Research Study: Variable Resistance vs. Standard Resistance Training

Research study: Variable Resistance vs. Standard Resistance Training — Muscular strength can be defined as maximal force that a muscle group can exert against resistance. In 1948, Delorme adopted the term " progressive resistance exercise" for his method of developing muscular strength. McQueen distinguished between exercise regimens for producing muscle hypertrophy and for those for producing muscle power. He concluded that the number of repetitions determines the characteristics of the exercise. Hundreds of investigations based on these early studies have been published. They include isotonic exercises, isometric exercises, eccentric contraction techniques, Oxford technique, double and triple progressive super set system and many others.  Each system has its supporters and refuters. Berger states that 6-7 repetitions three time a week is best for developing dynamic strength. Steinhouse emphasizes the need to increase the intensity - not the amount - of the work in order to develop maximum strength. The most recent studies on exercise, conducted by Thomas B. Pipes and Jack H. Wilmore, contrasts isokinetic and isotonic strength training. The study indicates a clear superiority for isokinetics.

In 1972, Ariel introduced the Dynamic Variable Resistance exercise principles, which, for the first time, enabled biomechanical principles to be employed in the design of exercise equipment. Rather than force the man to fit the machine, the machine was designed to fit the man.

Most athletic movements are ballistic in nature. They are programmed in the central mechanisms of the brain, and once initiated, cannot be influenced by sensory and/or environmental information. This necessitates preciseness in the timing and coordination of both the system of muscle contraction and the segmental sequence of muscular activity involved with complex tasks.

A characteristic pattern of motion exists during the intentional movement of the body segments against resistance. It consists of reciprocally organized activity between the agonist and antagonist muscles. The reciprocal activities occur in consistent temporal relationships with motion parameters, such as velocity, acceleration and forces.

Hellebrandt and Houtz shed some light on the mechanism of muscle training via the overload principle. They found that the mere repetition of non-stressful contractions has little effect on the functional capacity of the skeletal muscles; that the critical variable upon which muscular development depends is the amount of work per unit of time. The speed with which the functional capacity increases suggests that the central nervous system, as well as the contractile tissue is an important contributing component of training.

Since the human body is a system of linked segments, various forces cause these segments to rotate about their anatomical axes. Both muscle and gravitational forces are important in producing these turning effects, which are fundamental in body movements in all sports and daily living. Pushing, pulling, lifting kicking running walking, and all human activities stem from rotational motion of the links (which are made of bones).

Since force has been considered the most important component of athletic performance, many exercise devices have been developed that employ isometrics and isokinetics. These devices inhibit the natural movement patterns of acceleration and deceleration. Force, however, is only one of the three factors influencing all performance. The other two factors are displacement (direction of movement) and duration of movement. The muscular forces interact to move the body parts through the activity. The displacement of the body parts and their speed of motion are important in the coordination of the activity and are also directly related to the force produced.  However, it is only because the control provided by the brain that the muscular forces follow any particular displacement pattern. Without these brain center controls, there would be no skilled athletic performance. The intricate timing of the varying forces is a critical factor in successful performances. Training an isolated muscle group slowly or at a constant speed may, therefore, result in poorer performances. 

The Dynamic Variable Resistance (D.V.R.) Concept – 

In conventional resistive exercises, loads are moved through a range of motion. The muscular force and the load are not constant because of the modifying effects of the lever system throughout the range of motion. In an exercise such as the bench press, for example, the resistance achieves maximum effect at a specific point, and becomes less anywhere above or below that point. This illustrates a phenomenon; that the muscle works at maximum potential during a very small range of motion throughout an exercise stroke. To facilitate maximum muscular involvement, you must vary the resistance. In some exercises, this resistance must be varied as much as 100% in order to maintain the maximum moment of force. The resistance must be varied according to biomechanical data obtained under dynamic conditions. 

Method – 

20 University athletes between the ages of 19 and 23 were recruited for a 20-week experiment. The athletes, each of whom had at least 2 years of weight training experience, averaged 181.5 cm. in height and 91.4 kg. in weight. They were divided into two equal groups: Group 1,  which was assigned to conventional Olympic barbell equipment, and group 2 which was assigned to D.V.R. exercise equipment. For four weeks prior to the experimental period, the subjects lifted weights for two hours, five days a week. The program based on the overload principle, consisted of the bench press, military press, squat, and arm curl exercises. 

Each exercise was performed in sets of four with an increased load following a pyramidal increase. Each set consisted of a decreasing number of repetitions from 8 to 3. Weights were increased as rapidly as possible to maintain the training at maximum effort.

The training program for both groups were identical, the only difference being the exercise equipment. Constant supervision of workouts was maintained at all times. Testing was conducted every six days until the conclusion of the study. 

Both experimental groups were tested for maximum dynamic strength on the Olympic bench press set. The exercise was selected due to the similarity of the procedures. The subject reclined on his back flat against the bench. The weight was handed to the subject, who then lowered it to his chest and then immediately raised it to a straight arm position directly above his chest.

Note: Maximum strength testing was conducted on the Olympic bench press set even though only Group 1 trained with the Olympic barbells. Group 2 trained only with the dynamic variable resistance apparatus. This factor introduced a bias against Group 2 subjects, since they were not repeatedly exposed to the Olympic bars in training.

Results –

Both groups increased their mean strength level during the 20-week period. 

– The Olympic barbell group increased their strength levels from 259.5 lbs. to 285.5 lbs - a mean change of 36 lbs. Such strength gain, though perhaps having practical significance, was not considered statistically significant.

– The D.V.R exercise group increased their mean strength from 252.5 lbs. to 327.0 lbs. - a mean change of 74.5 lbs., which was considered both statistically and practically significant.

Discussion – 

The experiment indicated that training the muscle in a dynamic fashion alone such as with Olympic bar lifting does not produce maximum efficiency. To achieve greater muscular gains, you must vary the resistance via the biomechanical principles. 

A resistance device such as the Olympic barbell applies two kinds of forces: (1) the internal forces produced by the muscular system and (2) the external forces produced by the resistance device, in this case the weight or the bar. When considering the human force system, you must include muscles, bones and joints, as well as externally applied resistance. The actual forces produced by individual muscles cannot be predicted easily because of the indeterminable influence of a number of physiological and mechanical factors. These include length-tension and force-velocity relationships, as well as the location of the muscular attachments with respect to the joint and the dynamic effect of movement.

In conventional resistance exercise such as on the bench press, loads are moved through a range of motion. The mass remains constant throughout the motion, but the muscular forces and the dynamic forces are not constant because of the modifying effects of the lever system throughout the range of motion. For all practical purposes, the absolute muscular force is the same throughout the exercise, since the only difference is the force arm on which the muscle pulls. When the force arm changes due to the angular changes of the limb, the muscle can lift a variable load.

Another factor to consider in muscular training is the dynamic characteristics of the motion. In conventional barbell lifting, an initial burst of muscular activity occurs as the agonist muscle contracts and the antagonist muscle relaxes, thus causing acceleration of the limb. This is followed by an intervening quiet period during which there is no muscular firing activity, and by a deceleration of the limb as the antagonist contracts. Near the end of the movement, the antagonist muscle has to stop the motion. With a conventional barbell, the stopping motion starts too soon, causing a diminished training effect.

The D.V.R. equipment assigns different resistances throughout the range of motion in order to accommodate the biomechanical changes occurring during the exercise and at the same time, adjusts for the ballistic characteristics of the movement. With the D.V.R. apparatus, the agonist muscle can fire for a longer period of time.

Study Conclusion –

This study shows that this type of ballistic training is more efficient for dynamic muscular training.