HealthFit

First, I wanted to say thank you for building HealthFit. I’ve tried Apple Fitness, Apple Health, Garmin Connect, Strava, and several other fitness apps over the years, and HealthFit is easily my favorite. In my opinion, it’s better than anything Apple has produced for serious athletes. What I appreciate most is that it presents training data in a way that’s actually useful. Metrics like CTL, ATL, TSB, aerobic decoupling, training load, and heart rate analysis are incredibly valuable and much easier to interpret than Apple’s own ecosystem. I also really appreciate the export feature. I regularly export my workouts and analyze them with ChatGPT, which has essentially become my endurance coach. The combination of HealthFit’s detailed metrics and ChatGPT’s analysis has been fantastic for tracking my progress toward a half marathon and sprint triathlon. I do have one question regarding CTL. My understanding is that CTL is based on a 42-day exponentially weighted moving average (EWMA) of training load, similar to the Performance Management Chart used in TrainingPeaks. Because it’s a rolling average with a 42-day time constant, I wouldn’t expect it to increase dramatically in a single day. However, I noticed what appears to be my CTL increasing from 69 to 77 in one day, which doesn’t seem mathematically possible if CTL is indeed using a 42-day EWMA. Could you please confirm: * Is HealthFit’s CTL based on a 42-day exponentially weighted moving average? * If so, could you share the exact calculation or formula you use? * Is there any scenario where an apparent jump like 69 → 77 in a single day could occur (for example, a recalculation, data synchronization, or historical workout import)? Based on the formula published on your website (CTL_today = TRIMP × λ + (1 − λ) × CTL_yesterday, with λ = 2/43), I wouldn’t expect CTL to increase from 69 to 77 from a single workout. Can you help me understand how HealthFit arrived at that value? Was the metric recalculated from historical data, or is there another factor involved? I’m mainly trying to understand whether I’m misinterpreting the metric or whether something unusual happened with my data. Thanks again for creating such an outstanding app. It’s become one of the few fitness apps I use every single day.

I had an issue with training load no longer working after a recent release. The developer was very responsive to my outreach and was able to resolve my issue. For those who might also be experiencing this: IF you suddenly see no training load calcs, check that your resting heart rate is syncing correctly to your profile. Mine was not and this was the issue.