The core curriculum Resistance training is an important component of a comprehensive fitness program. A proper resistance-training program should be based on several factors, including health and fitness status, goals, proper application of the basic principles of training and the training environment. Health and fitness status. Prior to initiating resistance training, participants should take certain precautions. At a minimum, a health/medical questionnaire should be completed. Participants should also consider a muscular fitness evaluation prior to initiating resistance training. Because muscularly fit individuals do not improve as much or as quickly as untrained individuals, the initial level of muscular fitness can affect the magnitude and rate of improvement, and should be considered when establishing goals or evaluating the program's effectiveness. However, it's important to note that some individuals may be unable to tolerate muscular fitness testing, especially lifting heavy loads.

Goals. Once pre-exercise screening and assessment is complete, develop realistic goals and objectives for the resistance-training program.

Unrealistic expectations can lead to adverse outcomes, including discouragement, poor adherence and injury. To enhance the likelihood that resistance training is based on appropriate expectations, it helps to have an understanding of the physiological adaptations..

Basic training principles. Overload and specificity are fundamental precepts of resistance training. Both relate to the ability of targeted muscle groups to adapt to progressive stress. Adherence to these principles elicits both structural and functional adaptations. A resistance-training program that does not incorporate these fundamentals cannot provide consistent improvement in muscular fitness.

Overload is accomplished when a greater-than-normal physical demand is placed on muscles. The amount of overload required depends on the exerciser's current level of muscular fitness. For example, a football player requires a different level of overload than a sedentary person. To produce strength and endurance gains, the muscular system must be progressively overloaded. By definition, overloading is dynamic (changing). As a muscle or muscle group adapts, a progressive overload is required to continue improvement. For resistance training, overload can be achieved by one or more of the following variations:

*Increasing the resistance or weight

*Increasing the repetitions

*Increasing the sets

*Decreasing the rest period between sets or exercises

A training intensity of approximately 40 to 60 percent of one repetition maximum (RM) appears to be sufficient for the development of muscular strength in most normally active individuals. Intensities of 80 to 100 percent, however, have been shown to produce the most rapid gain in muscular strength. Due to the possibility of overtraining or injury, though,such intensities are generally contraindicated, especially in previously sedentary middle-aged and older adults.

Specificity relates to the nature of changes (structural and functional, systemic and local) that occur in an individual as a result of training. These adaptations are specific, and occur only in the overloaded muscles. Sports require specific movement patterns, which a properly designed program should consider. Although a comprehensive resistance-training program should include exercises for all the major muscle groups, it can be modified to address the unique demands of a particular sport or activity. The resistance-training program for a baseball pitcher, for example, should emphasize the rotator cuff, shoulder girdle and upper extremities, whereas a resistance training for a soccer player should focus on the lower extremities and include exercises to develop strength and endurance for the gluteals, quadriceps, hamstrings, abductors, adductors and gastrocnemius.

One of the most controversial issues regarding specificity is the debate over how to develop muscular strength versus muscular endurance. Based on the available literature, different programs should be employed. Muscular strength is the ability to generate force at a given speed (velocity) of movement, while muscular endurance is the ability to persist in physical activity or resist muscular fatigue. Generally, strength is developed with more resistance and fewer repetitions, while muscular endurance requires low to moderate resistance and more repetitions. Adaptations occur at both the cellular level (metabolic adaptation) and at the fiber level (selective hypertrophy and motor unit recruitment patterns). Both strength and endurance are developed, to some extent, regardless of the resistance-training prescription, because both fitness components exist on a continuum. However, one component may be emphasized, depending upon the specific program.

Strength gains are also dependent on the mode of resistance training (static, dynamic, isokinetic), the type of contraction (concentric, eccentric), the speed of contraction and the joint position. The extent to which and how these factors should be incorporated into a resistance-training program remains an ongoing topic of discussion.

General guidelines

Specific guidelines for achieving muscular fitness are not as universally accepted as those for aerobic fitness. There is considerable controversy regarding the most appropriate prescription for developing muscular fitness, especially in novice exercisers and competitive athletes. However, acceptance is growing that moderate-intensity resistance training should be an integral part of a comprehensive fitness program.

As with any exercise prescription, instructions regarding intensity, duration and frequency, as well as guidelines for rate of progression and precautions, are important. This information should be based on the health and fitness status, and personal goals and interests of the exerciser.

Muscular fitness can be developed through either static (isometric) or dynamic (isotonic and isokinetic) exercises. Dynamic resistance is recommended for most adults who wish to engage in basic resistance training. Because the primary objective of resistance training should be to develop total-body muscular fitness in a safe and time-efficient manner, individuals should be encouraged to perform eight to 10 different exercises to condition major muscle groups.

Appropriate resistance training for healthy adults should be based on the following guidelines and principles:

*Warm-up prior to performing resistance exercises.

*Adhere to proper techniques.

*Perform at least one set of eight to 12 repetitions of each exercise to the point of volitional fatigue. A recent review showed that one set of resistance-training exercises provides nearly the same improvement in muscular strength and endurance as multiple sets of resistance-training exercises. Consequently, for the average person beginning a resistance-training program, single-set programs are recommended over multiple-set programs, because they are effective and less time-consuming.

*Increase the resistance when a predetermined number of repetitions (typically eight to 12) can be completed using proper form. Increases in resistance should be made gradually (e.g., increments of approximately 2 to 5 percent).

*Exercise at least two days per week. Recovery time (rest) is an important component of muscular growth and strength development, and most individuals require approximately 48 hours to recover from a typical resistance-training session. When training at very low loads (i.e., in certain therapeutic settings), more frequent training sessions may be tolerated.

*Perform both the lifting (concentric phase) and lowering (eccentric phase) portions in a controlled manner. Using ballistic-type movements during resistance training can compromise safety and effectiveness.

*Perform each exercise through a functional range of motion. This helps ensure that joint mobility is maintained and, in some instances, enhanced.

*Maintain a normal breathing pattern, since breath-holding may induce elevations in blood pressure.

*When possible, exercise with a training partner who provides feedback, assistance and encouragement.

A key ingredient to total fitness

An understanding of resistance-training equipment and the most commonly used methods for developing strength (as well as advantages and limitations) is basic for the effective prescription and modification of resistance-training programs. Modification is necessary to maximize the benefits from resistance training and to avoid injury.

The benefits of strength training are no longer in question. Research continues to demonstrate that strength training plays an important role in helping individuals look and function better. A safe strength-training program combined with aerobic conditioning will yield the significant health benefits of a total fitness program.

REFERENCES

American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription. Philadelphia, Pa.: Lippincott Williams & Wilkins, 2000 (6th ed.).

Brzycki, M. (ed.).Maximize Your Training: Insights from Leading Strength and Fitness Professionals. Lincolnwood, Ill.: Masters Press, 2000.

Carpinelli, R.N., and R.M. Otto. Strength Training: Single versus multiple sets. Sports Medicine 26(2):73-84, Aug. 1998.

Feigenbaum, M.S., and M.L.Pollock.Strength Training: Rationale for current guidelines for adult fitness programs. Physician and Sportsmedicine 25(2):44-64, 1997.

Fleck, S.J., and W.J.Kraemer. Designing Resistance Training Programs. Champaign, Ill.: Human Kinetics, 1997 (2nd ed.).

Franklin, B.A. Pumping Iron: Rationale, benefits, safety and prescription. ACSM's Health & Fitness Journal 2(5):12-15, 1998.

Peterson, J.A., and C.X.Bryant.The StairMaster Fitness Handbook. Champaign, Ill.: Sagamore Publishing Company, 1995 (2nd ed.).

Pollock, M.L., and K.R. Vincent. The President's Council on Physical Fitness and Sports Research Digest. Series 2:No. 8, 1996.

 

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The three components of energy balance that need to be considered when discussing weight control and metabolic rate are caloric intake, caloric stores and caloric expenditure.