The Pacing Threshold Problem in Long COVID

When "safe" heart rate zones aren't safe

Last week I reviewed a research study published in February 2026 that reported their findings from a 6-month trial comparing the use of wearable activity trackers versus a pacing app. The researchers were hoping to prove that people who received real-time alerts as they were approaching their exertion threshold would have a greater reduction in post-exertional malaise. To their surprise they found no statistical difference between groups, which means that both groups improved. Neither one or the other was superior. Therefore, the real winner of the study was structured pacing, and not so much real-time alerts. Here’s the thing, there was one limitation to the study that the authors didn’t identify, and it may be the most important one. The pacing framework in the study allowed participants to spend up to 30 minutes per day above 60% of their age-predicted maximum heart rate. This sounds reasonable, but it isn’t for this population. The exertion thresholds were set too high, and in today’s deep-dive, we’re going to talk about why this is a problem. The real issue isn’t wearables. It isn’t the alerts. It isn’t even the pacing apps. It’s the physiology behind setting the appropriate threshold.