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Running on Empty:
You're so tired and bored, you can barely stay awake on the elliptical.

Power Up:
Sniff some lemon. Though most aromatherapy studies have had disappointing results, the National Institutes of Health National Center for Complementary and Integrative Health confirms that there's good evidence that the scent of lemon may energize you. In one study at the Ohio State University, researchers found that inhaling the smell of lemon oil boosted subjects' moods and feelings of vigor by up to 20 percent compared with plain water or the scent of lavender. Throw a small bottle of lemon essential oil in your gym bag. When you need a break, put a few drops in your palm, rub your hands together, take a whiff, and keep going!