Abstract
Background: Pioneer studies demonstrate the impact of extreme sport load on the human brain, leading to threatening conditions for athlete's health such as cerebral edema. The investigation of brain water diffusivity, allowing the measurement of the intercellular water and the assessment of cerebral edema, can give a great contribution to the investigation of the effects of extreme sports on the brain. We therefore assessed the effect of supra-physiological effort (extreme distance and elevation changes) in mountain ultra-marathons (MUMs) athletes combining for the first time brain magnetic resonance imaging (MRI) and blood parameters.Methods:This longitudinal study included 19 volunteers (44.2 ± 9.5 years) finishing a MUM (330 km, elevation + 24000 m). Quantitative measurements of brain diffusion-weighted images (DWI) were performed at 3 time-points: Before the race, upon arrival and after 48 h. Multiple blood biomarkers were simultaneously investigated. Data analyses included brain apparent diffusion coefficient (ADC) and physiological data comparisons between three time-points.Results:The whole brain ADC significantly increased from baseline to arrival (p = 0.005) and then significantly decreased at recovery (p = 0.005) to lower values than at baseline (p = 0.005). While sodium, potassium, calcium, and chloride as well as hematocrit (HCT) changed over time, the serum osmolality remained constant. Significant correlations were found between whole brain ADC changes and osmolality (p = 0.01), cholesterol (p = 0.009), c-reactive protein (p = 0.04), sodium (p = 0.01), and chloride (p = 0.002) plasma level variations.Conclusions:These results suggest the relative increase of the inter-cellular volume upon arrival, and subsequently its reduction to lower values than at baseline, indicating that even after 48 h the brain has not fully recovered to its equilibrium state. Even though serum electrolytes may only indirectly indicate modifications at the brain level due to the blood brain barrier, the results concerning osmolality suggest that body water might directly influence the change in cerebral ADC. These findings establish therefore a direct link between general brain inter-cellular water content and physiological biomarkers modifications produced by extreme sport.
Highlights
Mountain ultra-marathons (MUMs) have become increasingly popular in the last decade and they are considered a model to investigate acute responses to extreme load and stress (Millet and Millet, 2012)
We investigated changes occurring during and after ultra-marathon in brain water diffusivity aiming at investigating the presence of cerebral edemas
Brain magnetic resonance imaging (MRI) apparent diffusion coefficient (ADC) derived from diffusion weighed imaging (DWI) was used, which measures the diffusion of water notably in the inter-cellular compartment
Summary
Mountain ultra-marathons (MUMs) have become increasingly popular in the last decade and they are considered a model to investigate acute responses to extreme load and stress (Millet and Millet, 2012). Blood biomarkers changes confirm this response, showing higher C-reactive protein concentrations (Millet et al, 2011a; Saugy et al, 2013) and decreased hematocrit levels in runners right after MUMs (Robach et al, 2014; Vitiello et al, 2015). Besides these physiological changes, pioneer studies demonstrate the impact of extreme sport load on the human brain. We assessed the effect of supra-physiological effort (extreme distance and elevation changes) in mountain ultra-marathons (MUMs) athletes combining for the first time brain magnetic resonance imaging (MRI) and blood parameters
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