Introduction: We investigated the motor unit (MU) firing pattern in type 2 diabetes mellitus (T2DM) patients by means of multichannel surface electromyography (SEMG). Methods: Eight T2DM patients and 8 age-matched, healthy men performed a ramp-up contraction to 20% of maximal voluntary contraction (MVC). They also performed a sustained contraction at 10% of MVC during isometric knee extension. Multichannel SEMG signals recorded from the vastus lateralis muscle were decomposed with the convolution kernel compensation technique to extract individual MU firing patterns. Results: During the ramp contraction, the extent of MU firing modulation was significantly attenuated in T2DM. Variability of MU firing rate was significantly higher in T2DM at later periods during the sustained contraction. Conclusions: Our findings suggest that T2DM patients manifest characteristic MU activity patterns due possibly to some degree of neuromuscular impairment affecting the integrity of MU firing modulation. Muscle Nerve 48:806–813, 2013
Assessments of both neural and muscular adaptations during interventions would provide valuable information for developing countermeasures to age-related muscle dysfunctions. We investigated the effect of fish protein ingestion on training-induced neural and muscular adaptations in older adults. Twenty older adults participated 8 weeks of isometric knee extension training intervention. The participants were divided into two groups who took fish protein (n = 10, Alaska pollack protein, APP) or casein (n = 10, CAS). Maximal muscle strength during knee extension, lower extremity muscle mass (body impedance method), and motor unit firing pattern of knee extensor muscle (high-density surface electromyography) were measured before, during, and after the intervention. Muscle strength were significantly increased in both CAS (124.7 ± 5.8%) and APP (117.1 ± 4.4%) after intervention (p < .05), but no significant differences between the groups were observed (p > .05). Significant increases in lower extremity muscle mass from 0 to 8 weeks were demonstrated only for APP (102.0 ± 3.2, p < .05). Greater changes in motor unit firing pattern following intervention were represented in CAS more than in APP. These results suggest that nutritional supplementations could modulate neural and muscular adaptations following resistance training and fish protein ingestion preferentially induces muscular adaptation without the detectable neural adaptation in older adults.
The emission flux of volatiles from each fumarolic field in volcanic and geothermal areas can be used to evaluate the current state of magmatic activity and predict its future trends. The emission flux of SO2 has been quantified in many fumarolic fields using remote sensing techniques, such as differential optical absorption spectroscopy (DOAS). However, most of these remote sensing techniques are inapplicable to fumarolic fields emitting volatiles depleted in SO2 to which most of the geothermal fields are classified. In this study, we developed a vertical sensor array system to quantify the emission flux of H2S from each fumarolic field by integrating the cross-sectional distributions of H2S concentrations in the volcanic plume using the vertical sensor array system. In Iwo-yama of the Kirishima volcanic complex, the cross-sectional distribution of H2S concentrations was determined using the walking traverse method by moving the vertical sensor array system in the plume perpendicular to the direction of plume transport. The emission flux of SO2 (2.2 ± 0.4 ton SO2/day) was estimated from that of H2S using the walking traverse method (2.6 ± 0.5 ton H2S/day) and the molar ratio of the plume (SO2/H2S=0.45) corresponds well with that estimated optically by JMA. We concluded that the emission flux quantified using the vertical sensor array system was reliable. In the Oyunuma pond in the Kuttara volcano, the emission flux of H2S was quantified as 2.0 ton H2S/day through the fixed point method, wherein the vertical sensor array system was fixed in one point, whereas the cross sectional distribution of H2S in the plume was estimated using the natural variation in wind direction. The topography is often irregular and wind direction is variable in most fumarolic fields; thus, in general, the fixed point method should be more suitable to determine the emission flux of H2S from fumarolic fields, wherein H2S occupies a major portion of the total sulfur emission.
