Define and describe the different types of physical activities (aerobic, muscle strengthening, bone strengthening, and balance and stretching).

Aerobic -relating to or denoting exercise that improves or is intended to improve the efficiency of the body's cardiovascular system in absorbing and transporting oxygen.
Muscle strengthening- the ability of a muscle group to develop maximal contractile force against a resistance in a single contraction.
Bone strengthening- make bones grow and get stronger through an impact (often with the ground) or tension force that promotes bone growth and strength.
Balance- an even distribution of weight enabling someone or something to remain upright and steady.
Stretching- straighten or extend one's body or a part of one's body to its full length, typically so as to tighten one's muscles or in order to reach something.