Are Improvements in Skeletal Muscle Oxidative Capacity Possible in the Elderly? [Meeting Abstract]
Partitioning key determinants of oxygen consumption: Novel insight from Dual Wavelength Diffuse Correlation Spectroscopy [Meeting Abstract]
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.
Age-related microvascular dysfunction: novel insight from near-infrared spectroscopy
NEW FINDINGS:). However, owing to a lower skeletal muscle resting metabolic rate, StO2min was also significantly attenuated in the elderly participants compared with the young control subjects (55.7Â Â±Â 3.5 versus 41.0Â Â±Â 3.4%), resulting in a much lower ischaemic stimulus. To account for this important difference between groups, we then matched the level of tissue ischaemia in a subset of young healthy participants by reducing the cuff occlusion protocol to 3Â min. Remarkably, when we controlled for tissue ischaemia, we observed no differences in any of the hyperaemic end-points between the young and elderly participants. These data highlight the important role NIRS can serve in vascular biology, but also establish the need for assessing tissue ischaemia during cuff occlusion protocols.
Near-infrared spectroscopy detects age-related differences in skeletal muscle oxidative function: promising implications for geroscience
Age is the greatest risk factor for chronic disease and is associated with a marked decline in functional capacity and quality of life. A key factor contributing to loss of function in older adults is the decline in skeletal muscle function. While the exact mechanism(s) remains incompletely understood, age-related mitochondrial dysfunction is thought to play a major role. To explore this question further, we studied 15 independently living seniors (age: 72Â Â±Â 5Â years; m/f: 4/11; BMI: 27.6Â Â±Â 5.9) and 17 young volunteers (age: 25Â Â±Â 4 years; m/f: 8/9; BMI: 24.0Â Â±Â 3.3). Skeletal muscle oxidative function was measured in forearm muscle from the recovery kinetics of muscle oxygen consumption using near-infrared spectroscopy (NIRS). Muscle oxygen consumption was calculated as the slope of change in hemoglobin saturation during a series of rapid, supra-systolic arterial cuff occlusions following a brief bout of exercise. Aging was associated with a significant prolongation of the time constant of oxidative recovery following exercise (51.8Â Â±Â 5.4Â sec vs. 37.1Â Â±Â 2.1Â sec, PÂ =Â 0.04, old vs. young, respectively). This finding suggests an overall reduction in mitochondrial function with age in nonlocomotor skeletal muscle. That these data were obtained using NIRS holds great promise in gerontology for quantitative assessment of skeletal muscle oxidative function at the bed side or clinic.
Commentaries on Viewpoint: Principles, insights, and potential pitfalls of the noninvasive determination of muscle oxidative capacity by near-infrared spectroscopy
The absence of rhabdomyolysis-induced renal failure following the World Trade Center collapse [Letter]