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Effect of Age on the Cerebrovascular Responses to the Initiation of Dynamic Exercise
Author(s) -
Fisher James P,
Ahmed Amar,
Ainslie Phil N,
Bain Anthony R,
Wildfong Kevin W,
Morris Laura,
Flück Daniela
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.1020.6
Subject(s) - medicine , transcranial doppler , middle cerebral artery , cardiology , blood pressure , cardiac output , hemodynamics , diastole , vascular resistance , cerebral perfusion pressure , cerebral blood flow , ischemia
The rapid hemodynamic changes induced by the initiation of dynamic exercise robustly challenge the regulatory processes which ensure that cerebral perfusion is appropriately maintained. We sought to determine whether age alters the cerebrovascular responses to the initiation of dynamic exercise. Ten young (mean±SD, 23±2 years, 2 women) and eight older (65±3 years, 1 women) individuals performed a 5‐minute bout of semi‐recumbent leg cycling exercise at 75W. Blood pressure, cardiac output, total peripheral resistance (Finometer) and middle cerebral artery blood flow velocity (MCAv: transcranial Doppler ultrasound) were monitored. Gosling pulsatility index (PI) was calculated as; (systolic MCAv–diastolic MCAv)/mean MCAv. Beat‐to‐beat data during exercise were linearly interpolated at 1 Hz. At baseline, MAP (mean±SEM, young, 87±3; older, 93±4 mmHg), MCAv (young, 57±2; older, 56±3 cm/s) and PI (young, 0.88±0.4; older, 0.92±0.4 cm/s) were not different in young and older groups (P>0.05), while TPR tended to be lower (young, 16±1; older, 21±2 mmHg/L·min −1 , p=0.08) and CO tended to be higher (young, 5.6±0.4; older, 4.6±4 L·min −1 ; p=0.13) in the young. The initiation of exercise evoked a rapid and sustained increase in cardiac output and fall in total peripheral resistance, that was blunted in the older group. Blood pressure fell transiently at exercise onset, reaching a similar nadir (young, −9.9±2.8; older, −10.0±2.9 mmHg; p>0.05) after a similar duration (15±2; older, 13±2 s; p>0.05) in both groups. MCAv also fell transiently at the initiation of exercise (young, −5.3±1.5; older, −5.1±1.9 cm/s, p>0.05), but the nadir was reached later in the older group (young, 20±2; older, 29±2 s, p<0.05). PI increased rapidly at the onset of exercise in young individuals, but was elevated more sluggishly in older individuals. Collectively, these findings suggest that older individuals exhibit delayed cerebrovascular adjustments at the onset of exercise. Support or Funding Information This research was supported by a National Sciences and Engineering Research Council Discovery Grant and Canadian Research Chair in Cerebrovascular Physiology (PNA), the Swiss National Science Foundation (DF) and the British Heart Foundation (JPF).