ArticlePDF Available

Assessment of voluntary rhythmic muscle contraction-induced exercising blood flow variability measured by Doppler ultrasound

Authors:

Abstract and Figures

Given recent technological developments, ultrasound Doppler can provide valuable measurements of blood velocity/flow in the conduit artery with high temporal resolution. In human-applied science such as exercise physiology, hemodynamic measurements in the conduit artery is commonly performed by blood flow feeding the exercising muscle, as the increase in oxygen uptake (calculated as a product of arterial blood flow to the exercising limb and the arterio-venous oxygen difference) is directly proportional to the work performed. The increased oxygen demand with physical activity is met through a central mechanism, an increase in cardiac output and blood pressure, as well as a peripheral mechanism, an increase in vascular conductance and oxygen extraction (a major part of the whole exercising muscles) from the blood. The increase in exercising muscle blood flow in relation to the target workload (quantitative response) may be one indicator in circulatory adjustment for the activity of muscle metabolism. Therefore, the determination of local blood flow dynamics (potential oxygen supply) feeding repeated (rhythmic) muscle contractions can contribute to the understanding of the factors limiting work capacity including, for instance, muscle metabolism, substance utilization and magnitude of vasodilatation in the exercising muscle. Using non-invasive measures of pulsed Doppler ultrasound, the validity of blood velocity/flow in the forearm or lower limb conduit artery feeding to the muscle has been previously demonstrated during rhythmic muscle exercise. For the evaluation of exercising blood flow, not only muscle contraction induced internal physiological variability, or fluctuations in the magnitude of blood velocity due to spontaneous muscle contraction and relaxation induced changes in force curve intensity, superimposed in cardiac beat-by-beat, but also the alterations in the blood velocity (external variability) due to a temporary sudden change in the achieved workload, compared to the target workload, should be considered. Furthermore, a small amount of inconsistency in the voluntary muscle contraction force at each kick seems to be unavoidable, and may influence exercising muscle blood flow, although subjects attempt to perform precisely similar repeated voluntary muscle contractions at target workload (muscle contraction force). This review presents the methodological considerations for the variability of exercising blood velocity/flow in the limb conduit artery during dynamic leg exercise assessed by pulsed Doppler ultrasound in relation to data previously reported in original research.
Relationship between net-femoral arterial blood flow (FBF) and target workload during dynamic knee extensor exercise. The relationship between FBF and target workload was positive and linear at 30 cpm (r = 0.997, P < 0.01, n = 4) and 60 cpm (r = 0.999, P < 0.05, n = 3), respectively. The value of FBF for one subject was the average value of 60 samplings at each session. Furthermore, the target workload value in each individual subject was determined by averaging values of 60 samplings of the achieved workloads at each session. Both FBF and target workload were obtained from average values of all 9 subjects. Regression equations are indicated as follows: FBF (l/min) = 1.71 + 0.083 × target workload at 30 cpm (solid line): FBF (l/min) = 1.52 + 0.098 × target workload at 60 cpm (short dotted line). These data are in close agreement with the findings of Rådegran [6]: FBF (l/min) = 1.317 + 0.084 × target workload at 60 cpm, long dotted line. The difference in absolute FBF was approximately 0.5 l/min between the present FBF data and previous reports at 60 cpm by Rådegran [6]. This difference may be due to the subjects' characteristics, such as muscle strength variations and that they worked at different percentages of the maximum voluntary knee contraction force. However, the slope of the regression line in the present study is similar to previous findings. cpm, contractions per minute. Data are expressed as means  standard error. Figure adapted from Osada and Rådegran [32], reproduced with permission from John Wiley & Sons Ltd.
… 
Content may be subject to copyright.
Open Journal of Molecular and Integrative Physiology, 2013, 3, 158-165 OJMIP
http://dx.doi.org/10.4236/ojmip.2013.34021 Published Online November 2013 (http://www.scirp.org/journal/ojmip/)
Assessment of voluntary rhythmic muscle
contraction-induced exercising blood flow variability
measured by Doppler ultrasound
Takuya Osada1,2*, Bengt Saltin2, Göran Rådegran2,3,4
1Department of Sports Medicine for Health Promotion, Tokyo Medical University, Tokyo, Japan
2The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
3The Clinic for Heart Failure and Valvular Disease, Skåne University Hospital, Lund, Sweden
4Department of Cardiology, Clinical Sciences, Lund University, Lund, Sweden
Email: *DENTACMAC@aol.com
Received 25 September 2013; revised 25 October 2013; accepted 2 November 2013
Copyright © 2013 Takuya Osada et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
Given recent technological developments, ultrasound
Doppler can provide valuable measurements of blood
velocity/flow in the conduit artery with high temporal
resolution. In human-applied science such as exercise
physiology, hemodynamic measurements in the con-
duit artery is commonly performed by blood flow
feeding the exercising muscle, as the increase in oxy-
gen uptake (calculated as a product of arterial blood
flow to the exercising limb and the arterio-venous
oxygen difference) is directly proportional to the
work performed. The increased oxygen demand with
physical activity is met through a central mechanism,
an increase in cardiac output and blood pressure, as
well as a peripheral mechanism, an increase in vas-
cular conductance and oxygen extraction (a major
part of the whole exercising muscles) from the blood.
The increase in exercising muscle blood flow in rela-
tion to the target workload (quantitative response) may
be one indicator in circulatory adjustment for the ac-
tivity of muscle metabolism. Therefore, the determi-
nation of local blood flow dynamics (potential oxygen
supply) feeding repeated (rhythmic) muscle contrac-
tions can contribute to the understanding of the fac-
tors limiting work capacity including, for instance,
muscle metabolism, substance utilization and magni-
tude of vasodilatation in the exercising muscle. Using
non-invasive measures of pulsed Doppler ultrasound,
the validity of blood velocity/flow in the forearm or
lower limb conduit artery feeding to the muscle has
been previously demonstrated during rhythmic mus-
cle exercise. For the evaluation of exercising blood
flow, not only muscle contraction induced internal
physiological variability, or fluctuations in the mag-
nitude of blood velocity due to spontaneous muscle
contraction and relaxation induced changes in force
curve intensity, superimposed in cardiac beat-by-beat,
but also the alterations in the blood velocity (external
variability) due to a temporary sudden change in the
achieved workload, compared to the target workload,
should be considered. Furthermore, a small amount
of inconsistency in the voluntary muscle contraction
force at each kick seems to be unavoidable, and may
influence exercising muscle blood flow, although sub-
jects attempt to perform precisely similar repeated
voluntary muscle contractions at target workload
(muscle contraction force). This review presents the
methodological considerations for the variability of
exercising blood velocity/flow in the limb conduit ar-
tery during dynamic leg exercise assessed by pulsed
Doppler ultrasound in relation to data previously
reported in original research.
Keywords: Exercising Blood Flow; Doppler Ultrasound;
Muscle Contraction; Blood Flow Alterations
1. INTRODUCTION
In integrated and applied human physiology, blood flow
plays a key role, as oxygen transport via blood flow to
the working muscles is crucial for exercise capacity. Fur-
thermore, the magnitude of blood flow in the exercising
muscle may also be related to the blood volume redistri-
bution, via systemic circulation, as seen in previous
studies focused on cardiovascular regulation in humans
[1,2]. The oxygen uptake is evaluated by the product of
*Corresponding author.
OPEN ACCESS
T. Osada et al. / Open Journal of Molecular and Integrative Physiology 3 (2013) 158-165 159
cardiac output and arterio-venous oxygen concentration
difference. Consequently peripheral conduit arterial
blood flow to the working muscle is one indicator of the
metabolic demand in local large muscle groups [3].
Moreover, detecting utilization in the leg requires com-
prehensive leg blood flow and arterio-venous substance
concentration difference [4,5].
Peripheral circulatory changes during exercise corre-
spond to the stress imposed on the cardiovascular system
[6,7]. Cardiac output increases with increasing exercise
intensity along with enhanced skeletal muscle vasodila-
tation and muscle pumping in the exercising muscle. As
the perfusion in the active muscle is one further indicator
of oxygen delivery to the muscles, blood velocity and
flow in the feeding conduit arteries to working skeletal
muscle may also give valuable information regarding the
hemodynamic response to exercise (particularly for large
muscle groups in the upper or lower limbs).
Recent advanced ultrasound Doppler instruments can
provide valuable measurements of arterial blood flow
with high temporal resolution in the cardiovascular sys-
tem. The determination of blood velocity in the feeding
conduit artery at rest and during rhythmic muscle con-
tractions during exercise has an impact on transient
changes in hemodynamics [6,8,9]. The investigation of
the blood flow supply due to continuous muscle contrac-
tions may require the evaluation of the effect of physical
activity on regulation among central and peripheral
hemodynamics.
Since one of the advantages of Doppler ultrasound is
that it can provide an evaluation of high temporal resolu-
tion blood velocity, the oscillation of blood velocity may
be detected at rest as a measure of heart beat and blood
pressure. During repeated muscle contractions of exer-
cise, these oscillations are even more pronounced, as
they are also influenced by intramuscular pressure varia-
tions. Therefore, the measurement of valid blood velocity
should be done carefully to account for the influence of
changes in the voluntary muscle contraction force in in-
ducing physiological blood velocity fluctuation (internal
variability), as well as the alterations in the blood veloc-
ity (external variability) due to a temporary sudden chan-
ge in the achieved workload compared to the target
workload.
Acknowledging the above mentioned variability in the
conduit arterial blood velocity, feeding into voluntary
rhythmic muscle contractions is valuable information for
the determination of exercising blood flow under various
muscle contraction intensities. The purpose of the present
review is therefore to summarize the physiological con-
siderations of the variability of the exercising blood ve-
locity/flow in the limb conduit artery during thigh mus-
cle kicking exercise (dynamic knee extensor exercise
model) assessed by Doppler ultrasound.
The paper is organized as follows: 1) Muscle contrac-
tion-induced physiological (internal) variations in blood
velocity during rhythmic muscle contractions, 2) Valida-
tion of exercising blood flow during rhythmic muscle
contractions and 3) Changes in exercising blood flow
(external variations) due to spontaneous changes of mus-
cle contraction force (workload) compared to target in-
tensity.
2. METHODOLOGICAL
CONSIDERATIONS
2.1. Exercise Model
Determinations of blood flow to contractile muscles are
the primary focus of the present review. Whole body
exercise methods such as walking and running on a
treadmill do not easily allow measurement of upper- and
lower-limb blood flow using Doppler ultrasound as mo-
tion artifacts are present. There is also difficulty in fixing
the ultrasound Doppler probe. Whole lower limb muscle
blood flow may be measured using the one-legged, re-
peated kicking (dynamic knee-extensor) exercise model
described by Andersen and Saltin [10]. In this exercise
model, the subject performs leg kicking while the leg is
passively returned by the cycle ergometer. Consequently,
the work is confined to the quadriceps muscle group and
the model allows stable measurements of femoral arterial
blood velocity using Doppler ultrasound because the
subject is seated (Figure 1). Therefore, all hemodynamic
data described in this review are from one-legged re-
peated kicking (dynamic knee-extensor) exercise with
the activation of the large thigh muscle group.
2.2. Hemodynamic Measurements
Ultrasound instrumentation: The measurements were
performed using a Doppler ultrasound instrument (Model
CFM 800, Vingmed Sound, Horten, Norway) equipped
with an annular phased array transducer (Vingmed
Sound) probe (11.5-mm diameter). The imaging fre-
quency was 7.5 MHz and the Doppler frequencies varied
between 4.0 and 6.0 MHz (high-pulsed repetition fre-
quency mode, 4 - 36 kHz). Blood velocity was measured
Figure 1. One-legged dynamic kicking (knee extensor) exer-
cise as a model of rhythmic thigh muscle contractions.
Copyright © 2013 SciRes. OPEN ACCESS
T. Osada et al. / Open Journal of Molecular and Integrative Physiology 3 (2013) 158-165
160
with the probe at the lowest possible insonation angle
and always <60˚ [11]. The mean value of the insonation
angle was ~50˚, which remained constant throughout the
experiments for each individual. The probe position was
stable and the sample volume was precisely positioned in
the center of the vessel and adjusted to cover the diame-
ter width of the vessel.
Blood velocity, vessel diameter and blood flow: The
measurements of blood velocity and blood flow in the
femoral artery using Doppler ultrasound has previously
been validated and shown to produce accurate absolute
values both at rest and during leg exercise such as
rhythmical thigh muscle contractions [6,8,9,12,13]. Com-
pared with thermodilution, the high temporal resolution
of pulsed Doppler ultrasound additionally enables con-
tinuous measurement of blood velocity throughout the
knee-extensor exercise [6-9,14,15].
The angle-corrected, time and space-averaged, and
amplitude-weighted mean blood velocities were meas-
ured. Mean blood velocity was defined by averaging the
mean blood velocity trace, including both negative and
positive values [6,7]. The blood velocity parameter was
measured in relation to the blood pressure curve. The site
of blood velocity and vessel diameter measurements in
the femoral artery was distal to the inguinal ligament but
above the bifurcation into the branch of the superficial
and deep femoral artery. This location minimizes turbu-
lence from the femoral bifurcation and the influence of
blood flow from the inguinal region. In addition, the ar-
terial diameter is not affected by the contractions and
relaxations at this site, located proximal to the muscle.
The blood velocity measurements were performed
when steady-state had been reached after 3 min of one-
legged, dynamic knee extensor exercise, as previously
described [6,13,14]. The systolic and diastolic diameters
of the femoral artery were measured on a monitor rela-
tive to the electromyography at rest. The mean vessel
diameter was calculated in relation to the temporal dura-
tion of the blood pressure curve as; [(systolic vessel di-
ameter value × 1/3) + (diastolic vessel diameter value ×
2/3)] [6]. The diameters were measured under perpen-
dicular insonation at rest before exercise. The value of
the vessel diameter at rest (pre-exercise) was used to
calculate femoral arterial blood flow during rest and
during one-legged, dynamic knee extensor exercise,
since the diameter does not vary between rest and steady-
state exercise [1,6,12,16-18]. Steady-state one-legged
blood flow was calculated by multiplying the cross-sec-
tional area [Area = π × (vessel diameter/2)2] of the
femoral artery, with the angle corrected, time and space-
averaged, and amplitude (signal intensity) weighted
mean-blood velocity, where blood flow = mean-blood
velocity × cross-sectional area. Thus, the changes in
blood flow dynamics were basically parallel to the
changes in blood velocity.
Muscle force and work rate: Kicking muscle force
was measured using a strain gauge. Variations in muscle
force were taken to represent oscillations in intramuscu-
lar pressure, as these parameters have been shown to
temporally correlate closely to each other during dy-
namic knee extensor exercise [6,14,19]. The external
workload (work rate) was calculated according to the
knee extensor ergometer model [10,20], defined as: ex-
ternal workload (watt) = [contraction frequency (contrac-
tion per minute, cpm)/60 s] × [distance of one knee ex-
tensor revolution (6 m)] × [load (kg) × 9.81 (m/s2)]. The
specific loads applied were 0.333, 0.667, 1.0 and 1.333
kg at 10, 20, 30 and 40 watt, respectively, at 30 cpm; and
0.167, 0.333, 0.5 and 0.667 kg at 10, 20, 30 and 40 watt
at 60 cpm.
The external workload was evaluated by integrating
delta dP during the muscle contraction phase, where dP
(to time integral) = dF[N]i × R × Sin[alpha]i × revolution
per minute/60, were determined for each knee extensor
kicking session. The external workload = integral of dP
from time integral = 0 (where alpha = 0) to time integral
= x (where alpha = pi); dF[N]i, force (in Newtons) on the
kicking arm transducer to time integral; R, Length of
pedal arm in meters; Sin[alpha]i, Sin to horizontal angle
to time integral; revolution per minute, actual angular
velocity in rounds per minute to time integral; and
“dF[N]i × R × Sin[alpha]i” is the delta torque [Nm] to
time integral. The achieved workload determined by this
method was displayed in real time on a monitor visible to
the subjects, to maintain the target workload during dy-
namic knee extensor exercise.
3. EVALUATION OF EXERCISING
MUSCLE BLOOD FLOW
3.1. Muscle Contraction-Induced Physiological
Variations in Blood Velocity during
Rhythmic Muscle Contractions
Continuous recordings can clearly determine the magni-
tude of the physiological variability in blood velocity by
the contraction-relaxation-induced variations in muscle
force, and consequently the intramuscular pressure varia-
tions, along with the superimposed influence of the blood
pressure, as well as the tonic influence of the state of
vasodilatation [6,13,21]. The high intramuscular pressure
during muscle contractions may consequently temporar-
ily reduce or even reverse the blood velocity, depending
on the relationship between the intramuscular- and arte-
rial blood pressure. The major extent of the blood veloc-
ity and flow consequently occurs during the muscle re-
laxation phase [6,13,22]. Blood velocity fluctuated in
relation to the state of vasodilatation and the muscle con-
traction-relaxation duty cycles, indicated by the oscilla-
Copyright © 2013 SciRes. OPEN ACCESS
T. Osada et al. / Open Journal of Molecular and Integrative Physiology 3 (2013) 158-165 161
tions in muscle force.
In general, the blood velocity increased to its highest
value at the systolic blood pressure phase during muscle
relaxation, and significantly decreased to its lowest value
at the diastolic blood pressure phase during muscle con-
traction (Figure 2). The blood velocity showed an inter-
mediate value at the systolic blood pressure phase during
muscle contraction and at the diastolic blood pressure
phase during muscle relaxation, respectively. The blood
velocity curve was furthermore retrograde in the diastolic
blood pressure phase during muscle contraction.
In Figure 3, the limited view of blood velocity profile
in relation to single muscle contraction-relaxation and
single cardio systolic-diastolic beat, as well as the blood
velocities during the systolic and diastolic phases were
found continuously in parallel with the blood pressure
curve during the muscle contraction and muscle relaxa-
tion phases determined from the electromyography and
the muscle force curve.
Four variations in the coupling between the blood
Time (sec)
Figure 2. Continuous recording of blood velocity in the
femoral artery, blood pressure and thigh muscle force during
steady-state one-legged dynamic kicking (knee extensor) ex-
ercise at 20 watts and 60 contractions per minute. The letters
depicted indicate; A: Muscle contraction at systolic blood
pressure phase, B: Muscle contraction at diastolic blood pres-
sure phase, C: Muscle relaxation at systolic blood pressure
phase, D: Muscle relaxation at diastolic blood pressure phase.
During rhythmic exercise, the peak thigh muscle force was
seen over or under target work load. The higher or lower
achieved muscle force (workload) may influence blood flow
values in Figures 5 and 6. Figure adapted from Osada and
Rådegran [21], reproduced with permission from Edizioni
Minerva Medica.
Time (sec)
Figure 3. Blood velocity profile for the systolic and diastolic
phases during the muscle contraction and muscle relaxation
phases at 20 watts and 60 contractions per minute. The arrows
down and up indicate the influence of the blood velocity, de-
pending on the magnitude of, and temporal relation between,
the muscle force (intramuscular pressure), the electromyog-
raphy (EMG) and the blood pressure, respectively. These pan-
els (A-D) are expanded by the part of blood velocity profile
corresponding to them in Figure 2. Figure adapted from Osada
and Rådegran [22], reproduced with permission from The
Physiological Society of Japan.
pressure curve and the state of muscle contraction and
relaxation were indicated; the systolic phase during mus-
cle contraction, the diastolic phase during muscle con-
traction, the systolic phase during muscle relaxation, and
the diastolic phase during muscle relaxation. The forma-
tion of the blood velocity profile and flow was influ-
enced by the intramuscular pressure, as indicated by the
muscle force curve, and the superimposed influence of
blood pressure in relation to the systolic and diastolic
phases. The magnitude of blood flow value measured
against the 4 variations indicates the large difference in
work rates during the muscle relaxation phase and those
of the muscle contraction phase at systolic and diastolic
points, respectively.
3.2. Validation of Exercising Blood Flow during
Rhythmic Muscle Contractions
In previous reports, peripheral hemodynamic measure-
ments have been performed using the thermodilution
technique for leg blood flow during dynamic knee-ex-
tensor exercise [10]. However, this invasive technique
Copyright © 2013 SciRes. OPEN ACCESS
T. Osada et al. / Open Journal of Molecular and Integrative Physiology 3 (2013) 158-165
162
has the limitation of poor time resolution of blood flow.
Several other techniques have previously been developed
that enable estimates to be made of arterial inflow, ve-
nous outflow, and local blood flow within a muscle
[23-29]. Whereas many of the techniques are impaired
by different methodological limitations, the indicator
thermodilution and the ultrasound Doppler method have
both been found to give repeatable measurements of the
same magnitude during both rest and dynamic knee ex-
tensor exercise [6,30] (Figure 4).
Figure 4. Relationship between net-femoral arterial blood
flow (FBF) and target workload during dynamic knee
extensor exercise. The relationship between FBF and target
workload was positive and linear at 30 cpm (r = 0.997, P <
0.01, n = 4) and 60 cpm (r = 0.999, P < 0.05, n = 3), res-
pectively. The value of FBF for one subject was the average
value of 60 samplings at each session. Furthermore, the
target workload value in each individual subject was deter-
mined by averaging values of 60 samplings of the achieved
workloads at each session. Both FBF and target workload
were obtained from average values of all 9 subjects. Re-
gression equations are indicated as follows: FBF (l/min) =
1.71 + 0.083 × target workload at 30 cpm (solid line): FBF
(l/min) = 1.52 + 0.098 × target workload at 60 cpm (short
dotted line). These data are in close agreement with the
findings of Rådegran [6]: FBF (l/min) = 1.317 + 0.084 ×
target workload at 60 cpm, long dotted line. The difference
in absolute FBF was approximately 0.5 l/min between the
present FBF data and previous reports at 60 cpm by
Rådegran [6]. This difference may be due to the subjects’
characteristics, such as muscle strength variations and that
they worked at different percentages of the maximum volun-
tary knee contraction force. However, the slope of the re-
gression line in the present study is similar to previous
findings. cpm, contractions per minute. Data are expressed
as means standard error. Figure adapted from Osada and
Rådegran [32], reproduced with permission from John
Wiley & Sons Ltd.
There is a positive linear relationship between leg
blood flow in femoral artery and target work rate (10, 20,
30 and 40 watts) in relation to rhythmic thigh muscle
contractions at 30 and 60 contractions per minute (Fig-
ure 4). With the rapid increase in energy requirements
during exercise, equally rapid circulatory adjustments are
essential in order to meet the increased need for oxygen
and nutrients by the exercising muscle. In addition,
thermodilution blood flow measurements obtained under
similar experimental conditions by Andersen and Saltin
[10] are closely related to those obtained by Doppler
ultrasound. Thus, blood flow measured by Doppler ul-
trasound is valid not only at rest but also during incre-
mental one-legged dynamic knee extensor exercise.
The Doppler technique can be used to differentiate
between physiological and methodological variations in
flow, as well as detect rapid changes in flow induced by
exercise (dynamic or static), different metabolic states
(muscle contraction intensity or frequency), or any other
type of vasodilatation such as the reperfusion period after
arterial occlusion or infusion of a vasodilator substance.
3.3. Changes in Blood Flow Due to Spontaneous
Changes of Workload
Femoral arterial blood flow during steady-state rhythmic
thigh muscle contractions increases linearly with incre-
mental target workloads (work rates) [6,7,9,12,31]. This
implies that enhanced vasodilatation is elicited in relation
to the increased average muscle force, exerted at higher
workloads, to meet the elevated metabolic activity (Fig-
ure 4). However, these blood flow values are a mean of
steady-state exercising blood flow measurements, and
temporary muscle contraction-induced blood flow varia-
tions may therefore be conveyed in the mean average
blood flow value (Figure 5). For human voluntary exer-
cise, it is of value to consider how variations in repeated
muscle contractions at target muscle strength (muscle
force) directly influence exercise blood flow in conduit
arteries. Therefore, we have investigated whether sudden
physiological and spontaneous changes in exercise
rhythm, and consequently workload, temporarily alter
blood flow to the working muscle [32].
The results showed that femoral arterial blood flow
increased positively and linearly (dotted line) with in-
creasing target workload. However, femoral arterial
blood flow was inversely and linearly related (solid line)
to the actual achieved workload, when measured over 60
consecutive contraction-relaxation cycle bouts for each
target intensity at 30 and 60 contractions per minute,
respectively (see in Figure 5).
Thus any sudden spontaneous increase or decrease in
the achieved workload transiently altered the relationship
between limb femoral arterial blood flow and the
achieved workload. The influence upon the magnitude of
Copyright © 2013 SciRes. OPEN ACCESS
T. Osada et al. / Open Journal of Molecular and Integrative Physiology 3 (2013) 158-165
Copyright © 2013 SciRes.
163
limb femoral arterial blood flow, due to fluctuations in
the achieved workload from the target workload was
similar at target workload sessions of 30 and 60 contrac-
tions per minute, respectively. These findings indicate
that a transient sudden increase in the workload during
rhythmic muscle contractions more rapidly impedes
femoral arterial blood flow, and that vasodilatation may
be elicited to restore the intensity related steady-state
limb blood flow response, in relation to the average
metabolic activity (Figure 6).
This evidence may contribute to the evaluation of ex-
ercise hemodynamics for rhythmic, dynamic-isotonic
exercise training, leading to exercise prescriptions (mus-
cle contraction frequency or muscle contraction intensity)
for healthy participants, as well as for patients requiring
additional physical activity in a rehabilitation or clinical
setting.
Figure 5. Relationship between steady-state femoral arterial
blood flow (FBF) and the achieved workload during incre-
mental dynamic knee-extensor exercise at 30 or 60 contractions
per minute (cpm) during a minute measurement in one subject
(60 samplings at each workload). FBF was inversely related (P
< 0.05) to the actual achieved workload (60 samplings) at (A)
30 and (B) 60 cpm, respectively, for each target workload (solid
line). The linear relationship was furthermore positive (P <
0.0001) between FBF (240 samplings at 30 cpm; 180 sam-
plings at 60 cpm) and the target workloads (at 10, 20, 30 and 40
W at 30 cpm; and at 20, 30 and 40 W at 60 cpm) in one subject
(dotted line). Figure adapted from Osada and Rådegran [32],
reproduced with permission from John Wiley & Sons Ltd.
4. CONCLUSION
The detection of blood velocity with high temporal reso-
lution in real time, at rest, and during exercise, is the
advantage of using the non-invasive technique of the
Doppler method. However, the enhanced alterations in
Figure 6. Changes in femoral arterial blood flow (FBF) related to fluctuations in the achieved workload around the
target workload. A negative relationship was found between changes in FBF and changes in the achieved workload
from mean target workload at (A) 30 and (B) 60 contractions per minute (cpm), respectively. A higher achieved
workload, with a higher muscular force, reduced FBF. A lower achieved workload, with a lower muscular force,
increased FBF. The influence on the FBF magnitude due to fluctuations from the target workload was similar be-
tween the target workload sessions at 30 and 60 cpm, respectively. At both 30 and 60 cpm, changes in FBF were
within 0.6 and 0.6 l/min from baseline at the target workload in all sessions. Furthermore, changes in FBF ranged
between 0.2 and 0.2 l/min from baseline when the achieved workload was increased or decreased by ~2 W. The
target workload is defined as an average value (equal to mean workload) of 60 samplings for the achieved work-
load at each target workload (10, 20, 30, and 40 W). The basal FBF value at the mean target workload (diamond
shape) was measured as the average of the plotted FBF values between the mean target workload minus 0.5 W and
the mean target workload plus 0.5 W; which is defined by the horizontal standard (horizontal) line of the FBF
value (“zero”). Figure adapted from Osada and Rådegran [32], reproduced with permission from John Wiley &
Sons Ltd.
OPEN ACCESS
T. Osada et al. / Open Journal of Molecular and Integrative Physiology 3 (2013) 158-165
164
blood velocity profile may potentially confuse the evalua-
tion of hemodynamics in the exercising muscles. This
review discussed muscle contraction-induced normal
physiological (internal) variations in blood velocity dur-
ing rhythmic muscle contractions, as well as changes in
exercising blood flow (external variations) due to spon-
taneous changes of muscle contraction force (workload)
compared to target intensity. These findings should be
considered when determining the precise physiological
net-blood velocity/flow values.
5. ACKNOWLEDGEMENTS
The staff of The Copenhagen Muscle Research Centre is greatly ac-
knowledged. The study was supported by the Danish National Research
Foundation Grant 504-14, Uehara Memorial Foundation in 2002, a
Grant-in-Aid for Young Scientists (B) in Scientific Research (No.
16700471) and the “Excellent Young Researchers Overseas Visit Pro-
gram” in Scientific Research (No. 21-8285) 2010 from MEXT and
JSPS.
REFERENCES
[1] Osada, T., Katsumura, T., Hamaoka, T., Inoue, S., Esaki,
K., Sakamoto, A., Murase, N., Kajiyama, J., Shimomitsu,
T. and Iwane, H. (1999) Reduced blood flow in abdomi-
nal viscera measured by Doppler ultrasound during one-
legged knee extension. Journal of Applied Physiology, 86,
709-719.
[2] Osada, T., Iwane, H., Katsumura, T., Murase, N., Higuchi,
H., Sakamoto, A., Hamaoka, T. and Shimomitsu, T.
(2012) Relationship between reduced lower abdominal
blood flows and heart rate in recovery following cycling
exercise. Acta Physiologica, 204, 344-353.
htt p: //dx.doi.org/10.1111/j. 1748-1716.2011.02349.x
[3] Saltin, B., Rådegran, G., Koskolou, M.D. and Roach, R.C.
(1998) Skeletal muscle blood flow in humans and its
regulation during exercise. Acta Physiologica Scandi-
navica, 162, 421-436.
http://dx.doi.org/10.1046/j.1365-201X.1998.0293e.x
[4] Sacchetti, M., Saltin, B., Osada, T. and Van Hall, G.
(2002) Intramuscular fatty acid metabolism in contracting
and non-contracting human skeletal muscle. Journal of
Physiology (London), 540, 387-395.
http://dx.doi.org/10.1113/jphysiol.2001.013912
[5] Steensberg, A., Febbraio, M.A., Osada, T., Schjerling, P.,
Van Hall, G., Saltin, B. and Pedersen, B.K. (2001) Inter-
leukin-6 production in contracting human skeletal muscle
is influenced by pre-exercise muscle glycogen content.
Journal of Physiology (London), 537, 633-639.
htt p: //dx.doi.org/10.1111/j. 1469-7793.2001.00633.x
[6] Rådegran, G. (1997) Ultrasound Doppler estimates of
femoral artery blood flow during dynamic knee extensor
exercise in humans. Journal of Applied Physiology, 83,
1383-1388.
[7] Osada, T. and Rådegran, G. (2002) Femoral artery inflow
in relation to external and total work rate at different knee
extensor contraction rates. Journal of Applied Physiology,
92, 1325-1330.
[8] Walløe, L. and Wesche, J. (1988) Time course and mag-
nitude of blood flow changes in the human quadriceps
muscles during and following rhythmic exercise. Journal
of Physiology (London), 405, 257-273.
[9] Shoemaker, J.K., Hodge, L. and Hughson, R.L. (1994)
Cardiorespiratory kinetics and femoral artery blood ve-
locity during dynamic knee extension exercise. Journal of
Applied Physiology, 77, 2625-2632.
[10] Andersen, P. and Saltin, B. (1985) Maximal perfusion of
skeletal muscle in man. Journal of Physiology (London),
366, 233-249.
[11] Gill, R.W. (1985) Measurement of blood flow by ultra-
sound: Accuracy and sources of error. Ultrasound in
Medicine and Biology, 11, 625-641.
http://dx.doi.org/10.1016/0301-5629(85)90035-3
[12] Hughson, R.L., MacDonald, M.J., Shoemaker, J.K. and
Borkhoff, C. (1997) Alveolar oxygen uptake and blood
flow dynamics in knee extension ergometry. Methods of
Information in Medicine, 36, 364-367.
[13] Osada, T. (2004) Muscle contraction-induced limb blood
flow variability during dynamic knee extensor. Medicine
and Science in Sports and Exercise, 36, 1149-1158.
http://dx.doi.org/10.1249/01.MSS.0000132272.36832.6A
[14] Rådegran, G. and Saltin, B. (1998) Muscle blood flow at
onset of dynamic exercise in humans. American Journal
of Physiology Heart and Circulatory Physiology, 274,
H314-H322.
[15] Robergs, R.A., Icenogle, M.V., Hudson, T.L. and Greene,
E.R. (1997) Temporal inhomogeneity in brachial artery
blood flow during forearm exercise. Medicine and Sci-
ence in Sports and Exercise, 29, 1021-1027.
http://dx.doi.org/10.1097/00005768-199708000-00006
[16] Isnard, R., Lechat, P., Kalotka, H., Chikr, H., Fitoussi, S.,
Salloum, J., Golmard, J-L., Thomas, D. and Komajda, M.
(1996) Muscular blood flow response to submaximal leg
exercise in normal subjects and in patients with heart
failure. Journal of Applied Physiology, 81, 2571-2579.
[17] Leyk, D., Eßfeld, D., Baum, K. and Stegemann, J. (1992)
Influence of calf muscle contractions on blood flow pa-
rameters measured in the arteria femoralis. International
Journal of Sports Medicine, 13, 588-593.
http://dx.doi.org/10.1055/s-2007-1024571
[18] MacDonald, M.J., Shoemaker, J.K., Tschakovsky, M.E.
and Hughson, R.L. (1998) Alveolar oxygen uptake and
femoral artery blood flow dynamics in upright and supine
leg exercise in humans. Journal of Applied Physiology,
85, 1622-1628.
[19] Sjøgaard, G., Kiens, B., Jørgensen, K. and Saltin, B.
(1986) Intramuscular pressure, EMG and blood flow dur-
ing low-level prolonged static contraction in man. Acta
Physiologica Scandinavica, 128, 475-484.
htt p: //dx.doi.org/10.1111/j. 1748-1716.1986.tb08002.x
[20] Andersen, P., Adams, R.P., Sjøgaard, G., Thorboe, A.
and Saltin, B. (1985) Dynamic knee extension as model
for study of isolated exercising muscle in humans. Jour-
nal of Applied Physiology, 59, 1647-1653.
[21] Osada, T. and Rådegran, G. (2006) Differences in exer-
Copyright © 2013 SciRes. OPEN ACCESS
T. Osada et al. / Open Journal of Molecular and Integrative Physiology 3 (2013) 158-165 165
cising limb blood flow variability between cardiac and
muscle contraction cycle related analysis during dynamic
knee extensor. Journal of Sports Medicine and Physical
Fitness, 46, 590-597.
[22] Osada, T. and Rådegran, G. (2006) Alterations in the
blood velocity profile influence the blood flow response
during muscle contractions and relaxations. Journal of
Physiological Science, 56, 195-203.
http://dx.doi.org/10.2170/physiolsci.RP002905
[23] Cronestrand, R. (1970) Leg blood flow at rest and during
exercise after reconstruction for occlusive disease. Scan-
dinavian Journal of Thoracic Cardiovascular Surgery,
Supplement 4, 1-24.
[24] Jorfeldt, L., Juhlin-Dannfelt, A., Pernow, B. and Wassén,
E. (1978) Determination of human leg blood flow: A
thermodilution technique based on femoral venous bolus
injection. Clinical Science and Molecular Medicine, 54,
517-523.
[25] Lassen, N.A., Linbjerg, I. and Munck, O. (1964) Meas-
urement of blood flow through skeletal muscle by intra-
muscular injection of xenon 133. Lancet, 1, 686-689.
http://dx.doi.org/10.1016/S0140-6736(64)91518-1
[26] Rådegran, G., Pilegaard, H., Nielsen, J.J. and Bangsbo, J.
(1998) Microdialysis ethanol removal reflects probe re-
covery rather than local blood flow in skeletal muscle.
Journal of Applied Physiology, 85, 751-757.
[27] Boushel, R., Langberg, H., Olesen, J., Nowak, M., Si-
monsen, L., Bülow, J. and Kjær, M. (2000) Regional
blood flow during exercise in humans measured by near-
infrared spectroscopy and indocyanine green. Journal of
Applied Physiology, 89, 1868-1878.
[28] Ruotsalainen, U., Raitakari, M., Nuutila, P., Oikonen, V.,
Sipilä, H., Teräs, M., Knuuti, M.J., Bloomfield, P.M. and
Iida, H. (1997) Quantitative blood flow measurement of
skeletal muscle using oxygen-15-water and PET. Journal
of Nuclear Medicine, 38, 314-319.
[29] Jensen, B.R., Sjøgaard, G., Bornmyr, S., Arborelius, M.
and Jørgensen, K. (1995) Intramuscular laser-Doppler
flowmetry in the supraspinatus muscle during isometric
contractions. European Journal of Applied Physiology
and Occupational Physiology, 71, 373-378.
http://dx.doi.org/10.1007/BF00240420
[30] Rådegran, G. (1999) Limb and skeletal muscle blood
flow measurements at rest and during exercise in human
subjects. Proceedings of Nutrition Society, 58, 887-898.
http://dx.doi.org/10.1017/S0029665199001196
[31] Tschakovsky, M.E., Saunders, N.R., Webb, K.A. and
O’donnell, D.E. (2006) Muscle blood-flow dynamics at
exercise onset: Do the limbs differ? Medicine and Sci-
ence in Sports and Exercise, 38, 1811-1818.
http://dx.doi.org/10.1249/01.mss.0000230341.86870.4f
[32] Osada, T. and Rådegran, G. (2009) Femoral artery blood
flow and its relationship to spontaneous fluctuations in
rhythmic thigh muscle workload. Clinical Physiology and
Functional Imaging, 29, 277-292.
htt p: //dx.doi.org/10.1111/j. 1475-097X.2009.00868.x
Copyright © 2013 SciRes. OPEN ACCESS
... Postischemic hyperemia may be achieved with voluntary masseter and temporal muscle contraction (Supporting Information Figure S2). 25 In the case of MXA and MMA, the muscles' constriction unavoidably narrows the acoustic window, causing the MMA, and sometimes even the MXA to become unavailable. Temporal region compression does not alter the flow in MXA or MMA, probably because they supply mainly the facial area. ...
Cover Page
The cover image, by Toplica Lepić et al., is based on the RESEARCH ARTICLE Ultrasonographic assessment of the maxillary artery and middle meningeal artery in the infratemporal fossa. DOI: 10.1002/jcu.22773.
... Postischemic hyperemia may be achieved with voluntary masseter and temporal muscle contraction (Supporting Information Figure S2). 25 In the case of MXA and MMA, the muscles' constriction unavoidably narrows the acoustic window, causing the MMA, and sometimes even the MXA to become unavailable. Temporal region compression does not alter the flow in MXA or MMA, probably because they supply mainly the facial area. ...
Article
Purpose To investigate with Doppler ultrasonography the maxillary and middle meningeal arteries in the infratemporal fossa, and describe their hemodynamic characteristics. Methods We included 24 female and 11 male volunteers without vascular diseases, with a median age of 43 years. We used the acoustic window, enlarged by subjects half‐opening their mouth, located below the zygomatic arch, in front of temporo‐mandibular joint, to reach the maxillary and middle meningeal arteries. Results In the 35 subjects, 112 arteries were visualized successfully: 60 maxillary (85.7%), and 52 middle meningeal arteries (74.3%), at a depth of 2.40 and 2.50 cm, respectively. Their blood flow was directed anteriorly and away from the probe. While all the measured hemodynamic characteristics differed significantly between the maxillary and the middle meningeal artery (P < 0.001), there was no significant difference between male and female subjects, nor between the left or the right side. Conclusions The maxillary and middle meningeal arteries can be insonated in the infratemporal fossa through the easily accessible acoustic window below the zygomatic arch, when the patient holds his mouth half open. They can be differentiated by their ultrasonographic characteristics and blood flow features.
... It is indicated that AR recovery not only cannot slower SD, but it worsens the situation. Though it is indicated in researches that AR recovery can boost blood circulation [7], then the reason why it is not consistent with this research may be that continual active contraction after muscle injury cause ineffective rest for muscles of fatigue injury. It causes piling of Advances in Social Science, Education and Humanities Research, volume 105 interstitial fluid over that eliminated, so the body cannot obtain fatigue recovery and negative effect is caused. ...
... In the knee extensor exercise model utilizing a relatively small thigh muscle mass, the local factors regulating BF are thought to be of most importance including the voluntary repeated muscle contractions. It has previously been discussed that muscle contraction-induced rapid alterations in the conduit arterial blood velocity profile may be closely related to the magnitude of intramuscular pressure variation (muscle mechanical factors) and superimposed influence of perfusion pressure variation (pulsatile hemodynamic factors) [10,11,[13][14][15][20][21][22]. During steady-state, high intramuscular pressure during muscle contractions Figure 5a adapted from Osada and Rådegran [12], reproduced with permission from Edizioni Minerva Medica. ...
... Moreover, external factors representing repeated voluntary muscle contraction force may also influence the magnitude of BF fluctuation due to spontaneous changes in muscle contraction workload. The content in this review has partially been discussed in our previous review articles 36,37) . ...
Article
Exercising muscle blood flow (BF) may be an indicator of oxygen supply change allowing increased muscle energy metabolism through the circulatory response between central and peripheral hemodynamics. During exercise an increase in cardiac output may represent the interplay of alterations in both blood pressure and vascular conductance. Dynamic muscle contractions lead to an increase in cardiac output and promote venous return at the onset of exercise, and concurrently lead to enhanced muscle vasodilatation (and thus increased muscle BF) due to metabolites, neurological responses and/or other mechanisms, causing exercise hyperaemia. Doppler ultrasound can non-invasively detect with high resolution the temporal pulsatile blood velocity profiles in the conduit artery at rest as well as during muscle contractions. Based on this technique, it has been shown that alterations in the physiological blood velocity profile related to cardiac systole-diastole and fluctuations in the beat-by-beat blood velocity profile are due to rapid changes in the blood velocity profile concurrent with muscle contraction and/or relaxation during exercise (dynamic/static) or respiratory cycle, in different states (muscle contraction time/frequency or workload), or of any other type of vasodilatation/vasoconstriction. Muscle contraction-induced alterations in the blood velocity profile may be due in general to the magnitude of intramuscular pressure variation (mechanical factors) and the superimposed influence of perfusion pressure variation (pulsatile hemodynamic factors). This review therefore focuses on methodological considerations for muscle contraction-induced blood velocity/flow variability in the leg conduit artery, which in turn influences the magnitude of exercising BF during dynamic knee extensor exercise.
Article
Doppler ultrasound has now developed to the point where the rate of flow of blood in a given vessel can be measured with appropriate instrumentation. The theoretical basis of Doppler flow measurement is reviewed in this paper, with particular emphasis on the potential and actual sources of error. Three distinct approaches are identified, and the strengths and weaknesses of each discussed. The separate errors involved in estimating the vessel cross-sectional area, the angle of approach, and the Doppler shift are analyzed, together with the question of the uniformity of scattering from the blood. In vivo and in vitro tests of the accuracy obtained using a number of Doppler flow measuring instruments are then reviewed. It is concluded that the Doppler methods are capable of good absolute accuracy when suitably designed equipment is used in appropriate situations, with systematic errors of 6% of less. There are, however, considerable random errors, attributable primarily to errors in measuring the cross-sectional area and the angle of approach. Repeating the measurement of flow several times and averaging the results can reduce these random errors to an acceptable level.
Article
• Prolonged exercise results in a progressive decline in glycogen content and a concomitant increase in the release of the cytokine interleukin-6 (IL-6) from contracting muscle. This study tests the hypothesis that the exercise-induced IL-6 release from contracting muscle is linked to the intramuscular glycogen availability. • Seven men performed 5 h of a two-legged knee-extensor exercise, with one leg with normal, and one leg with reduced, muscle glycogen content. Muscle biopsies were obtained before (pre-ex), immediately after (end-ex) and 3 h into recovery (3 h rec) from exercise in both legs. In addition, catheters were placed in one femoral artery and both femoral veins and blood was sampled from these catheters prior to exercise and at 1 h intervals during exercise and into recovery. • Pre-exercise glycogen content was lower in the glycogen-depleted leg compared with the control leg. Intramuscular IL-6 mRNA levels increased with exercise in both legs, but this increase was augmented in the leg having the lowest glycogen content at end-ex. The arterial plasma concentration of IL-6 increased from 0.6 ± 0.1 ng l−1 pre-ex to 21.7 ± 5.6 ng l−1 end-ex. The depleted leg had already released IL-6 after 1 h (4.38 ± 2.80 ng min−1 ( P −1). A significant net IL-6 release was not observed until 2 h in the control leg. • This study demonstrates that glycogen availability is associated with alterations in the rate of IL-6 production and release in contracting skeletal muscle.
Article
Clearance of the radioactive inert gas 133Xenon injected muscularly was studied in 46 healthy subjects and 13 patients with radiologically verified occlusive disease of the main arteries of the legs and intermittent claudication. In contrast with 24Na or 131 I ions 133Xenon diffused freely across cell membranes and local muscle blood-flow can therefore readily be calculated in ml per 100 g per minute from the 133Xenon clearance-rate. Muscle blood flow (MBF) averaged 1.5 ml per 100 g per minute at rest in patients with vascular disease. This was not significantly lower than the average of 2.0 ml per 100 g per minute in healthy persons over age 50. Healthy subjects younger than 50 years had an average resting MBF of 2.2 ml per 100 g per minute. After work induced ischemia maximal MBF inpatients with vascular disease averaged 17 ml per 100 g per minute. This value was significantly below the corresponding normal values of 55 and 52 ml per 100 g per minute in the normal subjects. In the same patients the average time until maximal reactive hyperemia was reached was significantly longer--2.3 minutes in contrast to 0.4 minutes in normal subjects. The 133Xenon values accorded well with the results usually found by means of venous occlusion plethysmography but unlike this method 133Xenon can be used to measure MBF directly during muscular work with little interference from non-muscular tissues.
Article
To examine the blood flow (BF) response in the lower abdomen (LAB) in recovery following upright cycling exercise at three levels of relative maximum pulmonary oxygen consumption (VO(2max)) and the relationship of BF(LAB) to heart rate (HR) and target intensity. For 11 healthy subjects, BF (Doppler ultrasound) in the upper abdominal aorta (Ao) above the coeliac trunk and in the right femoral artery (RFA) was measured repeatedly for 720 s after the end of cycling exercises at target intensities of 30%, 50% and 85% VO(2max), respectively. Blood flow in the lower abdomen (BF(LAB)) can be measured by subtracting bilateral BF(FAs) (≈twofolds of BF(RFA)) from BF(Ao). Change in BF(LAB) (or BF(LAB) volume) at any point was evaluated by difference between change in BF(Ao) and in BF(FAs). Heart rate and blood pressure were also measured. At 85% VO(2max), significant reduction in BF(LAB) by approx. 89% was shown at 90 s and remained until 360 s. At 50% VO(2max), reduction in BF(LAB) by approx. 33% was found at 90 s although it returned to pre-exercise value at 120 s. On the contrary at 30% VO(2max), BF(LAB) showed a light increase (<20%) below 70 bpm of HR. There was a close negative relationship (P < 0.05) between change in BF(LAB) and recovery HR, as well as between change in BF(LAB) volume and both recovery HR and % VO(2max). This study suggests that the lower abdominal BF in recovery may be influenced by sympathetic-vagus control, and dynamics of BF(LAB) may be closely related to the level of relative exercise intensities.
Article
Limb femoral arterial blood flow (LBF) is known to increase linearly with increasing workload under steady-state conditions, suggesting a close link between LBF and metabolic activity. We, however, hypothesized that sudden physiological and spontaneous changes in exercise rhythm, and consequently workload temporarily alter blood flow to the working muscle. LBF and its relation to fluctuations in the contraction rhythm and workload were therefore investigated. LBF, measured by Doppler ultrasound, and the achieved workload, were continuously measured in nine subjects, aiming to perform steady-state, one-legged, dynamic knee-extensor exercise at 30 and 60 contractions per minute (cpm), at incremental target workloads of 10, 20, 30 and 40 W. In agreement with previous findings, LBF increased positively and linearly (P<0.05) with increasing target workload. However, LBF was inversely and linearly related (P<0.05) to the actually achieved workload, when measured over 60 consecutive contraction-relaxation cycle bouts, for each target intensity at 30 and 60 cpm respectively. Thus any sudden spontaneous increase or decrease in the achieved workload transiently altered the relationship between LBF and the achieved workload. The influence upon the magnitude of LBF, due to fluctuations in the achieved workload from the target workload, was furthermore similar between target workload sessions at 30 and 60 cpm respectively. LBF was, however, not associated with variations in the contraction frequencies. These findings indicate that a transient sudden increase in the workload more rapidly impedes LBF and that vasodilatation may be elicited to restore the intensity related steady-state LBF response in relation to the average metabolic activity.
Article
1. A thermodilution method was developed for the determination of human leg blood flow. The method is based on bolus injection of an indicator distally into the femoral vein, at room temperature, and recording of the dilution curve in the same vessel at the level of the inguinal ligament. The blood flow was computed automatically with two thermistors and an integrator. 2. The leg blood flow determined by this method at rest and during exercise at work loads of 50, 100 and 150 W in six healthy subjects was found to agree closely with measurements by an intraarterial indicator-dilution technique. A linear relationship was found between leg blood flow and work. The reproducibility of the blood flow determinations, expressed as the coefficient of variation for a single determination, was 12·9 at rest and 5·3 or less during exercise. 3. The method was used in two patients with occlusive arterial disease of the leg. Extremely low leg blood flows were found in these patients when they were forced to interrupt the exercise by severe calf pain.
Article
Ten healthy male subjects performed single (< 1 s), sustained and intermittent plantarflexions (up to 40 s) of one foot in sitting exercise position. Two different absolute forces were applied, which, in terms of maximal voluntary contraction, ranged between 5%-10% and 25%-30%. Blood velocity was continuously recorded in the proximal arteria femoralis by means of the Doppler technique. Heart rate (HR) and mean blood pressure (BP) were simultaneously determined using standard ECG and the FINAPRES method. Despite the distance between the proximal arteria femoralis and the exercising muscle the Doppler data showed: effects of single contractions on the individual Doppler data, the influence of consecutive contractions, variation with exercise intensity and differences between sustained and intermittent contractions. In all exercise tests there was an immediate significant increase in blood velocity at the onset of exercise. The major part (range 52%-73%) of the response to the 40 s tests was seen during the first 6 s. It was followed by a second phase of adjustment which depended on the type of exercise and exercise intensity. The single plantarflexion provoked increases in blood velocity for about 20 s. A comparison of HR and BP tracings with the Doppler data demonstrated the importance of local mechanical factors for the perfusion of the exercising muscle. The early adjustment of muscle perfusion were not correlated to the systemic blood pressure and, therefore, appeared to be related to muscle pump effects. The subsequent flow values were influenced by passive vessel compression and changes in local vasomotor tone.(ABSTRACT TRUNCATED AT 250 WORDS)
Article
1. Pulsed bidirectional Doppler-ultrasound equipment was used to measure changes in blood velocities in the femoral artery on a beat to beat basis for consecutive contraction and relaxation phases during voluntary rhythmic exercise of the quadriceps muscle group in man. 2. Rapid and large fluctuations of blood velocities were found, being high during relaxation and low during contraction phases. At the onset of contraction phase, negative velocities were present, indicating retrograde flow. During the rest of the contraction phase, forward flow occurred comparable to the resting flow level even at high loads. 3. Estimated maximal flow to the whole leg during relaxation phase, calculated from these blood velocity measurements and vessel diameter (measured with echo-ultrasound equipment with high resolution) was in two of the subjects 3.32 l min-1 (female) and 5.97 l min-1 (male). When using computer tomography to estimate the volume of the quadriceps muscle group, the calculated maximum flow to this muscle group was 243 (female) and 257 (male) ml min-1 100 ml muscle-1. The time-averaged flow during exercise to the whole leg was 1.51 l min-1 (female) and 2.47 l min-1 (male). The calculated time-averaged flow to the quadriceps muscle group was 101 (female) and 98 (male) ml min-1 100 ml muscle-1. 4. The duration of post-contraction hyperaemia following such rhythmic exercise of up to 6 min duration and up to 75% maximum voluntary contraction was never in excess of 150 s.
Article
Seven men performed one-legged isometric knee-extension at 5% MVC for 1 h. Intramuscular pressure increased with contraction from its resting value of 14 (2-31) mmHg. Some intramuscular pressure recordings stayed at an almost constant level through the 1 h contraction, but most recordings showed large fluctuations from resting values up to 90 mmHg. The overall mean intramuscular pressure was twice the resting value. In some cases, EMG recordings confirmed that the changes in intramuscular pressure were related to alternating recruitment of various parts of the knee-extensors. Blood flow in the femoral vein increased within 3 min of 5% MVC to a level of 1.58 (1.25-2.22) 1 min-1 and no significant changes occurred during the 1 h contraction. In two subjects blood flow was measured also in the recovery period, and this decreased almost immediately when the muscle relaxed. It is concluded that during low-level static contractions, the blood supply to the exercising muscle is maintained at a sufficiently high level, and that the alternating recruitment of muscle fibres may result in a heterogeneously distributed blood flow within the contracting muscle. Despite this the muscle was fatigued after the 1 h at 5% MVC. The rating of perceived exertion (RPE) increased from 1.9 (1-3) at the beginning to 4.5 (2-8) at the end of contraction, and MVC was decreased by 12% after the contraction.
Article
Five subjects exercised with the knee extensor of one limb at work loads ranging from 10 to 60 W. Measurements of pulmonary oxygen uptake, heart rate, leg blood flow, blood pressure and femoral arterial-venous differences for oxygen and lactate were made between 5 and 10 min of the exercise. Flow in the femoral vein was measured using constant infusion of saline near 0 degrees C. Since a cuff was inflated just below the knee during the measurements and because the hamstrings were inactive, the measured flow represented primarily the perfusion of the knee extensors. Blood flow increased linearly with work load right up to an average value of 5.7 l min-1. Mean arterial pressure was unchanged up to a work load of 30 W, but increased thereafter from 100 to 130 mmHg. The femoral arterial-venous oxygen difference at maximum work averaged 14.6% (v/v), resulting in an oxygen uptake of 0.80 l min-1. With a mean estimated weight of the knee extensors of 2.30 kg the perfusion of maximally exercising skeletal muscle of man is thus in the order of 2.5 l kg-1 min-1, and the oxygen uptake 0.35 l kg-1 min-1. Limitations in the methods used previously to determine flow and/or the characteristics of the exercise model used may explain why earlier studies in man have failed to demonstrate the high perfusion of muscle reported here. It is concluded that muscle blood flow is closely related to the oxygen demand of the exercising muscles. The hyperaemia at low work intensities is due to vasodilatation, and an elevated mean arterial blood pressure only contributes to the linear increase in flow at high work rates. The magnitude of perfusion observed during intense exercise indicates that the vascular bed of skeletal muscle is not a limiting factor for oxygen transport.