Abstract
Establish reliability of near-infrared spectroscopy (NIRS) mitochondrial capacity measurement and assess validity using heating and cooling interventions. We recruited 13 participants for four visits. Two visits consisted of a series of blood pressure occlusions proximal to the NIRS probe and electrical stimulation to the thigh, calf and forearm for reliability. Visits 3 and 4 required heating or cooling of the three muscles, using the protocol above. The between day reliability coefficient of variation (CV) in the forearm was 3% and time constant (TC) average was 41.9 ± 9.2 seconds (s). The within day CV in the forearm = 4.5%, the calf = 5.5% and the thigh = 4.6% (n = 13). Within day reliability for the cold condition in the forearm = 5.9%, calf = 4.3% and thigh = 4.4% and within day for the hot condition in the forearm = 6.4%, calf = 5.3% and thigh = 4.6%. The cold condition increased TC in the forearm, but decreased TC with heat (p < 0.05). The thigh decreased mitochondrial capacity with heat (p < 0.05), but cold was no different from control. These results suggest NIRS mitochondrial capacity has good within and between day reliability and temperature changes the mitochondrial capacity time constant.
Highlights
Near-infrared spectroscopy (NIRS) is a noninvasive device used to measure changes in oxygenated and deoxygenated hemoglobin/myoglobin and total hemoglobin, blood volume or flow in localized muscles during rest and exercise [1]
The arterial occlusion slopes are fit to an exponential curve and a time constant is calculated as a measure of mitochondrial capacity [3]
Depending on the mitochondrial time constant, higher mitochondria capacity correlates to a lower time constant, while lower mitochondrial capacity relates to a higher time constant
Summary
Near-infrared spectroscopy (NIRS) is a noninvasive device used to measure changes in oxygenated and deoxygenated hemoglobin/myoglobin and total hemoglobin, blood volume or flow in localized muscles during rest and exercise [1]. There is a lack of research looking at NIRS mitochondrial capacity in a variety of muscles in the same person and the validity and reliability of these measurements using clinically relevant manipulations. Decreases blood flow through vasoconstriction and permeability of the local vessels in order to reduce swelling [12] and reduces metabolic demand, which should reduce mitochondrial capacity. The aim of this study was to establish validity and reliability of skeletal muscle NIRS mitochondrial capacity measurements in young, healthy individuals We predicted that the NIRS mitochondrial capacity recovery protocol will be effective in proof of power for clinical interventions. We will have overall good across day reliability in the forearm and within day reliability in all three muscles
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