The density of the bentonite particles. calculated from these data is 2.457 _+ 4 x 10 -7 g/cm 3. and the compressibility is 0.12 x 10 -12 _+ 2 x 10 -20. cmZ/dyne. The +_ values are asymptotic standard errors.
The bottom line is this: You burn fat and build cardiovascular fitness at both low and high exercise intensities. The logic is that at lower heart rates you burn more fat. At higher heart rates you supposedly burn less fat but get a better cardio workout. This is partly true, but let's take a closer look. For a 20 minute workout performed at a lower heart rate, you burn proportionally more fat as a fuel source, but fewer overall calories per unit of time.
Our bodies burn fat best as we exercise at about 65-75% of the max heart rate for our age and sex. The only thing I could suggest would be to make sure the treadmill is going at a sufficient speed for you to achieve the right heart rate. You might like to consider other good exercises like eliptical trainers and the rowing machine for a bit of variety.