Advanced Interval Training
An interval-training workout is one in which you alternate periods of hard work, with periods of easy or recovery work. In my previous post I looked at some of the benefits of interval training such as weight loss, as well as increased strength, speed, and heart rate recovery. The best way for beginners to start interval training is to insert short high-energy bursts into their exercise regime at about five minute intervals. This article will go beyond basics for those of you who want a deeper understanding or who want to train at a higher level. The best way to approach this is to define some terms and explain their relevance to intervals.
Aerobic Exercise – This is exercise done within your own cardiovascular limits. The heart and circulatory system is able to supply enough oxygen to the tissues. If you are in your aerobic zone, you do not run out of breath.
Anaerobic Exercise – When the demands of our muscles outstrip our heart’s ability to supply oxygen, our muscles have to produce energy on an alternate pathway that produces lactic acid. When one muscle group goes anaerobic you will feel the burn of lactic acid, however if the body goes anaerobic you will immediately find yourself out of breath.
Heart Rate (HR) – Heart rate is measured in beats per minute (bpm). Serious exercise or interval training requires that you have objective information to guide your program. The most important piece of information is your heart rate. The best way to watch your heart rate is with a heart rate monitor. These can be purchased upwards from 100 dollars.
Maximum Heart Rate (HRmax) – The most accurate measure of your HRmax is to have a stress test performed. Barring that, you can approximate it by subtracting your age from 220. Our maximum heart rate is considered to be about 220 bpm at birth. It then declines by approximately one bpm per year. So at 50 years old for example, your maximum heart rate would be about 170 beats per minute (220 – 50).
Resting Heart Rate (HRmin) – This is your heart rate with the minimum load placed upon your cardiovascular system. You can obtain this by counting your radial (wrist) or carotid (neck) pulse for a full minute, before you get out of bed in the morning. HRmin is one indicator of relative fitness levels since it decreases as you become more fit.
Training Zone (%max) – This is the heart rate zone that you will train in and it is expressed as a percentage of your maximum heart rate. It is somewhat subjective, but if you are a beginner, start between 50% and 60%. As you become more fit, 60% – 70% is the zone that you will be in to recover between intervals. The area between 70% and 80% is termed the aerobic zone where a fit person can train their cardiovascular system. The Anaerobic Zone, which is where your body can no longer supply enough oxygen to keep pace with the levels of exertion, is from 80% to 90% of your HRmax. This is the zone that you need to enter if you want to do true interval training. Finally there is the red line zone from 90% – 100%. This zone is reserved for high-level interval training. Only the very fit are able to train effectively in this zone.
VO2max – This is a quantitative measurement of fitness levels. Specifically it is the maximum amount of oxygen in millilitres that you can use in one minute, per kilogram of body weight. Those who are more fit have higher VO2 max values, and can exercise more intensely. The ideal way to determine your VO2max is at a sports or medical facility with proper measuring equipment. In the absence of this equipment you can approximate your VO2max with a stopwatch and a friend by one of several methods, using the Cooper or Balke Tests or by using race results. To do this, go to the Sports Coach VO2max web page at: http://www.brianmac.demon.co.uk/vo2max.htm
Karvonen Formula – This is the most popular method of calculating target heart rate training zones. Because your resting heart rate is involved in the calculation, it adjusts for different fitness levels. The formula is as follows.
Target Training Zone = ((HRmax- HRmin) x %max/100)+ HRmin
Let’s say that a fit 40 year old, with a resting hear rate of 65 beats per minute, wants to train at 70 % of her maximum heart rate. Lets fill in the variables: HRmax = 220-40yrs old = 180, HRmin = 65, %max = 70
Plugging these numbers into the formula yields ((180-65) x 70/100) + 65 = 145bpm as her target heart rate for training.
High Intensity Interval Exercise (HIIE) – This is an interval training program containing multiple cycles of high level exertion (80% – 100% HRmax) for short bursts lasting 15 – 60 seconds at a time, followed by either rest or recovery periods. Researchers at the University of Barcelona tested a HIIE programme lasting just two weeks. The programme involved daily training sessions consisting of 15-second “all-out” work periods, followed by 45 seconds of rest. After just two weeks of training, VO2max had improved by an impressive 11% – a change normally associated with programmes lasting far longer. Japan’s National Institute of Fitness and Sport compared two training programmes, the first consisting of traditional moderate intensity exercise (cycling) for 60 minutes, five days a week. The second programme involved HIIE, and consisted of eight “all-out” work bouts lasting 20 seconds, with 10 seconds of rest. Despite the fact that each workout lasted just four minutes, VO2max gains in the HIIE group were 55% greater than those performing the moderate intensity training. Another very interesting fact is that four different studies have found that high-intensity exercise actually suppresses appetite more than lower intensities and tends to reduce peoples’ saturated fat intake.
Post Exercise Caloric Expenditure (PECE) – One of the newer findings from interval studies is in the area of fat burning. Conventional wisdom used to suggest that one should exercise around 60% – 70% HRmax (where you never got out of breath) to burn off fat. It turns out that with interval training, the body continues to burn fat, hours after your session has ended. Research done at the Laval University, as well as Colorado State University show that interval training can rev-up your metabolism quicker than continuous aerobic exercise. Dr. Melby At Colorado U. compared the amount of calories expended in aerobic exercise for of a sixty-minute duration, to interval training for of thirty minutes duration. He found that not only did the interval training burn more calories compared to aerobic training during the workout, but calories continued to be burned as long as 15 hours later as a result of the anaerobic activity during the workout. Another study found that individuals who regularly engaged in high-intensity exercise had lower skin fold thickness and waist-to-hip ratios than individuals who participated in exercise of lower intensities.
How do I begin interval training? – The benefits of interval training are well researched and documented. The most obvious risk is that you are pushing the limits of your cardiovascular system. This is why you should consult your doctor before beginning a high intensity program. If you want to go high-tech, then determine your maximum heart rate and buy a heart rate monitor. If you have never worked out before, then begin with continuous, low to moderate intensity exercise while listening to your body, not your monitor. If you are already training or working out you can begin inserting moderate intensity intervals into your existing routine, using your good sense as a guide. Initially, bring your heart rate down to between 100 and 110 bpm between intervals to be sure that you have recovered from your last interval. Monitor your heart rate during these workouts and see where your comfortable training heart rate lies. If you are a real keener, you can determine your own baseline VO2max with a friend and a stopwatch using the Cooper or Balke test. You can begin by approaching intervals intuitively, but sooner or later you are going to want to get anal . . . oops, I meant organized. One example of a 3-week schedule meant to train you for a competition that would last one hour might go as follows:
Days 1, 3, 5, 8, 10, 12, 15, 17 – Do 8-12 “all-out” sprint intervals lasting 30 seconds, with recovery periods of 4-5 minutes.
Days 2, 9, 16 – Do 45 minutes of continuous exercise at 70-80% maximum heart rate
Days 4, 11, 18 – Do 60 minutes of exercise at 60-70% maximum heart rate
Day 7, 14 – Do 90 minutes of light exercise
Days 6, 13 – Rest days
Hopefully those of us who are not training for a competition are exercising 3 or 4 days per week, which is fine. Just make sure that you get your heart up into your training zone for a minimum of 15 – 20 minutes, then insert a short interval (30-60 seconds) every 4 or 5 minutes. As with any workout, be sure and add a 5-minute warm-up and cool-down to each end of your routine. For more on interval training, simply search the web with any of the phrases used in this article. There is a multitude of guidance, research and routines out there. One particularly good site for explaining all of the terms used in this article is the Sports Coach, located at http://www.brianmac.demon.co.uk/