Part lll

Exercise training

The study of exercise physiology can be divided into how the body responds during acute bouts of exercise and how it adapts to repeated exercise sessions (i.e., training responses). In the two previous sections of the book, we examined the control and function of skeletal muscle during acute exercise (part I) and the role of the cardiovascular and respiratory systems in supporting those functions (part II). In part III we examine how these systems adapt when exposed to repeated bouts of exercise (i.e., adaptations to training). Chapter 9,“Principles of Exercise Training," lays the groundwork for subsequent chapters by discussing the terminology and training principles used by exercise physiologists. The principles presented in this chapter can be used to optimize the physiological adaptations to a training program. In chapter 10, “Adaptations to Resistance Training," we consider the mechanisms through which muscular strength and muscular endurance improve in response to resistance training. Finally, in chapter 11, “Adaptations to Aerobic and Anaerobic Training," we discuss the changes in various systems of the body that result from performing regular physical activity involving various combinations of exercise intensity and duration. Training adaptations that ultimately lead to improvements in exercise capacity and athletic performance are specific to the training to which those physiological systems are exposed.

Chapter 9

Principles of Exercise Training 

Previous chapters examining the acute response to exercise covered the body's immediate response to a single exercise bout. We now investigate how the body responds to repeated bouts of exercise performed over a period of time -exercise training. When one performs regular exercise over a period of days, weeks, and months, a variety of physiological adaptations occur. The positive adaptations that accompany proper training principles lead to improvement in both exercise capacity and sport performance. With resistance training, muscles become stronger. With aerobic training, the heart and lungs become more efficient at oxygen delivery, and exercise endurance increases. With high-intensity anaerobic training, the neuromuscular, metabolic, and cardiovascular systems adapt to generate more adenosine triphosphate (ATP) per unit of time, thus increasing muscular endurance and speed of movement over short periods of time. These adaptations are highly specific to the type of training performed. Before examining specific adaptations to training, this chapter first looks at the basic terminology and general principles used in exercise training and then gives an overview of the elements of proper training programs.

Muscular Strength

Strength is defined as the maximal force that a muscle or muscle group can generate. Someone with a maximal capacity to bench press 100 kg (220 lb) has twice the strength of someone who can bench press 50 kg (110 lb). In this example, strength is defined as the maximal weight the individual can lift with one single effort. This is referred to as 1-repetition maximum, or 1RM. To determine 1RM in the weight room or fitness center, people select a weight that they know they can lift at least one time. After a proper warm-up, they try to execute several repetitions. If they can perform more than one repetition, they add weight and try again to execute several repetitions. This continues until the person is unable to lift the weight more than a single repetition. This last weight that can be lifted only once is the 1RM for that particular exercise. The 1RM is commonly used in the laboratory or weight room as a measure of strength.

Muscular Power

Power is defined as the rate at which work is performed, thus the product of force and velocity. Unlike strength, it has a speed component. Maximal muscular power, generally referred to simply as power, is the explosive aspect of strength, the product of strength and the velocity of movement.

Power = Force x Distance/Time

where Force = Strength

and Distance 1 Time = Velocity

Muscular Endurance

Many sporting activities depend on the muscles' ability to repeatedly develop or sustain submaximal forces or to do both. The capacity to perform repeated muscle contractions, or to sustain a contraction over time, is termed muscular endurance. Examples of muscular endurance include performing sit-ups or push-ups or sustaining force in an attempt to pin an opponent in wrestling. Although several valid laboratory techniques are available to directly measure muscular endurance, a simple way to estimate it is to assess the maximum number of repetitions one can perform at a given percentage of 1RM. For example, a man who has a 1RM for the bench press of 100 kg (220 lb) could evaluate his muscular endurance independent of his muscular strength by measuring how many repetitions he could perform at, for example, 75% of that 1RM (75 kg, or 165 1b). Muscular endurance is increased through gains in muscular strength and through changes in local blood flow and metabolic function. Metabolic and circulatory adaptations that occur with training are discussed in chapter 11.

Aerobic Power

Aerobic power is defined as the rate of energy release by cellular metabolic processes that depend on the continued availability of oxygen. It is synonymous with the terms aerobic capacity and maximal oxygen uptake (ѶO2max). Maximal aerobic power is the highest oxygen uptake that an individual can obtain during dynamic exercise using large muscle groups for a few minutes. It depends on the maximal capacity for aerobic resynthesis of ATP. In most healthy individuals, maximal aerobic power is limited primarily by the central cardiovascular system and to a lesser extent by respiration and metabolism. The best laboratory test of aerobic power is a graded exercise test to exhaustion during which ѶO2 is measured and ѶO2max is determined, as discussed in detail in chapter 5. A number of field tests, most often measuring the time needed to walk or run a set distance or the distance covered in a given time, have been developed to estimate ѶO2max without the need to actually measure it in the laboratory.

Anaerobic Power

Anaerobic power is defined as the rate of energy release by cellular metabolic processes that function without the involvement of oxygen. Maximal anaerobic power, or anaerobic capacity, is defined as the maximal capacity of the anaerobic systems (ATP-phosphocreatine[PCr] system and anaerobic glycolytic system) to produce ATP. Unlike the situation with aerobic power, there is no universally accepted laboratory test to determine anaerobic power. Several tests provide estimates of maximal anaerobic power, including the maximal accumulated oxygen deficit test, the critical power test, and the Wingate anaerobic test.

In Review

 Muscular strength refers to the ability of a muscle or muscle group to exert force.

 Muscular power is the rate of performing work, or the product of force and velocity.

 Muscular endurance is the capacity to sustain a static contraction or to perform repeated muscle contractions.

 Maximal aerobic power, or aerobic capacity, is the highest oxygen uptake that an individual can obtain during sustained dynamic exercise using large muscle groups.

 Maximal anaerobic power, or anaerobic capacity, is defined as the maximal capacity of the anaerobic energy systems to produce ATP.

General Principles of Training

Chapters 10 and 11 present in detail the specific physiological adaptations that result from resistance training, aerobic training, and anaerobic training. Several principles, however, apply to all forms of exercise training.

Principle of Individuality

Individuals do not all possess the same inherent ability to respond to an acute exercise bout, or the same capacity to adapt to exercise training. Heredity plays a major role in determining the body's response to a single bout of exercise, as well as the chronic changes that result from a training program. This is the principle of individuality. Except for identical twins, no two people have exactly the same genetic characteristics, so individuals are unlikely to exhibit the same responses. Variations in cellular growth rates, metabolism, cardiovascular and respiratory regulation, and neural and endocrine regulation lead to tremendous individual variation. Such individual variation likely explains why some people show great improvement after participating in a given program ("high responders") whereas others experience little or no change after following the same program (“low responders"). We discuss this phenomenon of high and low responders in more detail in chapter 11. For these reasons, any training program must take into account the specific needs and abilities of the individuals for whom it is designed. Do not expect all individuals to have exactly the same degree of improvement, even when they train exactly the same.

Principle of Specificity

Training adaptations are highly specific to the type of activity being performed and to the volume and intensity of the exercise. To improve muscular power, for example, a shot-putter would not emphasize distance running or slow, low-intensity resistance training. The shot-putter needs to develop explosive power. Similarly, the marathon runner would not focus on sprint training. This is likely the reason that athletes who train for strength andpower, such as weightlifters, often have great strength but don't have highly developed aerobic endurance when compared to untrained people. According to the principle of specificity, exercise adaptations are specific to the mode, intensity, and duration of training; and the training program must stress the physiological systems that are critical for optimal performance in a given sport in order to achieve specific training adaptations and goals.

Principle of Reversibility

Resistance training improves muscle strength and the capacity to resist fatigue. Likewise, endurance training improves the ability to perform aerobic exercise at higher intensities and for longer periods. But if training is decreased or stopped (detraining), the physiological adaptations that caused those improvements in performance will be reversed. Any gains achieved with training will eventually be lost. The principle of reversibility lends scientific support to the saying “Use it or lose it." All effective training programs must include a maintenance plan that sustains the physiological adaptations gained by training. In chapter 14 we examine specific physiological changes that occur when the training stimulus stops. I

Principle of Progressive Overload

Two important concepts, overload and progressive training, form the foundation of all training programs. According to the principle of progressive overload, systematically increasing the demands on the body is necessary for continued improvement. For example, when undergoing a strength training program, in order to gain strength the muscles must be overloaded, which means they must be loaded beyond the point to which they are normally loaded. Progressive resistance training implies that as the muscles become stronger, either increased resistance or increased repetitions or both are required to stimulate further strength increases.

As an example, consider a young woman who can perform only 10 repetitions of a bench press before reaching fatigue, using 30 kg (66 lb) of weight. With a week or two of resistance training, she should be able to increase to 14 or 15 repetitions with the same weight. She then adds 2.3 kg (5 lb) to the bar, and her repetitions decrease to 8 or 10. As she continues to train, the repetitions continue to increase; and within another week or two, she is ready to add another 5 lb of weight. Thus, improvement depends on aprogressive increase in the amount of weight lifted. In a similar way, training volume (intensity and duration) must be increased progressively with anaerobic and aerobic training for further improvements to occur.

Principle of Variation

The principle of variation, also called the principle of periodization, first proposed in the 1960s, has become very popular in the area of resistance training. Periodization is the systematic process of changing one or more variables in the training program-mode, volume, or intensity- -over time to allow for the training stimulus to remain challenging and effective.' Training intensity and volume of training are the most commonly manipulated aspects of training to achieve peak levels of fitness for competition. Classical periodization involves high initial training volume with low intensity; then, as training progresses, volume decreases and intensity gradually increases. Undulating periodization uses more frequent variation within a training cycle.

For sport-specific training, the volume and intensity of training are varied over a macrocycle, which is generally up to a year of training. A macrocycle is composed of two or more mesocycles that are dictated by the dates of major competitions. Each mesocycle is subdivided into periods of preparation, competition, and transition. This principle is discussed in greater detail in chapter 14.

In Review

 According to the principle of individuality, each person responds uniquely to training, and training programs must be designed to allow for individual variation.

 According to the principle of specificity, to maximize benefits, training must be specifically matched to the type of activity or sport the person engages in. An athlete involved in a sport that requires tremendous strength, such as weightlifting, would not expect great strength gains from endurance running.

 According to the principle of reversibility, training benefits are lost if training is either discontinued or reduced abruptly. To avoid this, all training programs must include a maintenance program.

 According to the principle of progressive overload, as the body adapts to training at a given volume and intensity, the stress placed on the body must be increased  progressively for the training stimulus to remain effective in producing further improvements.

 According to the principle of variation (or periodization), one or more aspects of the training program should be altered over time to maximize effectiveness of training. The systematic variation of volume and intensity is most effective for long- term progression.

Resistance Training Programs

Over the past 75 years, research has provided a substantial knowledge base concerning resistance training and its application to health and sport. The health aspects of resistance training are discussed in chapter 20. This section concerns primarily the use of resistance training for sport.

Anaerobic and Aerobic Power Training Programs

Different types of training programs can be used to meet the specific training requirements of each event, such as in running and swimming, and each sport. this section describes some of the more popular types of training programs and how they are used to improve the specific energy systems.

Interval Training

Interval training consists of repeated bouts of high- to moderate-intensity exercise interspersed with periods of rest or reduced-intensity exercise. Research has shown that athletes can perform a considerably greater total volume of exercise by breaking the overall exercise period into shorter, more intense bouts, with rest or active recovery intervals inserted between the intense bouts.

The vocabulary used to describe an interval training program is similar to that used in resistance training and includes the terms sets, repetitions, training time, training distance and frequency, exercise interval, and rest or active recovery interval. Interval training is frequently prescribed in these terms as illustrated in the following example for a middle-distance runner:

 Set1:6x400mat75s(90 s slowjog)

 Set2:6x800mat180s(200 s jog-walk)

For the first set, the athlete would run six repetitions of 400 m each, completing the exercise interval in 75 s and recovering for 90 s between exercise intervals with slow jogging. The second set consists of running six repetitions of 800 m each, completing the exercise interval in 180 s, and recovering for 200 s with walking-jogging.

While interval training is traditionally associated with track, cross- country, and swimming, it is appropriate for all sports and activities. One can adapt interval training procedures for each sport or event by first selecting the form or mode of training and then manipulating the following primary variables to fit the sport and athlete:

 Rate of the exercise interval

 Distance of the exercise interval

 Number of repetitions and sets during each training session. 

 Duration of the rest or active recovery interval

 Type of activity during the active recovery interval

 Frequency of training per week

Exercise Interval Intensity

One can determine the intensity of the exercise interval either by establishing a specific duration for a set distance, as illustrated in our previous example for set 1 (i.e., 75s for 400m), or by using a fixed percentage of the athlete's maximal heart rate (HRmax). Setting a specific duration is more practical, particularly for short sprints. One typically determines this by using the athlete's best time for the set distance and then adjusting the duration according to the relative intensity that the athlete wants to achieve, wich 100% equal to theathlete's best time. As an example, to develop the ATP-PCr system, the intensity should be near maximal (e.g., 90-98%); to develop the anaerobic glycolytic system, it should be high (e.g., 80-95%); and to develop the aerobic system, it should be moderate to high (e.g., 75-85%). These estimated percentages are only approximations and are dependent on the athlete's genetic potential and fitness level, duration of the interval (e.g., 10 s vs. 10 min), number of repetitions and sets, and duration of the active recovery interval.

In Review

 Low-repetition, high-resistance training enhances strength development, whereas high-repetition, low-intensity training optimizes the development of muscular endurance.

 Variation (or periodization), through which various aspects of the training program are altered, is important to optimize results and to prevent overtraining or burnout.

 Resistance programs aimed at improving strength should involve repetitions with both concentric (muscle shortening) and eccentric (muscle lengthening) actions. Isometric contractions play a beneficial, but secondary, role and may be included as well.

 Large muscle groups should be stressed before smaller groups, multiple-joint exercises before single-joint exercises, and higher-intensity efforts before those of lower intensity.

 Rest periods of 2 to 3 min or more should be incorporated between heavy loads for novice and intermediate lifters; for advanced lifters, 1 to 2 min may suffice.

 The ability of a muscle or muscle group to generate force varies throughout the full range of movement.

 While both machine-based exercises and free weights can be used for novice and intermediate lifters, for advanced lifters the emphasis should be placed on free weights.

 When neutral testing devices are used, strength gains from free-weight programs and machine-based programs are similar.

 Electrical stimulation can be successfully used in rehabilitating athletes but has no additional benefits when used to supplement resistance training in healthy athletes.

 Exercises aimed at improving core stability may benefit sport performance by providing a foundation for greater force production and force transfer to the extremities while stabilizing other parts of the body. However, direct evidence of such a benefit is lacking.

In Review

 Anaerobic and aerobic power training programs are designed to train the three metabolic energy systems: the ATP-PCr system, the anaerobic glycolytic system, and the oxidative system.

 Interval training consists of repeated bouts of high- to moderate-intensity exercise interspersed with periods of rest or reduced-intensity exercise. For short intervals, the rate or pace of activity and the number of repetitions are usually high, and the recovery period is usually short. Just the opposite is the case for long intervals.

 Both the exercise rate and the recovery rate can be closely monitored with use of a heart rate monitor.

 Interval training is appropriate for all sports. The length and intensity of intervals can be adjusted based on the sport requirements.

 Continuous training has no rest intervals and can vary from LSD training to high-intensity training. Long, slow distance training is very popular for general fitness training.

 Fartlek training, or speed play, is an excellent activity for recovering from several days or more of intense training.

 Interval-circuit training combines interval training and circuit training into oneworkout.

 High-intensity interval training is a time-efficient way to induce many adaptations normally associated with traditional endurance training. In addition to consuming less of the athlete's time, it can be used to provide variety to the training.

Study Questions

1.Define and differentiate the terms strength, power, and muscular endurance. How does each component relate to athletic performance?

2.Define aerobic and anaerobic power. How does each relate to athletic performance?

3.Describe and provide examples for the principles of individuality, specificity, reversibility, progressive overload, and variation.

4.What factors need to be considered when one is designing a resistance training program?

5.What would be the appropriate range for resistance and repetitions when one is designing a resistance training program targeted to develop strength? Muscular endurance? Muscular power? Hypertrophy?

6.Describe the various types of resistance training and explain the advantages and disadvantages of each.

7. What type of training program would likely provide the greatest improvement for sprinters? Marathon runners? Football players?