2007, Piran, Slovenia

as observed at rest after LBNP was removed.
FBF(ml/min/100g)
(ml/min/100g)
( (ml/min/100g)
(
FBF(ml/min/100g )
LBNP
150mmH 2 O
5
4
3
2
1
0
0
0
70
70
60
60
50
50
40
40
30
30
20
20
10
10
0
0
LBNP
150mmH 2 O
5 10
Time Time (min)
(min)
recovery
rest LBNP
recovery
150mmH 2 O
15
5 10 15
Time (min)
Fig. 1Changes in forearm blood flow(FAB) and finger blood flow(FBF) FBF) at at the
the
two levels (150and300mmH 2
2 O) of LBNP in the athletes ( :closed circles) and
non athletes ( : open circles). Vertical bars are SEs. }
FAB(ml/min/100g)
FBF(ml/min/100g )
6
5
4
3
2
1
70
60
50
40
30
20
10
rest LBNP
300mmH 2 O
recovery
LBNP
300mmH 2 O
Gravitational Physiology
0 0 5 10 15
Time (min)
recovery
0 0 5 10
Time (min)
15
DISCUSSION
The cardiovascular response was clearly observed in our experiment with the
application of 300 mmH2O LBNP (Figure 2). Both forearm blood flow and finger
blood flow decreased with the application of LBNP, regardless of the level of
endurance training. We also observed significant differences in forearm blood flow
(plethysmography) between the athletes and non-athletes. However, when comparing
forearm blood flow measured using laser Doppler flowmetry and finger blood flow,
there were no significant differences between the groups. When comparing resting
forearm blood flow using laser-Doppler flowmetry and plethysmography during
LBNP application and recovery, there were no differences between the athletes and
non-athletes. Moreover, there was no difference in the reduction of cutaneous blood
flow caused by the application of LBNP, which leads us to think that endurance
training has only a little influence on the change of cutaneous blood flow in response
to baroreceptor reflex of lower pressure. On the contrary, as far as muscle blood flow
was concerned, the reduction at rest and during LBNP application were greatly
different between the two groups. When compared with the non-athletes, the athletes
should a much greater returning blood flow from muscles than from skin in response
to gravitational pressure. These results seem to suggest that, although it is important to
maintain cutaneous blood flow for heat dissipation by vasodilation in the heat,
endurance training makes it possible to mobilize muscle blood flow to respond to
baroreceptor reflex when cutaneous blood flow is not enough to compensate
baroreceptor reflex arising from the change in posture. Thus, the athletes could be said
to have greater tolerance to the heat compared to the non-athletes.
rest
45