Heart Rate-Based Interval Training
How would you like to burn more calories, in less time, burn more calories for hours after your workout and increase your metabolism long term? Heart rate-based interval training may be for you. This is high-intensity exercise. Check with your medical provider before attempting. It’s also quite advanced. Some level of fitness is required before you begin.
As an undergraduate exercise science major in the early ‘80s, I was taught the most efficient way to burn fat was aerobic exercise at moderate intensity, long duration and a steady state. I know that’s a mouthful, but stay with me and I’ll explain this.
Moderate intensity is approximately 60% of a person's predicted maximum heart rate (220 - age = predicted maximum heart rate). Long duration is 40 to 60 minutes or longer. Steady state means that, apart from the warm-up and cool-down, the intensity remains relatively constant. Aerobic refers to how your body uses oxygen to sufficiently meet energy demands during exercise. It uses large muscle groups, it’s rhythmic and it can be sustained for at least 10 minutes. While this type of workout does use fat as the primary fuel, interval training may be more productive for fat loss.
The diagram below illustrates how this works. Keep in mind that it’s not drawn to scale. (Yes, I did draw it myself. I’m a physiologist, not an artist.) The horizontal line represents time. The vertical line represents intensity. This could be expressed as V̇O2, or milliliters of oxygen per kilogram of body weight per minute (mlO2/kg/min) or as calories per kg per min. (kcal/kg/min). Both are standard measures of metabolic rate.
During exercise, heart rate is relatively proportionate to these measures. During recovery, heart rate decreases rapidly, while metabolic rate declines slowly.
The purple baseline represents resting metabolic rate (RMR) before training. The green line represents RMR after training. The blue line illustrates a steady state workout. The red line depicts an interval workout. The area with the blue diagonal lines shows the time when metabolism remains elevated, as your body recovers from the steady state workout. The area with red diagonal lines represents recovery from the interval workout. Even though the time spent in the training phase (represented by the spiked graph) is less than half the time of the steady state workout, the recovery phase is several times larger.
This is part of the beauty of interval training. You work harder for less time and you get a bigger payoff.
One payoff is that your metabolism remains elevated at a higher level and a longer time after your workout. Another payoff is that when you train this way long term, resting metabolic rate becomes higher. Both of these features are important if losing fat and maintaining a healthy weight are your goals.
Think of it this way: You’ve finished your
workout, had a shower and gone to work or home for dinner. You will continue to burn more calories for hours to come. Increased resting metabolic rate means more calories burned all day, every day. Combine this with proper weight training and you can avoid much of the reduction in metabolic rate associated with aging.
How do you go about doing interval training? One way is to take classes. At Premier Health & Fitness Center, we have numerous classes that employ different interval training schemes. Other clubs, gyms and studios do as well. Another approach that I like personally is heart rate-based interval training on the treadmill, spin bike, rowing machine or in the pool. Here’s what I do:
- I begin by warming up for 5 to 7 minutes. On the treadmill this involves walking at 2.5 mph at a 5% incline. (Keep in mind these speeds and inclines are based on my heart rate. Your numbers may be very different.)
- I increase the elevation of the treadmill to its maximum 15%. When my heart rate gets to 95% of maximum, I return the elevation to 5%.
- When my heart rate returns to warm-up level (or about 64% of max) and goes no lower, I increase the elevation back to 15%.
- I repeat the process as many times as time permits—or until I holler, “UNCLE!”
- On the treadmill, I use the built-in heart rate monitor. When using the spin bike, rowing machine or swimming I go by rating of perceived exertion (RPE; a subjective self evaluation how hard I’m working), as I don’t have my own heart rate monitor.
- On a spin bike, I follow warm-up at 80 to 90 watts by an increase in resistance and pedal speed getting to 180 to 200 watts for about one minute. This gets me to an RPE of 18 or 19 (“very, very hard”), on a scale of 6 to 20. I reduce resistance and speed to a wattage of 80 to 90 until my RPE gets to about 10 or 11 (“fairly light”).
- On a rowing machine, I row as hard as I can for one minute. That will be an RPE of 19 or 20. To recover, I stop rowing and wait until I return to 10 or 11.
- In the pool, I swim one lap, up and back, as fast as I can go. I then stand in the shallow end, until I recover to an RPE of 10 or 11.
Interval training, whether based on time, heart rate, or rating of perceived exertion, is a great way to get off a plateau in your weight loss process. It can make more efficient use of training time and yield better long-term results. If you’re already fairly fit and are healthy enough for high intensity exercise, adding interval training may be a great addition your workouts. As always, if I can help you with this (or anything else) please contact me at the below.