This pilot study investigated hemodynamics in bone and muscle of the same leg during resistance exercise, using near-infrared spectroscopy (NIRS). Total (tHb) and oxygenated (O2Hb) hemoglobin increased in bone but decreased in muscle. Absolute peak tHb and O2Hb changes in bone were much smaller than absolute antipeak changes in muscle. Bone tHb and O2Hb reached an initial peak quickly and then decreased progressively; muscle tHb and O2Hb decreased initially and then plateaued. Bone perfusion changes during exercise appear independent of metabolism, suggesting that bone hemodynamics measured using NIRS during resistance training are driven by blood vessel compression and release.
We investigated central fatigue during maximal exercise (EXmax) after 12×20-min respiratory muscle endurance training (eRMT) sessions over 4 weeks using cerebral near-infrared spectroscopy (NIRS; left, right prefrontal cortices: LPFC, RPFC); and self-reported effort perceptions (RPE). Healthy participants improved eRMT performance with no spirometry changes. Pre-eRMT, EXmax oxygenated (O2Hb), deoxygenated (HHb), and total (tHb) hemoglobin increases were larger in LPFC than RPFC. Post-eRMT, EXmax O2Hb, HHb, and tHb increases were smaller in LPFC than RPFC. Post-eRMT EXmax RPE were smaller. eRMT-induced LPFC-to-RPFC hemodynamic shifts during EXmax may facilitate decreased RPE.
The purpose of this study was to test the hypothesis that mobile, wireless near-infrared spectroscopy (NIRS) instruments can be used during standard lung function tests to measure adaptations in respiratory muscle metabolism over weeks to months. In eight varsity soccer players at 0 weeks and after 16 weeks of routine training, commercially available mobile, wireless NIRS instruments were used to measure oxygenation and hemodynamics in the sternocleidomastoid (SCM, accessory inspiration muscle). During maximal expiratory pressure (MEP) and forced vital capacity (FVC) maneuvers we determined peak or antipeak changes relative to baseline in oxygenation and hemodynamics: Δ%Sat (muscle oxygen saturation), ΔtHb (total hemoglobin), ΔO2Hb (oxygenated hemoglobin), and ΔHHb (deoxygenated hemoglobin). Subjects reported that the average training load was ~13.3 h/week during the 16 study weeks, compared to ~10.4 h/week during 12 prior weeks. After 16 weeks of training compared to 0 weeks we found statistically significant increases in SCM Δ%Sat (57.7%), ΔtHb (55.3%), and ΔO2Hb (56.7%) during MEP maneuvers, and in SCM Δ%Sat (64.8%), ΔtHb (29.4%), and ΔO2Hb (51.6%) during FVC maneuvers. Our data provide preliminary evidence that NIRS measurements during standard lung function tests are sufficiently sensitive to detect improvements or declines in respiratory muscle metabolism over periods of weeks to months due to training, disease, and rehabilitation exercise.
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