Question

And active student injured his knee playing basketball and has been advised by his doctor to avoid impact activities that cause heavy force on his bones which is the most effective activity he can do to maintain his stem ninja without further injury

Answer 1

The most effective activity he can do to maintain his stem ninja without further injury is swimming.
Swimming is a resistance exercise, similar to weight-lifting. However; unlike weight-lifting, swimming places almost no stress on your joints and bones. Therefore; not only does swimming work the muscles but it doesn't have some of the negative impacts that lifting weights has.