Exercise hemorheology: Classical data, recent findings and unresolved issues

Abstract

The present review focuses on the past and recent knowledge in the field of exercise hemorheology and presents some unresolved issues for opening discussion. Acute exercise is associated with a rise in hematocrit which results in an increase in blood viscosity. Whereas increased blood viscosity was previously viewed as having negative consequences for cardiovascular function and aerobic performance, recent findings suggest dynamic changes in blood viscosity might be useful for vascular function during exercise by increasing nitric oxide production. Other determinants of blood viscosity are altered by exercise (e.g., decreased red blood cell deformability, increased red blood cell aggregation and plasma viscosity) and may, independent of the associated effect on blood viscosity, directly modulate aerobic capacity. However, the data published on the effects of exercise on the hemorheology are not consistent, with some studies showing decreased, unchanged, or increased red blood cell deformability/aggregation when compared with rest. These discrepancies seem to be related to the exercise protocol investigated, the population tested or the methodogy utilized for hemorheological measurements. Finally, this review focuses on the effects of exercise training (i.e. chronic physical activity) on the hemorheological profile of healthy individuals and patients with cardiovascular and metabolic disorders. P. Connes et al. / Blood rheology and exerciseaddress classical findings in exercise hemorheology and will present new directions. In addition, some unresolved issues will be presented for opening discussion. Acute effects of exercise on hemorheology and relationships with performance2.1. Blood viscosity P. Connes et al. / Blood rheology and exercise 189 PRE 90 Blood viscosity (mPa/s) POST 90 POST 225 5 6 7 8 9

Exercise-Induced Blood Lactate Increase Does Not Change Red Blood Cell Deformability in Cyclists

“…In the present study, unloaded and moderate-intensity cycling did not alter η b , whereas heavy-intensity cycling significantly increased η b . The ∼25–30% increase in η b due to heavy-intensity cycling agrees with values reported for blood sampled in the post-exercise period [1]. Exercise-induced increases in η b are principally mediated by elevated haematocrit and plasma viscosity [3].…”

“…Initiation of exercise redistributes fluids away from the plasma compartment, increasing the packed cell volume of blood and relative concentration of plasma proteins, leading to elevated blood and plasma viscosities [1]. Exercise-induced alterations to the red blood cell (RBC), including increased RBC aggregation and decreased RBC deformability, directly increase blood viscosity [2].…”

“…The so called ‘anaerobic threshold’ demarks moderate- from heavy-intensity exercise, and represents the lowest work rate at which the clearance of lactate is surpassed by the rate of lactate appearance in the blood [4]. Changes in blood chemistry which occur at the anaerobic threshold are thought to significantly alter haemorheology [1], [3]. Decreased blood pH, for example, has been consistently demonstrated to increase the rigidity of RBC [5], [6], which in-turn increases higher-shear blood viscosity [7].…”

Time-course responses of circulating microRNAs to three resistance training protocols in healthy young men

“…Exercise induced c-miRNA elevations may represent a more generalized response to internal and/or external stress. Factors, including mechanical, oxidative or nitrosative stress, damaged cells 26 , changes in blood cell numbers 38 or hemolysis 39 and the release of secreted extracellular vesicles (exosomes) 40 , likely induce c-miRNAs production during exercise. However, c-miRNAs responded differently to the RT protocols in the present study, indicating a specific response to the demands of the exercise rather than a global exercise-induced c-miRNA response.…”

MicroRNAs in skeletal muscle and their regulation with exercise, ageing, and disease

“…The expression of plasma miRNAs derived from hematopoietic cells correlates strongly with hematopoietic cell number (Pritchard et al, 2012). Therefore, changes in circulating miRNA levels within subjects may reflect exercise-induced changes in blood cell numbers (Tanimura et al, 2009; Connes et al, 2013; Tonevitsky et al, 2013) rather than muscle-specific adaptations. Tonevitsky et al completed a miRNA array in whole blood of trained individuals following a single bout of treadmill exercise.…”