Interval training is any type of physical workout program that involves various intensities of exercise—going from short periods of high, intense work to longer periods of recovery in which only low- or no-intensity work is accomplished. The term can refer to any type of cardiovascular workout, such as running, bicycling, or swimming, in which brief spurts of maximum exertion, called sprint intervals, are intermingled between longer periods of much lower intensity activity, what are called rest intervals. This pair of intervals, or sets of high to low intensity activities are repeated several times to complete an interval training session.
For example, joggers include interval training within their weekly runs by alternating the use of walking and sprinting once or twice a week, in what is called sprint interval training (SIT). Similarly, swimmers can incorporate a couple fast-paced laps for every four or five slower laps.
The recent popularity of interval training over the past several decades has been brought about due to its effectiveness in providing a good cardiovascular work-out. Because the intensity of the workout is varied, it exercises the heart muscle, which improves the cardiovascular system of the body. Interval training helps to improve a person's aerobic capacity because, as one uses interval training on a regular basis, that person is able to exercise longer and at more intense levels. Interval training also provides a comprehensive work-out plan for many types of athletes, along with people who just want to stay healthy and fit.
Interval training is appropriate for most people who are in generally good health. However, if one has problems with the cardiovascular system (such as heart disease), or arthritis or joint problems, then it is recommended that a doctor be consulted before beginning interval training. In addition, if one is over age 45 for men and age 55 for women, it is necessary to first check with a doctor before beginning such a program.
Possibly originating in Sweden where it is called fartlek and meaning “speed play,” the basic idea of interval training is to vigorously exercise for a short amount of time and then slow down for a longer recovery time, only to resume the intensity for another short period followed by another longer break, and to do this many times in succession. This method improves a body's performance, specifically its endurance, speed, and strength.
Many different types of interval training are used. One example of interval training with a bicycle is:
- Step 1: Three to five minutes of warming up on a bicycle that starts out slow and gradually increases in intensity.
- Step 2: One minute of moderate or high intensity bicycling, or bike sprinting, followed by one minute of low intensity peddling.
- Step 3: Repeating the actions of Step 2 six to eight times.
- Step 4: Three to five minutes of cool down that starts at moderate intensity and gradually becomes low intensity and finally no intensity as the interval training ends.
Interval training can also be done with running. The high intensity portion of sprinting is called sprint intervals. They may consist of a time as short as 15 seconds or as long as 20 minutes. An example of sprint interval training is to run at a maximum speed for 30 seconds in a straight line. Running at such fast speeds for 15 minutes would simulate the climbing of a hill, and are also a part of interval training.
Several basic types of interval training are popular with athletes and non-athletes alike. One of them is called high intensity interval training (HIIT). HIIT involves combining very high intensity spurts of exercise with longer amounts of moderate intensity exercise for recovery. It is considered the most strenuous type of interval training but produces the fastest results when it comes to increasing endurance performance and getting physically fit.
Workout music is available that is specially designed to guide one through interval training. Such workout music is available on the Internet and most can be downloaded to a mobile device.
IMPROVING ENDURANCE. Canadian researchers at McMaster University (Hamilton, Ontario) studied interval training and endurance in 2005. They looked at college students who bicycled for 30 seconds at sprint-type speeds and then stopped pedaling or greatly slowed their speeds for four minutes. This group and a control group (which did not do this
interval training) also jogged, biked, and did aerobic exercise two to three times each week. After two weeks, 75% of the interval-training group doubled their endurance on the bicycles. That is, they were able to double their time that they sprinted at moderate intensities before becoming exhausted. None of the members of the control group showed any improvement in endurance over this two-week period. Since the size of the two groups was small, the researchers stated that further research studies were necessary to verify their conclusions.
BURNING FAT. A study from researchers at McMaster University, along with those from the University of Stirling (Scotland) and the University of Guelph (Canada), reported on the use of interval training to improve cardiovascular fitness and the body's ability to burn fat. The researchers studied eight women in their early twenties. The women intensely cycled for ten sets of four-minutes each; which was then followed by periods of two minutes of rest. In a two-week period, these female participants completed seven of these high-intensity aerobic interval training (HIIT) sessions.
The researchers found that the amount of fat expended in one hour of continuous moderate cycling increased by 36% when compared to the control group (which did not participate in interval training). Overall, the ability of the women's heart and lungs to supply oxygen to their working muscles (what is called cardiovascular fitness) improved by 13%.
Any healthy person can do interval training for improved fitness, health, stamina, and speed. Do to the physical demands of interval training, adequate preparation is necessary. Never go all out when first beginning interval training. Gradually increase performance to prevent injury. Warming up is critical because it gets extra blood into the muscles so they are prepared for the activity.
There is not one generally recommended way to prepare for interval training and to actually do interval training. A good warm-up period is always recommended before doing any exercise. A warm-up period may consist of about five minutes of light jogging or walking with a little extra quickness introduced from time to time. Let the body get accustomed to exercising. Once interval training is started, many exercise experts recommend that the duration of intense activity and moderate activity or rest is varied.
Once interval training is completed, it is a good idea to spend about five minutes cooling down. Light jogging or walking helps the body return to its regular routine. Some stretching exercises can also prevent muscle strain or soreness.
A chronic health condition may prevent one from doing interval training, such as heart disease, respiratory disorder, or cancer. Consult with a medical professional, such as a family doctor, before trying any type of interval training.
A risk of injury (such as with bones, muscles, or tendons) can occur with interval training, especially if one overexerts when first starting the training. Symptoms of overtraining include loss of endurance, strength, and speed; chronic aches and pains; loss of appetite, inability to sleep; overuse injuries such as tendinitis; irritability; irregular resting heart rate, and malaise or a general feeling of fatigue or ill feelings.
In general, the intensity of interval training sessions should be 80-85% of the maximum heart rate. This rate differs from person to person depending on such factors as age, genetics, fitness level, and gender. Exercising over this maximum percentage can be dangerous. It can be difficult to judge this amount without the proper equipment. A heart-rate monitor can provide an accurate way to judge the intensity of the workout with respect to one's specific recommended maximum heart rate. It also provides a much more efficient way to conduct workouts, getting the most out of each workout so one becomes stronger, healthier, and fitter in a shorter period of time. A qualified
personal trainer or exercise physiologist can assist individuals with establishing safe, effective interval sessions according to their personal goals and health history.
The use of interval training has great benefits for maintaining a healthy and physically fit body. It improves the body's aerobic capacity, which means the cardiovascular system will work more efficiently after experiencing interval training over a long period. It also reduces one's risk for many medical disorders such as heart disease, which in the long run improves cardiovascular fitness. A regular exercise program that includes interval training helps to maintain a healthy weight to height ratio, what is called the body mass index (BMI), by raising the body's potential to expend (burn) fat.
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William A. Atkins, BB, BS, MBA