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The Journals of Gerontology Series A: Biological Sciences and Medical Sciences Advance Access originally published online on February 5, 2009
The Journals of Gerontology Series A: Biological Sciences and Medical Sciences 2009 64A(2):293-299; doi:10.1093/gerona/gln025
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© The Author 2009. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org.

A Forty-Year Follow-Up of the Dallas Bed Rest and Training Study: The Effect of Age on the Cardiovascular Response to Exercise in Men

Jonathan M. McGavock1,2, Jeffrey L. Hastings2, Peter G. Snell1, Darren K. McGuire1, Eric L. Pacini2, Benjamin D. Levine1,2 and Jere H. Mitchell1

1 Pauline and Adolph Weinberger Laboratory for Cardiopulmonary Research, Internal Medicine and the Donald W. Reynolds Cardiovascular Research Center, University of Texas Southwestern Medical Center, Dallas
2 Institute for Exercise and Environmental Medicine, Presbyterian Hospital, Dallas, Texas

Address correspondence to Benjamin D. Levine, MD, Institute for Exercise and Environmental Medicine, Presbyterian Hospital, 7232 Greenville Ave, Dallas, TX 75231. Email: benjaminlevine{at}texashealth.org


  Abstract

Background: In 1966, five 20-year-old men underwent a comprehensive physiological evaluation of the capacity for adaptation of the cardiovascular system in response to 3 weeks of bed rest and 8 weeks of heavy endurance training; these same participants were reevaluated before and after training at the age of 50. The aim of the present study was to reexamine these same men 40 years following the original assessments.

Methods and Results: In all three studies, minute ventilation and expired gases were analyzed during exercise testing with Douglas bag collection. Cardiac output (CO) was determined using the acetylene rebreathing technique. Compared with the original 30-year interval, the decline in maximal oxygen uptake (VO2max) (–11% vs –25%), maximal CO (+6% vs –11%), and maximal stroke volume (+10% vs –10%) were greater between 50 and 60 years of age. The annualized decline in VO2max (55 mL/min/y) between ages 50 and 60 was approximately fourfold higher than the decline between 20 and 50 years (12 mL/min/y).

Conclusions: In the original five participants of the Dallas Bed Rest and Training Study, VO2max declined after 40 years of living due to a balanced decrease in central and peripheral determinants of oxygen uptake. The rate of decline in VO2max and its components accelerated after the age of 50 years secondary to age and clinical comorbidities. The net proportional decline in VO2max for a period of 40 years of life was comparable with that experienced after 3 weeks of strict bed rest at the age of 20 (27% vs 26%, respectively).

Keywords Maximal oxygen uptake; Cardiac output; Arteriovenous oxygen difference; Longitudinal

Received: March 12, 2008; Accepted: July 27, 2008

Decision Editor: Luigi Ferrucci, MD, PhD


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