In the Stress + Rest = Growth equation the stress part as far as exercise is concerned is usually more easy to measure. How close did you get to the target pace/weight/intensity/time during the session.
The rest and recovery side is harder to judge as there are fewer external metrics to go on. One of those is how well you perform in the following session, ideally better, indicating that the recovery was sufficient from the previous effort. However, with a really HUGE stress like a race event that goes well beyond the effort of a typical hard workout, how do you know whether or not you’ve recovered?
I think this is always going to be a tricky question to answer as it’s a totally individual thing dependent on lots of factors such as non-exercise stresses, sleep quality, nutrition quality, previous training history. It relies on more subjective, internal indications and on being really honest about those. Not just giving yourself the green light because you want to push on to the next thing!
Some that I noticed in myself over the last week post first trail ultra:
Muscle soreness (although even if that fades quickly it does not necessarily mean full recovery)
Tiredness and fatigue (wanting to fall sleep earlier and for longer; also feeling tired after apparently ‘easy’ activities like a 20 min walk)
Appetite (my appetite tends to regulate to my activity levels fairly well but this week it has been higher than normal for an ‘easy’ week)
Ability to focus and concentrate (being able to do productive work e.g. writing a blog post was not possible for the first half of this week)
Mood (it’s natural to be down after completing a big event but also feeling withdrawn or getting grumpy easily can be a sign of residual fatigue)
Enthusiasm to train again (on Monday I was still high and itching to run again I decided against as I think one mile would have finished me off, by Wednesday after a couple more sleeps a half hour run felt okay)
Recovery from the first session back (compared to how a session like that would normally feel)
All of the above require not just paying close attention to how you are ‘now’ post event but also knowing what your ‘normal’ is. A reflective practice like this ought to be a regular part of your training process and not just after the finish line so that you’re able to judge when things are off and when things are getting back to baseline.
The pay off for taking it cautiously with recovery is being able to come back fitter and stronger for the next round of training so it is worth taking time getting familiar with what your body needs!