You don't have to spend hours exercising if you want to lose weight or get stronger. Fitness instructor John Kersbergen says three to four 45-minute workouts a week is enough. If 45 minutes is more than you can devote at one time, break up your workouts, because it all adds up! Here are the best 20-minute workout videos you can follow along to — do two in a row or one in the morning and one at night. There's a great mix of quick and fun workouts including cardio, tabata, weights, barre, and dance, so you can do them all or pick and choose your favorites.