Submitted on September 30, 2002
Accepted on January 4, 2003
Leg blood flow during submaximal cycle ergometry is not reduced in healthy older normally active men
David N Proctor1*, Sean C Newcomer1, Dennis W Koch2, Khoi U Le1, David A MacLean3, and Urs A Leuenberger3
1 Noll Physiological Research Center, The Pennsylvania State University, University Park, PA, USA; Department of Kinesiology, The Pennsylvania State University, University Park, PA, USA
2 Noll Physiological Research Center, The Pennsylvania State University, University Park, PA, USA
3 Division of Cardiology, Department of Medicine, The Pennsylvania State University College of Medicine, Hershey, PA, USA
* To whom correspondence should be addressed. E-mail: dnp3{at}psu.edu.
The purpose of the present study was to test the hypothesis that leg blood flow responses during submaximal cycle ergometry are reduced with age in healthy normally active men. Eleven younger (20-25 yr) and eight older (62-73 yr) normotensive, non-endurance trained men performed both graded and constant-load bouts of leg cycling at the same absolute and relative (% of VO2peak) exercise intensities while leg blood flow (femoral vein thermodilution), mean arterial pressure (MAP, radial artery), cardiac output (acetylene rebreathing), blood O2 contents, and plasma catecholamines were measured. Leg blood flow responses at the same absolute submaximal power outputs (20 to 100 watts) and at a fixed systemic O2 demand (1.1 L/min) did not differ between groups (p=0.14 to 0.19), despite lower absolute levels of cardiac output in the older men (p<0.05). MAP at the same absolute power outputs was 8-12 mmHg higher (p<0.05) in the older men, but calculated leg vascular conductance responses (leg blood flow/MAP) were identical in the two groups (p>0.9). At the same relative intensity (60% VO2peak), leg norepinephrine spillover rates were ~5-fold higher in the older men (p=0.21). Exercise-induced increases in leg (a-v) O2 difference were identical between groups (p>0.9), since both arterial and venous O2 contents were lower in the older vs. younger men. These results suggest that the ability to augment active limb blood flow and O2 extraction during submaximal large muscle mass exercise is not impaired, but is well preserved with age in healthy men who are normally active.
