Bodyweight Strength Training

Body weight exercises are an excellent way to improve strength and muscle tone without the use of equipment. Using only your body weight as resistance builds muscle, but only proportional to your own body size. Once you have developed the strength to do more than 12 repetitions in a row of an exercise, hypertrophy (increases in muscle size) slows down, and you begin to develop your muscles' ability to resist fatigue.

Dynamic Movements

Dynamic exercises are exercises where your body moves through its range of motion against resistance. Examples of dynamic exercises include push-ups, crunches and lunges. In dynamic body-weight exercises, the force of gravity against your body is the only resistance. The "concentric" phase of the muscle contraction (muscle shortening, such as the "crunching" phase of a sit-up) is against the resistance of gravity. During an "eccentric" contraction ("recovery phase") resistance comes from controlling how fast your body drops to the bottom of the movement.

Isometric Exercises

Isometric training is when your muscle contracts, but your body doesn't move. Men's gymnastics involve a lot of isometric movements. Planks (balancing face-down at the top of a push-up position) and wall squats (sitting against a wall as if you were in a chair) are examples of isometric exercises. Because isometric contractions only train your muscle to be strong in that exact position, they don't improve strength for dynamic movements. A plank, for example, trains a runner to hold her midsection stiff for a smoother running stride. Wall squats don't improve the power of a runner's stride (a dynamic movement), but can train a skier to hold a tuck for longer.

Plyometrics

Plyometric body weight exercises are explosive movements that improve strength in two ways: by improving neuromuscular coordination (synchronizing the firing of different muscle fibers), and by using tendons like elastics to stimulate stronger muscle contractions. Plyometric exercises should mimic the movements an athlete uses in his sport. For example, basketball players throw weighted medicine balls to improve their throwing power and jump onto a high box to improve their vertical leap.

Functional Strength

Because gravity provides resistance in most daily and sport-specific movements, strength built through body weight exercises is directly applicable to everyday life. This is called "functional strength." For example, the elderly are encouraged to do push-ups so that they will have the strength to break a fall. A rock climber uses a pull-up like motion to pull herself from hold to hold. With exercise machines, muscles are isolated in an unnatural way that doesn't mirror everyday movement.

Increasing the Difficulty

Maximum strength only improves when a muscle reaches failure before twelve repetitions. To continue to build muscle, you must increase the exercises' difficulty as your muscles adapt to the load. You can add more weight with dumbbells or a weighted vest, but changing the rhythm of the movement also challenges muscles. Muscles work harder when you slow the movement down because there is less momentum to help them through the movement. Extending the "down phase" of the motion (eccentric contraction) especially stimulates muscle growth.