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Intensified endurance training increases nocturnal proximal skin temperature and sleep latency in male long-distance runners

Eight days of intensified endurance training (209.2 km vs 118.5 km) significantly elevated maximum nocturnal proximal skin temperature (p=0.045), especially during the first 180 minutes after bedtime (p=0.03), and increased sleep latency (8.4 min vs 2.6 min, p=0.003) compared to normal training. The delta skin temperature during sleep was also higher in the intensified training group (p=0.004).

Last updated: Jul 10, 2026•0 RCTs•📖 Read as article →

Evidence Score

Evidence Score32/100
Human RCT☆☆☆☆☆
Meta-analysis☆☆☆☆☆
Mechanism★★★★★
Safety★★★★☆
Confidencelow

Study Evidence

Study 1. Effects of intensified endurance training on nocturnal skin temperature and sleep variables in male long-distance runners: A pilot study.

observational

Okamoto S, Goto K · Physiological reports (2026)

Participants: N/A
Duration: 8 days
Intervention: Intensified endurance training (8-day program with higher running distance, average 209.2 km over 8 days) compared to normal training (average 118.5 km over 8 days)
Outcome: Nocturnal proximal skin temperature (maximum, delta), sleep latency, sleep efficiency, total sleep time, wake after sleep onset
Effect Size: N/A
Population: Male long-distance runners (14 participants)

Result:

PubMed: 42374861DOI: 10.14814/phy2.70986

Mechanism Graph

Intensified training increases metabolic heat production
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Elevated core and skin temperature persists into the night
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Higher proximal skin temperature delays heat dissipation
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Delayed sleep initiation (increased sleep latency)

Limitations

  • ⚠Small sample size (n=14) limits generalizability
  • ⚠Pilot study design with no blinding or randomization details
  • ⚠Only male runners studied, so findings may not apply to females or other populations

Frequently Asked Questions

Does intensified training affect overall sleep quality?▼

The study found that sleep latency increased, but overall sleep quantity (total sleep time, efficiency) was not substantially impaired.

Why does intensified training increase skin temperature at night?▼

Increased training volume likely elevates metabolic heat production, which persists into the night, raising proximal skin temperature and altering thermoregulatory responses.

How long did the skin temperature elevation last?▼

Maximum skin temperature was significantly higher throughout the night, especially during the first 180 minutes after bedtime.

Is this study applicable to female athletes?▼

No, the study only included male long-distance runners, so results may not generalize to females.

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References

  1. 1.Okamoto S, Goto K. "Effects of intensified endurance training on nocturnal skin temperature and sleep variables in male long-distance runners: A pilot study.." Physiological reports, 2026. PMID: 42374861 DOI: 10.14814/phy2.70986
Disclaimer: This content is for educational purposes only and is not medical advice. Evidence scores reflect the quality and quantity of available research, not clinical recommendations. Always consult a healthcare professional before starting any supplement or intervention.