Chinese kung fu is a large system of theory and practice. It combines techniques of self-defense and health-keeping.
In sports like track and field, ball sports, weightlifting, and boxing, an athlete typically has to retire from full participation in his 30s. Injuries sustained during years of active sport participation at a young age can affect our ability to continue exercising in later life.
In Chinese kung fu however, a distinction is made between “external” and “internal” kung fu. It is said that “In external kung fu, you exercise your tendons, bones, and skin; in internal kung fu, you train your spirit, your qi, and your mind.” And so internal kung fu can continue later in life, when the external body weakens.