The terms "circuit training" and "interval training" are often used interchangeably, but they are not the same workouts. The two workout types use different exercises, require different energy systems and promote different results. Both are efficient, time-effective workouts, however, that you can easily add into your weekly routine to boost your fitness benefits.
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Circuit training is a resistance-training workout. You choose nine to 12 exercises and rotate through stations for a pre-determined length of time. For example, perform a chest press, lat pulldown, shoulder press, bicep curl, tricep extension, squat, lunge, calf raise and abdominal crunch for 30 to 45 seconds each. Then, you repeat the circuit for the duration of your workout. In contrast, interval training is an aerobic-based workout. You choose your aerobic exercise and add intervals of increased speed or resistance. For example, during a brisk walk, add a one- to two-minute sprint, then return to your brisk walking for an equal amount of time.
You choose the types of resistance exercises to include in your circuit training workouts. These can be free-weight, weight-machine, kettlebell, medicine ball or bodyweight based exercises. The exercises challenge your muscles to improve your strength and provide workout variety. You also choose the types of cardiovascular exercises to include in your interval training workouts, but you only do one type of exercise for each workout. Select aerobic exercises such as walking, swimming, cycling, stair climbing, jogging and skating to increase your heart and breathing rates and improve your endurance.
Circuit training primarily uses strength-training exercises. Some circuit variations contain aerobic stations in between the strength exercises. A traditional circuit workout calls for 15 to 45 seconds of each resistance exercise. When you perform an exercise for less than two minutes, your body uses your anaerobic energy system, which converts glucose into fuel. Interval training uses cardiovascular exercises of a sustained duration. An exercise performed for longer than two minutes uses your aerobic energy system, which converts fat into fuel. The short, bursts of intensity intervals switch to the anaerobic energy system.
You can burn fat with both circuit and and interval training workouts; circuit training also increases your muscle mass. Interval training improves your endurance, which means your body becomes more efficient at converting both fat and glucose into energy, so you are able to workout for longer durations without as much effort. Both workouts help reduce overuse injuries as you constantly vary your workouts.