EP 92. Measuring force in fingertapping: A novel tool to detect motor fatigue

• Published in: Clinical neurophysiology 2016-09, Vol.127 (9), p.e282-e282
• Main Authors: Rönnefarth, M, Bathe-Peters, R, Jooß, A, Haberbosch, L, Brandt, S, Schmidt, S
• Format: Article
• Language: English
• Subjects: Neurology
• ISSN: 1388-2457; 1872-8952
• DOI: 10.1016/j.clinph.2016.05.140

Introduction The Fingertapping-task (FT) is a simple tool to evaluate complex aspects of motor function in a clinical as well as research setting. FT provides information about motor function and deterioration (Shimoyama, 1990). FT tapping rate (FT-speed) is recorded as a correlate for performance with reduced rates corresponding to a decline of function. Motor fatigue (MF) is usually studied by employing a maximum voluntary contraction task and decline of function is defined as reduced force output. Yet, there are few studies focusing on motor fatigue in more complex (repetitive) motor tasks like FT and modified FT-force. We hypothesize reduced FT-force in a standard FT-task will reflect task specific motor fatigue providing additional information to FT-speed. Methods We recorded the FT-force in healthy subjects in a standard FT-task (right and left first dorsal interosseous (FDI), 30 s repetitive sessions) via a morse key equipped with a 1 N force sensor. We hypothesized that as a correlate for motor fatigue the FT-speed and FT-force would decline over time. Results From the continuous force signal data FT tap-intervals were derived and compared to FT tap-intervals defined by a closed circuit (morse key). Results show a very high reliability (intraclass correlation coefficient 0.98). A significant decrease of FT-speed over time in the respective session (intrasession) was seen ( p < 0.01 ), that was more prominent in the non-dominant hand. A significant enhancement in FT-force over time was seen within and between FT sessions ( p < 0.01 ). This effect was more prominent in the non-dominant hand. Surprisingly, the effects of FT-force and FT-speed were not correlated. Discussion We could show that the assessment of tapping force in the standard FT-task provides additional novel information about motor fatigue not only within, but also between FT-task sessions, that is clearly independent of FT-speed. The increase in FT-force seems counterintuitive, yet is in line with previous definitions of motor fatigue (Edwards, 1980) when interpreted as a correlate for increasing effort and central compensatory mechanisms. Measuring the FT-force in a standard FT-task is a novel and easy to use tool, which might reflect central compensatory mechanisms, could be used in a clinical setting to detect early symptoms of fatigue in various disease entities and we believe deserves further investigation and neurophysiological characterization.