Effects of age and fitness on tolerance to lower body negative pressure.
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 +/- 2 years; 39.0 +/- 2 ml.kg(-1).min(-1) (age and estimated VO(2)peak, respectively)], 10 older unfit (OU) (70.9 +/- 1 years; 27.1 +/- 2 ml.kg(-1).min(-1)), 10 young fit (YF) (22.6 +/- 0.5 years; 57.1 +/- 2 ml.kg(-1).min(-1)), and 10 young unfit (YU) (23.1 +/- 1 years; 41.1 +/- 2 ml.kg(-1).min(-1)) participants underwent graded LBNP of -10 mmHg every 4 minutes to either presyncope or -100 mmHg.


RESULTS
Compared to the other groups, YF had an earlier increase in heart rate (-40 mmHg vs the last stage; YF vs OF, OU, and YU, respectively) and decline in stroke volume (-20 mmHg vs -40 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 (-20 mmHg vs -40 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.
Department of Health and Human Performance, Iowa State University, Ames, Iowa, USA. juliane@siu.edu
Juliane P
JP
Hernandez
Amruta
A
Karandikar
Warren D
WD
Franke
D000328:Adult; D000367:Age Factors; D000368:Aged; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008150:Lower Body Negative Pressure; D008297:Male; D008875:Middle Aged; D010809:Physical Fitness / Q000502:physiology*; D013318:Stroke Volume / Q000502:physiology; D013575:Syncope / Q000209:etiology