Multiple recommendations exist regarding the amount of exercise activity needed for health and well-being. One seminal longtitudinal study performed on Harvard graduates (Sesso, 2000) noted that 2000-3000 kilocalories worth of activity weekly (walking, stair climbing, recreational activities) was associated with the lowest risk ratio of cardiovascular heart disease; while a modest 1000 kcal weekly reduced coronary heart disease risk by 20%. Two trials (Dunn, 1999; Andersen, 1999) suggest that moderate-intensity conditioning programs may confer reduced CV risk similar to more structured, vigorous programs in obese, sedentary individuals. However, short-term improvements in risk may not necessarily translate into long-term reduction in morbidity and mortality.

CDC recommends 30-45 minutes of brisk walking, cycling, house or yardwork daily.

The Surgeon General recommends 30 minutes of moderate activity on most days of the week.

The 1995 Dietary Guidelines for Americans suggests 30 minutes or more of moderate activity on all or most days of the week.

Emerging data suggest that briefer bouts of exercise throughout the day may also offer health benefits. A regular activity program reduces the incidence of CV disease, hypertension, diabetes and colon cancer. Additional benefits include reduction in depression and anxiety as well as maintenance of functional status throughout life. Weight bearing activity is essential in childhood and adolescence for normal skeletal development and the achievement of peak bone mass.

The American College of Sports Medicine (ACSM) has published more specific exercise recommendations:

Recommended Quality and Quantity of Exercise for Developing and Maintaining Cardiorespiratory and Muscular Fitness, and Flexibility in Healthy Adult
Exercise Type	Frequency	Intensity	Duration	Mode of Activity	Comments
	3-5 days weekly	55/65%-90% of maximum heart rate or 40/50%-85% maximum oxygen uptake reserve (VO2R)	20-60 minutes of continuous or intermittent activity. Bouts should be at least 10 minutes.	Any activity that uses large muscle groups continuously.	Less trained individuals should adopt lower intensity and higher duration.
	2-3 days weekly	Repetition Maximum (RM) is the maximal number of times a load can be lifted, using good form and technique, before fatigue.	One set of 8-10 exercises that conditions the major muscle groups.	8-12 repetitions of each exercise. 10-15 repetitions for older or frail individuals.	Major muscle groups are back, arms, shoulders, chest, abdomen, hips and legs.
	2-3 days weekly	4 repetitions per muscle group.	Static stretches hold for 10-30 seconds, PNF includes a 6 second contraction followed by a 1-30 second assisted stretch.	3 types: Static, proprioceptive neuromuscular facilitation (PNF), and ballistic. Stretch the major muscle/ tendon groups.	Improves joint range of motion and function, enhances muscular performance, prevents and alleviates musculo-skeletal injury.

• Lower levels of physical activity than those stated above may offer some reduction of risk for chronic degenerative disease and improve metabolic fitness, yet may not improve VO2max.
• Middle-aged sedentary and older exercisers may take a longer period of adaptation before demonstrating a response to a program.
• Higher-intensity exercise is associated with greater CV risk and orthopedic injury. Moderate intensity and longer duration is advised for most adults.

Water is an essential component of any activity or exercise program to maximize performance, prevent dehydration, injury and to speed recovery.

1. The timing and quantity of fluid replacement requires planning on the part of the exerciser.
2. Fluid intake should replace sweat loss during exercise. Overall fluid intake should be 150% of the fluid loss during and after exercise. Many athletes can sweat 2-3 liters hourly.
3. Monitoring body weight pre and post exercise helps in calculating fluid needs. Drink 24 oz. of fluid for each pound lost during exercise in order to rehydrate within 6 hours of an exercise session or competitive event.
4. Sweat contains an average sodium concentration of 50 mEq (1.15 gm Na) per liter. Prolonged sweat loss with plain water replacement may produce hyponatremia.
5. Thirst is not a reliable mechanism to promote adequate fluid intake. A water deficit of 1% of body weight may be present before thirst becomes apparent.
6. The color and volume of urine is a helpful indicator of hydrational status.
7. Flavored, sweetened beverages with some sodium may promote greater fluid intake than plain water.
8. Exercise at altitude >8200 feet may produce extraordinary losses through respiration and diuresis. Fluid intake needs may be as high as 3-4 liters daily.
9. Ideal beverages contain 6-10% carbohydrate (CHO) to provide sufficient CHO and facilitate gastric emptying.

Fluid Requirement During Prolonged Exercise and Competition
	Fluid Requirement	Type of Fluid
2 hours before competition	400-600 ml (14-21 oz.)	Water
Immediately before competition or sustained activity	500 ml (17 oz.)	Water
During competition or exercise up to 60 minutes1	150-350 ml (5-12 oz.) every 15-20 minutes. More if sweat losses are excessive.	Water for most activities. High intensity activity performance may be enhanced with carbohydrate.
Exercise or competition lasting >60 minutes	150-350 ml (5-12 oz.) every 15-20 minutes. More if sweat losses are excessive.	Beverage with <8% carbohydrate concentration. May need beverage with 500-700 mg Na/L for activity >3 hours.2 (or consume salt in food)
1. ACSM, ADA and Dietitians of Canada Position Stand: Nutrition and Athletic Performance (2000). Medicine & Science in Sports & Exercise (32(12)2130-2145. 2. Commercial sports beverages contain 55-110 mg Na/Liter

Fluids 2000 - Dehydration and Heat Illness

This Heat Index Chart provides general guidelines for assessing the potential severity of heat stress. Individual reactions to heat will vary. It should be remembered that heat illness can occur at lower temperatures than indicated on the chart. In addition, studies indicate that susceptibility to heat illness tends to increase with age.

 

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