Master the basics of metabolic equivalents and learn to apply them to exercise programs in practical ways.
Nowadays, metabolic equivalents (METs) are commonplace on display panels of treadmills, stair climbers, elliptical trainers and other cardiovascular machines, yet METs are often ignored because exercisers simply don’t know what they are or how to use them. This is unfortunate, because monitoring METs is a great way for personal trainers to measure clients’ fitness levels and see improvements in exercise capacity.
So what is a MET anyway? “MET” is another name for metabolic equivalent; a measure of exercise intensity based on oxygen consumption. More specifically, a single MET is defined as the amount of oxygen a person consumes (or the energy expended) per unit of body weight during 1 minute of rest. It is equal to about 3.5 milliliters (ml) of oxygen consumption per kilogram (kg) of body weight per minute, or 1 kilocalorie (kcal) per kg of body weight per hour (Brooks, Fahey & White 1995).
For example, 1 MET for a 70 kg person (154 pounds) is equal to an oxygen consumption of 245 ml per minute (i.e., 3.5 ml · kg-1 · min-1 x 70 kg), or approximately 70 kcal per hour (i.e., 1 kcal x 70 kg). In other words, if a client weighs 154 pounds, he will burn about 70 calories an hour just sitting around.
In most cases, activities involving larger muscle groups result in more energy expenditure than those using smaller muscles. Also, factors such as skill level, body composition and the environment can influence the accuracy of MET calculations. For practical purposes, however, these factors are usually insignificant, so as a personal trainer you can typically disregard them when it comes to your clients.
If you plan to incorporate METs into exercise program design, it’s important to teach your clients exactly how these measurements work. One of the easiest ways to explain the concept is to use the MET display on the cardio machines. Your clients probably have a preferred mode of cardiovascular exercise for their warm-up, and this is a great time to introduce the concept of a MET, says David Dolana, a certified personal trainer at Bally Total Fitness in Tucson. When displayed on a typical cardiovascular machine, METs are shown as a multiple of resting oxygen consumption (i.e., a multiple of 1 MET).
For example, a MET reading of 5 means your client is consuming five times as much oxygen, or burning five times as many calories, as she would be if she were sitting idle in a chair. “And the great thing about METs is that they can be directly related to your clients’ level of physical exertion—and clients like that,” Dolana says. “If you tell a client she is burning five times as many calories exercising [as she would be] just sitting in a chair, she can relate.”
When using METs as an intensity guide for his clients, Dolana makes sure they understand at what intensity they need to be exercising. As a general rule, 4–6 METs is considered moderate intensity; greater than 10 METs is considered vigorous activity. “I tell my clients to strive for at least 30–45 minutes of moderately intense activity on most days of the week,” Dolana says. “And knowing the range of METs at which they should be exercising makes it easier for them to choose appropriate activities.” Table 1 provides examples of different activities and their energy costs in METs.
The concept of exercise capacity has been around for at least as long as the concept of VO2max, which was developed in the 1920s. The strict definition of exercise capacity is “the extent to which a person can increase exercise intensities and maintain those increased levels” (Brooks, Fahey & White 1995).
It makes sense, then, that the higher the exercise intensity is and the longer a client can maintain that intensity, the greater his exercise capacity is. And although cardiologists and clinicians have been using METs as a measure of exercise capacity for years, only recently have METs received renewed attention in the mainstream fitness community.
As a case in point, in a landmark study of nearly 6,000 asymptomatic women, published in the August 4, 2005, issue of The New England Journal of Medicine (NEJM), exercise capacity—as measured in METs—was used to predict survival in women (Gulati et al. 2005). Results showed that risk of death among women whose exercise capacity was less than 85% of the value predicted for age was twice as high as it was among women whose exercise capacity was at least 85% of the age-predicted value. A prior study in men showed similar, albeit slightly less profound, results (Morris et al. 1993; Myers et al. 2002). For men, research has shown that for every 1 MET increase in exercise capacity, there is a 12% improvement in survival (Myers et al. 2002). To make this information more accessible, the authors of these studies developed a nomogram (Figure 1) that you can use to determine your clients’ exercise capacity relative to their age-predicted values.
For a personal trainer, the nomogram provides very useful information. Dolana is particularly excited about this information because “with this [NEJM] study, I now have a reference to gauge where my clients need to be from an overall health standpoint. And I can use this information to set goals for my clients that I know will make a difference in their lives.” Steve Bell, a certified personal trainer from 24 Hour Fitness in Salt Lake City concurs, saying he doesn’t necessarily use METs now, but will probably start using them as a guide for clients who are overweight or have below-average exercise capacity. “The results of the [NEJM] study are helpful because now I can set very specific goals [with regard to exercise capacity] for my clients,” says Bell.
In personal training, the practical applications of using METs to design exercise programs and measure improvement in fitness are tremendous. Both Dolana and Bell agree that trainers should use METs as a guide to design exercise programs and track clients’ progress.
As a practical example, according to the nomogram shown in Figure 1, a 35-year-old woman should be able to reach about 10.5 METs and a 65-year-old man should be able to reach about 7.5 METs. These values represent the averages for their ages; anything below these levels is associated with greater risk of death.
So how do you translate this information into real life? Bell emphasizes the importance of estimating clients’ maximal exercise capacity. While he understands that performing a VO2max test is usually not practical, submax tests are generally adequate. He typically estimates a client’s exercise capacity on the first visit by tracking perceived exertion level and percent target heart rate while the client is using a preferred cardio machine. From this, Bell says, he can get a pretty good sense of cardiovascular fitness level and properly gauge how to help his new client improve exercise capacity.
With many of Bell’s clients, however, it is not just about training them a couple of times per week in the gym. If clients are generally sedentary or have an obvious need to improve their exercise capacity, he incorporates overall lifestyle changes in addition to personal training sessions. In the case of one particular client, who has below-average exercise capacity, Bell has recommended that she perform 20 squats every 20 minutes throughout her workday—and stand for at least 1 hour, without a break, every day. “These small changes can have profound impacts,” he observes. By combining lifestyle changes with this client’s regular exercise routine, he has already seen significant improvements in her exercise capacity.
Nonetheless, Bell also acknowledges that many of his clients already have adequate exercise capacity but still want to increase their fitness levels. To improve exercise capacity for these clients, Bell typically uses interval training and says he will probably start using METs more often to measure workout intensity. “I like the idea of using METs, because my clients [will then] have a concrete measure that they can translate to almost all of the cardio equipment.”
Dolana also recommends interval training for his clients and says he likes to use a 1:3 training ratio. For example, he will have a client run at 80%–90% of her maximum exercise capacity—as measured in METs—for 30 seconds and then run at 60%–70% of maximum capacity for 90 seconds. If the client is training for a particular sporting event, Dolana will vary the duration of both the training session and the intervals to fit the client’s particular goals. “The most important thing to recognize is that each client is different and has different needs,” he says. “Because of that, exercise programs should be tailored to ensure each client’s success, whether it is measured in METs or not.”