Interval training (HIT) involves a combination of high and low-intensity training within a single workout session. In this session, the individual alternates between a bout of higher intensity exercise followed by a lower intensity or "active recovery" bout. This type of training is in contrast to the more familiar "steady state" exercise where the intensity is much lower but longer in duration. Interval training is awesome for fat burning and aerobic conditioning but let's have a look at some more reasons to use interval training for your cardio workouts.
What are the benefits of interval training?
1. Intervals vastly reduce boredom. Traditional steady state cardio training can become quite boring. HIT offers more variety and excitement to your workouts.
2. Interval training increases post-exercise energy expenditure (calories burned following exercise) more than steady-state exercise, which means that more fat is burned. After intense exercise, the body needs extra calories as it works to repair muscles, replace energy stores (ie carbohydrate) and restore the body to its normal state (eg reduce heart rate). As this can take many hours, you will keep on burning more calories long after the workout is over. In fact, research shows that metabolic rate is higher for several hours following interval training compared to steady state exercise.
3. Interval training stimulates the respiratory system, cardiovascular system and nervous system to a greater degree. Therefore, more fat and carbohydrates are burned to support the expanding energy demands of the body during, and after, intense exercise.
4. Interval training increases the activity of enzymes involved in fat burning. Research has shown that after a bout of interval training there is more fat in the blood (ie free fatty acids), which is an indication of more fat, being used for energy production.
5. HIT burns more calories. As an example, 30 minutes on an Elliptical machine using a steady state program will burn roughly 292 calories, whereas 30 minutes of intervals will burn approximately 584 calories!
6. HIT causes a greater increase in VO2max (aerobic capacity). By stimulating your cardiovascular system to work closer to its maximum capacity for a longer duration than steady state exercise.
7. HIT allows for better time efficiency. For instance, a typical 30 min steady state run on the treadmill could be reduced to 10 – 15 min of HIT due to its demands on the aforementioned systems.
8. HIT results in increased amounts of circulating growth hormone (GH) following exercise. This Promotes an increase in lean body mass and increased fat burning. This does not occur to the same amount with steady state exercise. This is particularly beneficial for those looking to maintain their muscle mass and at the same time reduce body fat.
9. Interval training makes use of both aerobic (type 1) and anaerobic (type 2) muscle fibers. This is in contrast to steady state exercise that only makes use of type 1 fibers. By increasing the condition of these type 2 muscle fibers you will greatly increase your capacity to tolerate high-intensity exercise, which means an increased opportunity to exercise at higher levels that burns a lot of calories.
10. Because of the high-intensity of this exercise and the increased use of anaerobic type 2 muscle fibers there is an increased use of the body's glycogen (muscle-stored carbohydrates) stores. This is very beneficial for fat loss as the body will conserve carbohydrates following exercise and then use fat as an energy source for the body's energy requirements. The more glycogen you use during exercise the more fat you will burn following exercise!
Guidelines for Interval Training
1. Intensity of high-intensity interval
2. Intensity of low-intensity interval
3. Duration of high-intensity interval
4. Duration of low-intensity interval
5. Number of Intervals
Because of its versatility, HIT offers 1000s of different program variations. This is great for those looking for variety and change. After all, the body adapts best to changing stimuli. Furthermore, this type of training can be done on any cardio machine. Again, switching between machines periodically will stress your body differently and lead to the best results!
It is recommended that the intensity for the high-intensity interval range between 75 – 100% of your maximum effort. This will depend on the duration of the interval, as the longer the interval, the lower its intensity.
The recovery interval should range in the 55 – 65% of maximum effort.
The ratio of work to recovery can be varied and will depend on your fitness level and desired goal. For instance, I recommend starting at a work: rest ratio of 1: 4 for beginners. As an example, this could represent a high-intensity (work) interval of 15 seconds followed by a 60 second recovery interval. If you are more advanced you can play around with this ratio for increased difficulty.
What you will notice is that over the duration of the interval training session your average heart rate will tend to drift upward. This is due to the fact that, depending on the interval protocol and your fitness level, the length of your recovery bouts will not be sufficient to allow your heart rate to fully return to rest; so, you end up working at a greater percentage of your maximum heart rate even while you recover.
Here is a sample 10-min interval training workout that is sure to leave you exhausted:
1. 10 seconds at 100% effort
2. 20 seconds at 60% effort
3. Repeated 20 times