Neural activation of the triceps surae is impaired following 2�weeks of immobilization

Abstract

The purpose of this study was to investigate the effect of 2 weeks of ankle joint immobilization on triceps surae neural activation, with particular emphasis on the potential differences between the monoarticular soleus and the biarticular gastrocnemius muscles. Seventeen male volunteers were divided into the immobilized group (IG, n = 8) and the control group (CG, n = 9). Elastic adhesive bandages and an ankle stabilization orthosis were used to immobilize the ankle joint only. The plantar flexor torque obtained during maximal voluntary contractions (MVC) and after single, paired and tetanic stimuli applied at rest was measured. The associated EMG activity from the soleus and gastrocnemius muscles was also recorded, and their activation levels were estimated by means of the twitch interpolation technique. After immobilization, triceps surae maximal voluntary torque significantly decreased by 17% (P < 0.001). Strength losses were accompanied by a decrement in activation level (-6%, average of the three techniques used) and in maximal 100 Hz tetanic force (-11%). A significant decrease in the soleus (-22%, P < 0.05) but not in the gastrocnemius EMG activity, normalized to respective M-waves, was also found. It was concluded that the reduced voluntary torque output after immobilization could be attributed to both muscular and neural alterations. These latter selectively involved the monoarticular soleus muscle, while neural drive to the biarticular gastrocnemii, which had not been immobilized in their function as knee flexors, was preserved.

The Effect of Intense Interval Cycle-training on Unloading-Induced Dysfunction and Atrophy in the Human Calf Muscle

“…The results of the present study agree with those of prior ULLS studies (Clark et al, 2006;de Boer et al, 2007;Seynnes et al, 2010) in that we also found no significant change in central activation (pϭ0.085). Hence, the changes in maximal activation of planter flexor muscles following "ULLS" seem at odds with what has been observed in the aforementioned unloading or disuse paradigms (Duchateau, 1995;Lambertz et al, 2001;Kawakami et al, 2001;Gondin et al, 2004).…”

“…Regarding activation capacity, a decrease has been observed consistently after spaceflight (Lambertz et al, 2001), bed rest (Duchateau, 1995;Kawakami et al, 2001), or casting (Gondin et al, 2004). On the other hand, in all investigations utilizing the "ULLS model," the decrease in voluntary activation observed after ULLS failed to reach significance (Clark et al, 2006;de Boer et al, 2007;Seynnes et al, 2010).…”

Achilles tendon vibration-induced changes in plantar flexor corticospinal excitability

“…In early stages of immobilization, reduced neural drive accounts for a large portion of the decrease in plantar flexor strength loss (Duchateau 1995;Gondin et al 2004); therefore, it is important to develop effective countermeasures to neuromuscular deconditioning. With both potential ipsilateral and contralateral effects, a tendon vibration program might be beneficial for individuals who are hypoactive or immobilized, and not candidates for whole-body vibration.…”

Median Frequency Analysis of Shoulder Muscles Using EMG Power Spectrum Analysis After Rotator Cuff Repair

“…So, after repair, patients need to maintain about six-week fixation using ultra-sling for arms, in order to limit active motion [28]. However, it is said that such a fixation causes muscular activity in muscles surrounding the repaired portion and brings about changes in Cuff Repair [14]. If muscular activity is reduced, it is closely related to muscle fatigue and this affects median frequency value because EMG spectrum can be shifted if there are changes in the width in measuring EMG [29].…”

“…Patients who received a rotator cuff muscle repair indicated that muscular activity weakened in lower extremities even with no weight bearing because the surgical site was fixated and it brought about changes in myotility [14], and Downie and Miller [15] reported that after repair, tendon and muscular atrophy increased the fatigue in the surrounding muscles over time.…”