2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
Figure 3. Effect of increasing concentrations of the β1 agonist on heart rate in controls
(white points, interrupted line) and winter swimmers (black points, solid line).
Administrations of both β1 and β 2 adrenomimetic were without effect on blood presure and
rectal and skin temperatures. Generally, winter swimmers showed higher blood pressure and
lower rectal temperature, however.
DISCUSSION
To specify changes in adrenergic functions after adaptation of humans to cold, effect of
administration of increasing concentrations of β1 and β2 adrenomimetics (Dobutamine,
Bricanyl) on resting metabolic rate, heart rate, blood pressure and finger skin temperatures of
young men (21,4 years, body mass 79 kg) and of cold adapted winter swimmers (42,8 years.
body mass 83 kg) was studied. Increase in metabolic rate, mediated by β1 and β2
adrenomimetics was attenuated after cold adaptation, indicating downregulation of β1 and β2
adrenoceptors. Since cold adapted humans have greater capacity of nonshivering
346
Heart rate (beats.min -1 )
Heart rate (beats.min -1 )
120
110
100
90
80
70
60
50
120
110
100
90
80
70
60
β1 adrenergic agonist
-0,5 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5
Infusion rate (µg.kg -1 .min -1 )
β2 adrenergic agonist
50
-0,05 0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40 0,45
Infusion rate (µg.kg -1 .min -1 )
Figure 4. Effect of increasing concentrations of the β2 agonist on heart rate in controls (white
points, interrupted line) and winter swimmers (black points, solid line).