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The research program in the
Cardiorespiratory and Vascular Dynamics Laboratory examines the mechanisms
responsible for adapting to the stress of physical activity or changes in
posture. We have developed a wide range of noninvasive techniques that allow us
to explore control mechanisms in transitions between rest and exercise, or
between the supine and upright posture. Our research has application to
understanding why the sensation of effort might be greater during the
transition to exercise in individuals who are on medication to treat
cardiovascular diseases or people with diseases that impair the pumping
ability of the heart. Our research that explores the cardiovascular responses
to the upright posture has widespread application to the many individuals who
experience dizziness or faint when they go quickly to standing after lying in
bed or resting in a chair. Falls associated with dizziness in older people
are serious problems as the risk of bone fractures is greatly increased.
Below you can find more detail about our research program including our
experiments that will soon be on the International Space Station as well as
experiments taking place in Toulouse, France during 2005 in the ESA
web site for WISE 2005 or go to candidate
recruitment information for the long-term bed rest study of women. Or to
the CSA site.
And the profile of our work at the CSA site.
March 13 2007: UW Campus Day Presentation click here
Slides for the presentation "Training and Overtraining for the
Marathon and Cross-Country Skiing" can be obtained here
Click on the items in the table below to jump to a selected topic or
simply scroll down.
The Lab (Being updated 2007)
The Cardiovascular and Respiratory
Dynamics Lab, in the Department of Kinesiology at the University of
Waterloo has been the home of many outstanding students who have left
Waterloo for prestigious positions around the world. The former Ph.D.
students include Dr. Gary Butler (Ph.D. 1992) who completed his MD
and is associated with the Airline Pilots' Association study of the effects
of radiation on pilot health. Dr. Andrew Blaber (Ph.D 1994) is an Assistant
Professor at Simon Fraser University and he will be working with us on the Space Station project. Dr. Kevin Shoemaker (Ph.D. 1996)
returned to Canada after an NSERC PDF position at Hershey Medical Center.
He is now an Associate Professor at University of Western Ontario and also
works on the Space Station project. Dr. Maureen
MacDonald (Ph.D. 1998) also received an NSERC PDF and is now on faculty at
McMaster University. Dr. Mike Tschakovsky (Ph.D. 1998) worked with Dr. Mike
Joyner at the world famous Mayo Clinic under support from an NSERC PDF. He
is now an Associate Professor at Queen's University. Each of Kevin, Maureen
and Mike also won the Young Investigator Award from the Canadian Society
for Exercise Physiology based on work from their Ph.D. thesis experiments.
This is a significant achievement as they competed against the best
graduate students from across Canada. More recently, Stephane Perrey (PhD
2000 from Université Franche-Comté) is an assistant professor in the
Faculté des Sciences du Sport, Montpellier, France. Debbie O'Leary (PhD
2001) completed a PDF at UWO and is now a faculty member at Brock
University. The most recent PhD graduate is Michael Edwards who has taken a
position of scientist with a pharmaceutical company in Texas.
Recent M.Sc. graudates include Dave Quinlan, Darran
Fischer, Kourtney Dupak, and Louis Mattar. Ken Dyson has
moved up from MSc to PhD student. There are also many senior undergraduate
students in the lab.
Recent post-docs have included Dr. Mikko Tulppo
from University of Oulu, Finland and Dr. Zbigniew Topor who is now back in
Calgary and Pascaline Kerbeci from France. The lab technicians include Dave Northey and Myra
Gonzales, and Research Associate Danielle Greaves.
Research Focus
The focus of our research is on
the ability of the cardiovascular and respiratory systems to adapt to
changing environments. We attempt to integrate the responses of the
different components of these systems. One application of this approach
examines the body's response at the onset of exercise. This includes the
oxygen uptake response measured breath-by-breath, as well as beat-by-beat
changes in cardiac output and blood flow distribution patterns in terms of
how they impact on the adaptive processes of the energy supply mechanisms
(oxidative metabolism versus phosphocreatine depletion versus anaerobic
glycolysis). Another application looks at the mechanisms involved in heart
rate and blood pressure regulation. Here, various techniques including
sequence analysis, cross spectral analysis, autoregressive modelling, and
nonlinear methodologies including fractal analysis and chaos mathematics
have been applied. With regard to the fractal analysis, the methodology
"coarse graining spectral analysis" (CGSA) was developed in our
lab by Dr. Yoshi Yamamoto (now at the University of Tokyo). This has
provided us with a window through which we can explore the variations that
exist in time series data to provide an assessment of overall
cardiovascular system complexity.
Space Physiology Takes Off - Maybe This Time!
Our
space research program received a boost when we had a project approved in
1999 for flight on the International Space Station (ISS). Unfortunately,
major construction delays have caused all but the very simplest experiments
to be cancelled. Our project approved back in January 2002 is working its
way through the detailed procedure of getting the flight experiment ready
and we hope to continue recruiting astronauts during 2007-08. The research
funding from the Canadian
Space Agency allowed us to develop the methods for these future space
flight experiments. As astronauts are constructing the ISS they will spend
several months in the reduced gravity environment of space. This will have
major consequences as the cardiovascular system deconditions in space. In
normal daily life, the reflex mechanisms regulate blood pressure so that
blood flow to the brain can be maintained as we sit, stand or walk in the
upright posture. This is normally accomplished by changes in heart rate and
constriction of blood vessels. Without the stress of gravity, these
reflexes lose their ability to make quick changes so that when astronauts
return to Earth, there is an increased risk that they will faint. The
following indicate the experiments that have been approved in the most
recent competition.
We have been selected to perform most of the
cardiovascular measurements as part of the Long-Term
Bed Rest Study of Women taking
place in Toulouse, France beginning February 22, 2005. Women will spend 60
days in bed, with one group receiving regular exercise countermeasures
using the LBNP-treadmill device of Dr. Alan Hargens from San Diego. Our
project "Vascular remodelling and functional consequences of long-term
bed rest" will be in collaboration with Drs. Kevin Shoemaker, Jim
Rush, Philippe Arbeille and Marc-Antoine Custaud. On the right is a picture
of some of the team members standing outside the MEDES clinic in Toulouse.
On the front left is Valerie an ultrasound technician from Pr. Arbeille's
lab, Danielle (technician from Waterloo and the person most responsible for
the day to day success of the study), Pascaline a PhD student from Tours,
Kevin Shoemaker, Philippe Arbeille, back row Richard Hughson and Louis a
MSc student from Waterloo.
- 24-hour heart rate variability and physical
activity. This project will examine the pattern of beat-by-beat
changes in heart rate to determine whether there have been changes in
the balance between the parasympathetic and sympathetic neural control
of the heart. Measurements will be made on the ground before flight,
at regular intervals on ISS and after return.
- Arterial baroreflex in space. Due to the
limited time available for experiments in space, we will restrict our
estimates of the arterial baroreflex response to simply examining the
heart rate to blood pressure response during 5-minutes rest and
5-minutes of paced breathing at two time points during the flight.
These measurements will allow comparisions with similar experiments on
the ground before flight and after return.
- Arterial Baroreflex on Earth. These
experiments will examine changes in the vascular and heart rate
components of the arterial baroreflex by measuring continuous cardiac
output and peripheral vascular resistance during lower body negative
pressure (LBNP) tests as soon as possible after return to Earth. We
will also monitor changes in cerebral blood flow as arterial blood
pressure and arterial carbon dioxide levels change.
- Changes in central venous compliance. These
experiments will explore the role of the central veins in causing poor
blood pressure regulation when astronauts return from space. We will
monitor central venous pressure and determine the venous volume during
application of low levels of LBNP immediately on return from the ISS.
After spending a prolonged period of time in space with the central
blood volume elevated because gravity has not been pushing the blood
toward the lower regions of the body, we expect to see
"floppy" veins that will have difficulty maintaining
sufficient filling pressure for the heart. The factors assessed by
these experiments on return to Earth could point to mechanisms
responsible for greater incidence of dizziness and fainting when
astronauts return from space, or when people rise quickly from bed in
the morning.
We have been selected to perform most of the
cardiovascular measurements as part of the Long-Term
Bed Rest Study of Women taking place in Toulouse, France beginning
February 22, 2005. Women will spend 60 days in bed, with one group
receiving regular exercise countermeasures using the LBNP-treadmill device
of Dr. Alan Hargens from San Diego (see below). Our project "Vascular
remodelling and functional consequences of long-term bed rest" will be
in collaboration with Drs. Kevin Shoemaker, Jim Rush, Philippe Arbeille and
Marc-Antoine Custaud.
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This picture shows the space research in action. Heather Naylor,
Maureen MacDonald, Dave Northey and Mikko Tulppo take measurements with
Derek Kimmerly on the tilt table with the LBNP box. We are studying the
relationship between central venous pressure and volume and the
cardiopulmonary and arterial baroreflexes after 4-hours head down tilt.
We hope to conduct an experiment very similar to this on astronauts
before they go to the International Space Station and immediately after
they return.
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Our research in Waterloo has found a place in
the French/Russian space programs with examinations of heart rate and blood
pressure variability and the arterial baroreflex, and in the NASA/Russian
space programs with our breath-by-breath software for exercise testing. We
recently went to the MEDES clinical
research facility in Toulouse, France to take part in a women's 9-day
head-down tilt bed rest study. We are also working with Dr. Alan Hargens'
team at UCSD on a 30-day bed rest study
in which one member of a twin pair is doing supine treadmill running in a
lower body negative pressure chamber as a potential countermeasure to
prevent cardiovascular deconditioning while the other twin serves as an
inactive control.
Research Funding
Funding for the research
currently comes from the Natural Sciences and Engineering Research Council
(NSERC) and the Canadian Space Agency. Support from the Heart and Stroke
Foundation of Ontario (HSFO) goes specifically to projects looking at brain
blood flow and the effects of age and gender. NSERC funding supports the
gas exchange and blood flow dynamics work including major items of
equipment (mass spectrometer, Doppler flow and image systems). The
laboratory has received a total of $4.5 million in funding since Dr.
Hughson came to Waterloo in 1977.
Breath-by-Breath Gas Exchange
Beginning in 1981, we developed
a computer based system to perform breath-by-breath analysis of ventilation
and respiratory gas exchange. This original system was based on a data
acquisition computer in combination with a number crunching computer. Since
1990, the new software written for the PC computer has been available to
other laboratories (about 50 around the world) as part of a package with
the Marquette Electronics Inc. respiratory mass spectrometer.
Unfortunately, Marquette has been purchased by GE and the mass spectrometer
system is no longer produced. We also collaborated on development of a
quadrupole mass spectrometer and software that will be in the GASMAP system
on the International Space Station.
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This picture shows Andrew Betik (who finished his M.Sc. in May 2001) on
the cycle ergometer with Dr. Richard Hughson and Dave Northey on the right.
The MGA-1100 breath-by-breath system is shown. This mass spectrometer-based
system was originally purchased in 1982 with the assistance of an NSERC
equipment grant. Another NSERC grant supported the purchase of the cycle
ergometer.
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Blood Flow Control
This area of research has advanced
since our acquisition in 1990 of a Doppler velocity measurement system to
include simultaneous, and continuous, measurement of arterial cross sectional
area with a Toshiba SSH-140A colour Doppler echo imaging system. With this
approach, we have now been able to quantify the time course of the increase
in blood flow to exercising forearm and leg muscles. One of the most exciting
recent findings is that the muscle pump, advocated by some to be the sole
mechanism responsible for the initial increase in blood flow with muscle
contraction, actually works in concert with an immediate (within 2 s)
vasodilation (this was work from former PhD students, Kevin Shoemaker and
Mike Tschakovsky). We have also shown that there is a tight linear
relationship over a wide range of metabolic demands between the supply of
oxygen (calculated from the time course of increased blood flow times
arterial oxygen content) and the muscle utilization of that oxygen. This
provides further support for our model of rate limiting steps described above
from whole body exercise. Work in progress is attempting to evaluate the
blood flow responses in working and non-working vascular beds.
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Here, Heather Naylor is measuring the diameter of the femoral artery
with our Toshiba SSH-140A imaging system while Andrew Betik works on our
custom built "kicking" ergometer. This ergometer is electrically
braked and allows for one- or two-leg exercise with either or both of knee
extension or flexion. The Doppler system was purchased with the support of
a large equipment grant from NSERC. The ergometer was built with the
assistance of the Department of Kinesiology.
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This is Mike Tschakovsky measuring blood flow into the forearm with the
Multigon system. Mike Chambers is the willing subject while Debbie O'Leary
looks on. The hand grip device was built with support from an American
College of Sports Medicine grant to Mike Tschakovsky for a proposal based
on his Ph.D. thesis research. Mike T has gone on to successfully complete
PDF work at the Mayo Clinic with Dr. Mike Joyner and he has taken up a
faculty position at Queen's University.
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Heart Rate and Blood Pressure Control
In the past 10 years, we have
refined and developed a number of tools that have allowed us to explore the
beat-by-beat interactions that occur within the cardiovascular system, and
to better understand how this interaction is involved in the regulatory
process. Beginning with the work of Gary Butler with his MSc thesis and
into his PhD thesis, we have done some short-term bed rest studies in
Waterloo. In 1990, we had the opportunity to collaborate with Pr. C. Gharib
in Lyon, France, and to be involved with the French medical space research
group (MEDES) in Toulouse during the MEDES-CNES 28 day head down bedrest.
The methodologies that we had developed related to spontaneous baroreflex
function and coarse graining spectral analysis allowed us to contribute by
exploring the autonomic nervous function during a period of cardiovascular
deconditioning. This work provided the opportunity for continued
involvement with the French/Russian space programs (e.g. see J. Appl. Physiol.
77: 69-77, 1994).
Continued work in this area is being carried on by
Debbie O'Leary and Dr. Mikko Tulppo. This research focuses on the
cardiorespiratory interactions by simultaneous measurements of heart rate,
blood pressure, cardiac stroke volume by Doppler methods, respiration, and
cerebral blood flow.
Fire Fighter Research
We
have recently become aligned with Dr. Beth
Weckman from Mechanical Engineering on her major initiative for a live
fire research centre. Dr. Weckman will study the behaviour of fires while
we study the responses of the fire fighters. Mike Williams-Bell and several senior undergraduates have been busy testing student
volunteers and incumbent firefighters to determine the demands of the Candidate Physical Abilities Test (CPAT) that was developed by a joint initiative of the International Association of Fire Chiefs and the International Association of Fire Fighters. The CPAT test is a bone fide occupational requirement and more information can be found at the
UW Fitness website.
This text is WHITE and is just to fill space. Can remove if I figure out how to palce figures! We
have recently become aligned with from Mechanical Engineering on her major initiative for a live
fire research centre. Dr. Weckman will study the behaviour of fires while
we study the responses of the fire fighters. Mike Williams-Bell and several senior undergraduates have been busy testing student
volunteers and incumbent firefighters to determine the demands of the Candidate Physical Abilities Test (CPAT) that was developed by a joint initiative of the International Association of Fire Chiefs and the International Association of Fire Fighters. The CPAT test is a bone fide occupational requirement and more information can be found at the
Journal Publications from the Cardiovascular
and Respiratory Dynamics Laboratory from 1991-2001 (sorry but there hasn't
been time to update this for a while). Some papers are listed with links to
download PDF format copies. Be aware that publishers might place
restrictions on access to some papers.
- Tordi, N., Perrey,
S., Harvey, A., and Hughson, R.L. Oxygen uptake kinetics during two
bouts of heavy cycling separated by fatiguing sprint exercise in
humans. J Appl Physiol 2002 Oct 11 [epub ahead of print] PDF
- Edwards, M.R.,
Shoemaker, J.K., and Hughson, R.L. Dynamic modulation of
cerebrovascular resistance as an index of autoregulation under tilt
and controlled PETCO2. Am J Physiol Regul Integr Comp Physiol.
283: R653-R662, 2002. PDF
- Edwards, M.R.,
Martin, D.H., and Hughson, R.L. Cerebral hemodynamics and resistance
exercise. Med. Sci. Sports Exerc. 34: 1207-1211, 2002. PDF
- Sigaudo-Roussel, D.,
Maillet, A., Custaud, M.A., Frutoso, J., Güell, A., Kaspranski, R.,
Hughson, R.L., Gharib, C., and Fortrat, J.O. Heart rate variability
after prolonged spaceflights. Eur J Appl Physiol. 86: 258-265,
2002.
- Lin, DC, Hughson,
RL. A phenomenology model of normal sinus rhythm in healthy humans. IEEE
Trans. Biomed. Eng. 49: 97-109, 2002.
- Hughson, R.L.,
Edwards, M.R., O'Leary, D.D., and Shoemaker, J.K. Critical analysis of
cerebrovascular autoregulation during repeated head up tilt. Stroke
32: 2403-2408, 2001. PDF
- Perrey, S.,
Tschakovsky, M.E., and Hughson, R.L. Ischemic muscle chemoreflex
elevates muscle blood flow and oxygen uptake during onset of exercise
in nonischemic human forearm. J. Appl. Physiol. 91: 2010-2016,
2001. PDF
- Perrey, S., Betik,
A., Candau, R., Rouillon, J.D., and Hughson, R.L. Comparison of oxygen
uptake kinetics during concentric and eccentric cycle exercise. J.
Appl. Physiol. 91: 2135-2142, 2001. PDF
- Shoemaker, J.K.,
O'Leary, D.D., and Hughson, R.L. PETCO2 inversely affects MSNA
response to orthostatic stress. Am J Physiol Heart Circ Physiol
281: H1040-H1046, 2001. PDF
- Blaber, A.P.,
Bondar, R.L., Moradshahi, P., Serrador, J.M., and Hughson, R.L.
Inspiratory CO2 increases orthostatic tolerance during repeated tilt. Aviat.
Space Environ Med 72: 985-991, 2001.
- K. H. Doyon, S.
Perrey, D. Abe, and R. L. Hughson. Field testing of VO2peak in cross
country skiers with portable breath-by-breath system. Can. J. Appl.
Physiol. 26: 1-11, 2001.
- J. O. Fortrat, D.
Sigaudo, R. L. Hughson, A. Maillet, Y. Yamamoto, and C. Gharib. Effect
of prolonged head-down bed rest on complex cardiovascular dynamics. Autonomic
Neuroscience 86: 192-201, 2001.
- Tulppo, M.P., R.L.
Hughson, T.H. Mäkikallio, K.E. Juhani Airaksinen, T. Seppänen and H.V.
Huikuri. Effects of exercise and passive head-up tilt on fractal and
complexity properties of heart rate dyanmics. Am. J. Physiol.:
Heart Circ. Physiol. 280: H1081-H1087, 2001. PDF
- Green, H.J., B. Roy,
S. Grant, R. Hughson, M. Burnett, C. Otto, A. Pipe, D. McKenzie and M.
Johnson. Increases in submaximal cycling efficiency mediated by
altitude acclimatization. J. Appl. Physiol. 89: 1189-1197,
2000. PDF
- MacDonald MJ, Green
HJ, Naylor HL, Otto C, and Hughson RL. Reduced oxygen uptake during
steady state exercise after 21-day mountain climbing expedition to
6,194 m. Can J Appl Physiol 26: 143-156, 2001.
- Shoemaker JK,
O'Leary DD, and Hughson RL. PETCO2 inversely affects MSNA response to
orthostatic stress. Am J Physiol Heart Circ Physiol 281: 2001. PDF
- Tulppo MP,
Mäkikallio TH, Seppänen T, Shoemaker JK, Tutungi E, Hughson RL, and
Huikuri HV. Effects of pharmacological adrenergic and vagal modulation
on fractal heart rate dynamics. Clin Physiol 21: 2001.
- Griffin L, Garland
SJ, Ivanova T, and Hughson RL. Blood flow in the triceps brachii
muscle in humans during sustained submaximal isometric contractions. Eur
J Appl Physiol. 84:432-7, 2001.
- van Beekvelt MCP,
Shoemaker JK, Tschakovsky ME, Hopman MTE, and Hughson RL. Blood flow
and muscle oxygen uptake at the onset and end of moderate and heavy
dynamic forearm exercise. Am J Physiol Regul Integr Comp Physiol
280: 2001. PDF
- Hughson RL,
Tschakovsky ME, and Houston ME. Regulation of oxygen consumption at
the onset of exercise (Invited Review). Exercise and Sports
Science Reviews 29: 2001.
- Lin, D.C. and
Hughson, R.L. Using gaussians to model increment distribution of the
long-term R-wave interval in healthy humans. Chaos, Solitons and
Fractals 12: 1335-1345, 2001.
- MacDonald,M.J.,
Naylor,H.L., Tschakovsky,M.E., and Hughson,R.L. Evidence that
peripheral circulatory factors limit the rate of increase in muscle O2
uptake at the onset of heavy exercise. J. Appl. Physiol. 90:
83-89, 2001. PDF
- MacDonald, M.J.,
M.A. Tarnopolsky and R.L. Hughson. Effect of hyperoxia and hypoxia on
leg blood flow and pulmonary and leg oxygen uptake at the onset of
kicking exercise. Can. J. Physiol. Pharmacol. 78: 67-74, 2000
- Tschakovsky, M.E.
and R.L. Hughson. Venous emptying mediates a transient vasodilation in
the human forearm. Am. J. Physiol.: Heart Circ. Physiol. 279:
1007-1014, 2000. PDF
- Lucy,S.D.,
Hughson,R.L., Kowalchuk,J.M., Paterson,D.H., and Cunningham,D.A. Body
position and cardiac dynamic and chronotropic responses to
steady-state isocapnic hypoxaemia in humans. Exp. Physiol. 85:
227-237, 2000.
- McGill,S.M.,
Hughson,R.L., and Parks,K. Lumbar erector spinae oxygenation during
prolonged contractions: implications for prolonged work. Ergonomics
43: 486-493, 2000.
- McGill,S.M.,
Hughson,R.L., and Parks,K. Changes in lumbar lordosis modify the role
of the extensor muscles. Clin. Biomech. 15: 777-780, 2000.
- S. Houtman, B.
Oeseburg, R. L. Hughson, and M. T. E. Hopman. Tilt induced changes in
the sympathetic nervous system activity and cardiovascular stability
in spinal cord injured and able-bodied individuals. Clin. Auton.
Res. 10: 207-212, 2000.
- Hughson R.L., D.D.
O'Leary, A.C. Betik and H. Hebestreit. Kinetics of oxygen uptake at
the onset of exercise near or above peak oxygen uptake. J. Appl.
Physiol. 88: 1812-1819, 2000. PDF
- Hughson, R.L. and
R.L. Bondar. (Invited Review) Autonomic nervous system function
in space. Handbook of Clinical Neurology Vol. 74 (30): 273-305,
1999. O. Appenzeller, ed.
- Tschakovsky, M. and
R.L. Hughson. Invited Review: Interaction of factors
determining oxygen uptake at the onset of exercise. J. Appl.
Physiol. 86: 1101-1113, 1999. PDF
- Hughson, R.L. (Invited
Review) Oxygen uptake kinetics during exercise in humans in
relatio nto muscle blood flow. J. Exerc. Sci. 9: 1-12, 1999.
- MacDonald, M.J.,
M.A. Tarnopolsky and R.L. Hughson. Effect of hyperoxia and hypoxia on
leg blood flow and pulmonary and leg oxygen uptake at the onset of
kicking exercise. Can. J. Physiol. Pharmacol. In press, 1999
- Serrador, J.M., H.C.
Finlayson and R.L. Hughson. Physical activity is a major contributor
to the ultra-low frequency components of heart rate variability. Heart
82: e9, 1999. (http://www.heartjnl.com/cgi/content/full/82/6/e9)
- O'Leary, D.D., D.C.
Lin, and R.L. Hughson. Determination of baroreflex gain using
autoregressive moving average analysis during spontaneous breathing. Clin.
Physiol. 19: 369-377, 1999.
- Hicks, A., S.
McGill, and R.L. Hughson. Tissue oxygenation by near-infrared
spectroscopy and muscle blood flow during isometric contractions of
the forearm. Can. J. Appl. Physiol. 24: 216-230, 1999.
- MacDonald, M.J.,
M.A. Tarnopolsky, H.J. Green, and R.L. Hughson. Comparison of femoral
blood gases and muscle near infrared spectroscopy at the onset of
exercise in humans. J.Appl.Physiol. 86: 687-693, 1999. PDF
- Naylor, H.L., J.K.
Shoemaker, R.W. Brock, and R.L. Hughson. Prostaglandin inhibition
causes an increase in reactive hyperaemia after ischaemic exercise in
human forearm. Clin. Physiol. 19: 211-220, 1999.
- Hughson, R.L. and
M.E. Tschakovsky. Cardiovascular dynamics at the onset of exercise. Med.
Sci. Sports Exerc. 31: 1005-1010, 1999.
- Shoemaker, J.K. and
R.L. Hughson. Adaptation of blood flow during the rest to work
transition in humans. Med. Sci. Sports Exerc. 31: 1019-1026,
1999
- Tschakovsky, M. and
R.L. Hughson. Ischemic muscle chemoreflex response elevates blood flow
in non-ischemic exercising human forearm muscle. Am. J.
Physiol.Heart Circ. Physiol. 277: H635-H642, 1999. PDF
- Parlow, J.L., G.
Begou, P. Sagnard, J.M. Cottet-Emard, J.C. Levron, G. Annat, F.
Bonnet, M. Ghignone, R.L. Hughson, J.P. Viale, L. Quintin. Cardiac
baroreflex during the postoperative period in patients with
hypertension. Anesthesiology 90: 681-692, 1999.
- Brock, R.W., M.E.
Tschakovsky, J.K. Shoemaker, J.R. Halliwill, M.J. Joyner, and R.L.
Hughson. Effects of acetylcholine and nitric oxide on forearm blood
flow at rest and after a single muscle contraction. J.Appl.Physiol.
85: 2249-2254, 1998. PDF
- Hebestreit, H., S.
Kriemler, R.L. Hughson, and O. Bar-Or. Kinetics of oxygen uptake at
the onset of exercise in boys and men. J.Appl.Physiol. 85:
1833-1841, 1998. PDF
- Hughson, R.L., M.J.
MacDonald, R.C. Ter-Vrugt, and D.R. Northey. Central venous
pressure-volume relationship with head-down tilt and LBNP. J.Gravit.Physiol.
In Press: 1998.
- MacDonald, M.J.,
J.K. Shoemaker, M.E. Tschakovsky, and R.L. Hughson. Alveolar oxygen
uptake and femoral artery blood flow dynamics in upright and supine
leg exercise in humans. J.Appl.Physiol. 85: 1622-1628, 1998.
- Pavy-Le Traon, A.,
D. Sigaudo, P. Vasseur, A. Maillet, J.O. Fortrat, R.L. Hughson, G.
Gauquelin-Koch, and C. Gharib. Cardiovascular responses to orthostatic
tests after a 42-day head-down bed-rest. Eur.J.Appl.Physiol.Occup.Physiol.
77: 50-59, 1998.
- Serrador, J.M., R.L.
Bondar, and R.L. Hughson. Ventilatory response to passive head up
tilt. Adv.Exp.Med.Biol. 450: 133-139, 1998.
- Shoemaker, J.K.,
M.E. Tschakovsky, and R.L. Hughson. Vasodilation contributes to the
rapid hyperemia with rhythmic contractions in humans. Can.J.Physiol.Pharmacol.
76: 418-427, 1998.
- Sigaudo, D., J.O.
Fortrat, A.M. Allevard, A. Maillet, J.M. Cottet-Emard, A. Vouillarmet,
R.L. Hughson, G. Gauquelin-Koch, and C. Gharib. Changes in the
sympathetic nervous system induced by 42 days of head-down bed rest. Am.J.Physiol.Heart
Circ.Physiol. 274: H1875-H1884, 1998. PDF
- Shoemaker, J.K, M.E.
Tschakovsky and R.L. Hughson. Vasodilation contributes to the rapid
hyperaemia with rhythmic contractions in humans. Can. J. Physiol.
Pharmacol. In press, 1998.
- Sigaudo, D. J.-O.
Fortrat, A.-M. Allevard, A. Maillet, J.-M. Cottet-Emard, A.
Vouillarmet, R.L. Hughson, G. Gauquelin-Koch and C. Gharib. Changes in
the sympathetic nervous system induced by 42-days of head-down
bed-rest. Am. J. Physiol.: Heart Circ. Physiol. In press, 1998.
- Shoemaker, J.K.,
M.J. MacDonald and R.L. Hughson. Time course of brachial artery
diameter responses to rhythmic handgrip exercise in humans. Cardiovasc.
Res. 35: 125-131, 1997.
- Fortrat, J.O., Y.
Yamamoto and R.L. Hughson. Respiratory influences on nonlinear
dynamics of heart rate variability. Biol. Cybern. 77: 1-10,
1997.
- MacDonald, M., P.K.
Pedersen and R.L. Hughson. Acceleration of oxygen uptake kinetics in
heavy submaximal exercise by hyperoxia and prior high intensity
exercise. J. Appl. Physiol. 83: 1318-1325, 1997.
- Shoemaker, J.K.,
J.R. Halliwill, R.L. Hughson and M.J. Joyner. Contributions of
acetylcholine and nitric oxide to forearm blood flow at exercise onset
and recovery. Am. J. Physiol.: Heart Circ. Physiol. 273:
H000-H000, 1997. PDF
- Pavy-Le Traon, A.,
D. Siguado, P. Vasseur, A. Maillet, J.O. Fortrat, R.L Hughson, G.
Gauquelin-Koch and C. Gharib. Cardiovascular responses to orthostatic
tests after a 42-day head-down bed-rest. Eur. J. Appl. Physiol.
In press, 1997.
- Gratadour,P., P.
Sagnard, H. Counioux, B. Bagou, G. Annat, R.L. Hughson, J.-P. Viale
and L. Quintin. Sympathovagal effects of spinal anaesthesia assessed
by the spontaneous cardiac baroreflex. Anaesthesiology 87:
1359-1367, 1997.
- Pavy-Le Traon,A., D.
Siguaudo, P. Vasseur, J.O. Fortat, A. Güell, R.L. Hughson and C.
Gharib. Orthostatic tests after a 4-day confinement or simulated
weightlessness. Clin. Physiol. 17: 41-55, 1997.
- Shoemaker, J.K.,
S.M. Phillips, H.J. Green and R.L. Hughson. Faster femoral artery
blood velocity kinetics at the onset of exercise following short-term
training. Cardiovasc. Res. 31: 278-286, 1996.
- Blaber, A.P., and
R.L. Hughson. Cardiorespiratory interactions during fixed pace
resistive breathing. J. Appl. Physiol. 80:1618-1626, 1996.
- Sigaudo, D., J.O.
Fortrat, A. Maillet, A. Allevard, A. Pavy-Le Traon, R.L. Hughson, A.
Güell, C. Gharib and G. Gauquelin. Comparison of a 4-day confinement
and head-down tilt on endocrine response and cardiovascular
variability in humans. Eur. J. Appl. Physiol. 73: 28-37,
1996.
- Hughson, R.L., J.K.
Shoemaker, M.E. Tschakovsky and J.M. Kowalchuk. Dependence of muscle O2
on blood flow dynamics at the onset of forearm exercise. J. Appl.
Physiol. 81: 1619-1626, 1996.
- Shoemaker, J.K.,
H.L. Naylor, Z.I. Pozeg and R.L. Hughson. Failure of postraglandins to
modulate the time course of blood flow during dynamic forearm exercise
in humans. J. Appl. Physiol. 81: 1516-1521, 1996.
- Shoemaker, J.K.,
Z.I. Pozeg and R.L. Hughson. Forearm blood flow by Doppler ultrasound
during rest and exercise: tests of day-to-day repeatability. Med.
Sci. Sports Exerc. In press 81: 1144-1149, 1996.
- Tschakovsky, M.E.,
J.K. Shoemaker and R.L. Hughson. Vasodilation and muscle pump
contribution to immediate exercise hyperemia. Am. J. Physiol.:
Heart Circ. Physiol. 271: H1697-H1701, 1996.
- Gregoire, J., S.
Tuck, Y. Yamamoto and R.L. Hughson. Heart rate variability at rest and
exercise: Influence of age, gender, and physical training. Can. J.
Appl. Physiol. 21: 455-470, 1996.
- Blaber, A. P., Y.
Yamamoto, and R. L. Hughson. Change in phase relationship between
systolic BP and RR-interval during lower body negative pressure. Am.
J. Physiol. Heart Circ. Physiol. 268: H1688-H1693, 1995.
- Blaber, A. P., Y.
Yamamoto, and R. L. Hughson. Methodology of spontaneous baroreflex
relationship assessed by surrogate data analysis. Am. J. Physiol.
Heart Circ. Physiol. 268: H1682-H16871995.
- Hughson, R. L., A.
Maillet, G. Dureau, Y. Yamamoto, and C. Gharib. Harmonic and fractal
blood pressure variability in heart transplant patients. Hypertension
25: 643-650, 1995.
- Hughson, R. L., A.
Maillet, G. Gauquelin, P. Arbeille, Y. Yamamoto, and C. Gharib.
Investigation of hormonal effects during 10 hour head down tilt on
heart rate and blood pressure variability. J. Appl. Physiol. 78:
583-596, 1995.
- Hughson, R. L.
Coupling of ventilation and gas exchange during transitions in work
rate by humans. Resp. Physiol. 101: 87-98, 1995.
- Hughson, R. L. and
J. M. Kowalchuk. Kinetics of oxygen uptake for submaximal exercise in
hyperoxia, normoxia, and hypoxia. Can. J. Appl. Physiol. 20: 198-210,
1995.
- Hughson, R. L.
Coupling of ventilation and gas exchange during transitions in work
rate by humans. Respir. Physiol. 101: 87-98, 1995.
- Hughson, R. L., H.
J. Green, and M. T. Sharratt. Gas exchange, blood lactate, and plasma
catecholamines during incremental exercise in hypoxia and normoxia. J.
Appl. Physiol. 79: 1134-1141, 1995.
- Parlow, J., J.-P.
Viale, G. Annat, R. Hughson, and L. Quintin. Spontaneous cardiac
baroreflex in humans: Comparison with drug-induced responses.
Hypertension 25: 1058-1068, 1995.
- Phillips, S. M., H.
J. Green, M. J. MacDonald, and R. L. Hughson. Progressive effect of
endurance training on VO2 kinetics at the onset of submaximal
exercise. J. Appl. Physiol. 79: 1914-1920, 1995.
- Tschakovsky, M. E.,
J. K. Shoemaker, and R. L. Hughson. Beat-by-beat forearm blood flow
with Doppler ultrasound and strain-gauge plethysmography. J. Appl.
Physiol. 79: 713-719, 1995.
- Yamamoto, Y., J. O.
Fortrat, and R. L. Hughson. On the fractal nature of heart rate
variability in humans: effects of respiratory sinus arrhythmia. Am. J.
Physiol. Heart Circ. Physiol. 269: H480-H486, 1995.
- Yamamoto, Y., Y.
Nakamura, H. Sato, M. Yamamoto, K. Kato, and R. L. Hughson. On the
fractal nature of heart rate variability in humans: Effects of vagal
blockade. Am. J. Physiol. Regul. Integr. Comp. Physiol. 269:
R830-R837, 1995.
- Butler, G. C., Y.
Yamamoto, and R. L. Hughson. Heart rate variability to monitor
autonomic nervous system activity during orthostatic stress. J. Clin.
Pharmacol. 34: 558-562, 1994.
- Butler, G. C., Y.
Yamamoto, and R. L. Hughson. Fractal nature of short-term systolic BP
and HR variability during lower body negative pressure. Am. J.
Physiol. Regul. Integr. Comp. Physiol. 267: R26-R33, 1994.
- Hughson, R. L., Y.
Yamamoto, R. E. McCullough, J. R. Sutton, and J. T. Reeves.
Sympathetic and parasympathetic indicators of heart rate control at
altitude studied by spectral analysis. J. Appl. Physiol. 77:
2537-2542, 1994.
- Hughson, R. L., Y.
Yamamoto, A. Maillet, J. O. Fortrat, A. Pavy-Le Traon, G. C. Butler,
A. Güell, and C. Gharib. Altered autonomic regulation of cardiac
function during head-up tilt after 28-day head-down bed-rest with
counter-measures. Clin. Physiol. 14: 291-304, 1994.
- Hughson, R. L., A.
Maillet, C. Gharib, J. O. Fortrat, Y. Yamamoto, A. Pavy-Le Traon, D.
Riviere, and A. Güell. Reduced spontaneous baroreflex response slope
during lower body negative pressure after 28 day head down bedrest. J.
Appl. Physiol. 77: 69-77, 1994.
- Hughson, R. L., Y.
Yamamoto, A. P. Blaber, A. Maillet, J. O. Fortrat, A. Pavy-Le Traon,
A. Guell, and C. Gharib. Effect of 28-day head-down bed rest with
countermeasures on heart rate variability during LBNP. Aviat. Space
Environ. Med. 65: 293-300, 1994.
- Iellamo, F., R. L.
Hughson, F. Castrucci, J. M. Legramante, G. Raimondi, and G.
Tallarida. Evaluation of spontaneous baroreflex modulation of sinus
node during isometric exercise in healthy humans. Am. J. Physiol.
Heart Circ. Physiol. 267: H994-H1001, 1994.
- Maillet, A., J. O.
Fortrat, D. Sigaudo, A. Pavy-Le-Traon, R. L. Hughson, C. Gharib, and
G. Gauquelin. Variabilité de l'intervalle R-R et baroréflexe spontané
avant et après un séjour en apensateur. Presse Med. 23: 10431994.
- Maillet, A., A.
Pavy-Le Traon, A. M. Allevard, D. Siguardo, R. L. Hughson, C. Gharib,
and G. Gauquelin. Hormone changes induced by 37.5-h head-down tilt
(-6°) in humans. Eur. J. Appl. Physiol. 68: 497-503, 1994.
- Shoemaker, J. K., L.
Hodge, and R. L. Hughson. Cardiorespiratory kinetics and femoral
artery blood velocity during dynamic knee extension exercise. J. Appl.
Physiol. 77: 2625-2632, 1994.
- Yamamoto, Y. and R.
L. Hughson. On the fractal nature of heart rate variability in humans:
effects of data length and b-adrenergic blockade. Am. J. Physiol.
Regul. Integr. Comp. Physiol. 266: R40-R49, 1994.
- Butler, G. C., Y.
Yamamoto, and R. L. Hughson. Heart rate variability and fractal
dimension during orthostatic challenges. J. Appl. Physiol. 75:
2602-2612, 1993.
- Hughson, R. L., Y.
Yamamoto, G. C. Butler, A. Guell, and C. Gharib. Evaluation of
spontaneous baroreflex response during head up tilt after 28 days of
head down tilt bed rest. Acta Astronautica 29: 601-605, 1993.
- Hughson, R. L., J.
E. Cochrane, and G. C. Butler. Faster O2 uptake kinetics at onset of
supine exercise with than without lower body negative pressure. J.
Appl. Physiol. 75: 1962-1967, 1993.
- Hughson, R. L., L.
Quintin, G. Annat, Y. Yamamoto, and C. Gharib. Spontaneous baroreflex
by sequence and power spectral methods in humans. Clin. Physiol. 13:
663-676, 1993.
- Yamamoto, Y., R. L.
Hughson, J. R. Sutton, C. S. Houston, A. Cymerman, E. L. Fallen, and
M. V. Kamath. Operation Everest II: An indication of deterministic
chaos in human heart rate variability at extreme simulated altitude.
Biol. Cybern. 69: 205-212, 1993.
- Yamamoto, Y. and R.
L. Hughson. Extracting fractal components from time series. Physica D
68: 250-264, 1993.
- Butler, G. C., Y.
Yamamoto, H. C. Xing, D. R. Northey, and R. L. Hughson. Probing heart
rate and blood pressure control mechanisms during graded levels of
lower body negative pressure (LBNP). Microgravity Q. 2: 133-140, 1992.
- Cochrane, J. E. and
R. L. Hughson. Computer simulation of O2 transport and utilization
mechanisms at the onset of exercise. J. Appl. Physiol. 73: 2382-2388,
1992.
- Yamamoto, Y., R. L.
Hughson, and Y. Nakamura. Autonomic nervous system responses to
exercise in relation to ventilatory threshold. Chest 101 Suppl.
206S-210S, 1992.
- Butler, G. C., H. C.
Xing, D. R. Northey, and R. L. Hughson. Reduced orthostatic tolerance
following 4 h head-down tilt. Eur. J. Appl. Physiol. 62: 26-30, 1991.
- Hughson, R. L., D.
R. Northey, H. C. Xing, B. H. Dietrich, and J. E. Cochrane. Alignment
of ventilation and gas fraction for breath-by-breath respiratory gas
exchange calculations in exercise. Comput. Biomed. Res. 24: 118-128,
1991.
- Hughson, R. L. and
J. M. Kowalchuk. b-blockade and oxygen delivery to muscle during
exercise. Can. J. Physiol. Pharmacol. 69: 285-289, 1991.
- Hughson, R. L., L.
A. Cuervo, A. E. Patla, D. A. Winter, H. C. Xing, B. H. Dietrich, and
G. D. Swanson. Time domain analysis of oxygen uptake during
pseudorandom binary sequence exercise tests. J. Appl. Physiol. 71:
1991.
- Hughson, R. L., H.
C. Xing, C. Borkhoff, and G. C. Butler. Kinetics of ventilation and
gas exchange during supine and upright cycle exercise. Eur. J. Appl.
Physiol. 63: 300-307, 1991.
- Xing, H. C., J. E.
Cochrane, Y. Yamamoto, and R. L. Hughson. Frequency domain analysis of
ventilation and gas exchange kinetics in hypoxic exercise. J. Appl.
Physiol. 71: 2394-2401, 1991.
- Yamamoto, Y., R. L.
Hughson, and J. C. Peterson. Autonomic control of heart rate during
exercise studied by heart rate variability spectral analysis. J. Appl.
Physiol. 71: 1136-1142, 1991.
- Yamamoto, Y., M.
Miyashita, R. L. Hughson, S. Tamura, M. Shinohara, and Y. Mutoh. The
ventilatory threshold gives maximal lactate steady state. Eur. J.
Appl. Physiol. 63: 55-59, 1991.
- Yamamoto, Y. and R.
L. Hughson. Coarse graining spectral analysis: a new method for studying
heart rate variability. J. Appl. Physiol. 71: 1143-1150, 1991.
Send comments and mail to Dave
Northey
Cardiorespiratory & Vascular Dynamics Laboratory
Dept. of Kinesiology
University of Waterloo
Waterloo, ON N2L 3G1
CANADA
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Last updated by Richard Hughson on 10/25/2002
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