Maunder, EdKing, AndrewRothschild, Jeffrey ABrick, Matthew JLeigh, Warren BHedges, Christopher PMerry, Troy LKilding, Andrew E2024-11-122024-11-122024-03-06Pfluegers Archiv: European journal of physiology, ISSN: 0031-6768 (Print); 0031-6768 (Online), Springer, 476(6), 939-948. doi: 10.1007/s00424-024-02939-80031-67680031-6768http://hdl.handle.net/10292/18292There is some evidence for temperature-dependent stimulation of mitochondrial biogenesis; however, the role of elevated muscle temperature during exercise in mitochondrial adaptation to training has not been studied in humans in vivo. The purpose of this study was to determine the role of elevating muscle temperature during exercise in temperate conditions through the application of mild, local heat stress on mitochondrial adaptations to endurance training. Eight endurance-trained males undertook 3 weeks of supervised cycling training, during which mild (~ 40 °C) heat stress was applied locally to the upper-leg musculature of one leg during all training sessions (HEAT), with the contralateral leg serving as the non-heated, exercising control (CON). Vastus lateralis microbiopsies were obtained from both legs before and after the training period. Training-induced increases in complex I (fold-change, 1.24 ± 0.33 vs. 1.01 ± 0.49, P = 0.029) and II (fold-change, 1.24 ± 0.33 vs. 1.01 ± 0.49, P = 0.029) activities were significantly larger in HEAT than CON. No significant effects of training, or interactions between local heat stress application and training, were observed for complex I-V or HSP70 protein expressions. Our data provides partial evidence to support the hypothesis that elevating local muscle temperature during exercise augments training-induced adaptations to mitochondrial enzyme activity.Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.http://creativecommons.org/licenses/by/4.0/ExerciseHeatMitochondriaMuscleExerciseHeatMitochondriaMuscle3109 Zoology3101 Biochemistry and Cell Biology31 Biological SciencesPhysical Activity6.7 Physical0606 Physiology1106 Human Movement and Sports Sciences1116 Medical PhysiologyPhysiology3101 Biochemistry and cell biology3109 Zoology3208 Medical physiologyMaleHumansAdaptation, PhysiologicalMuscle, SkeletalExerciseAdultHeat-Shock ResponseMitochondria, MuscleHot TemperatureElectron Transport Complex IYoung AdultElectron Transport Complex IIMuscle, SkeletalMitochondria, MuscleHumansElectron Transport Complex IElectron Transport Complex IIExerciseAdaptation, PhysiologicalHeat-Shock ResponseAdultMaleHot TemperatureYoung AdultMaleHumansAdaptation, PhysiologicalMuscle, SkeletalExerciseAdultHeat-Shock ResponseMitochondria, MuscleHot TemperatureElectron Transport Complex IYoung AdultElectron Transport Complex IIJournal ArticleOpenAccess10.1007/s00424-024-02939-8