It's inevitable that an athlete will become injured at some point during their season. Which begs the question: how should their training be adapted during the rehab process. My overall philosophy is that we should aim to keep the goal as close to the goal as possible, and this means training at a high level of possible during the rehab process. In the case of injury athletes should continue to train as much of the whole body as possible, including the un-injured limb. This means that if you've sustained a minor or major knee injury to one leg, then you should continue to train the other leg. As I will explain later, it will help rehab outcomes. No, you don't need to worry about one side 'getting too jacked'!
I don't just think that others should do this, I've lived it and experienced myself on 2 occasions. The first was in 2008 when I ruptured my right triceps tendon in a University All-Star showcase game. When I finally had surgery, I was only 10 weeks out from training camp at Acadia, and I knew I had to keep as much strength as possible. I worked with my strength coach and loaded up the rest of my body and my healthy side. I was able to return to play at just over 12 weeks, and was playing professionally a year later. In my second year in the CFL, I dislocated my wrist which required surgery and immobilization. I continued to train with a cast on and returned in 9 weeks (still had to play with a cast), but kept my starting spot.
In most situations, athletes will cease their training until their whole body is healthy enough to return to training. the downside of this is that while one side is getting healthier, the other side is getting weaker. This is why that in ACL rehab scenarios, an individual is 230% more likely of tearing their other leg. If you became injured, there could have been a limitation to begin with! Letting the unaffected side detrain also makes it challenging to use bilateral comparisons as a marker of symmetry. If the injured side gets within 10% of the unaffected side (that significantly detrained) is that really a good thing?
This is why my philosophy has been not to treat our athletes in a conventional way of either taking training off, or just doing the opposite hemisphere of training (eg. if lower body is injured, only doing upper). We want them training at the highest level possible at all times. In terms of keeping the goal as close to the goal as possible, that means continuing to train the un-injured limb. The primary reason for this is what is known as cross-transfer, or contralateral training, but most commonly referred to in the research as cross-education (Cirer-Sastre, R, et al, 2017). What this means is that even though the injured isn't physically trained, there are physical improvements that are transferred over from the side of the body that is being trained.
Benefits of contralateral training :
1. Increase in strength of untrained limb
Early research found grip strength improvements were 43% of the trained side (Scripture, 1894), while most recently in 2004 (Munn) looked at all existing research to find that the average improvement is 7.8% in the injured limb when only training the unaffected side.
2. Less atrophy of inactive muscle.
Hendy et al. (2012) found that the injured side actually experienced less muscle wasting during the rehab process, which speaks to the nervous system signals that could have 'spilled over' from the working side to stimulate the 'dormant' side. This would certainly be beneficial to help speed the process up of improving strength when people are able to return.
3. Improvements in range of motion.
Magnus et al. (2013) found that with a simple hand grip strength protocol, range of motion was 30% greater was found between experimental and control group at 12 weeks post injury.
4. Maintains strength in the rest of the body.
As mentioned above, you can't let the unaffected parts of your body detrain. Whole body performance needs to be maintained, or improved for all athletes, all parts of the year.
5. Mental benefit.
Being injured is one of the hardest things for an athlete to go through. Being able to continue to be with their teammates is a big part of training, and becomes the only 'team thing' they do. They also get to maintain a sense of control, and that they're able to actively work towards their rehab goal.
6. .Extra rehab exposures.
One thing we add in for our injured athletes are the exercises given by therapists. We know that athletes aren't always the most compliant when it comes to their rehab exercises. By having them do their rehab exercises more often, it can help the rehab process. We do this by making any 'core' or 'corrective' exercises in our program to become rehab exercises.
How does it work?
Changes are more neurological than anything, and can happen because its the brain and central nervous system that are in control of muscle contractions. As we know the brain has two hemispheres, which control the opposite sides of the body, so it is thought that some of these signals 'spill over' from one side of the brain to the other side. These changes at the nervous system level is likely why very little hypertrophy effects have been noted. The main mechanism that is suggested for this is the cross-activation model and the bilateral access model. These models suggest that the neural adaptations extend to the opposite side of the body, almost like it leaks from one side of the brain to the other side of the CNS. The bilateral access model suggests that the motor schema or adaptation created on one side of the brain is able to be retrieved like a file by the other side of the brain when eventually called upon. A final model suggested to explain this is the mirror neuron system that shows that even just visualization of a movement can make a change. The bottom line is that it appears when you train one side of the body, there are residual signals that carry over to the untrained side.
Practical applications
If contralateral training can increase improvements in range of motion, decrease muscle atrophy, increase strength in the affected limb, then it will allow for a quicker and more effective rehab time which is positive for the athlete. From a psycho-social perspective, it keeps the athlete engaged with the process and involved with the team. There are a couple considerations for contralateral training. Primarily if you're going to train the unaffected side, then the athlete should look to train aggressively since only a percentage of the strength gains on one side will be seen on the other. Another method shown to be effective in the research is the use of fast eccentrics (3 sets of 10). This can be done using a flywheel type of training device if you have it. There's a high neurological demand to this type of activity which would explain its benefit. Outside of the weightroom this could mean to continue to do plyometrics on the good leg, high velocity overcoming isometrics against a wall, or medicine ball work for the upper body. The biggest take away should be to continue training and keep the majority of your program the same as it was before. It will help your athletes come back faster and be more resilient when they do get back.
References
Cirer-Sastre, R., Beltran-Garrido, J. V., Corbi, F. (2017) Contralateral effects after unilateral strength training: a meta-analysis comparing training loads. Journal of Sports Science and Medicine. 16, 180-186.
Hendy, A.M., Spittle, M., and Kidgell, D.J. (2012) Cross eductation and immobilisation: mechanisms and implications for injury rehabilitation. Journal of Science and Medicine in Sport, 15, 94-101.
Magnus, C., Arnold, C. M., Johnston, G., Dal-Bello Haas, V., Basran, J., Krentz, J., & Farthing, J. P. (2013). Cross-education for improvising strength and mobility after distal radius fractures: A randomized controlled trial. Archives of Physical Medicine and Rehabilitation, 94(7), 1247-1255.
Munn, J., Herbert, R. D., & Gandevia, S. C. (2004). Contralateral effects of unilateral resistance training: a meta-analysis. Journal of Applied Physiology, 96, 1861-1866.