Interval cardio at home, no machines required.

Check out the latest Turbulence Training blog post if you're looking for ideas.

The basic protocol is, you pick a single total body exercise and go fast and furious for 30 seconds. Then you rest 30-60 seconds depending on your fitness level, and repeat for a total of 6 intervals. The recommended exercises are dumbbell or kettlebell swings, dumbbell squat to overhead press, and burpees (with or without the pushup).

Whatever you choose, be sure you're working at maximum effort--about a 9 on the perceived exertion scale, meaning you should feel extremely ready to stop after 30 seconds. If you feel like you could go longer, pick heavier weights or a harder exercise, or shorten up the rest period. Or, go longer :) Not every HIIT session has to involve maximal effort. In fact, not every HIIT session should involve maximal effort, IMHO. I personally think it's more effective to do true anaerobic interval training no more than twice a week; otherwise you put yourself at risk of overtraining. You can do HIIT more often than that, as long as you alternate maximum effort days with slightly less intense ones. And I do mean slightly. One to two minutes of 80-85 percent effort, followed by a recovery period of no more than a minute, would be my suggestion.