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.