Proprioceptive coordination of movement sequences in humans

Objective To estimate the processing time and neuromuscular delay required to extract and process sensory information from the ankle in order to coordinate an upper extremity movement sequence. Methods Nineteen able-bodied subjects were tested on their ability to perform a motor task that involved extension of their left index finger when their left ankle was passively plantar flexed at random velocities through a predetermined target angle. Results We found that the able-bodied subjects were able to adjust their finger responses up to ankle velocities of 70°/s (300 ms). Reaction time, defined as the delay between onset of ankle rotation and how quickly the index finger could be extended, was 215 ms. The processing time and conduction delay was estimated to be 85 ms. Conclusions These results indicate that the nervous system processes kinesthetic input related to joint rotation of the ankle with the central mechanisms to execute a planned coordinated task with the upper extremity. Significance The time required to process proprioceptive information from the leg to perform a coordinated task with the upper extremity may vary throughout the lifespan. Understanding the effects of age, exercise, or injury on proprioceptive processing time may have important clinical implications