Underwater walking is one of the most common hydrotherapeutic exercises. Therefore, understanding muscular control during underwater walking is important for optimizing training regimens. The effects of the water environment on walking are mainly related to the hydrostatic and hydrodynamic theories of buoyancy and drag force. To date, muscular control during underwater walking has been investigated at the individual muscle level. However, it is recognized that the human nervous system modularly controls multiple muscles through muscle synergies, which are sets of muscles that work together. We found that the same set of muscle synergies was shared between the two walking tasks. However, some task-dependent modulation was found in the activation combination across muscles and temporal activation patterns of the muscle synergies. The results suggest that the human nervous system modulates activation of lower-limb muscles during water walking by finely tuning basic locomotor muscle synergies that are used during land walking to meet the biomechanical requirements for walking in the water environment.
Here we report an acute effect of aquatic pole walking (PW) training intervention on a 64-year-old male patient with chronic hemiparesis and symptoms of spasticity in the right lower limb. A comparison of over ground walking before and after 20 minutes of aquatic PW training revealed a significant improvement in gait performance. As a main result, the average speed of walking after the intervention was 0.16 m/s after the intervention as compared to 0.04 m/s in the initial condition. The time taken for each stride cycle was drastically decreased, mainly due to shortening of the stance time. Underlying the improved gait performance was the emergence of functional muscle activity in the paralyzed and spastic leg muscles. The result observed in this patient should be further tested among a large population of patients presenting similar symptoms. Moreover, the basic mechanisms underlying aquatic PW intervention should be further elucidated.
To provide a safer sitting environment for wheelchair users, it is important to quantitatively measure the forces acting on the contact surface between the seat and the person in the wheelchair. In addition to the pressure acting on the buttocks, shear forces have received particular attention in recent years; however, measuring shear force is more difficult than measuring pressure. To obtain this measurement, a thin and flexible sensor that can be used in a natural state on a wheelchair is needed. Therefore, we constructed a measurement system using our previously developed wearable sheet-type sensor (0.9 mm thick). In this study, preliminary tests were conducted using human dummies before testing on humans. Sensors were placed in four locations on the humanoid dummy’s back and buttocks, and the electric wheelchair was tilted and reclined five times each. The results showed that the sensor output pattern was reproducible and valid enough to proceed to the next step. However, the shear force in the internal and external directions was greater than expected, which indicates that the equipment and testing methods must be reviewed. On the basis of the results obtained in this preliminary study, preparations will be made for testing on human subjects.
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