How sleep changes the "operating system" and physics of your training tomorrow
If Part 1 was about the "Maintenance Crew" fixing the damage from today, Part 2 is about the "Operating System" you run on tomorrow. Most athletes treat sleep as a passive bank account; in reality, it is an active performance variable that shifts the goalposts of your fitness.
Most athletes understand that sleep helps recovery. What’s less understood is that sleep directly changes how training feels; how accurately you pace and how well you access your fitness under load.
Perceived Effort Is Not Fixed
Perceived exertion (RPE) is often treated as purely subjective, but research shows sleep loss increases RPE at any given workload.
Same pace. Same power. Higher effort. The body works harder to produce the same output when restricted. This is why threshold work "drifts" and why endurance days feel heavier than they should.
Neurological Pacing
Pacing is a cognitive skill. It relies on internal feedback and decision‑making. Sleep loss degrades both. Athletes short on sleep are more likely to start too fast or abandon pacing plans mid‑session. This is not a willpower issue; your brain simply loses the ability to fine‑tune the engine when the battery is low.
The Cellular Energy Factor: Creatine and Sleep
Emerging research suggests that sleep quality isn't just about "lifestyle"; it's about cellular energy. During hard training, your cells burn through ATP faster than it can be rebuilt. When reserves are depleted, energy sensors flag a crisis, keeping the sympathetic nervous system firing. This is the biological signature of being “tired but wired.”
A 2024 study showed that athletes (specifically women) taking 5g of creatine daily slept 48 minutes longer on training nights than those on a placebo. By buffering cellular energy stores, creatine may help switch off that "crisis" signal, allowing the body to transition into deep sleep more effectively.
The "Mystery" Niggles
The link between short sleep and injury risk is undeniable. Athletes sleeping under 7 hours are significantly more likely to develop overuse injuries. Sleep loss impairs tendon repair and makes movement subtly less precise. Small errors accumulate until something hurts "out of nowhere."
Durability as You Age
As we move into our 40s and beyond, recovery margins narrow. Connective tissue remodels more slowly. Sleep becomes your cheapest and most effective durability tool.
A Simple Framework to Take Away
If 6:30 is your current wake‑up time, aim for 7 hours first. When that sticks, add 15 minutes. Small gains compound.
Core Principles:
Environment: The bedroom is for sleep. No scrolling.
Caffeine: Cut it 6 hours before bed. It lingers longer than you think.
The Brain Dump: If your mind races, write tomorrow’s to‑do list before bed to "unload" the stress.
Morning Light: Even in a Swedish winter, get outside for your morning coffee. It’s the strongest circadian signal we have.
Creatine Buffer: Consider 5g of creatine monohydrate daily. It helps buffer cellular energy, potentially silencing the "tired but wired" signal on hard training days.
Downshift: If you train late, use a warm shower and slow breathing to signal to your nervous system that the session is over.
The "Pinot" Clause: Enjoy a good glass of wine if you like; just don’t pretend the science backs the recovery benefit.
The Takeaway
Hard training feels easier not because you’re tougher; but because your system is prepared to absorb the work.
Consistency beats perfection. Sleep makes consistency possible.
A Note on Women and Sleep
After the last newsletter, several women replied with something like “Sleep more… easy for you to say.” That is fair. Women are more prone to sleep disruption, not because of life load, but because of specific physiological shifts.
Progesterone has a calming effect on the brain. It enhances GABA signalling, which supports sleep onset. At the same time, progesterone raises core body temperature by around 0.3–0.5°C in the luteal phase. For some women, particularly during perimenopause when hormones fluctuate unpredictably, this can make sleep feel lighter or more fragmented.
Iron deficiency, common in women, can also impair sleep quality even when haemoglobin levels appear “normal”.
And if you are under-fuelling your training, low energy availability can increase evening cortisol and sympathetic activation, both associated with poorer sleep. In endurance sport, this sits on the same spectrum as Relative Energy Deficiency in Sport, where disrupted sleep is often an early signal rather than a late one.
So sometimes the issue is not just better habits. It is biology. The practical step — If sleep is consistently poor:
Track it alongside your menstrual phase.
Check ferritin, not just haemoglobin (many sports physicians prefer levels above ~50 ng/mL in active women).
Review fuelling: ensure energy intake matches training load.
Magnesium bisglycinate may help some individuals.
Speak to a GP or gynaecologist if patterns persist, ideally someone familiar with active women/endurance athletes.
As coaches, we adjust training when data changes. Sleep deserves the same respect.
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