Long-term heat acclimation training in mice: Similar metabolic and running performance adaptations despite a lower absolute intensity than training at temperate conditions

• Published in: Journal of thermal biology 2024-01, Vol.119, p.103797-103797, Article 103797
• Main Authors: Zanetti, Gustavo de Oliveira, Pessoa, Pedro William Martins, Vieira, Tales Sambrano, Garcia, Rodrigo de Almeida, Santos Barbosa, Nicolas Henrique, Arantes, Rosa Maria Esteves, Kettelhut, Isis do Carmo, Navegantes, Luiz Carlos C., Wanner, Samuel Penna, Soares, Danusa Dias, Gonçalves, Dawit Albieiro Pinheiro
• Format: Article
• Language: English
• Subjects: acclimation; Aerobic training; blood; body temperature; glycogen; heat; Heat stress; lactic acid; liver; males; mechanical loads; metabolism; mice; orthopedics; Peak oxygen consumption; peak oxygen uptake; Thermoregulation
• ISSN: 0306-4565; 1879-0992
• DOI: 10.1016/j.jtherbio.2024.103797

This study investigated the impact of long-term heat acclimation (HA) training on mouse thermoregulation, metabolism, and running performance in temperate (T) and hot (H) environments. Male Swiss mice were divided into 1) Sedentary (SED) mice kept in T (22 °C; SED/T), 2) Endurance Trained mice (ET, 1 h/day, 5 days/week, 8 weeks, 60 % of maximum speed) in T (ET/T), 3) SED kept in H (32 °C; SED/H), and 4) ET in H (ET/H). All groups performed incremental load tests (ILT) in both environments before (pre-ET) and after four and eight weeks of ET. In the pre-ET period, H impaired (∼30 %) performance variables (maximum speed and external work) and increased (1.3 °C) maximum abdominal body temperature compared with T. In T, after four weeks, although ET/H exercised at a lower (∼30 %) absolute intensity than ET/T, performance variables and aerobic power (peak oxygen uptake, VO2peak) were similarly increased in both ET groups compared with SED/T. After eight weeks, the external work was higher in both ET groups compared with SED/T. Only ET/T significantly increased VO2peak (∼11 %) relative to its pre-ET period. In H, only after eight weeks, both ET groups improved (∼19 %) maximum speed and reduced (∼46 %) post-ILT blood lactate concentrations compared with their respective pre-ET values. Liver glycogen content increased (34 %) in both ET groups and SED/H compared with SED/T. Thus, ET/H was performed at a lower absolute intensity but promoted similar effects to ET/T on metabolism, aerobic power, and running performance. Our findings open perspectives for applying HA training as part of a training program or orthopedic and metabolic rehabilitation programs in injured or even obese animals, reducing mechanical load with equivalent or higher physiological demand. •Hot (H) environment causes hyperthermia and ergolytic action in running mice.•Endurance training (ET) in H and temperate (T) environments causes similar effects.•ET/H and ET/T similarly improve metabolism, aerobic power, and running performance.•ET/H is performed in a lower absolute, but similar relative, intensity than ET/T.•ET/H induces a similar physiological strain to ET/T at a lower mechanical stress.