Spontaneous baroreflex sensitivity in young and older people during voluntary and electrically evoked isometric exercise.
BACKGROUND
In young people, cardiovagal baroreflex sensitivity alters during isometric exercise. We investigated whether the reduced resting baroreflex sensitivity seen with increasing age is similarly altered during exercise.


METHODS
Cardiovagal baroreflex sensitivity was examined in 8 young (age+/-SEM, 25+/-1.7 years) and 9 older (61+/-3.0 years) subjects, using sequence analysis during voluntary and electrically evoked isometric exercise (at 30% maximum voluntary strength) and during subsequent post-exercise circulatory occlusion.


RESULTS
In all phases of both conditions, baroreflex sensitivity was significantly reduced in the older group compared with the young group. (Median (interquartile range), voluntary 7.0 (4.4) vs 3.6 (3.8) ms x mmHg(-1), post-exercise circulatory occlusion 9.0 (8.2) vs 4.6 (4.0) ms x mmHg(-1); electrically evoked 6.6 (10.6) vs 3.2 (3.6) ms x mmHg(-1), post-exercise circulatory occlusion 8.3 (7.7) vs 2.9 (2.2) ms x mmHg(-1), young vs older respectively; P<0.05.) There was a marked rightward shift (resetting) of the baroreflex during exercise with the exception of electrically evoked in the older group.


CONCLUSIONS
Our data demonstrate that the reduction in baroreflex sensitivity in older people is maintained during exercise and during post-exercise circulatory occlusion. Resetting of the baroreflex in the older subjects during moderate voluntary isometric calf exercise is largely the result of central command.
Carrington
Charlotte A
CA
School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. C.A.Carrington@bham.ac.uk
White
Michael J
MJ
D000328:Adult; D000375:Aging / Q000502:physiology*; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D004558:Electric Stimulation; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation; D009475:Neurons, Afferent / Q000502:physiology; D012044:Regression Analysis