DO THIS In the Morning
Set Your Alarm
Embrace your inner early bird. British scientists found that when cyclists exercised at 6:45 a.m., they could sustain an intense pace for a longer period compared with when they exercised at 6:45 p.m. Your core body temperature is lower in the a.m., so it takes longer to overheat from exercise performed in warm conditions, says lead researcher Ruth Hobson, M.Sc., a doctoral student at Loughborough University in England. Plus, levels of cortisol (a hormone that helps break down fat for fuel) are higher at daybreak, "which might help you run a little farther, faster, and with more energy," says Hobson.
Hard training taxes your immune system, leaving you susceptible to colds and worse. Reinforce your defenses with probiotics—live, "good" bacteria available in dietary supplements and foods such as yogurt, cultured milk products, miso, and tempeh that maintain a healthy balance of microorganisms in the digestive system. A study in the British Journal of Sports Medicine reported that when elite distance runners took a daily probiotic supplement, they experienced fewer days of cough and cold symptoms; when symptoms did occur, they were less severe. The added stores of good bacteria may strengthen the body's mucous membranes and make it harder for invaders to penetrate, says lead researcher David Pyne, Ph.D. Stay sniffle-free with a daily serving of yogurt or kefir (a cultured milk drink); look for items containing the Live & Active Culture seal, which identifies products high in probiotics, says Tara Gidus, R.D. For year-round health insurance, take a supplement containing 14 to 30 billion active bacteria. "There may be more germs around in winter, but colds can also strike during the summer race season, when they can force runners to miss critical training days," says Gidus.
Down Some D
"Years of evidence suggests that vitamin D improves athletic performance," says Bruce Hollis, Ph.D., of the Medical University of South Carolina. In a recent research review, Hollis found that athletes who absorbed the vitamin through ultraviolet light or supplements exercised faster, stronger, and with greater endurance than those who missed out. Receptors in our muscles and heart absorb the nutrient, which may, in turn, stimulate muscle function, says Hollis. Since sunscreen blocks the wavelengths that produce D, try a supplement instead. Take 2,000 to 4,000 International Units per day, depending on your age.