Quantification of Impaired Cumulative Muscle Hemodynamics During Continuous Non‐Steady State Exercise and Recovery in Aging Humans

Aging is associated with impaired muscle blood flow during exercise; however, much of our understanding is derived from comparisons of steady state hemodynamics. In 8 young (22 ± 3 yrs) and 6 older (66 ± 5 yrs) adults, we continuously measured forearm blood flow (FBF; Doppler ultrasound) and calculated forearm vascular conductance (FVC; mean arterial pressure from finometry) during 3 min of rhythmic handgrip exercise at 10 and 20% maximum voluntary contraction (MVC; 1.5 min each) and 2 min of post‐exercise recovery. Two randomized, continuous non‐steady state exercise trials consisted of either 1.5 min at a low workload (10% MVC) immediately followed by 1.5 min at a high workload (20% MVC) (L2H) or vice versa (H2L). FBF and FVC were quantified in 3‐sec bins and area under the curve (AUC) was calculated throughout. In both exercise trials, FBF (~30‐40%) and FVC (~40‐50%) were reduced with age at the end of the first workload, and this persisted throughout the next workload transition and into recovery. When quantified as an absolute cumulative response over time in the L2H trial, the age‐related deficit in FBF increased from ~600 mL at 1.5 min to ~3000 mL at end recovery, and similar results were obtained for FVC (~900‐4400 mL/100mmHg). Similar trends were observed for the H2L trial, but the magnitude of the age‐related deficit was greater (FBF ~1500‐3800 mL; FVC ~2200‐5500 mL/100mmHg). We conclude that during non‐steady state exercise and recovery, the magnitude of FBF and FVC deficit with age increases over time, which may have implications for understanding muscle perfusion during activities of normal daily living in older adults. Support HL095573