COLUMNS: Clinical Applications
Consistent commitment to exercise training results in substantial health and fitness benefits, inspiring a colleague of mine to label exercise a virtual “polypill” for the benefits it provides. The fitness benefits associated with long-term exercise training include increased cardiorespiratory function and efficiency manifested in part by increased aerobic power (V˙O2max), decreased percentage body fat, increased muscle strength and endurance, and enhanced flexibility. The amount of benefit that an individual experiences as a result of an exercise training program is dependent on factors such as initial fitness level, genetic potential, and others. Perhaps, however, the most important factor influencing the gains in fitness experienced with exercise training is the exercise dosage. The exercise training dosage is a composite of intensity, frequency, and duration, and these variables can be manipulated during the course of a training program in an attempt to produce optimal gains in fitness. How the exercise dosage is manipulated throughout the course of a training program has a profound influence on exercise training outcomes and also may influence long-term adherence to exercise training. This column will discuss the research literature that has investigated the exercise dosage necessary to maintain fitness gains of cardiovascular efficiency, muscle strength, and flexibility and how the findings of this research may relate to enhancing adherence to exercise training programs.
RESEARCH REGARDING EXERCISE DOSAGE AND MAINTAINING FITNESS GAINS
There is little argument that when exercise training is stopped or significantly reduced, training gains related to cardiorespiratory and muscular strength are reversed to varying degrees over time (2,6,14). Many factors influence the degree and rate of change in fitness, including the fitness level when de-training began (those with higher fitness levels decline less rapidly); age; how long and how intensely the individual had been training (those who have trained longer and more intensely decline less rapidly); the level of daily habitual activity; and genetic disposition (1,7).
Reversal of fitness gains as a result of de-training occurs as soon as 1 to 2 weeks after exercise training stops, whereas continuing to exercise at reduced volume may attenuate these changes (3,12,13). The fact that a reduced volume of training can attenuate the loss of fitness gains begs the question: how much can an individual reduce his or her training and still maintain the gains that have been made? Several research studies have manipulated the components of the exercise dosage in an attempt to address this question. In a series of elegantly controlled experiments, Hickson and associates (9–11) found that if the intensity of training remained unchanged, aerobic power was maintained for up to 15 weeks even when frequency and duration of training were reduced by as much as two thirds. In converse, when frequency and duration of training remained constant and intensity of training was reduced by one third or two thirds, then aerobic power was significantly reduced. Thus, it appears that to maintain gains related to aerobic power, intensity is the key variable of the dosage.
Although research literature is not as extensive, resistance training-induced improvements in muscle strength and power have been shown to deteriorate quickly with complete cessation of exercise (2,4, 5,8,12). In findings analogous to those associated with the maintenance of aerobic power, Fatouros and colleagues (4,5) demonstrated that muscular strength may be maintained by as little as a single session per week of moderate- to hard-intensity training (equivalent to at least 60% of an individual’s one-repetition maximum lift).
Although few studies have investigated the impact of de-training on flexibility, current data indicate that improvements in joint range of motion reverse within 4 to 8 weeks of cessation of stretching (5,15). There is limited research, however, on the effects of reducing the frequency or duration of stretching exercise, although it has been demonstrated that individuals who reduced participation in stretching exercise from daily to 2 to 3 days per week maintained joint range of motion (5,15). In summary, research findings support the conclusion that as long as the intensity of training is maintained, a reduced volume of exercise dosage through reductions in duration and/or frequency will likely not result in a loss of fitness gains.
IMPACT OF RESEARCH FINDINGS ON EXERCISE ADHERENCE
Conservative estimates indicate that more than 50% of clients who begin an exercise program will quit that program after 10 to 12 weeks. With all the documented health and fitness benefits of exercise, why is long-term adherence to a program so difficult? The answer to this query, in part, may lie in how an individual applies the “medicine” or the dosage of exercise training during the course of training. The observation that fitness gains can be maintained with reduced exercise volume has significant implications for exercise adherence. Many exercise training programs designed for the recreational athlete do not consider recovery. A key for a client staying with their exercise program may lie in the concept of including adequate recovery using short-term volume reductions in dosage. The good news is that the research literature supports that the volume of exercise necessary to maintain the gains in fitness experienced with training is less than that required to achieve gains, and this finding is consistent across all areas of fitness, including cardiorespiratory fitness, muscular strength, and flexibility. The Table identifies a sample client and how the exercise volume could be reduced while maintaining the fitness gains achieved.
CONCLUSIONS AND TAKE-HOME MESSAGE
The most important variable of the exercise dosage that will allow an individual to maintain the gains they have achieved is the intensity, and this observation is consistent across each of the fitness benefits that an exercise program provides. Reducing the exercise volume while maintaining the intensity of training at critical times during the exercise program may allow for recovery and maintaining enthusiasm for exercise training, both of which are variables important to long-term exercise adherence. The next column topic will be “periodization” of an individual’s exercise program. Periodization is a more systematic way to add “planned” recovery into your training program.
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Strength training and detraining effects on muscular strength, anaerobic power, and mobility of inactive older men are intensity dependent. Br J Sports Med
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© 2012 American College of Sports Medicine
15. Willy RW, Kyle BA, Moore SA, Chleboun GS. Effects of cessation and resumption of static hamstring muscle stretching on joint range of motion. J Orthop Sports Phys Ther