The Effect of Physical Activity on Passive Leg Movement-Induced Vasodilation with Age

Abstract

Introduction: Because of reduced nitric oxide (NO) bioavailability with age, passive leg movement (PLM)-induced vasodilation is attenuated in older sedentary subjects and, unlike the young subjects, cannot be augmented by posture-induced elevations in femoral perfusion pressure. However, whether vasodilator function assessed with PLM, and therefore NO bioavailability, is preserved in older individuals with greater physical activity and fitness is unknown.

Methods: PLM was performed on four subject groups: young sedentary (Y, 23 ± 1 yr, n = 12), old sedentary (OS, 73 ± 2 yr, n = 12), old active (OA, 71 ± 2 yr, n = 10), and old endurance trained (OT, 72 ± 1 yr, n = 10) in the supine and upright-seated posture. Hemodynamics were measured using ultrasound Doppler and finger photoplethysmography.

Results: In the supine posture, PLM-induced peak change in leg vascular conductance was significantly attenuated in the OS compared with the young subjects (OS = 4.9 ± 0.5, Y = 6.9 ± 0.7 mL·min·mm Hg) but was not different from the young in the OA and OT (OA = 5.9 ± 1.0, OT = 5.4 ± 0.4 mL·min·mm Hg). The upright-seated posture significantly augmented peak change in leg vascular conductance in all but the OS (OS = 4.9 ± 0.5, Y = 11.8 ± 1.3, OA = 7.3 ± 0.8, OT = 8.1 ± 0.8 mL·min·mm Hg), revealing a significant vasodilatory reserve capacity in the other groups (Y = 4.92 ± 1.18, OA = 1.37 ± 0.55, OT = 2.76 ± 0.95 mL·min·mm Hg).

Conclusions: As PLM predominantly reflects NO-mediated vasodilation, these findings support the idea that augmenting physical activity and fitness can protect NO bioavailability, attenuating the deleterious effects of advancing age on vascular function.

Conflict of interest statement

Competing Interest

None of the authors has any conflicts of interest.

Figures

Figure 1. Physical Activity and Fitness Levels

Average steps taken per day (A); Total daily physical activity (B, activity counts/min); both steps per day and total daily physical activity were assessed as the average from at least 7 days of accelerometry; Absolute (C, l/min) and relative (D, ml/kg/min) volume of oxygen consumed at peak exercise during a graded cycling test to volitional exhaustion. Young sedentary n = 12, old sedentary n = 12, old active n = 10, old endurance trained n = 10. # p < 0.05, significantly different from the young; § p < 0.05, significantly different from the old sedentary; † p < 0.05, significantly different from the old active. Values are mean ± SEM.

Figure 2. Passive Leg Movement (PLM)-Induced Changes in Leg Vascular Conductance in the Supine and Upright-Seated Posture with Age and Across Physical Activity and Fitness Levels

Second-by-second tracing of the change in leg vascular conductance (ml/min/mmHg) throughout 1 min of PLM in the supine (A) and upright-seated (B) postures; peak change in LVC from baseline (ΔLVCpeak, ml/min/mmHg) in the supine (C) and upright-seated (D) postures. Young sedentary n = 12, old sedentary n = 12, old active n = 10, old endurance trained n = 10. * p < 0.05, significantly different from the supine posture. # p < 0.05, significantly different from the young; § p < 0.05, significantly different from the old sedentary. Values are mean ± SEM.

Figure 3. Passive Leg Movement (PLM)-Induced Vasodilatory Reserve Capacity with Age and Across Physical Activity and Fitness Levels

The difference in the PLM-induced peak change in leg vascular conductance ( LVCpeak, ml/min/mmHg) between the supine and upright-seated posture (vasodilatory reserve capacity). Young sedentary n = 12, old sedentary n = 12, old active n = 10, old endurance trained n = 10. # p < 0.05, significantly different from the young; § p < 0.05, significantly different from the old sedentary. Values are mean ± SEM.

Figure 4. Passive Leg Movement (PLM)-Induced Rapid Vasodilation in the Supine and Upright-Seated Posture with Age and Across Physical Activity and Fitness Levels

The rate of increase in the leg vascular conductance (LVC, ml/min/mmHg) over time was determined for the first 9 s of PLM in the supine (A) and upright-seated (B) postures; C, the difference in the slope between the supine and upright-seated posture (rapid vasodilatory reserve capacity, ml/min/mmHg/s). Young sedentary n = 12, old sedentary n = 12, old active n = 10, old endurance trained n = 10. * p < 0.05, significantly different from the supine posture. # p < 0.05, significantly different from the young; § p < 0.05, significantly different from the old sedentary. Values are mean ± SEM.