A workout once in a blue moon won’t do it, she says: you really have to exercise regularly, since hormone levels largely return to baseline after you exercise. That said, there’s an effect that accrues over time, which is what you want to harness by being active at least a few times a week. “What I’d caution readers is not to view our results as ‘one 20-minute moderate exercise will be a cure for all inflammatory conditions,’” says Hong. “These significant immune effects we observed occurred immediately with one bout of exercise, and likely will occur each time one exercises. So every time you exercise you’d see this effect, which will be cumulative over time.”
One of the easiest ways to tone those arms fast is by incorporating some bicep curls into your routine. Simply raising and lowering a weight in a 180-degree range of motion, starting with your arm extended along your side, and bringing it up toward your shoulder, can yield serious definition in a hurry. Fortunately, this exercise doesn’t require a fancy gym membership or even special equipment; while it’s not hard to find a set of dumbbells for under $10, you can also use household products, like gallon jugs of water or soup cans to get the same result.
And perhaps one of the best new findings about exercise — especially if you, like many people, struggle to find the time to fit it into a busy day — is that all those benefits of physical activity can be had even if you only squeeze in a few minutes of exercise a day. While doctors used to think that we needed to engage in 30 to 60 minutes of exercise a day, new research is finding that we can see benefits with shorter bursts of physical activity. “As little as 15 minutes a day of high-intensity activity that leaves you breathless, like swimming, can kick start your metabolic rate and reduce body fat and increase muscle mass,” says Dr. Berger.
The workout includes a dynamic warm-up to get your blood flowing and prep your body for the rest of the work ahead, and a cool-down to help you slow back down and wrap it all up. If you want to make the workout more challenging—maybe you've done it a handful of times and are ready to turn things up a notch—add weights to the lunge and squat movements. You can also, like Sims said, add another round of the main strength circuit.
Endorphins, amiright? The link between exercise and happiness has been well-studied, and the results are very positive (just like you’ll be after some gym time). One study from the University of Vermont found that just 20 minutes of exercise can boost your mood for 12 hours. Cardio and strength training can both give you a lift, and 30-60 minutes of exercise three to five days a week is optimal for mood benefits, according to the U.S. Office of Disease Prevention and Health Promotion.