I hope you had an enjoyable holiday Labor Day weekend and summer vacation! As the kids are going back to school and summer vacations come to an end, many individuals begin to refocus their efforts towards their own personal health and fitness goals. Often times those fitness goals involve shedding excess pounds gained by indulging on vacation, and maybe not exercising as routinely over the past couple months. The majority of individuals will take to the streets and start jogging again, got to the gym and log miles on the elliptical or go on long bike rides in an effort to burn calories and lose weight. This unfortunately, is a very misleading perception on the most effective path to fat loss. Time and time again, I see individuals, especially women; spend hours each week subscribing to cardio workouts in the hopes of getting that lean and toned look of the celebrities. What they fail to realize is that all that time spent jogging, or being on the elliptical is fighting against them.
Here is where the long duration cardio exercise idea came from:
When individuals perform aerobic cardiovascular exercise between 50-65% of their maximum heart rate (MHR), the body’s primary source of fuel for this type of activity is stored body fat. When working at 50% of your MHR, approximately 60% of your energy will come from fat, and the remaining 40% will come from glycogen stores. When the exercise intensity increases to 75% of MHR only 35% of energy comes from stored fat, and 65% from glycogen, and as the intensity increases even more, the ratio of fat to glycogen use decreases even further.
It was the higher ratio of energy from stored fat at lower exercise intensities that led many to believe the best way to reduce overall body fat resulted from completing long periods of steady state cardiovascular exercise. This was deemed the ‘fat burning zone’. What many scientists have discovered since is that high intensity interval training (HIIT), where a series of high intensity efforts are interspersed with periods of rest or active recovery has been shown to be a far more effective method of reducing body fat. A recent Australian study by Trapp et al (2008) found that females who followed a 20 minute HIIT program consisting of 8 second sprints followed by 12 second rest lost an incredible 6 times more body fat than a group that followed a 40 minute steady state workout at 60% MHR.
HIIT not only burns more calories in a session than using lower intensity cardiovascular exercise, but the largest benefit of HIIT when training for fat loss is the effect it has on your metabolism afterward. As HIIT is harder for the body to recover from than lower intensity steady state cardiovascular exercise, more energy is required in the period after the workout for the body to repair. A recent study by Meuret et al (2007) found that participants who performed HIIT burned nearly 10% more calories in the 24 hour period after exercise than the group who performed steady state exercise.
That is why I only prescribe HIIT and strength training workouts to my personal training San Diego clients. HIIT workouts also help to develop muscle tone particularly in the legs and abdomen. If you look at the picture below you can see that marathon runners have far less muscle tone than sprinters. Now ask yourself, who do you want to look like?
That’s because sprinting has been shown to:
• Increase the growth hormone (GH) and blood lactate, because this protocol is metabolically more taxing, which will leads to more fat loss over time.
• Induce a testosterone response, suggesting that sprinting is effective for muscle building and creating an anabolic environment.
These two crucial facts play a large role in fat loss. When muscle mass is increased, resting metabolism is also increased. So now you have two avenues for burning even more fat when you are sitting on your butt. Think about it, active muscle tissue requires far more energy to maintain it than fat, and there is elevated metabolism post workout for the rest of the day! This is a no-brainer. HIIT will get you to your fat loss goals a lot faster than those 5 mile runs you have been doing!
Since HIIT is fairly taxing on the body as a San Diego personal trainer, I would suggest not to train with HIIT more than 2-3 times per week. In addition to HIIT cardio exercise you should also include lifting weights on separate days 3-4 times per week to see the most substantial fat loss.