Background. The purpose of this investigation was to determine the effects of age and fitness on tolerance to maximal lower body negative pressure (LBNP).Methods. Ten older fit (OF) [73.9 6 2 years; 39.0 6 2 mlÁkg À1 Ámin À1 (age and estimated VO 2 peak, respectively)], 10 older unfit (OU) (70.9 6 1 years; 27.1 6 2 mlÁkg À1 Ámin À1 ), 10 young fit (YF) (22.6 6 0.5 years; 57.1 6 2 mlÁkg À1 Ámin À1 ), and 10 young unfit (YU) (23.1 6 1 years; 41.1 6 2 mlÁkg À1 Ámin À1 ) participants underwent graded LBNP of À10 mmHg every 4 minutes to either presyncope or À100 mmHg.Results. Compared to the other groups, YF had an earlier increase in heart rate (À40 mmHg vs the last stage; YF vs OF, OU, and YU, respectively) and decline in stroke volume (À20 mmHg vs À40 mmHg; YF vs OF, OU, and YU, respectively). OU had a higher resting mean arterial pressure; this difference was maintained until the last stage. OF had an earlier decline in total peripheral conductance than the other groups (À20 mmHg vs À40 mmHg). Tolerance to maximal LBNP did not differ among the groups.Conclusions. Despite differences in the responses to submaximal LBNP, neither age nor cardiovascular fitness affect tolerance to maximal LBNP.
Background. The purpose of this investigation was to determine the effects of age and fitness on tolerance to maximal lower body negative pressure (LBNP). Methods. Ten older fit (OF) [73.9 6 2 years; 39.0 6 2 mlÁkg À1 Ámin À1 (age and estimated VO 2 peak, respectively)], 10 older unfit (OU) (70.9 6 1 years; 27.1 6 2 mlÁkg À1 Ámin À1), 10 young fit (YF) (22.6 6 0.5 years; 57.1 6 2 mlÁkg À1 Ámin À1), and 10 young unfit (YU) (23.1 6 1 years; 41.1 6 2 mlÁkg À1 Ámin À1) participants underwent graded LBNP of À10 mmHg every 4 minutes to either presyncope or À100 mmHg. Results. Compared to the other groups, YF had an earlier increase in heart rate (À40 mmHg vs the last stage; YF vs OF, OU, and YU, respectively) and decline in stroke volume (À20 mmHg vs À40 mmHg; YF vs OF, OU, and YU, respectively). OU had a higher resting mean arterial pressure; this difference was maintained until the last stage. OF had an earlier decline in total peripheral conductance than the other groups (À20 mmHg vs À40 mmHg). Tolerance to maximal LBNP did not differ among the groups. Conclusions. Despite differences in the responses to submaximal LBNP, neither age nor cardiovascular fitness affect tolerance to maximal LBNP.
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