INCREASE ENERGY

THE PROBLEM: By 3 p.m., you're nodding off at your desk.
THE FIX: Simply standing up gets more blood — and energizing oxygen — pumping to your brain; after walking briskly for a few minutes, your whole body (including your sluggish mind) becomes more engaged. "You don't even have to work up a sweat," says Robert E. Thayer, professor of psychology at California State University Long Beach and author of Calm Energy: How People Regulate Mood with Food and Exercise. In one of Thayer's studies, subjects either went for a brisk 10-minute walk or ate a candy bar. The walkers had increased energy for up to two hours, while the snackers saw their immediate energy boost drop off within an hour — and after two hours were even more lethargic than before.
TRY THIS: When you have time for more than a couple of laps through your cubicle maze, personal trainer Kacy Duke of Equinox Fitness recommends circuit work for the biggest jump-start. Count to 10 jumping rope, then do 8 push-ups, then 12 crunches. Next, graduate to 20 seconds jumping rope, 10 push-ups, 15 crunches. Keep upping the ante until you've been active for at least 15 minutes. (Don't push yourself for more than 30, though — the idea is to get energized, not exhausted.)
BONUS: Whatever workout you choose, do it outside when possible. Research has shown that an identical workout will yield a more substantial energy payoff when it's done outdoors — "even when the sun isn't shining," says Thomas Plante, professor of psychology at Santa Clara University, who has published several dozen studies on exercise and mood.

FEEL HAPPIER

THE PROBLEM: It's been a couple of weeks, and you can't seem to snap out of this woe-is-me funk.
THE FIX: Even short bursts of exercise (again, we're talking 10 minutes) can elevate the serotonin and norepinephrine levels in the brain that perk up your mood, while longer-term workout regimens have proved comparable to prescription antidepressants. One particularly rigorous study, published in the Archives of Internal Medicine, found that people suffering from clinical depression who exercised — walking, jogging, or biking for 30 minutes three times a week — for four months reported increases in happiness and self-esteem in line with those who had been taking Zoloft for the same period. And working out with music or a friend has also been shown to augment the antidepressant effects of exercise. You might want to avoid the gym, though — it's a hotbed of what psychologists call "social comparison." "You can start thinking, These people are more attractive, more fit than I am, and walk out of there more depressed," says Plante.
TRY THIS: Movements that are literally uplifting are most likely to boost your heart rate and your spirits, says Duke, who likes to take clients through a series of jump squats when they're feeling blue. Start in a deep squat position with your arms stretched out in front of your body, then jump as high as you can, reaching up toward the ceiling. "After doing them, it's hard to feel powerless anymore," says Duke. "And using only your own body weight — no machines — improves your sense of self."