KinX Learning Blog

A muscle is called a prime mover, agonist, or muscle most involved when it is the main muscle involved in a concentric contraction. For example, in the biceps curl the biceps brachialis and brachioradialis are agonists for elbow flexion. Many muscles are prime movers in more than one action, as for example, the biceps is also a prime mover in forearm supination.

One of the most frequently asked questions is how many repetitions should be done for each exercise. This is a valid question since the number of repetitions (together with the number of sets) is the key to the type of development that will be produced. However, it is important to understand that there are no magical numbers that will produce the changes you desire. Strength, flexibility, muscle mass, and muscular endurance development are very individualistic. For some individuals doing a certain number of repetitions will produce the greatest increase in strength, flexibility, endurance, etc. while for others there will be minor changes. Because of this, you must pay close attention to the changes you receive from doing exercises with different numbers of repetitions in regard to your capabilities. There are, however, some excellent guidelines to direct your training based on research and practical experiences. Following are some guidelines for the number of repetitions that should be used when the athlete is well experienced in weight training and has been in training in his sport for several years. 1-4 repetitions are for pure strength. There are no increases in muscle mass.5-9 repetitions for strength together with muscle mass.10-15 repetitions for muscular strength, muscular endurance, and muscle mass.16-30 repetitions are for muscular endurance. There may also be small increases in muscular strength and/or mass.31-50 repetitions are used for the development of muscular endurance, no mass and some cardiovascular endurance.50-100 repetitions for muscular endurance, cardiorespiratory endurance, a possible loss of fat andmass and no strength increases. Keep in mind that these are only guidelines and there is variation in the numbers depending upon the individual and his or her stage of training. For example, high-level athletes who require increases in strength usually train in the 5-9 RM range, but not year round. Training with the same number of repetitions and weight leads to the hitting of a plateau (or full adaptation) in regard to increases in strength or other physical qualities.

It is generally assumed that when you lift weights you should do three sets of each exercise inorder to gain strength. This is a fallacy. If you are a beginner, doing one set will give you the same gains as doing two or more sets. The reason for this is that one set is more than adequate to sufficiently deplete your energy supplies to bring about supercompensation. The higher your level of fitness and the more strength you want to gain, the greater is the number of sets. This also depends on the percent of maximum weight being used. In general, the more sets you do, the fewer the repetitions for each exercise. The more repetitions you do, the fewer the number of sets that are needed. In supercompensation your energy supply is not only restored to the original level, but additional energy supplies are deposited to allow for more work in the upcoming workouts. During supercompensation, there is restructuring of the muscles and tissues to increase their strength, endurance and/or mass. In addition, there is usually greater capillarization to better support the muscles and tissues and other organs. These changes enable you to do the same or greater amounts of work with greater ease in the following workouts. The changes that are produced during the phase of supercompensation are the key to any development that you undergo. As fitness and strength levels increase, it may require two sets or more to adequately deplete the energy stores in order to continue achieving supercompensation. When two sets are insufficient, it is necessary to do three sets. This applies only when the number of repetitions is no greater than 8-12 RM. However, the use of two or more sets is usually reserved for the third or fourth year of training. Doing more than one set soon after initiating the strength training program, creates excessive stress on the body. Studies have shown that lower intensity programs produce greater supercompensation which results in greater development of the body. This is why it is often best to stay with one set for longer periods of time. The one set will produce greater and better results. Doing more than 3 to 4 or more sets does not allow the body to produce the gains that are possible when less stress (less intensity) is employed. This is a fact that is typically been overlooked in the development and practice of effective strength training programs. A more advanced athlete may use a low range of 3-5 RM. In such cases, five or six sets can be done. If a 1-3 RM routine is used, then it is possible to do up to 6-8 sets. However, when the number of sets gets this high, fatigue usually sets in and there is a breakdown in technique. Because of this, some athletes can be found using 10-15 sets, but this is seen only when practicing a particular lift for competition. In this case, each set consists of 1-2 repetitions and they are executed over the course of a day, not in one workout. Such high-intensity workouts are recommended only for the highest level athletes. It must also be pointed out that all novice athletes should do a greater number of exercises rather than more sets and a limited number of exercises. There are multiple and sometimes complex reasons for this. They are discussed in the next section. Suffice it to say, a greater number of exercises are needed in order to fully develop the body. This is especially needed for the high school athlete and for athletes who have not previously trained. The greater number of exercises is necessary to develop the base needed in order to do more intense or specialized strength exercises. Note also that it takes approximately 20 or more exercises to cover all the major joints and joint actions of the body. When the athlete (usually high school level) completes all the exercises for a total body workout, there should be a high level of fatigue. In such cases doing more than one set will lead to overtraining. Thus, you should use additional sets wisely. This should mean only when additional sets help to ensure continuous development of strength and other qualities. Always adjust the number of sets to the number of repetitions and number of exercises that are used in one workout. In general, there is no magical number of sets that will produce the greatest development. The exact number always depends on your level of fitness, mastery of the exercises, training objectives, and stages of training. For most athletes however, less intensity is most important for continuous development  of the body and sports abilities.  

The most accurate way to determine the key joint actions and muscles involved in a strength exercise is to analyze biomechanically and kinesiologically, the movements that are performed. By doing this you can also determine the effectiveness of the exercise in relation to muscle involvement and function. Only in this way can you determine which joint actions and muscles play a major role and if the exercise is effective and safe. In books and magazines exercises are usually described in very general terms. As a result it leads to misunderstandings. An exercise analysis, however, answers questions such as: If the exercise is effective, why is it effective? What is the role of each joint action? What is the role of the different muscles that are involved? With this information it is possible to determine which actions can be changed to make the technique more effective? Also, how can joint, body, or limb movements be changed to bring in greater involvement of specific muscles? How can specific actions be made more powerful? Should the exercise be modified? If the answer is yes, how can this be done? Most sources of standard instruction fail to address important points such as these. There is a lack of agreement in regard to exercises and their execution among iron sport athletes, strength and conditioning coaches, athletes, personal trainers, and people who are involved in fitness programs. There is often disagreement when identifying the key actions and the exact execution that is needed to ensure safety and produce maximum strength or muscle involvement. Nor is there conformity as to how each joint action involves specific muscles. Instead, we see articles espousing the opinions of exercisers, personal trainers, and celebrities which are often at odds with one another’s views. You have probably read articles dealing with certain issues, as for instance, whether the bar should be pulled down in front or behind the head when doing the lat pull-down. Or, if the arms should be raised shoulder level or completely overhead when doing the lateral or front arm raise, or if you should hold your breath on the exertion phase of a lift. From biomechanics and kinesiology, that also incorporate pertinent physiological factors, we can come up with definitive answers to resolve these issues. These answers are based on science and facts, not opinion, as is often being done. Biomechanics is the study of movement, more specifically, the movement (technique) involved in a strength exercise, or in execution of a sports skill. It deals mainly with physical factors such as speed, mass, acceleration, levers, force, and the physical functions of the movement. Some think of biomechanics as the science of movement based on principles derived from physics and anatomy. It explains the “why” and “how” of a movement and strategies to improve it through scientifically-based modifications. Kinesiology is the study of human motion which deals mainly with the muscles and their functions. It describes movement, which muscles are involved in the movement, and how exactly they are involved. It explores the muscular involvement in strength exercises and sports technique while biomechanics looks at the physical factors involved in the movement. By applying basic scientific laws it is possible to come up with accurate descriptions not only of what should take place in the exercise, but also the roles that key joint actions and muscles play. By studying the physical characteristics of the human body and the principles of mechanical physics, you will be able to better apply the information to your workouts or to those of your charges. You will have the basis for selecting and using specific exercises and movements to produce the results desired. Biomechanics and, to a limited extent, kinesiology are relatively new to the fitness and sports fields but are very important emerging sciences. They help to determine what exercises a person should do, how the workouts should be conducted, how effective the exercise execution is and if the exercises you use are safe. Biomechanics shows you the way to do exercises most effectively while kinesiology tells you which muscles are involved in the particular actions that take place in the exercise.