The American College of Sports Medicine has reviewed its health and fitness guidelines in its revised Position Stand on The Recommended Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory and Muscular Fitness, and Flexibility in Healthy Adults (Med. Sci. Sports Exerc., Vol. 30, No. 6, pp 975 - 991, 1998). There is much to gain from a thorough reading of this new Position Stand and just a few of the main points relating to cardiorespiratory fitness and body composition are highlighted here in this brief review.

Cardiorespiratory Fitness and Body Composition

With respect to cardiorespiratory fitness, body composition and frequency of training, the guidelines remain the same as in previous Position Stands, namely 3 - 5 days per week. Similarly, the duration of training recommended is a familiar 20 - 60 minutes. However, the ACSM advocates either continuous or intermittent aerobic activity, with intermittent bouts being a minimum of 10 minutes. And, since the duration of training is largely determined by the intensity of the exercise bout, it is recommended that lower intensity be conducted over a longer period of time (30 minutes or more). Adults not training for athletic competition are additionally advised to choose moderate intensity activity of longer duration since this poses fewer potential injury hazards and greater adherence when compared to high intensity exercise.

Recommended activities are once again those that involve large muscle groups which are rhythmical and aerobic in nature. The list has been extended to include activities such as walking-hiking, running-jogging, cycling-bicycling, cross-country skiing, aerobic dance, group exercise (and this term encompasses activities such as step aerobics, slide board exercise, strength aerobics, and spinning, usually performed to music), rope skipping, rowing, stair climbing, swimming, skating and various endurance game activities or some combination thereof.

There is a slight change compared to previous guidelines with respect to intensity of training. Here, the ACSM advocates 55/65% - 90% of maximum heart rate or 40/50% - 85% maximum oxygen uptake reserve or heart rate reserve. The lower starting points in these intensity bands have been incorporated in order to accommodate those individuals who are very unfit.

Muscular Strength and Endurance, Body Composition and Flexibility

Under this heading, the ACSM recommends resistance training as an essential part of any adult fitness programme. It should be progressive, individualised and target all major muscle groups. One set of 8 - 10 exercises for the major muscle groups, performed 2 - 3 times weekly is recommended, with 8 - 12 repetitions of each exercise or in the case of older or more frail people 10 - 15 repetitions is preferred. The ACSM notes that multiple set programmes may provide greater benefit where time is not an issue.

The guidelines are less precise when it comes to flexibility training. Flexibility exercises should be included in the adult fitness programme, to develop and maintain range of motion. Major muscle groups should be stretched a minimum of 2 - 3 days each week, using appropriate static and/or dynamic techniques.

The Revisions Explained

The ACSM points out that since the original position statement was published in 1978, and subsequently revised in 1990 an important distinction has been made between physical fitness as it relates to health versus fitness. In other words, the quantity and quality of exercise needed for health benefits may well be different to that required to develop fitness. In particular, lower intensity activity may reduce the risk for certain chronic degenerative diseases and improve metabolic fitness and yet may not be of sufficient quantity or quality to improve maximum oxygen uptake.

Thus the recognition in the guidelines of the fact that there are health benefits to be gained from regular physical activity, performed frequently, for a long duration but at a relatively lower intensity than advocated in previous guidelines (for example, 55 - 64% MHR). This is in line with recommendations from other organisations, including the Office of the US Surgeon General. Effectively, this means that there is a dose - response relationship with respect to exercise and health benefits which is also individually specific. In other words, going from a sedentary state to a minimal level of physical activity can confer significant health benefits, with further benefits being gained from increasing the intensity, duration and frequency of physical activity or exercise. The decrease in the minimal recommended intensity allows for the fact that the person with a very low level of fitness can achieve a significant training effect with a training heart rate as low as 40 - 50% of HRR.

Volume of Training

It is interesting to note that this Position Stand reports extensively on the importance of the total volume of training when it comes to improving fitness and cardiorespiratory fitness in particular; depending upon the quantity and quality of training, improvement in maximum oxygen uptake ranges from10% to 30%. However, it is also acknowledged that there is a genetically determined capacity to adapt to physical training.

Of interest to those instructors (and several presenters) who are less familiar with the lacate threshold and seem to think that it is always found at a relatively fixed percentage of maximum oxygen uptake is the literature review on this topic within this Position Stand. The ACSM states, for most untrained individuals, the lactate threshold occurs between 40% and 60% of maximum oxygen uptake. Furthermore, and as is well known by endurance coaches in many sports, it is also acknowledged that the lactate threshold can be increased independently of maximum oxygen consumption and is correlated strongly with endurance capacity.

This Position Stand is also the first to acknowledge that as long as exercise is performed above a minimum intensity threshold, the total volume of training (in kcal) is what is most important in terms of either fitness development or maintenance. In other words, improvements will be similar for exercise performed at a lower intensity for a longer duration when compared to exercise performed at higher intensity for less time, as long as the energy expenditure is the same. However, higher intensity activity carries a higher injury risk and lower exercise adherence.

The ACSM also notes that increasing the exercise frequency leads to increased training effects as far as maximum oxygen uptake is concerned, but the additional improvement tends to plateau at around 3 days per week. Training greater than five times weekly leads to negligible improvements in maximum oxygen uptake, but a significantly increased injury risk. However, the optimal training frequency for improving the lactate threshold and metabolic fitness are not known and may or may not be similar to that for improving maximum oxygen uptake.

Type of Activity

It would appear that as long as the total energy expenditure is similar, training adaptations are largely independent of the mode of aerobic activity undertaken. Cross training may well be beneficial as a consequence when attempting to achieve a well balanced training effect. Impact activities are associated with an increased risk of injury, particularly in the elderly, the unfit and the overweight.

Maintenance of Training

Exercise must be continued on a regular basis if fitness is to be maintained. A reduction in cardiorespiratory fitness may be seen after just two weeks of inactivity and pre-training levels of fitness will be reached after as little as ten weeks of detraining. More commonly, a loss of 50% of the initial improvement in maximum oxygen uptake obtained through training is seen after 4 - 12 weeks of inactivity. Yet decreasing training volume by up to two thirds whilst keeping the intensity the same seems to maintain fitness. However, intensity seems to be the key since when this is reduced and training frequency and duration are kept the same, fitness declines. Similar responses have been seen with strength training.

Weight Control and Body Composition

As all instructors are aware, exercise without dieting tends to have only a very small effect on total body mass and fat mass loss. The ACSM acknowledges this, the most successful studies in terms of weight loss have been those that combined diet and exercise to optimise the energy deficit. Also, it appears that individuals who combined exercise with their dietary regimens maintain their weight loss more effectively. Exercise should involve the expenditure of 250 - 300 kcal per session (75 kg individual) as a minimum, performed at least three times each week. Energy expenditures lower than this (200 kcal) per session may be effective if carried out at least four times each week. However, as the ACSM states, if the primary purpose of the training programme is for weight loss then regimens of greater frequency and duration of training and moderate intensity are recommended.