There are four commonly used methods of applying resistance to develop strength and endurance.
• Body Weight Resistance
Many different techniques can be used to develop skeletal muscle fitness without relying on resistance equipment. Most of these methods use part or all of your body weight to offer the resistance during exercise. While these techniques are not as effective as external resistance in developing muscular strength, they are quite adequate for improving general muscular fitness. Activities such as sit-ups, push-ups, and pull-ups use both concentric and eccentric muscle actions. These types of resistance activities are convenient – no special equipment is needed – and are generally sufficient to improve muscle tone and maintain the level of muscular strength created by this type of overload. But they will not help you to make significant strength gains.
• Fixed Resistance
Fixed resistance exercises provide a constant amount of resistance throughout the full range of movement. Barbells and dumbbells provide fixed resistance because their weight (amount of resistance) does not change as you exercise. The advantages of fixed resistance exercise include the portability and low cost of barbells and dumbbells, the common availability of fixed resistance exercise machines at university recreation/fitness facilities and health clubs, and the existence of numerous exercises designed to strengthen all the major muscle groups in the body.
• Variable Resistance
Whether found at a health club or in your home workout area, variable resistance equipment alters the resistance encountered by a muscle at various joint angles so that the effort by the muscle is more consistent throughout the full range of motion. Variable resistance machines are typically single-station devices (e.g., Nautilus, Hammer Strength’ but some have multiple stations at which muscles of the upper and lower extremities can be exercised (e.g., Soloflex). While some of these machines are expensive and permanently placed, other inexpensive, portable forms of variable resistance devices are sold for home use.
With accommodating resistance devices, the resistance changes according to the amount of force generated by the individual. There is no external weight to move or overcome. Resistance is provided by having the exerciser perform at maximal level of effort, while the exercise machine controls the speed of the exercise and does not allow any faster motion. The body segment being exercised must move at a rate faster than or equal to the set speed to encounter resistance.