SUMMARYACSM Position Stand on The Recommended Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory and Muscular Fitness, and Flexibility in Adults. Med. Sci. Sports Exerc., Vol. 30, No. 6, pp. 975-991, 1998. The combination of frequency, intensity, and duration of chr

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ACSM Position Stand: The Recommended Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory and Muscular Fitness, and Flexibility in Healthy Adults

Two quite distinct adaptive responses can be induced in skeletal muscle by regularly performed, strenuous exercise. The nature of the exercise stimulus determines the type of adaptation. One type of adaptation involves hypertrophy of the muscle cells with an increase in strength; it is exemplified in its most extreme form by the muscles of weight lifters and body builders. The second type of adaptation involves an increase in the capacity of muscle for aerobic metabolism with an increase in endurance and is found in its most highly developed form in the muscles of competi­ tive middleand long-distance runners, long-distance cross-country skiers, bicy­ clists, and swimmers. Although many types of physical activity can bring about varying degrees of both types of adaptation in the same muscle, it does appear that these adaptations can occur quite independently of each other in their most extreme forms. For example, the hypertrophied muscles of weight lifters do not appear to have an increased respiratory capacity (45), whereas the muscles of rodents trained by prolonged daily running, which have a large increase in respiratory capacity, are not hypertrophied (56, 92) and show no increase in strength (12). This review deals with the biochemical adaptations induced in skeletal muscle by the endurance type of exercise and with the physiological consequences of these adaptations.

Biochemical adaptations to endurance exercise in muscle.

Purpose: The purpose of this study is to review the effects of aerobic exercise training (AET) on blood lipids and assess dose-response relationships and diet interactions. Methods: We reviewed papers published over the past three decades pertaining to intervention trials on the effects of ≥ 12 wk of AET on blood lipids and lipoprotein outcomes in adult men and women. Included were studies with simultaneous dietary and AET interventions, if they had appropriate comparison groups. Studies were classified by the participants' relative weights expressed as mean BMIs. Information was extracted on baseline characteristics of study subjects, including age, sex, and relative baseline cholesterol levels; details on the training programs; and the responses to training of body weight, VO 2max , and blood total cholesterol (TC) and low-density lipoprotein-cholesterol (LDL-C), high-density lipoprotein-cholesterol (HDL-C), and triglyceride (TG). Results: We identified 51 studies, 28 of which were randomized controlled trials. AET was generally performed at a moderate to hard intensity, with weekly energy expenditures ranging from 2,090 to >20,000 kJ. A marked inconsistency was observed in responsiveness of blood lipids. The most commonly observed change was an increase in HDL-C (with reductions in TC, LDL-C, and TG less frequently observed). Insufficient data are available to establish dose-response relationships between exercise intensity and volume with lipid changes. The increase in HDL-C with AET was inversely associated with its baseline level (r = -0.462), but no significant associations were found with age, sex, weekly volume of exercise, or with exercise-induced changes in body weight or VO 2max . Conclusion: Moderate- to hard-intensity AET inconsistently results in an improvement in the blood lipid profile, with the data insufficient to establish dose-response relationships.

Response of blood lipids to exercise training alone or combined with dietary intervention.

Dose-response relationships between exercise training volume and blood lipid changes suggest that exercise can favourably alter blood lipids at low training volumes, although the effects may not be observable until certain exercise thresholds are met. The thresholds established from cross-sectional literature occur at training volumes of 24 to 32 km (15 to 20 miles) per week of brisk walking or jogging and elicit between 1200 to 2200 kcal/wk. This range of weekly energy expenditure is associated with 2 to 3 mg/dl increases in high-density lipoprotein-cholesterol (HDL-C) and triglyceride (TG) reductions of 8 to 20 mg/dl. Evidence from cross-sectional studies indicates that greater changes in HDL-C levels can be expected with additional increases in exercise training volume. HDL-C and TG changes are often observed after training regimens requiring energy expenditures similar to those characterised from cross-sectional data. Training programmes that elicit 1200 to 2200 kcal/wk in exercise are often effective at elevating HDL-C levels from 2 to 8 mg/dl, and lowering TG levels by 5 to 38 mg/dl. Exercise training seldom alters total cholesterol (TC) and low-density lipoprotein-cholesterol (LDL-C). However, this range of weekly exercise energy expenditure is also associated with TC and LDL-C reductions when they are reported. The frequency and extent to which most of these lipid changes are reported are similar in both genders, with the exception of TG. Thus, for most individuals, the positive effects of regular exercise are exerted on blood lipids at low training volumes and accrue so that noticeable differences frequently occur with weekly energy expenditures of 1200 to 2200 kcal/wk. It appears that weekly exercise caloric expenditures that meet or exceed the higher end of this range are more likely to produce the desired lipid changes. This amount of physical activity, performed at moderate intensities, is reasonable and attainable for most individuals and is within the American College of Sports Medicine's currently recommended range for healthy adults.

Blood lipid and lipoprotein adaptations to exercise: a quantitative analysis.

Purpose: There is strong and consistent evidence that a single exercise session can acutely reduce triglycerides and increase high-density lipoprotein (HDL) cholesterol (HDL-C) reduce blood pressure, and improve insulin sensitivity and glucose homeostasis. Such observations suggest that at least some of the effects on atherosclerotic cardiovascular disease (ASCVD) risk factors attributed to exercise training may be the result of recent exercise. Results: These acute and chronic exercise effects cannot be considered in isolation. Exercise training increases the capacity for exercise, thereby permitting more vigorous and/or more prolonged individual exercise sessions and a more significant acute effect. The intensity, duration, and energy expenditure required to produce these acute exercise effects are not clearly defined. The acute effect of exercise on triglycerides and HDL-C appears to increase with overall energy expenditure possibly because the effect maybe mediated by reductions in intramuscular triglycerides. Prolonged exercise appears necessary for an acute effect of exercise on low-density lipoprotein (LDL) cholesterol (LDL-C) levels. The acute effect of exercise on blood pressure is a low threshold phenomenon and has been observed after energy expenditures requiring only 40% maximal capacity. The acute effect of exercise on glucose metabolism appears to require exercise near 70% maximal, but this issue has not been carefully examined. Conclusions: Exercise has definite acute effects on blood lipids, blood pressure, and glucose homeostasis. Exercise also has acute effects on other factors related to atherosclerosis such as immunological function, vascular reactivity, and hemostasis. Considerable additional research is required to define the threshold of exercise required to produce these putatively beneficial effects.

The acute versus the chronic response to exercise.

HE EFFECT of six months of physical conditioning upon a number of physiologic variables has been investigated in a group of previously sedentary middle-aged men.’ This study was performed to help lay the groundwork for a possible large-scale, long term investigation of whether or not regular exercise protects against the development of coronary heart disease. A major aim of the present study was to try to

Effects of a six month program of endurance exercise on the serum lipids of middle-aged men

Physical fitness of champion athletes

Nineteen volunteer men, between 28–39 years of age (mean 32.5) were randomly assigned to one of the two experimental groups. Group I exercised two days a week, and Group II four clays a week for twenty weeks. Exercise sessions were 30 minutes in duration and consisted of continuous walking,

Effects of frequency of training on working capacity, cardiovascular function, and body composition of adult men

Physical Fitness Appraisal and Guidance-By Thomas Kirk Cureton, Jr., and Frederick W. Kasch, assisted by John Brown and W. G. Moss. St. Louis: Mosby, 1947. 566 pp. Illus. Price, $6.00. The purpose of this reference as stated in the preface is to provide an " interpretative book on physical fitness " for physicians and nurses as well as physical educators. Many of the data presented are based on a project designed to promote physical education for first year students in the Colleges of Medicine, Dentistry, and Pharmacy at the University of Illinois. Appraisal of physical fitness is approached from the point of view of determining physique, organic efficiencv, and motor fitness. This is the same emphasis described in a previous publication by Cureton.* Mention is made of health examination tests and other approaches to fitness but the emphasis on the three approaches selected is justified on the basis of practicality and previous research in these areas. Considerable attention is given to a review of the literature dealing with methods of appraising body types, weight, cardiovascular and respiratory fitness, strength and motor performance. In fact the strength of the book lies in the extensive bibliography it presents, since many basic studies are cited. The project conducted with 110 first year medical students to stimulate their interest in physical education and increase their understanding of physical

https://ajph.aphapublications.org/doi/pdfplus/10.2105/AJPH.38.7.1020

Physical fitness appraisal and guidance

(1941). Flexibility as an Aspect of Physical Fitness. Research Quarterly. American Association for Health, Physical Education and Recreation: Vol. 12, Physical Fitness, pp. 381-390.

Thomas K. Cureton

Papers

Effects of a six month program of endurance exercise on the serum lipids of middle-aged men

Physical fitness of champion athletes

Effects of frequency of training on working capacity, cardiovascular function, and body composition of adult men

Physical fitness appraisal and guidance

Flexibility as an Aspect of Physical Fitness