If you’ve ever sworn that a “runner’s high” or post-workout pain relief is universal, this one’s for you. People respond very differently to the same routine, physically, chemically, and psychologically. In exercise science, this is called inter-individual variability: some folks are robust “responders,” others change a little, and a few don’t change at all (or even feel worse) despite doing the same program. That’s been shown across outcomes like aerobic fitness, blood pressure, and muscle gain.
Take pain relief after exercise, often called exercise-induced hypoalgesia (EIH). In healthy people, a single workout can temporarily raise pain thresholds, which is one reason many feel looser or “better” after moving. But that effect isn’t guaranteed, and it’s frequently blunted or inconsistent in people with chronic pain conditions. Reviews show EIH varies by intensity, body region, and health status; in some chronic pain populations, it can even invert (more pain afterward), especially when dosing is off.
Now consider fibromyalgia, a condition marked by central pain amplification (the nervous system turns up the “gain” on signals). For some with fibromyalgia, certain formats (gentle aerobic work, light resistance, stretching) can improve pain and quality of life over time. But acute responses are sensitive to factors like intensity, rest periods, and belief/expectation; push too hard and you may get a flare instead of relief. Research highlights both the promise of exercise for symptom management and the need for tailored dosing rather than copy-pasting a generic plan.
It’s real for some, but not a rite of passage for all. The euphoric, calm, “floaty” state has long been blamed on endorphins, yet animal and human work points strongly to endocannabinoids (your body’s own cannabis-like compounds) as key drivers. Even then, studies show big variability based on sex, training history, intensity, duration, and environment; plenty of perfectly fit runners have never felt it. In mice, blocking cannabinoid receptors wipes out the high; in humans, evidence is growing but mixed and context-dependent. Translation: if you don’t feel it, you’re not broken, you’re normal.
So why do influencers often insist their experience is universal? It’s compelling (and marketable) to tell a clean story: “I did X, felt Y, so you will too.” But biology is messy. Genes, sleep, stress, pain sensitivity, prior injuries, medication, expectations, and the exact dose (mode, intensity, volume, rest) all shape what you feel during and after a workout. The same interval set that lights someone up can drain another. Reviews in exercise science increasingly argue for adaptive, individualized programming and caution against labeling people “non-responders” without first checking the fit and fidelity of the program.
Bodies are diverse. Good coaching and good self-care honor that diversity instead of denying it.
