Effect of static stretch training on neural and mechanical properties of the human plantar‐flexor muscles

Abstract

To determine the contributions of neural and mechanical mechanisms to the limits in the range of motion (ROM) about a joint, we studied the effects of 30 sessions of static stretch training on the characteristics of the plantar-flexor muscles in 12 subjects. Changes in the maximal ankle dorsiflexion and the torque produced during passive stretching at various ankle angles, as well as maximal voluntary contraction (MVC) and electrically induced contractions, were recorded after 10, 20, and 30 sessions, and 1 month after the end of the training program. Reflex activities were tested by recording the Hoffmann reflex (H reflex) and tendon reflex (T reflex) in the soleus muscle. Training caused a 30.8% (P < 0.01) increase in the maximal ankle dorsiflexion. This improved flexibility was associated (r(2) = 0.88; P < 0.001) with a decrease in muscle passive stiffness and, after the first 10 sessions only, with a small increase in passive torque at maximal dorsiflexion. Furthermore, both the H- and T-reflex amplitudes were reduced after training, especially the latter (-36% vs. -14%; P < 0.05). The MVC torque and the maximal rate of torque development were not affected by training. Although the changes in flexibility and passive stiffness were partially maintained 1 month after the end of the training program, reflex activities had already returned to control levels. It is concluded that the increased flexibility results mainly from reduced passive stiffness of the muscle-tendon unit and tonic reflex activity. The underlying neural and mechanical adaptation mechanisms, however, showed different time courses.

Quantifying the passive extensibility of the flexor pollicis longus muscle in people with tetraplegia

“…33,34 In the clinical setting, these two passive mechanical properties of muscles are best reflected by torque-angle curves. [10][11][12][13][14][15][16][17] Although more than one soft tissue structure spans a joint, the torque-angle curve of a joint can be used to primarily reflect the passive mechanical properties of an overlying multiarticular muscle (such as FPL muscle) when this muscle primarily restricts joint movement. Therefore, provided the FPL muscle is placed at a stretch by positioning the wrist, MCP and IP joints in full extension, the torque-angle curve of the CMC joint will primarily reflect the passive mechanical properties of the FPL muscle.…”

“…[10][11][12][13][14][15][16][17] Clinical assessment tools have been designed using these principles to measure the extensibility of muscles such as the plantarflexor muscles, [18][19][20] hamstring muscles, 21,22 and extrinsic finger flexor muscles. 23 However, no equivalent device to measure the extensibility of the FPL muscle has been described.…”

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

“…Normally, there are three main mechanisms used to explain an increase in muscle length: sarcomerogenesis [24,25], increase in stretching tolerance (increase in passive torque at end ROM) [26,27] and decrease in MTU stiffness [28].…”

“…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.…”

The Effect of Static Stretching in Agility and Isokinetic Force at Football Players

“…Peak torque is an absolute value (Kowalski, 2003). Static Stretch The technique of lengthening a muscle group by slowly moving a joint to its maximal range of motion and maintaining the position for a period of time (Guissard & Duchateau, 2004).…”