Department of Integrative Physiology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
Department of Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas.
J Appl Physiol (1985). 2020 Nov 1;129(5):1161-1172. doi: 10.1152/japplphysiol.00392.2020. Epub 2020 Sep 24.
Our laboratory has reported with near-infrared spectroscopy (NIRS) that prefrontal oxygenated-hemoglobin concentration (Oxy-Hb), measured as index of regional cerebral blood flow, increased before and at the onset of arbitrary (i.e., noncued) ergometer exercise in a laboratory environment. In the current study, we hypothesized that naturally occurring over-ground locomotion, despite "very light" motor effort, as indicated by a Borg scale of 8.0 ± 0.3, likewise causes preexercise activation of the prefrontal cortex. Using wireless NIRS, we examined in this study how early and to what extent prefrontal activity changed before the onset of arbitrary walking in 13 subjects. Prefrontal Oxy-Hb increased 2 s before the onset of arbitrary walking, and the increased Oxy-Hb reached a peak at 5 s from walking onset. The preexercise and initial increase in prefrontal Oxy-Hb was absent when over-ground walking was forced to start by cue. The difference in the Oxy-Hb response between arbitrary and cued start, which was considered to be related to central command, became significant 2 s before walking onset, preceding the difference in the heart rate (HR) response by 8 s. This demonstrated a positive relationship with the HR difference in 69% of subjects. Imagery of arbitrary walking was, likewise, able to increase prefrontal oxygenation to the same extent as actual walking. Thus, it is likely that prefrontal oxygenation increases before the onset of naturally occurring walking in daily life, despite "very light" effort. The increased prefrontal oxygenation may contribute at least partly to cardiac adjustment, synchronized with the beginning of motor performance. We found using wireless near-infrared spectroscopy that prefrontal oxygenation increased before the onset of arbitrary over-ground walking, whereas the preexercise increase was absent when walking was suddenly started by cue. The difference in prefrontal oxygenation between start modes (considered related to central command) preceded heart rate response variances and demonstrated a positive relationship with the difference in heart rate. The central command-related prefrontal activity may contribute to cardiac adjustment, synchronized with the beginning of over-ground walking.
我们的实验室曾利用近红外光谱（NIRS）技术报告称，在实验室环境中，进行任意（即无提示）测力计运动前和运动开始时，前额叶氧合血红蛋白浓度（Oxy-Hb）会增加，氧合血红蛋白作为区域性脑血流的指标而增加。在当前的研究中，我们假设尽管运动强度非常低（根据 Borg 量表为 8.0±0.3），但自然发生的地面行走会导致前额叶皮层在运动前被激活。使用无线 NIRS，我们在这项研究中检查了 13 名受试者在进行任意行走前，前额叶活动会提前多久以及提前到何种程度发生变化。任意行走开始前 2 秒，前额叶 Oxy-Hb 增加，从行走开始起 5 秒，Oxy-Hb 达到峰值。当强制通过提示开始地面行走时，预先行走的 Oxy-Hb 没有增加，也没有初始增加。在行走开始前 2 秒，任意开始和提示开始之间的 Oxy-Hb 反应之间的差异变得显著，比心率（HR）反应提前 8 秒。这表明在 69%的受试者中，与 HR 差异呈正相关。任意行走的想象同样能够增加前额叶的氧气供应，达到与实际行走相同的程度。因此，尽管“非常轻”的运动，日常生活中很可能在自然发生的行走开始之前，前额叶就会增加氧气供应。增加的前额叶氧气供应至少可能部分有助于与运动表现开始同步的心脏调整。我们使用无线近红外光谱技术发现，在任意地面行走开始前，前额叶的氧气供应增加，而当行走突然通过提示开始时，运动前的增加则消失。启动模式之间的前额叶氧合差异（被认为与中央命令有关）先于心率反应变化，并与心率差异呈正相关。与中央命令相关的前额叶活动可能有助于与地面行走开始同步的心脏调整。
