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Difference in muscle blood flow fluctuations between dynamic and static thigh muscle contractions: How to evaluate exercise blood flow by Doppler ultrasound

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Commentary
Physical Medicine and Rehabilitation Research
Phys Med Rehabil Res, 2016 doi: 10.15761/PMRR.1000128 Volume 1(5): 1-7
ISSN: 2398-3353
Dierence in muscle blood ow uctuations between
dynamic and static thigh muscle contractions: How to
evaluate exercise blood ow by Doppler ultrasound
Takuya Osada1,2* and Göran Rådegran3
1Rehabilitation Center, Tokyo Medical University Hospital, Tokyo, Japan
2Cardiac Rehabilitation Center, Tokyo Medical University Hospital, Tokyo, Japan
3Lund University, Department of Clinical Sciences Lund, Cardiology, Lund, and The Section for Heart Failure and Valvular Disease, VO. Heart and Lung Medicine,
Skåne University Hospital, Lund, Sweden
Correspondence to: Takuya Osada, MD, PhD, Rehabilitation Center, Cardiac
Rehabilitation Center, Tokyo Medical University Hospital, 6-7-1, Nishishinjuku,
Shinjuku-ku, Tokyo 160-0023, Japan, Tel: +81-33342-6111; Fax: +81-33342-
7082; E-mail: dentacmac@aol.com
Key words: muscle blood ow uctuations, dynamic and static muscle contractions,
knee extensor exercise, Doppler ultrasound
Received: December 04, 2016; Accepted: December 21, 2016; Published:
December 30, 2016
Introduction
Determination of limb blood ow (BF) in relation to exercise may
be useful in rehabilitation programs, increasing the general knowledge
on oxygen supply, energy metabolism as well as on central and
peripheral hemodynamics.
Peak leg muscle oxygen uptake has previously been found to be
closely related to the diameter of the feeding artery, which may vary
in relation to the dependent muscle mass and oxygen need [1]. e
time course of BF alterations may be inuenced by remodeling of the
arterial structure or restricted motor control as seen in musculoskeletal
disorders like disuse syndrome and cerebrovascular disorders with
hemiplegia [2-5].
Exercise hyperemia with vasodilation is related to intrinsic
(endothelial-related factors, autacoid substances, metabolite and
myogenic response) as well as extrinsic (autonomic nerve regulation,
signal/reexes with central command and exercise pressor reexes
with mechanical muscle contraction/accumulated metabolite product)
regulation, as well as changes in arteriovenous pressure gradient due
to the muscle pump. Furthermore, during exercise the increase in limb
oxygen uptake (calculated as the product of exercising arterial BF and
the arteriovenous oxygen dierence to the exercising limb) is directly
proportional to the work performed in relation to the interplay between
cardiovascular regulation and muscle energy metabolism. erefore,
determination of limb BF response to exercise through physical training
may yield information about an integrated circulatory adaptation and
strengthening of muscle force at the target of exercise/rehabilitation
prescription. Furthermore, the comparison of hemodynamics during
transient exercise such as repeated limb muscle contractions between
pre- and post-physical therapy may increase our understanding of
the peripheral BF adjustment (so called physical training induced-
circulatory adaptation).
Non-invasive Doppler ultrasound with a high temporal resolution
can continuously detect alterations in pulsatile blood velocity proles
as “time and space-averaged and amplitude, signal intensity weighted
mean blood velocity” in the conduit artery. e arterial BF can be
calculated as the mean blood velocity multiplied by the cross-sectional
area in the target artery.
Based on this technique, rapid changes in time courses of blood
velocity proles in the conduit artery have been found, with muscle
contraction and/or muscle relaxation during exercise (dynamic/static),
in dierent states of muscle contraction time/frequency and workload,
and in relation to vasodilatation/vasoconstriction. Furthermore,
the determination of a comprehensive exercise BF, for instance in a
brachial, femoral or popliteal artery feeding a limb working muscle
group can also be performed during muscle contractions such as with
the exercise model of forearm handgrip, lower limb knee extensor or
plantar exion exercise.
Following our previous reports with the series of investigation
for muscle/exercise BF regulation during limb exercise using Doppler
ultrasound [6-15], large dierences have been observed in the time
course of the magnitude of the blood velocity prole during steady-
state muscle contraction-relaxation phases and between dynamic
and static muscle contraction. is raises the issue how to determine
exercise BF optimally during repeated muscle contractions.
In general, an optimal/valid BF in a non-exercise limb may exhibit
minimum physiological BF variability using samplings of cardiac beat-
by-beat cycle (BBcycle). However, during muscle contractions, the
muscle contraction-induced blood velocity prole in the working limb
muscle may be greatly inuenced by the magnitude of intramuscular
pressure variation and the superimposed inuence of perfusion
pressure variation. us, for determination of optimal exercise BF we
must consider how to treat the minimum physiological variability in
exercise BF via muscle contraction-relaxation cycle (CRcycle) and/or
cardiac BBcycle.
e present commentary visualizes how to determine BF during
exercise in relation to CRcycle or BBcycle, in dynamic/isotonic and
static/isometric exercise, utilizing the knee extensor model and the
Doppler ultrasound technique.
Osada T (2016) Dierence in muscle blood ow uctuations between dynamic and static thigh muscle contractions: How to evaluate exercise blood ow by Doppler
ultrasound
Volume 1(5): 2-7
Phys Med Rehabil Res, 2016 doi: 10.15761/PMRR.1000128
One-legged repeated knee extensor exercise model
Previous studies reported measurement of exercising leg BF by the
invasive thermodilution technique, utilizing the one-legged, dynamic
(so called isotonic or rhythmic) knee-extensor exercise model [16,17].
However, this invasive technique has the limitation of not being able
to detect the beat-by-beat blood velocity prole for temporal duration
in real time. Whereas many of the available techniques are impaired
by dierent methodological limitations, the indicator thermodilution
and non-invasive Doppler ultrasound methods have both been found
to give repeatable measurements of the same magnitude during both
rest and dynamic knee extensor exercise [18,19]. Furthermore, the
thermodilution measurements obtained under similar experimental
conditions by Andersen et al. [18] are statistically similar to those
obtained by Doppler ultrasound.
In one-legged, dynamic/static knee-extensor exercise, the exercise
(absolute workload using the unit watt, W or relative maximum
1
Ergometer
Workload
Muscle power
as target workload
(Strain-gauge)
Active (0.5s)
k
T
a
<
DYNAMIC
>
Isotonic muscle contraction
Femoral artery blood velocity/flow
(Doppler ultrasound)
a)
Muscle relaxation
Passive (0.5s)
Pre-ex Recovery
1-duty cycles
2 185 288 289 290 3001821813 288288 288183 184
(10, 20, 30 or 40W)
0
CR
180 300 (sec)
Steady-state
(60 cpm)
0 10 20
Muscle relaxation
<
STATIC
>
Isometric muscle contraction
Alternating
Relax (10s)
Muscle power
for target workload
(Strain-gauge)
Fixed
axle
Active (10s)
b)
k
T
a
Recovery
1210 11 12 13 14 15-duty cycles
CR
300(sec)180
(10, 30, 50 or 70%MVC)
Steady-state
Pre-ex
(3 cpm)
Figure 1. One-legged knee extensor exercise model
a) <Dynamic> Isotonic muscle contraction at 60 contractions per minute performed as 0.5s-voluntary (active) muscle contraction and 0.5s-passive muscle relaxation (1s) for 5 min at 10,
20, 30 and 40 W, respectively.
b) <Static> Repeat isometric muscle contraction performed as 10s-voluntary (active) isometric muscle contraction and 10s-muscle relaxation (20s) for 5 min at 10%, 30%, 50% and
70%MVC, respectively.
The voluntary contraction rhythm was maintained by following the pace of a visible and audible metronome and by visualizing the contraction frequency displayed in real time on a monitor.
Simultaneous recording of hemodynamic parameters was measured at a steady-state from 3 min to 5 min. Pre-ex, pre-exercise; %MVC, percentage of maximum voluntary contraction; C,
muscle contraction phase; R, muscle relaxation phase.
Osada T (2016) Dierence in muscle blood ow uctuations between dynamic and static thigh muscle contractions: How to evaluate exercise blood ow by Doppler
ultrasound
Volume 1(5): 3-7
Phys Med Rehabil Res, 2016 doi: 10.15761/PMRR.1000128
voluntary contraction (MVC) using the unit percentage of MVC,
%MVC) is conned to the quadriceps muscle group (Figure 1). is
model allows stable measurements of femoral arterial blood velocity
using Doppler ultrasound, in comparison to treadmill walking or
running models, which do not allow BF measurement in the feeding
conduit femoral artery, due to the diculty of insonation [6,8,10-
15,18,19].
e measurement of blood velocity in the femoral artery feeding
the active thigh muscles using Doppler ultrasound, where BF is
determined by the product of blood velocity and cross-sectional area,
has been validated and shown to produce accurate absolute values both
at rest and during incremental leg exercise such as rhythmical/dynamic
[18] or static thigh muscle contractions [15]. us, the high temporal
resolution of the Doppler ultrasound enables continuous measurement
of blood velocity throughout the kicking duty cycle during one-legged
dynamic/static knee extensor exercise.
e measurement site of the femoral artery was distal to the inguinal
ligament, but above the bifurcation into the branches of the supercial
and deep femoral arteries. is location minimizes turbulence from
the femoral bifurcation and the inuence of blood velocity from the
inguinal region. Furthermore, the changes of the vessel diameter of the
conduit artery in the target location are mostly unaected by muscle
contractions and relaxations [6,8,15,18]. erefore, changes in blood
velocity may potentially correspond to changes in BF because BF is
calculated by the product of mean blood velocity and the stable cross-
sectional area in the target artery.
Regarding the hemodynamics in the leg conduit femoral artery
during knee extensor exercise, we have previously: 1) validated the
method during exercise [18], 2) determined changes in BF due to
incremental work intensity at dierent muscle contraction frequencies
[8,15], and evaluated 3) the physiological variability/uctuations in
the magnitude of blood velocity/BF due to the muscle contraction
and relaxation phases [10-13], as well as 4) changes in BF due to
spontaneous changes of workload at a certain target intensity and
muscle contraction per minute (cpm) rate [14]. e exercise model
presented in this commentary was 1) dynamic muscle contractions at
60 cpm (0.5s-on and 0.5s-o) at 10, 20, 30 and 40 W (Figure 1a), 2)
repeated static muscle contractions at 3 cpm (10s-on and 10s-o) at
10%, 30%, 50% and 70% of MVC (Figure 1b).
Blood velocity/ow uctuations due to voluntary mus-
cle contraction and cardiac contractions
e dierence between dynamic and static muscle contractions
depends on the time period of muscle contraction and relaxation
phases (corresponding to muscle contraction frequency). We therefore
focused on the magnitude of blood velocity/BF between muscle
contraction and relaxation phases, and its variations between CRcycle
and BBcycle using dynamic (60 cpm) and static (3 cpm) exercise.
As shown in Figure 2, continuous recordings of hemodynamic
parameters can demonstrate the magnitude of the physiological
variability in blood velocity during dynamic- and repeated static-thigh
muscle contractions.
In dynamic/isotonic exercise at 60 cpm (0.5s-on and 0.5s-o), the
continuous blood velocity curve during repeated muscle contractions
uctuated rapidly due to the muscle force curve, which indicated that
the 0.5s-muscle contraction restricted BF (temporal reduced blood
velocity), and consequently 0.5s-muscle relaxation may induce an
increase in BF (higher blood velocity) (Figure 2a). eoretically, the
rate of 60 cpm (single muscle contraction-relaxation cycle in 1s) may be
able to uniformly interfere with the magnitude of the single whole blood
velocity prole (interval < 1s) when the heart rate is above 60 beats/min
(i.e. time interval of muscle contraction similar to heart rate) during
exercise. is means that rapid changes of muscle force curve every
second may completely disturb the formal blood velocity prole (time
and space-averaged and amplitude as the clear systolic and diastolic-
like prole, blood pressure curve-like). erefore, we acknowledge the
muscle contraction-induced physiological BF variability with systole
and diastole superimposed by CRcycle.
Figure 3a (corresponding to an expanded view indicated in Figure
2a) clearly shows the four specic variations with magnitude of the
physiological variability in blood velocity with muscle contraction
or relaxation-induced variations in muscle force, and consequently
the intramuscular pressure variations, along with the additional
inuence of blood pressure, as well as the tonic inuence of the state
of vasodilatation. An oscillation in the peak of the blood velocity is
partially related to the interaction between peak muscle force strength
and the peak blood pressure curve. In particular, the magnitude of the
tip point of blood velocity prole for a single muscle contraction or
muscle relaxation with single systolic or diastolic phase was found to be
closely related to the point in a peak systolic- or second peak diastolic-
blood pressure curve throughout the muscle contraction and muscle
relaxation phases as determined by muscle force curve and/or the
electromyography signals.
ere is a relatively high BF component at the systolic phase
during muscle relaxation (RS), and at the diastolic phase during
muscle relaxation (RD), as compared to the relatively low (reduced)
BF component at the systolic phase during muscle contraction (CS)
and the diastolic phase during muscle contraction (CD) in Figure
3b. Furthermore, BF during both systolic and diastolic phases during
the muscle relaxation phase showed a positive linear increase with
workload. However, during the muscle contraction phase it was similar
between workloads [11].
Regarding the variability in BF during dynamic exercise,
discrepancies in variability of BF between BBcycle and CRcycle are seen
at 30 W and 40 W (Figure 4a). ese higher variations in BF during the
BBcycle may be due to the large increase in BF in the systolic or diastolic
phase during muscle relaxation compared to muscle contraction at 30
W and 40 W. However, the variability in BF evaluated by CRcycle is
similar (almost 15% of coecients of variation) between workloads.
erefore, the approach for determination of optimal steady-state
BF, including the samplings for CRcycle ( in Figure 2a) is better,
even if the measurement of BF at rest is generally valid using BBcycle
samplings ( in Figure 2a).
In static/isometric exercise at 3 cpm (10s-on and 10s-o) described
in Figure 2b, the blood velocity prole clearly presents a clear systolic
and diastolic-like prole (blood pressure curve-like). is is due
to non-oscillation of the blood velocity prole (a non-disturbed
blood velocity prole), lacking rhythmical vessel compression even
under 10s-sustained isometric muscle contraction. Any mechanical
compression remains extravascular with increasing intramuscular
pressure. erefore, the variations in beat-by-beat blood velocity are
similar between %MVC (approximately 15%, range: 12.4−17.8%) and
show no relation to muscle contraction intensity (Figure 4b). is
nding supports changes in beat-by-beat blood velocity being lower
during 10s-sustained isometric muscle contraction, although a gradual
Osada T (2016) Dierence in muscle blood ow uctuations between dynamic and static thigh muscle contractions: How to evaluate exercise blood ow by Doppler
ultrasound
Volume 1(5): 4-7
Phys Med Rehabil Res, 2016 doi: 10.15761/PMRR.1000128
G
EMGs
Muscle force
(N)
(cm/s) 2
4
3
5
6
7 8
9
10
11
12
14
15
16
17
18
19
20
21
22
23
24
25
26
27 28
29 30
-0.04
-0.02
0
0.02
0.04
*
-50
0
50
100
150
200
10 s
Contraction Relaxation
13
1
-50
0
50
100
150
2
1 3 4
2 5 6 7 8 9
1 3 4 56 7 8 9
10
0
50
100
150
(cm/s)
10 s
Contraction Relaxation
MBV (Femoral artery)
<STATIC> Isometric knee extensor exercise at 50%MVC
0
Target
(%MVC)
50
Contraction Relaxation
EMGs
-10
0
10
Muscle power
Cardiac beat-by-beat cycle
90
100
110
120
130
140
150
160
170
180
180
160
140
120
100
Muscle contraction-relaxation cycle
20
21
22
23
24
25
2627
28
29
30
2 4
3
5
6
7
8
9
10
11
12
1314
15
16
17
18
19
1
10
Muscle contraction-relaxation cycle
Expanded as Figure 3a
Determination for blood flow fluctuations
Blood pressure
(mmHg)
80
100
120
1 2
11
12
Determination for blood flow fluctuations
Cardiac beat-by-beat cycle
3
a)
b)
*
MBV(Femoral artery)
<DYNAMIC> Isotonic knee extensor exercise at 20W
Blood pressure
(mmHg)
Figure 2. Simultaneous recording of blood velocity and hemodynamic parameters during exercise
a) <Dynamic> Isometric muscle contractions were clearly evident in the oscillations of mean blood velocity (MBV) due to muscle contraction-relaxation cycle superimposed on the cardiac
beat cycle. The MBV prole shows turbulence representing non-systole and diastole portions. b) <Static> Repeat isometric muscle contraction may indicate the clear MBV prole at each
beat corresponding to the cardiac systole-diastole. The blood velocity uctuations (coecients of variation) were determined by each muscle contraction-relaxation cycle (● or *) as well as
the cardiac beat-by-beat cycle (▲ or †). EMGs, surface electromyography; G, gap between contraction and relaxation. Figure 2a is drawn from our original unpublished data. Figure 2b is
adapted from Osada et al. [15], reproduced with permission for unrestricted use from BioMed Central.
Osada T (2016) Dierence in muscle blood ow uctuations between dynamic and static thigh muscle contractions: How to evaluate exercise blood ow by Doppler
ultrasound
Volume 1(5): 5-7
Phys Med Rehabil Res, 2016 doi: 10.15761/PMRR.1000128
-0.3
0.1
0
0.1
0.2
-50
0
50
100
150
200
90
110
130
150
170
-50
0
50
100
150
200
S
D
S
D
R RC C
Contraction
phase
Relaxation
phase
Diastolic phase
Systolic phase
Pre-
0
1
2
3
4
5
6
7
8
9
Blood flow (L/min)
Blood velocity (ml/min) B (mmHg) Muscle force (N), EMG
10 20 30 40 10 20 30 40W
R: Relaxation
C: Contraction
D: Diastole
S: Systole
a) b)
1s CD CS RS RD exercise
Figure 3. Alterations in blood velocity prole during muscle contractions-relaxation superimposed on cardiac cycle
a) A partial window in the simultaneous recording in Figure 2a was expanded to show the inuence on the blood velocity prole by muscle force curve, EMGs (muscle contractions) and
blood pressure curve (cardiac beat). Temporal blood velocity prole curves were closely related to the blood pressure curve and muscle force curve. The magnitude of the peak of blood
velocity proles for a single muscle contraction or muscle relaxation with single systolic or diastolic phase was found to be closely related to the peak systolic or second peak diastolic blood
pressure curve through muscle contraction-relaxation phases. Muscle contraction synchronized systole (CS) or diastole (CD); Muscle relaxation synchronized systole (RS) and diastole
(RD); EMGs, surface electromyography.
b) Blood ow was dierent between muscle contraction and muscle relaxation phases, consecutively provided in systolic and diastolic phase. Furthermore, blood ow during muscle
relaxation synchronized with systolic and diastolic phase showed a positive linear correlation with work rate. The values are expressed as means ± standard error.
Figure 3a is drawn from our original unpublished data. Figure 3b is adapted from Osada and Rådegran [13], reproduced with permission from The Physiological Society of Japan.
*
Worklod (W)
Coefficients of variation for blood flow (%)
%MVC
<DYNAMIC>
Isotonic exercise
10 30 50 70
10 20 30 40
0
10
20
30
Isometric exercise
10s-Contraction phase
10s-Relaxation phase 20s-CRcycle
BBcycle
BBcycle 1s-CRcycle
<STATIC>
*
*
***
a) b)
Figure 4. Blood ow uctuations (variations) determined by muscle contraction or cardiac contraction cycle during dynamic and static exercise
a) <Dynamic> isotonic exercise; Signicantly higher blood ow variability (coecients of variations) was determined by the cardiac beat-by-beat cycle (1-BBcycle) than muscle contraction-
relaxation cycle (1-CRcycle, 1s) at 30 W and 40 W, although blood ow variability was similar at each workload when determined for 1-CRcycle.
b) <Static> isometric exercise; There was a signicant dierence in the blood ow variability between 1-BBcycle during 10s-muscle contraction phase or 10s-muscle relaxation phase and
1-CRcycle (20s) at each percentage of maximum voluntary contraction (%MVC). *Signicant dierence (p < 0.05) - one way ANOVA. The values are expressed as means ± standard error.
Figure 4a adapted from Osada and Rådegran [12], reproduced with permission from Edizioni Minerva Medica. Figure 4b is our original unpublished data newly analyzed by the source in
Ref. [15].
Osada T (2016) Dierence in muscle blood ow uctuations between dynamic and static thigh muscle contractions: How to evaluate exercise blood ow by Doppler
ultrasound
Volume 1(5): 6-7
Phys Med Rehabil Res, 2016 doi: 10.15761/PMRR.1000128
but not signicant BF increase was seen during 10s-sustained isometric
muscle contraction [15]. It means that during 10s-sustained isometric
muscle contraction the BF measured by a few beat-by-beat samplings
may be equal to the essential BF value during the muscle contraction
phase.
In contrast, the variations in beat-by-beat BF evaluated by BBcycle
were signicantly higher in 10s-muscle relaxation than in 10s-isometric
muscle contraction at 10%MVC−50%MVC (Figure 4b). However,
the low value for beat-by-beat BF variation at 70%MVC suggests that
the higher blood velocity (prolonged vasodilation) was maintained
during the 10s-muscle relaxation phase. is result suggests that
during 10s-muscle relaxation the time course of the beat-by-beat BF
magnitude may markedly change (high attenuation ratio for beat-by-
beat BF from onset to end of 10s-muscle relaxation) below 50%MVC,
even if the major variation of the blood velocity consequently occurs
during the muscle relaxation phase.
e magnitude of BF at 10%MVC−50%MVC and the dierence in
BF variations between 10s-isometric muscle contraction and relaxation
may indicate the characteristic of exercise hyperemia (describing the
exponential decay of beat-to-beat BF magnitude) aer the end of
10s-muscle contraction during repeated isometric muscle contraction
(see the blood velocity magnitude in contraction and relaxation phase
in Figure 2b) [15]. As mentioned above, we must recognize that there
is a large dierence in single blood velocity value between rst and last
beats during the muscle relaxation phase, and the variations in beat-by-
beat BF are obviously high below 50%MVC.
e message from these ndings is that if a shorter duration of
beat-by-beat samplings during muscle relaxation were used for BF
determination, the resulting BF value would potentially be an over-
or under-estimation. We must remain aware that BF measured by
transient beat-by-beat sampling may not be expressing the essential BF
value during muscle relaxation phase.
As expected, variations in BF measured by CRcycle (* in Figure
2b) were signicant lower by BBcycle († in Figure 2b) during
10s-isometrcic muscle contraction (10%MVC and 30%MVC), and
during muscle relaxation (10%MVC−70%MVC). is demonstrated
that the comprehensive (net-) BF including the muscle contraction
and relaxation phase (i.e. CRcycle) will naturally be less variable in
comparison to the relatively high BF variations by BBcycle during
muscle contraction and/or relaxation. e optimal determination of
steady-state BF might require CRcycle sampling for repeated isometric
muscle exercise.
Speculated mechanisms for controlling BF during exer-
cise in relation to CRcycle
e cardiovascular responses to exercise are coordinated by
signals from central motor systems and peripheral sensors such as
baroreceptors, muscle chemocensors and mechanoreceptors being
integrated by the central nervous system with the degree of exercise/
muscle contraction intensity. e central nervous system may
subsequently inuence heart rate, cardiac output and vascular tone, and
thus skeletal muscle BF by altering sympathetic and parasympathetic
nervous activity. Furthermore, exercise-induced muscle hyperemia
has consequently been controlled by an inter-play between both “feed
back” and “feed forward” vascular control mechanisms which include
central mechanisms (neural and hormonal factors), as well as local
mechanisms involving the myogenic activity, and mediators derived
from the endothelium, muscle bers and/or muscle mechanical factors.
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 prole may be closely
related to the magnitude of intramuscular pressure variation (muscle
mechanical factors) and superimposed inuence of perfusion pressure
variation (pulsatile hemodynamic factors) [10,11,13-15,20-22]. During
steady-state, high intramuscular pressure during muscle contractions
50403020100
0
1
2
3
4
5
6
Worklod (W)
Blood flow (L/min)
0 01 02 03 04 05 06 07 08
0
1
2
3
4
%MVC
<DYNAMIC>
Isotonic exercise
<STATIC>
Isometric exercise
Contraction phase
Net
Relaxation phase
r=0.991, p<0.01
r=0.989, p<0.05
r=0.984, p<0.05
Net
p=NS
a) b)
Figure 5. Relationship between blood ow and exercise intensity
a) <Dynamic> There was a close positive linear relationship between net-blood ow and workload (r = 0.991, p < 0.01). b) <Static> There was a close positive linear relationship between
blood ow and %MVC during muscle relaxation (r = 0.989, p < 0.05) as well as combined muscle contraction-relaxation (r = 0.984, p < 0.05). However, blood ow during isometric muscle
contraction showed no change within the target %MVC. Statics (p < 0.05 and correlation coecient, r) - linear regression analysis. NS, not signicant; %MVC, percentage of maximum
voluntary contraction. The values are expressed as means ± standard error. Figure 5a adapted from Osada and Rådegran [12], reproduced with permission from Edizioni Minerva Medica.
Figure 5b adapted from Osada et al. [15], reproduced with permission for unrestricted use from BioMed Central.
Osada T (2016) Dierence in muscle blood ow uctuations between dynamic and static thigh muscle contractions: How to evaluate exercise blood ow by Doppler
ultrasound
Volume 1(5): 7-7
Phys Med Rehabil Res, 2016 doi: 10.15761/PMRR.1000128
may consequently temporarily reduce or even reverse the blood
velocity, depending on the relationship between the intramuscular
pressure and arterial blood pressure. e major extent of the blood velocity
and ow consequently occurs during the muscle relaxation phase.
Finally, the time and space-averaged blood velocity/ow
magnitude/dynamics may represent the phenomenon with blood
velocity changes (changes in vasodilation) due to CRcycle by above
mentioned integrated cardiovascular adjustment. e high time
resolution blood velocity prole in continuous recording may be
suitable for the investigation of BF regulation (time course in rapid
changes in blood velocity prole described in Figure 2).
Exercising blood ow versus exercise intensity
Limb conduit artery BF in the working muscle is one indicator of
metabolic demand in a local large muscle group. erefore, exercising
net-BF increased positively and linearly with increasing target intensity
(dynamic exercise as workload and static exercise as %MVC) as shown
in Figure 5. Interestingly, regarding static exercise, there was a close
positive linear relationship between net-BF and %MVC, and between
BF during muscle relaxation phase and %MVC, but not during the
isometric muscle contraction phase. e evaluation of the magnitude
for blood velocity proling was possible using Doppler ultrasound with
high temporal resolution. e important message from our ndings is
that accounting for the time resolution changes in the blood velocity
due to, i.e., CRcycle and/or BBcycle is valuable information for the
measurement of target exercise BF.
Acknowledgements
e authors acknowledge the long-term support of professor
emeritus Bengt Saltin, the sta of the Copenhagen Muscle Research
Centre, and the volunteers who participated in the studies. e study
was supported by the Danish National Research Foundation Grant 504-
14, as well as the “Excellent Young Researchers Overseas Visit Program”
in Scientic Research (No. 21-8285) 2010 and Scientic Research (C)
general (No. 15K01730) from MEXT and JSPS (T. Osada).
Authorship contributions
T. Osada contributed to the conception and design of the study,
data acquisition, analysis and interpretation. T. Osada and G. Rådegran
were involved in draing, revising and nalization of the manuscript.
Conicts of interest
e authors declare no conicts of interests in relation to the article.
References
1. Rådegran G, Saltin B (2000) Human femoral artery diameter in relation to knee
extensor muscle mass, peak blood ow, and oxygen uptake. Am J Physiol Heart Circ
Physiol 278: H162-167. [Crossref]
2. Ivey FM, Gardner AW, Dobrovolny CL, Macko RF (2004) Unilateral impairment of leg
blood ow in chronic stroke patients. Cerebrovasc Dis 18: 283-289. [Crossref]
3. Billinger SA, Kluding PM (2009) Use of Doppler ultrasound to assess femoral artery
adaptations in the hemiparetic limb in people with stroke. Cerebrovasc Dis 27: 552-
558. [Crossref]
4. Ivey FM, Hafer-Macko CE, Ryan AS, Macko RF (2010) Impaired leg vasodilatory
function after stroke: adaptations with treadmill exercise training. Stroke 41: 2913-
2917. [Crossref]
5. Durand MJ, Murphy SA, Schaefer KK, Hunter SK, et al. (2015) Impaired hyperemic
response to exercise post stroke. PLoS One 10: e0144023. [Crossref]
6. Osada T, Katsumura T, Hamaoka T, Inoue S, Esaki K, et al. (1999) Reduced blood
ow in abdominal viscera measured by Doppler ultrasound during one-legged knee
extension. J Appl Physiol 86: 709-719. [Crossref]
7. Osada T, Katsumura T, Hamaoka T, Murase N, Naka M, et al. (2002) Quantitative
eects of respiration on venous return during single knee extension-exion. Int J Sports
Med 23: 183-190. [Crossref]
8. Osada T, Rådegran G (2002) Femoral artery inow in relation to external and total
work rate at dierent knee extensor contraction rates. J Appl Physiol 92: 1325-1330.
[Crossref]
9. Osada T, Katsumura T, Murase N, Sako T, Higuchi H, et al. (2003) Post-exercise
hyperemia after ischemic and non-ischemic isometric handgrip exercise. J Physiol
Anthropol Appl Human Sci 22: 299-309. [Crossref]
10. Osada T (2004) Muscle contraction-induced limb blood ow variability during dynamic
knee extensor. Med Sci Sports Exerc 36: 1149-1158. [Crossref]
11. Osada T, Rådegran G (2005) Alterations in the rheological ow prole in conduit
femoral artery during rhythmic thigh muscle contractions in humans. Jpn J Physiol
55: 19-28. [Crossref]
12. Osada T, Rådegran G (2006) Dierences in exercising limb blood ow variability
between cardiac and muscle contraction cycle related analysis during dynamic knee
extensor. J Sports Med Phys Fitness 46: 590-597. [Crossref]
13. Osada T, Rådegran G (2006) Alterations in the blood velocity prole inuence the
blood ow response during muscle contractions and relaxations. J Physiol Sci 56: 195-
203. [Crossref]
14. Osada T, Rådegran G (2009) Femoral artery blood ow and its relationship to
spontaneous uctuations in rhythmic thigh muscle workload. Clin Physiol Funct
Imaging 29: 277-292. [Crossref]
15. Osada T, Mortensen SP, Rådegran G (2015) Mechanical compression during repeated
sustained isometric muscle contractions and hyperemic recovery in healthy young
males. J Physiol Anthropol 34: 36. [Crossref]
16. Andersen P, Saltin B (1985) Maximal perfusion of skeletal muscle in man. J Physiol
366: 233-249. [Crossref]
17. Andersen P, Adams RP, Sjøgaard G, Thorboe A, Saltin B (1985) Dynamic knee
extension as model for study of isolated exercising muscle in humans. J Appl Physiol
59: 1647-1653. [Crossref]
18. Rådegran G (1997) Ultrasound Doppler estimates of femoral artery blood ow during
dynamic knee extensor exercise in humans. J Appl Physiol 83: 1383-1388.[Crossref]
19. Rådegran G, Saltin B (1998) Muscle blood ow at onset of dynamic exercise in
humans. Am J Physiol 274: H314-322. [Crossref]
20. Osada T, Saltin B, Mortensen SP, Rådegran G (2012) Measurement of the exercising
blood ow during rhythmical muscle contractions assessed by Doppler ultrasound:
Methodological considerations. J Biomed Sci Eng 5: 779-788.
21. Osada T, Saltin B, Rådegran G (2013) Assessment of voluntary rhythmic muscle
contraction-induced exercising blood ow variability measured by Doppler ultrasound.
Open J Mol Integr Physiol 3: 158-165.
22. Osada T, Murase N, Kime R, Katsumura T, Rådegran G (2014) Blood ow dynamics in
the limb conduit artery during dynamic knee extensor exercise assessed by continuous
Doppler ultrasound measurements. J Phys Fitness Sports Med 3: 409-421.
Copyright: ©2016 Osada T. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use,
distribution, and reproduction in any medium, provided the original author and source are credited.
... Our previous studies demonstrated rapid changes in the time courses of blood velocity profiles in the conduit femoral artery, with muscle contraction and/or muscle relaxation superimposed cardiac cycle during exercise in different states of muscle contraction time/frequency and workload [9,11,12,51]. In dynamic exercise at 30 contractions per minute (1-s contraction-1-s relaxation cycle), the continuous blood velocity curve during repeated muscle contractions fluctuated rapidly due to the muscle force curve, which indicated that the muscle contraction restricted LBF (temporal reduced blood velocity), and consequently muscle relaxation may induce an increase in LBF (higher blood velocity) [11,13,51]. ...
... Our previous studies demonstrated rapid changes in the time courses of blood velocity profiles in the conduit femoral artery, with muscle contraction and/or muscle relaxation superimposed cardiac cycle during exercise in different states of muscle contraction time/frequency and workload [9,11,12,51]. In dynamic exercise at 30 contractions per minute (1-s contraction-1-s relaxation cycle), the continuous blood velocity curve during repeated muscle contractions fluctuated rapidly due to the muscle force curve, which indicated that the muscle contraction restricted LBF (temporal reduced blood velocity), and consequently muscle relaxation may induce an increase in LBF (higher blood velocity) [11,13,51]. ...
... Previous evidence revealed that, although both types of leg exercises were able to increase femoral artery blood flow and velocity, isometric exercise produced greater blood flow fluctuations than isotonic exercise. 28 Another potential mechanism involves differences in muscle deoxygenation. Lowintensity isotonic forearm exercise demonstrated reduced forearm venous oxygen saturations during the ambient condition, which further reduced during the ischemic condition. ...
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... do not easily allow LBF measurement in the leg conduit artery, due to the difficulty of fixing the scanning probe to the hip joint [16] [18] [19] [20]. The patient performed exercise with the hips at a 100˚ angle, the thigh positioned horizontally with the knee joint bent at an approximately 110˚ angle, and their foot and ankle secured to upper and lower rods with the use of a custom-designed Meiko-100 knee-extension ergometer (Meiko Co. Ltd., Tokyo, Japan) [13]. ...
... A previous evidence reveals that although both types of leg exercise can increase femoral artery blood flow and velocity, isometric exercise generates more blood flow fluctuation than that of isotonic exercise. 41 In addition, low and moderate intensity of isometric exercise increased blood velocity and vascular conductance during leg exercise. 42 Regarding muscular deoxygenation, decreased muscular oxygen saturation was found during low, moderate, and high intensity of isometric exercise. ...
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... In addition, static contraction is the type of contraction most related to fatigue in humans [73][74][75]. Therefore, it is possible to hypothesize that static contraction increased muscle blood flow [76,77] by fatigue mechanisms [78][79][80] and promoted the clearance of muscle cytokines during contraction [81]. ...
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