A question I get asked a lot in clinic, especially by athletes, is whether it's OK to keep going if you feel pain.
Conventional wisdom stated that you should rest at the first sign of any pain/injury although research over the last few years has demonstrated consistently that that’s rarely the best course of action. By continuing to use muscles/joints/tendons you are stimulating blood flow and allowing the bodies own healing mechanisms to operate effectively. Of course there’s a limit to this and pushing a damaged tendon too hard may well lead to further damage and longer recovery time.
A classic example is tennis elbow (or lateral epicondylitis), the tendon is damaged and it can be really irritated when you engage the muscle by gripping, I see it a lot in climbers. The temptation is to completely rest the wrist and forearm but in my clinical experience even if it causes short term pain, people who carry on using the muscles tend to heal quicker in the long run. A degree of common sense is helpful and it’s best to use lighter weights than normal until it’s completely recovered.
When I get minor running injuries my rule of thumb is that I will carry on running as long as the pain doesn’t get significantly worse while I run, the pain doesn’t effect the way that I run (eg landing on the outside of the foot as the inside hurts to land on) and I don’t need to take painkillers to keep going (honestly, you’d be surprised ;)
There are always exceptions, such as stress fractures where it’s vital to take pressure off the bone to allow it to heal. But even in this instance it’s important to keep some pressure on the effecteted area.
So in conclusion, rest is very rarely best but it’s a fine line between stimulating repair and doing too much.