Biomedical Engineering Letters

, Volume 8, Issue 4, pp 345–353 | Cite as

Electromyography-signal-based muscle fatigue assessment for knee rehabilitation monitoring systems

  • Hyeonseok Kim
  • Jongho Lee
  • Jaehyo KimEmail author
Original Article


This study suggested a new EMG-signal-based evaluation method for knee rehabilitation that provides not only fragmentary information like muscle power but also in-depth information like muscle fatigue in the field of rehabilitation which it has not been applied to. In our experiment, nine healthy subjects performed straight leg raise exercises which are widely performed for knee rehabilitation. During the exercises, we recorded the joint angle of the leg and EMG signals from four prime movers of the leg: rectus femoris (RFM), vastus lateralis, vastus medialis, and biceps femoris (BFLH). We extracted two parameters to estimate muscle fatigue from the EMG signals, the zero-crossing rate (ZCR) and amplitude of muscle tension (AMT) that can quantitatively assess muscle fatigue from EMG signals. We found a decrease in the ZCR for the RFM and the BFLH in the muscle fatigue condition for most of the subjects. Also, we found increases in the AMT for the RFM and the BFLH. Based on the results, we quantitatively confirmed that in the state of muscle fatigue, the ZCR shows a decreasing trend whereas the AMT shows an increasing trend. Our results show that both the ZCR and AMT are useful parameters for characterizing the EMG signals in the muscle fatigue condition. In addition, our proposed methods are expected to be useful for developing a navigation system for knee rehabilitation exercises by evaluating the two parameters in two-dimensional parameter space.


Muscle fatigue Knee rehabilitation EMG signals 


Compliance with ethical standards

Conflict of interest

The authors declare that there is no conflict of interest regarding the publication of this paper.

Ethical statement

All the subjects provided written informed consent prior to participation. The experimental protocol was approved by the ethics committees of Handong Global University and was conducted in accordance with the ethical standards outlined in the Declaration of Helsinki.

Supplementary material

13534_2018_78_MOESM1_ESM.docx (12 kb)
Supplementary material 1 (DOCX 12 kb)


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Copyright information

© Korean Society of Medical and Biological Engineering and Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Information and Communications EngineeringTokyo Institute of TechnologyYokohamaJapan
  2. 2.Department of Clinical Engineering, Faculty of Health SciencesKomatsu UniversityKomatsuJapan
  3. 3.Department of Mechanical and Control EngineeringHandong Global UniversityPohangRepublic of Korea

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