Perform each of these exercises for 30 seconds at a time to begin with and gradually build up to 60 seconds by adding five to 10 second increments as your metabolic conditioning improves. Keep your heart rate high and your rest periods between exercises at 30 seconds or less. Finally, alternate between sets of “non-competitive” moves — i.e. switch between exercises that work your upper body and lower body or front and backside. Doing so will minimize fatigue and help you keep up the intensity throughout the workout.
Bend your knees to lower down into a split squat. Your left knee should ideally form a 90-degree angle so that your thigh is parallel to the ground, and your right knee is hovering above the floor. (Quick position check: your left foot should be stepped out far enough that you can do this without letting your left knee go past your left toes—if you can't, hop your left foot out a bit farther away from the bench.)

It strengthens the brain. Studies have found that working out can lessen the severity of memory problems in older adults, and even decrease the risk of diseases like Alzheimer's. It can also have a positive benefit on the brain function of younger people. Research out of New Zealand shows that exercise improves executive function -- the general brain processes that include planning, memory, reasoning, problem-solving and more.

This may be the most worthwhile reason for exercising there is. Studies have shown how people who exercise are at a significantly reduced risk of developing dementia like Alzheimer’s disease. And even for people who start exercising relatively late in life, brain volume can actually increase over time, as can scores on memory tests, compared to people who don’t exercise (their brains shrunk over time, which is normal part of aging).
Well, good (bad?) news: People who have dedicated their professional lives to defying Newton's First Law (you know them as "personal trainers") don't often have the luxury of skipping a sweat session. Next time you find yourself in need of a workout but without any of the things you think you need to get one, we got them to share the best workouts and circuits and exercises you can do anyway—no gear required.
The skin also serves as a release point for heat. (See “Why Does My Face Turn Red When I Exercise?” for more on that.) When you exercise, your muscles generate a lot of heat, which you have to give up to the environment so your body temperature doesn’t get too high, Hackney says. The heat in the muscle transfers to the blood, which shuttles it to the skin; it can then escape into the atmosphere.