Exercise intensity nonlinearly correlates with proximal renal tubular stress in young men, with an exploratory breakpoint at 6.76 METs beyond which exercise-associated subclinical renal tubular stress accelerates rapidly.
Post-exercise urinary L-FABP concentrations increased significantly from baseline following a 20-minute physical training session.
Restricted cubic splines analysis confirmed a nonlinear dose-response relationship between exercise intensity (METs) and urinary L-FABP concentrations.
An exploratory intensity threshold (breakpoint) was identified at 6.76 METs, below which exercise intensity was not significantly associated with post-exercise L-FABP.
Above the 6.76 MET threshold, urinary L-FABP escalated rapidly with increasing exercise intensity.
The study used urinary liver-type fatty acid-binding protein (L-FABP) as a sensitive marker of proximal tubular stress in an observational cohort design.
This research suggests that strenuous physical exercise places measurable stress on the kidneys, specifically on the tiny filtering tubes (proximal tubules) within them. The study followed 285 healthy young men through a 20-minute exercise session and measured a protein called L-FABP in their urine—a sensitive indicator of kidney tubule stress—before and 30 minutes after exercise. On average, this protein more than doubled after exercise (from 0.90 to 1.89 µg/gCr), indicating that even a brief workout causes detectable, though temporary, kidney stress in otherwise healthy individuals. Importantly, the relationship between exercise intensity and kidney stress was not a simple straight line. Instead, there was a clear 'tipping point' around 6.76 METs—a unit of exercise intensity roughly corresponding to activities like jogging or fast cycling. Below this threshold, increasing exercise intensity had virtually no association with kidney stress markers. Above it, kidney stress rose sharply and significantly with each additional increase in intensity. This nonlinear pattern means that moderate exercise appears relatively safe for the kidneys, while higher-intensity exercise triggers a much more pronounced stress response. This research suggests that there may be an exploratory intensity boundary in young healthy men beyond which the kidneys experience accelerated subclinical (below the level of clinical symptoms) stress during exercise. While this kidney stress appears temporary and was observed in healthy individuals, the findings could be relevant for understanding exercise-related kidney responses in athletes, military personnel, or individuals with pre-existing kidney vulnerabilities. The authors emphasize that 6.76 METs should be considered an exploratory threshold requiring further validation rather than a definitive clinical cutoff.
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Upload Your LabsThanh H, Le D, Anh T, Thai C, Hai G, Xuan D. (2026). Nonlinear Dose-Response Association Between Exercise Intensity and Urinary Liver-Type Fatty Acid-Binding Protein in Young Men: A Piecewise Threshold Analysis.. International journal of molecular sciences. https://doi.org/10.3390/ijms27198539