Goodhart’s Law in the Gym
We often track progress through numbers . While those numbers can be useful, they can also lead us astray if we’re not careful.
When the Measure Becomes the Target: Understanding Goodhart’s Law in Fitness and Health
In health and fitness, we track progress through numbers — weight, sets, reps, calories, soreness, and more. And while those numbers can be useful, they can also lead us astray if we’re not careful.
This is where Goodhart’s Law comes in:
“When a measure becomes a target, it ceases to be a good measure.”
The idea is simple: once a number becomes the goal, it stops being a reliable reflection of the thing you were trying to improve. You start training the number instead of the outcome.
Here are three common examples from strength training, hypertrophy, and fat loss:
1. Box Jumps and Vertical Jump Training
The original goal: Improve explosive power and vertical jump performance.
The measure: Height of the box you’re jumping onto.
How it backfires:
Athletes start chasing higher boxes to show off or track progress. But instead of improving their vertical leap, they focus on tucking their knees or contorting their body just to land on a taller surface. It becomes about landing ability or mobility — not actual jumping power.
Why it matters:
Once box height becomes the goal, it stops being a reliable measure of athleticism. The movement has been gamed, and you’re no longer training the quality that matters.
2. Chasing Soreness
The original goal: Stimulate muscle growth or performance adaptation through effective training.
The measure: How sore you feel after the workout (DOMS).
How it backfires:
Instead of following a smart, progressive program, lifters chase soreness to “prove” they trained hard enough. This leads to constant exercise switching, excessive volume, or gimmicky intensity techniques — all of which ramp up fatigue but not necessarily results.
How it backfires:
Instead of following a smart, progressive program, lifters chase soreness to “prove” they trained hard enough. This leads to constant exercise switching, excessive volume, or gimmicky intensity techniques — all of which ramp up fatigue but not necessarily results.
Why it matters:
Soreness is not the same as progress. It’s influenced by novelty and eccentric load — not effectiveness. When soreness becomes the goal, people often compromise recovery, reduce performance in subsequent workouts, and miss the bigger picture.
3. Chasing Weight Loss
The original goal: Improve overall health, body composition, and well-being.
The measure: Pounds lost on the scale.
How it backfires:
People start doing whatever it takes to see the number drop — crash diets, skipping meals, extreme cardio, or using quick fixes like sweat suits or water cuts. The focus shifts from building a sustainable routine to manipulating short-term numbers.
Why it matters:
The scale doesn’t reflect muscle gain, water retention, or how you actually feel. When weight loss becomes the only goal, it can lead to unhealthy behaviors, burnout, and rebound weight gain — especially when muscle is lost along the way.
The Takeaway
Goodhart’s Law reminds us not to confuse metrics with goals.
Tracking is helpful — until the metric becomes the obsession. Instead of chasing soreness, volume, or the number on the scale, ask yourself:
“Is this still moving me toward what I really want?”
Progress in fitness isn’t just about bigger numbers — it’s about doing the right work, recovering well, and building something that lasts.