In sports sciences, blood lactate is commonly measured for performance testing or setting exercise intensity. Differences in measuring lactate concentration over time and across sampling sites during constant exercise...In sports sciences, blood lactate is commonly measured for performance testing or setting exercise intensity. Differences in measuring lactate concentration over time and across sampling sites during constant exercise are unknown. We aimed to compare blood lactate concentration across sampling sites during constant exercise. Eight participants performed three bouts of 20-min steady-state cycle exercise, consisting of 45, 60, and 75% of peak oxygen uptake (V . O2peak). Blood lactate levels were measured simultaneously from the fingertip and earlobe every 5 min during exercise. The time course analysis revealed that lactate level in the fingertip was significantly higher than in the earlobe at either work intensity (P < 0.05). A significant interaction effect (site x time) was observed at 60% V O2peak (P < 0.001), which indicated that the difference in samples across sampling sites decreased over time. The levels in the fingertip samples were higher at 5 min (P < 0.05);this difference was not noted after 10 min. Similarly, the fingertip values were significantly higher until 10 min (P < 0.05), but not after 15 min at 75% V O2peak. These findings suggest that the sampling site may affect the time course of change in lactate value under a constant workload.展开更多
脉冲负载由于其周期性脉动的特点,使电网系统公共母线的功率产生持续的、高峰值脉冲,严重威胁到电力系统的安全稳定运行。针对常用脉冲负载结构,建立了以脉冲负载为主负载的公网和柴油发电机组(60 kW)供电试验平台。基于脉冲负载的工作...脉冲负载由于其周期性脉动的特点,使电网系统公共母线的功率产生持续的、高峰值脉冲,严重威胁到电力系统的安全稳定运行。针对常用脉冲负载结构,建立了以脉冲负载为主负载的公网和柴油发电机组(60 kW)供电试验平台。基于脉冲负载的工作机理,分别对不同脉冲频率、占空比下的脉冲负载进行联网/脱网试验,对公共母线处的暂态和稳态功率特性进行对比讨论。针对传统平均功率无法准确、有效表征系统稳态功率的问题,提出了基于脉冲频率的瞬时功率平均值(pulsed frequency based instantaneous power average value,PFIPA)的计算方法,试验结果证明,该方法具有一定的合理性和正确性,在联网和脱网电力系统均可适用。所建试验平台及分析结论,对脉冲负载在电力系统中的应用、设计、系统容量、功率分配等方面具有重要意义和参考价值。展开更多
文摘In sports sciences, blood lactate is commonly measured for performance testing or setting exercise intensity. Differences in measuring lactate concentration over time and across sampling sites during constant exercise are unknown. We aimed to compare blood lactate concentration across sampling sites during constant exercise. Eight participants performed three bouts of 20-min steady-state cycle exercise, consisting of 45, 60, and 75% of peak oxygen uptake (V . O2peak). Blood lactate levels were measured simultaneously from the fingertip and earlobe every 5 min during exercise. The time course analysis revealed that lactate level in the fingertip was significantly higher than in the earlobe at either work intensity (P < 0.05). A significant interaction effect (site x time) was observed at 60% V O2peak (P < 0.001), which indicated that the difference in samples across sampling sites decreased over time. The levels in the fingertip samples were higher at 5 min (P < 0.05);this difference was not noted after 10 min. Similarly, the fingertip values were significantly higher until 10 min (P < 0.05), but not after 15 min at 75% V O2peak. These findings suggest that the sampling site may affect the time course of change in lactate value under a constant workload.
文摘脉冲负载由于其周期性脉动的特点,使电网系统公共母线的功率产生持续的、高峰值脉冲,严重威胁到电力系统的安全稳定运行。针对常用脉冲负载结构,建立了以脉冲负载为主负载的公网和柴油发电机组(60 kW)供电试验平台。基于脉冲负载的工作机理,分别对不同脉冲频率、占空比下的脉冲负载进行联网/脱网试验,对公共母线处的暂态和稳态功率特性进行对比讨论。针对传统平均功率无法准确、有效表征系统稳态功率的问题,提出了基于脉冲频率的瞬时功率平均值(pulsed frequency based instantaneous power average value,PFIPA)的计算方法,试验结果证明,该方法具有一定的合理性和正确性,在联网和脱网电力系统均可适用。所建试验平台及分析结论,对脉冲负载在电力系统中的应用、设计、系统容量、功率分配等方面具有重要意义和参考价值。