Narattaphol CharoenphandhuJarinthorn TeerapornpuntakitSarawut LapmaneeNitita DorkkamNateetip KrishnamraJantarima CharoenphandhuMahidol UniversityFaculty of Medicine, Thammasat University2018-05-032018-05-032011-11-01Journal of Physiological Sciences. Vol.61, No.6 (2011), 473-486188065462-s2.0-84855997467https://repository.li.mahidol.ac.th/handle/20.500.14594/11442Endurance swimming is known to increase duodenal calcium absorption in normal rats and bone strength in estrogen-deficient rats. Because the stress resulting from forced training often attenuates the stimulatory effect of exercise, swimming in an inescapable chamber should reveal both the positive effect of the exercise and the negative effect of stress. In the work reported herein, swimming rats showed no signs of stress during 2 weeks of training. However, stress response gradually developed thereafter and peaked at weeks 6 and 7. In rats swimming for 2 weeks, transcellular duodenal calcium transport was enhanced ∼ 2-fold. In contrast, calcium absorption was reduced in rats swimming for 8 weeks, consistent with the absence of swimming-induced upregulation of calcium transporter genes in the 8-week group. In conclusion, prolonged stress hindered the stimulatory effect of swimming on duodenal calcium absorption, and thus endurance exercise should be performed without forced training or stress to retain its beneficial effect on calcium metabolism. © The Physiological Society of Japan and Springer 2011.Mahidol UniversityBiochemistry, Genetics and Molecular BiologyArticleSCOPUS10.1007/s12576-011-0168-5