High-Intensity Interval Training Improves Erythrocyte Osmotic Deformability

Introduction Physical exercise or hypoxic exposure influences erythrocyte susceptibility to osmotic stress, and the aquaporin 1 (AQP1) facilitates the transport of water in erythrocytes. This study investigated whether high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) affect erythrocyte osmotic deformability by modulating AQP1 function under hypoxic stress. Methods Forty-five healthy sedentary males were randomized to engage in either HIIT (3-min intervals at 40 % and 80 % VO2 reserve, n=15) or MICT (sustained 60 % VO2 reserve, n=15) on a bicycle ergometer for 30 min/day, 5 days/week for 6 weeks, or to a control group that did not perform any exercise (n=15). All subjects were analyzed with osmotic gradient ektacytometry for assessing erythrocyte membrane stability and osmotic deformability following hypoxic exercise (HE) (100W under 12%O2 for 30 min). Results Before the intervention, HE increased the shear stress at 50% of maximal elongation (SS1/2) and the ratio of SS1/2 to maximal elongation index (SS1/2/EImax) on erythrocytes pretreated with 50 Pa of shear stress for 30 min and diminished HgCl2-depressed osmolality at 50%EImax (Ohyper). However, both HIIT and MICT for 6 weeks diminished the elevations of erythrocyte SS1/2 and SS1/2/EImax caused by HE. Moreover, HIIT also increased contents of erythrocyte AQP1 proteins while enhancing HgCl2-depressed Ohyper and area under elongation index-osmolarity curve (AUC) following HE. Additionally, changes in erythrocyte AQP1 contents were associated with changes in HgCl2-depressed erythrocyte Ohyper and AUC. Conclusion Acute HE reduces erythrocyte membrane stability, whereas either HIIT or MICT attenuates the depression of erythrocyte membrane stability by HE. Moreover, HIIT increases the AQP1 content and facilitates the HgCl2-mediated osmotic deformability of erythrocytes following HE. Please send correspondence to: Professor, Jong-Shyan Wang, Graduate Institute of Rehabilitation Science, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Tao-Yuan, 333, Taiwan. Fax # 886-3-2118700. s5492@mail.cgu.edu.tw This work was supported by the National Science Council of Taiwan (grant number NSC 106-2314-B-182-048-MY3), Chang Gung Medical Research Program (grant number CMRPD1E0263 and CMRPD3G0032), and Healthy Aging Research Center, Chang Gung University (grant number EMRPD1A0841). The results of the present study do not constitute endorsement by ACSM. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. No conflicts of interest, financial or otherwise, are declared by the authors. Submitted for publication October 2018. Accepted for publication February 2019. © 2019 American College of Sports Medicine

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