The Workout We Don't Log
Every morning I check multiple numbers before I look at anything else on my calendar: HRV, resting heart rate and how much deep sleep I got. Not because I'm obsessed with data, but because sleep is the one training input we never program directly, and it's usually the one doing the most work!
We build plans around swim sets, bike intervals, and long runs. We rehearse nutrition. We talk about recovery day(s). But the session that determines how well all of that gets absorbed happens after the watch stops recording, in a room we rarely think about as part of the program.
The Stages, Briefly
Sleep isn't one thing. It cycles through stages roughly every 90 minutes, several times a night. Light sleep is the on-ramp: necessary, but not where the payoff is. Deep sleep, also called slow-wave sleep (SWS), is where growth hormone release peaks, where muscle tissue repairs and where the physical cost of training actually gets converted into fitness. REM sleep is different work entirely - it's where the brain consolidates motor learning and processes the accumulated stress of the day. Skimp on either one, and we're not just tired, we're undertrained in a way our training log will never show.
Why It Matters More for Us
Endurance athletes break down more tissue, more often, than the general population. That means the repair window matters more, not less. A recreational athlete who sleeps poorly for a few nights feels groggy. An athlete in mid-season training who sleeps poorly for a few nights is accumulating a debt that shows up as a flat interval, a heavier long run, or a nagging ache that won't resolve. We've talked before about reading training data for warning signs. Well sleep is usually the earliest one, and the most ignored, because it doesn't feel like it's costing us anything until it already has.
What Actually Moves the Needle
Quantity first. Most adults need seven to nine hours, and athletes in heavy training blocks often need the high end of that range, not the low end. And this requirement doesn't change just because the morning session is early.
Quality is where the details live. Temperature matters more than almost anything else! A cool room (or sheets/mattress) helps trigger the core temperature drop that pulls us into deep sleep.
And forget the things that can work against us:
Alcohol will wreck slow-wave sleep even in small amounts, regardless of how relaxed it makes us feel going down.
Late meals compete with recovery processes instead of supporting them.
Anti-inflammatories - if we're managing an injury with these , know that they can suppress the same deep sleep we're relying on to heal.
Consistency beats heroics. One great night after five mediocre ones doesn't erase the debt. A steady, boring sleep schedule - same window, most nights - builds a baseline that a single "recovery nap" can't replace.
We spend a lot of energy optimizing the sessions we can see while doing them. Sleep is the session we can't - no watts, no pace, no RPE giving us real-time feedback. But we do have the ability to record it and learn to create consistent habits that allow us to maximize the benefits from it.
Sleep is still training and, at times, might be the most important session on the calendar (and the only one we always automatically show up for!) We just need to remember to treat it that way.
Gratefully,
Mark
Team MPI
