We investigated relationships among body composition, blood rheology, and
exercise performance in 14 rugbymen (19–31 yr, weight 65.8–109.2 kg, height
1.7–1.96 m, body mass index 21.7–33.1 kg/m
^{2}
) who underwent a standardized
submaximal exercise session on cycloergometer corresponding to 225 kJ over 30
min. The rheologic response to exercise was measured with the MT90 viscometer
and the Myrenne aggregometer. Dehydration, evaluated by precision weighing,
resulted in a loss of 360 to 973 g water, i.e., 1.69 to 4.32 g/kJ. This loss of
water is not correlated to plasma volume contraction as assessed by the equation
of Greenleaf. Hemorheologic changes are observed, but they are correlated
neither to water loss, nor to plasma volume contraction. A 36% increase in blood
viscosity (
p<0.01
) is mainly explained by a red
blood cell rigidification (
p<0.02
), although hematocrit and
plasma viscosity also increase (
p<0.01
). Isometric adductor
strength (specific ergometer) is correlated to erythrocyte flexibility
(
r=0.680
,
p<0.01
). Red cell aggregability (Myrenne
aggregometer) is correlated to fat mass measured by bioelectrical impedance
(
r=0.634
,
p<0.02
). Aerobic working capacity index
W
_{170}
is
negatively correlated to the increase in plasma viscosity during exercise
(
r=-0.546
,
p<0.05
), suggesting that this event is
less important in stronger individuals. This study shows that fat mass, even
within a physiological range, is a determinant of erythrocyte aggregability,
suggesting that training‐induced alterations in body composition play a role in
the specific hemorheologic profile of athletes. In addition, both erythrocyte
flexibility and the magnitude of fluid shifts during exercise appear to be
related to fitness in these sportsmen.
