I want to share a real example from a recent day of mine, because it perfectly illustrates something I see all the time – and it’s something that can really throw people off.

My day looked like this:

• • • 1 hour walk
    • 70 minutes of weight training (back + chest)
    • 40 minutes of hard pickleball (not ‘real’ pickleball with four people, but rather my husband and I play singles and he runs my a$$ all over the court – it’s basically doing court sprints!)
    • Walking to and from the gym and pickleball (another 30+ minutes)
    • 22,700+ steps total
    • WHOOP strain score: 15.0

Yup, this was a very active day.

And yet…

👉 WHOOP reported total calories burned for the entire day: 1,949 calories.

At first glance, that number might seem reasonable — until you understand what it’s actually measuring… and what it’s not.

What Fitness Trackers Are Good At (and What They’re Not)

Wearables like WHOOP, Apple Watch, Garmin, etc. are great tools — when used correctly.

They’re excellent for:

• • • tracking trends over time
    • comparing effort day to day
    • monitoring recovery and sleep
    • helping you notice patterns

Where they struggle is accurately estimating total daily calories burned, especially in people who:

• • • have high muscle mass
    • strength train regularly
    • move a lot throughout the day
    • are efficient, well-trained athletes

And that’s exactly where many of my clients fall.

 

Why This Day Almost Certainly Burned More Than 1,949 Calories

Let’s break it down in simple terms.

1. Your body burns calories just to exist

Even lying on the couch all day, your body burns calories to:

• • • keep your organs functioning
    • maintain body temperature
    • support muscle tissue

This is called your BMR (basal metabolic rate). For a woman like myself, with high lean mass (lots of muscle), that baseline burn alone is often 1,400–1,500 calories per day.

See the problem? A total calorie burn of 1949 – estimated 1450 cal BMR = 500 calories.

That means WHOOP’s number would suggest that all my walking, lifting, pickleball, and daily movement I did on this sample day only added a few hundred calories total — which is just non-sensical. It doesn’t line up with basic physiology.  

And we haven’t even factored in thermic effect of food (a whole ‘nother calculation)!

My actual calculated total calorie burn for this day should be about 3000 calories. A thousand calorie difference!

Even if we were to meet these two numbers in the middle (to account for whatever our wearables tell us to account for), that’s still a difference of 500 calories.  A lot.

 

2. Strength training burns calories that trackers don’t “see”

Weight lifting:

• • • doesn’t always keep heart rate high
    • creates metabolic demand inside the muscle
    • continues to burn calories after the workout ends

Trackers rely heavily on heart rate, which means they undercount lifting — sometimes significantly.

 

3. High daily movement adds up (even when it feels “easy”)

22,700 steps is a lot of movement.

But because much of it happens at a moderate pace, your heart rate may not spike dramatically — and trackers discount it.

Your body doesn’t.