During exercise we put extra stresses and strains on our muscles. When we do this we create tiny tears in the muscle fibres, and we often feel this a soreness a day or two later (a phenomenon known as “DOMS”, or Delayed Onset Muscle Soreness).
During rest, between bouts of exercise, our bodies will go about repairing these micro-tears, and this most often occurs during our sleep. In the process of repairing, out body “remembers” that a certain level of stress/effort caused the muscle fibre to break last time round, and will repair it to be more resilient – stronger – next time.
Thus, when it comes to getting stronger, that actually happens when we are asleep or resting, and not when we are exercising!
So – don’t overdo it, you won’t give yourself a chance to get stronger, and are more likely to injure yourself as a result.