Stretching is an effective exercise for increasing body flexibility and pain relief. This study investigates the relationship between stretching intensity and relaxation effects, focusing on brainwaves and autonomic nervous system (ANS) activity. We used a crossover design with low- and high-intensity conditions to elucidate the impact of varying stretching intensities on neural activity associated with relaxation in 19 healthy young adults. Participants completed mood questionnaires. Electroencephalography (EEG) and plethysmography measurements were also obtained before, during, and after stretching sessions. The hamstring muscle was targeted for stretching, with intensity conditions based on the Point of Discomfort. Data analysis included wavelet analysis for EEG, plethysmography data, and repeated-measures ANOVA to differentiate mood, ANS activity, and brain activity related to stretching intensity. Results demonstrated no significant differences between ANS and brain activity based on stretching intensity. However, sympathetic nervous activity showed higher activity during the rest phases than in the stretch phases. Regarding brain activity, alpha and beta waves showed higher activity during the rest phases than in the stretch phases. A negative correlation between alpha waves and sympathetic nervous activities was observed in high-intensity conditions. However, a positive correlation between beta waves and parasympathetic nervous activities was found in low-intensity conditions. Our findings suggest that stretching can induce interactions between the ANS and brain activity.

Visual information affects static postural control, but how it affects dynamic postural control still needs to be fully understood. This study investigated the effect of proprioception weighting, influenced by the presence or absence of visual information, on dynamic posture control during voluntary trunk movements. We recorded trunk movement angle and angular velocity, center of pressure (COP), electromyographic, and electroencephalography signals from 35 healthy young adults performing a standing trunk flexion–extension task under two conditions (Vision and No-Vision). A random forest analysis identified the 10 most important variables for classifying the conditions, followed by a Wilcoxon signed-rank test. The results showed lower maximum forward COP displacement and trunk flexion angle, and faster maximum flexion angular velocity in the No-Vision condition. Additionally, the alpha/beta ratio of the POz during the switch phase was higher in the No-Vision condition. These findings suggest that visual deprivation affects cognitive- and sensory-integration-related brain regions during movement phases, indicating that sensory re-weighting due to visual deprivation impacts motor control. The effects of visual deprivation on motor control may be used for evaluation and therapeutic interventions in the future.

This study aimed to clarify the relationship between spine curvature and the movement pattern/motor control ability of the lumbar and hip joints during prone hip extension in elderly individuals. The participants were 14 elderly people who attended a community health class. We measured the motion angle, motion ratio (movement pattern), and motor control ability of the lumbar and hip joints during prone hip extension. In addition, the lumbar lordosis angle and thoracic kyphosis angle were measured in the standing position. There was no correlation between the spinal curvature in the standing position and the lumbar/hip joint movement pattern and motor control ability during prone hip extension. When evaluating the lumbar spine, it is necessary to perform a comprehensive evaluation by interpreting static evaluations such as spinal alignment or dynamic evaluations such as movement patterns and motor control abilities.

Objectives: To comprehensively examine the association between spinopelvic alignment and muscle shortening in healthy young men, focusing on the individual and interactive effects of thoracic kyphosis, lumbar lordosis, and anterior pelvic tilt using SHapley Additive exPlanation (SHAP) analysis. Methods: Forty-one healthy young adult men participated in this cross-sectional study. Thoracic kyphosis, lumbar lordosis, and anterior pelvic tilt were measured using a flexible curve ruler and inclinometer. Muscle length indices for six muscles (iliopsoas, rectus femoris, gluteus maximus, hamstrings, back extensors, and abdominals) were assessed via standardized physical examinations and image analysis. A machine learning model was developed, and SHAP analysis applied to determine individual and interactive contributions of spinopelvic angles to each muscle length index. Results: SHAP analysis showed that hip-related muscle shortening (iliopsoas, rectus femoris, hamstrings, gluteus maximus) was influenced by both individual alignments and interactions, especially between thoracic kyphosis and lumbar lordosis. Lumbar lordosis was most associated with iliopsoas shortening (SHAP = −0.09), while anterior pelvic tilt was linked to hamstring shortening (SHAP = −0.30). Thoracic kyphosis was the key factor for rectus femoris shortening (SHAP = −0.05). Interactive effects exceeded individual contributions for the rectus femoris, gluteus maximus, and hamstrings. In contrast, spinal alignment had minimal influence on the back extensors and abdominals. Conclusions: Both individual and intersegmental spinal alignments are associated with muscle shortening, particularly in hip-related muscles. The interaction between thoracic kyphosis and lumbar lordosis plays a pivotal role. These findings underscore the importance of evaluating segmental spinal interactions when assessing muscle flexibility and posture.

We investigated the effects of manipulating visual information on motor control indicators during the Waiter’s Bow Test. The results suggested that visual information occlusion reduced the maximum flexion angles of the lumbar spine and upper lumbar region. Furthermore, subjects who tested negative under the open-eye condition tested positive under the closed-eye condition. Regarding muscle activity in the rectus abdominis and erector spinae muscles, it was suggested that this activity was not affected by visual information. These findings indicate that visual sensory feedback is one factor influencing lumbar motor control. The integration of electromyography and accelerometer systems in this study highlights the role of wearable sensor technologies in quantifying neuromuscular function in Bioengineering. By restricting visual information, a model for sensory reweighting can be established for the design of biofeedback systems, rehabilitation robotics, and assistive devices. The results of this study demonstrate how sensor-based evaluation and sensory manipulation can inform the engineering of diagnostic and therapeutic technologies for motor control assessment.

Background and Objectives: Understanding the relationships between subjective shoulder stiffness, muscle hardness, and various factors is crucial. Our cross-sectional study identified subgroups of shoulder stiffness based on symptoms and muscle hardness and investigated associated factors. Materials and Methods: measures included subjective stiffness, pain, muscle hardness, and factors like physical and psychological conditions, pressure pain threshold, postural alignment, heart rate variability, and electroencephalography in 40 healthy young individuals. Results: Three clusters were identified: Cluster 1 with high stiffness, pain, and muscle hardness; Cluster 2 with low stiffness and pain but high muscle hardness; and Cluster 3 with low levels of all factors. Cluster 1 had significantly higher central sensitization-related symptoms (CSS) scores than Cluster 2. Subjective stiffness is positively correlated with psychological factors. Conclusions: our results suggest that CSS impacts subjective symptom severity among individuals with similar shoulder muscle hardness.