The health benefits of strength training (as with most forms of regular exercise) are frequently quoted as providing increased lifespan, better ageing, disease resistance etc. However, it is certainly not the case that elite athletes live the longest, and many seem to do harm to their overall health by pushing themselves as hard as they do. Logically there must be a point at which an individual is maximising the health benefits of their training, beyond which they no longer improve their overall health and may eventually start to damage it if they push significantly harder.
To put this specifically into the context of strength training, is there a good understanding of the level of strength, or the rate of gain, at which an individual can say they're doing as much as can benefit their health? Would this be a fixed level of strength which just has to be maintained, or a constant rate of gain which represents the optimal level of stress on the body? What is known about this at the moment?