METs and the Mets
The Mets, The Kings of Queens, The Orange and Blue, the Grimace Mets, The Other New York Team, and the anthesis of The Bronx Bombers, The Pinstripes, The Bronx Zoo. Other than being athletes, the baseball Mets have little to do with our personal health other than if you are a fan, perhaps they contribute to your wellbeing.
We want to talk about another kind of METs, the metabolic equivalent of task (MET). The academic definition is “the objective measure of the ratio of the rate at which a person expends energy, relative to the mass of that person, while performing some specific physical activity compared to a reference, currently set by convention at an absolute 3.5 mL of oxygen per kg per minute, which is the energy expended when sitting quietly by a reference individual, chosen to be roughly representative of the general population, and thereby suited to epidemiological surveys.” “… sitting quietly by a reference individual” is 1.0 MET. … Have we found a scientific use for a coach potato? Sleeping and meditating are also 1.0 MET. Ainsworth, B., et al., “2011 Compendium of Physical Activities,” Medicine & Science in Sports & Exercise, 43 (8): 1575–81 (2011). https://doi.org/10.1249/mss.0b013e31821ece12
Let’s try a somewhat easier description. You know that your body needs energy to function, 24 hours per day, 7 days per week, twelve months per year, year after year after year. Even when we are asleep our body continues to need and burn energy. A MET is a measure of your body’s expenditure of that energy per minute. The higher the MET of a particular activity, the more energy your body needs to do that activity. You can find a list of MET values for hundreds of activities online at https://pacompendium.com. The activities are described by a five-digit code, the first two digits of which are the base category or activity and the latter three digits the type of activity. For example, activity 17190 is walking (17) at a moderate pace of 2.8 to 3.4 miles per hour (mph) on a level firm surface (190), yields a MET of 3.8. A MET of 3.8 means you are exerting 3.8 times the energy than you would if just sitting quietly. Add a 1 to 5 percent slope, and the MET goes to 5.3; a 6 to 10 percent grade, 7.0. Jogging (12020) and running (12050, a ten-minute mile) are even higher METs, 7.5 and 9.3 respectively.
Walking the dog is 3.0 MET (17165), while carrying a 50-pound suitcase through a level airline terminal is 6.5 MET (17019). Downhill skiing or snowboarding with moderate exertion is 6.3 MET (19160); doing Colbert’s Couloir is 8.0 MET. Of course, these measures apply only when actively moving, not just standing trying to get your heart rate back down after being bitten by a snow snake. I could not find a MET for après ski … does it depend on how often you raise your glass and with how much vigor?
Walking and carrying your golf clubs is 4.3 MET (15265), pulling your clubs is 4.5 MET (15285), but using a cart is down to 3.5 MET (15290). Cooking is 2.5 MET (11115) and serious baking is 4.0 MET (11010). Writing this post is 1.3 MET (11770). Go to the Website and look up your activities. Yes, there is a separate category for sex; sorry, you will just have to look that up yourself.
Understand that MET scores are empirically based on consuming 3.5 milliliters of oxygen per kilogram (kg) of body weight per minute. On an individual basis, many factors influence the rate of energy use, including age, gender, body weight, body composition, resting metabolic rate, cardiorespiratory fitness level (CRF), and genetic traits. While acknowledging the individual variability, METs do provide a standardize basis for comparing human activities. Franklin, B., et al., “Using Metabolic Equivalents in Clinical Practice,” Am J Cardio 121(3):382-387 (Feb 1, 2018). https://doi.org/10.1016/j.amjcard.2017.10.033
Now we know what MET scores are, for what are they used? We all know we should exercise, and there are accepted (by some? by most?) guidelines. Let’s start with the US Government. The US Department of Health and Human Servies (HHS) issues its Physical Activity Guidelines, that are “based on current scientific evidence supporting connections between physical activity, overall health and well-being, disease prevention and quality of life.” The second edition of the Guidelines was issued in 2018. There are guidelines for preschool-aged children (3-5 years), children and adolescents (6-17 years), adults and older adults.
“For substantial health benefits, adults should do at least 150 minutes (2 hours and 30 minutes) to 300 minutes (5 hours) a week of moderate-intensity, or 75 minutes (1 hour and 15 minutes) to 150 minutes (2 hours and 30 minutes) a week of vigorous-intensity aerobic physical activity, or an equivalent combination of moderate- and vigorous-intensity aerobic activity. Preferably, aerobic activity should be spread throughout the week.
Additional health benefits are gained by engaging in physical activity beyond the equivalent of 300 minutes (5 hours) of moderate-intensity physical activity a week.
Adults should also do muscle-strengthening activities of moderate or greater
intensity and that involve all major muscle groups on 2 or more days a week, as these activities provide additional health benefits.” US Department of Health and Human Servies Physical Activity Guidelines. https://odphp.health.gov/our-work/nutrition-physical-activity/physical-activity-guidelines/current-guidelines
Older adults should back off these guidelines as appropriate for their age and overall physical and health conditions. Leal-Martín, J., et al., “Metabolic equivalents intensity thresholds for physical activity classification in older adults,” Eur Rev Aging Phys Act 21(1):14 (May 21, 2024). https://doi.org/10.1186/s11556-024-00348-5
Sounds good, sort of. First, we have to define “moderate-intensity” and “vigorous intensity.” As you can easily imagine, these definitions depend upon who you ask. We can get some help by referring back to METs. Byrne, N., et al., “Metabolic equivalent: one size does not fit all,” J Appl Physiol 99(3):1112-9 (Sep 2005). https://doi.org/10.1152/japplphysiol.00023.2004
A MET score of 1 to 4 is considered low intensity and is not considered to improve cardiovascular fitness in most people (although, you start where you start). MET scores of 5 to 8 and are considered moderate and an appropriate starting point for sedentary and older adults. A MET score over 8 is considered high intensity and best for improving fitness. See, Cristi-Montero, C., “Considerations regarding the use of metabolic equivalents when prescribing exercise for health: preventive medicine in practice,” The Physician and Sportsmedicine, 44(2), 109–111 (2016). https://doi.org/10.1080/00913847.2016.1158624
Another group of researchers score less than 3 METs as “light,” 3 to 6 METs as “moderate,” and more than 6 METs as “vigorous.” Jetté, M., K. Sidney, & G. Blümchen, G., “Metabolic equivalents (METS) in exercise testing, exercise prescription, and evaluation of functional capacity,” Clin Cardiol 13(8): 555-565 (1990). https://doi.org/10.1002/clc.4960130809
The guidelines and the definitions are imprecise. Can we generate more clarity?
An expert panel convened by the American College of Sports Medicine (ACSM) and the American Heart Association (AHA) recommended healthy adults expend from 450 to 750 MET-minutes per week. Crawford-Faucher, A. “Physical Activity Recommendations for Healthy Adults,” Am Fam Physician 77(4):513 (Feb 15, 2008). The Kenneth H. Cooper Institute at the Texas Tech University Health Sciences Center recommends 500 to 1,000 MET-minutes per week for significant health benefits. Farrell, S., “Using MET-Minutes to Track Volume of Physical Activity,” Blog Post, Kenneth H. Cooper Institute Texas Tech University Health Resources Center (Dec 7, 2017). https://www.cooperinstitute.org/blog/using-met-minutes-to-track-volume-of-physical-activity
Both of these recommendations are focused on health and longevity benefits. If your objective is weight loss, the required MET-minute levels are higher.
How does the concept of MET-minutes correlate with other exercise recommendations. You will recall the 10,000 steps recommendation. You can read how this 10,000 step recommendation came to be in my Substack post on June 28, 2023, “How many steps does it take?” Research demonstrated health benefits starting about 4,000 steps. See my “Steps update,” August 24, 2023. An average walking pace is 3 mph, which is 3.8 MET. At this pace, 10,000 steps would take just under an hour. Thus, 10,000 steps would be about 200 MET-minutes. Correspondingly, 4,000 steps would be about 85 MET-minutes. Looks like you have to step it up beyond just walking.
Our society is calorie obsessed, so how many calories do you burn meeting the weekly MET-minute recommendations? First, you have to know your body weight in kilograms (kg). Divide your body weight by 2.2 to covert from pounds to kilograms (or just change the display on your scale). Multiply your activity MET by 3.5 and then by your body weight in kg. Divide the result by 200 to determine your calories burned per minute. A 160-pound person walking at 3 mph burns just under 5 calories per minute. Thus, walking 10,000 steps burns just under 300 calories; 4,000 steps about 120 calories. A 100-pound person walking at 3 mph burns about 3 calories per minute. Thus, 10,000 steps would be about 170 calories and 4,000 steps about 70 calories.
It is the familiar story, get off the couch. You have lots of options.
Remember strength exercises also generate METs. Again, lots of options.
I talked to the manager of a pulmonary rehabilitation program aimed at people with impaired pulmonary capacity, such as emphysema, chronic obstructive pulmonary disease (COPD), interstitial lung disease (ILD), asthma, and the like. As we age our pulmonary capacity naturally decreases. The pulmonary rehab program is designed to slow the age-related degradation, to increase degraded capacity, and enhance overall lung function. The rehab program threshold objective is to reach a minimum of 4 METs. MET 4 is the threshold above which cardiac and pulmonary benefits are experienced. Of course, the higher the better. The program accepts people as they are and is individually designed to help them better their lung function. METs are the quantitative and quality measures of enhancement.
A typical protocol in this program is 5 minutes on a treadmill at a moderate pace, less than 3 MET, followed by 15 minutes on the treadmill at a higher pace or increased incline, over 4 MET. The next 15 minutes use machines that engage more of the body than just walking, with an over 4 MET objective. The final 10 minutes are devoted to balance and strength exercises. Each person’s blood pressure, pulse and SO2 are recorded before commencing the exercises, and again upon completion. Pulse and SO2 are measured during each 15-minute session. Exercise and breathing effort are queried subjectively.
It matters not the measure or measures you choose to use; it matters not your age. METs enable exercise effort measures across activities, and are valuable to researchers and practitioners alike. Should you like, you can use them to design your own exercise program (a great way to avoid exercise boredom). The watchword is to get off the couch, MET 1.0 and get above MET 4. And it is truly best to get outside; spring, summer, fall and winter.
