Decreased Muscle Oxygenation and Increased Arterial Blood Flow in the Non-Exercising Limb During Leg Exercise
ABSTRACT We evaluated arterial blood flow, muscle tissue oxygenation and muscle metabolism in the non-exercising limb during leg cycling exercise. Ten healthy male volunteers performed a graded leg cycling exercise at 0, 40, 80, 120 and 160 watts (W) for 5 min each. Tissue oxygenation index (TOI) of the non-exercising left forearm muscle was measured using a near-infrared spatially resolved spectroscopy (NIR(SRS)), and non-exercising forearm blood flow ((NONEX)FBF) in the brachial artery was also evaluated by a Doppler ultrasound system. We also determined O(2) consumption of the non-exercising forearm muscle (NONEXV(O)(2mus)) by the rate of decrease in O(2)Hb during arterial occlusion at each work rate. TOI was significantly decreased at 160 W (p < 0.01) compared to the baseline. The (NONEX)V(O)(2mus) at each work rate was not significantly increased. In contrast, (NONEX)FBF was significantly increased at 120 W (p < 0.05) and 160 W (p < 0.01) compared to the baseline. These results suggest that the O(2) supply to the non-exercising muscle may be reduced, even though (NONEX)FBF increases at high work rates during leg cycling exercise.
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ABSTRACT: To develop a reliable live-animal imaging method for monitoring muscle pathology in mouse models of myopathy. A caged near-infrared Cathepsin B (CTSB) substrate, ProSense 680, is evaluated in the dystrophin deficient mdx mice, a genetic homologue of Duchenne muscular dystrophy via optical imaging. We show high levels of infrared signal in dystrophic muscle relative to healthy muscle at 24 h post-injection. Imaging for CTSB presence revealed localization to inflammatory infiltrates and regenerating muscle fibers. A time series myotoxin-induced muscle injury experiment showed that CTSB activity and its mRNA levels peaked at the interface between inflammation and myoblast fusion stage of recovery. Prednisone treatment in mdx mice resulted in decreased CTSB activity and increased grip strength in forelimbs and hindlimbs. Optical imaging of CTSB activity is an ideal method to sensitively monitor inflammation, regeneration, and response to therapy in myopathic skeletal muscle.Molecular imaging and biology: MIB: the official publication of the Academy of Molecular Imaging 06/2011; 13(3):462-70. DOI:10.1007/s11307-010-0376-z
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ABSTRACT: We compared absolute values of regional tissue hemoglobin saturation (StO(2)), reproducibility, and dynamic range of four different instruments on the forearm of adults. The sensors were repositioned 10 times on each subject. Dynamic range was estimated by exercise with subsequent arterial occlusion. Mean StO(2) was 70.1% ± 6.7 with INVOS 5100, 69.4% ± 5.0 with NIRO 200 NX, 63.4% ± 4.5 with NIRO 300, and 60.8% ± 3.6 with OxyPrem. The corresponding reproducibility S(w) was 5.4% (CI 4.4-6.9), 4.4% (CI 3.5-5.2), 4.1% (CI 3.3-4.9), and 2.7% (CI 2.2-3.2), respectively. The dynamic ranges ΔStO(2) were 45.0%, 46.8%, 44.8%, and 27.8%, respectively. In conclusion, the three commercial NIRS instruments showed different absolute values, whereas reproducibility and dynamic range were quite similar.Biomedical Optics Express 11/2011; 2(11):3047-57. DOI:10.1364/BOE.2.003047
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ABSTRACT: The purpose of the present study was to elucidate changes in mean blood flow and oscillatory blood flow patterns to the inactive limb during leg cycle exercise in hypoxia. We hypothesized that oscillatory antegrade and retrograde blood flows to the nonworking limb would increase during incremental cycle exercise under hypoxic condition. Eight males participated in this study. Two maximal exercise tests were conducted on a semirecumbent cycle ergometer while subjects inhaled a normoxic (inspired oxygen fraction [FIO2] = 0.21) or hypoxic gas mixture (FIO2 = 0.12). The exercise began at an initial power output of 30 W, and workload was increased by 30 W every 2 min until exhaustion. Brachial artery blood velocity and diameter were simultaneously recorded during exercise using Doppler ultrasonography. Blood flow was calculated using the cross-sectional area of the brachial artery and time-averaged mean blood velocity. Mean blood flow decreased until 120 W in both trials (P < 0.05), and the magnitude of the reduction in mean blood flow was not different between two trials. However, the extent of changes in antegrade and retrograde blood flows during submaximal exercise in hypoxia was greater than that in normoxia (normoxia vs hypoxia: antegrade blood flow at 120 W = 145.4 ± 10.3 vs 172.4 ± 9.0 mL·min and retrograde blood flow at 120 W = -89.1 ± 4.9 vs -118.1 ± 6.2 mL·min, P < 0.05). These results indicate that hypoxia has a significant effect on oscillatory antegrade/retrograde blood flow patterns in nonworking limb during cycling exercise.Medicine and science in sports and exercise 06/2012; 44(6):1035-42. DOI:10.1249/MSS.0b013e31824294f9