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Nowadays, most people don't have time for lengthy, grueling 2-hour workouts, be it with work and family demands or simply the search of free time. Well, what if there was a way to be in and out of the gym in less than 1 hour and still feel absolutely worked? What if you could combine your cardio and weights so that you wouldn't have to spend hours on either? Well, I'm going to let you in on a little secret ' it's called Circuit Training ' and it is the most effective and time efficient means of exercise for those looking to lose weight and tone.

CIRCUIT TRAINING 101

Circuit Training involves completing several resistance exercises in a continual sequence. For instance, a circuit may be comprised of 8 exercises (push-ups, plank, lunges, etc') with each one being performed for any length of time (30 sec, 45 sec, etc') or number of repetitions. Between each exercise is a rest period of a certain length. Note that circuits that have lower rest periods will be more challenging and provide more aerobic benefit. An example of a typical circuit is 8 exercises each 30 seconds in length with 30 seconds to recover between each. This is only one example of 1000s of possible circuit combinations. There are many factors involved in determining the effectiveness of a given circuit including: number and types of exercises, load, tempo, duration of work bout, duration of rest bout. Basically, the more intense you make the circuit, the more challenging, yet effective, it becomes.

AEROBIC BENEFITS

Studies have found that aerobic benefits related to circuit training are mainly determined by the duration of the exercise (work bout) and by the amount and type of rest given between exercises. For instance, a meta-analysis done on circuits showed that a 10-exercise circuit (using weights) using a 30 seconds for both work and recovery, performed 3 times per week over 8-12 weeks improved VO2max (measure of aerobic capacity) by 5%. Compare that to continuous running, cycling or rowing at around 75% of max heart rate for 20-30 minutes, three times a week for 8-12 weeks which boosts V02max by around 20%. Obviously, this 30s work: 30s rest protocol is not optimal for yielding staggering aerobic improvements. However, other studies have shown that by shortening the rest period to 15 seconds or jogging during a 30 second recovery bout improved VO2max by 12% and 18%, respectively.

Further, some research has even shown that Circuit Training can be just as effective at maintaining previous aerobic gains as following a strictly aerobic conditioning regime.

Incorporating more compound movements (several different muscle groups involved) into your circuits will make it more challenging for both your muscles and aerobic system. This is because as you use more muscle mass, more oxygen is required to supply the working muscles. As a result, you begin breather heavier and your heart rate increases to provide the muscles with the oxygen they need. This technique makes circuits much more challenging and effective. As an example, perform lunge walks with a shoulder press, instead of either one separately. Here is an example of a 7.5-minute aerobic based circuit:

1. Lunge Walks with Biceps Curls' 30 sec
2. Jogging on spot ' 1 min
3. Stability Ball Chest Press ' 30 sec
4. Jogging on spot ' 1 min
5. Plank ' 30 sec
6. Jogging on spot ' 1 min
7. Back Rows ' 30 sec
8. Jogging on spot ' 1 min
9. Squat Presses ' 30 sec
10. Jogging on spot ' 1 min

BODY COMPOSITION CHANGES

Circuit Training has been shown to decrease body fat by 3%. Research also shows that lean body mass is either maintained or increased alongside the decrease in body fat. This is a major benefit for those who want to get in better shape, lose weight, and tone. With traditional aerobic training, a decrease in relative fat mass leads to a decrease in total weight with little change in lean body mass. The resistance work involved in the circuits encourages muscle-mass development, and thus any fat loss is replaced equally by muscle gain. This makes it easier to maintain the lower body fat or reduce body fat even further because the increase in lean body mass pushes up basal metabolic rate and overall calorie expenditure.

It has also been estimated that calorie expenditure during a bout of circuit training is approximately 5 - 6 kcal per minute for women and 8 - 9 kcal per minute for men (this may vary depending on body weight). Thus, if a man were to perform 30 of circuit training he would burn upwards of 180 calories.

OTHER BENEFITS

Because of the duration of each exercise many people claim that strength may be compromised as a result of working at a lower percent of 1RM (maximum weight you can lift once). This is definitely true in most cases and thus, I would not recommend circuit training for those looking to improve strength. However, some studies have shown that circuit training increases muscular strength anywhere from 7% to 32%.1 Achieving such strength gains requires working at a much higher percent of 1RM (>80%) and thus the duration of the work bouts would need to be much lower (