Abstract
Excessive muscle tension is implicitly caused by inactivity or tension in daily activities, and it results in increased joint stiffness and vibration, and thus, poor performance, failure, and injury in sports. Therefore, the routine measurement of muscle tension is important. However, a co-contraction observed in excessive muscle tension cannot be easily detected because it does not appear in motion owing to the counteracting muscle tension, and it cannot be measured by conventional motion capture systems. Therefore, we focused on the physiological characteristics of muscle, that is, the increase in muscle belly cross-sectional area during activity and softening during relaxation. Furthermore, we measured muscle tension, especially co-contraction and relaxation, using a DATSURYOKU sensor, which measures the circumference of the applied part. The experiments showed high interclass correlation between muscle activities and circumference across maximal voluntary co-contractions of the thigh muscles and squats. Moreover, the circumference sensor can measure passive muscle deformation that does not appear in muscle activities. Therefore, the DATSURYOKU sensor showed the potential to routinely measure muscle tension and relaxation, thus avoiding the risk of failure and injury owing to excessive muscle tension and can contribute to the realization of preemptive medicine by measuring daily changes.
Highlights
The rapid aging of the population and declined birthrates as well as advanced medical technology and increased medical requirements have rapidly increased medical costs and demand for nursing care
To avoid an increase in demand for nursing care and the burden of medical costs, the motor system for diseases caused by the decline in physical and cognitive functions and daily exercise habits associated with aging should be improved to enable people to live independently for a longer period and extend their health span
The circumference is believed to decrease owing to the tightening force applied by the sensor. These results indicate that the DATSURYOKU sensor can measure muscle tension and co-contraction that do not appear in motion, as well as passive deformation of muscles that do not appear in muscle activity
Summary
The rapid aging of the population and declined birthrates as well as advanced medical technology and increased medical requirements have rapidly increased medical costs and demand for nursing care. Protecting the lives of the elderly and their families as well as coping with the rising burden of medical costs are becoming major issues To address these issues, a new direction of medicine has been proposed as preemptive medicine, which aims to diagnose and predict diseases with a certain probability, and to provide therapeutic intervention in the early stage of disease onset, when there are no clinical symptoms and no abnormalities in the usual examination findings [1]. To avoid an increase in demand for nursing care and the burden of medical costs, the motor system for diseases caused by the decline in physical and cognitive functions and daily exercise habits associated with aging (as typified by the decline in walking ability owing to pain and dullness of knee joints, such as knee osteoarthritis) should be improved to enable people to live independently for a longer period and extend their health span. Preemptive medical treatment for diseases related to such motor functions requires diagnosis and prediction in the early stages of disease onset based on changes in the state of cardiopulmonary and musculoskeletal functions as well as daily exercise, and routine measurement of this information is essential
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