Getting Lean: Why Your Current Cardio is on the Wrong Path

fit girl with kettle bell
Getting Lean: Why Your Current Cardio is on the Wrong Path
by: Taylor Simon

There are two priorities for those of us who dedicate a significant amount of our lives to the gym. The first is how to increase the amount of muscle we can make our bodies grow and the second is finding the best way to lose the body fat (BF) that hides it.

The difficulty that many have experienced is how to reduce their BF levels while preserving the lean muscle tissue they have laboured for so long to obtain. At one end of the spectrum are those that must dedicate themselves to achieving less than 10% body fat in order to enter competitions judged on visible muscularity. From bodybuilding to figure competitions, to modeling searches, there is a large population that is endeavoring to achieve just this goal. The opposing end of the spectrum is the larger proportion of the fitness population, who are those that simply want to drop body fat to see the six-pack, feel good, and earn some bragging rights. Those who must drop to very low fat levels have learned the best techniques and practices on how to do this and we can incorporate their practices into our own programs.

Many believe that the best way to decrease BF levels to competition level is to exercise at low intensity for 45-60 minutes once or twice a day pre-competition. Traditionally this approach began when we developed the knowledge of how the body uses energy to fuel long duration activity (we call it cardio). However, while the knowledge is sound, the resulting ideas of reducing BF are not as effective as it is believed.

The question is: what is the best way to preserve lean tissue, while stripping body fat? This is where the shades of grey have long been confusing the correct answer. The traditional approach for competitive figure and bodybuilding athletes is to increase cardio duration as early as 12 weeks pre-competition. The belief is that maintaining low intensity cardio activity at around 60% of max heart rate for 1 hour 6-10 times weekly is the best way to burn body fat, while preserving muscle tissue.

Is this, however, the best approach to cutting BF levels? First we need to understand the basic physiological processes that occur during exercise. Let us quickly review for anyone that is not familiar with these. For those of you who are familiar with physiology, this discussion is based on cardiovascular exercise in relation to BF reduction, as such; we will skip discussions of the creatine/phosphate system, as it is not relevant to our purpose.

The first and preferred energy source for your body during prolonged exercise is glycogen. This is simply sugar that your body converts carbohydrate into in order to fuel most processes in the body. You get glycogen from three places, stored in the liver, stored in muscle tissue, or from ingested carbohydrate.

Your next energy source to sustain activity is body fat. At a very useful 9 calories per gram, your BF stores represent the most efficient energy storage system you have. Your body knows that and works to ensure that a reserve supply is always present (12-18% for men and 18-22% for women is healthy). So this source of fuel is used once you have fully utilized the other energy systems.

The intensity of exercise is also a primary determinant for where the body uses energy. At lower exercise intensities (50-65% of max heart rate) the body’s energy use can be as much as 55-65% straight from BF storage, with the rest coming from glycogen storage, or if that is not available, catabolic muscle tissue breakdown. When exercise intensities increase to 75% to 90% of max heart rate, the fat utilization decreases and glycogen usage increases, with BF use dropping as low as 35-45% of overall energy expenditure.

Knowing that once muscle glycogen stores have been exhausted the body will catabolize (break down) muscle tissue to make more glycogen, a high intensity long duration exercise session seems like a poor choice for reducing BF levels. Most people will exhaust glycogen levels within 20 to 30 minutes working at a higher intensity. This means that after that time they begin to sacrifice hard earned muscle in order to complete the activity.

At lower exercise intensities the body is more likely to increase BF utilization, and hence, not go to muscle catabolism for meeting energy needs. This in effect means that at 65% of max heart rate your body uses significantly more BF for energy then stored glycogen and is less likely to begin eating muscle.

Armed with this knowledge the world of bodybuilding and fitness figure modeling has adopted a less than efficient system of obtaining very low BF levels. If long duration and low intensity workouts are not the best way to decrease BF, then what is? Especially if high intensity exercise leads to muscle breakdown!


Let’s do some math. We will use a 180 pound, male around 30 years of age as our example. If you are older, younger, heavier, lighter, or a different sex, than the base metabolic rates and calories used numbers will be a little bit different, but the principles will be the same.

So our case study wants to burn off body fat and keep muscle. So he decides to incorporate some cardio into his program. To preserve muscle he is going to stay at 60% of his max heart rate and do an hour long session on the treadmill.

Treadmill, 60 minutes @ 4mph:

  • Overall calories burned = 340
  • 60% calories from BF = 204
  • 40% calories from glycogen and muscle catabolism

Now let us say that our guy decides that he hates watching Oprah for an hour 5 times a week and wants to shorten his time on the treadmill. He ups his intensity to 80% of his max heart rate, which is not sustainable for a solid hour, so he is going to do a half hour session. This means that with commercials Oprah viewing is limited to a mere 20 minutes.

Treadmill, 30 minutes @ 6.5mph:

  • Overall calories burned = 450
  • 40% calories from BF = 180
  • 60% calories from glycogen and muscle catabolism

Well you might say at this point, more fat burned during the lower intensity session it is a better way to decrease body fat. This is the reason that many have decided to use the less effective system. There are other variables that we need to consider with this example.

  1. There was only a total of 24 calories less BF burned with the high intensity set, that’s only 3 dietary grams of fat.
  2. Don’t ignore the fact that the high intensity program is HALF AS LONG, only 30 min.
  3. While the amount of non-fat calories is higher, with the shorter duration, the majority of those calories will come from stored muscle and liver glycogen, not muscle catabolism. It is at high intensities longer then the 30 minute mark that the muscle catabolism becomes an issue, and then mostly if the right nutrition is not in place.
  4. The cardiovascular system would have to work at a much higher level during the shorter and higher intensity workout leading to more health benefits for the heart and lungs than the low intensity program provides.
  5. He couldn’t even pay attention to Oprah because he was working too hard.

There are other important aspects that need to be recognized as well. Intense exercise has been shown to increase metabolic rate much longer then low intensity exercise and the positive hormone response from intense exercise.

We will use the conservative estimates for our purposes. Exercise 70% or higher of maximum intensity has been shown to increase metabolic rate from 5-19% for up to 38 hours after the cessation of exercise (‘Impact of energy intake and exercise on resting metabolic rate’, Mole et al, Sports Medicine, vol 10, pp 72-87). Exercise below 70% does not have the same effect.

If we use our example above and say he experiences a 10% increase in base metabolic rate for 12 hours he will create an additional calorie deficit of 157 calories, based on a BMR of 3140 calories. This is in addition to the calories utilized during the session. If the extra calories are just over 100 per session we could drop a full cardio session from the 5 times a week schedule and burn almost the same number of overall calories over the course of the entire week. It is important that these calories do not become catabolized muscle tissue. The hormonal benefit from higher intensity exercise becomes important when we consider this.

Most people dedicated to bodybuilding and figure modeling are aware of a few important hormones. Testosterone, growth hormone (GH), cortisol, and insulin are the most important to your day to day fitness and fat loss programs. Testosterone and growth hormone are considered to be anabolic, in that they are muscle building, while cortisol is a muscle wasting hormone. Insulin is a good and bad hormone as it both helps to preserve muscle and keep glycogen energy stores topped up, as well as move excess calories into fat storage.

It has been well documented that more intense activity will actually increase the level of GH and testosterone in the body. So by increasing the intensity of cardio sessions it is possible to naturally increase the levels of these hormones in the body, helping to create a more anabolic state for the body. The longer the duration of your exercise session the higher the cortisol levels tend to become without the corresponding increase in anabolic hormones (note the difference between Olympic sprinters and Olympic marathon runners). If cortisol levels become too high for too long your body will break down muscle fibres, which is why we all work so hard to avoid overtraining.


Insulin can be you best friend. Insulin’s job is to shuttle glycogen back into the liver and your muscles after you have depleted those stores. Higher intensity exercise will burn more stored glycogen than low intensity, which was demonstrated above with our example, creating a need for glycogen replenishment. What does this have to do with the cardio sessions and fat loss? Shorter, higher intensity sessions will deplete your glycogen stores more than long term low intensity sessions, creating a need to replenish those storage areas. So when you eat your post-exercise carb meals, the insulin spike that is caused is most likely going to be taking all of those carbs and sticking them straight into your muscles and liver where they are need, instead of turning them into BF stores.

With the host of benefits from increasing cardio intensity above 75% of maximal heart rate there must be drawbacks, after all, if something sounds too good to be true, it usually is. There are things to think about before changing your program.

If you have a heart condition or blood pressure problems then elevating the heart rate too high can be potentially dangerous. If you fall into this category (including if you are on beta blockers) checking with your physician is a necessity. Diabetics also need to be conscious of the hormonal response from vigorous exercise, as rapid shifts in insulin levels is obviously un-desirable.

Oh yeah, and it hurts. You wont be able to read, or pay attention to what Oprah is talking about (if that’s your thing and it was pretty exciting when Tom Cruise jumped on the couch), and making conversation with the hottie next to you will be out of the question.

There are two questions you may now be asking yourself. How do you know when you are at the appropriate intensity and what are the best means of achieving these results in relation to decreasing BF levels while preserving lean tissue for competitions or just for lowering BF.

You don’t need to go out and buy the latest most accurate heart rate monitor on the market. As much as we all do the math and figure out percentages and calories and time and all of that, there are much more simple and just as effective strategies. The perceived exertion scale is an easy method.

If you are doing a cardio session and it would be possible to have a conversation with someone, not easy, but possible, that is roughly around the bottom end of your ‘target heart rate zone’. I know this from testing it on clients for the last 4 years. Is it exact? No. Is it the same for everyone? No. But it is a good general guide, which is what we are looking for. So what are you looking for to get at 75% or higher?

You need to go to the point that breathing rate significantly elevates and if someone try’s to talk to you that should be about the last thing you want to do (yes even if it’s the hottie). You should be out of breath and continuing that intensity for another 5 minutes should seem like an eternity, and you may even question your ability to do it for another 5 minutes. That’s around the 75% level.

How then, do you get your 30 minutes? The answer is to increase the intensity of the session. Yes you have all heard of interval cardio training. Why? Because it takes you to the point where all of the benefits we have been talking about take effect. It is relatively easy to create an interval program. Use your perceived exertion scale. 5 Minutes to get warmed up and the blood flowing, then go 1 minute at your bottom end zone. Then spend 1 minute at your 75% or more zone, then back for another minute at the previous level. Then repeat that 5-10 times and finish with a 5 minute cool down. I promise that if you do this with the right intensity you will kick your own ass harder in 20 minutes then you ever did in an hour.

This also allows you to get rid of some of the boredom factor cardio sessions can lend themselves to. It is easier to make every session different, try 30 seconds high, 30 seconds low. Or try a pyramid session, 1 min hard, 1 min low, 45 seconds hard, 45 seconds low, 30 and 30, 15 and 15, etc….the variety is endless. What many also forget is that your body will reach a set point with cardio. If you do the same hour long workout 5 times a week for 6 months, you will adapt and not get the benefits you are working for. You have seen them, the people on the treadmill or the elliptical who have been there since you joined the gym and still look exactly the same, maybe even the same workout clothes.


Here is where I will give you something new. This style of program is easiest to perform on the treadmill and stationary bike. Both of these are great options and you should incorporate them. Alright, here comes the long forgotten and most beneficial cardio options available to you (not in order of importance).

  • The Stair Mill. Not the step machine, the machine where the stairs just keep going around and around in an endless cycle. Do 15 minutes on that with the above program and let me know how you feel.
  • The Rowing Machine. This is by far the most under-utilized piece of equipment in the gym. More then any other piece of equipment, the rowing machine will provide not just a cardiovascular benefit but also an anabolic benefit. You actually will provide your body with resistance. Cardio and muscle growth. Get someone to show you the proper form so you don’t end up icing your low back as you are laying motionless in bed the next day and then try the above mentioned interval program.
  • OK, my favorite, and don’t laugh. A jump rope. This I rank as the #1 cardio activity you can do for losing fat and preserving muscle. I am not talking about double-dutch in the schoolyard. A good speed rope and an intensive program will give you the most intense workout around. Burning as many calories in 10 minutes as 30 minutes of jogging or 2 miles in 6 minutes of cycling, rope jumping is a calorie killer. It has also been shown to increase natural anabolic hormones as well as improving speed, agility, quickness, and power. A good rope is under $30 and can go anywhere, so you don’t have to miss a cardio session even on vacation! (Sorry).

If you don’t think rope jumping has a place for competitive bodybuilders of figure competitors, check out you copy of pumping iron (if you body build you’ve seen it). Ignore Arnold’s cocky rants with Louie or his description of why he loves the feeling of the pump. Instead find the scene of Franco doing cardio pre-South Africa Olympia. He has about 15 guys sitting there watching him workout. What was everyone watching him do for cardio? He was using a jump rope, which will take you way above the ‘fat burning’ zone. If you want to learn how to incorporate rope jumping and programming you can grab a copy of Buddy Lee’s book, Jump Rope Training, it will tell you all you need to know. If there is interest I could provide an article on the topic in the future.

Hopefully everything is making sense. So get away from those boring sessions walking on the treadmill counting down the minutes. Put the same intensity into your cardio as you do into your weight training and you will reap the benefits. It has always amazed me to see people kill themselves in the weight room and then slack it with the cardio, mostly because they think they are doing the best thing. Work as hard as you can as long as you can, if you feel like you are going to pass out, take a break, then get up and do it again.

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