The mysterious “fat burning zone” continues to confuse many gym-goers. The theory goes something like this: working out in a “zone” of intensity that is less intense for at least 20 minutes will burn more fat calories than calories from carbohydrate. Is this true? Yes and no, but mostly no. You actually burn more calories from fat right now, sitting still, reading this post, than you do on the treadmill. That is because in the resting state, the body burns a higher percentage of fat calories. As you crank up the exercise intensity, you burn a little less fat per calorie. However, it really comes down to the total number of calories you burn per exercise session — if you want to lose weight.

Here is an example:

Let’s pretend for a moment that you decide power walk for 40 mins on the treadmill. This would burn approx. 5 to 6 calories per minute. After 40 mins, you will have burned 200 to 240 calories. Not bad. Percentage-wise, about 50% of these calories will come from fat, so about 100 to 120 calories.

Now, let’s say you decide to add running intervals to your power walk at a 1:1 ratio, meaning that for every bout of less intense cardio, you do an equal-length interval that is more intense. After 40 mins of this type of intense activity, you will likely have burned between 400 to 450 calories. A bit less fat is burned during intense activity, BUT, you burned more total calories. So, if 40% of those calories come from fat, you will have burned 160 to 180 fat calories!

This was a simple example of how interval training can turn up the calorie-burn. Try adding intervals to your current cardio routine if you want to 1) burn more total calories and 2) burn more fat!

Dear Diane,

I’ve signed up for a 5k race in May and after 3 months of “training,” I still can’t go much further than a mile without stopping to walk. What am I doing wrong?

Colleen

This question is from last spring, but with racing season well under way, it seemed like a good time to post my answer on the blog, as I’m sure many of you have run into this dilemma, or know someone who has.

A typical fitness routine includes the same type of cardiovascular activity, performed for the same length of time, with little variation – and while there isn’t anything inherently wrong with this approach (it is exercise, after all), you probably won’t improve if you continue to do the same thing. To boost endurance (i.e, go longer, faster), something has to change. There are 3 easy ways to improve endurance:

1. Add time to at least one cardio session per week for several weeks, then taper for one week to allow the body to adapt to the increased load. Then start back up where you left off, again adding time to at least one session per week.

2. Make one session per week more intense (harder). Speed work (400×6 sprints, for example), hill-work, or interval training (combine speed and hills, alternating between the two).

3. Strength train. Even the best endurance plan will fall short of success if there are muscle weaknesses. To improve endurance, muscles must be strong, so include at least 2 days of strength training per week.

Recent research indicates that one solution to aging (slowing it down, that is), lies in the ability of our muscles to maximally use oxygen, both at rest and during exercise. In fact, regular aerobic exercise may decrease biological age by as many as ten years. Maybe more. (British Journal of Medicine, Dr. R. J. Shepard, 2008) The harder you exercise (read: Intense!) the greater the reduction in biological age.

I’m a huge fan of interval training, and when I read these studies promising such benefits, I just get giddy. Interval training is one of the most effective ways to achieve the level of intensity needed to increase the oxygen demands of your muscles. Maximal oxygen consumption peaks at around age 35, and as with all things, declines with age – especially so after age 60.

I’m tackling cardio interval training in this blog, but similar tactics can also be applied to strength training. It’s almost a sure bet you’ll see that post next!

Interval Training = intense exercise (all out effort) for short bursts. For the purposes of this post, and assuming you are in good health, 1-3 minutes should do the trick. This may seem overly simplified, but a good example would be your regular running workout. We call this “steady state” training – your pace is constant, your breathing is comfortably challenging, you could go all day at the same pace. Interval training shocks the system, so to speak, by elevating the heart rate to about 85% of its max. This is where the real changes that slow aging take place.

Incorporating interval training into your workout

There are many ways to skin this cat. To keep things simple, I’ve listed the most common ways interval training can be incorporated into a steady state workout:

• Increase your speed. Make certain you are injury free and in good health before you choose this method, as increasing speed has been linked to higher injury rates than other modes. (Carrol et al. 1992)
• Add impact. Squat jumps, burpees (squat thrusts), explosive jumping from the ground to a stair step or other raised platform…anything that briefly increases the intensity the exercise you’re doing. I like to incorporate plyometrics into track workouts, where running/jogging laps are briefly interrupted with a set of high-knee skips, explosive lateral shuffling, or power jacks (exagerated jumping jacks).
• Add resistance. If you’re working out on a stationary cycle or elliptical machine, this is a very simple component to change. Simply increase the resistance for short bouts. To determine if the resistance is hard enough, I use this general rule of thumb: if you have to lower resistance after 15-20 seconds, the resistance is too high. If you can continue past 3 minutes, it is likely too easy. In other words, after 1-3 mins, you WANT (or need) to end the interval and begin a 2-3 minute recovery.
• Increase the incline. This is easier to manipulate on a treadmill, however hill work can be incorporated into an outdoor workout too. If you’re on the treadmill, you can keep the speed constant, but increase the incline for short periods. Again, 1-3 minutes is sufficient. One of my favorite outdoor versions of this involves my sister-in-law’s neighborhood in Wake Forest, NC where the hills are steep and abundant. When we visit, I lace of up shoes, warm up for 5-10 minutes,  and head one block south of her home where the route around this large block starts uphill, then levels off before going down hill for the recovery part of the workout. I credit this workout with helping me tackle the hills in last spring’s Flying Pig half-marathon in Cincinnati.

Make sure the recovery portion of the interval is two to three times as long as the all-out effort. If your interval was 1 minute long, then the recovery should be 2-3 minutes. Perform your interval workout once per week for starters, increasing to two times per week (not on successive days) to see further improvements.

* Note: Blue Sky Gym and the author disclaim any liability for any injury, physical or emotional, suffered during or as a result of exercise or activities recommended. As always, you should use common sense and consult your health professional before beginning any exercise routine or program.