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EFFECTS OF HIGH INTENSITY EXERCISE TRAINING ON CARDIOVASCULAR FUNCTION, OXYGEN UPTAKE, INTERNAL OXYGEN TRANSPORT AND OSMOTIC BALANCE IN CHINOOK SALMON (ONCORHYNCHUS TSHAWYTSCHA) DURING CRITICAL SPEED SWIMMING

1
Continuing Studies in Science, Simon Fraser University, Burnaby, BC, V5A
1S6, Canada
2
Department of Biological Sciences, Simon Fraser University, Burnaby, BC,
V5A 1S6, Canada
3
Holar Agricultural College, 551 Sudarkrokur, Iceland
4
Department of Fisheries and Oceans, West Vancouver Laboratory, West
Vancouver, BC, V7V 1N6 Canada
*
Present address: Matre Research Station IMR, 5198 Matredal, Norway
Author for correspondence (e-mail:
farrell{at}sfu.ca
)
Accepted May 14, 2001
To examine cardiorespiratory plasticity, cardiovascular function, oxygen
consumption, oxygen delivery and osmotic balance were measured at velocities
up to critical swimming speed (Ucrit) in seawater-adapted
chinook salmon. We used two groups of fish. The control group had swum
continuously for 4 months at a low intensity (0.5 BL s-1)
and the other was given a high-intensity training regimen (a
Ucrit swim test on alternate days) over the same period of
time. Compared with available data for other salmonid species, the control
group had a higher maximum oxygen consumption
(
o2max; 244
µmol O2 min-1 kg-1), cardiac output
(
max; 65 ml
min-1 kg-1) and blood oxygen content
(CaO2; 15 ml O2 dl-1). Exercise
training caused a 50% increase in
o2max without
changing either Ucrit or CaO2, even
though there were small but significant increases in hematocrit, hemoglobin
concentration and relative ventricular mass. During swimming, however,
exercise-trained fish experienced a smaller decrease in body mass and muscle
moisture, a smaller increase in plasma osmolality, and reduced venous oxygen
stores compared with control fish. Consequently, exercise training apparently
diminished the osmorespiratory compromise, but improved oxygen
extraction at the tissues. We conclude that the training-induced increase in
o2max provided
benefits to systems other than the locomotory system, such as osmoregulation,
enabling trained fish to better multitask physiological functions while
swimming. Furthermore, because a good interspecific correlation exists between
o2max and
arterial oxygen supply
(
o2max;
r2=0.99) among temperate fish species, it is likely that
CaO2 and
max are principal loci for
cardiorespiratory evolutionary adaptation but not for intraspecific
cardiorepiratory plasticity as revealed by high intensity exercise
training.
Key words: salmon, cardiac output, heart rate, oxygen consumption, plasma osmolality, oxygen transport, swimming, exercise training, osmorespiratory compromise, Oncorhynchus tshawytscha
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