Assessment of Pulsatile Load During Lower Body Aerobic Exercise in Young and Older Adults

Abstract

Increased wave reflection magnitude (RM) and early return of reflected pressure waves augment pulsatile load, waste left ventricular effort, and are associated with cardiovascular events. Acute lower body aerobic exercise (AE) decreases RM and reflected wave transit time (RWTT) in young adults (YA). Due to age‐related changes in arterial structure and function, older adults (OA) experience an elevated RM and earlier RWTT at rest compared to YA. However, it is unknown how AE influences RM and RWTT in OA, and whether OA respond differently than YA.PURPOSEThe purpose of this study was to test the hypotheses that 1) RM and RWTT would be reduced during AE and 2) the reduction in RM would be attenuated in OA while the reduction in RWTT would be augmented in OA compared to YA.METHODSRadial artery pressure waveforms and aortic blood flow velocities were acquired at baseline and during light, moderate, and vigorous intensity AE on a supine cycle via applanation tonometry and echocardiography, respectively, in 20 YA (25±5 yrs) and 20 OA (66±4 yrs). Central pressure waveforms were synthesized from radial waves using a generalized transfer function. Pressure‐flow relations were analyzed offline to perform wave separation analysis. This provided a comprehensive assessment of ventricular‐arterial interactions for the determination of the relative amplitude and timing of forward (Pf) and backward (Pb) pressure waves, yielding RM (Pb/Pf) and RWTT.RESULTSAs expected, baseline RM was greater in OA (YA: 40±6 vs. OA: 49±6%, p<0.05) and RWTT was shorter in OA compared to YA (YA: 191±20 vs. OA: 140±18 ms, p<0.05). RM was decreased during all intensities of AE. However, the reduction in RM from baseline was different between YA and OA during light intensity AE (ΔYA: −12±8 vs. ΔOA: −17±7, p<0.05), trended toward being different during moderate AE (ΔYA: −12±10 vs. ΔOA: −18±7%, p=0.06), and was not different during vigorous AE (ΔYA: −15±6 vs. ΔOA: −18±6%, p>0.05). RWTT decreased during all intensities of AE. The reduction in RWTT from baseline was attenuated in OA compared to YA during light (ΔYA: −39±18 vs. ΔOA: −9±13ms, p<0.05), moderate (ΔYA: −51±18 vs. ΔOA: −11±17ms, p<0.05), and vigorous intensity AE (ΔYA: −57±25 vs. ΔOA: −19±17ms, p<0.05).CONCLUSIONRM decreased during AE, however, differences in ΔRM between YA and OA were exercise intensity dependent. Our results suggest a greater decrease in RM in OA compared to YA during light‐moderate intensity AE. Contrary to our hypothesis, there was an attenuated reduction in RWTT in OA compared to YA during all intensities of AE, which may be due to the OA reaching the floor in RWTT.Support or Funding InformationACSM Foundation Doctoral Student Research Grant and NIH grant P20 GM 113125