2. The faux pas Performing your reps too quickly
The facts If you zoom through your repetitions when strength training, you'll be using momentum instead of muscle power. You won't get the same stimulus for muscle building, and you won't burn as many calories. You'll also be more susceptible to training injuries such as torn muscles or connective tissue.
The fix Take 6 seconds to perform each repetition: 2 seconds to lift the weight and 4 seconds to lower it. (Since you have gravity to help you lower the weight, you need to slow down even more on this phase in order to give your muscles a sufficient challenge.) Our experts agree that slowing down is the single most significant change you can make to get better results from strength training.
3. The faux pas Exercising too hard, too often
The facts If you don't rest enough between hard cardio or strength workouts, you'll stop making progress and may even lose some of the fitness you've gained. You're also likely to burn out on exercise.
The fix To keep your muscles fresh and your motivation high, alternate shorter, tougher cardio workouts (for instance, 20 minutes) with longer, easier days (40–60 minutes). Don't go all-out more than twice a week. Keep in mind that the more intensely you train, the more time your body needs to recover. It's a good idea to do a couple of tough workouts and take 1 day completely off each week. On the strength-training front, take at least 1 day off between sessions that work the same muscle group.