WHAT IS INTERVAL TRAINING?
The three main components of an effective weight-loss program are proper diet, efficient resistance training and cardiovascular conditioning. Yet ideas about what a proper cardiovascular workout to induce weight loss consists of are many and varied, including the myth of the fat burning zone. The following will help you to design a good cardio program for yourself regardless of the type of exercise you choose.
The myth of the fat burning zone
The fat burning “zone” is, supposedly, when the body is primarily using fat as its fuel. This can be determined by using a metabolic chart to measure an individual’s respiratory exchange ratio (RER), which is simply the amount of CO2 exhaled, divided by the O2 inhaled. The highest percent of fuel from fat is used when the body has an RER of .71. This is where the fat burning “zone” falls short. The only time the body can be at .71 RER is at complete rest, which means it’s not burning a large amount of calories. As activity level increases, so will the RER. What some professionals call the “fat burning zone” has an RER of .80 to .90. At this level (reached from moderate exercise such as brisk walking or light jogging), 40 to 60 percent of the calories from fat can be burned. This is a good range or zone for beginners, however if a person stays within this zone, they will hit a training plateau, and fitness level and fat-burning capacity will not increase.
On the other hand, some individuals work around a level of 1.0 RER (anaerobic threshold occurs before an RER of 1.0), assuming that the harder they work, the greater the cardiovascular benefit. These individuals are burning mainly carbohydrates for fuel and, of course, more calories. The bottom line for losing fat is to burn more calories than are taken in. The problem, however, is that even individuals who work at a higher intensity will also plateau. It’s a common frustration among people in group fitness classes and people who work out on bikes and treadmills. Despite their efforts to burn fat, these people generally look pretty much the same month after month.
The solution is to overload the body. If someone performs at the same level of intensity every cardiovascular workout, the body isn’t overloaded. This is where interval training comes in. The individual should aim for an RER of 1.1 (or an individual peak) for short intervals, returning to the fat burning zone to recover. Hitting the peak and then returning for an active recovery in the fat burning zone is a “true” interval.
Benefits of true interval training
To see how true intervals can be more beneficial than anaerobic threshold training or training in the fat burning zone, let’s look an example of a 150-pound individual on a stationary bike. In the fat burning zone, the subject could burn approximately 82 Calories during a 30-minute session. Half of those calories could come from fat, thus the name “fat burning.” As this same individual bikes at a harder level for the same period of time, up to 152 Calories can be burned, but only a small percentage might come from fat. During a more effective interval workout, a person starts in the fat burning zone then slowly works their way through the anaerobic threshold until they hit their peak for 30 to 60 seconds. After the peak, the exerciser returns to their fat burning zone to recover before starting the next interval. The individual must return to an active recovery period before starting the next interval. Active recovery is the equivalent of a walk or light jog without stopping to take a rest (later referred to as Zone 1). With this particular workout, the same individual would burn 173 Calories, and many of those calories could come from fat.
For interval training to be effective, the entire interval must be long enough for exercisers to reach their peaks and recover within their recovery zone. If intervals are too short, anaerobic threshold training, not interval training, is being performed.
The benefits of true interval training are an increase in calories burned, and a possible increase in fat burned. Plus, members may find that they are more challenged and motivated by their cardiovascular workouts since they continuously change. In addition, by overloading the heart and respiratory system, endurance and cardiovascular fitness levels are increased. This is the same principal used in resistance training — overloading the biceps will result in an increase in the strength of the biceps, and overloading the heart muscle will improve its strength. Another important benefit of true interval training is increased metabolism. Interval training can increase metabolism after a workout and keep it up longer than a steady-state workout.
Finding the zones
To perform true interval training, people must know their heart-rate zones. There are two ways to find these zones. One is to use a metabolic cart. This method accurately pinpoints the zone using the ratio of CO2 to O2. With new portable units on the market, fitness centers can now offer this service. The second method is to use age predictions. This works well for beginners, but adjustments will have to be made as fitness levels increase. (The “peak” zone will need the most adjustment.) A comfortable peak level is when the heart rate that can be maintained for 30 to 60 seconds. (The person then returns to Zone 1 for five to 10 minutes before performing another peak interval.) Using the standard formula, subtract the person’s age from 220, and use that number to figure out how many beats per minute is at 65 percent, 75 percent, etc., of the maximum heart rate. For example, a 30-year-old will have the following resting zone rate:
220-30=190, and 65% of 190 is 123.5. Therefore, this person should have a resting interval rate of about 123.5 BPM.
Figure out the person’s heart rate for each of the following zones.
Zone 1 (recovery zone) — 65 percent of maximum heart rate
Zone 2 (anaerobic threshold) — 75 to 85 percent of maximum heart rate
Zone 3 (peak training zone) — 90 percent of maximum heart rate
The peak heart rate zone (Zone 3) should be challenging without causing burnout. After several sessions using the training zones provided by the heart-rate formula, it will be time to make some adjustments. Gradually add 2 to 3 beats per minute to each zone, then try the workouts three or four times before making another adjustment. Once a comfortable peak is found, the goal is to gradually increase the amount of time spent in Zone 3 during each interval. The goal is not, at this point, to increase the beats per minute any further.
To help achieve true interval benefits, varied workouts should change the workload (speed, incline, level, etc.). The following stages are recommended guidelines to achieve such variation.
Stage I. This stage is for beginners who have not been working out. They should start slowly and work up to 30 to 60 minutes in Zone 1, and remain at this stage for two to three weeks before moving to Stage II. The workload may change, but what is important is that the individual stays in Zone 1.
Stage II. Stage II is the introduction to interval training. During the exercise period, exercisers begin by warming up in Zone 1 for 10 minutes. Then, they perform a one-minute interval within Zone 2. Once they reach the high end of the anaerobic threshold zone, they must maintain that level for the remainder of the one-minute interval. This may mean that someone will work within the top of Zone 2 for only 15 seconds before they reduce their workload and return to Zone 1.
Although they may be at Stage II, exercisers should alternate their sessions between Stage I (light) days and Stage II (hard) days. These alternating sessions will become very important as they progress to Stages III and IV.
Stage III. This stage is for those who have worked their way through Stage I and II and may have hit a plateau. During the exercise period, they should begin in Zone 1 and, after 5 minutes, increase their workload every 30 seconds until they reach Zone 3, where they should stay for one minute. Next, the individual should decrease their workload back to Zone 1. The goal is to reach Zone 1 within a one-minute period. As improvement is made over several weeks, the heart rate will drop more quickly, which means the heart is getting stronger.
After several months of interval training with the heart rate consistently dropping to the same number, this recovery heart rate can be used as a gauge for overtraining. For example, an individual with a peak training heart rate of 160 recovers over a one-minute period to a rate of 140 on a normal day. If the rate drops to only 150 BPM, this person is overtraining and should stay in either Zone 1 or 2 for the remainder of that workout. Other signs that an individual is overtraining are insomnia or total body fatigue the following day. Rest is the best solution, but proper nutrition also plays an important part in successful interval training. A high number of individuals who are not reaching their goals are actually overtraining, not under-training.
When the individual’s heart rate consistently drops to the normal recovery rate over a one-minute period, it is time to overload the body again. After remaining in Zone 1 for 10 minutes, keep repeating the interval for the duration of the workout. If the peak range was reached and maintained, the 10-minute rest will be needed before beginning a new interval. Remember to rotate workouts performing Stage I one day, then Stage II and then Stage III. This will keep the workouts balanced and should prevent overtraining.
Stage IV. During this stage, programs are designed based on daily goals, much like resistance training when a person works the upper body one day and the lower body the next. The following four goals can be used as guides when designing true interval workouts.
1. Cardiovascular/respiratory exercise. These days are designed to increase overall cardiovascular fitness. The main focus is to strengthen the heart and respiratory system by reaching the peak zone often throughout the workout and returning to the recovery zone for an active recovery. This program strengthens the heart without overworking the legs.
2. Leg strength/toning. Some of the best toning or strengthening for the legs can be accomplished by using a stationary bike or stair machine. On toning days, the workload should be slowly increased while putting stress on the legs. If exercisers are unable to go beyond level two or three on the stationary bike or stair machine, they need to strengthen their legs so they can exercise at a higher level.
3. Endurance. Group fitness classes and most pre-set programs on bikes, treadmills and stair machines do a good job of maintaining endurance. These programs keep exercisers at or near their anaerobic threshold for a long time. This cardio program is good for maintaining fitness level, or to use a few days a week for a medium-intensity workout. It is important to only use this program to build endurance and not use it every day.
4. Recovery. This program is active rest, and is equivalent to a walk (or staying in Zone 1). Recovery workouts should be done at least once a week. To truly improve, the body must have proper rest. The heart is a muscle and can only train so long before it will need rest.
Designing the workout schedule
In addition to designing workouts, weekly schedules are also important. Schedule low-, medium- and high-intensity workout days with a set goal for each. The first workout could be a low-intensity walk for recovery. The next workout could spend more time in Zone 2, with hills in it to overload the legs and improve strength, or it could be an aerobics class. The third day could be high intensity and could either concentrate on cardio strength or leg strength by spending more time in Zone 3. With set goals and changes in intensity, each cardio workout can be challenging.
Mayo Clinic Interval training.
Amherst College Athletic Recruiting.