Cross-education attenuates muscle weakness and facilitates strength recovery after orthopedic immobilization in females: A pilot study

Abstract

This pilot study consists of a two-phase intervention to examine the effectiveness of unilateral resistance training to mitigate the negative consequences of immobilization and expedite the restoration of muscle strength and size following a period of retraining. Ten females were randomized to a unilateral training (TRAIN, n = 6) or control (CON, n = 4) group. During Phase 1, all participants wore an arm sling for a total of 4 weeks on their non-dominant arm. This phase required the TRAIN group to perform unilateral resistance training with the non-immobilized arm while the CON group did not. Phase 2 commenced thereafter and consisted of 4 weeks of bilateral resistance training for both groups. Outcome measures of neuromuscular function and muscle size were assessed at baseline and after each phase, with neuromuscular function quantified by maximal dynamic and isometric strength alongside electromyographic responses and muscle size measured using ultrasonography and regional lean mass via DEXA. Unilateral training of the non-immobilized arm during Phase 1 attenuated dynamic (p < 0.05; g > 1.2), but not isometric (p > 0.40; g < 0.095), strength loss following immobilization and showed large effects for improving the recovery of strength after retraining. Similarly, the imaging data show the relative changes in muscle size and regional lean mass of the non-dominant arm favor TRAIN. Although the small sample prevents definitive conclusions, our study suggests resistance training of the non-immobilized arm attenuates muscle weakness and atrophy for the contralateral, immobilized arm during immobilization and facilitates their recovery following retraining.

Keywords: early medical intervention; physical therapy; resistance training; sports medicine.

FIGURE 1

The CONSORT flow diagram for the complete trial is shown.

FIGURE 2

The relative changes in the immobilized arm for shoulder press 1RM (a), biceps curl 1RM (b), biceps curl 1RM EMG_AMP (c), elbow flexor MVC EMG_AMP (d), handgrip MVC strength (e), and elbow flexor MVC strength (f) from baseline for TRAIN (circles) and CON groups (triangles) are shown. The large symbols represent the group mean, with the standard deviation shown in the gray shading, along with the individual responses after Phase 1 (immobilization) and Phase 2 (retraining).

FIGURE 3

The relative changes in biceps brachii CSA (a), biceps brachii cEI (b), regional lean mass (c), and total body BF% (d) from baseline for TRAIN (circles) and CON groups (triangles) are shown. The large symbols represent the group mean, with the standard deviation shown in the gray shading, along with the individual responses after Phase 1 (immobilization) and Phase 2 (retraining).