Fitness Forum:

Jason Karp’s article, “The Fat-Burning Zone” [October 2009 IDEA Fitness Journal], was very informative as to the mechanisms by which fat is oxidized. I agree that high-intensity interval training is an excellent way to burn more calories and increase cardiovascular fitness. However, I take exception to his specific workout recommendations that we should have our clients doing 5–6 reps of 3-minute intervals at 95%–100% max HR or 4 reps of 4-minute intervals at 95%–100% max HR.