When you hurt one of your arms, you shouldn’t necessarily stop exercising the healthy arm.
A study at the University of Oklahoma suggests that when you train a single arm (or leg), the muscle nerve fibers in the opposite appendage are stimulated. This means you will still get the benefits of Central Nervous System (CNS) adaptations in an injured limb as long as you train the opposite healthy limb, over a short period of time.
In the study, the participants who exercised one arm for 2 weeks were able to increase the strength in their non-working arm up to 10%.
Similarly, I have written before about the body’s attempts to keep itself in a state of homeostasis.
This means that the body wants to be symmetrical. It wants both arms and legs to have equal strength and size. It doesn’t want any one muscle in the body to become extremely strong or weak relative to the rest of the muscles in the body.
Homeostasis is one fundamental reason that good training routines include at least one exercise to stimulate every muscle in the body. Legs must be worked for the upper body to reach its potential, back must be worked if you want to have a strong bench press, etc…
Keep in mind, this is a short-term study. Exercising a single arm over a long period of time will leave you with a muscle imbalance. If you have an arm or a leg that is laid up for months, it might actually be a bad idea to train the healthy limb too much, as the muscular imbalances that will inevitably occur, could lead to injuries in other areas of the body due to over-compensation.
This has nothing to do with unilateral training, where each limb is trained separately using dumbbells, kettlebells, or odd objects. Unilateral training is great, as long as both sides receive equal stimulation.
Sure, professional athletes rush back from severe injuries in just a couple weeks, but YOU are not a professional athlete.
When recovering from an injury, please use proper rest and recovery methods such as RICE (rest, ice, compression, elevation), physical therapy, rest, foam roller, massage, and rest. If you don’t take care of your injured muscles, you may end up with nagging injuries that could eventually require surgery.
Attempt to give up the instant gratification for long term health. It will be worth it in the long run.