Earlier this year, Dr Kenna Stephenson explored why bone health is not just an issue for later life, and why building muscle, strength and confidence of movement should be part of a lifelong strategy for reducing fracture risk.
In this follow-up, certified endurance and ultra-running coach Mario Buchs brings that conversation into the world of ultra-endurance sport. After being diagnosed with osteoporosis and sustaining two sacral stress fractures, Mario used serial DEXA scans to track his bone mineral density and body composition across a demanding race season that included UTA100, the Elephant Miler and Coast to Kosciuszko.
His findings offer a valuable, personal insight into the demands ultra-running places on the body, and why strength training, recovery, fuelling and long-term monitoring matter just as much as the miles themselves. For athletes chasing endurance performance, Mario’s experience is a timely reminder that durability is not just built on fitness. It is built on bones, muscle, recovery and consistency.
Introduction
Ultra-endurance running places significant stress on the body through long training hours, repeated impact, and high energy demands. Running is generally considered beneficial for bone health because it is weight-bearing, however endurance athletes can still experience reduced bone mineral density (BMD), particularly when recovery and nutrition are inadequate.
A DEXA scan is a tool used to measure bone density and body composition, including lean mass, fat mass, and visceral fat. This provides a more detailed understanding of an athlete’s health than body weight alone. This paper explores the relationship between ultra-endurance running and bone health through a case study across three ultra-endurance events completed within one season:
- UTA100 (100 km)
- Elephant Miler (100 miles)
- Coast to Kosciuszko (240 km)
DEXA scans were completed before each race, shortly after, and again approximately five days later. The subject had previously been diagnosed with osteoporosis and had sustained two sacral stress fractures within four years. This prompted a stronger focus on monitoring bone health, recovery, and training strategies.
Bone Health and Training
Bone is constantly changing and adapting. Cells called osteoblasts help build bone, while osteoclasts break bone down. Healthy bone depends on maintaining a balance between these two processes.
Exercise helps stimulate bone growth, especially activities involving high force and varied movement patterns, such as strength training.
Ultra-running provides repeated loading through thousands of steps, but the impact is relatively low compared to resistance training. This means running alone may not be enough to maximise bone density, particularly when combined with high energy expenditure.
Methods
DEXA scans were conducted across the three races at consistent time points:
-
Before the race
-
Within several days after the race
-
Approximately five days post-race
Recovery strategies remained consistent throughout the season and included:
- Daily cold water immersion (~6 minutes)
- Relative rest
- A whole-food plant-based diet
The subject also completed approximately three gym-based strength sessions (heavy loading) per week.
Results
Body Composition
Across all races, lean mass increased immediately after racing, while fat mass and body fat percentage decreased. Most of these changes returned closer to normal within 5–7 days.
The increase in lean mass was likely related to inflammation, fluid retention, and glycogen restoration rather than true muscle gain.
Visceral Fat
Visceral fat increased immediately after races before returning toward baseline during recovery. These short-term increases were likely related to inflammation and stress responses.
Bone Mineral Density
Bone mineral density remained stable across the season, increasing slightly from 1.115 g/cm² to 1.141 g/cm². Although small fluctuations occurred after races, there was no evidence of long-term decline.
Discussion
The stable BMD observed in this case challenges the idea that high-volume endurance training always leads to bone loss. Instead, it suggests that bone health can be maintained when training is supported by proper recovery and nutrition.
However, running alone may not be enough to improve bone density. Regular strength training likely played an important role in maintaining bone health in this case. Unlike running, resistance training creates higher forces on the skeleton, which stimulates bone formation. It should also be acknowledged that strength training makes it difficult to attribute the results solely to ultra-running. However, this reflects real-world endurance training, where athletes often include gym work to improve performance and reduce injury risk.
Cold water immersion was used consistently throughout recovery. While it may reduce soreness and inflammation, research on its long-term effects on bone health remains unclear.
In this case, the short duration used is unlikely to have negatively affected bone density. Nutrition and energy intake also appear important.
Low energy availability is associated with Relative Energy Deficiency in Sport, which can negatively affect bone health and recovery. A nutrient-dense diet and structured recovery may have contributed to the stable BMD observed.
Practical Implications
This case study highlights that bone health in endurance athletes is influenced by more than running volume alone. Recovery, nutrition, and strength training all appear important.
Key takeaways include:
- Strength training should be included to support bone health
- DEXA scans can help monitor long-term trends
- Post-race body composition changes are often temporary
- Recovery and fuelling strategies are essential for long-term performance and health
Conclusion
This case study demonstrated that bone mineral density remained stable across a season of ultra-endurance racing, despite significant physical stress.
The findings suggest that maintaining bone health in endurance athletes requires more than simply accumulating mileage. A balanced approach that includes strength training, appropriate nutrition, and effective recovery strategies appears essential for both performance and long-term health.
Link to Full Paper
Mario Buchs is a certified sport endurance coach, ultrarunning coach, and the founder of Healthetica Coaching, where he takes a human-first approach to performance, resilience, and wellbeing. Specialising in ultra-endurance running, leadership, and holistic athlete development, Mario works with runners and professionals to build sustainable performance both on and off the trail/road/track.
Through his coaching, podcast Strides & Vibes, and involvement in projects such as the humanitarian IRAQ100, Mario combines practical experience with evidence-based strategies in endurance, recovery, mindset, and nutrition. His philosophy is simple: consistent, sustainable habits create long-term performance and healthier humans.
mario@healtheticacoaching.com
healtheticacoaching.com