It’s frustrating when you injure an arm or a leg and can’t train that side for a few weeks or even months but it’s a fact of life. Injuries need time to heal or you risk greater injury and time away from training. When you take long breaks from training, you risk the loss of strength and muscle mass, especially if it is sustained. Your aerobic capacity may also decline while nursing an injury for a long period. In some cases, you can modify the exercises you do, but what do you do if you can’t use one arm or leg at all? All is not lost! If you’re forced to stop training one side, there’s a reason to keep training the other.
The Benefits of Cross Education Can Work in Your Favor
According to a study conducted by researchers at Edith Cowan University, training the limb on one side of the body helps prevent muscle loss in the same limb on the other side. They discovered that when subjects injure an arm, training the healthy arm helps reduce muscle atrophy and loss of strength in the injured arm.
For the study, researchers immobilized one arm of the participants’ for at least eight hours per day for one month. They divided the 30 subjects into three groups and asked them to follow one of three protocols training only the “good” arm:
- Both concentric and eccentric exercise
- Eccentric exercise only
- No exercise at all
Concentric exercise is the portion of a movement that emphasizes the shortening of a muscle, for example, bringing the weight toward the shoulder with a biceps curl. Eccentric involves elongation of a muscle under tension and corresponds to the lowering phase of a biceps curl where you bring the weight back to the starting position. Eccentric contractions create more muscle damage and can lead to greater muscle hypertrophy. The participants did their designated exercise using the arm that wasn’t immobilized.
The results? The participants who did the eccentric exercise using a heavy weight on their mobile arm developed greater muscle strength in their immobilized arm and lost less muscle tissue in the arm that was immobilized. Pretty amazing if you think about it! Training one arm eccentrically built strength and led to less muscle wasting of the opposite immobilized arm.
What does this mean? These findings suggest that training an uninjured muscle eccentrically may maintain muscle size in the opposite, injured arm, and even lead to strength gains in that arm. It’s an example of a cross-training effect, training one side can trigger strength gains in the opposite side even if that side doesn’t train or move.
The Cross-Training Effect
The cross-training effect is sometimes called “cross-education” and it refers to the transference of the training effects from one limb to the limb on the opposite side and it seems to apply to many muscle groups, including muscles in the arms legs, and even smaller muscles like those in the hands. If you look at the results of multiple studies, gains from cross education are modest but significant. You can increase the strength of an untrained limb by up to 11% by training the opposite limb, even if the first limb is immobilized. Of course, you’ll make greater gains on the side you train but some of those benefits will transfer to the immobilized or injured limb. Gains on the untrained side will be about half those of the trained side but that’s not bad when you’re not able to train!
This is good news if you sustain an injury on one side. For example, you might strain or even tear an Achilles tendon running and not be able to strength train on that side for weeks or longer, yet you might still be able to train the opposite limb and preserve strength and reduce muscle loss. If you don’t train at all, studies show you can lose up to 33% of the strength in a limb from inactivity. Then, you have the task of recouping that lost strength and mass. Some form of training is better than being inactive. Too much sitting when you’re injured increases the risk of a blood clot and is harmful to your metabolic health. You might also gain a few pounds of body fat from being sedentary. Training the good side is a chance to preserve muscle mass and strength and stay active.
The Bottom Line
If you’re injured, be cautious about your training to avoid doing further damage and extending the time you can’t train, but if at all possible, keep training the opposite side to reduce muscle atrophy and wasting. It could save you from having to start at square one building muscle size and strength again.
Also, if your lower body is injured, continue to work your upper body using weights of some form of resistance. Likewise, if your upper body is injured, work your lower body by doing cardio or lower bodyweight training. Work with what you have. Moving your body, in some way, when you’re injured will also help you maintain sanity too. If you have a serious injury though, be sure to follow the advice of your health care provider, but they’ll likely want you to do some form of movement too. Do it safely but keep moving!
- Padulo J, Laffaye G, Chamari K, Concu A. Concentric and Eccentric: Muscle Contraction or Exercise? Sports Health. 2013;5(4):306-306. doi:10.1177/1941738113491386.
- Omar Valdes, Carlos Ramirez, Felipe Perez, Sebastian Garcia‐Vicencio, Kazunori Nosaka, Luis Penailillo. Contralateral effects of eccentric resistance training on immobilized arm. Scandinavian Journal of Medicine & Science in Sports, 2020; DOI: 10.1111/sms.13821.
- Lee, M and Carroll, T. Cross Education: Possible Mechanisms for the Contralateral Effects of Unilateral Resistance Training. Sports Med. 37(1): 1-4, 2007.
- Carroll, T, Herbert, R, Munn, J, Lee, M, and Gandevia, S. Contralateral effects of unilateral strength training: evidence and possible mechanisms. J Appl Physiol 101: 1514-1522, 2006.
- J Appl Physiol (1985). 2006 Nov;101(5):1514-22. doi: 10.1152/japplphysiol.00531.2006.
- gov. “Sports Injuries”