3. Don’t accelerate your training level too rapidly. You need time to build confidence and accustom your muscles to any new activity. A beginner might benefit initially from working with a trainer to find the optimum level of activity. If you run, follow the 10 percent rule: do not increase mileage by more than 10 percent per week.

25. If you follow a vegetarian diet and lead an active lifestyle, be sure you know what you are doing. Vegetarians who don’t eat dairy foods or other animal products need to use extra care to monitor their consumption of some nutrients that occur mainly or almost exclusively in animal foods. Vitamin B12 deficiency is especially common.

33. Properly formulated sports drinks (those with 6 to 7 percent carbohydrate concentration) are absorbed 30 percent faster than water, and much faster than drinks with carbohydrate concentrations of 8 percent or more. Studies have shown they improve performance and combat fatigue during exercise sessions of an hour or longer because the body can use them right away.