Anemia, heart failure and exercise training

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% V˙O2 reserve, n = 15) or MICT (sustained 60% V˙O2 reserve, n = 15) on a bicycle ergometer for 30 min·d, 5 d·wk for 6 wk, 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 after hypoxic exercise (HE) (100 W 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 wk 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 after HE. Additionally, changes in erythrocyte AQP1 contents were associated with changes in HgCl2-depressed erythrocyte Ohyper and area under elongation index-osmolarity curve.

CONCLUSIONS

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 after HE.

Cycling Exercise Training Alleviates Hypoxia-Impaired Erythrocyte Rheology

PURPOSE

Physical exercise or hypoxic exposure influences hemorheology and acid-base homeostasis. Band 3 protein in erythrocytes modulates cells' rheological properties and anion transport ability. This study investigated how cycling aerobic interval training (AIT) and moderate continuous training (MCT) affect the rheological function and band 3 activity of erythrocytes under hypoxic exercise (HE) stress.

METHODS

Forty-five healthy sedentary men were randomized to engage in either AIT (3-min intervals at 40% and 80% of VO2max, n = 15) or MCT (sustained 60% of VO2max, n = 15) on a bicycle ergometer for 30 min · d(-1) (5 d · wk(-1) for 5 wk) or to a control group that did not perform any exercise (n = 15). Erythrocyte rheological responses to HE (100 W under 12% O2 for 30 min) were determined before and after various regimens.

RESULTS

Acute HE increased the aggregation and osmotic fragility of erythrocytes, decreased the deformability of erythrocytes, and depressed erythrocyte band 3 activity, as indicated by lowered anion transport ability. Following 5 wk of intervention, the AIT group exhibited maximal work rate and VO2max higher than those in the MCT and control groups. Moreover, cycling AIT and MCT diminished the extent of erythrocytes' enhanced aggregation and osmotic fragility and reduced their deformability and band 3 activity caused by HE. Additionally, erythrocyte band 3 activity was directly related to erythrocyte deformability and inversely related to erythrocyte aggregation and osmotic fragility.

CONCLUSIONS

Cycling AIT is superior to cycling MCT in enhancing aerobic capacity. Moreover, either cycling AIT or MCT effectively alleviates HE-evoked impairments of erythrocyte rheological characteristics and band 3 function.