Biology subjects

Umehara, J.

Publications and source records attributed to Umehara, J..

3 recordsLinked to original sources

bioRxiv2025

The relationship between passive ankle joint stiffness and the stiffness of muscles, nerve, and tendon

Passive joint stiffness reflects the stiffness of various soft tissues across a joint. However, no previous studies have investigated the relationship between passive joint stiffness and muscle, nerve, and tendon stiffness. This study aimed to clarify whether passive ankle joint stiffness is related to stiffness in the triceps surae muscles, tibial nerve, and Achilles tendon. Thirty-eight healthy adults participated in the study. The passive ankle joint stiffness (slope of angle-passive torque curve) and shear wave velocities, which indicate soft tissue stiffness, of the triceps surae muscles and tibial nerve were measured at 5{degrees} of ankle plantarflexion and 5{degrees}, 15{degrees}, and 25{degrees} of ankle dorsiflexion. The shear wave velocity of the Achilles tendon was measured only at 5{degrees} of plantarflexion. A multiple regression model (forced-entry method) was constructed at each angle, specifying the shear wave velocities as the independent variables and passive joint stiffness as the dependent variable. At 5{degrees} of plantarflexion, no shear wave velocities were significantly related to passive joint stiffness (all p [≥] 0.05). At 5{degrees} and 15{degrees} of dorsiflexion, only the shear wave velocities of the tibial nerve were significantly positively related to passive joint stiffness (p = 0.024 and 0.008, respectively). At 25{degrees} of dorsiflexion, the shear wave velocities of the lateral gastrocnemius muscle and tibial nerve were significantly positively related to passive joint stiffness (p = 0.002 and 0.001, respectively). It can be concluded that both triceps surae muscles stiffness and tibial nerve stiffness are related to passive ankle joint stiffness.

biophysics↗

bioRxiv2025

Tibial nerve stiffness is related to maximum angle of ankle dorsiflexion

The maximum angle of ankle dorsiflexion is affected by the triceps surae muscle stiffness and stretch tolerance, which may be strongly reflected by the tibial nerve stiffness. However, no study has evaluated the triceps surae muscle and tibial nerve stiffness simultaneously or clarified their association with the maximum angle. The purpose of this study was to investigate the association between the maximum angle and both the stiffness. Forty-one healthy adults participated. The shear wave velocities of the triceps surae muscles and tibial nerve were measured at 5{degrees}, 15{degrees}, and 25{degrees} ankle dorsiflexion. Multiple linear regression analysis was performed using the forced entry method, specifying the shear wave velocities of the four tissues as the independent variables and the maximum angle as the dependent variable. This analysis was performed at each angle where the shear wave velocity was measured. Multiple linear regression analysis was also performed using the stepwise method, specifying the shear wave velocities of the tibial nerve at the three angles as the independent variables and the maximum angle as the dependent variable. Using the forced entry method, the shear wave velocity of the tibial nerve at each angle was significantly negatively associated with the maximum angle, whereas those of the muscles were not. Using the stepwise method, only the shear wave velocity of the tibial nerve at 25{degrees} was significantly negatively associated with the maximum angle. These results suggest that the tibial nerve stiffness in a greatly lengthened position determines the maximum angle of ankle dorsiflexion.

physiology↗

bioRxiv2021

Validity of freehand three-dimensional ultrasound system in measurement of three-dimensional surface shape of shoulder muscles

Freehand three-dimensional ultrasound (3DUS) system is a promising technique for accurately assessing muscle morphology. However, its accuracy has been validated mainly in terms of volume by examining lower limb muscles. This study aimed to validate 3DUS in the measurements of 3D surface shape and volume by comparing them with MRI measurements while ensuring the reproducibility of participant posture by focusing on the shoulder muscles. The supraspinatus, infraspinatus, and posterior deltoid muscles of 10 healthy males were scanned using 3DUS and MRI while secured by an immobilization support customized for each participant. A 3D surface model of each muscle was created from the 3DUS and MRI methods, and the agreement between them was assessed. For the muscle volume, the mean difference between the two models was within -0.51 cm3. For the 3D surface shape, the distances between the closest points of the two models and Dice similarity coefficient were calculated. The results showed that the median surface distance was less than 1.21 mm and Dice similarity coefficient was larger than 0.85. These results suggest that, given the above error is permitted, 3DUS can be used as an alternative to MRI in measuring volume and surface shape, even for the shoulder muscles.

bioengineering↗