n. Cardio Circuit Training for Weight Loss

Article Taken from PT on the Net

Written by Paul Robbins
Date Released : 10 Oct 2011

The fitness industry is rife with misleading information regarding the benefits of cardiovascular exercise for weight loss, and many “sure thing” cardio programs for weight loss have come and gone. Left in the wake of these questionable programs are frustrated, overweight folks who never saw the promised fat loss and energy gains, despite working as hard as they could (or so they thought).

As fitness professionals, it can be difficult to sift through fact and fiction to come up with a cardio-based training plan that really works for these clients. Let’s first address some common mistakes made in cardio training programs for weight loss, then discuss how to deliver and progress a program that will effectively promote weight loss using interval-based cardio circuits.

Mistake #1: Focusing on Low Intensity, Long Duration Cardio Workouts
One common misconception is that body fat reduction can only result from extended periods of time on a piece of cardio equipment or in a group exercise class. This is based on a theory known as the “fat burning zone,” which advocates exercising for longer periods of time, but at a low intensity. Although fat may be utilized as a fuel in this zone, a low number of calories will be burned and metabolism will not increase, which is the key to burning fat.

Long term body fat reduction takes place when there is more energy being burned than consumed. The biggest benefit from a cardio workout should be the body’s ability to burn calories after the cardio workout and throughout the day. This is known as EPOC (excess post-exercise oxygen consumption), the state in which the body’s metabolism is elevated after exercise. This means that the body is burning more calories after exercise than before the exercise was initiated. Think of EPOC as a caloric afterburner that is caused by exercise (much like a car engine stays warm for a period of time after it has been driven). After exercise, the body must use increased amounts of oxygen to replenish energy supplies, lower tissue temperature, and return the body to a resting state.

There is a place for low intensity training. It should be used to build a work capacity for beginners and to provide a recovery period for more advanced clients. Low intensity cardio does not result in weight loss, but can increase the energy deficit of the body, creating the right physiological conditions to promote weight loss. To really burn calories, however, you must introduce some higher intensity training into your client’s cardio program.

Mistake #2: Basing Training Solely on Heart Rate Zones
Another misconception of cardio training for fat loss is that the exerciser must stay within specific heart rate zones. The formulas used to create these zones – such as the most basic formula, 220 minus age – are largely inaccurate because, as research has shown, they are unable to correctly estimate the energy systems being used (Robergs & Landwehr, 2002). In addition, energy systems are not based on heart rate, but rather on the time and intensity that the exercise is being performed. Using heart rate alone to design a cardio program will limit success.

The more important measure is power. In most cases, power is gauged during cardiovascular training in the form of watts. More watts (power) generated means more work performed, and when more work is performed, more calories are burned. Another limitation of heart rate training alone is that the client’s heart rate may be increasing toward the end of the workout while their watts could be decreasing due to fatigue. If calories burned are being measured by monitoring heart rate alone, it will indicate that the client is burning more calories than he or she actually is.

An Effective Cardio Weight Loss Training Technique

So, what really works?

Many popular programs that promote very high intensity workouts have shown great results, at least in the short term. For example, studies of different programs on the market found that very high intensity programs like Tabata (Tabata et al., 1996) and High Intensity Interval Training (HIIT) (Tabata et al., 1996; Gibala et al., 2006) resulted in significant weight loss for participants. The fitness franchise Curves has also had success using basic intervals programming to achieve weight loss (Kerksick, 2007). Chart 1 below shows how high intensity intervals can help promote weight loss by burning more calories.

Aerobic exercise levels
Chart 1: The yellow line represents a low intensity workout, which produces very low in calorie expenditure.
The green line represents what happens in a lot of group exercise classes — more calories are burned than in the low intensity workout, but this often still results in plateauing for most clients.
The red line shows interval training, which will take your clients to a higher intensity level to promote higher caloric expenditure during and, even more important, after the workout.

“Circuit training” has been a buzz phrase in fitness in recent years, and is a great way to accomplish a lot of work in a short period of time and promote caloric burn both during and after the workout. Because the intensity of the workout greatly increases the odds of injury or burnout, however, trainers must consistently monitor the client’s power expenditure and heart rate throughout the session. This enables the trainer to gauge improvement and safely progress the client’s program while keeping track of signs of overtraining. Using a heart rate monitor is the most effective way to monitor the heart rate and there are new strapless monitors that not only show continuous heart rate, but also have interval programs built into them.

Most circuit training programs slowly introduce circuit with intervals, in an effort to avoid the plateaus that often resulted from training in the “fat burning zone.” To do this, 30-second high intensity work intervals are combined with 30 seconds of rest or recovery. For a beginner, this recovery may be complete rest, while more advanced exercisers have an active recovery, such as walking or movement exercises like dynamic stretching or light plyometrics. Because the goal is to maintain the intensity throughout the interval, 30 seconds of high intensity exercise is sufficient. Longer intervals often result in compromised form and technique, and clients are unable to maintain the resistance necessary to achieve the desired results, such as an increase in EPOC. Thirty-second intervals make it easy for clients to stay focused and to put in 100% effort, making the workouts move very quickly.

In order to determine how many intervals should make up a circuit, the creators of high intensity programs developed the “five minutes of fun” concept. This five-minute block of intense exercise is extremely effective because clients can maintain power, keep perfect form and focus, and push themselves to their physical limits while seeing the end is near. At the same time, trainers and coaches are able to effectively measure the client’s power expenditure during this relatively short period. In the studies noted previously, 10-minute circuits showed a significant drop in client performance in minutes 6 through 8, and circuits shorter than 3 minutes did not allow for maximum effort.

Implementing “Five Minutes of Fun” Circuits

Beginning weight loss clients that have been walking for 30 minutes at a steady pace are ready to add some circuits to their workout once or twice a week. This is the perfect time to implement the five-minute 30/30 interval training format. After a light warm-up, have them begin walking at their normal pace. Their first 30-second work, or high intensity interval, can be to walk quickly for 30 seconds, then resume their warm-up pace for 30 seconds. This would be repeated five times, finishing with a slow-paced cool-down. They can repeat the “five minutes of fun” any time during the workout. The more circuits they do, the more calories they will burn. The faster walk is simply an increase in watts (watts can be measured using speed, distance and bodyweight). For beginners, it isn’t necessary to measure the watts — the goal is to just get clients out of their comfort zone. Heart rate can be used for these clients, but not heart rate zones. More important for beginners is to monitor how fast their heart rate drops.

Using the “five minutes of fun” as a guide, improvements in cardio fitness levels can be measured. The goal is to see how fast the heart rate drops from the top heart rate recorded during the 30 second fast pace, to the recovery heart rate in the 30 second rest or recovery pace. The average number of beats the heart rate drops over the five rest/recovery periods provides you with a very simple fitness score. If a client’s heart rate drops an average of 10 beats over the five minutes, that is his or her fitness score. It is not necessary to look at norms; you will only use this number (fitness score) to gauge the client’s improvement over time. This client may aim to have their average heart rate drop by 11 beats in the next month. A heart rate that drops faster indicates improved cardiovascular fitness. Additionally, with the faster walk intervals (or perhaps a slight incline on the treadmill), more calories are burned. This simple 30/30 interval training program provides the two basic benefits of cardio training: an increase in cardio fitness (faster heart rate recovery) and more calories burned (more work done).

This same concept can be applied to advanced clients and those who have reached either a cardio fitness or weight loss plateau. Now they can be taken to the next level once or twice a week by adding the 30/30 program to their favorite cardio workout. With this group, begin to measure the power output so they can progress. On a bike, simply record the watts/RPMs during the 30 seconds of high intensity (max effort) work. Ideally, all five intervals are performed at the same watts/RPMs. Make sure clients do not start too fast and have to reduce intensity before the end of the five minutes. If clients must reduce intensity, fewer calories are burned and their form has usually broken down. This can result in an injury if done on a consistent basis. With cardio, the work is recorded so you can continue to push clients by adding more work (watts/RPMs) over time. This can be done running outside as well and timing a run over a set distance. Over time, increase the distance they must cover in the 30 seconds, which represents an increase in power.

For additional weight loss, vary the equipment. To promote the use of additional muscle groups, use climbers, rowers, ellipticals (not all brands are safe to do sprints on, so check the biomechanics of the equipment first), and equipment where power can be generated quickly, such as indoor cycles, Versaclimbers or Woodway Curve treadmills. Track the power and use heart rate as a guide. Determine if a client can safety push the heart rate up little higher over time, but, more importantly, track the heart rate recovery.

There are several additional ways to progress clients using interval training. Continue to add watts to the intervals while monitoring the client’s form, and /or reduce the time between the “five minutes of fun.” Initially, a five-minute recovery period will promote total body recovery, enabling the client to perform the next five-minute circuit at the same level as the last one. Over time, this recovery period can be reduced to two to three minutes. If the client is unable to perform subsequent series at the same intensity, the two to three minute recovery period is too short. Another progression is to change the 30 seconds of rest after each 30 seconds of work. They could start as complete rest periods, then progess to active walking, balance exercises or movement exercises. Again, if the intensity during the work intervals begins to drop off, the 30-second active recoveries are too hard and the client may need to return to complete rest during these recovery intervals.

The 30/30 interval training program will safely aid in both cardio fitness improvement and the body’s ability to burn more calories during workouts, while increasing metabolism to burn calories throughout the day. It is important to note that this type of training should be done only once or twice a week. It is a great supplement to group exercise or steady-state training, and weight training can be added for a total body workout if closely monitored. If your client is exercising every day, mix in some lower intensity days (returning to the old “fat burning zone”) to help promote recovery and to prevent overtraining. For the most part, clients can do the high intensity workout once or twice a week year-round if they mix in lighter workout days the rest of the week, with an unload week every six weeks. This training variety avoids hitting a plateau or burning out.

Sample Training Formats for Weight Loss Clients

Below are some sample breakdowns of formats you can use to develop programs for your clients, depending on their training frequency.

3x per week

Monday Wednesday Friday
30/30 group exercise or steady-state 30/30

5x per week

Monday Tuesday Wednesday Thursday Friday
30/30 low intensity
group exercise
or steady-state
30/30 low intensity

6x per week

Monday Tuesday Wednesday Thursday Friday Saturday
group exercise
or steady-state
30/30 low intensity
group exercise
or steady-state
30/30 low intensity


Gibala, M.J., Little, J.P., van Essen, M., Wilkin, G.P. , Burgomaster, K.A., Safdar, A., Raha, S. & Tarnopolsky, M.A. (2006 Sept). Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance. Journal of Physiology 575(3): 901–911. Retrieved from http://jp.physoc.org/cgi/content/short/575/3/901.

Kerksick, C., Roberts, M., Taylor, L., Moulton, C., Rasmussen, C. & Kreider, R. (2007). Impact of Increased Energy Intake after Acute Hypo-Energetic Dieting on Markers of Energy Balance, Satiety and Fuel Utilization in Obese Females. FASEB Journal 21: 681.1

Robergs, R.A. & Landwehr, R. (2002 May). The Surprising History of the “HRmax=220-age” Equation. Journal of Exercise Physiology 5(2).

Tabata, I., Nishimura, K., Kouzaki, M., et al. (1996). Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and VO2max. Medicine & Science in Sports & Exercise 28(10): 1327–30.

2 thoughts on “n. Cardio Circuit Training for Weight Loss

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