Endurance Running & Hormones: A Guide for Trail Runners
Endurance Running and Hormones: Maintaining Balance in Trail and Ultra-Trail
Training load, VO₂max, elevation gain: these are all central topics in trail preparation. Yet, a fundamental aspect remains underestimated: the hormonal impact of endurance training.
In both men and women, hormones play a central role in performance, recovery, bone health, vitality, and sports longevity. Understanding these mechanisms allows you to adapt your training for sustainable performance.
Summary
- 3 essential ideas about hormonal balance in endurance
- Scientific insights: endurance, energy, and testosterone
- Practical applications to protect your hormonal health
- Key takeaways
3 Essential Ideas About Hormonal Balance in Endurance
1. Energy Balance Conditions Hormonal Balance
Endurance sports—running, trail, cycling, triathlon—support cardiovascular and metabolic health. They integrate sustainably when they are built on three solid pillars: sufficient energy, consistent recovery, and progression.
When training volume increases, the body needs proportional resources. Adequate energy availability allows the hormonal system to fully perform its adaptive role.
Running a lot becomes beneficial when the body receives what it needs to assimilate the effort.
2. For Men: Understanding EHMC to Better Anticipate It
In some highly trained endurance athletes, the literature describes a condition called Exercise Hypogonadal Male Condition (EHMC).
Scientific data shows that these profiles often exhibit:
- Lower total and bioavailable testosterone (on average 15 to 45%)
- Reduced activity of LH, a key hormone for testicular production
- Higher cortisol, reflecting prolonged physiological stress
These adaptations are sometimes accompanied by persistent fatigue, variations in libido, or slower recovery.
Careful management of energy intake and training load usually allows for maintaining functional hormonal balance.
3. For Women: RED-S as a Global Framework
For female athletes, research today uses the concept of RED-S (Relative Energy Deficiency in Sport), which is broader than the former “athlete's triad.”
RED-S describes a situation where insufficient energy affects multiple systems:
- Menstrual cycle
- Bone health
- Metabolism
- Immune system
- Cardiovascular function
In men, the observed physiological mechanisms follow a very similar logic, even if the markers differ.
Sufficient energy availability supports hormonal health, performance, and the sustainability of the practice.
Scientific Insights: Endurance, Energy, and Testosterone
What the Literature Shows
In his reference review, physiologist Anthony Hackney analyzes several decades of work conducted on high-level runners, cyclists, and triathletes.
His conclusions are clear: the hormonal variations observed in some endurance athletes are primarily explained by the relationship between training load and energy availability, and not by the practice itself.
A transient drop in testosterone remains common in highly trained athletes. It becomes relevant to monitor when it persists over time and is accompanied by clinical signs.
In most situations, adjusting energy intake and modulating the load allows for a return to balance.
Reference:
In Practice: Protecting Your Hormonal Health in Trail Running
- ✅ Eat enough, especially during high-load periods (carbohydrates, fats, proteins)
- ✅ Sleep. Really. Sleep is a major hormonal regulator.
- ✅ Plan breaks and active recovery periods.
- ⚠️ Avoid combining voluntary weight loss + large training blocks.
- ⚠️ Do not pursue an “ideal body composition” as your primary goal.
- 👩🦰 Monitor your menstrual cycle; amenorrhea is never normal.
- 🧪 Don't panic over an isolated blood test without symptoms.
- 👨⚕️ Consult if unexplained fatigue, persistent low libido, performance decline, or menstrual disorders persist.
Key Takeaways
✔️ Endurance supports health when it is part of a global balance.
✔️ Energy availability conditions hormonal adaptation.
✔️ Nutrition and recovery are performance levers in their own right.
✔️ Longevity in trail running relies on consistency, not restriction.
Training is about stimulating. Recovering is about adapting.
— Antoine, Baptiste, and Etienne from TRL