So basically, the current situation is "this training is way too harsh! At this rate, squad 402 will fail and drop out! I better do something!" And that something is... even harsher training on top of the already too harsh training? How does training them even harder save them from too harsh training, especially since it will presumably be on top of the currently too harsh training?
This manga's message seems to be "if your willpower is strong enough, then your body will keep moving no matter how much overexertion you put your body through!" What would actually happen with significant overexertion would be tearing or overstretching in muscles, tendons, and ligaments, which actually weakens the body and can even have permanent damage to your muscles. Pretty much all training regimes have limits and rest days for a reason.