The mechanical characteristics of single-leg squat exercise with emphasis on pelvic elevation / 体力科学

Movement control and muscle function for pelvic movement in the frontal plane (pelvic elevation) are important for various single-leg sports activities. We aimed to clarify mechanical characteristics of pelvic squat (P-Sq: single-leg squat exercise with emphasis on pelvic elevation, developed by our research group) compared with the double-leg squat (D-Sq) and single-leg squat (S-Sq). Twelve male track and field athletes performed D-Sq, S-Sq, and P-Sq exercises at various loads (90%, 75%, and 60% of 1-repetition maximum [1RM]), using maximum effort. Kinematic and kinetic data were calculated using data recorded with a motion capture system and force platforms. We observed the highest values with P-Sq, followed by S-Sq and D-Sq under all load conditions as follows: peak vertical ground reaction force and rate of force development (RFD), range of pelvic elevation, peak pelvic elevation velocity, peak powers associated with hip abduction torque and trunk lateral flexion torque. In P-Sq, RFD at 90% 1RM was smaller than under the other load conditions, whereas peak vertical ground reaction force at 90% 1RM was larger than under the other load conditions. There were no differences among load conditions with regard to hip abduction and trunk lateral flexion torques and powers. Therefore, characteristics of P-Sq compared to those of D-Sq and S-Sq are 1) larger and faster pelvic elevation, using related muscles (hip abductors and trunk lateral flexors) under all load conditions, 2) larger peak ground reaction force with pelvic elevation under large load conditions, and larger RFD in pelvic elevation under low load conditions.

Time-series relationship to achieve performance on rebound drop jump / 体力科学

<p>The aim of this study was to demonstrate a time-series relationship in drop jump (DJ) from a pre-set state with improved performance. Twelve male college athletes performed a DJ from a height of 0.60 m. DJ performance was assessed with a DJ-index (jump height/contact time). Short-interval intracortical inhibition (SICI) was assessed as intracortical inhibitory circuit excitability in a pre-set state, calculated by using paired-pulse transcranial magnetic stimulation for the medial gastrocnemius muscle (MG). The H-reflex of the left MG and the ankle joint torque were calculated in the early phase of take-off. A significant correlation was shown between ⊿SICI during the pre-set state and the DJ index. Thus, we examined the relationships between phases, focusing on time-series relationships throughout the jump period. The results showed a significant correlation between ⊿SICI during the pre-set state and %H-reflex during the early phase of take-off, and peak ankle joint torque during take-off was also significantly correlated with %H-reflex during the early phase of take-off. A significant correlation was also demonstrated between ankle joint torque during take-off and the DJ-index. In conclusion, we observed a time-series relationship between DJ from a pre-set state and improved performance. A decrease of intracortical inhibitory circuit excitability in the pre-set state affects stretch-reflex facilitation during the early phase of take-off; stretch-reflex facilitation results in the development of a large force in the ankle joint during take-off, and this force develops ankle joint torque. These findings may be used to improve jump performance.</p>

Effect of short-interval intracortical inhibition in motor cortex during pre-set on rebound drop jumping performance / 体力科学

This study aimed to assess the effect of short-interval intracortical inhibition (SICI) before a jump off a platform (pre-set) on drop jump (DJ); the purpose was to investigate the relationship between this activity and performance, and the different effects of SICI on agonist and antagonist muscles during pre-set for jump athletes. Jump athletes (Jumper group, n=13) and Other athletes (Other group, n=9) performed DJ from drop heights of 0.30, 0.45, and 0.60 m). DJ performance was evaluated with DJ-index which was calculated from contact time and jump height. SICI was calculated from motor evoked potentials (MEP) recorded using paired-pulse transcranial magnetic stimulation for the medial gastrocnemius (MG) and tibialis anterior (TA) muscles in 7 jump athletes. Significantly higher DJ performance was observed for the Jumper group at all drop heights, and the Jumper group exhibited greater performance for the highest drop height than the Other groups. Significant decreases in SICI for MG were observed for the Jumper groups, and this decrease in inhibition was more prominent for the highest drop height during pre-set. Furthermore, the correlation between SICI for MG and DJ-index was stronger for increased drop heights, and a significantly positive correlation between these variables was observed at a height of 0.60 m. However, the SICI during the pre-set for TA exhibited no significant change under any of the conditions. The results of the present study suggest the importance of selective disinhibition of brain areas associated with the agonistic muscles during pre-set for higher DJ performance.

Pancreatic Neuroendocrine Carcinoma with Obstruction of Main Pancreatic Duct / 日本農村医学会雑誌

　　Pancreatic neuroendocrine tumors, relatively rare cancers, mostly arise in the pancreatic parenchyma with infrequent involvement of the main pancreatic duct. Now and then, however, case reports have been published on pancreatic neuroendocrine carcinoma in which the main pancreatic duct is obstructed by tumor cells with severely fibrous stromal cells. Here, in this paper, we report a case of pancreatic neuroendocrine carcinoma with obstruction of the main pancreatic duct. A 59-year-old man complained of right upper abdominal pain. Magnetic resonance cholangiopancreatography and fat-suppressed T1-weighted magnetic resonance imaging showed gallbladder stones, a low-intensity-area measuring 8 mm in diameter in the pancreatic body, and club-shaped dilatation at the distal end of the pancreatic duct. The patient was thus diagnosed with a tumor in the pancreatic body and cholecystolithiasis, and underwent distal pancreatectomy and cholecystectomy. HE-staining showed tumor cells with eosinophilic cytoplasm and nuclear atypia. The infiltrative growth of the cells with severe fibrosis caused stenosis of the pancreatic duct. Based on the positive results of immunohistochemical staining for chromogranin A and synaptophysin and the Ki-67 index, the tumor was finally identified as pancreatic neuroendocrine carcinoma. The patient has been under follow-up with no additional treatment for >3 years since the surgery, without evidence of tumor recurrence.

The effect of elastic-taping on long-latency somatosensory evoked potentials (SEPs) / 体力科学

Taping is widely used by sports trainers to prevent injury and to protect affected sites post-injury. However, it is not clear whether taping affect the perception of somatosensory stimulation. We sought to clarify the effect of taping on somatosensory stimulation using somatosensory evoked potentials (SEPs). We recorded SEPs following transcutaneous electrical stimulation of the right medial forearm in ten healthy volunteers. SEPs were recorded from 9 electrodes on the scalp under control, elastic-taping and white-taping conditions. Subjects relaxed on a comfortable reclining seat without taping in the control condition, while they were subjected to taping along the muscle of forearm with tension (elastic-taping) and without tension (white-taping) in the taping conditions. Results showed that the peak amplitude of N140 did not differ significantly among the three conditions but the peak amplitude of P250 was significantly lower in the elastic-taping condition than control and white-taping conditions. Elastic-taping with tension along the muscles changes various afferent inputs from muscle spindle or skin, and this may affect the perception of somatosensory stimulation.