(04) UNILATERAL TRAINING ACCELERATES STRENGTH RECOVERY FOLLOWING ORTHOPEDIC IMMOBILIZATION

Background: Sport-related orthopedic injuries are one of the most common health issues faced by athletes. These injuries typically affect one side of the body and often result in temporary muscle disuse due to rest or orthopedic immobilization. Despite its necessity, immobilization causes profound impairments in muscle strength. Unilateral training of the uninvolved limb is an emerging paradigm to attenuate the immobilization-induced deficits in neuromuscular function.

Purpose: To determine whether unilateral strength training can attenuate muscle weakness during orthopedic immobilization and expedite the restoration of muscle strength during retraining.

Methods: A randomized controlled clinical trial was performed to examine the time course of muscle strength adaptations in two groups of untrained volunteers during four weeks of immobilization and four weeks of subsequent strength retraining. Both groups underwent orthopedic immobilization by wearing a shoulder sling and swathe on their non-dominant arm for ~≥10 hours/day for four weeks. One group (TRAIN, n = 6) performed progressive unilateral strength training of the free limb throughout the immobilization period. The other group (SLING, n = 4) did not undergo any training during the immobilization period. Following immobilization, both groups underwent four weeks of bilateral strength training to retrain the immobilized arm. The unilateral and bilateral training consisted of biceps curls and shoulder press at ~80%1RM for 3-5 sets of 5-6 repetitions. The training was performed 2x/wk and loading was progressed as tolerated. Maximal muscle strength of the non-dominant (immobilized) arm was assessed via 1-repetition maximum (1RM) testing for shoulder press and biceps curl along with the maximal voluntary isometric contraction (MVC) force of the elbow flexors. Strength measures were collected before immobilization, after the immobilization phase, and after the retraining phase. Separate analysis of covariance tests were performed on each strength measure at post-immobilization and post-retraining with baseline strength as the covariate. Alpha was set at 0.05.

Results: After adjusting for baseline strength, the ANCOVA test revealed significantly (p < 0.05) greater strength values for TRAIN versus SLING for shoulder press and biceps curl 1RM after immobilization and after retraining, but not for elbow flexor MVC force.

Conclusions: These results show that unilateral strength training of the uninvolved arm during four weeks of orthopedic immobilization preserves maximal muscle strength for the immobilized arm and accelerates strength recovery during retraining. The lack of an effect for elbow flexor MVC force likely highlights the specificity of the cross-education effect. PRACTICAL APPLICATIONS: These data have applications for how strength coaches, physical therapists, and athletic trainers manage athletes with unilateral orthopedic injuries. These findings should aid the development of athlete-driven rehabilitation protocols that accelerate the recovery of muscle strength during scenarios in which an athlete is unable to train one limb due to injury.

Acknowledgements: This work was supported by the Texas Christian University Research and Creative Activities Fund.