Range of motion, neuromechanical, and architectural adaptations to plantar flexor stretch training in humans

Abstract

Blazevich AJ, Cannavan D, Waugh CM, Miller SC, Thorlund JB, Aagaard P, Kay AD. Range of motion, neuromechanical, and architectural adaptations to plantar flexor stretch training in humans. 117: 452-462, 2014. First published June 19, 2014 doi:10.1152/japplphysiol.00204.2014.-The neuromuscular adaptations in response to muscle stretch training have not been clearly described. In the present study, changes in muscle (at fascicular and whole muscle levels) and tendon mechanics, muscle activity, and spinal motoneuron excitability were examined during standardized plantar flexor stretches after 3 wk of twice daily stretch training (4 ϫ 30 s). No changes were observed in a nonexercising control group (n ϭ 9), however stretch training elicited a 19.9% increase in dorsiflexion range of motion (ROM) and a 28% increase in passive joint moment at end ROM (n ϭ 12). Only a trend toward a decrease in passive plantar flexor moment during stretch (Ϫ9.9%; P ϭ 0.15) was observed, and no changes in electromyographic amplitudes during ROM or at end ROM were detected. Decreases in H max:Mmax (tibial nerve stimulation) were observed at plantar flexed (gastrocnemius medialis and soleus) and neutral (soleus only) joint angles, but not with the ankle dorsiflexed. Muscle and fascicle strain increased (12 vs. 23%) along with a decrease in muscle stiffness (Ϫ18%) during stretch to a constant target joint angle. Muscle length at end ROM increased (13%) without a change in fascicle length, fascicle rotation, tendon elongation, or tendon stiffness following training. A lack of change in maximum voluntary contraction moment and rate of force development at any joint angle was taken to indicate a lack of change in series compliance of the muscle-tendon unit. Thus, increases in end ROM were underpinned by increases in maximum tolerable passive joint moment (stretch tolerance) and both muscle and fascicle elongation rather than changes in volitional muscle activation or motoneuron pool excitability. J Appl Physiol

Specialized properties of the triceps surae muscle‐tendon unit in professional ballet dancers

“…The numerical values may indicate that muscle contributes to a greater extent in dancers (63% of maximal MTU elongation) compared to controls (53%); however, these differences did not reach statistical significance. Greater contribution from muscle would be in agreement with Abellaneda et al, where fascicles contributed 72% and tendon 28% at 30° dorsiflexion, and an intervention study which found increased muscle and fascicle strain and decreased tendon strain at a constant joint angle following stretching training . Taken together, these findings suggest that the capacity for muscle elongation plays an important role for ROM.…”

Effects of Acute Fatigue of the Hip Flexor Muscles on Hamstring Muscle Extensibility

“…The greater hip ROM reached in the passive tests after fatigue condition could be due to changes in the mechanical properties (i.e. muscle stiffness or viscoelastic deformation) (Magnusson et al, 1996), changes in stretch reflex activity (Blazevich et al, 2014) or greater subjective tolerance to passive stretch (Magnusson et al, 2001). Stretch tolerance can be defined as the ability of a participant to tolerate an increase in the discomfort of the stretching procedure at the terminal range of motion (Reid and McNair, 2004).…”

Does Stretching Have Long-Term Effects on Muscle Performance? A Clinical Commentary

“…Therefore, it becomes hard to consider sarcomerogenesis as a possible mechanism for increased performance following flexibility training. A recent investigation [31] reviewed six studies [26,28,[32][33][34][35] that evaluated the influence of static stretching training on isometric contractions. The authors observed that none of the included studies showed any improvement in performance after flexibility training using static stretching.…”