Whole body passive heating versus dynamic lower body exercise: A comparison of peripheral hemodynamic profiles

Passive heating has emerged as a therapeutic intervention for the treatment and prevention of cardiovascular disease. Like exercise, heating increases peripheral artery blood flow and shear rate which is thought to be a primary mechanism underpinning endothelium mediated vascular adaptation. However, few studies have compared the increase in arterial blood flow and shear rate between dynamic exercise and passive heating. In a fixed crossover design study, 15 moderately trained healthy participants (25.6 ± 3.4 years) (5 female) underwent 30 minutes of whole body passive heating (42 °C bath), followed on a separate day by 30 minutes of semi-recumbent stepping exercise performed at two workloads corresponding to the increase in cardiac output (Qc) (Δ3.72 l∙min-1) and heart rate (HR) (Δ38 bpm) recorded at the end of passive heating. Results: At the same Qc (Δ3.72 l∙min-1 vs 3.78 l∙min-1), femoral artery blood flow (1599 ml/min vs 1947 ml/min) (p=0.596) and shear rate (162 s -1 vs 192 s-1) (p=0.471) measured by ultrasonography were similar between passive heating and stepping exercise. However, for the same HR matched intensity, femoral blood flow (1599 ml·min-1 vs 2588 ml·min-1) and shear rate (161s-1 vs 271s-1) were significantly greater during exercise, compared with heating (both P=<0.001). The results indicate that, for moderately trained individuals, passive heating increases common femoral artery blood flow and shear rate similar to low intensity continuous dynamic exercise (29% VO2max), however exercise performed at a higher intensity (53% VO2max) results in significantly larger shear rates towards the active skeletal muscle.

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Ultrasound Doppler estimates of femoral artery blood flow during dynamic knee extensor exercise in humans

Journal of Applied Physiology ◽

10.1152/jappl.1997.83.4.1383 ◽

1997 ◽

Vol 83 (4) ◽

pp. 1383-1388 ◽

Cited By ~ 188

Author(s):

G. Rådegran

Keyword(s):

Blood Flow ◽

Femoral Artery ◽

Coefficient Of Variation ◽

Knee Extensor ◽

Dynamic Exercise ◽

Artery Blood Flow ◽

Ultrasound Doppler ◽

Femoral Artery Blood Flow ◽

Human Limb ◽

Exercise In Humans

Rådegran, G. Ultrasound Doppler estimates of femoral artery blood flow during dynamic knee extensor exercise in humans. J. Appl. Physiol.83(4): 1383–1388, 1997.—Ultrasound Doppler has been used to measure arterial inflow to a human limb during intermittent static contractions. The technique, however, has neither been thoroughly validated nor used during dynamic exercise. In this study, the inherent problems of the technique have been addressed, and the accuracy was improved by storing the velocity tracings continuously and calculating the flow in relation to the muscle contraction-relaxation phases. The femoral arterial diameter measurements were reproducible with a mean coefficient of variation within the subjects of 1.2 ± 0.2%. The diameter was the same whether the probe was fixed or repositioned at rest (10.8 ± 0.2 mm) or measured during dynamic exercise. The blood velocity was sampled over the width of the diameter and the parabolic velocity profile, since sampling in the center resulted in an overestimation by 22.6 ± 9.1% ( P< 0.02). The femoral arterial Doppler blood flow increased linearly ( r = 0.997, P < 0.001) with increasing load [Doppler blood flow = 0.080 ⋅ load (W) + 1.446 l/min] and was correlated positively with simultaneous thermodilution venous outflow measurements ( r = 0.996, P < 0.001). The two techniques were linearly related (Doppler = thermodilution ⋅ 0.985 + 0.071 l/min; r = 0.996, P < 0.001), with a coefficient of variation of ∼6% for both methods.

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Sympathetic vasomotor control does not explain the change in femoral artery shear rate pattern during arm-crank exercise

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00686.2008 ◽

2009 ◽

Vol 296 (1) ◽

pp. H180-H185 ◽

Cited By ~ 13

Author(s):

Dick H. J. Thijssen ◽

Daniel J. Green ◽

Sjoerd Steendijk ◽

Maria T. E. Hopman

Keyword(s):

Blood Flow ◽

Shear Rate ◽

Flow Pattern ◽

Femoral Artery ◽

Peripheral Resistance ◽

Retrograde Flow ◽

Artery Blood Flow ◽

Femoral Artery Blood Flow ◽

Exercise Induced ◽

Retrograde Shear

During lower limb exercise, blood flow through the resting upper limbs exhibits a change characterized by increased anterograde flow during systole, but also large increases in retrograde diastolic flow. One explanation for the retrograde flow is that increased sympathetic nervous system (SNS) tone and concomitant increased peripheral resistance generate a rebound during diastole. To examine whether the SNS contributes to retrograde flow patterns, we measured femoral artery blood flow during arm-crank exercise in 10 healthy men (31 ± 4 yr) and 10 spinal cord-injured (SCI) subjects who lack sympathetic innervation in the legs (33 ± 5 yr). Before, and every 5 min during 25-min arm-crank exercise at 50% maximal capacity, femoral artery blood flow and peak anterograde and retrograde shear rate were assessed using echo Doppler sonography. Femoral artery baseline blood flow was significantly lower in SCI compared with controls. Exercise increased femoral artery blood flow in both groups (ANOVA, P < 0.05), whereas leg vascular conductance did not change during exercise in either group. Mean shear rate was lower in SCI than in controls ( P < 0.05). Peak anterograde shear rate was higher in SCI than in controls ( P < 0.05), whereas peak retrograde shear rate did not differ between groups. Arm-crank exercise induced an increase in peak anterograde and retrograde shear rate in the femoral artery in controls and SCI subjects ( P < 0.05). This suggests that the SNS is not obligatory to change the flow pattern in inactive regions during exercise. Local mechanisms may play a role in the arm-crank exercise-induced changes in flow pattern in the femoral artery.

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Kinetics of V̇o2 and femoral artery blood flow during heavy-intensity, knee-extension exercise

Journal of Applied Physiology ◽

10.1152/japplphysiol.00707.2004 ◽

2005 ◽

Vol 99 (2) ◽

pp. 683-690 ◽

Cited By ~ 14

Author(s):

Nicole D. Paterson ◽

John M. Kowalchuk ◽

Donald H. Paterson

Keyword(s):

Blood Flow ◽

Femoral Artery ◽

Time Course ◽

Slow Component ◽

Knee Extension ◽

Artery Blood Flow ◽

Phase 2 ◽

Femoral Artery Blood Flow ◽

Knee Extension Exercise ◽

Kinetics Of

It has been suggested that, during heavy-intensity exercise, O2 delivery may limit oxygen uptake (V̇o2) kinetics; however, there are limited data regarding the relationship of blood flow and V̇o2 kinetics for heavy-intensity exercise. The purpose was to determine the exercise on-transient time course of femoral artery blood flow (Q̇leg) in relation to V̇o2 during heavy-intensity, single-leg, knee-extension exercise. Five young subjects performed five to eight repeats of heavy-intensity exercise with measures of breath-by-breath pulmonary V̇o2 and Doppler ultrasound femoral artery mean blood velocity and vessel diameter. The phase 2 time frame for V̇o2 and Q̇leg was isolated and fit with a monoexponent to characterize the amplitude and time course of the responses. Amplitude of the phase 3 response was also determined. The phase 2 time constant for V̇o2 of 29.0 s and time constant for Q̇leg of 24.5 s were not different. The change (Δ) in V̇o2 response to the end of phase 2 of 0.317 l/min was accompanied by a ΔQ̇leg of 2.35 l/min, giving a ΔQ̇leg-to-ΔV̇o2 ratio of 7.4. A slow-component V̇o2 of 0.098 l/min was accompanied by a further Q̇leg increase of 0.72 l/min (ΔQ̇leg-to-ΔV̇o2 ratio = 7.3). Thus the time course of Q̇leg was similar to that of muscle V̇o2 (as measured by the phase 2 V̇o2 kinetics), and throughout the on-transient the amplitude of the Q̇leg increase achieved (or exceeded) the Q̇leg-to-V̇o2 ratio steady-state relationship (ratio ∼4.9). Additionally, the V̇o2 slow component was accompanied by a relatively large rise in Q̇leg, with the increased O2 delivery meeting the increased V̇o2. Thus, in heavy-intensity, single-leg, knee-extension exercise, the amplitude and kinetics of blood flow to the exercising limb appear to be closely linked to the V̇o2 kinetics.

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