Posted by: Taz | 2008/11/16

Get this junk out of my trunk!

Hi Doc

It seems there are too many " experts"  with their own opinions.
I need to know, please, at what heart rate I should be cardio training at to lose about 6kgs. I have been told 165bpm for 40-60mins as Il be burning alot more calories as its quite high intensity (I am relatively fit anyway), but then Iv been told " that person who told you that is crazy, youll only be burning carbs, you need to train between 130 and 150 max for 45mins as youl be in fat burning mode."  So what is best doc? I do power plate 2-3 times a week as resistance training (which I have definitely noticed a difference) but with regards to the cardio, which heart rate and for how long and how many times a week if I want to lose 1kg a week. (I know I must eat right too)

I am female, 26 years old, 1,76m tall and weigh 68kg. I know Im in a healthy weight range, blah blah, but I am a size 12 and want to be a 10, which I know I am if I weigh 62kg.

Thanks for your time and keep up the great work!!

Not what you were looking for? Try searching again, or ask your own question
Our expert says:
Expert ImageFitnessDoc

Hi Taz

Yes, indeed, far too many experts when it comes to heart rate and training. Ever since people noticed that heart rate goes up as intensity goes up, they have used it to gauge exercise intensity. Then, when it was noticed that the fuel that is used also depends on the exercise intensity, it was thought that heart rate monitoring was a good way to train at just the right zone to burn fat. In theory, this is true, but there is more to it than this. What happens is that at low exercise intensities (less than 60% of maximum), the main source of fuel used by the body is fat. As exercise intensity increases above 65 to 70%, progressively more and more of the energy that is produced comes from the carbohydrate stores, meaning that fat contributes a smaller overall percentage of the total energy use.

However, and many people forget this, the overall energy use also increases, so that, even though fat might be contributing less as a percentage of the energy, it is still being used in larger quantities. That means that the total amount of fat being burned per minute might actually be higher at higher intensities, which is what you want. The example is that you could have 50% of 1R, or you could have 20% of R10. Which is more? It doesn't matter that you have 50% of your energy coming from fat, what is more important is the TOTAL energy. So that's far more important.

So, many people make the mistake of trying to go at a low intensity, to burn fat, which means that they are probably using more fat than carbohydrate, but the overall energy used is so low that the results are barely noticeable.

SO, basically, the body does not have certain ‘zones’ at which it uses just fat and then just carbohydrates – there is no on-off switch, but a gradual change from fat to carbohydrates, which means that you have to find the exact intensity to burn more fat in total, not more fat as a percentage, if you follow my logic. Also, at slightly higher exercise intensities, the total energy that is being used is greater, which means that the total amount of fat that is being used is also greater – so, to answer the question, I’m more in favour of higher intensity training to burn fat. However, a word of caution, this does not mean going out and training hard all the time. You have to find the right balance. Your goal should be to use the greatest total amounts of fat, and this means that the duration of the training must also be long enough to burn more fat. So, it’s not only the intensity, but also the duration that is vital. That’s why you can’t just go out and train at 90% of maximum – you would tire very quickly, meaning that your total fat and energy use would be relatively low.

Therefore, my advice would be to aim for an intensity between 70 and 80% of maximum. In your case, anything between 150 and 175 bpm would probably be about right – the main thing is to be able to finish a session of 45 minutes or so of training feeling like your breathing is elevated, that you’ve had a hard session, but that you are not completely exhausted. The other piece of advice is that you could also exercise at a low intensity (60 to 70%), with short periods of high intensity in between. So, say you are cycling for 45 minutes, every 9 or 10 minutes, you could pick up the intensity for one minute. This type of training is very good for fitness, performance and weight loss.

Good luck

The information provided does not constitute a diagnosis of your condition. You should consult a medical practitioner or other appropriate health care professional for a physical exmanication, diagnosis and formal advice. Health24 and the expert accept no responsibility or liability for any damage or personal harm you may suffer resulting from making use of this content.

Have your say

Thanks for commenting! Your comment will appear on the site shortly.
Thanks for commenting! Your comment will appear on the site shortly.