We thank all participants in this study and technical laboratory staff for their support in the measurements taken at the Laboratory of Exercise Physiology. The authors FC-B and ME-R were partially supported by the III, IV, and V Research &#38; Innovation Competitions of the School Health Sciences (Faculty of Medicine, Pontificia Universidad Cat&#243;lica de Chile).&#160;The author RC-C was funded by Project supported by the Competition for Research Regular Projects, year 2023, code LPR23-17, Universidad Tecnol&#243;gica Metropolitana.

The protocol was approved by the Institutional Review Board of the Pontificia Universidad Cat&#243;lica de Chile (projects n&#186; 210525001 and 220608010), and the study was conducted in accordance with the Declaration of Helsinki. All participants provided written informed consent before participating in the testing described.
1. Placement and setup of NIRS wearables
NOTE: Various NIRS wearables and data acquisition software can be utilized. Researchers should thoroughly consult the manufacturer&#39;s instructions and guidelines to ensure proper setup and usage. In this study, the devices that use a continuous wave register of the NIRS signal are used. These commercial devices are easy to use, but they can only detect changes in light attenuation relative to the reference or baseline phase and cannot detect absolute concentrations like other devices that employ a time-domain register of NIRS.

<ol>
	<li>NIRS wearables preparation and general placement guidelines
	<ol>
		<li>Before placing the devices and starting the measurements, ensure that all wearables are fully charged. 
		NOTE: For the devices used in this study, the manufacturer reports that a battery with a full charge can register 6&#8211;8 h continuously.</li>
		<li>Apply double-sided adhesive tape to all wearables to secure them to the participant&#39;s skin, ensuring that the tape does not obstruct the light emitters and detectors.</li>
		<li>Cover all wearables with a layer of cling film, followed by a layer of a waterproof adhesive dressing to protect them from sweat.</li>
		<li>Before placing the devices, clean the target area with an alcohol pad to remove any residue that may interfere with the register (e.g., creams, cosmetics, etc.). If necessary, shave the area around the target site, as hair can interfere with NIRS signals. 
		NOTE: It is recommended that a thorough hand wash be performed before placing any device on the participant&#39;s skin to prevent potential contamination. Wearing gloves is encouraged, as it can further reduce the risk of contamination.</li>
		<li>Once all wearables are correctly placed on the participant&#39;s skin (see section 1.2), secure them with a layer of elastic therapeutic tape. If additional fixation is needed, use an elastic bandage wrap of dark color, ensuring that excessive compression does not alter the measurements (less than the 25 mm Hg capillary occlusion pressure measured by a conventional sphygmomanometer).</li>
		<li>Place a black cloth over all wearables to prevent ambient light from penetrating. If covering the area with a cloth is not possible (around 6 cm2), use black elastic therapeutic tape to block ambient light.</li>
	</ol>
	</li>
	<li>NIRS device placement 
	NOTE: Ensure that NIRS wearables devices are placed so that ON/OFF and setting buttons are easily accessible.
	<ol>
		<li>Prefrontal Cortex: Place the NIRS probe on the left or right dorsolateral prefrontal cortex, approximately 10 mm above the participant&#39;s superciliary arch, similar to Fp1 electrode placement according to the modified international EEG 10-20 system21.</li>
		<li>m.Intercostales: Place the NIRS probe over the 7th intercostal space at the right anterior axillary line22,23,24. If, for some reason, it is not positioned over the right hemithorax, position it over the left hemithorax, but the signal from the heart rate may be more pronounced on the left side.
		<ol>
			<li>To confirm NIRS penetration depth, use a B&#8211;mode ultrasound to verify the distance from subcutaneous tissue to the outer border of the m.Intercostales. For measurements at m.Intercostales, ensure that the distance between skin and muscle is less than 15 mm.</li>
		</ol>
		</li>
		<li>m.Vastus Lateralis: Place the NIRS probe 5 cm lateral to the imaginary line&#39;s midpoint, connecting the patella&#39;s upper edge and the greater trochanter of the femur24,25,26.
		<ol>
			<li>To ensure that the adipose tissue thickness (ATT) does not alter the register of the NIRS signal, measure skinfold thickness to confirm the NIRS penetration depth27. For measurements at m.Vastus Lateralis, ensure that the ATT is less than 20 mm.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>NIRS software setup
	<ol>
		<li>Once all NIRS wearables are correctly placed (see section 1.2), power them ON before starting the measurement.</li>
		<li>Launch the data acquisition software provided by the manufacturer, create a new file, and link the NIRS wearables.</li>
		<li>After all NIRS wearables are successfully linked, set the sampling rate to 10 Hz for data acquisition and analog-to-digital conversion for the assessed tissues. For prefrontal cortex measurements, adjust the differential pathlength factor (DPF) according to the age-dependent DPF for each participant28. For muscle measurement, set the DPF to 4, as used in previous protocols with athletes as subjects of study29,30.</li>
	</ol>
	</li>
</ol>
2. Calibration and setup of ergospirometer 
<ol>
	<li>Volume calibration
	<ol>
		<li>Open the ergospirometer&#39;s software provided by the manufacturer to begin the calibration process.</li>
		<li>Attach the flow meter to a 28 mm turbine with a syringe adapter. Connect one corrugated tube to the syringe adapter and the other to a 3 L calibration syringe.</li>
		<li>Perform six withdrawal/injection maneuvers, maintaining a constant flow rate. Upon completion, the software will automatically confirm if the calibration test has passed.</li>
	</ol>
	</li>
	<li>Gas calibration 
	NOTE: Ensure the flow calibration is done before starting the gas calibration.
	<ol>
		<li>Air calibration
		<ol>
			<li>Ensure the sample line from the gas analyzer is disconnected from the calibration port and hanging freely. Then, initialize the calibration process.</li>
			<li>During calibration, a stable flat line is observed as the concentrations of oxygen (O2) and carbon dioxide (CO2) do not vary significantly (less than 5%). Once air calibration has been successfully completed, proceed to the metabolic gas calibration.</li>
		</ol>
		</li>
		<li>Metabolic gas calibration
		<ol>
			<li>Open the gas valves and verify that adequate pressure is delivered to the system by checking the manometer (consult the manufacturer for specific instructions).</li>
			<li>Connect the sample line to the calibration port and initialize the calibration process. Perform a 3 min pre-heating before starting the calibration, as advised by the manufacturer.</li>
			<li>If done correctly, after the 3 min pre-heating period, two flat lines should be observed: one fluctuating between room air (approximately 21.00% O2 and 0.04% CO2) and the other between the calibration gas (16.00% O2 and 5.00% CO2).</li>
			<li>Finally, disconnect the sample line from the calibration port and attach it to the mouthpiece that will be used for the upcoming test.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>
3. ECG electrode placement (12 leads)
<ol>
	<li>Prepare the skin by exfoliating with a cream and/or shaving any hair from the electrode placement sites if necessary. Clean the areas with an alcohol pad to remove any superficial tissue residues.</li>
	<li>Place the ECG electrodes as follows31:
	<ol>
		<li>Place the bipolar leads (Limb lead electrodes) as follows: Left arm (LA): left side of subclavicular fossa; Right arm (RA): right side of subclavicular fossa; Left leg (LL): anterior projection of left femoral head; Right leg (RL): anterior projection of right femoral head.</li>
		<li>Place the precordial lead electrodes as follows: V1: 4th intercostal space to the right of the sternum; V2: 4th intercostal space to the left of the sternum (in line with V1); V3: Midway between V2 and V4; V4: 5th intercostal space at the midclavicular line; V5: anterior axillary line at the same level as V4; V6: midaxillary line at the same level as V4 and V5.</li>
	</ol>
	</li>
</ol>
4. Incremental maximal exercise test (cardiopulmonary exercise testing, CPET)
<ol>
	<li>Ask the participant to sit on the bike, ensuring that the seat and handlebars are adjusted to their height for optimal comfort and positioning. 
	NOTE: It is advised to set the seat height so that the knee is slightly bent at full extension32. The handlebars should be positioned to allow for a slight flexion of the elbows.</li>
	<li>Attach a pulse oximeter to the participant&#39;s ear lobe, ensuring the site is clean by wiping it with an alcohol pad.</li>
	<li>Explain the protocol and instruct the participant to breathe through the mask before, during, and after the test. 
	NOTE: The participant must avoid talking or whistling while wearing the mask, as this can affect the ergospirometer&#39;s readings33.</li>
	<li>Once the participant is positioned and prepared, have the participant extend the right leg and wait 2 min for the start instruction (initial rest stage). Have the participant pedal at a cadence between 80&#8211;100 rpm for 6 min at 0.6 W&#183;kg-1 and 0.8 W&#183;kg-1 for women/men, respectively (warm-up phase). Then, increment the workload at a rate of 20 W&#183;min-&#185; for women and 25 W&#183;min-&#185; for men until the participant reaches exhaustion (exercise phase).</li>
	<li>After completing the exercise phase, instruct the participant to remain still and continue breathing into the mask for 3 min (cool-down or recovery phase).</li>
	<li>Once the exercise protocol is finished, carefully remove the pulse oximeter from the earlobe, the mask, all three NIRS wearables, and the ECG electrodes. 
	NOTE: To keep the laboratory ambient condition (e.g., air temperature ~20 &#177; 2 &#176;C, relative humidity ~40% &#177; 5%), it is a crucial criterion. Some participants can show a high sweat rate, which interferes with the fixation of devices on the skin and affects NIRS data recording. The use of ventilators can help to reduce hot thermoregulation by sweating.</li>
</ol>

The authors declare no conflict of interest.

There is significant potential in using NIRS wearables as a complementary tool to CPET for evaluating athletic performance and identifying central and peripheral exercise&#8211;limiting factors in aerobic or endurance athletes, given that NIRS technology has proven its validity and reliability in assessing microvascular hemodynamics in both cerebral and muscular regions37,38. However, to maximize the benefits of this technology, several considerations must be add...

Endurance athletes rely on an efficient balance of oxygen delivery and uptake to sustain high&#8211;intensity exercise and enhance their athletic performance1,2. The maximal oxygen uptake test (VO2-max) is a vital physiological assessment that determines sports performance by analyzing exhaled&#8211;gases and cardiorespiratory variables during incremental exercise intensity1. This assessment, known as ergospirometry or Cardiopulmonary Exercise Testing (CPET), reflects the exercise response of the cardiovascular, respiratory, and muscular systems3. Along these lines, the increased energy cost associated with breathing, referred to as the cost of breathing (COB), heightens the demand for nutrients and oxygen in the surrounding tissues. This phenomenon has been documented to potentially reduce blood flow to the muscles involved in active movements, resulting in a decreased tolerance to physical exertion and an early cessation of exercise progression due to the metabolic reflex4.
During a VO2&#8211;max test, it is also possible to identify the ventilatory thresholds (VTs), which correspond to specific exercise intensities marking the transition from aerobic to anaerobic metabolism (aerobic threshold or ventilatory threshold 1 [VT1], and anaerobic threshold or respiratory compensation point [RCP] or ventilatory threshold 2 [VT2])5. The VTs reflect the ventilatory responses that compensate for metabolic changes during incremental exercise6. By identifying these thresholds, CPET offers a comprehensive evaluation by integrating the responses of multiple biological systems critically engaged during high&#8211;intensity exercise.
However, while ergospirometry is widely considered the gold standard for evaluating CPET, it does not capture metabolic changes occurring at the muscle level. These changes are crucial for understanding the physiological limiting factors associated with the lack of progression during high&#8211;intensity exercise in endurance athletes. In this context, NIRS technology has emerged as a valuable tool in exercise science, aiding in analyzing hemodynamic variables at the microvascular muscle level7.
In recent years, sports professionals and researchers have used a wide range of commercial wearables equipped with NIRS technology to explore non&#8211;invasive muscular changes during exercise, providing the ability to determine VT1 and VT2 with this technology8. Thus, the integrative analysis of data from NIRS and CPET offers a comprehensive understanding of physiological responses to exercise.
The NIRS technology utilizes the modified Beer-Lambert law to quantify changes (D) in the concentrations of oxyhemoglobin (O2-Hb) and deoxyhemoglobin (H-Hb) during exercise7. At the local tissue level, a decrease in O2-Hb reflects an increase in local metabolic demand, while an increase in H-Hb reflects an increase in oxygen extraction. Total hemoglobin (tHb), the sum of O2-Hb and H-Hb, is used as an index of local tissue blood flow. Conversely, the difference between O2-Hb and H-Hb (Hbdiff) provides an index of tissue oxygen extraction9. The tissular saturation index (TSI), calculated as the ratio of O2-Hb to tHb, reflects the tissue oxygen saturation level and indicates the balance between local oxygen delivery and uptake10,11. Thus, NIRS data give critical insights into the physiological status at the microvascular level, providing a detailed understanding of tissue oxygenation and hemodynamics that complements the information obtained from CPET.
This detailed understanding provided by NIRS technology extends to many practical applications. Recent research highlights the versatility of NIRS and demonstrates its practical application in monitoring respiratory12,13 and locomotor muscles7, as well as brain regions involved in motor act ideation, such as the prefrontal cortex (PFC)14,15. This broad applicability underscores the ability of NIRS to provide comprehensive insight into physiological responses to various types of muscle contractions (concentric or, eccentric, or isometric contractions) and exercise.
By analyzing exercise-induced DTSI at both the muscular and cerebral levels, NIRS provides a valuable potential for identifying associations between peripheral and central limiting factors that affect the progression of exercise16,17. For example, among central limiting factors, decreased blood flow resulting from cerebral vasoconstriction caused by compensatory hyperventilation due to elevated hydrogen levels from anaerobic metabolism and increased blood lactate during high-intensity exercise is a significant contributor to the reduction in TSI in the prefrontal cortex17,18. In contrast, peripheral limiting factors are characterized by an imbalance between oxygen supply and demand in the exercising musculature19. Reduced local oxygen delivery and increased oxygen consumption can lead to tissue deoxygenation, as evidenced by decreased TSI20. This distinction highlights the multifaceted nature of performance limitations during high&#8211;intensity exercise, where both central and peripheral mechanisms are critical. This understanding suggests that delaying the onset of these limiting factors during exercise may contribute to improved athletic performance.
To fully leverage the potential of NIRS technology in identifying these limitations, standardized procedures are essential to ensure high-quality data collection and analysis. This document outlines methods for conducting maximal endurance exercise testing using NIRS technology to collect physiological data and elucidate the relationship between central and peripheral limiting factors during high-intensity exercise in endurance athletes. The proposed protocol provides a standardized approach to ensure consistency and accuracy in assessing the physiological phenomena underlying these limiting factors.

<table><tbody><tr><td>Column Scale</td><td>SECA</td><td>711</td><td>There are numerous alternatives to this item</td></tr><tr><td>Portable Stadiometer&amp;nbsp;</td><td>SECA</td><td>217</td><td>There are numerous alternatives to this item</td></tr><tr><td>12-lead ECG</td><td>COSMED</td><td>Quark T12x</td><td>A 12-lead ECG provides a better understanding of HR during exercise and facilitates the detection of arrhythmias.</td></tr><tr><td>Pulse Oxymeter</td><td>COSMED</td><td></td><td>Integrated pulse oxymeter</td></tr><tr><td>Ergoespirometer</td><td>COSMED</td><td>Quark-CPET</td><td>Calibration gases and calibration syringe are included</td></tr><tr><td>Cycle-ergometer</td><td>Ergoline GmH</td><td>ViaSprint 150P</td><td>There are numerous alternatives to this item. Must ensure compatibility with provided software</td></tr><tr><td>NIRS weareable</td><td>Artinis Medical Systems</td><td>Portalite</td><td>Articulated NIRS weareable fits the surface where it&#039;s placed upon.&amp;nbsp;</td></tr><tr><td>NIRS weareable</td><td>Artinis Medical Systems</td><td>Portamon</td><td>Portamon device provides better results on high adipose-tissue surfaces.</td></tr><tr><td>Metabolic Data Management Software (OMNIA)</td><td>COSMED</td><td></td><td>Software will vary upon system choice</td></tr><tr><td>NIRS Data Management Software (Oxysoft)</td><td>Artinis Medical Systems</td><td></td><td>Software will vary upon device choice</td></tr><tr><td>Wireless Probe Type Ultrasound Scanner</td><td>SONUS</td><td>Duo LC</td><td>There are numerous alternatives to this item</td></tr></tbody></table>

using near-infrared spectroscopy wearable devices to identify central versus peripheral limitations during exercise

The gold standard to assess the aerobic capacity in physically active subjects and athletes is the maximal oxygen consumption test (VO2&#8211;max), which involves analysis of exhaled&#8211;gases and cardiorespiratory variables obtained via the breath-by-breath method in an ergospirometer during an incremental exercise. However, this method cannot elucidate metabolic changes at the muscular level. Near-infrared spectroscopy (NIRS) has emerged as a valuable technology to evaluate local oxygen levels (Tissular Saturation Index, TSI) by quantifying the concentrations of oxygenated (O2-Hb) and deoxygenated (H-Hb) hemoglobin in the microvasculature of tissues. NIRS applications extend to respiratory and locomotor muscles, assessing metabolic changes associated with the cost of breathing (COB) and peripheral workload, respectively. Additionally, cerebral regions, such as the prefrontal cortex, have been explored with NIRS technology to assess physiological changes related to cognitive demand associated with planning or ideation of motor tasks linked to sports performance. Thus, by analyzing exercise-induced changes (D) in O2-Hb, H-Hb, and TSI, it is possible to identify central and peripheral exercise limitations, particularly when endurance training is the main component of physical fitness (e.g., running, cycling, triathlon, etc.). Addressing these factors is paramount for coaches and exercise physiologists to optimize athletic performance, incorporating training strategies focused on the primary exercise-limiting factors. This study outlines a protocol for utilizing wearables devices equipped with NIRS technology to analyze exercise changes in TSI, O2-Hb, and H-Hb, alongside cardiorespiratory variables typically registered in athletes during VO2&#8211;max tests. This approach offers a comprehensive method for identifying the primary systems involved in stopping exercise progression and sports performance improvement.

During the completion of a CPET, the symptoms of dyspnea, leg fatigue, and rate of perceived exertion (RPE) were reported in all subjects. The complementary use of the NIRS devices did not add any discomfort to the subjects&#39; sensation assessment. Also, we did not stop the CPET assessments by any risk event associated with excessive physiological stress.&#160; &#160;
We studied two competitive male cyclists recruited from a national cycling club. The inclusion criteria for this study were p...

This protocol integrates near-infrared spectroscopy (NIRS) technology to assess localized hematological and oxygenation changes at the prefrontal cortex, respiratory (m.Intercostales), and locomotor (m.Vastus Lateralis) muscles during cardiopulmonary exercise testing, enabling the identification of central and peripheral limiting factors affecting exercise performance.

Using Near-Infrared Spectroscopy Wearable Devices to Identify Central Versus Peripheral Limitations During Exercise

The gold standard to assess the aerobic capacity in physically active subjects and athletes is the maximal oxygen consumption test (VO2&#8211;max), which ...

using-near-infrared-spectroscopy-wearable-devices-to-identify-central

Research

JoVE Journal

Medicine

761 Views.  Pontificia Universidad Católica de Chile. Het doel is om te beoordelen of het gevoel van inspanningsprestaties te wijten is aan centrale of perifere determinanten. Proefpersonen reageren anders op levensvatbare omgevingsomstandigheden en opdringerige factoren. Dit zal gebeuren met behulp van een niet-invasieve methode.Dit is nabij-infraroodspectroscopie. De nieuwe studies op dit gebied van infraroodchirurgie, met behulp van nieuwe technologie, richten zich op het analyseren van hersenen en mas...

Video: Draagbare apparaten met nabij-infraroodspectroscopie gebruiken om centrale versus perifere beperkingen tijdens het sporten te identificeren

In vivo Near Infrared Fluorescence (NIRF) Intravascular Molecular Imaging of Inflammatory Plaque, a Multimodal Approach to Imaging of Atherosclerosis

The vascular response to injury is a well-orchestrated inflammatory response triggered by the accumulation of macrophages within the vessel wall leading to an accumulation of lipid-laden intra-luminal plaque, smooth muscle cell proliferation and progressive narrowing of the vessel lumen. The formation of such vulnerable plaques prone to rupture underlies the majority of cases of acute myocardial infarction. The complex molecular and cellular inflammatory cascade is orchestrated by the recruitment of T lymphocytes and macrophages and their paracrine effects on endothelial and smooth muscle cells.1
Molecular imaging in atherosclerosis has evolved into an important clinical and research tool that allows in vivo visualization of inflammation and other biological processes. Several recent examples demonstrate the ability to detect high-risk plaques in patients, and assess the effects of pharmacotherapeutics in atherosclerosis.4 While a number of molecular imaging approaches (in particular MRI and PET) can image biological aspects of large vessels such as the carotid arteries, scant options exist for imaging of coronary arteries.2 The advent of high-resolution optical imaging strategies, in particular near-infrared fluorescence (NIRF), coupled with activatable fluorescent probes, have enhanced sensitivity and led to the development of new intravascular strategies to improve biological imaging of human coronary atherosclerosis.
Near infrared fluorescence (NIRF) molecular imaging utilizes excitation light with a defined band width (650-900 nm) as a source of photons that, when delivered to an optical contrast agent or fluorescent probe, emits fluorescence in the NIR window that can be detected using an appropriate emission filter and a high sensitivity charge-coupled camera. As opposed to visible light, NIR light penetrates deeply into tissue, is markedly less attenuated by endogenous photon absorbers such as hemoglobin, lipid and water, and enables high target-to-background ratios due to reduced autofluorescence in the NIR window. Imaging within the NIR 'window' can substantially improve the potential for in vivo imaging.2,5
Inflammatory cysteine proteases have been well studied using activatable NIRF probes10, and play important roles in atherogenesis. Via degradation of the extracellular matrix, cysteine proteases contribute importantly to the progression and complications of atherosclerosis8. In particular, the cysteine protease, cathepsin B, is highly expressed and colocalizes with macrophages in experimental murine, rabbit, and human atheromata.3,6,7 In addition, cathepsin B activity in plaques can be sensed in vivo utilizing a previously described 1-D intravascular near-infrared fluorescence technology6, in conjunction with an injectable nanosensor agent that consists of a poly-lysine polymer backbone derivatized with multiple NIR fluorochromes (VM110/Prosense750, ex/em 750/780nm, VisEn Medical, Woburn, MA) that results in strong intramolecular quenching at baseline.10 Following targeted enzymatic cleavage by cysteine proteases such as cathepsin B (known to colocalize with plaque macrophages), the fluorochromes separate, resulting in substantial amplification of the NIRF signal. Intravascular detection of NIR fluorescence signal by the utilized novel 2D intravascular NIRF catheter now enables high-resolution, geometrically accurate in vivo detection of cathepsin B activity in inflamed plaque.
In vivo molecular imaging of atherosclerosis using catheter-based 2D NIRF imaging, as opposed to a prior 1-D spectroscopic approach,6 is a novel and promising tool that utilizes augmented protease activity in macrophage-rich plaque to detect vascular inflammation.11,12 The following research protocol describes the use of an intravascular 2-dimensional NIRF catheter to image and characterize plaque structure utilizing key aspects of plaque biology. It is a translatable platform that when integrated with existing clinical imaging technologies including angiography and intravascular ultrasound (IVUS), offers a unique and novel integrated multimodal molecular imaging technique that distinguishes inflammatory atheromata, and allows detection of intravascular NIRF signals in human-sized coronary arteries.

In vivo Near Infrared Fluorescence NIRF Intravascular Molecular Imaging of Inflammatory Plaque, a Multimodal Approach to Imaging of Atherosclerosis

We detail a new near-infrared fluorescence (NIRF) catheter for 2-dimensional intravascular molecular imaging of plaque biology in vivo. The NIRF catheter can visualize key biological processes such as inflammation by reporting on the presence of plaque-avid activatable and targeted NIR fluorochromes. The catheter utilizes clinical engineering and power requirements and is targeted for application in human coronary arteries. The following research study describes a multimodal imaging strategy that utilizes a novel in vivo intravascular NIRF catheter to image and quantify inflammatory plaque in proteolytically active inflamed rabbit atheromata.

The vascular response to injury is a well-orchestrated inflammatory response triggered by the accumulation of macrophages within the vessel wall leading ...

Functional Near Infrared Spectroscopy of the Sensory and Motor Brain Regions with Simultaneous Kinematic and EMG Monitoring During Motor Tasks

There are several advantages that functional near-infrared spectroscopy (fNIRS) presents in the study of the neural control of human movement. It is relatively flexible with respect to participant positioning and allows for some head movements during tasks. Additionally, it is inexpensive, light weight, and portable, with very few contraindications to its use. This presents a unique opportunity to study functional brain activity during motor tasks in individuals who are typically developing, as well as those with movement disorders, such as cerebral palsy. An additional consideration when studying movement disorders, however, is the quality of actual movements performed and the potential for additional, unintended movements. Therefore, concurrent monitoring of both blood flow changes in the brain and actual movements of the body during testing is required for appropriate interpretation of fNIRS results. Here, we show a protocol for the combination of fNIRS with muscle and kinematic monitoring during motor tasks. We explore gait, a unilateral multi-joint movement (cycling), and two unilateral single-joint movements (isolated ankle dorsiflexion, and isolated hand squeezing). The techniques presented can be useful in studying both typical and atypical motor control, and can be modified to investigate a broad range of tasks and scientific questions.

Monitoring brain activity during upright motor tasks is of great value when investigating the neural source of movement disorders. Here, we demonstrate a protocol that combines functional near infrared spectroscopy with continuous monitoring of muscle and kinematic activity during 4 types of motor tasks.

There are several advantages that functional near-infrared spectroscopy (fNIRS) presents in the study of the neural control of human movement. It is ...

Behavior

Using Fiberless, Wearable fNIRS to Monitor Brain Activity in Real-world Cognitive Tasks

Functional Near Infrared Spectroscopy (fNIRS) is a neuroimaging technique that uses near-infrared light to monitor brain activity. Based on neurovascular coupling, fNIRS is able to measure the haemoglobin concentration changes secondary to neuronal activity. Compared to other neuroimaging techniques, fNIRS represents a good compromise in terms of spatial and temporal resolution. Moreover, it is portable, lightweight, less sensitive to motion artifacts and does not impose significant physical restraints. It is therefore appropriate to monitor a wide range of cognitive tasks (e.g., auditory, gait analysis, social interaction) and different age populations (e.g., new-borns, adults, elderly people). The recent development of fiberless fNIRS devices has opened the way to new applications in neuroscience research. This represents a unique opportunity to study functional activity during real-world tests, which can be more sensitive and accurate in assessing cognitive function and dysfunction than lab-based tests. This study explored the use of fiberless fNIRS to monitor brain activity during a real-world prospective memory task. This protocol is performed outside the lab and brain haemoglobin concentration changes are continuously measured over the prefrontal cortex while the subject walks around in order to accomplish several different tasks.

Monitoring brain activity outside the lab without physical constraints presents methodological challenges. A fiberless, wearable functional Near Infrared Spectroscopy (fNIRS) system was used to measure brain activity during an ecological prospective memory task. It was demonstrated that this system could be used to monitor brain activity during non-lab based experiments.

Functional Near Infrared Spectroscopy (fNIRS) is a neuroimaging technique that uses near-infrared light to monitor brain activity. Based on neurovascular ...

Near Infrared Optical Projection Tomography for Assessments of &beta;-cell Mass Distribution in Diabetes Research

By adapting OPT to include the capability of imaging in the near infrared (NIR) spectrum, we here illustrate the possibility to image larger bodies of pancreatic tissue, such as the rat pancreas, and to increase the number of channels (cell types) that may be studied in a single specimen. We further describe the implementation of a number of computational tools that provide: 1/ accurate positioning of a specimen's (in our case the pancreas) centre of mass (COM) at the axis of rotation (AR)2; 2/ improved algorithms for post-alignment tuning which prevents geometric distortions during the tomographic reconstruction2 and 3/ a protocol for intensity equalization to increase signal to noise ratios in OPT-based BCM determinations3. In addition, we describe a sample holder that minimizes the risk for unintentional movements of the specimen during image acquisition. Together, these protocols enable assessments of BCM distribution and other features, to be performed throughout the volume of intact pancreata or other organs (e.g. in studies of islet transplantation), with a resolution down to the level of individual islets of Langerhans.

Near Infrared Optical Projection Tomography for Assessments of &#946;-cell Mass Distribution in Diabetes Research

We describe the adaptation of optical projection tomography (OPT)1 to imaging in the near infrared spectrum, and the implementation of a number of computational tools. These protocols enable assessments of pancreatic &beta;-cell mass (BCM) in larger specimens, increase the multichannel capacity of the technique and increase the quality of OPT data.

By adapting OPT to include the capability of imaging in the near infrared (NIR) spectrum, we here illustrate the possibility to image larger bodies of ...

Using Continuous Data Tracking Technology to Study Exercise Adherence in Pulmonary Rehabilitation

Pulmonary rehabilitation (PR) is an important component in the management of respiratory diseases. The effectiveness of PR is dependent upon adherence to exercise training recommendations. The study of exercise adherence is thus a key step towards the optimization of PR programs. To date, mostly indirect measures, such as rates of participation, completion, and attendance, have been used to determine adherence to PR. The purpose of the present protocol is to describe how continuous data tracking technology can be used to measure adherence to a prescribed aerobic training intensity on a second-by-second basis.
In our investigations, adherence has been defined as the percent time spent within a specified target heart rate range. As such, using a combination of hardware and software, heart rate is measured, tracked, and recorded during cycling second-by-second for each participant, for each exercise session. Using statistical software, the data is subsequently extracted and analyzed. The same protocol can be applied to determine adherence to other measures of exercise intensity, such as time spent at a specified wattage, level, or speed on the cycle ergometer. Furthermore, the hardware and software is also available to measure adherence to other modes of training, such as the treadmill, elliptical, stepper, and arm ergometer. The present protocol, therefore, has a vast applicability to directly measure adherence to aerobic exercise.

Pulmonary rehabilitation is widely recognized in the management of respiratory diseases. A key component to successful pulmonary rehabilitation is adherence to the recommended exercise training. The purpose of the present protocol is to describe how continuous data tracking technology can be used to precisely measure adherence to a prescribed aerobic training intensity.

Pulmonary rehabilitation (PR) is an important component in the management of respiratory diseases. The effectiveness of PR is dependent upon adherence to ...

Skeletal Muscle Neurovascular Coupling, Oxidative Capacity, and Microvascular Function with 'One Stop Shop' Near-infrared Spectroscopy

Exercise represents a major hemodynamic stress that demands a highly coordinated neurovascular response in order to match oxygen delivery to metabolic demand. Reactive hyperemia (in response to a brief period of tissue ischemia) is an independent predictor of cardiovascular events and provides important insight into vascular health and vasodilatory capacity. Skeletal muscle oxidative capacity is equally important in health and disease, as it determines the energy supply for myocellular processes. Here, we describe a simple, non-invasive approach using near-infrared spectroscopy to assess each of these major clinical endpoints (reactive hyperemia, neurovascular coupling, and muscle oxidative capacity) during a single clinic or laboratory visit. Unlike Doppler ultrasound, magnetic resonance images/spectroscopy, or invasive catheter-based flow measurements or muscle biopsies, our approach is less operator-dependent, low-cost, and completely non-invasive. Representative data from our lab taken together with summary data from previously published literature illustrate the utility of each of these end-points. Once this technique is mastered, application to clinical populations will provide important mechanistic insight into exercise intolerance and cardiovascular dysfunction.

Here, we describe a simple, non-invasive approach using near-infrared spectroscopy to assess reactive hyperemia, neurovascular coupling and skeletal muscle oxidative capacity in a single clinic or laboratory visit.

Exercise represents a major hemodynamic stress that demands a highly coordinated neurovascular response in order to match oxygen delivery to metabolic ...

Qualitative and Comparative Cortical Activity Data Analyses from a Functional Near-Infrared Spectroscopy Experiment Applying Block Design

Neuroimaging studies play a pivotal role in the evaluation of pre- vs. post-interventional neurological conditions such as in rehabilitation and surgical treatment. Among the many neuroimaging technologies used to measure brain activity, functional near-infrared spectroscopy (fNIRS) enables the evaluation of dynamic cortical activities by measuring the local hemoglobin levels similar to functional magnetic resonance imaging (fMRI). Also, due to lesser physical restriction in fNIRS, multiple variants of sensorimotor tasks can be evaluated. Many laboratories have developed several methods for fNIRS data analysis; however, despite the fact that the general principles are the same, there is no universally standardized method. Here, we present the qualitative and comparative analytic methods of data obtained from a multi-channel fNIRS experiment using a block design. For qualitative analysis, we used a software for NIRS as a mass-univariate approach based on the generalized linear model. The NIRS-SPM analysis shows qualitative results for each session by visualizing the activated area during the task. In addition, the non-invasive three-dimensional digitizer can be used to estimate the fNIRS channel locations relative to the brain. To corroborate the NIRS-SPM findings, the amplitude of the changes in hemoglobin levels induced by the sensorimotor task can be statistically analyzed by comparing the data obtained from two different sessions (before and after intervention) of the same study subject using a multi-channel hierarchical mixed model. Our methods can be used to measure the pre- vs. post-intervention analysis in a variety of neurological disorders such as movement disorders, cerebrovascular diseases, and neuropsychiatric disorders.

We describe the analysis of continuous-wave functional near-infrared spectroscopy experiment using a block design with a sensorimotor task. To increase the reliability of the data analysis, we used the qualitative general linear model-based statistical parametric mapping and the comparative hierarchical mixed models for multi-channels.

Neuroimaging studies play a pivotal role in the evaluation of pre- vs. post-interventional neurological conditions such as in rehabilitation and surgical ...

Neuroscience

Integration of Brain Tissue Saturation Monitoring in Cardiopulmonary Exercise Testing in Patients with Heart Failure

Cerebral hypo-oxygenation during rest or exercise negatively impacts the exercise capacity of patients with heart failure with reduced ejection fraction (HF). However, in clinical cardiopulmonary exercise testing (CPET), cerebral hemodynamics is not assessed. NIRS is used to measure cerebral tissue oxygen saturation (SctO2) in the frontal lobe. This method is reliable and valid and has been utilized in several studies. SctO2 is lower during both rest and peak exercise in patients with HF than in healthy controls (66.3 &#177; 13.3% and 63.4 &#177; 13.8% vs. 73.1 &#177; 2.8% and 72 &#177; 3.2%). SctO2 at rest is significantly linearly correlated with peak VO2 (r = 0.602), oxygen uptake efficiency slope (r = 0.501), and brain natriuretic peptide (r = -0.492), all of which are recognized prognostic and disease severity markers, indicating its potential prognostic value. SctO2 is determined mainly by end-tidal CO2 pressure, mean arterial pressure, and hemoglobin in the HF population. This article demonstrates a protocol that integrates SctO2 using NIRS into incremental CPET on a calibrated bicycle ergometer.

This protocol integrated near-infrared spectroscopy into conventional cardiopulmonary exercise testing to identify the involvement of the cerebral hemodynamic response in exercise intolerance in patients with heart failure.

Cerebral hypo-oxygenation during rest or exercise negatively impacts the exercise capacity of patients with heart failure with reduced ejection fraction ...

Non-Invasive Monitoring of Microvascular Oxygenation and Reactive Hyperemia using Hybrid, Near-Infrared Diffuse Optical Spectroscopy for Critical Care

The detection of levels of impairment in microvascular oxygen consumption and reactive hyperemia is vital in critical care. However, there are no practical means for a robust and quantitative evaluation. This paper describes a protocol to evaluate these impairments using a hybrid near-infrared diffuse optical device. The device contains modules for near-infrared time-resolved and diffuse correlation spectroscopies and pulse-oximetry. These modules allow the non-invasive, continuous, and real-time measurement of the absolute, microvascular blood/tissue oxygen saturation (StO2) and the blood flow index (BFI) along with the peripheral arterial oxygen saturation (SpO2). This device uses an integrated, computer-controlled tourniquet system to execute a standardized protocol with optical data acquisition from the brachioradialis muscle. The standardized vascular occlusion test (VOT) takes care of the variations in the occlusion duration and pressure reported in the literature, while the automation minimizes inter-operator differences. The protocol we describe focuses on a 3-min occlusion period but the details described in this paper can readily be adapted to other durations and cuff pressures, as well as other muscles. The inclusion of an extended baseline and post-occlusion recovery period measurement allows the quantification of the baseline values for all the parameters and the blood/tissue deoxygenation rate that corresponds to the metabolic rate of oxygen consumption. Once the cuff is released, we characterize the tissue reoxygenation rate, magnitude, and duration of the hyperemic response in BFI and StO2. These latter parameters correspond to the quantification of the reactive hyperemia, which provides information about the endothelial function. Furthermore, the above-mentioned measurements of the absolute concentration of oxygenated and deoxygenated hemoglobin, BFI, the derived metabolic rate of oxygen consumption, StO2, and SpO2 provide a yet-to-be-explored rich data set that can exhibit disease severity, personalized therapeutics, and management interventions.

We describe a protocol to non-invasively and continuously measure absolute microvascular blood flow index and blood oxygen saturation using a multi-modal device based on near-infrared diffuse optics. We then evaluate the metabolic rate of oxygen consumption and reactive hyperemia utilizing a vascular occlusion test.

The detection of levels of impairment in microvascular oxygen consumption and reactive hyperemia is vital in critical care. However, there are no ...

Optimizing NIRS for Assessing Lower Limb Vascular Function

Near-Infrared Spectroscopy During Reactive Hyperemia for the Assessment of Lower Limb Vascular Function

Vascular diseases of the lower limb contribute substantially to the&#160;global burden of cardiovascular disease and comorbidities such as diabetes. Importantly, microvascular dysfunction can occur prior to, or alongside, macrovascular pathology, and both potentially contribute to patient symptoms and disease burden. Here, we describe a non-invasive approach using near-infrared spectroscopy (NIRS) during reactive hyperemia, which provides a standardized assessment of lower limb vascular (dys)function and a potential method to evaluate the efficacy of therapeutic interventions. Unlike alternative methods, such as contrast-enhanced ultrasound, this approach does not require venous access or sophisticated image analysis, and it is inexpensive and less operator-dependent. This description of the NIRS method includes representative results and standard terminology alongside the discussion of measurement considerations, limitations, and alternative methods. Future application of this work will improve standardization of vascular research design, data collection procedures, and harmonized reporting, thereby enhancing translational research outcomes in the areas of lower limb vascular (dys)function, disease, and treatment.

Author Spotlight: Enhancing Vascular Function and Physical Capacity in Cardiovascular Disease Through Novel Interventions and NIRS Technology

Here, we describe a non-invasive approach using near-infrared spectroscopy to assess reactive hyperemia in the lower limb. This protocol provides a standardized assessment of vascular and microvascular responsiveness that may be used to determine the presence of vascular dysfunction as well as the efficacy of therapeutic interventions.

Vascular diseases of the lower limb contribute substantially to the&#160;global burden of cardiovascular disease and comorbidities such as diabetes. ...

Using Near-Infrared Spectroscopy Wearable Devices to Identify Central Versus Peripheral Limitations During Exercise

Samenvatting

Meer video's verkennen