A well-rounded fitness program should include cardiovascular and flexibility components, a sound nutritional diet and a strength training program. Most people looking to do resistance training programs will undoubtedly head toward the wide array of exercise equipment and machinery located in most gyms. If your gym has a pool you should consider the benefits of water resistance; including cardiovascular and range of motion benefits. But the pool has so much more to offer. In reality, it is a multidimensional, variable resistance machine.
Water Resistance
As a variable resistance machine, the water allows for three-dimensional movement with a built-in overload factor. You are surrounded by resistance in any direction of movement: horizontal, vertical and diagonal. To increase fitness and function of your musculoskeletal system, the overload principle must be implemented, and the most common overload in strength training is resistance training. Resistance training increases the probability of achieving your weight loss and body image goals, along with an overall fitness benefit.
The physics governing the laws of motion in water include the terms of buoyancy, drag, turbulence and inertia. Water supports the body through buoyancy, and buoyancy counteracts the effect of gravity on the body. At chest height, a body will weigh approximately 35% of body weight, and at shoulder height, this will decrease to 10%. Because of the effect of buoyancy, the compression of joints is decreased, resulting in less joint stress and greater range of motion. The diminished effects of gravity allow for gains in muscle balance and stability.
Although buoyancy and the feeling of weightlessness is most likely the first effect you will notice upon entering the pool, you will work more against drag, which is the primary force opposing movement in the water. Water is 12 times more viscous than air. As a muscle exerts force to move a body part, it presents a surface area in direction of movement to the surrounding water. This is called frontal resistance. As the body part moves against the opposing drag, turbulence is created in the irregular movement of the water and the formation of eddies. As the body part moves through the water, inertia is created. This motion causes the water to move and travel in the direction of movement. When a change in direction is made, the body part will be moving against inertia, thus increasing the resistance encountered.
According to Newton's law, to every action there is an equal and opposite reaction; therefore, the more force you exert against the water, the more resistance you will encounter. In swimming, the goal is to streamline the body and create less turbulence. In water fitness, the properties of water are utilized to create more turbulence and increase the resistance. This creates the variable resistance of the water.
By utilizing these factors, it is apparent that a water resistance training program has many benefits for you. One benefit is that the speed of movement is not controlled, allowing an individualized approach to pace, strength gains, intensity and effort. The muscle used to exert force and the different joint angles affected by the given range of motion are subjected to a constant, balanced resistance from the water.
Muscle action against water resistance is primarily concentric. As the agonist moves against the resistance, the antagonist is being prepared to exert force in the opposite direction. The influences of gravity with regard to land exercises do not allow both muscles in a muscle pair to work concentrically when performing the same exercise. For example, a biceps curl performed on land would work the biceps concentrically, but its opposing muscle group, the triceps, would not have a concentric contraction as the arm returned to its starting position. In water, a biceps curl with a flat palm exerting force against the water would result in a concentric contraction of the biceps as the elbow flexed and a concentric contraction of the triceps as the elbow extended. This ability of the water to work the muscles in both directions of movement with equal force allows for greater muscle balance and equality in strength gains of synchronized pairs of muscles.
In order to increase strength and promote positive body changes, you must have desire, motivation and consistency in training. You must also utilize the overload principle. The overload principle requires the training program to upset homeostasis of the system being trained through mode of exercise, frequency, duration and intensity. The mode in this case is water resistance training, with frequency and duration. The frequency should be at least two days a week, with beginning exercisers starting with 8 to 10 reps per set. The most effective way to train a muscle is through full range of motion, manipulating the intensity.
Variables can be modified to manipulate the intensity. These variables are the surface area of the moving body part, the length of the moving limb and the speed of movement.
These three components affect the drag force and turbulent flow of the water.
Surface Area — Increasing the surface area of an object increases the frontal resistance presented to the horizontal forces of the water. Moving the whole body forward and backward in the water creates more frontal resistance than moving the body sideways through the water. As frontal resistance increases, the opposing force of drag is then increased. Drag can be increased by changing the hand position from a slice with the edge of the hand cutting through the water, to a cupped hand, then finally to a clawed hand with the fingers open creating further eddies and turbulence between the fingers.
Lever — A second variable is the length of the moving limb or the lever. The lever is affected by the forces of resistance and effort, with resistance consisting of the fluid drag and the effort from the muscle. By changing the length of the resistance arm, or lever, from short to long, the frontal resistance is again increased with the corresponding increase in drag. There is also an increase of the actual water to be "lifted" or moved to accommodate the change in position of the limb. This engages the muscle effort to generate force against the water resistance. An example of a change in lever length varying the resistance is a jog versus a straight leg kick. A jog involves the short lever of a flexed knee moving in the water versus the long lever of a straight leg kick (soft joint) displacing water. An extended foot versus a flexed foot can also change the lever length, with the extended foot generating a longer resistance arm. The long lever requires more effort from the mus¬cle to generate force for the movement.
Speed — A third variable for manipulating intensity is speed. As speed increases in the water, the resistance increases. It is tempting to move "faster," but the caution here is the tendency to compromise range of motion. The fast and slow twitch muscle fibers respond to training intensity of resistance, not necessarily to the speed of the contraction. An excellent way to judge speed in water resistance is with a tempo or cadence. Using a time range, the speed can be adjusted by the volume done in that amount of time. An example would be to do a set of 8 repetitions of a bicep curl in 10 seconds. To increase speed of movement, the repetitions could be increased to 12 in the same 10-second interval. As the speed increases, the resistance increases. Keep in mind the squared term of relative velocity; As speed doubles, the force increases by four. And as speed triples, the force increases by nine, etc. A separate application of speed would be acceleration. Resistance exercises can be done with force against the pool bottom or against water in a given direction. These types of exercises are generally known as plyometric.
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