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[han-grrl]

Keeping your heart rate low to burn fat is one of the many fitness myths around. In order to use fat for fuel you need A LOT of oxygen, hence the myth of keeping low heart rate to use fat as a fuel. What it is actually is that at lower heart rate, the PERCENTAGE of fuel that comes from fat is higher, HOWEVER, because fat produces so much energy in the form of ATP, not much fat is actually used (or needed). At higher intensities, even though the perecentage of fat is lower, the total number of calories burned is actually higher. More CALORIES from fat is used at higher intensity than at lower intensity. Using a simple example, lets say that a light walk for 30 minutes burns 100 calories, 60% of which comes from fat, and 30 % from carbs. that means 60 calories from fat are used. Now say that you change this light walk to a light jog, burning a total of 300 calories, but only 30% of those calories comes from fat, BUT that 30% is 90 calories coming from fat - 20 more than the light walk. this is oversimplified, but you get the idea. The best thing to do if you are trying to burn fat is to go as hard as possible for as long as possible. People have a hard time pacing themselves though and as hard as possible means at best 5 minutes. So using the keeping your heart rate low advice forces people to pace themselves.

The idea of keeping heart rate low is to build your endurance. Many people tend to work at a heart rate of over 85% of their max heart rate without having good base training. This is like building a tower without a good foundation. Aerobic base training is vital to training and is often neglected. My suggestion to my clients is that if they work on building to an hour long session at 65-75% of their max heart rate before doing higher intensity work.

Hope this helps

Happy Spinning

Hannah