Some days you wake up and you feel “ok, today it’s not my day”. Then you know what to expect, you can be a little bit more kind to yourself today, and take it easy. That’s expectable, and at least lets you the consolation of knowing yourself.
But other days your body decides to lie to you. You wake up with a good feeling – no special soreness or fatigue, prepare to train – and BANG. You miss the target greatly, not even close.
I have been measuring my HRV daily, first thing in the morning when I wake up. It helps me detect when my body or my feelings are lying to me – if the HRV is high, it already puts me in guard of something that might be going on.
Could be a cold starting, just some bad sleep, accumulated stress of the previous days – but at least I am aware of not being 100% of top, and I can justify being more kind to myself and not get too frustrated when the session doesn’t go as planned.

Today was one of those days. But the nice thing of triathlon training is that there are so many chances to redeem the bad day!
References:
- I use HRV4Training to measure and analyze my HRV.
I log it synced to TrainingPeaks, and can see the correlation of my low/high HRV values with good or bad trainings, and with the amount of sleep, its (subjective) quality, and if I drank or not alcohol the previous day. - HRV for Triathletes in Scientific Triathlon.
- Interview to Marco Altini from HR4Training in Scientific Triathlon. After this I decided I wanted to log raw values instead of the “stress” measure from Garmin.
- I use the HRM-Tri strap from Garmin to measure the HRV (but I also use it for cycling, swimming and running).