ANTI-FATIGUE UNIT (AFU)
AFU, or pulse splitter, is a device that distributes pulses asynchronously from one input to four outputs. Each pulse from the input is distributed to only one output in a shuffling manner.
AFU is power supplied from the stimulator battery via audio cable, but it can also be supplied externally with coin batteries. It can be used with any other stimulator if the following limits are met:
- pulse amplitude: 0-170mA,
- pulse width (PW): 50-1000us,
- frequency (F): 1-500Hz,
- where PW * F ≤ 0.025.
AFU mimics the natural activation of a muscle to reduce FES-induced muscle fatigue. The asynchronous stimulation of different branches of a nerve innervating the same muscle or synergistic muscles via several electrodes at a lower frequency (≈10-15Hz) results with the fused contraction with the comparable force to the one generated with single large electrode activated at higher frequency (≈40–50 Hz); yet, postpones the muscle fatigue for several times. This phenomenon was confirmed in several clinical studies (see publications).
- Popović-Maneski L, Malešević N, Savić A, Keller T, Popović DB. Surface distributed low-frequency asynchronous stimulation (sDLFAS) delays fatigue of stimulated muscles. Muscle & Nerve, 2013, Vol 48(6), pp.930-937, DOI: 10.1002/mus.23840.
- Malešević, L. Popović, L. Schwirtlich and D.B. Popović, Distributed low-frequency functional electrical stimulation delays muscle fatigue compared to conventional stimulation, Muscle and Nerve, 2010, pp. 42(4): 556-562, DOI 10.1002/mus.21736.
- Popović, L.Z., and Malešević, N.M. "Muscle fatigue of quadriceps in paraplegics: comparison between single vs. multi-pad electrode surface stimulation." In 2009 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2009, pp. 6785-6788.