Table 2.
Haemodynamic and neural responses to a cold pressor test (CPT) performed under normothermic and heat stress conditions
| Normothermia | Heat stress | |||||||
|---|---|---|---|---|---|---|---|---|
| Young (n = 11) | Aged (n = 10) | Young (n = 11) | Aged (n = 10) | |||||
| Baseline | CPT | Baseline | CPT | Baseline | CPT | Baseline | CPT | |
| Heart rate (beats min−1) | 59 ± 5 | 66 ± 6* | 64 ± 6 | 70 ± 9* | 100 ± 12* | 99 ± 9 | 91 ± 9*,‡ | 92 ± 10 |
| MAP (mmHg) | 86 ± 6 | 104 ± 6* | 96 ± 5† | 115 ± 8*,† | 82 ± 8 | 98 ± 9# | 90 ± 5* | 95 ± 5 |
| Burst frequency (bursts min−1) | 15 ± 4 | 33 ± 7* | 31 ± 3† | 48 ± 11*,† | 47 ± 6* | 58 ± 8# | 63 ± 11*,† | 69 ± 10 |
| Burst incidence (bursts (100 CC)−1) | 26 ± 8 | 48 ± 11* | 50 ± 7† | 66 ± 9*,† | 48 ± 8* | 57 ± 9# | 67 ± 9*,† | 75 ± 9†,# |
| ΔTotal activity (units min−1) | 0 ± 0 | 486 ± 173* | 0 ± 0 | 688 ± 549* | 0 ± 0 | 356 ± 184# | 0 ± 0 | 342 ± 280# |
| Plasma [A] (pg ml−1) | 27 ± 16 | 56 ± 28 | 34 ± 24 | 46 ± 23 | 47 ± 13 | 137 ± 57# | 39 ± 20 | 90 ± 41 |
| Plasma [NA] (pg ml−1) | 145 ± 22 | 234 ± 53* | 288 ± 51† | 419 ± 53*,† | 327 ± 90* | 432 ± 94# | 419 ± 82* | 512 ± 57# |
Values are means ± 95% confidence intervals. MAP, mean arterial pressure; [A], adrenaline concentration; [NA], noradrenaline concentration.
*
Significantly different from normothermic baseline.
†
Significantly different from young for the indicated time point (P ≤ 0.05).
#
Significantly different from heat stress baseline.
‡
Significantly different change from normothermia compared to the change in this variable in the young (P ≤ 0.05).