Comparison of analysis strategies to assess sex differences in microvascular reperfusion using near-infrared spectroscopy.

The near-infrared spectroscopy (NIRS) vascular occlusion test (VOT) assesses microvascular reperfusion. Two strategies have been used to quantify reperfusion following reactive hyperemia, but it is unclear whether both yield similar results when comparing biological sex. This study aimed to determine whether sex differences in NIRS-based microvascular reperfusion are similarly apparent using the 10-s reactive hyperemia slope of the tissue saturation index (StO2) signal (slope 2) and the halftime to maximal reperfusion (T ½). Healthy, recreationally active males (n = 31) and females (n = 31) between 18 and 82 years took part in this study. A NIRS VOT was performed on the tibialis anterior muscle, and reperfusion was quantified using slope 2 (% s-1) and T ½ (s). Adipose tissue thickness (ATT) was higher in females (P = 0.009), which was associated with a lower StO2 (P = 0.001) and oxygenated hemoglobin (O2Hb) (P = 0.05) signal range. The StO2 slope 2 was significantly steeper in males versus females (P = 0.001) but not after correcting for ATT (P = 0.295). There were no sex differences in StO2 T ½ (P = 0.067) or O2Hb T ½ (P = 0.197). In a subset of males (n = 26) and females (n = 21) with similar ATT, there were no sex differences in StO2 slope 2 (P = 0.068), StO2 T ½ (P = 0.491), or O2Hb T ½ (P = 0.899). An ATT-corrected StO2 slope 2 or the T ½ approach is recommended for analysis of NIRS-based microvascular reperfusion when differences in ATT are present between sexes.NEW & NOTEWORTHY Sex differences in near-infrared spectroscopy (NIRS)-based microvascular reperfusion have been previously reported. We found that greater adipose tissue thickness in females reduces kinetic measures of NIRS-based microvascular reperfusion. Sex differences are eliminated when performing an adipose tissue thickness correction, when the NIRS signal range is accounted for, or when adipose tissue thickness is similar between sexes. This highlights the importance of considering factors that affect NIRS signals, such as adipose tissue thickness, when drawing comparisons between groups.

Muscle Mitochondrial Capacity Is Impaired Immediately Following Maximal Exercise.

PURPOSE: This study measured the time course mVO2max following both maximal and submaximal exercise. METHODS: Healthy male and female participants were tested (n = 12 maximal and n = 8 submaximal exercise). A NIRS device was placed on the left medial gastrocnemius. Participants performed either one minute of maximal, rapid (~2 Hz), or submaximal (~0.37 Hz) plantar flexion exercise on a custom pneumatic ergometer. mVO2max was measured before and immediately after exercise. mVO2max measurements consisted of four incomplete recovery curves of muscle metabolism taken after 30 seconds of electrical muscle stimulation except in the first post-exercise trial. The four recovery curves were collected 50-, 156-, 260-, and 366-seconds post-exercise, each producing a mVO2max rate constant. RESULTS: After maximal exercise muscle acceleration decreased to 52 + 18% (p = 0.001) of pre-values. mVO2max was reduced from the pre-exercise mean at the first post-trial (2.16 + 0.44 min-1 to 1.21 + 0.52 min -1, p < 0.001). The fourth trial showed recovery from the first (2.2 + 0.46 min-1 vs 1.21 + 0.52 min-1, p < 0.001) and was not significantly different from pre-exercise values (2.2 + 0.46 min-1 vs 2.16 + 0.44 min-1, p = 0.41). No change in acceleration or mVO2max was seen after submaximal exercise (p > 0.05). CONCLUSIONS: The 56.7% reduction in mVO2max supports the hypothesis that in young, healthy individuals a minute of maximal exercise transiently impairs mVO2max which then recovers within six minutes. The NIRS method shows promise in tracking time course changes in mVO2max and warrants further investigation of the transient effects of exercise on mVO2max.

Elevated blood pressure in children with cerebral palsy and its relationship with adiposity and physical activity.

BACKGROUND: There is a high prevalance of hypertension in adults with with cerebral palsy (CP). However, less is known about blood pressure in children with CP. OBJECTIVE: The aim was to determine if blood pressure is elevated in children with CP and whether it is related to adiposity and physical activity. METHODS: Thirty children with spastic CP (5-11 y) and 30 age-, sex-, and race-matched typically developing control children were studied. Resting systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate were measured, and mean arterial pressure (MAP) was calculated. Visceral fat mass and total body fat mass index (FMI) were determined using dual-energy X-ray absorptiometry. Physical activity was assessed using accelerometer-based monitors. RESULTS: Children with CP had higher DBP and heart rate than controls (p < 0.05). DBP percentile and MAP were also higher in children with CP when BMI was statistically controlled. Children with CP and elevated blood pressure or hypertension (n = 8) had 56% more visceral fat mass than children with CP and normal blood pressure (n = 22; p < 0.05). In the groups combined, blood pressure was directly related to visceral fat mass and FMI, and inversely related to physical activity (p < 0.05). However, in children with CP alone, only visceral fat mass was related to blood pressure (p < 0.05). CONCLUSIONS: Children with CP have higher resting blood pressure than typically developing children. The higher blood pressure is related to higher visceral adiposity. Careful blood pressure screening should start during childhood in individuals with CP.

Validation of scores from a telephone administered multiple sclerosis walking scale-12 in persons with multiple sclerosis.

BACKGROUND: The Multiple Sclerosis Walking Scale-12 (MSWS-12) has typically been delivered through paper-and-pencil or computer-based administration. PURPOSE: This study examined the validity of inferences from scores derived via a telephone administration of the MSWS-12 applied as part of screening of participants with walking dysfunction into a clinical trial of exercise training in MS. METHOD: The MSWS-12 was administered on two occasions separated by approximately 2 weeks through the telephone and then in-person (i.e., computer-based administration). Participants further completed the Patient Determined Disease Steps (PDDS) scale, timed 25-foot walk (T25FW), six-minute walk (6MW), Modified Fatigue Impact Scale (MFIS), and Multiple Sclerosis Impact Scale-29 (MSIS-29), and underwent a neurological exam for generating an expanded disability status scale (EDSS) score. The primary set of data (Full Sample) for analyses included all persons who passed the telephone screening for inclusion with MSWS-12 scores between 25 and 75 (N = 374). The secondary set of data (Truncated Sample) included only persons with MSWS-12 scores between 25 and 75 for both the telephone and computer administrations of the MSWS-12 (N = 248). RESULTS: The results in the Full Sample indicated a difference in overall and item levels scores between the telephone and computer data collections, and the computer version had higher internal consistency and stronger unidimensionality. Nevertheless, MSWS-12 scores from both modes of administration had comparable correlations with the T25FW, 6MW, EDSS, PDDS, MFIS, and MSIS-29, but the correlation between the two MSWS-12 administrations did not approach unity. There was a systematic difference in scores between telephone and computer administrations across levels of walking dysfunction based on a Bland-Altman plot, and the difference was predicted by MFIS physical, 6MW, and EDSS scores. The comparison of results between the Full and Truncated Samples suggested that the primary analysis might have been influenced by the larger range of scores on the computer than telephone administrations of the MSWS-12. CONCLUSION: The telephone administration of the MSWS-12 provides an efficient and cost-effective measure of walking dysfunction in persons with MS.

A systematic review of the relationship between muscle oxygen dynamics and energy rich phosphates. Can NIRS help?

BACKGROUND: Phosphocreatine dynamics provide the gold standard evaluation of in-vivo mitochondrial function and is tightly coupled with oxygen availability. Low mitochondrial oxidative capacity has been associated with health issues and low exercise performance. METHODS: To evaluate the relationship between near-infrared spectroscopy-based muscle oxygen dynamics and magnetic resonance spectroscopy-based energy-rich phosphates, a systematic review of the literature related to muscle oxygen dynamics and energy-rich phosphates was conducted. PRISMA guidelines were followed to perform a comprehensive and systematic search of four databases on 02-11-2021 (PubMed, MEDLINE, Scopus and Web of Science). Beforehand pre-registration with the Open Science Framework was performed. Studies had to include healthy humans aged 18-55, measures related to NIRS-based muscle oxygen measures in combination with energy-rich phosphates. Exclusion criteria were clinical populations, laboratory animals, acutely injured subjects, data that only assessed oxygen dynamics or energy-rich phosphates, or grey literature. The Effective Public Health Practice Project Quality Assessment Tool was used to assess methodological quality, and data extraction was presented in a table. RESULTS: Out of 1483 records, 28 were eligible. All included studies were rated moderate. The studies suggest muscle oxygen dynamics could indicate energy-rich phosphates under appropriate protocol settings. CONCLUSION: Arterial occlusion and exercise intensity might be important factors to control if NIRS application should be used to examine energetics. However, more research needs to be conducted without arterial occlusion and with high-intensity exercises to support the applicability of NIRS and provide an agreement level in the concurrent course of muscle oxygen kinetics and muscle energetics. TRIAL REGISTRATION: https://osf.io/py32n/ . KEY POINTS: 1. NIRS derived measures of muscle oxygenation agree with gold-standard measures of high energy phosphates when assessed in an appropriate protocol setting. 2. At rest when applying the AO protocol, in the absence of muscle activity, an initial disjunction between the NIRS signal and high energy phosphates can been seen, suggesting a cascading relationship. 3. During exercise and recovery a disruption of oxygen delivery is required to provide the appropriate setting for evaluation through either an AO protocol or high intensity contractions.

Investigating Relationships Among Interoceptive Awareness, Emotional Susceptibility, and Fatigue in Persons With Multiple Sclerosis.

BACKGROUND: Fatigue is a particularly debilitating symptom for people with multiple sclerosis (MS). Although personality traits and MS have been studied, interoception and emotional susceptibility and their links to fatigue have not yet been explored. METHODS: Study participants provided demographic information and completed standardized patient-reported outcomes of walking function, physical activity, subjective fatigue, interoceptive awareness, and emotional susceptibility. A subset of participants participated in semistructured interviews discussing fatigue, body sensations, emotions, and their effects on exercise. Quantitative data were analyzed using multiple regression. Qualitative data were analyzed using thematic analysis. RESULTS: Mean ± SD Fatigue Severity Scale scores (5.0 ± 1.3) indicated that fatigue was a problematic symptom. Mean ± SD Multidimensional Assessment of Interoceptive Awareness, Version 2 (2.8 ± 0.6) and Emotional Susceptibility Scale (3.0 ± 1.0) scores indicated lower levels of interoceptive awareness and emotional susceptibility. Quantitative data indicated no relationship between fatigue and interoceptive awareness (ß = -0.20; P = .88) and emotional susceptibility (ß = 0.03; P = .83), and neither were these related to physical activity (ß = -0.07; P = .64). Qualitative themes indicated strong fatigue experiences involving the whole body and individual limbs, anger and frustration, and effects on physical activity. CONCLUSIONS: Physically active people with MS report strong sensations of fatigue closely linked to frustration and helplessness. There was agreement between qualitative and quantitative assessments of fatigue but dissonance regarding interoceptive awareness and physical activity. The practice of clinicians, particularly those involved with facilitating or planning physical activity for persons with MS, would benefit from these findings about fatigue.

Evaluation of inter-rater and test-retest reliability for near-infrared spectroscopy reactive hyperemia measures.

BACKGROUND: Near-infrared spectroscopy (NIRS) is a non-invasive tool used to measure blood flow in peripheral tissues. More information on inter-rater agreement and test-retest reliability of NIRS-based reperfusion assessments is needed. PURPOSE: To assess inter-rater agreement for NIRS based data analysis, and evaluate the measurement's reliability across days. METHODS: On three separate days (average days between visits 1 and 3: 19.4 ± 6.9 days), participants' (N = 15 males, 22 ± 2 yr.) post-occlusion reactive hyperemia (PORH) was measured in the left gastrocnemius muscle using Continuous-Wave NIRS (CW-NIRS). A blood pressure cuff was placed proximal to the knee and inflated to occlude lower leg blood flow for 5 min. The following CW-NIRS parameters were selected: (1) percent saturation in HbO2 (StO2%) at baseline; (2) the O2Hb range used to normalize the NIRS signal; (3) the time for the O2Hb signal to reach 50 % peak post-occlusion hyperemia (T1/2), and (4) the post peak hyperemic O2Hb recovery slope (O2REC-SLP). Absolute agreement between the two analysts was calculated using two-way random effects Intraclass Correlation Coefficients (ICC2,1). Consistency between analysts and across days was calculated using two-way mixed models (ICC3,1). Mean and 95 % confidence intervals (CI) of ICCs are reported. Coefficient of variation (CV) and standard error of the measurement (SEM) are reported. RESULTS: The ICC2,1 data indicated "adequate" to "excellent" absolute agreement between the two NIRS analysts. ICC2,3 data indicated "adequate" to "good" reliability across visits. The CV and SEM for rater 1 and rater 2 across visit were StO2 (CV: 3.79 % ± 2.71 % and 4.50 % ± 2.37 %; SEM: 3.42 and 3.82), O2Hb range (CV: 10.50 ± 5.93 and 12.79 ± 12.41; SEM: 3.26 and 4.71), T1/2 (CV: 11.15 % ± 5.52 % and 10.96 % ± 4.50; SEM: 1.22 and 1.11), and O2REC-SLP (CV: 19.49 % ± 9.99 % and 18.45 % ± 9.48 %; SEM: 0.04 and 0.04). CONCLUSION: It is concluded that NIRS parameters assessed show adequate reliability between analysts and across three visits. It is recommended, when feasible and because of the absence of 100 % reliability, that investigators employ more than one rater for scoring at least a portion of the data across each trial in a study's control condition in order to have the ability to estimate the magnitude of error attributable to imperfect reliability.

Skeletal Muscle Dysfunction in People With Multiple Sclerosis: A Physiological Target for Improving Physical Function and Mobility.

Impaired mobility is amongst the most debilitating symptoms reported by people with multiple sclerosis (MS). Historically, it has been viewed that walking impairments in people with MS are directly caused by the physical damage to the neurons in the central nervous system (CNS) which results from the immunopathology of MS. However, research from over the past 4 decades has revealed that physical function in people with MS is also affected by skeletal muscle dysfunction characterized by a reduced capacity to produce, regulate, and sustain the force-generating muscle contractions that propel human movement. While the immediate CNS damage caused by MS can alter the neural activation of muscle by disrupting neuromotor transmission, chronic reductions in mobility and extreme fatigue can lead to physically inactive lifestyles that negatively affect skeletal muscle through mechanisms of deconditioning. Consequently, people with MS can experience alterations in activation patterns, muscle mass and tissue composition, contractility, metabolism, and perfusion that contribute to reductions in muscle function that ultimately impair key physical functions such as walking. This article provides an overview of the cellular mechanisms that contribute to skeletal muscle dysfunction in people with MS and a discussion of the current evidence suggesting that skeletal muscle may be a key physiological target for interventions aiming to improve mobility in this population. We specifically highlight recent evidence demonstrating the potential for rehabilitation and exercise interventions to induce muscle plasticity in people with MS who have moderate to severe levels of disability. In conclusion, we discuss future directions in basic science and clinical research that may advance our understanding of muscle dysfunction in MS and lead to the development of more precise and effective treatment strategies.

The role of worry in exercise and physical activity behavior of people with multiple sclerosis.

Purpose: This study is a secondary analysis of data from a mixed methods exploration of fatigue in people with multiple sclerosis (MS), a chronic autoimmune disease affecting the central nervous system. During initial analysis, worry emerged during discussions of the fatigue experience. The purpose of this study is to explore worry in relationship to exercise and physical activity behavior. Methods: Mixed methods were used to address the research question. 55 people with MS provided demographic and survey data (habitual physical activity, body perception, functioning). 35 participated in semi-structured interviews on the topics of fatigue, body sensations, emotions, and their effects on physical activity. Qualitative data were analyzed utilizing constructivist grounded theory. Quantitative data were analyzed utilizing multiple regression. Results: Qualitative theory described participants' thoughts and experiences regarding the consequences of fatigue during activity, and how they appear to influence subsequent actions. Worry played a critical role in thought processes regarding physical activity. Aspects of body perception were weak quantitative predictors of physical activity behavior after control of physical functionality. Conclusions: The most significant finding of this study was the description and dialogue about worry as a factor that shapes perceptions of the benefits and value of exercise and physical activity. Physical activity practitioners could benefit from seeking to understand physical-activity-related worry when examining physical activity behavior and designing programming.

Lessons learned from clinical trials of exercise and physical activity in people with MS - guidance for improving the quality of future research.

The body of research on exercise and physical activity among persons with multiple sclerosis(MS) has expanded rapidly in quantity, but not necessarily quality, over the past 20+ years. There is evidence for beneficial effects of exercise and physical activity on immune cells and neurotrophic factors, brain structure and function, walking and cognitive performance, fatigue, depression, and pain, and quality of life among persons with MS. Nevertheless, there is heterogeneity in the outcomes of exercise and physical activity, and a recognition of substantial challenges for improving the effectiveness of those behaviors in MS. To move the field forward, members of the National MS Society physical wellness research working-group pooled collective experiences for identifying challenges, logistic complexities, and opportunities for researchers in designing and conducting interventions of exercise and physical activity among persons with MS. We examined the scope of our experiences and identified collective "lessons learned" regarding the behaviors themselves; study design features and stage of research; study setting, safety, and sample selection; and implementation of randomized controlled trials(RCTs) and treatment fidelity. This paper provides a resource that can inform researchers, particularly new investigators or established investigators transitioning into MS, on conducting high-quality RCTs on exercise and physical activity in MS.

Is Sleep Disordered Breathing Confounding Rehabilitation Outcomes in Spinal Cord Injury Research?

The purpose of this article is to highlight the importance of considering sleep-disordered breathing (SDB) as a potential confounder to rehabilitation research interventions in spinal cord injury (SCI). SDB is highly prevalent in SCI, with increased prevalence in individuals with higher and more severe lesions, and the criterion standard treatment with continuous positive airway pressure remains problematic. Despite its high prevalence, SDB is often untested and untreated in individuals with SCI. In individuals without SCI, SDB is known to negatively affect physical function and many of the physiological systems that negatively affect physical rehabilitation in SCI. Thus, owing to the high prevalence, under testing, low treatment adherence, and known negative effect on the physical function, it is contended that underdiagnosed SDB in SCI may be confounding physical rehabilitation research studies in individuals with SCI. Studies investigating the effect of treating SDB and its effect on physical rehabilitation in SCI were unable to be located. Thus, studies investigating the likely integrated relationship among physical rehabilitation, SDB, and proper treatment of SDB in SCI are needed. Owing to rapid growth in both sleep medicine and physical rehabilitation intervention research in SCI, the authors contend it is the appropriate time to begin the conversations and collaborations between these fields. We discuss a general overview of SDB and physical training modalities, as well as how SDB could be affecting these studies.

Impact of marriage on physical activity behavior in women with multiple sclerosis.

PURPOSE: Adopting and continuing physical activity (PA) is critical for the management of multiple sclerosis (MS). The role that spouses or partners play in the adoption and continuation of PA in women with MS has yet to be explored. METHODS: Nine women with MS and their respective spouses volunteered for in-depth, semi-structured interviews that lasted approximately an hour. Interviews were transcribed and analyzed thematically. Spouse interview data were used to contextualize and provide a richer understanding of themes from women with MS. RESULTS: Three themes were constructed from analysis of the interview data with women with MS: support, motivation to perform PA, and PA prior to MS. Support was most discussed and took the form joining in PA, supporting PA accomplishments or information sharing, assisting with PA, and encouraging separate PA. Motivation to perform PA and prior PA also were impacted by the women's spouses and their behaviors. CONCLUSIONS: This study points to the importance of support and perception of support by spouses for women with MS. Support was highly valued regardless of the form that it took. Women with MS could benefit from understanding and encouraging the various supporting roles spouses play in the decisions women with MS make to be physically active.IMPLICATIONS FOR REHABILITATIONWomen with MS and their spouses consider physical activity to be beneficial.Women with MS value the support their spouses provide to encourage them to be physically active.Women with MS can perceive support from their spouses in varying ways, including support in initiating physical activity, supporting physical activity accomplishments or information sharing, assisting with physical activity, and encouraging separate physical activity.Physical activity programming for this population should consider ways to incorporate spousal support.

Bilateral NIRS measurements of muscle mitochondrial capacity: Feasibility and repeatability.

BACKGROUND: Non-invasive determination of mitochondrial capacity via near infrared spectroscopy (NIRS) typically involves voluntary exercise of a single muscle group followed by as many as 26 brief ischemic cuff occlusions to determine a single recovery rate constant (k). PURPOSE: To determine the within- and between-visit repeatability of a shortened bilateral NIRS protocol, and to establish the feasibility of hamstring k measurements. METHODS: Sixteen young (eight women, eight men; 22 ± 3 years) active adults underwent a bilateral electrical stimulation protocol in which multiple (n = 4) measurements of k for the vastus lateralis (VL) and medial hamstring (MH) muscles were determined on two visits. Repeatability (CV% and intraclass correlations, ICC) and equivalency across visits were assessed for both muscles. RESULTS: Mean k values in the VL were consistent with published values and within-visit ICCs were moderately high for both muscles in both sexes. In men, average k values on visit 2 were within 1% (VL muscle) and 5% (MH muscle) of the values on visit 1 (all p > 0.78). In women, average k values were 10%-15% lower on visit 2 (p = 0.01 and p = 0.15 for MH and VL) with the largest between-visit differences in a subset of participants with the most days between visits. CONCLUSIONS: This bilateral NIRS protocol is time efficient and provides valid estimates of k in both sexes and muscle groups with acceptable within-visit repeatability. Lower than expected between-visit repeatability in some participants reinforces the need for further investigation of this newly developed protocol to identify and control for experimental and behavioral sources of variation.

Measuring tibial hemodynamics and metabolism at rest and after exercise using near-infrared spectroscopy.

The bone vascular system is important, yet evaluation of bone hemodynamics is difficult and expensive. This study evaluated the utility and reliability of near-infrared spectroscopy (NIRS), a portable and relatively inexpensive device, in measuring tibial hemodynamics and metabolic rate. Eleven participants were tested twice using post-occlusive reactive hyperemia technique with the NIRS probes placed on the tibia and the medial gastrocnemius (MG) muscle. Measurements were made at rest and after 2 levels of plantarflexion exercise. The difference between oxygenated and deoxygenated hemoglobin signal could be reliably measured with small coefficients of variation (CV; range 5.7-9.8%) and high intraclass correlation coefficients (ICC; range 0.73-0.91). Deoxygenated hemoglobin rate of change, a potential marker for bone metabolism, also showed good reliability (CV range 7.5-9.8%, ICC range 0.90-0.93). The tibia was characterized with a much slower metabolic rate compared with MG (p < 0.001). While exercise significantly increased MG metabolic rate in a dose-dependent manner (all p < 0.05), no changes were observed for the tibia after exercise compared with rest (all p > 0.05). NIRS is a suitable tool for monitoring hemodynamics and metabolism in the tibia. However, the local muscle exercise protocol utilized in the current study did not influence bone hemodynamics or metabolic rate. Novelty: NIRS can be used to monitor tibial hemodynamics and metabolism with good reliability. Short-duration local muscle exercise increased metabolic rate in muscle but not in bone. High level of loading and exercise volume may be needed to elicit measurable metabolic changes in bone.

Mitochondrial capacity using NIRS and incomplete recovery curves: Proximal and Medial Vastus Lateralis muscle.

Near-Infrared Spectroscopy (NIRS) has been used to measure muscle mitochondrial capacity (mVO2max) as the recovery rate constant of muscle metabolism after exercise. The current method requires as many as 50 short ischemic occlusions to generate 2 recovery rate constants. PURPOSE: To determine the effectiveness of using a 6-occlusion protocol (Mito6) versus one with 22 occlusions (Mito22) to measure muscle mitochondrial capacity. METHOD: In two independent data sets (bicep n=7, forearm A n=23), recovery curves were analyzed independently using both the Mito6 and Mito22 analyses. A third data set (Forearm B, n=16) was generated on forearm muscles of healthy subjects using four Mito6 tests performed in succession. Recovery rate constants were generated using a MATLAB routine. RESULTS: When calculated from the same data set, the recovery rate constants were not significantly different between the Mito22 and Mito6 analyses for the bicep (1.43+0.33min-1, 1.43+0.35min-1, p=0.81) and the forearm A (1.97+0.40min-1, 1.97+0.43min-1, p=0.90). The correlation between Mito22 and Mito6 recovery rate constants was y=1.07x-0.09, R2=0.90 for the bicep data and 1.00x+0.01, R2=0.85 for the forearm A data. When performing the four Mito6 tests in the Forearm B study; recovery rate constants were not different between tests (1.50±0.51 min-1, 1.42±0.54 min-1, 1.26±0.41 min-1, 1.29±0.47 min-1, P>0.05). CONCLUSIONS: Muscle mitochondrial capacity was not different between the Mito6 analysis and the longer Mito22 analysis. The Mito6 protocol was considered more practical as it used fewer ischemic occlusion periods, and multiple tests could be performed in succession in less time. There were no order effects for the rate constants of four repeated Mito6 tests of mitochondrial capacity, supporting the use of multiple tests to improve accuracy.

Reliability and reproducibility of a four arterial occlusions protocol for assessing muscle oxidative metabolism at rest and after exercise using near-infrared spectroscopy.

OBJECTIVE: To assess the reliability and reproducibility of using a four arterial occlusions protocol and near-infrared spectroscopy (NIRS) to measure resting and post-exercise muscle oxidative metabolism (mVO2). APPROACH: mVO2 was measured on the forearm muscles on two different days (day1 and day2) within one week in 11 healthy young adults (24.2 ± 2.7 years; 5 males). mVO2 was measured using NIRS during four repeated arterial occlusions at rest, and 5 min after exercise consisting of 90 s of rapid concentric contractions (5 minEPOC). MAIN RESULTS: Resting mVO2 with four measurements was 17.88 ± 3.04% min-1 on day 1 and 19.42 ± 3.03% min-1 on day 2 (p = 0.171) with a coefficient of variation (CV) of 10.1%. When using only the first measurement, the CV increased to 18.5% (p = 0.039). 5minEPOC was 212.4 ± 142.5% and 177.1 ± 125.8% higher than resting and was not different between days one and two (53.83 ± 21.17% min-1 and 52.22 ± 22.10% min-1, respectively, p= 0.199). The CV and intraclass correlation (ICC) for 5minEPOC between days one and two were, 6.5% and 0.98, respectively. Using only the first value for 5minEPOC resulted in slightly higher CV but similar ICC (7.6% and 0.98, respectively; both p > 0.05). SIGNIFICANCE: Our results suggest that within a single testing session, one arterial occlusion can provide reproducible measurements for both resting and post-exercise mVO2 similar to that of a four arterial occlusions protocol. While a four arterial occlusion protocol provides similar reliability for post-exercise mVO2 with one arterial occlusion, it reduces the day-to-day variance for resting mVO2 and therefore should be employed for longitudinal studies.

Near Infrared Spectroscopy Measurements of Mitochondrial Capacity Using Partial Recovery Curves.

BACKGROUND: Near-infrared spectroscopy (NIRS) has been used to measure muscle mitochondrial capacity (mVO2max) as the recovery rate constant of muscle metabolism after exercise. The current method requires as many as 50 short ischemic occlusions to generate two recovery rate constants. PURPOSE: To determine the validity and repeatability of using a 6-occlusion protocol versus one with 22 occlusions to measure muscle mitochondrial capacity. The order effect of performing multiple Mito6 test was also evaluated. METHOD: In two independent data sets (bicep n = 7, forearm A n = 23), recovery curves were analyzed independently using both the 6 and 22 occlusion methods. A third data set (forearm B n = 16) was generated on the forearm muscles of healthy subjects using four 6-occlusion tests performed in succession. Recovery rate constants were generated using a MATLAB routine. RESULTS: When calculated from the same data set, the recovery rate constants were not significantly different between the 22 occlusion and 6 occlusion methods for the bicep (1.43 ± 0.33 min-1, 1.43 ± 0.35 min-1, p = 0.81) and the forearm A (1.97 ± 0.40 min-1, 1.97 ± 0.43 min-1, p = 0.90). Equivalence testing showed that the mean difference was not different than zero and the 90% confidence intervals were within 5% of the average rate constant. This was true for the Mito6 and the Mito5∗ approaches. Bland-Altman analysis showed a slope of 0.21 min-1 and an r of 0.045 for the bicep dataset and a slope of -0.01 min-1 and an r of 0.045 for the forearm A dataset. When performing the four 6-occlusion tests; recovery rate constants showed no order effects (1.50 ± 0.51 min-1, 1.42 ± 0.54 min-1, 1.26 ± 0.41 min-1, 1.29 ± 0.47 min-1, P > 0.05). CONCLUSION: The Mito6 analysis is a valid and repeatable approach to measure mitochondrial capacity. The Mito6 protocol used fewer ischemic occlusion periods and multiple tests could be performed in succession in less time, increasing the practicality of the NIRS mitochondrial capacity test. There were no order effects for the rate constants of four repeated 6-occlusion tests of mitochondrial capacity, supporting the use of multiple tests to improve accuracy.

The effects of exercise on mood and prefrontal brain responses to emotional scenes in smokers.

The benefits of exercise for smokers attempting to quit are partially dependent on physical activity levels prior to cessation. Mood disturbances can manifest within 30 min of smoking a cigarette and contribute to negative reinforcement of smoking behavior over time, whereas a single bout of aerobic exercise can reduce negative mood states and improve affect on a similar timescale in non-smokers. The acute effects of exercise among non-abstaining smokers immediately after a cigarette are unknown but may have clinical implications for smokers considering cessation. The aim of this study was to examine the concurrent effects of exercise on mood disturbance and prefrontal brain hemodynamic response to emotionally arousing scenes 30 min after smoking a cigarette and to test whether prefrontal brain hemodynamic response was correlated with affective ratings of the scenes. Fifteen cigarette smokers, averaging 47.6 cigarettes/week in the year prior to screening, served as participants. Functional near-infrared spectroscopy was used to measure hemodynamic status over the dorsolateral prefrontal cortex (DLPFC). Participants viewed pleasant, unpleasant, and neutral scenes prior to smoking a cigarette and 30 min later after seated rest or exercise at a preferred intensity. Mood disturbance was assessed by the Profile of Mood States-Brief Form four times: before smoking a cigarette, before and after exercise and rest, and after a post-condition (exercise/rest) exposure to emotionally arousing scenes. Compared to seated rest, cycling after a cigarette reduced mood disturbance (p = =.038) and DLPFC hemodynamic response to unpleasant (p = =.003) and pleasant (p = =.021) scenes relative to neutral scenes. DLPFC hemodynamic response was not related to affective ratings of scenes. We report that cycling for 20 min at a preferred intensity reduces mood disturbances which occur shortly after smoking a cigarette and blunts DLPFC hemodynamic response to emotionally arousing scenes. The findings encourage further investigation of exercise for smokers in the maintenance stage of smoking cessation.

Impact of a student-driven wellness program for individuals with disabilities on caregivers and family members.

Aim: Few studies have addressed impact of participation in exercise programs on caregivers or family members of individuals with disabilities.Purpose: To evaluate the impact of interaction rich wellness program on family members or caregivers of participants.Methods: Nine family members or caregivers were selected for interviews. Interviews were transcribed and analyzed using a thematic approach.Results: Five themes were constructed from analysis of the interview data: benefit of class to self, positive feelings about participation, relationship dynamic, importance of classroom interaction, and burden of class. The first four themes occurred in caregivers despite individual burden determined by self-reported interview scores on the Zarit Burden interview.Conclusion: This study demonstrated the impact of an interaction rich exercise program on wellness of participants with disabilities and respective caregivers or family members. Caregivers or family members do acknowledge benefits of the program to themselves. However, the program does not reduce caregiver burden.Implications for RehabilitationRehabilitation professionals should be cognizant of the potential for indirect benefit of rehabilitation or exercise programs on family members or caregivers of patients.Rehabilitation programs should consider the indirect benefit on the caregivers of patients when evaluating the burden of a program on caregivers.Rehabilitation professionals should focus on interpersonal interaction to aid in positive outcomes for both patients and caregivers.