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. CONCLUSION 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.