Putting muscle in your workout: using resistance training to increase muscular strength and endurance

In 1990, the America College of Sports Medicine (ACSM) added resistance training recommendations to its existing position stand, recognizing muscular fitness as an integral part of overall fitness and wellness. ACSM's recommended minimum training stimulus for the healthy adult population is one set of eight-12 repetitions working eight-10 of the major muscle groups two days per week. Variations in program design accommodate diverse populations.

Designing a fitness program is as much an art as it is a science. All variables must be carefully analyzed before and throughout training to ensure development of a successful program. Through health and fitness assessments, a client's goals and needs may be determined. Administrative concerns, such as equipment and space availability, as well as time restraints must be addressed.

Muscular Strength and Endurance

Muscular endurance refers to the ability to sustain repetitions of submaximal force, and is measured by the number of repetitions that can be performed. Muscular strength refers to the ability to generate maximal force (1 RM) in good form and is measured by the amount of weight that can be lifted.

The Strength/Endurance Continuum

ENDURANCE STRENGTH 30-60% 1 RM 80-100% 1 RM 12 + repetitions 2-6 repetitions

To accomplish precise fitness goals, specific training must be applied. Specificity of training is also referred to as the Specific Adaptation to Imposed Demands (SAID) principle. Most often, a training goal somewhere between pure strength and endurance on the continuum is desired. Once training objectives are established, a trainer can design a program defining the muscles, actions and type of resistance to be included. Recommendations for frequency, intensity, volume and periodization may also be outlined.

To develop pure strength, maximal or near maximal force must be exerted. Only a few repetitions of this force can be performed at one time, and several minutes of recovery are required to replenish energy stores.

Many repetitions of submaximal force are required to develop muscular endurance. Minimal recovery periods are required between sets when training for endurance as the energy stores are not depleted during lower intensity.

Frequency

Two days per week is the recommended minimum to develop the musculature. Three days per week provides additional gains in strength. Research indicates less than two days per week will not provide sufficient training stimulus. Optimal training frequency varies depending on the muscles exercised, duration and intensity, fitness level, individual health status and training objectives.

Muscle fiber composition dictates the length of recovery required. Individuals with a high percentage of fast twitch fibers will require a longer recovery period, while those with a high percentage of slow twitch fibers are fatigue resistant and require less recovery time between workouts, according to Essentials of Strength Training and Conditioning (Human Kinetics, 1994) by Thomas R. Baechle.

Intensity

Intensity is defined as the workload or weight per repetition. In order to achieve gains in muscular strength or endurance, the principle of overload, or stressing the body slightly beyond its capacity to increase work potential, must be utilized. Specifically, adaptation to stress occurs and a training effect results. When stress is greatly beyond the body's capacity, injury will likely result. As the body adapts to stress and training, the stress overload must be continually increased for growth. This principle is called progressive overload.

Volume of Training

Volume of training describes the total amount of weight lifted in a workout and is defined as sets multiplied by repetitions multiplied by intensity. Volume may be used to measure a specific exercise or a total workout. It varies according to goals and training status.

Order of Exercise

Order of exercises selected depends on factors such as conditioning level and training goals and methods. Generally speaking, the large muscle, multi-joint exercises should be performed first followed by single muscle isolation exercises. This prevents early fatigue of isolated muscles needed to perform the multi-joint work. Individuals with motor performance goals, such as competitive body building and performance lifting, may use alternate methods of training. A well-rounded program will include exercises for all major muscles. To avoid fatigue, arrange exercises so the same muscles don't work successively.

Periodization

Periodization is the gradual development or cycling of a training program and is used to avoid plateaus in training. A carefully designed periodization schedule is important when preparing athletes for a competitive season. A cycle includes conditioning phases to optimize performance and develop hypertrophy, strength and power. A gradual transition phase, including lower work volume and greater emphasis on mental preparation, precedes the competition phase. A lower training volume can be resumed at the end of a competitive season.