Metabolic Training: Do We Really Need Cardio?

by Dr Mike Bracko

Dr Bracko will be here at Fit Singapore to teach our HIIT Workshop on 24th September 2017)


There seems to be a general consensus in the fitness industry that cardio must be part of an exercise program for our clients. Even though we are training them with weight training, yoga, high or medium intensity interval training, and all other kinds of exercise, we still need for them to do cardio. Many clients want, or need, their cardio. Evidence of this is the cardio machines being packed at peak times at gyms. But when we look closely at the benefits of non-traditional exercise (yoga, martial arts, Tai Chi), weight training, and high and medium intensity interval training, we understand that all the benefits of cardio training can be realized with non-cardio exercise. This article will discuss the guidelines or recommendations that many professional organizations have for improving fitness and health as they relate to using cardio training. The discussion will then focus on what cardio exercise is as well at what metabolic training is. The benefits of weight training compared to cardio will be a primary focus as well as the benefits of high intensity interval training.

Learning Objectives:

1.Understand the guidelines of health and fitness associations for improving fitness and health and if they include non-traditional training instead of just cardio.

2.Be able to describe what cardio exercise is as well as metabolic training.

3.Describe the benefits of weight training when compared to cardio.

4.Understand the multiple benefits of high intensity and medium intensity interval training.



Many clients, and trainers, seem to think there is a dramatic need to incorporate cardiovascular training into either every training session or at least into an overall program. Watching people at gyms you can see that cardio training is popular because most cardio machines are being used during peak times. Based on the dramatic improvements in fitness that high intensity interval training (HIIT) research studies have found, the need for, or the feeling that a work-out or program is lacking without cardio training may be questioned.

There is no question of the benefits of cardio training, or long slow distance training. But with limited time of many clients, and perhaps the changing landscape of the business of personal training, it may be questioned if it is worth spending the time doing a long bout of cardio training. Many professional associations write their guidelines that cardio training is very important.


Guidelines for Health and Fitness

American College of Sports Medicine (ACSM) (Garber, et al., 2011), their guidance for prescribing exercise includes moderate-intensity cardio exercise for ≥30 min/day ≥5 days/week for a total of ≥150 min/week. Or vigorous-intensity cardio exercise for ≥20 min/day ≥3 days/week for total of ≥75 min/week. And finally, a combination of moderate- and vigorous-intensity exercises.

American Heart Association (AHA)( can-Heart-Association-Recommendations-for-Physical-Activity-in-Adults_UCM_307976_Article.jsp) recommends 150 min/week of moderate exercise or 75 min/week vigorous exercise (or combination of moderate and vigorous). The AHA suggests 30 minutes a day; five times a week is an easy goal to remember. And they talk about people experiencing benefits if they divide your time into 2 or 3 segments of 10 -15 minutes per day.

American Diabetes Association (ADA) ( suggests to aim for 30 minutes of moderate-to-vigorous intensity aerobic exercise at least 5 days a week or a total of 150 minutes per week. They also suggest to spread out the the activity over 3 days during the week and try not to go more than 2 days in a row without exercising. It is noted in their guidelines that moderate intensity means that a person is working hard enough to talk, but not sing, during the activity. Vigorous intensity means you cannot say more than a few words without pausing for a breath during the activity.

The U.S. Department of Health & Human Services ( might have the most practical suggestions for people to be active. They start with baseline activity – light-intensityactivities of daily life, such as standing, walking slowly, and lifting lightweight objects. But suggest that health-enhancing physical activity produces health benefits. They indicate that brisk walking, jumping rope, dancing, lifting weights, climbing on playground equipment at recess, and doing yoga all have health benefits. And one exceptional part of their guidelines is that they talk about how some people (such as postal carriers or carpenters on construction sites) may get enough physical activity on the job to meet the physical activity guidelines.

As such, it appears that many professional associations recommend mostly cardio training in an attempt to help people improve their health and fitness. It appears that many of these associations do not talk about HIIT or even medium intensity interval training as a way to improve fitness and health.


What is Cardio Exercise?

The question that is raised is what exactly is cardio exercise? In a practical sense it could be argued that any form of exercise is “cardio” because all forms of exercise place a demand on the cardiovascular system. But technically, the fitness industry usually describes cardio as exercise that increases the demand of oxygen to the muscles for a long period of time. The ACSM describes cardio as “exercise that uses large muscle groups and is done for 30 – 60 minutes.” Other descriptions include, long slow distance (LSD), an activity that raises your heart rate to a level where you’re working, but can still talk, or exercise that increases the demand of oxygen to the muscles. But, as mentioned above, all forms of exercise do what these descriptions indicate: for instance weight training, boot camps, yoga, Pilates, just to mention a few. The distinct difference is that cardio exercise is steady state exercise and is performed for a relatively long period of time.


Metabolic Training

Although there is no specific definition of metabolic training, we can start with what metabolism is and move forward from there.

According to Timi Gustafuson, R.D., metabolism is a complex network of hormones and enzymes that convert food into fuel and affect how efficiently we burn the fuel ( Yet others have different definitions of metabolism; “exercises that improve or enhance the body’s energy systems” (, “conditioning muscles to better use what’s being delivered to them by improving the efficiency of the different metabolic pathways” (, and “exercise that utilizes science of endocrinology and performance training to tax body’s major energy systems . . . maximize use of stored adipose tissue as a fuel source, during and after exercise” (

There are five different metabolisms that our body experiences: 1) sleeping, 2) resting/sedentary work, 3) active work, 4) exercise, and 5) post-exercise. With specific reference to exercising metabolism, McArdle, Katch, and Katch (2001) indicate that short term physical activity stimulates a sharp rise in growth hormone and increases free fatty acid mobilization. Fat and carbohydrate are used for energy to produce muscle contraction simultaneously as it relates to exercise intensity. Kenny, Wilmore and Costill (2011) indicate that the approximate energy use during continuous exercise is 50% carbohydrate and fat at ten minutes of exercise, 70% carbohydrate and 30% fat at 30 minutes of exercise, 40% carbohydrate and 40% fat at 60 minutes of exercise, and 20% carbohydrate and 80% fat at 120 minutes of exercise.

Many people do not have a good understanding of how fat is used by the body to produce energy for muscle contraction. Some people have the misunderstanding that the body either uses fat or carbohydrate for energy during exercise depending on how intense the exercise is. This is not the case at all, and Spencer & Gastin (2001) have perhaps the most elegant description of how the energy systems are used during exercise, “Energy for exercise does not simply result from activation of a series of energy systems that ‘switch on’ and ‘switch off’ but rather from a smooth blending, with considerable overlap of one mode of energy transfer to another.” As such, we cannot train the body to use fat as fuel. The fat in fat cells is released into the blood at the onset of exercise. Fat that is released into the blood are called free fatty acids, and they bind with a blood protein called albumin. Albumin carries the fat to the muscle cell and it is used to produce adenosine triphosphate (ATP). Low intensity activities such as walking strongly stimulate fat use from peripheral areas, while muscle fat contributes little to total energy. At low intensities of exercise carbohydrate needs are met with blood sugar and little glycogen (carbohydrate stored in the muscle cell) is used. Fat use is highest during moderately intense exercise (65% of VO2 max) free fatty acids and muscle fat contributing equally. During high-intensity exercise (85% of VO2 max), the rate of total fat use falls, mainly because the appearance of fatty acids into blood is suppressed Kenny, Wilmore and Costill (2011).

When we think of metabolic training, we can say we are training our body to increase our metabolism. In most cases, trainers refer to metabolic training as either HIIT or anaerobic training. Generally speaking, metabolic training is recognized as high intensity training of any kind with little rest or structured rest between sets of high intensity work. One of the benefits of metabolic training is the “after burn” or excess post exercise oxygen consumption (EPOC). Excess post exercise oxygen consumption can be defined as ‘disequilibrium’s’ in physiologic function, operating to keep recovery metabolism elevated (McKardle, Katch, & Katch, 2001). Post exercise metabolism is similar to a blender after mixing a smoothie. After the blender has mixed the smoothie, all the ingredients tend to settle in the mixer. This is similar to what happens to many body functions after metabolic training, they have to get settled back to their resting metabolism. And the increased calorie burn is caused by the body working “over-time”to get body functions back to resting metabolism. Some of the body functions that need to get back to normal include: resynthesize lactate to glycogen, 10% of recovery is to reload hemoglobin with oxygen, start of tissue repair, and the redistribution of calcium, potassium, and sodium in the muscle cell. Excess post exercise oxygen consumption is dependent on the intensity and duration of exercise, as well as training status and gender because females have less muscle mass. Elevated post exercise metabolism can last anywhere between 90 minutes to 24 hours, depending on the factors mentioned above.


What Kind of Fitness Do Our Clients Want?

The type of exercise our clients engage in depends on what type of fitness they want to achieve. There are several levels, or types, of fitness, including: activities of daily living, health related fitness, physical fitness, recreational athlete, and elite athlete. And we come back to the question as it relates to the different types of fitness, do our clients need cardio. If we are strictly interested in how many calories our clients burn in a work-out, the following my help us answer the question. According to Kenny, Wilmore, and Costill (2011) the following exercises burn the corresponding number of calories:

1.Weight Training, vigorous = 373 kcals/60 minutes

2.Vinyasa Yoga = 535 kcals/60 minutes

3.Calisthenics, vigorous = 494 kcals/60 minutes

4.Judo, martial arts = 616 kcals/60 minutes

5.Rock climbing = 672 kcals/60 minutes

6.Boxing, punching bag = 364 kcals/60 minutes

7.Aerobics, high impact = 429 kcals/60 minutes

However, in order to get benefit from physical activity it does not have to be actual exercise rather, movement. Brudnak, et al., (2002) found that hard martial arts benefited the elderly. Takeshima, Rogers, Rogers, et al., (2007) found that Tai Chi and yoga improved functional fitness for older adults. Seo, et al., (2012) indicate that yoga can be an uncomplicated therapy for obesity in adolescent boys. Fourteen year old obese boys did yoga three times per week at 40 – 60% of heart rate reserve. After yoga training, body weight, body mass index, fat mass, and body fat percentage were significantly decreased, and fat-free mass and basal metabolic rate were significantly increased compared to baseline values. Based on these findings, it brings the question of do we need cardio into a different perspective.


Weight Training is Medicine

Artero, et al., (2012) found the specifically muscle strength from weight training had a protective effect on all-cause and cancer mortality in healthy middle-aged men, men with hypertension, and patients with heart disease. They also found that muscle fitness was inversely associated with weight and fat gains, risk of hypertension, and prevalence of the metabolic syndrome. They concluded by saying high levels of muscle fitness seems to counteract the adverse cardiovascular profile of overweight and obese individuals. This is significant research because many people only think that cardiovascular exercise can have these types of effects on heart disease patients and obese individuals.

Westcott (2012) indicates that inactive adult’s experience a three to eight percent loss muscle mass per decade, a decrease in resting metabolic rate, & increased fat accumulation. However, he has found that ten weeks of resistance training increased lean weight by three pounds, increased resting metabolic rate by seven percent, and reduce fat weight by four pounds. Moreover, the benefits of resistance training include improved physical performance, movement control, walking speed, functional independence, cognitive abilities, and self-esteem. resistance training can promote bone development, with studies showing a one to three percent increase in bone mineral density.

McGuigan, et al., (2009) did an eight week resistance training program (three days per week) with children who were overweight or obese. There were 26 girls and 22 boys, with a mean age of 9.7 years. After the training, they found a decrease in absolute percent body fat of 2.6% and significant increase in lean body mass of 5.3%. There were increases in one repetition maximum squat (74%), number of push-ups (85%), countermovement jump height (8%), static jump height (4%), and power (16%). Based on these exciting findings it is hard to argue that cardio exercise would have the same effect.

Westcott, (2012) compared the benefits of weight training to cardio exercise and reported the following comparisons. For fat reduction, cardio training uses more calories during the exercise, but there is less EPOC. As such, calorie for calorie cardio exercise has a slight advantage, during the exercise. Generally speaking, running or cycling can use 10 to 12 calories per minute, whereas weight training uses 8 to 10 calories per minute. However, when taking into consideration EPOC, weight training has the advantage because in a 60 minute weight training work-out, there is an additional 25% of calories burned after the training is done. Westcott (2012) indicates that for every three pounds of muscle a human can burn an extra 120 calories per day.

Westcott (2012) also looked at body changes with weight training compared to cardio and indicated that body image can increase immediately after a weight training work-out. . . blood engorged muscles which gives the muscles and immediate pump. And that people feel confident because they just lifted some major poundage. Finally, Westcott (2012) indicates that the repetitive nature of puts clients at a higher risk of injury with cardio. Functional strength training teaches the brain to allow muscle contractions that are quick enough to prevent or minimize injuries.


High Intensity Interval Training

One of the strongest arguments against performing long slow distance cardio is that high intensity interval training (HIIT) has been found to provide almost identical benefits, if not more, than cardio training. This raises the question that if a client can get the same benefits with HIIT in dramatically less time, why not uses it and focus on other forms of training. Or, is it possible to restructure training time and try to get more clients in an hour?

Many studies have been done showing how many calories HIIT can burn, the effects on fat reduction, and the cardiovascular benefits. Olson, (2013), had subjects perform a four minute Tabata (20 seconds maximum work, with 10 seconds of passive rest repeated four minutes) routine of jump squats. She found that the subjects used 13.5 calories per minute for a total of 54 calories during the Tabata routine. She also calculated the subjects EPOC and found that they burned 81 calories for 30 minutes after the Tabata training for a total number of calories burned of 135 from four minutes of exercise.

Whyte, Gill, Cathcart (2010) used ten overweight/obese sedentary men as subjects and had them perform two weeks, six sessions, of four to six, 30 second Wingate sprints with 4.5 minutes of recovery. The results of the training showed that VO2max and Wingate power increased, insulin sensitivity and resting fat oxidation rate were higher (24 hours post-work-out), systolic blood pressure and resting carbohydrate oxidation were lower (24 hours post-work-out), and waist and hip circumferences decrease. These are remarkable results considering the training was only six sessions. Again, this is perhaps an argument for HIIT training versus cardio training.

Tremblay, Simoneau, and Bouchard (1994) compared aerobic exercise & medium intensity interval training (MIIT) on fat loss and muscle metabolism. They had two groups, the aerobic training group did 20 weeks of endurance training on a cycle ergometer, four then five times per week, for 30 to 45 minutes, at an intensity of 60% – 85% of heart rate reserve. The MIIT group did 25 30-minute aerobic training sessions at 70% of maximal heart rate reserve plus 19 short interval sessions (10 – 15/15 – 30 seconds) and 16 long intervals (4 – 5/60 – 90 seconds). The intensity of the training was 60% – 70% of the maximal work output in 10 seconds. The recovery was when the heart rate got down to 120-130 beats per minute. The results indicate that the total calories burned for the endurance group was 28,757.04 calories and the MIIT group burned 13,829.17 calories for a difference of 14,927.87. However, one of the remarkable findings of the study was that the MIIT group decreased their sum of six skinfolds nine-fold less than the endurance group. In addition, the MIIT group had significant increase in enzymes promoting fat being used as energy for muscle contraction.

Hazell, et al., (2014) had fifteen recreationally active women (22.9 years old) perform six weeks of sprint interval training. The subjects did 4 to 6, 30 sec maximal sprints on treadmill with four minutes of rest between sprints three times per week. The results show that the sprint interval training decreased body fat by 8% (measured in a BOD POD) and waist circumference by 3.5%. There were increases in fat-free mass of 1.3%, maximal oxygen consumption of 8.7%, and peak running speed of 4.8%. The authors conclude that their training protocol is a time-efficient mode of training for decreasing body fat; increasing aerobic capacity, peak running speed, and increasing fat-free mass in healthy young women.



In conclusion, even though many professional associations recommend cardio for improved fitness and health, the benefits of other forms of exercise can be as good or better. Not to suggest that cardio training does not have its benefits rather, it is to suggest that other forms of exercise are as good, or better for our clients. For instance non-traditional exercise such as yoga can have dramatic effects on weight loss. Tai Chi and martial arts improved the functional capacity of older adults. Weight training has remarkable benefits for calorie burn during and after the work-out. It has been used for weight loss in children and adults. Based on the research of Baquet et al. (2010) is makes sense that weight training is good for kids because they do not like LSD training primarily because they find it boring. Body changes are more intense with the muscles getting an immediate pump from weight training. Weight training also has a good effect on reducing injuries compared to repetitive cardio training. From 1994 with Tremblay, Simoneau, and Bouchard to 2014 with Hazell, HIIT and MIIT has been found to produce very good results for burning calories during and after exercise, improved V02, fat loss, reducing waist and hip circumferences, reducing systolic blood pressure, and increasing fat-free mass. Bill Kraemer, former Editor-In-Chief of the Journal of Strength and

Conditioning Research is quoted as saying “While the practice of strength and conditioning will always rely on the art and creativity of the professional to implement the science, a factual basis for practice is needed similar to the process a physician uses in patient treatment decisions.” As such, trainers need to continually be creative with all the new information that is being put out to us.