The Multiplexed Device for Hoffmann Reflex Detection

A study is presented on the design of compact-sized signal distribution device for Hoffmann reflex methodological applications in sports medicine. This work is aimed at improving the reliability of H-reflex measuring and recording technique for the purpose of reducing inaccuracies introduced to data obtained because of the conventional methodological approach. Inaccuracies due to changes in subject muscle geometry and body part positioning were considered, and the method was devised to expand the stimulus signal delivery channels to cover the entire limb length. Expanded output channels were achieved through a designed signal distribution device that offers low impedance (≤ 150 mΩ), low power dissipation (≤ 200 mW), low inductance (≤ 1.00 mH), and low resistance (≤ 100 mΩ) signal travel path. The device was tested with a 5 V input signal; data obtained establishes the minimum effective signal processing speed for the device to be 20 ms. This processing time is lower than the required processing speed (100 ms); hence, the distributed stimulus was effectively distributed through the output channels of the designed device. Device performance was evaluated in a simulated environment by testing real electric stimulus from a constant current stimulator at both minimum current amplitude (1 mA), voltage amplitude (100 V), pulse duration (50 μs) and maximum current amplitude (10 mA), voltage amplitude (400 V), pulse duration (2 ms) tested on simulated human body resistance, and response at each setting monitored on an oscilloscope. Results obtained confirm all expectations, as the designed device was able to deliver electric stimulus to the simulated human body resistance set up with minimum signal propagation delay at 75 mΩ average resistance. Incorporation of the designed multichannel devices in the methodological delivery of stimulus to human muscle was established to significantly improve the reliability of response data obtained.