The body might be able to physically perform 100 squats a day, but the question you then need to ask is whether that is going to stimulate muscle growth and is it going to have an adverse affect on your joints in the process. I’ve read plenty of information that suggests it’s better to train muscles with a couple of warm up sets and then complete 1-2 working sets on those muscles to absolute failure in order to stimulate muscle growth, growth of which then happens over the following days. This has worked well for my training. It depends what your goals are, or course, but if it’s to grow the muscles, why overtrain them unnecessarily, which can potentially lead to more chances of damaging your knees (or other joints) in this instance, when you can stimulate the muscle growth with a maximum effort load, say on a leg extension machine in this instance, then rest with a good diet and sleep and then return again to that exercise in 4-5 days time and repeat. Personally, I think it’s a fools errand doing things like 100 lunges and pushups a day. Each to their own, however.