MR measurements can be accurately performed during 4486 km of running, opening a window into in vivo assessment of hindfoot articular cartilage under extreme ultra-endurance loading. This observational cross-sectional study included 22 randomized participants of TransEurope FootRace between Italy and the North Cape, which was accompanied by a trailer-mounted 1.5T MRI scanner over 9 weeks. Four follow up MR examinations of subtalar and midtarsal joints were performed. Statistics of cartilage T2∗ and thickness were obtained. Nearly all observed joints showed an initial significant mean T2∗ increase of 20.9% and 26.3% for the left and right side, followed by a relative decrease of 28.5% and 16.0% during the second half, respectively. It could be demonstrated that mobile MRI field studies allow in vivo functional tissue observations under extreme loading. Elevated T2∗ values recovered during the second half of the ultramarathon supported the evidence that this response is a physiological adaptive mechanism of chondrocyte function via upregulation of de novo synthesis of proteoglycans and collagen. These changes occurred in a distinct asymmetric pattern leaving a biochemical signature of articular cartilage that allows in vivo insight into joint loading. In conclusion, the normal articular cartilage of the hindfoot is resilient and adaptive, leaving extreme endurance activities up to limitless human ambition.
Bibliographical noteFunding Information:
We would like to thank all the athletes of TEFR who took part at this proje?t. ?onsidering their immense physi?al and mental stresses they showed an extraordinary ?omplian?e on every day of the ra?e. Contributions. All authors of this manuscript had substantial contribution to ?on?eption and design or a?quisition, analysis and interpretation of data; all revised it ?riti?ally for important intelle?-tual ?ontent and did final approval of the version to be published. Role of funding sour?e. This work is supported in part by the German Resear?h Asso?iation (DFG: “Deuts?he Fors?hungsgemein-s?haft”), under Grants S?HU 2514/1-1 and S?HU 2514/1-2. The funders had no role in study design, data ?olle?tion and analysis, de?ision to publish, or preparation of the manus?ript. No additional external funding was re?eived for this study. ?ompeting interests. The authors de?lare that they have no finan?ial or non-finan-?ial ?ompeting interests. There are no finan?ial or non-finan?ial ?ompeting interests of other people or organizations influen?ing our interpretation of data or presentation of information.
- chondral, cartilage
- functional magnetic resonance imaging