Sex differences in muscle excitation and oxygenation, but not in force fluctuations or active hyperemia resulting from a fatiguing, bilateral isometric task

2021 ◽  
Author(s):  
Joshua L Keller ◽  
John Paul Vance Anders ◽  
Tyler J Neltner ◽  
Terry J Housh ◽  
Richard J Schmidt ◽  
...  
Keyword(s):  
Blood Flow ◽  
Sex Difference ◽  
Near Infrared ◽  
Task Force ◽  
Vastus Lateralis ◽  
Muscle Blood Flow ◽  
Rate Of Change ◽  
Force Fluctuations ◽  
Rate Of Increase ◽  
The Right

Abstract It remains to be fully elucidated if there are sex-specific physiological adjustments within the human neuromuscular and vascular systems that contribute to symptoms of fatigue during a sustained bilateral task. This, in part, is likely due to various limitations in experimental design such as an inability to independently record force fluctuations from each limb. Objective: Therefore, the purpose of the current study was to examine the fatigue-induced changes in muscle excitation, force fluctuations, skeletal muscle tissue saturation (StO2), and muscle blood flow resulting from a sustained, bilateral task. Approach: Thirty healthy, college-aged adults (15 males, 15 females) performed a bilateral leg task at 25% of maximum voluntary isometric (MVIC). Before and after the task, MVICs were completed. Resting and post-task femoral artery blood flow (FABF) were determined. Muscle excitation was quantified as electromyographic amplitude (EMG AMP) from the right and left vastus lateralis. During the task, force fluctuations were determined independently from each leg. The StO2 signal was collected with a near-infrared spectroscopy device attached to the right vastus lateralis. The rate of change in these variables was calculated via simple linear regression. The exercise-induced magnitude of change in MVIC (i.e., performance fatigability) and FABF (i.e., active hyperemia) was determined. Main results: There was no sex difference in the percent decline in MVIC (20.5±20.1% vs. 16.4± 3.5%; p>0.05). There were no inter-leg differences in EMG AMP or force fluctuations. The males exhibited a faster rate of increase in EMG AMP (b=0.13 vs. b=0.08; p<0.001), whereas the females exhibited a slower rate of decline in StO2 (b=-0.049 vs. b=-0.080). There was no sex difference in force fluctuations or change in FABF. Significance: Males and females likely have different neuromuscular strategies and muscle characteristics, but these did not elicit a sex difference in performance fatigability.

Human respiratory muscle blood flow measured by near-infrared spectroscopy and indocyanine green

2008 ◽  
Vol 104 (4) ◽  
pp. 1202-1210 ◽  
Author(s):  
Jordan A. Guenette ◽  
Ioannis Vogiatzis ◽  
Spyros Zakynthinos ◽  
Dimitrios Athanasopoulos ◽  
Maria Koskolou ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Infrared Spectroscopy ◽  
Respiratory Muscle ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Muscle Blood Flow ◽  
Work Of Breathing ◽  
Dilution Method ◽  
Transdiaphragmatic Pressure

Measurement of respiratory muscle blood flow (RMBF) in humans has important implications for understanding patterns of blood flow distribution during exercise in healthy individuals and those with chronic disease. Previous studies examining RMBF in humans have required invasive methods on anesthetized subjects. To assess RMBF in awake subjects, we applied an indicator-dilution method using near-infrared spectroscopy (NIRS) and the light-absorbing tracer indocyanine green dye (ICG). NIRS optodes were placed on the left seventh intercostal space at the apposition of the costal diaphragm and on an inactive control muscle (vastus lateralis). The primary respiratory muscles within view of the NIRS optodes include the internal and external intercostals. Intravenous bolus injection of ICG allowed for cardiac output (by the conventional dye-dilution method with arterial sampling), RMBF, and vastus lateralis blood flow to be quantified simultaneously. Esophageal and gastric pressures were also measured to calculate the work of breathing and transdiaphragmatic pressure. Measurements were obtained in five conscious humans during both resting breathing and three separate 5-min bouts of constant isocapnic hyperpnea at 27.1 ± 3.2, 56.0 ± 6.1, and 75.9 ± 5.7% of maximum minute ventilation as determined on a previous maximal exercise test. RMBF progressively increased (9.9 ± 0.6, 14.8 ± 2.7, 29.9 ± 5.8, and 50.1 ± 12.5 ml·100 ml−1·min−1, respectively) with increasing levels of ventilation while blood flow to the inactive control muscle remained constant (10.4 ± 1.4, 8.7 ± 0.7, 12.9 ± 1.7, and 12.2 ± 1.8 ml·100 ml−1·min−1, respectively). As ventilation rose, RMBF was closely and significantly correlated with 1) cardiac output ( r = 0.994, P = 0.006), 2) the work of breathing ( r = 0.995, P = 0.005), and 3) transdiaphragmatic pressure ( r = 0.998, P = 0.002). These data suggest that the NIRS-ICG technique provides a feasible and sensitive index of RMBF at different levels of ventilation in humans.

scholarly journals Near-infrared spectroscopy using indocyanine green dye for minimally invasive measurement of respiratory and leg muscle blood flow in patients with COPD

2018 ◽  
Vol 125 (3) ◽  
pp. 947-959 ◽  
Author(s):  
Zafeiris Louvaris ◽  
Helmut Habazettl ◽  
Harrieth Wagner ◽  
Spyros Zakynthinos ◽  
Peter Wagner ◽  
...  
Keyword(s):  
Blood Flow ◽  
Minimally Invasive ◽  
Indocyanine Green ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Muscle Blood Flow ◽  
Reference Method ◽  
Chronic Obstructive ◽  
Obstructive Pulmonary Disease ◽  
Muscle Perfusion

Reliability of near-infrared spectroscopy, measuring indocyanine green (ICG) for minimally invasive assessment of relative muscle blood flow during exercise has been examined in fit young individuals but not in chronic obstructive pulmonary disease (COPD). Here we ask whether it could be used to evaluate respiratory and locomotor muscle perfusion in COPD patients. Vastus lateralis muscle blood flow (MBF, the reference method calculated from arterial and muscle ICG concentration curves) and a blood flow index [BFI, calculated using only the (same) muscle ICG concentration curves] were compared in 10 patients (forced expiratory volume in 1 s: 51 ± 6% predicted) at rest and during cycling at 25, 50, 75, and 100% of peak work rate (WRpeak). Intercostal muscle MBF and BFI were also compared during isocapnic hyperpnea at rest, reproducing ventilation levels up to those at WRpeak. Intercostal and vastus lateralis BFI increased with increasing ventilation during hyperpnea (from 2.5 ± 0.3 to 4.5 ± 0.7 nM/s) and cycling load (from 1.0 ± 0.2 to 12.8 ± 1.9 nM/s), respectively. There were strong correlations between BFI and MBF for both intercostal ( r = 0.993 group mean data, r = 0.872 individual data) and vastus lateralis ( r = 0.994 group mean data, r = 0.895 individual data). Fold changes from rest in BFI and MBF did not differ for either the intercostal muscles or the vastus lateralis. Group mean BFI data showed strong interrelationships with respiratory and cycling workload, and whole body metabolic demand ( r ranged from 0.913 to 0.989) simultaneously recorded during exercise. We conclude that BFI is a reliable and minimally invasive tool for evaluating relative changes in respiratory and locomotor muscle perfusion from rest to peak exercise in COPD patient groups. NEW & NOTEWORTHY We show that noninvasive near-infrared spectroscopic (NIRS) detection of indocyanine green dye (ICG) after peripheral venous injection adequately reflects intercostal and locomotor muscle perfusion during exercise and hyperpnea in patients with chronic obstructive pulmonary disease (COPD). Mean, individual, and fold change responses from rest to exercise or hyperpnea correlated closely with the reference method, which requires arterial sampling. NIRS-ICG is a reliable, robust, and essentially noninvasive tool for assessing relative changes in intercostal and locomotor muscle perfusion in COPD patient groups.

Microvascular oxygen delivery-to-utilization mismatch at the onset of heavy-intensity exercise in optimally treated patients with CHF

2009 ◽  
Vol 297 (5) ◽  
pp. H1720-H1728 ◽  
Author(s):  
Priscila Abreu Sperandio ◽  
Audrey Borghi-Silva ◽  
Adriano Barroco ◽  
Luiz Eduardo Nery ◽  
Dirceu R. Almeida ◽  
...  
Keyword(s):  
Pharmacological Treatment ◽  
Near Infrared ◽  
Enzyme Inhibitors ◽  
Vastus Lateralis ◽  
Muscle Blood Flow ◽  
Angiotensin Converting Enzyme Inhibitors ◽  
Rate Of Change ◽  
Converting Enzyme Inhibitors ◽  
Mean Response Time ◽  
Subsequent Response

Impaired muscle blood flow at the onset of heavy-intensity exercise may transiently reduce microvascular O2 pressure and decrease the rate of O2 transfer from capillary to mitochondria in chronic heart failure (CHF). However, advances in the pharmacological treatment of CHF (e.g., angiotensin-converting enzyme inhibitors and third-generation β-blockers) may have improved microvascular O2 delivery to an extent that intramyocyte metabolic inertia might become the main locus of limitation of O2 uptake (V̇o2) kinetics. We assessed the rate of change of pulmonary V̇o2 (V̇o2p), (estimated) fractional O2 extraction in the vastus lateralis (∼Δ[deoxy-Hb+Mb] by near-infrared spectroscopy), and cardiac output (Q̇t) during high-intensity exercise performed to the limit of tolerance (Tlim) in 10 optimally treated sedentary patients (ejection fraction = 29 ± 8%) and 11 controls. Sluggish V̇o2p and Q̇t kinetics in patients were significantly related to lower Tlim values ( P < 0.05). The dynamics of Δ[deoxy-Hb+Mb], however, were faster in patients than controls [mean response time (MRT) = 15.9 ± 2.0 s vs. 19.0 ± 2.9 s; P < 0.05] with a subsequent response “overshoot” being found only in patients (7/10). Moreover, τV̇o2/MRT-[deoxy-Hb+Mb] ratio was greater in patients (4.69 ± 1.42 s vs. 2.25 ± 0.77 s; P < 0.05) and related to Q̇t kinetics and Tlim ( R = 0.89 and −0.78, respectively; P < 0.01). We conclude that despite the advances in the pharmacological treatment of CHF, disturbances in “central” and “peripheral” circulatory adjustments still play a prominent role in limiting V̇o2p kinetics and tolerance to heavy-intensity exercise in nontrained patients.

scholarly journals Systemic and vastus lateralis muscle blood flow and O2 extraction during ramp incremental cycle exercise

2013 ◽  
Vol 304 (9) ◽  
pp. R720-R725 ◽  
Author(s):  
Juan M. Murias ◽  
Matthew D. Spencer ◽  
Daniel A. Keir ◽  
Donald H. Paterson
Keyword(s):  
Blood Flow ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Muscle Blood Flow ◽  
Microvascular Blood Flow ◽  
Peripheral Blood Flow ◽  
Vastus Lateralis Muscle ◽  
Metabolic Demand ◽  
Active Muscle ◽  
Cycling Exercise

During ramp incremental cycling exercise increases in pulmonary O2 uptake (V̇o2p) are matched by a linear increase in systemic cardiac output ( Q). However, it has been suggested that blood flow in the active muscle microvasculature does not display similar linearity in blood flow relative to metabolic demand. This study simultaneously examined both systemic and regional (microvascular) blood flow and O2 extraction during incremental cycling exercise. Ten young men (V̇o2 peak = 4.2 ± 0.5 l/min) and 10 young women (V̇o2 peak = 3.2 ± 0.5 l/min) were recruited to perform two maximal incremental cycling tests on separate days. The acetylene open-circuit technique and mass spectrometry and volume turbine were used to measure Q (every minute) and breath-by-breath V̇o2p, respectively; systemic arterio-venous O2 difference (a-vO2diff) was calculated as V̇o2p/ Q on a minute-by-minute basis. Changes in near-infrared spectroscopy-derived muscle deoxygenation (Δ[HHb]) were used (in combination with V̇o2p data) to estimate the profiles of peripheral O2 extraction and blood flow of the active muscle microvasculature. The systemic Q-to-V̇o2p relationship was linear (∼5.8 l/min increase in Q for a 1 l/min increase in V̇o2p) with a-vO2diff displaying a hyperbolic response as exercise intensity increased toward V̇o2 peak. The peripheral blood flow response profile was described by an inverted sigmoid curve, indicating nonlinear responses relative to metabolic demand. The Δ[HHb] profile increased linearly with absolute V̇o2p until high-intensity exercise, thereafter displaying a “near-plateau”. Results indicate that systemic blood flow and thus O2 delivery does not reflect the profile of blood flow changes at the level of the microvasculature.

Muscular blood flow distribution patterns as a function of running speed in rats

1982 ◽  
Vol 243 (2) ◽  
pp. H296-H306 ◽  
Author(s):  
M. H. Laughlin ◽  
R. B. Armstrong
Keyword(s):  
Blood Flow ◽  
Muscle Blood Flow ◽  
Flow Distribution ◽  
Distribution Patterns ◽  
Left Renal Artery ◽  
Sprague Dawley ◽  
Vastus Intermedius ◽  
Slow Twitch ◽  
The Right ◽  
White Gastrocnemius

Muscle blood flow (BF) was measured using the radiolabeled microsphere technique within and among nine major muscles of rats before exercise and during treadmill walking or running at speeds of 15, 30, 45, 60, and 75 m/min. Measurements were made during exercise after 1 min of steady walking or running. Male Sprague-Dawley rats were chronically instrumented with 2 Silastic catheters, one in the ascending aorta via the right carotid artery for microsphere infusion and one in the left renal artery for arterial reference blood sample withdrawal. The preexercise results demonstrated that 1) BF to deep slow-twitch muscles was three to four times that to peripheral fast muscles (e.g., soleus and gastrocnemius BFs were 138 and 33 ml . min-1 . 100 g-1, respectively); 2) BFs to red portions within mixed muscles were three to four times those to white portions (e.g, red and white gastrocnemius BFs were 54 and 18 ml . min-1 . 100 g-1, respectively; and 3) there was a direct relationship (P less than 0.05) between BFs to muscles and their slow-twitch oxidative fiber populations. The results obtained during exercise demonstrated that 1) at the slowest speed studied (15 m/min) BFs to the red portions of muscles increased, whereas BFs to the white portions of the same muscles decreased; 2) BFs to all muscles (except soleus) were increased during running at 75 m/min when there was a range of flows of 30 ml . 100 g-1 . min-1 (white gastrocnemius) to 321 (vastus intermedius), 3) at all running speeds the increases in BF to muscles were directly related to the fast-twitch, high-oxidative fiber populations of the muscles; and 4) BFs to visceral tissues and fat were decreased during exercise.

Muscle blood flow during exercise in sedentary and trained hypothyroid rats

1995 ◽  
Vol 269 (6) ◽  
pp. H1949-H1954 ◽  
Author(s):  
R. M. McAllister ◽  
M. D. Delp ◽  
K. A. Thayer ◽  
M. H. Laughlin
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Citrate Synthase ◽  
Vastus Lateralis ◽  
Muscle Blood Flow ◽  
Treadmill Running ◽  
Exercise Intolerance ◽  
Vastus Lateralis Muscle ◽  
Blood Flows ◽  
Vastus Intermedius

Hypothyroidism is characterized by exercise intolerance. We hypothesized that active muscle blood flow during in vivo exercise is inadequate in the hypothyroid state. Additionally, we hypothesized that endurance exercise training would restore normal blood flow during acute exercise. To test these hypotheses, rats were made hypothyroid (Hypo) over 3-4 mo with propylthiouracil. A subset of Hypo rats was trained (THypo) on a treadmill at 30 m/min (15% grade) for 60 min/day 5 days/wk over 10-15 wk. Hypothyroidism was evidenced by approximately 80% reductions in plasma triiodothyronine levels in Hypo and THypo and by 40-50% reductions in citrate synthase activities in high oxidative muscles in Hypo compared with euthyroid (Eut) rats. Training efficacy was indicated by increased (25-100%) citrate synthase activities in muscles of THypo vs. Hypo. Regional blood flows were determined by the radiolabeled microsphere method before exercise and at 1-2 min of treadmill running at 15 m/min (0% grade). Preexercise muscle blood flows were generally similar among groups. During exercise, however, flows were lower in Hypo than in Eut for high oxidative muscles such as the red section of vastus lateralis [277 +/- 24 and 153 +/- 13 (SE) ml.min-1.100 g-1 for Eut and Hypo, respectively; P < 0.01] and vastus intermedius (317 +/- 32 and 187 +/- 20 ml.min-1.100 g-1 for Eut and Hypo, respectively; P < 0.01) muscles. Training (THypo) did not normalize these flows (168 +/- 24 and 181 +/- 24 ml.min-1.100 g-1 for red section of vastus lateralis and vastus intermedius muscles, respectively). Blood flows to low oxidative muscle, such as the white section of vastus lateralis muscle, were similar among groups (21 +/- 5, 25 +/- 4, and 34 +/- 7 ml.min-1.100 g-1 for Eut, Hypo, and THypo, respectively; P = NS). These findings indicate that hypothyroidism is associated with reduced blood flow to skeletal muscle during exercise, suggesting that impaired delivery of nutrients to and/or removal of metabolites from skeletal muscle contributes to the poor exercise tolerance characteristic of hypothyroidism.

Impact of Changes in Tissue Optical Properties on Near-Infrared Diffuse Correlation Spectroscopy Measures of Skeletal Muscle Blood Flow

2021 ◽  
Author(s):  
Miles F. Bartlett ◽  
Scott M. Jordan ◽  
Dennis M. Hueber ◽  
Michael D. Nelson
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Optical Properties ◽  
Near Infrared ◽  
Muscle Blood Flow ◽  
Reactive Hyperemia ◽  
Correlation Spectroscopy ◽  
Skeletal Muscle Blood Flow ◽  
Diffuse Correlation Spectroscopy ◽  
Tissue Optical Properties

Near-infrared diffuse correlation spectroscopy (DCS) is increasingly utilized to study relative changes in skeletal muscle blood flow. However, most diffuse correlation spectrometers assume that tissue optical properties- such as absorption (μa) and reduced scattering (μ's) coefficients- remain constant during physiological provocations, which is untrue for skeletal muscle. Here, we interrogate how changes in tissue μa and μ's affect DCS calculations of blood flow index (BFI). We recalculated BFI using raw autocorrelation curves and μa/μ's values recorded during a reactive hyperemia protocol in 16 healthy young individuals. First, we show that incorrectly assuming baseline μa and μ's substantially affects peak BFI and BFI slope when expressed in absolute terms (cm2/s, p<0.01) but these differences are abolished when expressed in relative terms (% baseline). Next, to evaluate the impact of physiologic changes in μa and μ's, we compared peak BFI and BFI slope when μa and μ's were held constant throughout the reactive hyperemia protocol versus integrated from a 3s-rolling average. Regardless of approach, group means for peak BFI and BFI slope did not differ. Group means for peak BFI and BFI slope were also similar following ad absurdum analyses, where we simulated supraphysiologic changes in μa/μ's. In both cases, however, we identified individual cases where peak BFI and BFI slope were indeed affected, with this result being driven by relative changes in μa over μ's. Overall, these results provide support for past reports in which μa/μ's were held constant but also advocate for real-time incorporation of μa and μ's moving forward.

scholarly journals The Vascular Side of Chronic Bed Rest: When a Therapeutic Approach Becomes Deleterious

2020 ◽  
Vol 9 (4) ◽  
pp. 918 ◽  
Author(s):  
Anna Pedrinolla ◽  
Alessandro L. Colosio ◽  
Roberta Magliozzi ◽  
Elisa Danese ◽  
Emine Kirmizi ◽  
...  
Keyword(s):  
Blood Flow ◽  
Shear Rate ◽  
Vascular Function ◽  
Inflammatory Markers ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Vascular Inflammation ◽  
Bed Rest ◽  
Total Hemoglobin ◽  
No Bioavailability

The interplay between chronic constraint and advanced aging on blood flow, shear-rate, vascular function, nitric oxide (NO)-bioavailability, microcirculation, and vascular inflammation factors is still a matter of debate. Ninety-eight individuals (Young, n = 28, 23 ± 3 yrs; Old, n = 36, 85 ± 7 yrs; Bedridden, n = 34, 88 ± 6 yrs) were included in the study. The bedridden group included old individuals chronically confined to bed (3.8 ± 2.3 yrs). A blood sample was collected and analyzed for plasma nitrate, and vascular inflammatory markers. Hyperemic response (∆peak) during the single passive leg movement (sPLM) test was used to measure vascular function. Skeletal muscle total hemoglobin was measured at the vastus lateralis during the sPLM test, by means of near infrared spectroscopy (NIRS). Bedridden subjects revealed a depletion of plasma nitrates compared with Old (−23.8%) and Young (−31.1%). Blood flow was lower in the Bedridden in comparison to Old (−20.1%) and Young (−31.7%). Bedridden presented lower sPLM ∆peak compared Old (−72.5%) and the Young (−83.3%). ∆peak of NIRS total hemoglobin was lower in the Bedridden compared to that in the Young (−133%). All vascular inflammatory markers except IL-6 were significantly worse in the Bedridden compared to Old and Young. No differences were found between the Old and Young in inflammatory markers. Results of this study confirm that chronic physical constraint induces an exacerbation of vascular disfunction and differential regulation of vascular-related inflammatory markers. The mechanisms involved in these negative adaptations seems to be associated with endothelial dysfunction and consequent diminished NO-bioavailability likely caused by the reduced shear-rate consequential to long-term reduction of physical activity.

Dependence of muscleV˙o 2on blood flow dynamics at onset of forearm exercise

1996 ◽  
Vol 81 (4) ◽  
pp. 1619-1626 ◽  
Author(s):  
R. L. Hughson ◽  
J. K. Shoemaker ◽  
M. E. Tschakovsky ◽  
J. M. Kowalchuk
Keyword(s):  
Blood Flow ◽  
Muscle Blood Flow ◽  
Venous Blood ◽  
Lactate Concentration ◽  
Flow Dynamics ◽  
Cross Sectional ◽  
Mean Response Time ◽  
Rate Of Increase ◽  
Blood Flow Dynamics ◽  
Forearm Exercise

Hughson, R. L., J. K. Shoemaker, M. E. Tschakovsky, and J. M. Kowalchuk. Dependence muscle ofV˙o 2on blood flow dynamics at the onset of forearm exercise. J. Appl. Physiol. 81(4): 1619–1626, 1996.—The hypothesis that the rate of increase in muscle O2 uptake (V˙o 2 mus) at the onset of exercise is influenced by muscle blood flow was tested during forearm exercise with the arm either above or below heart level to modify perfusion pressure. Ten young men exercised at a power of ∼2.2 W, and five of these subjects also worked at 1.4 W. Blood flow to the forearm was calculated from the product of blood velocity and cross-sectional area obtained with Doppler techniques. Venous blood was sampled from a deep forearm vein to determine O2 extraction. The rate of increase inV˙o 2 musand blood flow was assessed from the mean response time (MRT), which is the time to achieve ∼63% increase from baseline to steady state. In the arm below heart position during the 2.2-W exercise, blood flow andV˙o 2 musboth increased, with a MRT of ∼30 s. With the arm above the heart at this power, the MRTs for blood flow [79.8 ± 15.7 (SE) s] and V˙o 2 mus(50.2 ± 4.0 s) were both significantly slower. Consistent with these findings were the greater increases in venous plasma lactate concentration over resting values in the above heart position (2.8 ± 0.4 mmol/l) than in the below heart position (0.9 ± 0.2 mmol/l). At the lower power, both blood flow andV˙o 2 musalso increased more rapidly with the arm below compared with above the heart. These data support the hypothesis that changes in blood flow at the onset of exercise have a direct effect on oxidative metabolism through alterations in O2transport.

Principles, Techniques, and Limitations of Near Infrared Spectroscopy

2004 ◽  
Vol 29 (4) ◽  
pp. 463-487 ◽  
Author(s):  
Marco Ferrari ◽  
Leonardo Mottola ◽  
Valentina Quaresima
Keyword(s):  
Blood Flow ◽  
Near Infrared ◽  
Dynamic Balance ◽  
Exercise Physiology ◽  
Muscle Blood Flow ◽  
Subcutaneous Fat ◽  
Nir Spectroscopy ◽  
Radical Change ◽  
Cortical Activation ◽  
Muscle Energetics

In the last decade the study of the human brain and muscle energetics underwent a radical change, thanks to the progressive introduction of noninvasive techniques, including near-infrared (NIR) spectroscopy (NIRS). This review summarizes the most recent literature about the principles, techniques, advantages, limitations, and applications of NIRS in exercise physiology and neuroscience. The main NIRS instrumentations and measurable parameters will be reported. NIR light (700-1000 nm) penetrates superficial layers (skin, subcutaneous fat, skull, etc.) and is either absorbed by chromophores (oxy- and deoxyhemoglobin and myoglobin) or scattered within the tissue. NIRS is a noninvasive and relatively low-cost optical technique that is becoming a widely used instrument for measuring tissue O2 saturation, changes in hemoglobin volume and, indirectly, brain/muscle blood flow and muscle O2 consumption. Tissue O2 saturation represents a dynamic balance between O2 supply and O2 consumption in the small vessels such as the capillary, arteriolar, and venular bed. The possibility of measuring the cortical activation in response to different stimuli, and the changes in the cortical cytochrome oxidase redox state upon O2 delivery changes, will also be mentioned. Key words: tissue oximetry, oxidative metabolism, optical imaging, blood flow, oxygen consumption, exercise physiology

Sign in / Sign up

Export Citation Format

Share Document