By Rick Morris
You’ve probably been fairly faithful with your winter workouts. You’ve been hitting the treadmill or running outdoors for some calorie-burning running workouts, but have you been running hard? Have you been doing any high-intensity interval training? If the answer is no, or not always, and you want to get your body ripped and lean, you may need to change the way you exercise with high-intensity interval training (HIIT) cardio.
Interval training is a technique in which you run at high-intensity paces for a short period, then slow to an easier pace for recovery before doing it all over again. Interval training has been used by competitive distance runners for many years to improve their VO2 max or maximal aerobic capacity. Your VO2 max is simply a measure of the maximum amount of oxygen your body can process to produce energy. A high VO2 max is a critical measure for a distance runner, but does it really matter for someone who is running for fitness or fat burning? It sure does!
Raising your VO2 max makes your body fitter and more efficient at producing energy. That increased fitness level allows you to run at faster paces for longer periods of time. Even your “easy running” pace becomes faster. For example, if your current “easy run” pace is 10 minutes per mile, you may be able to increase that speed to 9 minutes per mile – or faster – after a period of VO2 max training. Running faster translates to burning more calories and more fat per minute of running. High-intensity training also builds more fat-burning enzymes in your body, which raises your overall metabolism.
A study conducted at the University of New South Wales in Australia looked at the effects of high-intensity interval training on fat loss. Researchers concluded that high-intensity interval training (HIIT) three times per week for 15 weeks resulted in significantly greater reductions in total body fat, subcutaneous leg and trunk fat, and insulin resistance.
When you should you start to add HIIT to your training program? There isn’t a “hard and fast” rule on that one. You shouldn’t do HIIT until you have built up a substantial base of fitness that will support the harder training runs. I would not suggest doing HIIT until you have been running consistently for at least eight weeks and are able to run 3 miles without difficulty. Once you reach that level, your fitness has improved enough that you should be able to safely complete HIIT.
The first question that needs to be answered before you start HIIT is how fast you should run. The concept of VO2 max has been around for a long time, but a more recent concept revolutionized training methods used to improve VO2 max. That concept is the minimum running speed that elicits VO2 max. This concept was named velocity @ VO2 max (vVO2 max).
The concept of vVO2 max opened up a whole new world of possible running workouts. It became obvious that the best way to improve your VO2 max is to run at vVO2 max. Running at that velocity forces your body to improve its ability to run at VO2 max and makes further increases in your fitness level and VO2 max.
Now you know that you want to run at your vVO2 max, but how fast is that? An experienced runner will have a good idea of their vVO2 max pace, which is right around 3,000-meter race pace. Since you may not know your 3K pace, the best way to determine your proper pace is by the rating of perceived exertion (RPE), which is a scale from 1 to 20 that rates how hard your workout feels. There are some time trials you could do, but they are very difficult and not especially accurate for inexperienced runners. On the RPE scale, a 1 means very little effort and 20 means all-out effort. At 70 percent of VO2 max, your rating should be about 14; at 80 percent, your rating should be about 16; at 90 percent, your rating should be around 18 and 100 percent, your rating should be around 19. The most efficient training intensity to improve your vVO2 max is at RPE 19. That is a very hard pace and one that you will need to gradually build up to.
Here are six HIIT treadmill/outdoor running workouts that will safely take you from running at 80 percent of your VO2 max (RPE 16) to 100 percent of your VO2 max (RPE 19). For all treadmill workouts, keep your machine elevated to 1 percent or level one, to match the intensity of outside running.
Warm up with 5 minutes of easy running. Then run for 15 minutes, alternating between 15 seconds at 90 percent of VO2 max and 15 seconds at 80 percent of VO2 max. Cool down with 5 minutes of easy running.
Warm up with 5 minutes of easy running. Then run for 20 minutes, alternating between 15 seconds at 90 percent of VO2 max and 15 seconds at 80 percent of VO2 max. Cool down with 5 minutes of easy running.
Warm up with 5 minutes of easy running. Then run for 15 minutes, alternating between 15 seconds at 100 percent of VO2 max and 15 seconds at 70 percent of VO2 max. Cool down with 5 minutes of easy running.
Warm up with 5 minutes of easy running. Then run for 20 minutes, alternating between 15 seconds at 100 percent of VO2 max and 15 seconds at 70 percent of VO2 max. Cool down with 5 minutes of easy running.
Warm up with 5 minutes of easy running. Then run for 20 minutes, alternating between 30 seconds at 100 percent of VO2 max and 30 seconds at 70 percent of VO2 max. Cool down with 5 minutes of easy running.
Warm up with 5 minutes of easy running. Then run for 20 minutes, alternating between 1 minute at 100 percent of VO2 max and 1 minute at 70 percent of VO2 max. Cool down with 5 minutes of easy running.
Very short interval training around the critical velocity allows middle-aged runners to maintain VO2 max for 14 minutes. Billat VL, Slawinksi J, Bocquet V, Chassaing P, Demarie A, Koralsztein JP. Int J Sports Med, 2001 Apr;22(3):201-8.
The effects of high-intensity intermittent exercise on fat loss and fasting insulin levels of young women. Trapp EG, Chisholm DJ, Freund J, Boutcher SH. Int J Obes, (Lond). 2008 Apr;32(4):684-91.