Injury rehab: talking at cross purposes!

Circles = eccentric training group; crosses = concentric training group; triangles = control group (no training). The control group lost 15-20% maximum force production in the immobilized arm. The concentric group gained up to 10% maximum force in the trained arm and lost only 5-10% in the immobilized arm. The eccentric group gained 10-30% maximum force in the trained arm and actually gained around 5% in the immobilized arm!

When it came to the protective effects against muscle damage, eccentric training was significantly more effective than concentric training and the control group in all measures. The concentric training program was also significantly more effective than the control group in all measures. This means that even though no exercise was performed with the immobilized arm, it was protected against the damaging effects of exercise by training the non-immobilized arm either eccentrically or concentrically. Pretty amazing!

Practical implications for athletes

When injury strikes, it appears that training the non-immobilized limb has a major impact on the structure and function of the immobilized limb. It reduces losses in strength, it reduces losses in size, and it reduces losses in the ability to prevent muscle damage following intense exercises. These are all benefits that are of tremendous value to athletes of all types. Importantly, these effects appear to be magnified by eccentric training compared to eccentric training. In times where one limb is out of action, it looks like there’s a lot that can be done to reduce the negative impact of such a situation!

For athletes who get injured, a setback is inevitable. However, effective strategies exist to minimize how large that set back is going to be. By training the uninjured limb, it’s very likely that you will be able to reduce the impact of a lack of training on the uninjured limb. Pretty cool! Even better, it doesn’t take a lot of time or effort. All it takes is a commitment to continuing to train, and potentially some creativity as to how you can maintain this training effect if one limb is out of action.

Caveats

There are some caveats that should be considered. It’s important to note that this study was just performed on the arms. However, while it can’t be definitively concluded that similar effects would be found in the legs, there’s no reason to expect that wouldn’t be the case. Secondly, these subjects were untrained, which means two things. First, they were unaccustomed to the training which likely resulted in a more robust training response due to the novelty of the intervention. Secondly, because they weren’t training, they didn’t have any training-induced adaptations to lose, likely limiting how much of a loss of function they experienced. That being said, it’s likely that the effect would still be present in a trained athlete, although the magnitude of the effect would likely be less. 

Despite these potential limitations, when you’re injured, any way to minimize the loss of training adaptations is well worth the effort. And even if the results aren’t as significant as those in this study, if you’re injured, you’ll have time to do something, so you might as well do what you can! Just as importantly, continuing to feel like you’re doing something to help your situation will do wonders psychologically, both during the injury period and when ramping back up to speed. For all these reasons, any progress that can be maintained is a worthy time investment.

When it comes to the strength, it appears that eccentric training is particularly effective relative to concentric training. When possible, emphasize eccentric training. However, concentric only was still effective at mitigating losses of function and structure, just not as effective as eccentric only training. If for some reason eccentric training is not an option, it’s still valuable to perform some sort of training, even if it’s concentric only training. Training the uninjured limb in some manner will likely help you retain more of your function.

Another key takeaway is that it doesn’t take much training to make an impact. Over a 3-week period, the subjects only performed six sessions. Each session only consisted of 5 sets of 6 repetitions. This is an incredibly small time commitment considering the potential benefits. Of course, you may want to perform multiple exercises or multiple types of activities depending on your injury, but it would still represent a minimal time investment, certainly when in comparison to a full training load.

Now, if you’re an endurance-based athlete, you might be quick to dismiss these findings as irrelevant because you’re not much interested in muscle strength and size. However, that’s a foolish outlook. First of all, regardless of your event, muscle strength and size do matter. While you may not be looking for giant muscles, any loss of muscle size due to disuse will need to be re-gained, so you might as well prevent that loss. Secondly, consider the concept demonstrated- continuing to exercise the unaffected limb allowed for a reduction in loss of the immobilized limb. While strength training was the stimulus in this study, it stands to reason that a similar result could be possible with endurance training as well. It may be that the magnitude of the effect is less, but as demonstrated above, any benefit is worth the effort.

Reference

1. Med Sci Sports Exerc. 2023 Feb 20.  doi: 10.1249/MSS.0000000000003140. Online ahead of print