During a half marathon, the foot is exposed to prolonged repetitive mechanical loading, which may affect plantar mechanosensory function. This study investigated changes in whole-foot vibration perception threshold (WF-VPT) after a half marathon. Using a pre–post-design, 23 recreational runners participated. Overall, data from 20 participants were analysed after three participants were excluded as outliers. WF-VPT were assessed, after 10-min acclimatization period at room temperature, before and after the half-marathon using a vibration exciter platform at 30 and 200 Hz. Wilcoxon signed-rank tests showed a significant increase in WF-VPT at 30 Hz (p = 0.02) and a significant decrease in WF-VPT at 200 Hz (p = 0.001). At 30 Hz, the median (interquartile range) WF-VPT increased from 1.77 (1.50–2.36) µm before exercise to 2.08 (1.87–2.83) µm after the half marathon. In contrast, at 200 Hz WF-VPT decreased from 0.09 (0.08–0.12) µm to 0.06 (0.04–0.10) µm. Furthermore, linear mixed-effects models assessed the effects of age, plantar temperature, and gender on WF-VPT at 30 and 200 Hz. Only age showed a significant positive association with WF-VPT at both frequencies. The frequency-specific changes in WF-VPT may be associated with differential contributions of mechanosensory pathways involved in low- and high-frequency vibration perception. Differences in the structural and functional properties of these pathways may influence how they respond to mechanical stimulation and running-related loading.
The vesicular nucleotide transporter (VNUT) plays a key role in ATP-mediated intercellular signaling by regulating ATP release into the extracellular space. In the central nervous system, VNUT is involved in communication between neurons and glial cells; however, its distribution in sensory ganglia of the peripheral nervous system remains incompletely understood. This study aimed to investigate VNUT immunoreactivity in sensory ganglia following acute peripheral nerve injury. After tooth extraction–induced acute nerve injury, ATF3-positive primary sensory neurons, a marker of neuronal damage, were observed in sensory ganglia. VNUT immunoreactivity in ATF3-positive primary sensory neurons and adjacent satellite glial cells was markedly increased in a coordinated manner at days 1, 5, and 7 after tooth extraction. In addition, P2X3, P2X4, and P2X7 receptor immunoreactivity was detected in primary sensory neurons, satellite glial cells, and macrophages. These findings suggest that VNUT-associated ATP signaling may contribute to communication among primary sensory neurons, satellite glial cells, and macrophages in sensory ganglia following nerve injury.
Limb-trunk coordination plays an essential role in daily actions. The reticulospinal contribution in limb muscles has been suggested to be modulated by long-term motor experience, such as strength training. However, it remains unclear whether reticulospinal contributions in limb-trunk coordinated movements are modulated by strength training. This study aimed to determine whether reticulospinal contributions to limb-trunk coordination differ between strength-trained and untrained individuals. Fifteen long-term (≥3 yrs) strength-trained and 15 untrained healthy men participated in this study. Participants performed a rapid bilateral arm-curl task while standing, using a load corresponding to 35% of their one-repetition maximum, in response to visual, visual-auditory (80 dB), or visual-startling (115 dB) stimuli. Electromyography (EMG) was recorded from the right biceps brachii (BB) and erector spinae (ES) muscles during the task. In the visual-alone condition, ES activation occurred closer in time to BB onset in the trained group than in the untrained group, indicating tighter temporal coordination between the limb prime mover and trunk postural muscles in strength-trained individuals. In both groups, visual-startling stimuli shortened the EMG onset of both the BB and ES, suggesting reticulospinal contributions to both muscles. Notably, the relative reduction in EMG onset of the BB induced by the startling stimulus was smaller in the trained group than in the untrained group, whereas no difference between groups was observed for the ES. These findings suggest that strength training may modify limb-trunk muscle coordination during standing arm curls and may be associated with muscle-specific adaptations in reticulospinal contributions.
