Running or hiking can be great ways to build muscle and increase overall endurance. Running is a cardio exercise that requires no equipment or extra expense. Local park trails are wonderful places to start and add a different level of physical activity. Different terrains will help build muscle and strengthen bones.
Running can also be a social activity involving multiple people. Invite friends or family members to join you on runs. Sometimes you will even meet new people along the way, broadening your social circle and improving intellectual/emotional health.
According to the American College of Sports Medicine, spending time running for even just 30 minutes can improve the mood of someone suffering from a major depressive disorder. Running improves sleep, boosts moods, relieves stress, and increases focus. All of which benefits you emotionally and intellectually.