Strength training the free limb attenuates strength loss during unilateral immobilization

Abstract

The objective was to determine if strength training the free limb during a 3-wk period of unilateral immobilization attenuates strength loss in the immobilized limb through cross-education. Thirty right-handed participants were assigned to three groups. One group (n = 10) wore a cast and trained the free arm (Cast-Train). A second group (n = 10) wore a cast and did not train (Cast). A third group (n = 10) received no treatment (control). Casts were applied to the nondominant (left) wrist and hand by a physician. Strength training was maximal isometric ulnar deviation (right hand) 5 days/wk. Peak torque (dynamometer), electromyography (EMG), and muscle thickness (ultrasound) were assessed in both arms before and after the intervention. Cast-Train improved right arm strength [14.3 (SD 5.0) to 17.7 (SD 4.8) N x m; P < 0.05] with no significant muscle hypertrophy [3.73 (SD 0.43) to 3.84 (SD 0.52) cm; P = 0.09]. The immobilized arm of Cast-Train did not change in strength [13.9 (SD 4.3) to 14.2 (SD 4.6) N x m] or muscle thickness [3.61 (SD 0.51) to 3.57 (SD 0.43) cm]. The immobilized arm of Cast decreased in strength [12.2 (SD 3.8) to 10.4 (SD 2.5) N x m; P < 0.05] and muscle thickness [3.47 (SD 0.59) to 3.32 (SD 0.55) cm; P < 0.05]. Control showed no changes in the right arm [strength: 15.3 (SD 6.1) to 14.3 (SD 5.8) N x m; muscle thickness: 3.57 (SD 0.68) to 3.52 (SD 0.75) cm] or left arm [strength: 14.5 (SD 5.3) to 13.7 (SD 6.1) N x m; muscle thickness: 3.55 (SD 0.77) to 3.51 (SD 0.70) cm]. Agonist muscle activation remained unchanged after the intervention for both arms [right: 302 (SD 188) to 314 (SD 176) microV; left: 261 (SD 139) to 288 (SD 151) microV] with no group differences. Strength training of the free limb attenuated strength loss in the immobilized limb during unilateral immobilization. Strength training may have prevented muscle atrophy in the immobilized limb.

Functional and morphological effects of resistance exercise on disuse-induced skeletal muscle atrophy

“…Among the models of RE most commonly used in disuse atrophic states are flywheel (30)(31)(32)(33)(34), vascular occlusion (VO) (35), and conventional RE consisting of concentric/eccentric or isometric muscle actions (20,36,37). It is important to emphasize that the composition of these types of RE differs in terms of intensity and volume.…”

“…After the immobiliza-tion period, the lean mass of the individuals presented a reduction of about 5%, which was restored after 6 weeks of RE. Recently, Farthing et al (20) assessed whether unilateral isometric RE on the upper dominant limb could mitigate the loss of strength in the immobilized limb (crosstraining) for 3 weeks and observed maintenance of the basal isometric strength of the contralateral limb. Trappe et al (37) conducted a study to assess structural and functional changes of skeletal muscle in individuals for 6 months of a space mission (lack of gravity).…”

“…Although it is questionable whether such intensity should be applied to an immobilized limb, the training protocol began 2 weeks after immobilization, a fact that can be interpreted as a limitation since the return of the body overload during this period may have contributed to rehabilitation. Other human studies involving isometric (20) and dynamic (37) RE did not report the training intensity. In an experimental model, Haddad et al (52) and Adams et al (53) reported that the protocols used promoted less than 25 and 30% of peripheral fatigue in each session, respectively.…”

“…Worthy of note, the RE variables are approached separately in order to discuss the effectiveness of their characterization according to the model of RE. It is important to note that short periods of immobilization may result in significant strength loss but may not induce significant muscle atrophy (20). Thus, for this review we selected studies whose experimental design of muscle disuse resulted in significant skeletal muscle atrophy and loss of muscle function (strength).…”

Interhemispheric interactions associated with unilateral ballistic motor tasks

“…For the purpose of this thesis, the terms "cross education" and "cross limb transfer" are used interchangeably to describe the phenomenon. Cross education has been demonstrated in a number of tasks such as strength training (Adamson, et al, 2008;Farthing et al, 2009;Pearce et al, 2013), fast speed (ballistic) contractions (Carroll, et al, 2008;Hinder et al, 2013b;Lee et al, 2010), pegboard dexterity tasks (Schulze et al, 2002), sequential finger movements (Shea et al, 2011;Wiestler et al, 2014), force field perturbations (Criscimagna-Hemminger et al, 2003;Galea et al, 2007) and visuomotor distortions (Carroll et al, 2014;Sainburg & Wang, 2002;Taylor et al, 2011;Wang & Sainburg, 2009). The exact mechanisms for cross education are still not well understood, but presumably reflect the sharing between both limbs of specific information acquired by the trained limb.…”