REF-548 · Jaén-Carrillo et al., 2026 · International Journal of Sports Physiology and Performance · Paper
Durability in Trail Running — physiological & biomechanical drift over prolonged trail effort
Protocol & Participants
n=23 trained trail runners (11 women); 180-min treadmill run at 85% of the speed at lactate threshold + 0.5 mmol/L (steady state)
Every 60 min a 12-min uphill time trial at +12%
Continuous recording: VO2, RER, blood lactate, substrate oxidation, HR, RPE; gait: stride length, cadence, ground contact time, duty factor, vertical oscillation, leg stiffness
Key Results (abstract)
Steady-state running: HR and RPE increased (p < .001); VO2, blood lactate and energy cost stayed STABLE; carbohydrate oxidation decreased and fat oxidation increased (both p < .001)
Uphill time trials: distance covered fell by 6.6% (p < .001) and stride length declined; ground contact time and duty factor increased; RER and lactate decreased (both p < .001) — a progressive shift toward fat reliance
Oxygen cost and leg stiffness were PRESERVED across the protocol
Authors' conclusion: small but coordinated physiological and mechanical drifts without compromising overall energetic cost — "high durability" in trained trail runners, i.e. preserved biomechanical stability and running efficiency despite increasing perceived fatigue
Practical Application
In 23 trained trail runners (11 women) running 180 min at a steady-state pace with a 12-min +12% uphill time trial every hour, uphill TT distance fell 6.6% and RER/lactate dropped (more fat use), while oxygen cost, energy cost and leg stiffness held and HR/RPE climbed — trained trail runners are durable: the price of 3 hours is a modest loss of climbing output and a metabolic shift, not a collapse of mechanics
What drifts is cardiovascular/perceptual (HR, RPE) and substrate use, not efficiency — for a masters trail/ultra runner this points at fuelling (carbohydrate oxidation fell) and at practising climbing late in long runs, rather than at "protecting form." Inference from the pattern of drift
Train durability specifically — long sessions with uphill efforts in a fatigued state. Not from this paper; the base's own practice
Nutrition/durability entries (REF-543 fuel-for-work, REF-528 ultra) are the natural companions
Limitations
Treadmill protocol (controlled), not a real trail race with technical ground/descents
Single session (n=23), trained cohort — describes drift, does not test how to train it
The +12% climbs are standardised — real trail is more variable
Group means; individual drift is not reported in the abstract
How this entry was checked and changed
Why this level
regraded 2026-09-27 from B+: uncontrolled single-session pre-post, n=23
Content correction 2026-09-27
"Fresh laboratory values poorly predict performance after hours of work" -> not in the abstract and at odds with its conclusion (energy cost and leg stiffness preserved; "high durability"); removed
Added the actual results: uphill TT distance −6.6%, HR/RPE up, VO2/lactate/energy cost stable, CHO oxidation down / fat up, ground contact time and duty factor up, oxygen cost and leg stiffness preserved
Level B+ -> B (single-session pre-post, n=23); Journal year 2025 -> 2026 (publication year of the DOI record); Sport line "trail-running, running" -> "trail running, running"