Fitness isn’t a one-size-fits-all pursuit, yet so many of us approach it that way. We follow generic training plans, rely on wearable-tech estimates, and end up frustrated when we don’t reach our goals. But what if you could ditch the guesswork by better understanding your body’s unique blueprint, enabling you to work smarter, not harder?
“If you’re going to invest several hours a week doing something, it’s probably worth spending a little bit of time, money, and energy at the beginning to ensure you’re getting the most out of that time,” says master trainer Danny King, director of performance and recovery at Life Time.
An Active Metabolic Assessment is a test offered at Life Time that calculates an individual’s VO2 max, specific heart-rate zones, and other fitness metrics, allowing for tailored workouts and more intentional results.
We asked King about this assessment and how the data can lead to a more efficient and effective training plan.
What is an Active Metabolic Assessment?
The Active Metabolic Assessment is a test performed on a piece of cardio equipment — typically a treadmill — at Life Time under the guidance of a Dynamic Personal Trainer. It measures exactly how much oxygen you consume and how much carbon dioxide you expire as you exercise at varying intensities. This data reveals your individual heart-rate zones as well as other insights, including your aerobic base, anaerobic threshold, and VO2 max.
During the test, you’ll wear a cordless silicone mask that’s connected to an iPad via Bluetooth. You’ll hop on a treadmill and a Dynamic Personal Trainer will lead you through the assessment, starting with a warm-up and progressing to your peak intensity. During this time, the trainer will monitor your exercise metabolism, or how many calories you’re burning and the ratio of carbohydrate-to-fat burn.
“What we’re doing with this test is putting a mask on you and measuring what’s called gas exchange — oxygen coming in, carbon dioxide going out,” says King. “This can be measured in one of two ways: at rest, which would measure your resting metabolic rate, or more commonly, through exercise, which measures your active metabolic rate.”
The test typically takes 10 to 20 minutes. “If we go too fast through it, we won’t get a good picture of your fuel use or of your zones,” explains King. “If the test goes longer than 20 minutes, we start running into fatigue, which affects results. Therefore, to ensure accuracy, we increase intensity about every two minutes to hit this time range that’s going to get us the best results.”
What information does the Active Metabolic Assessment provide?
Metabolic testing helps us understand how our individual bodies use different fuel sources and at what intensities.
“When you exercise, the two primary fuel sources you’re going to use are either fat or carbohydrates,” says King. “Fat is a slow-burning fuel source, so when we’re at rest, that’s primarily what we’re using. Carbohydrates are a fast-burning fuel source, so as our exercise intensity increases, the amount of fuel that has to come from carbohydrates has to also increase.”
Neither fuel source is considered good or bad, according to King, as there are times when you’ll want to use each of them. That being said, these fuel sources have distinct impacts on the body. That’s why it’s helpful to know at what intensities your body burns each one.
An Active Metabolic Assessment will also provide you with your personal heart-rate zones. “Knowing these allows us to customize your fitness efforts, specifically when it comes to cardiovascular exercise, in a way that allows you to get the most out of it,” says King.
You’ll also learn your VO2 max, a marker of cardiovascular capacity. “There’s a lot of wearable technology that provides an estimated VO2 max,” says King. “However, it’s not going to be as accurate as the score you get from the Active Metabolic Assessment.”
How are the different heart-rate zones outlined?
It’s helpful to understand how training zones work in order to appreciate the value of testing to determine them.
Zone 1: Zone 1 is a very easy intensity level. Moving in this zone feels like something you could do for hours, such as going for a long, leisurely walk. This zone is valuable for supporting recovery and is an important part of general health.
Aerobic Base: The point between zone 1 and zone 2 is called your aerobic base. It’s calculated as the intensity at which you burn fat most efficiently.
One of the major goals of a heart-rate training program is to increase your aerobic base. As it increases, you have to work harder to maintain the same heart rate.
If you work harder while still burning a maximal level of fat, you burn more total calories and use more stored fat.
Zone 2: In zone 2, your breathing gets a little heavier. You’re still able to carry on a conversation with someone, pausing to catch your breath now and then. You’ll likely start sweating soon after reaching this zone.
Zone 3: In zone 3, you’ll notice that you need to breathe through your mouth. You’ll also begin to feel a little less comfortable.
Anaerobic Threshold (AT): The point at which your fat-burning drops dramatically and your body relies much more on carbohydrates is called your anaerobic threshold. People rarely exercise for extended periods of time above this point.
In fact, your body would be limited in how long it could function above this line — but that doesn’t mean there isn’t value in occasionally crossing it.
By spending part of your cardiovascular training time above threshold, you’ll notice that your recovery time between resistance training sets improves as well.
Zone 4: Zone 4 is used for shorter periods of time, like minutes, for the purpose of increasing VO2 max. It may also be used to increase running or cycling speed.
Zone 5: Zone 5 can only be sustained briefly, often less than a minute. Getting to this heart rate requires all-out sprints, Tabata–style cardio, or very high-repetition resistance training sets.
How do you use the information to inform a training plan?
How you use this information depends on your goals.
If your goal is fat loss, for instance, King recommends you spend the majority of your cardio in zone 1 and zone 2 where you’ll burn more fat as your fuel source, with brief intervals into zones 4 and 5. Those striving for muscle gain can use the data to understand how much cardiovascular exercise to do before it starts to hinder your ability to build muscle. Or if you’re looking to build endurance, understanding your heart-rate zones allows you to train at the appropriate intensities to optimize aerobic capacity and avoid overtraining.
“In general, the data you gather from the test will inform the types of workouts you want to do, depending on the outcomes you’re hoping to see,” explains King. “There are many ways to customize your approach, depending on what those outcomes are. And if you could use assistance putting together your plan based on your results, a Dynamic Personal Trainer can absolutely help you do that.”
If you have an Apple Watch and the Life Time app, this integration becomes even more seamless. After taking an Active Metabolic Assessment, your trainer can load your results into your profile in the Life Time app. If your Apple Watch has all things “allowed” with the Life Time app, those numbers are then automatically updated and integrated into the watch. If you start a workout in the Life Time app or when taking an Alpha or GTX class, your Apple Watch will automatically activate and start tracking your heart rate.
Is this test different from the one previously offered at Life Time?
The new Active Metabolic Assessment is very similar to the test that has long been offered at Life Time, though the mask you wear during the test has been improved. The new silicone mask provides the wearer with more space for air. “This allows for a better breathing pattern for the participant and, because it’s easier to breathe through your nose, it’s overall a more comfortable experience,” says King. “And it’s also easier to push to your max, which provides us with more accurate results.”
The mask is also now wireless (connected via Bluetooth) rather than connected via cords, which makes for a more natural running experience during the assessment.
Who is this test for?
This test is for everyone, says King.
Although it’s commonly assumed that the assessment is designed for elite athletes, it may actually be most useful for everyday exercisers, he notes. The less experienced you are with fitness, the harder it may be to know what a specific heart-rate zone should feel like.
What can be expected from the testing experience?
Before the assessment starts, you’ll be asked for your age and have your weight measured. You’ll also be asked about your current fitness level. Because the ideal test takes about 10 to 20 minutes, it’s best to start at a pace that’s not too slow or too fast.
You will be given a heart-rate monitor to strap around your chest, and the trainer will help adjust a silicone mask, so it fits snugly on your face and around your head. Talking is difficult once you’re wearing the mask, so if you ever need to stop during the assessment, you can step on the sides of the treadmill. To communicate with your trainer, you’ll use your fingers to indicate how you feel.
Your trainer will set the treadmill to a pace to begin the warm-up. They will gradually increase the pace throughout the test, each time checking with you to see how you’re feeling. The test ends once you’ve reached your max pace. After you complete your cool-down, you’ll remove the mask and heart-rate monitor and discuss your results with your trainer.
How often is it recommended to do an Active Metabolic Assessment?
Heart rate zones do change over time. For optimal progress, King recommends retesting about every three months or, at minimum, every six months — especially if you make a big change in your training regimen.
“Elite athletes can probably get away with less frequent testing because, the fitter you are, the slower change takes place,” he explains. “However, the newer-to-fitness member we’d want to retest a little more frequently.” To plan for this, it’s helpful to book quarterly or twice-yearly tests for the first year or two of a new or renewed training approach.
How do you sign up for an Active Metabolic Assessment?
Talk with a Dynamic Personal Trainer at your Life Time athletic country club. They’re available to discuss your fitness goals and schedule the test. Or, you can book in the Life Time app.
