < 0.05) at both angular velocities for the untrained group only. The static stretching program of plantar-flexors was effective in increasing the concentric and eccentric plantarflexion torque at angular velocities of 30 and 120°/s. Increases in plantar-flexors flexibility were observed in untrained subjects.
Highlights
Strength and flexibility are common components of exercise programs; it is not clear how best include both of these elements in a single training program
The stretching sessions were carried out 5 days a week for 6 weeks because this frequency exceeded that reported by most of the previous investigators (Bohannon et al, 1994; Grady and Saxena, 1991; Muir et al, 1999) who did not find lasting gains in active ankle dorsiflexion range of motion (ROM), exceeded the stretching technique conducted by Johanson et al (2008) who proved that dorsiflexion ROM increased after a gastrocnemius stretching program
The results of this study proved that plantar-flexor muscles static stretching increased ankle dorsiflexion ROM of untrained group without consideration of the subtalar joint position
Summary
Strength and flexibility are common components of exercise programs; it is not clear how best include both of these elements in a single training program. Various studies found that stretching exercises preceding the main strength activity significantly decreased performance (Avela et al, 2004; Behm et al, 2006; Brandenburg, 2006; Cramer et al, 2005; Derek et al, 2005; Marek et al, 2005; Nelson et al, 2001; Nelson et al, 2005; Power et al, 2004; Rubini et al, 2005; Yamaguchi et al, 2006). These studies used stretching exercise of lower extremities and found decreases in strength ranging from 4.5 to 28%, irrespective to the testing mode (i.e. isometric, isotonic or isokinetic) (Rubini et al, 2007)
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