Muscle fitness means having muscles that can lift heavier objects or muscles that will work longer before becoming exhausted. Muscle fitness improves when a person does activities that build or maintain muscles (strength) or that increase how long a person can use their muscles (endurance).

Activities like weight lifting, push-ups, or leg lifts can improve muscle fitness. As muscle fitness increases, most people notice that they can carry heavy grocery bags more easily, pick up children without feeling as much strain, or carry heavy items longer before getting too tired to continue. Having stronger muscles also protects the joints.

Muscles become stronger through a three-step process:

• Stress
• Recovery (rest)
• Repeated stress

When a person exercises against resistance, the muscles are stressed slightly but not to the point of serious damage or injury. When the person rests, the body rebuilds the muscles and the connective tissues between them (joints, tendons, and ligaments) in a way that prepares them for the next time they will be stressed. When the same muscles are stressed again, the process is repeated, and the muscles gradually become stronger.

You can do 8 to 10 muscle-fitness exercises at least 2 days each week. Try to use resistance (such as a dumbbell) that tires out the muscles after 8 to 12 repetitions of each exercise.

To increase muscle fitness, a person can do:

• Basic muscle-conditioning exercises, such as push-ups, leg lifts, sit-ups, squats, and lunges.
• Resistance training with rubber tubing or stretchable bands.
• Weight training with free weights (dumbbells) or weight-training equipment.
• Housework and yard work, such as scrubbing the bathtub, washing walls, or pulling weeds.

If you are worried about how exercise may affect your health, talk to a doctor first to see if it's safe.