Strength and endurance are inter-related but different concepts. Muscle endurance is the ability of a muscle to produce sub-maximal force repeatedly over time. Muscle strength is the ability of the muscle to exert maximum force against resistance.

Endurance depends extensively on strength. If the muscles are weak, they will not be able to repeat an action as often as needed. Based on the way that strength and endurance are developed, some basic principles have been formulated to guide exercise prescriptions.

Endurance is developed, at best, by the number of repetitions you can perform against a sub-maximal resistance or by the length of time you can maintain a muscle contraction or simply assuming a change in your body position and maintaining it in that position during a physical activity. The number of sit ups you can do, the number of times you are able to lift a 20-pound dumb-bell or the length of time you can maintain yourself in the chin-up position are all good indicators of your level of endurance. Endurance is developed through your exercise routines. However, a high degree of endurance in one aspect of the body is not an indication of high endurance in all other areas.

A sample of some simple exercises will give you a profile of endurance exercises for the upper and lower body and abdomen. These are exercises of low-level organisation that can be done at home with simple household equipment and a partner.

Step-ups/bench jump

Use a sturdy support base, about 16 inches high and step up and down as many times as you can. If you are enjoying fairly good physical fitness and your joints can tolerate the dynamics of jumping, then jump up and down as many times as you can. If you are counting the number of repetitions, each time both feet return to the floor is one repetition.

Modified dip for men

Using three stable chairs as support, place each hand on a chair with your fingers pointing forward and your feet on the other to suspend your self between the chairs. Bend your elbows to lower yourself to a 90-degree angle at your hips then return to the starting position. Do as many repetitions as you can.

Modified push up for women

Lie face down and bend your knees so that your feet are up in the air. Hands on the floor beside your shoulder, fingers pointing forward, lower your body to touch your chest to the floor for each repetition. Repeat as many times as you can.

Bent-leg curl

Lie on your back with your knees bent at a 100-degree angle.

Feet on the floor, cross your arms in front of your chest with hands on opposite shoulders. Raise your head off the floor and place your chin on your chest. Return to the starting position but keep the back of your head off the floor and your hands on your shoulders.

Abdominal crunch (for those unable to do bent-up curl)

Lie on your back with knees bent at a 100-degree angle, legs slightly apart, feet on the floor and held in place. Have your arms stretched out by your sides with palms on the floor. Raise your head above the floor until your chin is about two inches away from your chest while you slide your hand along the floor. Return to the starting position.

Dr Kenneth Gardner is an exercise physiologist at Holiday Hills Research Center; email: yourhealth@ gleanerjm.com.