In general, doing challenging sports with Amoxicillin is not advisable. The body is already stressed by fighting the infection and the weakened intestinal flora (as antibiotics also attack good bacteria). Challenging sporting activity puts an additional strain on the weakened immune system and delays recovery. An infection that is carried over increases the risk of late complications such as heart muscle inflammation. In case of doubt, you should ask your doctor what is possible and sensible in your condition.