Why your best session leads to your worst night?

4 minute read

You finish a 90-minute session. Heart rate drops. You shower, eat, stretch. Two hours later you're in bed and you can't fall asleep, or you fall asleep fast because you're wrecked and wake at 2am soaked in sweat, sheets stuck to your skin, core still radiating heat from training.

For an athlete with a fixed morning schedule, the practical consequence of delayed sleep onset is compressed total sleep.

Sleep onset requires your core temperature to drop by 0.5 to 1°C. The first bout of deep sleep (where physical repair begins) is most likely to start when the rate of that temperature decline is at its steepest (Harding et al., Frontiers in Neuroscience, 2019).

Intense exercise raises core temperature by 1.5 to 2.5°C, and that elevation can persist for 30 to 90 minutes after you stop (Gilbert et al., Sleep Medicine Reviews, 2004). If you train in the evening, your body temperature peaks right when you need it to fall.

Your bedding controls the microclimate between your skin and the air for the next 7 to 9 hours. It's either helping that cooling process or fighting it.

The price of a bad night.

The research on this is consistent and extensive.

Hormonal disruption. Sleep under 7 hours increases circulating cortisol and reduces testosterone and growth hormone, the two primary anabolic hormones responsible for muscle repair and adaptation (Kaczmarek et al., Journal of Clinical Medicine, 2025). Elevated cortisol drives muscle protein breakdown and impairs glycogen repletion. The session that was supposed to make you stronger creates a catabolic environment instead.

Impaired muscle repair. Muscle tissue rebuilds predominantly during deep sleep. Reduced time in N3 means the adaptation from training doesn't complete. You didn't get fitter during the workout. You got fitter during recovery.

Increased injury risk. A prospective study of roughly 600 student-athletes found those sleeping 5.8 hours or less were nearly twice as likely to sustain a sport-related injury compared to those sleeping over 7 hours: 15.7% incidence versus 8.8% (Rygielski et al., Quality in Sport, 2024).

Performance decline. Maximum work rate dropped by 15 watts after a single night of 4-hour sleep restriction in cyclists (Mougin et al., 2001). Perceived exertion increases too, meaning the same effort feels harder, which leads to either underperformance or overtraining to compensate.

You track everything except...

Athletes optimise nutrition timing, supplementation, compression, foam rolling, cold exposure, sleep schedules, room temperature, blue light. Most of these target either the pre-sleep window or the immediate post-workout period.

Bedding operates continuously across the entire recovery period, and it directly controls the temperature and humidity layer against your skin, which is what determines whether you stay asleep or wake up.

A 2024 study in Scientific Reports (Nature) found that enhanced body cooling during sleep increased slow-wave sleep by 7.5 minutes per night and decreased heart rate by 2.36 bpm (Kräuchi et al., 2024). The mechanism: bedding that helps dissipate body heat supports the core temperature decline that both initiates and maintains deep sleep.

The sleep microclimate should stay between 31 and 35°C with humidity below 60%. Too warm, too humid, or too variable, and your body interrupts sleep to thermoregulate instead of repair.

How common duvet materials handle a post-training night

Polyester absorbs 0.4% of its weight in moisture. Your body loses roughly 200 to 500ml of perspiration per night (more after hard training). Polyester can't take that moisture into its fibre structure, so it pools in the spaces between fibres, creating a humid layer against your skin. You overheat, sweat more, the moisture has nowhere to go, and you wake up. That cycle can repeat multiple times per night. Polyester also permanently accumulates odour because bacteria colonise those damp spaces.

Down performs well in cold, dry conditions. The problem for athletes: when damp from perspiration, down clusters clump and lose insulating properties entirely, requiring 2 to 3 hours in a commercial dryer to recover. Over a hard training week, performance degrades exactly when you need recovery most.

Sheep wool absorbs 30 to 35% of its weight, which is genuinely good. The Bangor University/IWTO study (2024-2025) found wool transmitted 67% more moisture than down and 43% more than polyester in full-sized duvet testing. But that high absorption capacity means wool holds more moisture, takes longer to dry, and can feel heavier by morning. Wool also contains 10 to 15% lanolin, which triggers reactions in 1 to 2% of the population (higher among athletes with skin compromised by frequent washing, chlorine, or friction).

Alpaca solves three problems that matter specifically after training.

The first is heat dissipation. Your core temperature is elevated 1.5 to 2.5°C. You need a material that lets excess heat escape without stripping insulation entirely, because four hours from now, at your circadian low point around 3 to 4am, you'll need warmth again. Alpaca's semi-hollow fibre structure does both. Air pockets inside each fibre release trapped heat when your body is warm and retain it when your body cools. Yocum-McCall Laboratory testing measured a 28°C comfort range for alpaca, compared to 17°C for sheep wool: 67% more adaptability across the night, not just at one temperature.

The second is moisture. You're perspiring more than usual, and that sweat needs to leave the microclimate against your skin, not sit in it. Alpaca absorbs 10 to 11% of its weight in moisture (27 times more than polyester's 0.4%), enough to pull sweat away from skin, but not so much that the fibre itself gets damp or heavy. The moisture moves to the fibre surface and evaporates. Your microclimate stays in the 31 to 35°C, sub-60% humidity range where deep sleep is sustained.

The third is durability across a training week. Athletes sweat more, wash bedding more, and need materials that don't degrade from repeated moisture exposure. In ASTM E2149-13a antimicrobial testing, alpaca fibre reduced bacterial load by 65 to 79% after one hour of exposure. The duvet doesn't become a bacterial habitat.  Alpaca also contains 0 to 3% lanolin (effectively zero after processing), which means no chemical treatments are needed and no risk of the skin irritation, especially on skin already sensitised by friction, chlorine, or frequent showering.

What we can't claim: No peer-reviewed sleep studies exist specifically for alpaca fibre bedding. The University of Sydney conducted polysomnography studies on wool sleepwear showing a 54% reduction in sleep onset latency in older adults (12.4 minutes versus 26.7 minutes with cotton, p=0.001). Alpaca's superior moisture properties suggest comparable or greater benefits, but the clinical validation specific to alpaca hasn't been done yet. We won't claim evidence we don't have.

What Ida Mathilde experiences

"It helps me with the heat after hard sessions."

Ida Mathilde Steensgaard is a Red Bull-sponsored OCR World Champion. Her training combines endurance running, explosive strength, grip work, and carries, often in the evening. Post-session, her core temperature is elevated and her body needs to cool before sleep can begin.

The alpaca duvet creates conditions where her body can cool itself efficiently, wicking perspiration away from her skin while maintaining enough insulation to prevent the overcooling that would fragment sleep later in the night.

Quick reference

Sources

1. Harding et al. (2019). "The Temperature Dependence of Sleep." Frontiers in Neuroscience, 13, 336.
2. Gilbert et al. (2004). "Thermoregulation as a sleep signalling system." Sleep Medicine Reviews, 8(2), 81-93.
3. Kaczmarek et al. (2025). "Sleep and Athletic Performance." Journal of Clinical Medicine, 14(21), 7606.
4. Rygielski et al. (2024). "The Impact of Sleep on Athletes Performance and Injury Risk." Quality in Sport, 19, 54333.
5. Mougin et al. (2001). Sleep restriction effects on cycling performance. European Journal of Applied Physiology.
6. Kräuchi et al. (2024). "Enhanced conductive body heat loss during sleep increases slow-wave sleep." Scientific Reports (Nature).
7. Bangor University / IWTO / British Wool (2024-2025). Duvet moisture transmission and thermal performance study.
8. ASTM E2149-13a antimicrobial testing: Huacaya and Suri alpaca fibre bacterial reduction.
9. Shin et al. (2016), Chow et al. (2019). University of Sydney polysomnography studies on wool sleepwear.
10. Yocum-McCall Laboratory. Alpaca thermal comfort range testing (ASTM F1868).