Publications by authors named "Louvaris Z"

57 Publications

Physical activity is increased by a 12-week semiautomated telecoaching programme in patients with COPD: a multicentre randomised controlled trial.

Thorax 2017 May 30;72(5):415-423. Epub 2017 Jan 30.

KU Leuven, Department of Rehabilitation Sciences, Leuven, Belgium.

Rationale: Reduced physical activity (PA) in patients with COPD is associated with a poor prognosis. Increasing PA is a key therapeutic target, but thus far few strategies have been found effective in this patient group.

Objectives: To investigate the effectiveness of a 12-week semiautomated telecoaching intervention on PA in patients with COPD in a multicentre European randomised controlled trial.

Methods: 343 patients from six centres, encompassing a wide spectrum of disease severity, were randomly allocated to either a usual care group (UCG) or a telecoaching intervention group (IG) between June and December 2014. This 12-week intervention included an exercise booklet and a step counter providing feedback both directly and via a dedicated smartphone application. The latter provided an individualised daily activity goal (steps) revised weekly and text messages as well as allowing occasional telephone contacts with investigators. PA was measured using accelerometry during 1 week preceding randomisation and during week 12. Secondary outcomes included exercise capacity and health status. Analyses were based on modified intention to treat.

Main Results: Both groups were comparable at baseline in terms of factors influencing PA. At 12 weeks, the intervention yielded a between-group difference of mean, 95% CI (lower limit - upper limit; ll-ul) +1469, 95% CI (971 to 1965) steps/day and +10.4, 95% CI (6.1 to 14.7) min/day moderate PA; favouring the IG (all p≤0.001). The change in 6-min walk distance was significantly different (13.4, 95% CI (3.40 to 23.5) m, p<0.01), favouring the IG. In IG patients, an improvement could be observed in the functional state domain of the clinical COPD questionnaire (p=0.03) compared with UCG. Other health status outcomes did not differ.

Conclusions: The amount and intensity of PA can be significantly increased in patients with COPD using a 12-week semiautomated telecoaching intervention including a step counter and an application installed on a smartphone.

Trial Registration Number: NCT02158065.
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http://dx.doi.org/10.1136/thoraxjnl-2016-209026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5520265PMC
May 2017

Heterogeneity of blood flow and metabolism during exercise in patients with chronic obstructive pulmonary disease.

Respir Physiol Neurobiol 2017 03 3;237:42-50. Epub 2017 Jan 3.

Faculty of Physical Education and Sport Sciences, National and Kapodistrian University of Athens, Greece; 1st Department of Critical Care Medicine and Pulmonary Services, Evangelismos Hospital, "M. Simou, and G.P. Livanos Laboratories", National and Kapodistrian University of Athens, Greece; Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University Newcastle, UK.

The study investigated whether the capacity to regulate muscle blood flow (Q) relative to metabolic demand (VO) is impaired in COPD. Using six NIRS optodes over the upper, middle and lower vastus lateralis in 6 patients, (FEV:46±12%predicted) we recorded from each: a) Q by indocyanine green dye injection, b) VO/Q ratios based on fractional tissue O saturation and c) VO as their product, during constant-load exercise (at 20%, 50% and 80% of peak capacity) in normoxia and hyperoxia (FO:1.0). At 50 and 80%, relative dispersion (RD) for Q, but not for VO, was greater in normoxia (0.67±0.07 and 0.79±0.08, respectively) compared to hyperoxia (0.57±0.12 and 0.72±0.07, respectively). In both conditions, RD for VO and Q significantly increased throughout exercise; however, RD of VO/Q ratio was minimal (normoxia: 0.12-0.08 vs hyperoxia: 0.13-0.09). Muscle Q and VO appear closely matched in COPD patients, indicating a minimal impact of heterogeneity on muscle oxygen availability at submaximal levels of exercise.
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http://dx.doi.org/10.1016/j.resp.2016.12.013DOI Listing
March 2017

Interval training induces clinically meaningful effects in daily activity levels in COPD.

Eur Respir J 2016 08 23;48(2):567-70. Epub 2016 Jun 23.

Faculty of Physical Education and Sports Sciences, National and Kapodistrian University of Athens, Athens, Greece 1st Dept of Respiratory Medicine, Pulmonary Rehabilitation Unit, National and Kapodistrian University of Athens, Sotiria Hospital, Athens, Greece

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http://dx.doi.org/10.1183/13993003.00679-2016DOI Listing
August 2016

Physical Activity Characteristics across GOLD Quadrants Depend on the Questionnaire Used.

PLoS One 2016 14;11(3):e0151255. Epub 2016 Mar 14.

NIHR Respiratory Biomedical Research Unit of the Royal Brompton and Harefield NHS foundation Trust and Imperial College London, London, United Kingdom.

Background: The GOLD multidimensional classification of COPD severity combines the exacerbation risk with the symptom experience, for which 3 different questionnaires are permitted. This study investigated differences in physical activity (PA) in the different GOLD quadrants and patient's distribution in relation to the questionnaire used.

Methods: 136 COPD patients (58±21% FEV1 predicted, 34F/102M) completed COPD assessment test (CAT), clinical COPD questionnaire (CCQ) and modified Medical Research Council (mMRC) questionnaire. Exacerbation history, spirometry and 6MWD were collected. PA was objectively measured for 2 periods of 1 week, 6 months apart, in 5 European centres; to minimise seasonal and clinical variation the average of these two periods was used for analysis.

Results: GOLD quadrants C+D had reduced PA compared with A+B (3824 [2976] vs. 5508 [4671] steps.d-1, p<0.0001). The choice of questionnaire yielded different patient distributions (agreement mMRC-CAT κ = 0.57; CCQ-mMRC κ = 0.71; CCQ-CAT κ = 0.72) with different clinical characteristics. PA was notably lower in patients with an mMRC score ≥2 (3430 [2537] vs. 5443 [3776] steps.d-1, p <0.001) in both the low and high risk quadrants.

Conclusions: Using different questionnaires changes the patient distribution and results in different clinical characteristics. Therefore, standardization of the questionnaire used for classification is critical to allow comparison of different studies using this as an entry criterion.

Clinical Trial Registration: ClinicalTrials.gov NCT01388218.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0151255PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4790973PMC
August 2016

Can health status questionnaires be used as a measure of physical activity in COPD patients?

Eur Respir J 2016 05 25;47(5):1565-8. Epub 2016 Feb 25.

KU Leuven-University of Leuven, Department of Rehabilitation Sciences, Leuven, Belgium University Hospitals Leuven, Department of Respiratory Diseases, Leuven, Belgium

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http://dx.doi.org/10.1183/13993003.01815-2015DOI Listing
May 2016

Physiological basis of cardiopulmonary rehabilitation in patients with lung or heart disease.

Breathe (Sheff) 2015 Jun;11(2):120-7

Faculty of Physical Education and Sports Sciences, National and Kapodistrian University of Athens, Athens, Greece ; 1st Dept of Respiratory Medicine, Pulmonary Rehabilitation Unit, National and Kapodistrian University of Athens, Sotiria Hospital, Athens, Greece ; 1st Dept of Critical Care Medicine, Pulmonary Rehabilitation Center, National and Kapodistrian University of Athens, Evangelismos Hospital, Athens, Greece.

Educational Aims: To illustrate the common mechanisms limiting exercise tolerance in patients with chronic lung and heart diseaseTo highlight the impact of lung and heart disease on daily physical activity levelsTo outline the effects of cardiopulmonary rehabilitation on functional capacity in patients with chronic lung and heart diseaseTo discuss an innovative tele-rehabilitation intervention using information and communications technologies to improve functional capacity in patients with chronic lung and heart disease.

Summary: Shortness of breath associated with cardiorespiratory abnormalities and peripheral muscle discomfort are the major factors that limit exercise capacity in patients with chronic obstructive pulmonary disease (COPD) and those with congestive heart failure (CHF). Both of these symptoms negatively impact on patients' daily physical activity levels. In turn, poor daily physical activity is commonly associated with increased rates of morbidity and mortality. Cardiopulmonary rehabilitation programmes partially reverse muscle weakness and dysfunction and increase functional capacity in both COPD and CHF. However, benefits gained from participation in cardiopulmonary rehabilitation programmes are regressing soon after the completion of these programmes. Moreover, several barriers limit access and uptake of cardiopulmonary rehabilitation programmes by eligible patients. A potential solution to the underutilisation of cardiopulmonary rehabilitation is the implementation of tele-rehabilitation interventions at home using information and communications technologies. Thus, tele-rehabilitation may be useful to encourage and educate patients with COPD or CHF on how best to maintain and/or further enhance daily physical activity levels.
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http://dx.doi.org/10.1183/20734735.021114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4487369PMC
June 2015

Hemodynamic effects of high intensity interval training in COPD patients exhibiting exercise-induced dynamic hyperinflation.

Respir Physiol Neurobiol 2015 Oct 23;217:8-16. Epub 2015 Jun 23.

National and Kapodistrian University of Athens, Department of Physical Education and Sports Sciences, Athens, Greece; National and Kapodistrian University of Athens, 1st Department of Respiratory Medicine, Pulmonary Rehabilitation Unit, Sotiria Hospital, Athens, Greece; National and Kapodistrian University of Athens, 1st Department of Critical Care Medicine, Evangelismos Hospital, Greece. Electronic address:

Dynamic hyperinflation (DH) has a significant adverse effect on cardiovascular function during exercise in COPD patients. COPD patients with (n = 25) and without (n = 11) exercise-induced DH undertook an incremental (IET) and a constant-load exercise test (CLET) sustained at 75% peak work (WRpeak) prior to and following an interval cycling exercise training regime (set at 100% WRpeak with 30-s work/30-s rest intervals) lasting for 12 weeks. Cardiac output (Q) was assessed by cardio-bio-impedance (PhysioFlow, enduro, PF-O7) to determine Q mean response time (QMRT) at onset (QMRT(ON)) and offset (QMRT(OFF)) of CLET. Post-rehabilitation only those patients exhibiting exercise-induced DH demonstrated significant reductions in QMRT(ON) (from 82.2 ± 4.3 to 61.7 ± 4.2 s) and QMRT(OFF) (from 80.5 ± 3.8 to 57.2 ± 4.9 s ). These post-rehabilitation adaptations were associated with improvements in inspiratory capacity, thereby suggesting that mitigation of the degree of exercise-induced DH improves central hemodynamic responses in COPD patients.
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http://dx.doi.org/10.1016/j.resp.2015.06.006DOI Listing
October 2015

The PROactive instruments to measure physical activity in patients with chronic obstructive pulmonary disease.

Eur Respir J 2015 Oct 28;46(4):988-1000. Epub 2015 May 28.

Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain Centro de Investigación Biomédica en Red de Epidemiología y Salud Pública (CIBERESP), Barcelona, Spain Universitat Pompeu Fabra (UPF), Barcelona, Spain

No current patient-centred instrument captures all dimensions of physical activity in chronic obstructive pulmonary disease (COPD). Our objective was item reduction and initial validation of two instruments to measure physical activity in COPD.Physical activity was assessed in a 6-week, randomised, two-way cross-over, multicentre study using PROactive draft questionnaires (daily and clinical visit versions) and two activity monitors. Item reduction followed an iterative process including classical and Rasch model analyses, and input from patients and clinical experts.236 COPD patients from five European centres were included. Results indicated the concept of physical activity in COPD had two domains, labelled "amount" and "difficulty". After item reduction, the daily PROactive instrument comprised nine items and the clinical visit contained 14. Both demonstrated good model fit (person separation index >0.7). Confirmatory factor analysis supported the bidimensional structure. Both instruments had good internal consistency (Cronbach's α>0.8), test-retest reliability (intraclass correlation coefficient ≥0.9) and exhibited moderate-to-high correlations (r>0.6) with related constructs and very low correlations (r<0.3) with unrelated constructs, providing evidence for construct validity.Daily and clinical visit "PROactive physical activity in COPD" instruments are hybrid tools combining a short patient-reported outcome questionnaire and two activity monitor variables which provide simple, valid and reliable measures of physical activity in COPD patients.
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http://dx.doi.org/10.1183/09031936.00183014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4589432PMC
October 2015

Reply to Engel and Vemulpad.

J Appl Physiol (1985) 2015 Apr;118(8):1087

National and Kapodistrian University of Athens, Department of Physical Education and Sports Sciences, Athens, Greece; National and Kapodistrian University of Athens, 1st Department of Critical Care Medicine, Evangelismos Hospital, Athens, Greece;

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http://dx.doi.org/10.1152/japplphysiol.00132.2015DOI Listing
April 2015

A method for assessing heterogeneity of blood flow and metabolism in exercising normal human muscle by near-infrared spectroscopy.

J Appl Physiol (1985) 2015 Mar 15;118(6):783-93. Epub 2015 Jan 15.

Department of Medicine, University of California San Diego, La Jolla, California; Institute of Clinical Exercise & Health Sciences, University of the West of Scotland, Hamilton, United Kingdom.

Heterogeneity in the distribution of both blood flow (Q̇) and O2 consumption (V̇O2) has not been assessed by near-infrared spectroscopy in exercising normal human muscle. We used near-infrared spectroscopy to measure the regional distribution of Q̇ and V̇O2 in six trained cyclists at rest and during constant-load exercise (unloaded pedaling, 20%, 50%, and 80% of peak Watts) in both normoxia and hypoxia (inspired O2 fraction = 0.12). Over six optodes over the upper, middle, and lower vastus lateralis, we recorded 1) indocyanine green dye inflow after intravenous injection to measure Q̇; and 2) fractional tissue O2 saturation (StiO2) to estimate local V̇O2-to-Q̇ ratios (V̇o2/Q̇). Varying both exercise intensity and inspired O2 fraction provided a (directly measured) femoral venous O2 saturation range from about 10 to 70%, and a correspondingly wide range in StiO2. Mean Q̇-weighted StiO2 over the six optodes related linearly to femoral venous O2 saturation in each subject. We used this relationship to compute local muscle venous blood O2 saturation from StiO2 recorded at each optode, from which local V̇O2/Q̇ could be calculated by the Fick principle. Multiplying regional V̇O2/Q̇ by Q̇ yielded the corresponding local V̇O2. While six optodes along only in one muscle may not fully capture the extent of heterogeneity, relative dispersion of both Q̇ and V̇O2 was ∼0.4 under all conditions, while that for V̇O2/Q̇ was minimal (only ∼0.1), indicating in fit young subjects 1) a strong capacity to regulate Q̇ according to regional metabolic need; and 2) a likely minimal impact of heterogeneity on muscle O2 availability.
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http://dx.doi.org/10.1152/japplphysiol.00458.2014DOI Listing
March 2015

Limitation in tidal volume expansion partially determines the intensity of physical activity in COPD.

J Appl Physiol (1985) 2015 Jan 13;118(1):107-14. Epub 2014 Nov 13.

National and Kapodistrian University of Athens, Department of Physical Education and Sports Sciences, Athens, Greece; National and Kapodistrian University of Athens, 1st Department of Critical Care Medicine, Evangelismos Hospital, Athens, Greece;

In patients with chronic obstructive pulmonary disease (COPD), reduced levels of daily physical activity are associated with the degree of impairment in lung, peripheral muscle, and central hemodynamic function. There is, however, limited evidence as to whether limitations in tidal volume expansion also, importantly, determine daily physical activity levels in COPD. Eighteen consecutive patients with COPD [9 active (forced expiratory volume in 1 s, FEV1: 1.59 ± 0.64 l) with an average daily movement intensity >1.88 m/s(2) and 9 less active patients (FEV1: 1.16 ± 0.41 l) with an average intensity <1.88 m/s(2)] underwent a 4-min treadmill test at a constant speed corresponding to each individual patient's average movement intensity, captured by a triaxial accelerometer during a preceding 7-day period. When chest wall volumes, captured by optoelectronic plethysmography, were expressed relative to comparable levels of minute ventilation (ranging between 14.5 ± 4.3 to 33.5 ± 4.4 l/min), active patients differed from the less active ones in terms of the lower increase in end-expiratory chest wall volume (by 0.15 ± 0.17 vs. 0.45 ± 0.21 l), the greater expansion in tidal volume (by 1.76 ± 0.58 vs. 1.36 ± 0.24 l), and the larger inspiratory reserve chest wall volume (IRVcw: by 0.81 ± 0.25 vs. 0.39 ± 0.27 l). IRVcw (r(2) = 0.420), expiratory flow (r(2) change = 0.174), and Borg dyspnea score (r(2) change = 0.123) emerged as the best contributors, accounting for 71.7% of the explained variance in daily movement intensity. Patients with COPD exhibiting greater ability to expand tidal volume and to maintain adequate inspiratory reserve volume tend to be more physically active. Thus interventions aiming at mitigating restrictions on operational chest wall volumes are expected to enhance daily physical activity levels in COPD.
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http://dx.doi.org/10.1152/japplphysiol.00301.2014DOI Listing
January 2015

Blood flow does not redistribute from respiratory to leg muscles during exercise breathing heliox or oxygen in COPD.

J Appl Physiol (1985) 2014 Aug 5;117(3):267-76. Epub 2014 Jun 5.

First Department of Critical Care Medicine and Pulmonary Services, GP Livanos and M Simou Laboratories, Medical School of Athens University, Evangelismos Hospital, Athens, Greece;

In patients with chronic obstructive pulmonary disease (COPD), one of the proposed mechanisms for improving exercise tolerance, when work of breathing is experimentally reduced, is redistribution of blood flow from the respiratory to locomotor muscles. Accordingly, we investigated whether exercise capacity is improved on the basis of blood flow redistribution during exercise while subjects are breathing heliox (designed to primarily reduce the mechanical work of breathing) and during exercise with oxygen supplementation (designed to primarily enhance systemic oxygen delivery but also to reduce mechanical work of breathing). Intercostal, abdominal, and vastus lateralis muscle perfusion were simultaneously measured in 10 patients with COPD (forced expiratory volume in 1 s: 46 ± 12% predicted) by near-infrared spectroscopy using indocyanine green dye. Measurements were performed during constant-load exercise at 75% of peak capacity to exhaustion while subjects breathed room air and, then at the same workload, breathed either normoxic heliox (helium 79% and oxygen 21%) or 100% oxygen, the latter two in balanced order. Times to exhaustion while breathing heliox and oxygen did not differ (659 ± 42 s with heliox and 696 ± 48 s with 100% O2), but both exceeded that on room air (406 ± 36 s, P < 0.001). At exhaustion, intercostal and abdominal muscle blood flow during heliox (9.5 ± 0.6 and 8.0 ± 0.7 ml · min(-1)·100 g(-1), respectively) was greater compared with room air (6.8 ± 0.5 and 6.0 ± 0.5 ml·min(-1)·100 g·, respectively; P < 0.05), whereas neither intercostal nor abdominal muscle blood flow differed between oxygen and air breathing. Quadriceps muscle blood flow was also greater with heliox compared with room air (30.2 ± 4.1 vs. 25.4 ± 2.9 ml·min(-1)·100 g(-1); P < 0.01) but did not differ between air and oxygen breathing. Although our findings confirm that reducing the burden on respiration by heliox or oxygen breathing prolongs time to exhaustion (at 75% of maximal capacity) in patients with COPD, they do not support the hypothesis that redistribution of blood flow from the respiratory to locomotor muscles is the explanation.
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http://dx.doi.org/10.1152/japplphysiol.00490.2014DOI Listing
August 2014

Activity monitoring reflects cardiovascular and metabolic variations in COPD patients across GOLD stages II to IV.

Respir Physiol Neurobiol 2013 Dec 3;189(3):513-20. Epub 2013 Sep 3.

National and Kapodistrian University of Athens, Department of Physical Education and Sports Sciences, Athens, Greece; National and Kapodistrian University of Athens, 1st Department of Respiratory Medicine, Pulmonary Rehabilitation Unit, Sotiria Hospital, Athens, Greece; Technological Educational Institute of Lamia, Physiotherapy Department, Lamia, Greece.

We investigated whether activity monitoring reliably reflects variations in oxygen transport and utilization during walking in COPD patients. Forty-two patients (14 in each GOLD stage II, III and IV) performed an incremental treadmill protocol to the limit of tolerance. Breath-by-breath gas exchange, central hemodynamic variables and activity monitoring were simultaneously recorded. Physiological variables and accelerometer outputs rose linearly with walking speeds. Strong correlations (r[interquartile range, IQR]) were found between treadmill walking intensity (WI: range 0.8-2.0 ms(-2)) and oxygen consumption (0.95 [IQR 0.87-0.97]), (range 7.6-15.5 ml kg(-1)min(-1)); minute ventilation (0.95 [IQR 0.86-0.98]), (range 20-37 l min(-1)); cardiac output (0.89 [IQR 0.73-0.94]), (range 6.8-11.5 l min(-1)) and arteriovenous oxygen concentration difference (0.84 [IQR 0.76-0.90]), (range 7.7-12.1 ml O2100 ml(-1)). Correlations between WI and gas exchange or central hemodynamic parameters were not different across GOLD stages. In conclusion, central hemodynamic, respiratory and muscle metabolic variations during incremental treadmill exercise are tightly associated to changes in walking intensity as recorded by accelerometry across GOLD stages II to IV. Interestingly, the magnitude of these associations is not different across GOLD stages.
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http://dx.doi.org/10.1016/j.resp.2013.08.014DOI Listing
December 2013

Intensity of daily physical activity is associated with central hemodynamic and leg muscle oxygen availability in COPD.

J Appl Physiol (1985) 2013 Sep 11;115(6):794-802. Epub 2013 Jul 11.

First Department of Critical Care Medicine and Pulmonary Services, GP Livanos and M Simou Laboratories, Medical School of Athens University, Evangelismos Hospital, Athens, Greece;

In chronic obstructive pulmonary disease (COPD), daily physical activity is reported to be adversely associated with the magnitude of exercise-induced dynamic hyperinflation and peripheral muscle weakness. There is limited evidence whether central hemodynamic, oxygen transport, and peripheral muscle oxygenation capacities also contribute to reduced daily physical activity. Nineteen patients with COPD (FEV1, 48 ± 14% predicted) underwent a treadmill walking test at a speed corresponding to the individual patient's mean walking intensity, captured by a triaxial accelerometer during a preceding 7-day period. During the indoor treadmill test, the individual patient mean walking intensity (range, 1.5 to 2.3 m/s2) was significantly correlated with changes from baseline in cardiac output recorded by impedance cardiography (range, 1.2 to 4.2 L/min; r = 0.73), systemic vascular conductance (range, 7.9 to 33.7 ml·min(-1)·mmHg(-1); r = 0.77), systemic oxygen delivery estimated from cardiac output and arterial pulse-oxymetry saturation (range, 0.15 to 0.99 L/min; r = 0.70), arterio-venous oxygen content difference calculated from oxygen uptake and cardiac output (range, 3.7 to 11.8 mlO2/100 ml; r = -0.73), and quadriceps muscle fractional oxygen saturation assessed by near-infrared spectrometry (range, -6 to 23%; r = 0.77). In addition, mean walking intensity significantly correlated with the quadriceps muscle force adjusted for body weight (range, 0.28 to 0.60; r = 0.74) and the ratio of minute ventilation over maximal voluntary ventilation (range, 38 to 89%, r = -0.58). In COPD, in addition to ventilatory limitations and peripheral muscle weakness, intensity of daily physical activity is associated with both central hemodynamic and peripheral muscle oxygenation capacities regulating the adequacy of matching peripheral muscle oxygen availability by systemic oxygen transport.
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http://dx.doi.org/10.1152/japplphysiol.00379.2013DOI Listing
September 2013

Validity of physical activity monitors during daily life in patients with COPD.

Eur Respir J 2013 Nov 8;42(5):1205-15. Epub 2013 Feb 8.

Centre for Inflammation Research, The Queen's Medical Research Institute, University of Edinburgh, Edinburgh.

Symptoms during physical activity and physical inactivity are hallmarks of chronic obstructive pulmonary disease (COPD). Our aim was to evaluate the validity and usability of six activity monitors in patients with COPD against the doubly labelled water (DLW) indirect calorimetry method. 80 COPD patients (mean ± sd age 68 ± 6 years and forced expiratory volume in 1 s 57 ± 19% predicted) recruited in four centres each wore simultaneously three or four out of six commercially available monitors validated in chronic conditions for 14 consecutive days. A priori validity criteria were defined. These included the ability to explain total energy expenditure (TEE) variance through multiple regression analysis, using TEE as the dependent variable with total body water (TBW) plus several physical activity monitor outputs as independent variables; and correlation with activity energy expenditure (AEE) measured by DLW. The Actigraph GT3X (Actigraph LLC, Pensacola, FL, USA), and DynaPort MoveMonitor (McRoberts BV, The Hague, the Netherlands) best explained the majority of the TEE variance not explained by TBW (53% and 70%, respectively) and showed the most significant correlations with AEE (r=0.71, p<0.001 and r=0.70, p<0.0001, respectively). The results of this study should guide users in choosing valid activity monitors for research or for clinical use in patients with chronic diseases such as COPD.
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http://dx.doi.org/10.1183/09031936.00134312DOI Listing
November 2013

Heliox increases quadriceps muscle oxygen delivery during exercise in COPD patients with and without dynamic hyperinflation.

J Appl Physiol (1985) 2012 Oct 9;113(7):1012-23. Epub 2012 Aug 9.

Department of Critical Care Medicine and Pulmonary Services, Evangelismos Hospital, M. Simou and G.P. Livanos Laboratories, National and Kapodistrian University of Athens, Athens, Greece.

Some reports suggest that heliox breathing during exercise may improve peripheral muscle oxygen availability in patients with chronic obstructive pulmonary disease (COPD). Besides COPD patients who dynamically hyperinflate during exercise (hyperinflators), there are patients who do not hyperinflate (non-hyperinflators). As heliox breathing may differently affect cardiac output in hyperinflators (by increasing preload and decreasing afterload of both ventricles) and non-hyperinflators (by increasing venous return) during exercise, it was reasoned that heliox administration would improve peripheral muscle oxygen delivery possibly by different mechanisms in those two COPD categories. Chest wall volume and respiratory muscle activity were determined during constant-load exercise at 75% peak capacity to exhaustion, while breathing room air or normoxic heliox in 17 COPD patients: 9 hyperinflators (forced expiratory volume in 1 s = 39 ± 5% predicted), and 8 non-hyperinflators (forced expiratory volume in 1 s = 48 ± 5% predicted). Quadriceps muscle blood flow was measured by near-infrared spectroscopy using indocyanine green dye. Hyperinflators and non-hyperinflators demonstrated comparable improvements in endurance time during heliox (231 ± 23 and 257 ± 28 s, respectively). At exhaustion in room air, expiratory muscle activity (expressed by peak-expiratory gastric pressure) was lower in hyperinflators than in non-hyperinflators. In hyperinflators, heliox reduced end-expiratory chest wall volume and diaphragmatic activity, and increased arterial oxygen content (by 17.8 ± 2.5 ml/l), whereas, in non-hyperinflators, heliox reduced peak-expiratory gastric pressure and increased systemic vascular conductance (by 11.0 ± 2.8 ml·min(-1)·mmHg(-1)). Quadriceps muscle blood flow and oxygen delivery significantly improved during heliox compared with room air by a comparable magnitude (in hyperinflators by 6.1 ± 1.3 ml·min(-1)·100 g(-1) and 1.3 ± 0.3 ml O(2)·min(-1)·100 g(-1), and in non-hyperinflators by 7.2 ± 1.6 ml·min(-1)·100 g(-1) and 1.6 ± 0.3 ml O(2)·min(-1)·100 g(-1), respectively). Despite similar increase in locomotor muscle oxygen delivery with heliox in both groups, the mechanisms of such improvements were different: 1) in hyperinflators, heliox increased arterial oxygen content and quadriceps blood flow at similar cardiac output, whereas 2) in non-hyperinflators, heliox improved central hemodynamics and increased systemic vascular conductance and quadriceps blood flow at similar arterial oxygen content.
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http://dx.doi.org/10.1152/japplphysiol.00481.2012DOI Listing
October 2012

Validity of activity monitors in health and chronic disease: a systematic review.

Int J Behav Nutr Phys Act 2012 Jul 9;9:84. Epub 2012 Jul 9.

Faculty of Kinesiology and Rehabilitation Sciences, Department of Rehabilitation Sciences, Katholieke Universiteit Leuven, Leuven, Belgium.

The assessment of physical activity in healthy populations and in those with chronic diseases is challenging. The aim of this systematic review was to identify whether available activity monitors (AM) have been appropriately validated for use in assessing physical activity in these groups. Following a systematic literature search we found 134 papers meeting the inclusion criteria; 40 conducted in a field setting (validation against doubly labelled water), 86 in a laboratory setting (validation against a metabolic cart, metabolic chamber) and 8 in a field and laboratory setting. Correlation coefficients between AM outcomes and energy expenditure (EE) by the criterion method (doubly labelled water and metabolic cart/chamber) and percentage mean differences between EE estimation from the monitor and EE measurement by the criterion method were extracted. Random-effects meta-analyses were performed to pool the results across studies where possible. Types of devices were compared using meta-regression analyses. Most validation studies had been performed in healthy adults (n=118), with few carried out in patients with chronic diseases (n=16). For total EE, correlation coefficients were statistically significantly lower in uniaxial compared to multisensor devices. For active EE, correlations were slightly but not significantly lower in uniaxial compared to triaxial and multisensor devices. Uniaxial devices tended to underestimate TEE (-12.07 (95%CI; -18.28 to -5.85) %) compared to triaxial (-6.85 (95%CI; -18.20 to 4.49) %, p=0.37) and were statistically significantly less accurate than multisensor devices (-3.64 (95%CI; -8.97 to 1.70) %, p<0.001). TEE was underestimated during slow walking speeds in 69% of the lab validation studies compared to 37%, 30% and 37% of the studies during intermediate, fast walking speed and running, respectively. The high level of heterogeneity in the validation studies is only partly explained by the type of activity monitor and the activity monitor outcome. Triaxial and multisensor devices tend to be more valid monitors. Since activity monitors are less accurate at slow walking speeds and information about validated activity monitors in chronic disease populations is lacking, proper validation studies in these populations are needed prior to their inclusion in clinical trials.
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http://dx.doi.org/10.1186/1479-5868-9-84DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3464146PMC
July 2012

Validity of six activity monitors in chronic obstructive pulmonary disease: a comparison with indirect calorimetry.

PLoS One 2012 20;7(6):e39198. Epub 2012 Jun 20.

Faculty of Kinesiology and Rehabilitation Sciences, Department of Rehabilitation Sciences, Katholieke Universiteit Leuven, and Respiratory Division, UZ Gasthuisberg, Leuven, Belgium.

Reduced physical activity is an important feature of Chronic Obstructive Pulmonary Disease (COPD). Various activity monitors are available but their validity is poorly established. The aim was to evaluate the validity of six monitors in patients with COPD. We hypothesized triaxial monitors to be more valid compared to uniaxial monitors. Thirty-nine patients (age 68±7 years, FEV(1) 54±18%predicted) performed a one-hour standardized activity protocol. Patients wore 6 monitors (Kenz Lifecorder (Kenz), Actiwatch, RT3, Actigraph GT3X (Actigraph), Dynaport MiniMod (MiniMod), and SenseWear Armband (SenseWear)) as well as a portable metabolic system (Oxycon Mobile). Validity was evaluated by correlation analysis between indirect calorimetry (VO(2)) and the monitor outputs: Metabolic Equivalent of Task [METs] (SenseWear, MiniMod), activity counts (Actiwatch), vector magnitude units (Actigraph, RT3) and arbitrary units (Kenz) over the whole protocol and slow versus fast walking. Minute-by-minute correlations were highest for the MiniMod (r = 0.82), Actigraph (r = 0.79), SenseWear (r = 0.73) and RT3 (r = 0.73). Over the whole protocol, the mean correlations were best for the SenseWear (r = 0.76), Kenz (r = 0.52), Actigraph (r = 0.49) and MiniMod (r = 0.45). The MiniMod (r = 0.94) and Actigraph (r = 0.88) performed better in detecting different walking speeds. The Dynaport MiniMod, Actigraph GT3X and SenseWear Armband (all triaxial monitors) are the most valid monitors during standardized physical activities. The Dynaport MiniMod and Actigraph GT3X discriminate best between different walking speeds.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0039198PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3380044PMC
November 2012

Cerebral cortex oxygen delivery and exercise limitation in patients with COPD.

Eur Respir J 2013 Feb 3;41(2):295-301. Epub 2012 May 3.

Evangelismos Hospital, M. Simou and G.P. Livanos Laboratories, Athens, Greece.

In healthy humans, cerebral oxygen desaturation during exercise affects motor unit recruitment, while oxygen supplementation enhances cerebral oxygenation and work capacity. It remains unknown whether in patients with chronic obstructive pulmonary disease (COPD), the well-documented improvement in exercise tolerance with oxygen supplementation may also be partly due to the increase in cerebral oxygenation. Using near infrared spectroscopy, we measured both frontal cerebral cortex blood flow (CBF) using indocyanine green dye and cerebrovascular oxygen saturation (S(t,O(2))) in 12 COPD patients during constant-load exercise to exhaustion at 75% of peak capacity. Subjects exercised while breathing air, 100% oxygen or normoxic heliox, the latter two in balanced order. Time to exhaustion while breathing air was less than for either oxygen or heliox (mean±sem 394±35 versus 670±43 and 637±46 s, respectively). Under each condition, CBF increased from rest to exhaustion. At exhaustion, CBF was higher while breathing air and heliox than oxygen (30.9±2.3 and 31.3±3.5 versus 26.6±3.2 mL·min(-1) per 100 g, respectively), compensating for the lower arterial oxygen content (C(a,O(2))) in air and heliox, and leading to similar cerebral cortex oxygen delivery (CQ(O(2)) for air was 5.3±0.4, for oxygen was 5.5±0.6 and for heliox was 5.6±1.0 mL O(2) per min per 100 g). In contrast, end-exercise S(t,O(2)) was greater while breathing oxygen compared with air or heliox (67±4 versus 57±3 and 53±3%, respectively), reflecting C(a,O(2)) rather than CQ(O(2)). Prolonged time to exhaustion by breathing oxygen and heliox, despite these having a similar CQ(O(2)) to air, a lower S(t,O(2)) with heliox than oxygen, and yet similar endurance time and similar S(t,O(2)) in air and heliox despite greater endurance with heliox, do not support the hypothesis that an improvement in cerebral cortex oxygen availability plays a contributing role in increasing exercise capacity with oxygen or heliox in patients with COPD.
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http://dx.doi.org/10.1183/09031936.00016312DOI Listing
February 2013

On- and off-exercise kinetics of cardiac output in response to cycling and walking in COPD patients with GOLD Stages I-IV.

Respir Physiol Neurobiol 2012 May 29;181(3):351-8. Epub 2012 Mar 29.

Department of Physical Education and Sports Sciences, National and Kapodistrian University of Athens, Greece.

Exercise-induced dynamic hyperinflation and large intrathoracic pressure swings may compromise the normal increase in cardiac output (Q) in Chronic Obstructive Pulmonary Disease (COPD). Therefore, it is anticipated that the greater the disease severity, the greater would be the impairment in cardiac output during exercise. Eighty COPD patients (20 at each GOLD Stage) and 10 healthy age-matched individuals undertook a constant-load test on a cycle-ergometer (75% WR(peak)) and a 6min walking test (6MWT). Cardiac output was measured by bioimpedance (PhysioFlow, Enduro) to determine the mean response time at the onset of exercise (MRTon) and during recovery (MRToff). Whilst cardiac output mean response time was not different between the two exercise protocols, MRT responses during cycling were slower in GOLD Stages III and IV compared to Stages I and II (MRTon: Stage I: 45±2, Stage II: 65±3, Stage III: 90±3, Stage IV: 106±3s; MRToff: Stage I: 42±2, Stage II: 68±3, Stage III: 87±3, Stage IV: 104±3s, respectively). In conclusion, the more advanced the disease severity the more impaired is the hemodynamic response to constant-load exercise and the 6MWT, possibly reflecting greater cardiovascular impairment and/or greater physical deconditioning.
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http://dx.doi.org/10.1016/j.resp.2012.03.014DOI Listing
May 2012

Frontal cerebral cortex blood flow, oxygen delivery and oxygenation during normoxic and hypoxic exercise in athletes.

J Physiol 2011 Aug 4;589(Pt 16):4027-39. Epub 2011 Jul 4.

Department of Critical Care Medicine and Pulmonary Services, Evangelismos Hospital, M. Simou, and G.P. Livanos Laboratories, National and Kapodistrian University of Athens, Greece.

During maximal hypoxic exercise, a reduction in cerebral oxygen delivery may constitute a signal to the central nervous system to terminate exercise. We investigated whether the rate of increase in frontal cerebral cortex oxygen delivery is limited in hypoxic compared to normoxic exercise. We assessed frontal cerebral cortex blood flow using near-infrared spectroscopy and the light-absorbing tracer indocyanine green dye, as well as frontal cortex oxygen saturation (S(tO2)%) in 11 trained cyclists during graded incremental exercise to the limit of tolerance (maximal work rate, WRmax) in normoxia and acute hypoxia (inspired O2 fraction (F(IO2)), 0.12). In normoxia, frontal cortex blood flow and oxygen delivery increased (P < 0.05) from baseline to sub-maximal exercise, reaching peak values at near-maximal exercise (80% WRmax: 287 ± 9 W; 81 ± 23% and 75 ± 22% increase relative to baseline, respectively), both leveling off thereafter up to WRmax (382 ± 10 W). Frontal cortex S(tO2)% did not change from baseline (66 ± 3%) throughout graded exercise. During hypoxic exercise, frontal cortex blood flow increased (P = 0.016) from baseline to sub-maximal exercise, peaking at 80% WRmax (213 ± 6 W; 60 ± 15% relative increase) before declining towards baseline at WRmax (289 ± 5 W). Despite this, frontal cortex oxygen delivery remained unchanged from baseline throughout graded exercise, being at WRmax lower than at comparable loads (287 ± 9 W) in normoxia (by 58 ± 12%; P = 0.01). Frontal cortex S(tO2)% fell from baseline (58 ± 2%) on light and moderate exercise in parallel with arterial oxygen saturation, but then remained unchanged to exhaustion (47 ± 1%). Thus, during maximal, but not light to moderate, exercise frontal cortex oxygen delivery is limited in hypoxia compared to normoxia. This limitation could potentially constitute the signal to limit maximal exercise capacity in hypoxia.
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http://dx.doi.org/10.1113/jphysiol.2011.210880DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3180000PMC
August 2011

Quadriceps muscle blood flow and oxygen availability during repetitive bouts of isometric exercise in simulated sailing.

J Sports Sci 2011 Jul 23;29(10):1041-9. Epub 2011 May 23.

Faculty of Physical Education and Sports Science, National and Kapodistrian University of Athens, Athens, Greece.

In this study, we wished to determine whether the observed reduction in quadriceps muscle oxygen availability, reported during repetitive bouts of isometric exercise in simulated sailing efforts (i.e. hiking), is because of restricted muscle blood flow. Six national-squad Laser sailors initially performed three successive 3-min hiking bouts followed by three successive 3-min cycling tests sustained at constant intensities reproducing the cardiac output recorded during each of the three hiking bouts. The blood flow index (BFI) was determined from assessment of the vastus lateralis using near-infrared spectroscopy in association with the light-absorbing tracer indocyanine green dye, while cardiac output was determined from impedance cardiography. At equivalent cardiac outputs (ranging from 10.3±0.5 to 14.8±0.86 L · min(-1)), the increase from baseline in vastus lateralis BFI across the three hiking bouts (from 1.1±0.2 to 3.1±0.6 nM · s(-1)) was lower (P = 0.036) than that seen during the three cycling bouts (from 1.1±0.2 to 7.2±1.4 nM · s(-1)) (Cohen's d: 3.80 nM · s(-1)), whereas the increase from baseline in deoxygenated haemoglobin (by ∼17.0±2.9 μM) (an index of tissue oxygen extraction) was greater (P = 0.006) during hiking than cycling (by ∼5.3±2.7 μM) (Cohen's d: 4.17 μM). The results suggest that reduced vastus lateralis muscle oxygen availability during hiking arises from restricted muscle blood flow in the isometrically acting quadriceps muscles.
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http://dx.doi.org/10.1080/02640414.2011.574720DOI Listing
July 2011

Effect of helium breathing on intercostal and quadriceps muscle blood flow during exercise in COPD patients.

Am J Physiol Regul Integr Comp Physiol 2011 Jun 16;300(6):R1549-59. Epub 2011 Mar 16.

Department of Critical Care Medicine and Pulmonary Services, Evangelismos Hospital, “M. Simou, and G.P. Livanos Laboratories,” National and Kapodistrian University of Athens, Greece.

Emerging evidence indicates that, besides dyspnea relief, an improvement in locomotor muscle oxygen delivery may also contribute to enhanced exercise tolerance following normoxic heliox (replacement of inspired nitrogen by helium) administration in patients with chronic obstructive pulmonary disease (COPD). Whether blood flow redistribution from intercostal to locomotor muscles contributes to this improvement currently remains unknown. Accordingly, the objective of this study was to investigate whether such redistribution plays a role in improving locomotor muscle oxygen delivery while breathing heliox at near-maximal [75% peak work rate (WR(peak))], maximal (100%WR(peak)), and supramaximal (115%WR(peak)) exercise in COPD. Intercostal and vastus lateralis muscle perfusion was measured in 10 COPD patients (FEV(1) = 50.5 ± 5.5% predicted) by near-infrared spectroscopy using indocyanine green dye. Patients undertook exercise tests at 75 and 100%WR(peak) breathing either air or heliox and at 115%WR(peak) breathing heliox only. Patients did not exhibit exercise-induced hyperinflation. Normoxic heliox reduced respiratory muscle work and relieved dyspnea across all exercise intensities. During near-maximal exercise, quadriceps and intercostal muscle blood flows were greater, while breathing normoxic heliox compared with air (35.8 ± 7.0 vs. 29.0 ± 6.5 and 6.0 ± 1.3 vs. 4.9 ± 1.2 ml·min(-1)·100 g(-1), respectively; P < 0.05; mean ± SE). In addition, compared with air, normoxic heliox administration increased arterial oxygen content, as well as oxygen delivery to quadriceps and intercostal muscles (from 47 ± 9 to 60 ± 12, and from 8 ± 1 to 13 ± 3 mlO(2)·min(-1)·100 g(-1), respectively; P < 0.05). In contrast, normoxic heliox had neither an effect on systemic nor an effect on quadriceps or intercostal muscle blood flow and oxygen delivery during maximal or supramaximal exercise. Since intercostal muscle blood flow did not decrease by normoxic heliox administration, blood flow redistribution from intercostal to locomotor muscles does not represent a likely mechanism of improvement in locomotor muscle oxygen delivery. Our findings might not be applicable to patients who hyperinflate during exercise.
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http://dx.doi.org/10.1152/ajpregu.00671.2010DOI Listing
June 2011

Intercostal muscle blood flow limitation during exercise in chronic obstructive pulmonary disease.

Am J Respir Crit Care Med 2010 Nov 9;182(9):1105-13. Epub 2010 Jul 9.

Department of Critical Care Medicine and Pulmonary Services, Evangelismos Hospital, M. Simou, and G.P. Livanos Laboratories, National and Kapodistrian University of Athens, Athens, Greece.

Rationale: It has been hypothesized that, because of the high work of breathing sustained by patients with chronic obstructive pulmonary disease (COPD) during exercise, blood flow may increase in favor of the respiratory muscles, thereby compromising locomotor muscle blood flow.

Objectives: To test this hypothesis by investigating whether, at the same work of breathing, intercostal muscle blood flow during exercise is as high as during resting isocapnic hyperpnea when respiratory and locomotor muscles do not compete for the available blood flow.

Methods: Intercostal and vastus lateralis muscle perfusion was measured simultaneously in 10 patients with COPD (FEV₁ = 50.5 ± 5.5% predicted) by near-infrared spectroscopy using indocyanine green dye.

Measurements And Main Results: Measurements were made at several exercise intensities up to peak work rate (WRpeak) and subsequently during resting hyperpnea at minute ventilation levels up to those at WRpeak. During resting hyperpnea, intercostal muscle blood flow increased with the power of breathing to 11.4 ± 1.6 ml/min per 100 g at the same ventilation recorded at WRpeak. Conversely, during graded exercise, intercostal muscle blood flow remained unchanged from rest up to 50% WRpeak (6.8 ± 1.3 ml/min per 100 g) and then fell to 4.5 ± 0.8 ml/min per 100 g at WRpeak (P = 0.003). Cardiac output plateaued above 50% WRpeak (8.4 ± 0.1 l/min), whereas vastus lateralis muscle blood flow increased progressively, reaching 39.8 ± 7.1 ml/min per 100 g at WRpeak.

Conclusions: During intense exercise in COPD, restriction of intercostal muscle perfusion but preservation of quadriceps muscle blood flow along with attainment of a plateau in cardiac output represents the inability of the circulatory system to satisfy the energy demands of locomotor and respiratory muscles.
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http://dx.doi.org/10.1164/rccm.201002-0172OCDOI Listing
November 2010

Expiratory muscle loading increases intercostal muscle blood flow during leg exercise in healthy humans.

J Appl Physiol (1985) 2010 Aug 27;109(2):388-95. Epub 2010 May 27.

Department of Critical Care Medicine and Pulmonary Services, Evangelismos Hospital, M. Simou, and G. P. Livanos Laboratories, Athens, Greece.

We investigated whether expiratory muscle loading induced by the application of expiratory flow limitation (EFL) during exercise in healthy subjects causes a reduction in quadriceps muscle blood flow in favor of the blood flow to the intercostal muscles. We hypothesized that, during exercise with EFL quadriceps muscle blood flow would be reduced, whereas intercostal muscle blood flow would be increased compared with exercise without EFL. We initially performed an incremental exercise test on eight healthy male subjects with a Starling resistor in the expiratory line limiting expiratory flow to approximately 1 l/s to determine peak EFL exercise workload. On a different day, two constant-load exercise trials were performed in a balanced ordering sequence, during which subjects exercised with or without EFL at peak EFL exercise workload for 6 min. Intercostal (probe over the 7th intercostal space) and vastus lateralis muscle blood flow index (BFI) was calculated by near-infrared spectroscopy using indocyanine green, whereas cardiac output (CO) was measured by an impedance cardiography technique. At exercise termination, CO and stroke volume were not significantly different during exercise, with or without EFL (CO: 16.5 vs. 15.2 l/min, stroke volume: 104 vs. 107 ml/beat). Quadriceps muscle BFI during exercise with EFL (5.4 nM/s) was significantly (P = 0.043) lower compared with exercise without EFL (7.6 nM/s), whereas intercostal muscle BFI during exercise with EFL (3.5 nM/s) was significantly (P = 0.021) greater compared with that recorded during control exercise (0.4 nM/s). In conclusion, increased respiratory muscle loading during exercise in healthy humans causes an increase in blood flow to the intercostal muscles and a concomitant decrease in quadriceps muscle blood flow.
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http://dx.doi.org/10.1152/japplphysiol.01290.2009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2928598PMC
August 2010
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