Prior exercise speeds pulmonary O2 uptake kinetics by increases in both local muscle O2 availability and O2 utilization

2007 ◽  
Vol 103 (3) ◽  
pp. 771-778 ◽  
Author(s):  
Darren S. DeLorey ◽  
John M. Kowalchuk ◽  
Aaron P. Heenan ◽  
Gregory R. duManoir ◽  
Donald H. Paterson
Keyword(s):  
Near Infrared ◽  
Slow Component ◽  
Vastus Lateralis ◽  
Knee Extension ◽  
Vastus Lateralis Muscle ◽  
Phase 2 ◽  
Warm Up ◽  
Prior Exercise ◽  
Exercise Onset ◽  
Monoexponential Model

The effect of prior exercise on pulmonary O2 uptake (V̇o2p), leg blood flow (LBF), and muscle deoxygenation at the onset of heavy-intensity alternate-leg knee-extension (KE) exercise was examined. Seven subjects [27 ( 5 ) yr; mean (SD)] performed step transitions ( n = 3; 8 min) from passive KE following no warm-up (HVY 1) and heavy-intensity (Δ50%, 8 min; HVY 2) KE exercise. V̇o2p was measured breath-by-breath; LBF was measured by Doppler ultrasound at the femoral artery; and oxy (O2Hb)-, deoxy (HHb)-, and total (Hbtot) hemoglobin/myoglobin of the vastus lateralis muscle were measured continuously by near-infrared spectroscopy (NIRS; Hamamatsu NIRO-300). Phase 2 V̇o2p, LBF, and HHb data were fit with a monoexponential model. The time delay (TD) from exercise onset to an increase in HHb was also determined and an HHb effective time constant (HHb − MRT = TD + τ) was calculated. Prior heavy-intensity exercise resulted in a speeding ( P < 0.05) of phase 2 V̇o2p kinetics [HVY 1: 42 s ( 6 ); HVY 2: 37 s ( 8 )], with no change in the phase 2 amplitude [HVY 1: 1.43 l/min (0.21); HVY 2: 1.48 l/min (0.21)] or amplitude of the V̇o2p slow component [HVY 1: 0.18 l/min (0.08); HVY 2: 0.18 l/min (0.09)]. O2Hb and Hbtot were elevated throughout the on-transient following prior heavy-intensity exercise. The τLBF [HVY 1: 39 s ( 7 ); HVY 2: 47 s ( 21 ); P = 0.48] and HHb-MRT [HVY 1: 23 s ( 4 ); HVY 2: 21 s ( 7 ); P = 0.63] were unaffected by prior exercise. However, the increase in HHb [HVY 1: 21 μM ( 10 ); HVY 2: 25 μM ( 10 ); P < 0.001] and the HHb-to-V̇o2p ratio [(HHb/V̇o2p) HVY 1: 14 μM·l−1·min−1 ( 6 ); HVY 2: 17 μM·l−1·min−1 ( 5 ); P < 0.05] were greater following prior heavy-intensity exercise. These results suggest that the speeding of phase 2 τV̇o2p was the result of both elevated local O2 availability and greater O2 extraction evidenced by the greater HHb amplitude and HHb/V̇o2p ratio following prior heavy-intensity exercise.

Relationship between pulmonary O2 uptake kinetics and muscle deoxygenation during moderate-intensity exercise

2003 ◽  
Vol 95 (1) ◽  
pp. 113-120 ◽  
Author(s):  
Darren S. DeLorey ◽  
John M. Kowalchuk ◽  
Donald H. Paterson
Keyword(s):  
Near Infrared ◽  
Vastus Lateralis ◽  
Metabolic Activation ◽  
Moderate Intensity ◽  
Vastus Lateralis Muscle ◽  
Phase 2 ◽  
Moderate Intensity Exercise ◽  
Muscle Deoxygenation ◽  
Monoexponential Model ◽  
Kinetics Of

The temporal relationship between the kinetics of phase 2 pulmonary O2 uptake (V̇o2p) and deoxygenation of the vastus lateralis muscle was examined during moderate-intensity leg-cycling exercise. Young adults (5 men, 6 women; 23 ± 3 yr; mean ± SD) performed repeated transitions on 3 separate days from 20 W to a constant work rate corresponding to 80% of lactate threshold. Breath-by-breath V̇o2p was measured by mass spectrometer and volume turbine. Deoxyhemoglobin (HHb), oxyhemoglobin, and total hemoglobin and myoglobin were sampled each second by near-infrared spectroscopy (Hamamatsu NIRO-300). V̇o2p data were filtered, interpolated to 1 s, and averaged to 5-s bins; HHb data were averaged to 5-s bins. Phase 2 V̇o2p data were fit with a monoexponential model. For HHb, a time delay (TDHHb) from exercise onset to an increase in HHb was determined, and thereafter data were fit with a monoexponential model. The time constant for V̇o2p (30 ± 8 s) was slower ( P < 0.01) than that for HHb (10 ± 3 s). The TDHHb before an increase in HHb was 13 ± 2 s. The possible mechanisms of the TDHHb are discussed with reference to metabolic activation and matching of local muscle O2 delivery and O2 utilization. After this initial TDHHb, the kinetics of local muscle deoxygenation were faster than those of phase 2 V̇o2p (and presumably muscle O2 consumption), reflecting increased O2 extraction and a mismatch between local muscle O2 consumption and perfusion.

scholarly journals Comparison of femoral blood gases and muscle near-infrared spectroscopy at exercise onset in humans

1999 ◽  
Vol 86 (2) ◽  
pp. 687-693 ◽  
Author(s):  
Maureen J. MacDonald ◽  
Mark A. Tarnopolsky ◽  
Howard J. Green ◽  
Richard L. Hughson
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Femoral Vein ◽  
Blood Gases ◽  
Moderate Intensity ◽  
Reliable Estimate ◽  
Vastus Lateralis Muscle ◽  
Exercise Onset

We hypothesized that near-infrared spectroscopy (NIRS) measures of hemoglobin and/or myoglobin O2 saturation (IR-So 2) in the vascular bed of exercising muscle would parallel changes in femoral venous O2 saturation (S[Formula: see text]) at the onset of leg-kicking exercise in humans. Six healthy subjects performed transitions from rest to 48 ± 3 (SE)-W two-legged kicking exercise while breathing 14, 21, or 70% inspired O2. IR-So 2 was measured over the vastus lateralis muscle continuously during all tests, and femoral venous and radial artery blood samples were drawn simultaneously during rest and during 5 min of exercise. In all gas-breathing conditions, there was a rapid decrease in both IR-So 2 and SfvO2 at the onset of moderate-intensity leg-kicking exercise. Although SfvO2 remained at low levels throughout exercise, IR-So 2increased significantly after the first minute of exercise in both normoxia and hyperoxia. Contrary to the hypothesis, these data show that NIRS does not provide a reliable estimate of hemoglobin and/or O2 saturation as reflected by direct femoral vein sampling.

Speeding of V̇o2 kinetics during moderate-intensity exercise subsequent to heavy-intensity exercise is associated with improved local O2 distribution

2011 ◽  
Vol 111 (5) ◽  
pp. 1410-1415 ◽  
Author(s):  
Juan M. Murias ◽  
Matthew D. Spencer ◽  
Darren S. DeLorey ◽  
Brendon J. Gurd ◽  
John M. Kowalchuk ◽  
...  
Keyword(s):  
Phase Ii ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Moderate Intensity ◽  
Vastus Lateralis Muscle ◽  
Moderate Intensity Exercise ◽  
Young Males ◽  
Monoexponential Model ◽  
O2 Distribution ◽  
Priming Exercise

The relationship between the adjustment of muscle deoxygenation (Δ[HHb]) and phase II VO2p during moderate-intensity exercise was examined before (Mod 1) and after (Mod 2) a bout of heavy-intensity “priming” exercise. Moderate intensity VO2p and Δ[HHb] kinetics were determined in 18 young males (26 ± 3 yr). VO2p was measured breath-by-breath. Changes in Δ[HHb] of the vastus lateralis muscle were measured by near-infrared spectroscopy. VO2p and Δ[HHb] response profiles were fit using a monoexponential model, and scaled to a relative % of the response (0–100%). The Δ[HHb]/V̇o2 ratio for each individual (reflecting the local matching of O2 delivery to O2 utilization) was calculated as the average Δ[HHb]/V̇o2 response from 20 s to 120 s during the exercise on-transient. Phase II τVO2p was reduced in Mod 2 compared with Mod 1 ( P < 0.05). The effective τ′Δ[HHb] remained the same in Mod 1 and Mod 2 ( P > 0.05). During Mod 1, there was an “overshoot” in the Δ[HHb]/V̇o2 ratio (1.08; P < 0.05) that was not present during Mod 2 (1.01; P > 0.05). There was a positive correlation between the reduction in the Δ[HHb]/V̇o2 ratio and the smaller τVO2p from Mod 1 to Mod 2 ( r = 0.78; P < 0.05). This study showed that a smaller τVO2p during a moderate bout of exercise subsequent to a heavy-intensity priming exercise was associated with improved microvascular O2 delivery during the on-transient of exercise, as suggested by a smaller Δ[HHb]/V̇o2 ratio.

Effects of prior heavy-intensity exercise on pulmonary O2 uptake and muscle deoxygenation kinetics in young and older adult humans

2004 ◽  
Vol 97 (3) ◽  
pp. 998-1005 ◽  
Author(s):  
Darren S. DeLorey ◽  
John M. Kowalchuk ◽  
Donald H. Paterson
Keyword(s):  
Older Adults ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Muscle Blood Flow ◽  
Moderate Intensity ◽  
Vastus Lateralis Muscle ◽  
Warm Up ◽  
Muscle Deoxygenation ◽  
Older Subjects ◽  
Young Subjects

Pulmonary O2 uptake (V̇o2p) and muscle deoxygenation kinetics were examined during moderate-intensity cycling (80% lactate threshold) without warm-up and after heavy-intensity warm-up exercise in young ( n = 6; 25 ± 3 yr) and older ( n = 5; 68 ± 3 yr) adults. We hypothesized that heavy warm-up would speed V̇o2p kinetics in older adults consequent to an improved intramuscular oxygenation. Subjects performed step transitions ( n = 4; 6 min) from 20 W to moderate-intensity exercise preceded by either no warm-up or heavy-intensity warm-up (6 min). V̇o2p was measured breath by breath. Oxy-, deoxy-(HHb), and total hemoglobin and myoglobin (Hbtot) of the vastus lateralis muscle were measured continuously by near-infrared spectroscopy (NIRS). V̇o2p (phase 2; τ) and HHb data were fit with a monoexponential model. After heavy-intensity warm-up, oxyhemoglobin (older subjects: 13 ± 9 μM; young subjects: 9 ± 8 μM) and Hbtot (older subjects: 12 ± 8 μM; young subjects: 14 ± 10 μM) were elevated ( P < 0.05) relative to the no warm-up pretransition baseline. In older adults, τV̇o2p adapted at a faster rate ( P < 0.05) after heavy warm-up (30 ± 7 s) than no warm-up (38 ± 5 s), whereas in young subjects, τV̇o2p was similar in no warm-up (26 ± 7 s) and heavy warm-up (25 ± 5 s). HHb adapted at a similar rate in older and young adults after no warm-up; however, in older adults after heavy warm-up, the adaptation of HHb was slower ( P < 0.01) compared with young and no warm-up. These data suggest that, in older adults, V̇o2p kinetics may be limited by a slow adaptation of muscle blood flow and O2 delivery.

Adaptation of pulmonary O2 uptake kinetics and muscle deoxygenation at the onset of heavy-intensity exercise in young and older adults

2005 ◽  
Vol 98 (5) ◽  
pp. 1697-1704 ◽  
Author(s):  
Darren S. DeLorey ◽  
John M. Kowalchuk ◽  
Donald H. Paterson
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Muscle Blood Flow ◽  
Constant Load ◽  
Vastus Lateralis Muscle ◽  
Muscle Deoxygenation ◽  
Exercise Onset ◽  
Concentration Changes

The purpose was to examine the adaptation of pulmonary O2 uptake (V̇o2p) and deoxygenation of the vastus lateralis muscle at the onset of heavy-intensity, constant-load cycling exercise in young (Y; 24 ± 4 yr; mean ± SD; n = 5) and older (O; 68 ± 3 yr; n = 6) adults. Subjects performed repeated transitions on 4 separate days from 20 W to a work rate corresponding to heavy-intensity exercise. V̇o2p was measured breath by breath. The concentration changes in oxyhemoglobin, deoxyhemoglobin (HHb), and total hemoglobin/myoglobin were determined by near-infrared spectroscopy (Hamamatsu NIRO-300). V̇o2p data were filtered, interpolated to 1 s, and averaged to 5-s bins. HHb-near-infrared spectroscopy data were filtered and averaged to 5-s bins. A monoexponential model was used to fit V̇o2p [phase 2, time constant (τ) of V̇o2p] and HHb [following the time delay (TD) from exercise onset to the start of an increase in HHb] data. The τV̇o2p was slower ( P < 0.001) in O (49 ± 8 s) than Y (29 ± 4 s). The HHb TD was similar in O (8 ± 3 s) and Y (7 ± 1 s); however, the τ HHb following TD was faster ( P < 0.05) in O (8 ± 2 s) than Y (14 ± 2 s). The slower V̇o2p kinetics and faster muscle deoxygenation in O compared with Y during heavy-intensity exercise imply that the kinetics of muscle perfusion are slowed relatively more than those of V̇o2p in O. This suggests that the slowed V̇o2p kinetics in O may be a consequence of a slower adaptation of local muscle blood flow relative to that in Y.

Effect of age on O2 uptake kinetics and the adaptation of muscle deoxygenation at the onset of moderate-intensity cycling exercise

2004 ◽  
Vol 97 (1) ◽  
pp. 165-172 ◽  
Author(s):  
Darren S. DeLorey ◽  
John M. Kowalchuk ◽  
Donald H. Paterson
Keyword(s):  
Time Delay ◽  
Time Constant ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Muscle Blood Flow ◽  
Moderate Intensity ◽  
Vastus Lateralis Muscle ◽  
Phase 2 ◽  
Cycling Exercise ◽  
Muscle Deoxygenation

Phase 2 pulmonary O2 uptake (V̇o2p) kinetics are slowed with aging. To examine the effect of aging on the adaptation of V̇o2p and deoxygenation of the vastus lateralis muscle at the onset of moderate-intensity constant-load cycling exercise, young (Y) ( n = 6; 25 ± 3 yr) and older (O) ( n = 6; 68 ± 3 yr) adults performed repeated transitions from 20 W to work rates corresponding to moderate-intensity (80% estimated lactate threshold) exercise. Breath-by-breath V̇o2p was measured by mass spectrometer and volume turbine. Deoxy (HHb)-, oxy-, and total Hb and/or myoglobin were determined by near-infrared spectroscopy (Hamamatsu NIRO-300). V̇o2p data were filtered, interpolated to 1 s, and averaged to 5-s bins. HHb data were filtered and averaged to 5-s bins. V̇o2p data were fit with a monoexponential model for phase 2, and HHb data were analyzed to determine the time delay from exercise onset to the start of an increase in HHb and thereafter were fit with a single-component exponential model. The phase 2 time constant for V̇o2p was slower ( P < 0.01) in O (Y: 26 ± 7 s; O: 42 ± 9 s), whereas the delay before an increase in HHb (Y: 12 ± 2 s; O: 11 ± 1 s) and the time constant for HHb after the time delay (Y: 13 ± 10 s; O: 9 ± 3 s) were similar in Y and O. However, the increase in HHb for a given increase in V̇o2p (Y: 7 ± 2 μM·l−1·min−1; O: 13 ± 4 μM·l−1·min−1) was greater ( P < 0.01) in O compared with Y. The slower V̇o2p kinetics in O compared with Y adults was accompanied by a slower increase of local muscle blood flow and O2 delivery discerned from a faster and greater muscle deoxygenation relative to V̇o2p in O.

Time-course of V̇O2 kinetics responses during moderate-intensity exercise subsequent to HIIT vs moderate-intensity continuous training in type 2 diabetes.

2021 ◽  
Author(s):  
Norita Gildea ◽  
Adam McDermott ◽  
Joel Rocha ◽  
Donal O'Shea ◽  
Simon Green ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Time Course ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Moderate Intensity ◽  
Vastus Lateralis Muscle ◽  
Maximal Heart Rate ◽  
Continuous Training ◽  
Muscle Deoxygenation

We assessed the time course of changes in oxygen uptake (V̇O2) and muscle deoxygenation (i.e., deoxygenated haemoglobin and myoglobin, [HHb+Mb]) kinetics during transitions to moderate-intensity cycling following 12-weeks of low-volume high-intensity interval training (HIIT) vs. moderate-intensity continuous training (MICT) in adults with type 2 diabetes (T2D). Participants were randomly assigned to MICT (n=10, 50 min of moderate-intensity cycling), HIIT (n=9, 10x1 min at ~90% maximal heart rate) or non-exercising control (n=9) groups. Exercising groups trained 3 times per week and measurements were taken every 3 weeks. [HHb+Mb] kinetics were measured by near-infrared spectroscopy at the vastus lateralis muscle. The local matching of O2 delivery to O2 utilization was assessed by the Δ[HHb+Mb]/ΔV̇O2ratio. The pretraining time constant of the primary phase of V̇O2 (τV̇O2p ) decreased (P<0.05) at wk 3 of training in both MICT (from 44±12 to 32±5 s) and HIIT (from 42±8 to 32 ± 4 s) with no further changes thereafter; while no changes were reported in controls. The pretraining overall dynamic response of muscle deoxygenation (τ'[HHb+Mb]) was faster than τV̇O2p in all groups, resulting in Δ[HHb+Mb]/V̇O2p showing a transient "overshoot" relative to the subsequent steady-state level. After 3 wks, the Δ[HHb+Mb]/V̇O2p overshoot was eliminated only in the training groups, so that τ'[HHb+Mb] was not different to τV̇O2p in MICT and HIIT. The enhanced V̇O2 kinetics response consequent to both MICT and HIIT in T2D was likely attributed to a training-induced improvement in matching of O2 delivery to utilization.

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

2005 ◽  
Vol 99 (2) ◽  
pp. 683-690 ◽  
Author(s):  
Nicole D. Paterson ◽  
John M. Kowalchuk ◽  
Donald H. Paterson
Keyword(s):  
Blood Flow ◽  
Femoral Artery ◽  
Time Course ◽  
Slow Component ◽  
Knee Extension ◽  
Artery Blood Flow ◽  
Phase 2 ◽  
Femoral Artery Blood Flow ◽  
Knee Extension Exercise ◽  
Kinetics Of

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

The Effect of ACL Reconstruction on Involved and Contralateral Limb Vastus Lateralis Morphology and Histology: A Pilot Study

2019 ◽  
Author(s):  
Eric C. Leszczynski ◽  
Christopher Kuenze ◽  
Brett Brazier ◽  
Joseph Visker ◽  
David P. Ferguson
Keyword(s):  
Fiber Type ◽  
Vastus Lateralis ◽  
Knee Extension ◽  
Cross Sectional Area ◽  
Vastus Lateralis Muscle ◽  
Myosin Isoforms ◽  
Sectional Area ◽  
Cross Sectional ◽  
Contralateral Limb ◽  
Significant Difference

AbstractQuadriceps muscle weakness is a commonly reported issue post anterior cruciate ligament reconstruction (ACLR), with minimal information related to skeletal muscle morphology following surgery. The purpose is to examine the morphological and functional differences in the vastus lateralis muscle from patient's ACLR and contralateral leg. Three physically active ACLR participants were recruited and secured to a dynamometer to perform maximal voluntary isometric knee extension contractions (MVIC) of the ACLR and contralateral limb. Muscle biopsies of the ACLR and contralateral vastus lateralis were performed, then sectioned, and stained for myosin isoforms to determine fiber type. Confocal images were acquired, and ImageJ software was used to determine the fiber type and cross-sectional area (CSA). There was a significant reduction in CSA of the type IIa and type IIx muscle fiber cells between healthy (IIa: 7,718 ± 1,295 µm2; IIx; 5,800 ± 601 µm2) and ACLR legs (IIa: 4,139 ± 709 µm2; IIx: 3,708 ± 618 µm2) (p < 0.05), while there was no significant difference in knee extension MVIC torque between legs (healthy limb: 2.42 ± 0.52 Nm/kg; ACLR limb: 2.05 ± 0.24 Nm/kg, p = 0.11). The reduction in the cross-sectional area of the ACLR type II fibers could impair function and increase secondary injury risk.

scholarly journals Near-Infrared Spectroscopy Is Promising to Detect Iliac Artery Flow Limitations in Athletes: A Pilot Study

2018 ◽  
Vol 2018 ◽  
pp. 1-11
Author(s):  
Martijn van Hooff ◽  
Goof Schep ◽  
Eduard Meijer ◽  
Mart Bender ◽  
Hans Savelberg
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Diagnostic Techniques ◽  
Vastus Lateralis Muscle ◽  
Diagnostic Potential ◽  
Substantial Risk ◽  
Artery Flow ◽  
Healthy Participants

Endurance cyclists have a substantial risk to develop flow limitations in the iliac arteries during their career. These flow limitations are due to extreme hemodynamic stress which may result in functional arterial kinking and/or intravascular lesions. Early diagnosis may improve outcome and could prevent the necessity for surgical vascular repair. However, current diagnostic techniques have unsatisfactory sensitivity and cannot be applied during exercise. Near-infrared spectroscopy (NIRS) has shown great diagnostic potential in peripheral vascular disease and might bring a solution since it measures tissue oxygenation in real time during and after exercise. This report describes the first experiences of the application of NIRS in the vastus lateralis muscle during and after maximal graded cycling exercise in ten healthy participants and in three patients with flow limitations due to (1) subtle functional kinking, (2) an intravascular lesion, and (3) severe functional kinking. The results are put into perspective based on an empirically fitted model. Delayed recovery, showing clearly different types of patterns of tissue reoxygenation after exercise, was found in the affected athletes compared with the healthy participants. In the patients that had kinking of the arteries, tissue reoxygenation was clearly more delayed if NIRS was measured in provocative position with flexed hip. In this pilot experiment, clearly distinctive reoxygenation patterns are observed during recovery consistent with severity of flow limitation, indicating that NIRS is a promising diagnostic tool to detect and grade arterial flow limitations in athletes. Our findings may guide research and optimization of NIRS for future clinical application.

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