Optimal Physical Health
The Surgeon General has determined that lack of physical activity is detrimental to your health and recommends moderate activity: 150 calories per day or 1000 calories per week. The American College of Sports Medicine suggests all adults should engage in 30 minutes or more of moderately intense physical activity daily. This level of activity corresponds to 200 kcals a day (Pate RR, Pratt M, Blair SN, et al 1995). See Calorie Expenditure Calculator.
Other authorities suggest that the least amount of activity for optimal physical health is about 1500-2000 kcals a week of light and moderately intense activities. Additional physical health benefits come with increased intensity and eventually level off at around 3500 kcals per week (Peterson & Bryant 1995).
Children and adolescents are recommended to engage in at least 60 minutes of physical activity on most, and preferably all, days of the week (USDA 2005). For ideal BMI, the minimum recommended daily steps for 6-12 year old children are 12,000 steps/day for girls and 15,000 steps/day for boys (Tudor Locke et al 2004). See Step Distance Converter.
The ACSM recommends to target a weekly exercise expenditure of approximately 1000 kcals a week (e.g. 3 sessions of 300 Calories or 4 sessions of 200 Calories) (ACSM 1995). See Calorie Expenditure Calculator.
A review of the scientific literature suggests that moderately intense aerobic activity needs to be performed most days of the week to bring about significant fat loss. Some sources recommend brisk walking progressing to 45 minutes or more daily. Other authorities recommend working up to 60-90 minutes of daily physical activity for weight loss.
The USDA recommends at least 60 to 90 minutes of daily moderately intense physical activity while not exceeding caloric intake requirements to sustain weight loss in adulthood. About 60 minutes a day may be needed to prevent weight gain. (USDA 2005).
High Intensity Interval Training (HIIT) has shown to be more effective in lowering body fat than traditional aerobic exercise. Begin such a program only after a period of general conditioning for adequate adaptation and greater participant adherence. However, the combination of aerobic and anaerobic exercise may utilize more fat than either type of exercise alone, particularly since greater recovery is required between sessions of anaerobic activity. Also see Fat Loss.
Alternating weight-bearing with non-weight-bearing exercises every other day may be recommended to minimize the repetitive orthopedic stresses of exercising daily. See Overtraining.
For cardiorespiratory fitness, ACSM (2000) recommends intensities between 55% and 65% to 90% of maximum heart rate, or between 40% and 50% to 85% of oxygen uptake reserve (VO2R) or Heart Rate Reserve (HHR). ACSM suggests low-fit or deconditioned individuals may experience improvements at exercise intensities of only 40% to 49% HRR or 55% to 64% Maximum Heart Rate (HRmax). Skinner et. al. (2004) remarks, "Because 'quite unfit', sedentary subjects are already doing enough activity in their daily lives to maintain a VO2 ventilatory threshold at levels that are generally greater than 50% VO2R, it is not necessary to reduce the prescribed intensity to 40% VO2R, as recommended by the ACSM."
Cardiovascular fitness improvement is dependent upon the exercise program (mode, frequency, duration, intensity of exercise) as well as the individual participant (fitness level, age, and health status). Also see Running Risk / Benefit Study. For the average person, aerobic training programs typically produce an increase of VO2 of 5% to 20% (Pollock 1973). Those with low initial levels of fitness and those exhibiting large losses of body weight will exhibit up to a 40% improvement of VO2 max. Similarly, only modest improvements may be expected from individuals with high initial levels of fitness or those who exhibit little change in body weight (ACSM 1995).
Intensity, duration, and frequency are somewhat inversely proportional. If one component increases, the others may be decreased to a degree. When a program has been established, intensity is the least forgiving component for cardiovascular fitness. An increase in duration or frequency cannot make up for a significant decrease in intensity without a decrease in cardiovascular fitness.
Cardiovascular fitness can be expressed as maximum oxygen uptake (VO2 max). This is the amount of oxygen the body can utilize per unit weight per unit time [ml / (kg x min)]. Since measuring oxygen consumption directly is not feasible, many methods of measuring VO2 max have been developed. These cardiovascular tests have been validated by measuring the direct correlation of VO2 max and estimate cardiovascular fitness. These results of a cardiovascular fitness test can be used to prescribe an exercise program based on the participant's fitness level. See Aerobic Testing.
The inclusion of resistance training is important for a sound overall exercise program but will not significantly increase VO2 max. Circuit weight training (eg: 10 to 15 repetitions with 15 to 30 seconds between weight stations) improves VO2 max an average of about 5%. For this reason circuit training is not generally recommended as an activity to improve cardiovascular fitness. (ACSM 1995).
In general, the best exercise for a specific sport is the sport itself. Additional exercises should condition the particular components of fitness specific to the sport. The specific muscles involved, type of muscular contraction, intensity, duration, recovery time, and motor skill must be considered. Specific components of the sport may need to be trained separately.
Short Sprint Interval Training and Interval Training can supplement traditional cardiovascular fitness Training (see Sports Conditioning Program). Periodization may be implemented for continued progress and for specialization of particular components. For periodization examples, see Marathon Training, Cycling, Triathlon, and weight training periodization. Also see Training Specificity.
American College of Sports Medicine (1995) Principles of Exercise Prescription, William & Wilkins, 5.
American College of Sports Medicine (2000) ACSM's Guidelines for Exercise Testing and Prescription, 6; 145.
Gaskill SE, et. al. (2004) %heart rate reserve is better related to %VO2max than to VO2 Reserve: The Heritage Family Study. Medicine & Science in Sports & Exercise, 36(5) S3.
Peterson PA, Bryant CX (1995) The StairMaster Fitness Handbook, 2; 5-7.
Pollock ML (1973) The quantification of endurance training programs. In Exercise and Sports Sciences Reviews, ed. JH Wilmore, 1: 155-188, New York; Academic Press.
Skinner JS, et. al. (2004) Evaluation on ACSM guidelines on prescribing exercise intensity for "quite unfit": The Heritage Family Study. Medicine & Science in Sports & Exercise, 36(5) S3.
Tudor-Locke C, Pangrazi RP, Corbin CB, Rutherford WJ, Vincent SD, Raustorp A, Tomson LM, Cuddihy TF 9 (2004). BMI-referenced standards for recommended pedometer-determined steps/day in children. Prev Med. Jun; 38(6): 857-64.
USDA (2005) Dietary Guidelines for Americans, viii.