Ridzuan et al. / Malaysian Journal of Fundamental and Applied Sciences Special Issue on Medical Device and Technology (2017) 509-514 509 Evaluation of muscle fatigue using infrared thermal imaging technique with assisted electromyography Nursyazana Ridzuan a , Aizreena Azaman b,c , Kamaruzaman Soeed c , Izwyn Zulkapri a , Asnida Abdul Wahab a,* a Department of Clinical Sciences, Faculty of Biosciences and Medical Engineering, 81310 UTM Johor Bahru, Johor, Malaysia b Sport Innovation Technology Center , 81310 UTM Johor Bahru, Johor, Malaysia c Department of Biotechnology and Medical Engineering , Faculty of Biosciences and Medical Engineering, 81310 UTM Johor Bahru, Johor, Malaysia * Corresponding author: asnida@biomedical.utm.my Article history Received 15 October 2017 Accepted 6 December 2017 Abstract Muscle fatigue in sports science is an established research area where various techniques and types of muscles have been studied in order to understand the fatigue condition. It can be used as an indicator for predicting muscle injury and other muscle problems which can decrease athletes’ performance. Muscle fatigue usually occurs after a long lasting or repeated muscular activity. Electromyography (EMG) assessment method is a standard tool used to evaluate muscle fatigue based on the signals from the neuromuscular activation during fatigue condition. However, additional time for equipment set up such as placement of the electrodes and the use of multiple wires make this overall setting a bit complicated. In addition, the signal from EMG which possessed some noise, need to be filtered and post processing time is also required to obtain a reliable measurement signal. Therefore, researchers have explored the application of thermal imaging technique as one of the alternative methods for muscle fatigue assessment. The objective of this study is to investigate the correlation of muscle fatigue condition measured using a non-invasive infrared thermal imaging technique and a standard evaluation method, EMG. Five healthy men were selected to run on a treadmill for 30 minutes with a constant speed setting. Temperature and EMG signals were registered from gastrocnemius muscle of the subjects' dominant leg simultaneously. Result obtained shows that the average temperature of gastrocnemius muscle decrease as subjects start to exercise. Further temperature decrease along with exercise and increase in temperature were observed during the recovery period. Statistical analysis was performed and analyzed using both temperature and EMG parameters. Result shows a significant strong correlation with r = 0.7707 and p < 0.05 between temperature difference and median frequency (MDF) for all subjects compared to average temperature. Therefore, it is concluded that temperature difference extracted from thermal images can be used as an ideal parameter for muscle fatigue evaluation. Keywords: Muscle fatigue, thermal imaging, muscle injury, thermoregulation © 2017 Penerbit UTM Press. All rights reserved INTRODUCTION Muscle fatigue in sports science is a condition when there is a transient decrease in contractile strength and capacity to perform physical actions. Muscle fatigue occurs after a long lasting or repeated muscular activity. During this phase, the capacity of muscle to produce maximum voluntary action or to perform a series of repetitive actions is reduced (Hadžić et al., in press). For athletes, muscle fatigue plays a crucial role since it limits their performance in sport. Muscle fatigue can be used as a good indicator to prevent a person from having other musculoskeletal diseases (MSD) such as muscle injury and thus, it is important to assess muscle fatigue condition in its early phase (Al- Mulla et al., 2011). According to Bartuzi et al. (2012) the most common and leading method since 1980s in assessing muscle fatigue in sports science is by using electromyography (EMG). This method is used to estimate fatigue by quantifying electrical signals sent to muscle fibers through motor neurons during muscle activation. EMG is a diagnostic procedure to assess muscle health and the nerve cells that control the muscle (motor neurons). This motor neurons transmit electrical signals that cause muscle to contract. EMG uses electrodes to transmit or detect electrical signals from the muscle. In accessing muscle load and fatigue during an occupational task, the electrical signal from a surface electrode is commonly used (Merletti et al., 2009). Although EMG is the current preferred method for muscle fatigue, factors such as various sources of noise acquired with the signal such as electromagnetic noise, transducer noise, power line noise, and motion noise limit its performance (Al-Mulla et al., 2011). Moreover, measurement of EMG signal will require additional time for equipment set up and proper placement of the electrodes. In addition, post processing time is also needed for noise filtering in the signals. EMG also has the limitation in detection of low level of muscle contraction (Kallenberg and Hermens, 2008). Therefore, researchers have started to look for a reliable and better alternative method for muscle fatigue detection and prediction such as by using non-invasive infrared thermal imaging (Al-Mulla et al., 2011). In any physical activities, heat is lost to the environment via convection and evaporation during respiration process. Based on the RESEARCH ARTICLE