How to maintain strength whilst being injured

“I’ve injured my “insert body part” what can I do?” This is the question most people face when injured and let us firstly state the answer is NOT just rest! The benefits of beginning rehabilitation ASAP on the injured site are clear, but what if I told you that training your uninjured side can result in strength gains on your injured side? Enter the Cross-education effect

Researchers from the University of Copenhagen studied the effects of disuse on muscle strength. This revealed in their younger subjects that two weeks inactivity resulted in a staggering 33% loss in leg strength, leaving them on par with a person who is 40-50 years their senior! If this is not shocking enough, it can take 2-3 times as long to regain this lost strength!

Fortunately, we have something called the cross-education effect that we can take advantage of! The cross-education effect is a phenomenon whereby training one side of the body results in an increased strength of the OPPOSITE side of the body. This effect was first observed and published in the literature over 100 years ago, and since this time there have been hundreds of studies examining this topic.

What sort of gains can we experience from this cross-education effect?

The size of contralateral strength gains varies based on the length and type of training, but a 2018 meta-analysis by Green et al revealed a strength gain of:

• 18% in young, able-bodied adults
• 15% in older, able-bodied participants,
• 29% in a patient population consisting of poststroke, neuromuscular disorders, and osteoarthritis patients.

This is quite staggering considering this represents 52-80% of the gains in the trained limb, and it’s not even being used! These effects do not seem to be limited to a single muscle group or area; benefits have been seen all over the body.

How does it happen, and how can we maximize it?

As yet, researchers haven’t reached a consensus on the exact mechanisms of effect, but the leading theory is that the strength gains on the untrained side are neurally driven. It is theorized that the cross-over effect is perhaps the body’s attempt to strive for symmetry (Hendy et al)

Cirer-Sastre et al in their 2017 study examined training parameters (sets/reps/contraction type) that might maximize the cross-education effect. They found that performing 3-5 sets of 8-15 repetitions of eccentric contractions with rest times of 1-2 minutes between sets, created the greatest change. Leung et al also found that higher-load and more cognitively demanding strength training, such as using a metronome to control movement, increases cross-education.

Potential uses of the cross-education effect

ANY injury that results in an inability to perform your usual resistance training. Some examples of its’ use could include:

1. Shoulder pain, and only able to perform 50% of your usual bench press and overhead press? Switch to dumbbells, continue training the uninjured side at 100%, and do what you can perform on the injured side.
2. Broken leg and in a cast for 6 weeks? Switch to single-leg weights for the uninjured side i.e., leg press, leg extension, leg curl, split squat, calf raise, to slow the decline in strength of the injured leg.
3. Acute flare-up of knee osteoarthritis? Train the other leg to take advantage of a 29% gain!
4. Shoulder or ACL reconstruction? Early in the rehab process whilst not able to do much on the operated side, keep training the opposite side!

Conclusion

• An injury is not an excuse to stop training.
• Do not neglect the uninjured side, use unilateral training to take advantage of the cross-education effect.
• Cross-education can result in a staggering 18-29% gain in strength of the opposite side.
• 3-5 sets of 8-15 reps of eccentric contractions with rest times of 1-2 minutes between sets and using a metronome when performing may result in a greater change.

References

• Carroll, T. J., et al. (2006). "Contralateral effects of unilateral strength training: evidence and possible mechanisms." J Appl Physiol (1985) 101(5): 1514-1522.
• Cirer-Sastre, R., et al. (2017). "Contralateral Effects After Unilateral Strength Training: A Meta-Analysis Comparing Training Loads." J Sports Sci Med 16(2): 180-186.
• Fimland, M. S., et al. (2009). "Neural adaptations underlying cross-education after unilateral strength training." Eur J Appl Physiol 107(6): 723-730.
• Green, L. A. and D. A. Gabriel (2018). "The effect of unilateral training on contralateral limb strength in young, older, and patient populations: a meta-analysis of cross education." Physical Therapy Reviews 23(4-5): 238-249.
• Hendy, A. M., et al. (2012). "Cross education and immobilisation: mechanisms and implications for injury rehabilitation." J Sci Med Sport 15(2): 94-101.
• Hortobágyi, T., et al. (1997). "Greater cross education following training with muscle lengthening than shortening." Med Sci Sports Exerc 29(1): 107-112.
• Latella, C., et al. (2012). "Reduction in corticospinal inhibition in the trained and untrained limb following unilateral leg strength training." Eur J Appl Physiol 112(8): 3097-3107.
• Lepley, L. K. and R. M. Palmieri-Smith (2014). "Cross-education strength and activation after eccentric exercise." J Athl Train 49(5): 582-589.
• Leung, M., et al. (2015). "Motor cortex excitability is not differentially modulated following skill and strength training." Neuroscience 305: 99-108.
• Scripture EW, Smith TL, Brown EM. On the education of muscular control and power. Studies Yale Psychol Lab 1894;2:114-119.
• Shields, R. K., et al. (1999). "Effects of repetitive handgrip training on endurance, specificity, and cross-education." Phys Ther 79(5): 467-475.
• Vigelsø, A., et al. (2015). "Six weeks' aerobic retraining after two weeks' immobilization restores leg lean mass and aerobic capacity but does not fully rehabilitate leg strength in young and older men." J Rehabil Med 47(6): 552-560.