Sleep & Recovery for Endurance Athletes
Tom Jenkinson
Why the most powerful training tool in your arsenal is the one you’re probably ignoring
I recently received my Coros Year in Review, and one number stood out immediately: an average of 8 hours and 39 minutes of sleep per night over the past year.
When I shared this with my training group after a dark Saturday morning session, the reaction was telling. A few of the others still smelled faintly of chlorine from an early indoor pool workout. There were a few low whistles. Some disbelief.
Out of a dozen dedicated runners, swimmers, and swimrunners, no one else came close. Most were hovering somewhere in the high sixes or low sevens.
And I get it.
In endurance sport, there’s often a quiet badge of honor attached to doing it all on very little rest. The 5:00 a.m. alarm for a pre‑work swim. The long run before the city wakes up. Strength work squeezed into whatever gap remains. We admire the grind.
But sitting there over coffee, it struck me that we often have the problem backwards.
We obsess over carbon plates, pull buoys, paddle size, and wetsuit model; while quietly undercutting all that work by neglecting the one window where we actually get better.
Training Is the Signal. Sleep Is the Adaptation.
This is a truth I regularly remind athletes:
You don’t get fitter during the run.
You don’t get stronger during the swim set.
You don’t adapt while you’re suffering through threshold work.
In those moments, you are breaking things down. Muscle fibers are stressed. Glycogen is depleted. The nervous system is loaded. Training is simply the signal; the message to your body that says, “This version of me isn’t robust enough yet.”
Sleep is when the upgrade happens. If you send a massive training signal but don’t provide enough sleep to support the adaptation, you’re not training. You’re just accumulating fatigue.
“I Function Fine on Six Hours” — A Subtle Trap
I hear this a lot:
“Coach, I’ve always been a low‑sleep person. I function fine on six or seven hours.”
I believe you. Humans are remarkably resilient. We can function under all sorts of sub‑optimal conditions. But there’s a big difference between functioning and thriving as an endurance athlete.
General sleep recommendations, 7 to 8 hours are designed for the average person. If you’re training an hour or more per day, stressing your cardiovascular system, connective tissue, and nervous system, you’re no longer average. Your recovery requirements are higher.
One of the most consistent findings in sports science is that increasing sleep duration reduces injury risk and lowers perceived effort.
On 8.5 hours of sleep, a threshold swim feels like a controlled 6 out of 10.
On 6.5 hours, the same session feels like an 8 out of 10; even at an identical pace.
Sleep doesn’t just help you recover. It makes the work feel easier.
Your Overnight Maintenance Crew
Think of sleep as your body's essential service window:
Tissue Repair: Deep sleep is the primary window for growth hormone release. When sleep is cut short, the window for physical repair narrows.
Refueling: Glycogen restoration accelerates while you sleep. Nutrition provides the raw material, but sleep governs how effectively that fuel is stored for the next day’s work.
Neurological Filing: Endurance training is as much neurological as it is muscular. Coordination, rhythm, and technical efficiency are all brain‑dependent. Sleep is when motor patterns are consolidated. The improvements you chase in the pool are not truly "saved" until you sleep.
Tracking Tools vs. Truth Machines
Most of us now wear something that tracks sleep. Used correctly, these tools are genuinely helpful for pattern recognition. They reliably show:
Consistency of your routine.
Duration trends (up or down).
The impact of lifestyle stressors.
Where these devices fail is the details. Sleep stages (REM vs. Deep) require brain‑wave measurements in a lab. Wrist‑based devices estimate these via movement and heart rate, making them "noisy" day‑to‑day.
Many athletes wake up, see a poor sleep score, and subconsciously decide the day is doomed. Use sleep data as feedback, not judgment. If your resting heart rate is trending up, that’s a coaching signal; not a verdict.
Sleep trackers should help you sleep more — not worry better.
The Anchor Rule
In the middle of a Swedish winter, the lack of daylight can wreak havoc on your internal clock. Your body’s circadian rhythm loves predictability, and the most important part of that rhythm is your wake‑up time.
Think of it as your physiological anchor. Even if you have a late night, try to wake up at the same time the next morning. Consistency at 7:00 AM every day is far more powerful than catching up on weekends and inducing "social jet lag."
A Gentle Challenge
What would change if you aimed for just 30 more minutes of sleep tonight? Not perfection. Not two hours. Just thirty minutes. Move the bedtime up. Close the laptop. Let the adaptation happen.
But sleep doesn’t just dictate how you recover from yesterday's work. In the next post, we’re going to look at the hidden side of the equation: why the exact same session can feel like a breeze or a death march depending entirely on what happened while your eyes were closed. It turns out, sleep isn't just a recovery tool; it's a performance enhancer that changes the very physics of your training. This is what we will look into next week.
This article was written by Tom Jenkinson, read the article on his blog here. Tom also offers UltraSwim 33.3 training programmes.
