Comparison of SEMG Derived Parameters and Blood Oxygen Saturation in Monitoring Neuromuscular Fatigue in Humans

Comparison of SEMG Derived Parameters and Blood Oxygen Saturation in Monitoring Neuromuscular Fatigue in Humans

M. Tarata (Department of Medical Informatics, University of Medicine and Pharmacy of Craiova, Craiova, Romania), W. Wolf (Universität der Bundeswehr München, Neubiberg, Germany), D. Georgescu (Department of Medical Informatics, University of Medicine and Pharmacy of Craiova, Craiova, Romania), D. Alexandru (Department of Medical Informatics, University of Medicine and Pharmacy of Craiova, Craiova, Romania) and M. Serbanescu (Department of Medical Informatics, University of Medicine and Pharmacy of Craiova, Craiova, Romania)
DOI: 10.4018/ijmstr.2013100102

Abstract

The effects of neuromuscular fatigue are various and with serious consequences on work performance and safety. This paper provides a practical overview of several noninvasive methods of investigating neuromuscular fatigue (NMF), mainly via the surface electromyographic signal (SEMG), as essentially related to the muscle contraction and intimately mirroring muscle activation and contraction mechanisms. The purpose of this paper is to identify the most suitable non-invasively derived parameters for detecting and quantifying NMF, to be practically used in monitoring people exposed to high risks, such as fighter pilots. Wavelet Transform-based techniques (WT), as well as another original approach, together with the blood oxygen saturation are analyzed and discussed, based on results from preliminary experiments.
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Introduction

Neuromuscular fatigue (NMF) in pilots and other high risk, high performance professions (train drivers, race drivers, even long distance truck drivers, professional or recreational divers) is a cause of real concern, due to its impact on the capabilities of the involved personnel to correctly and safely execute work tasks. All the above professions involve the adjustment of the body to rapid shifts in acceleration and direction, or exposure to long-term higher forces/ pressure, which wear off postural muscles.

Because of the high risks and costs involved by flight under special conditions, many papers explored NMF in pilots on different military aircraft (Ang, 2006; Caldwell, 2005; Green, 2004; Netto, 2006; Thuresson, 2005). In these studies, the muscular groups affected to a greater extent by the limit conditions that flight implies (neck, back, leg and hand muscles) were studied to describe different aspects of fatigue, both in on-ground and in-flight experiments.

The results confirmed the installation and development of fatigue in all studied muscles, but faster and to a greater degree in the neck muscles (Ang, 2008). The development of fatigue is affected by the pilot’s helmet, even more because the weight of the helmet increased in the later years with the addition of new technologies and equipment.

The power and resistance in the neck muscles are very important in fighter and test pilots, therefore extreme attention has to be paid to the recovery following the mission, otherwise the efficiency of the subject decreases and the risk of accidents increases significantly. Cervical injury is directly related to fatigue in the neck muscles, which involve mostly the Trapezius (TR) and Sternocleidomastoid (SCM) muscles (Ang, 2006). These are accessible for surface electromyography recordings.

The purpose of this paper is to identify the most suitable non-invasive method and parameters for detecting and quantifying NMF, to be practically used in monitoring people exposed to high risks, such as fighter pilots. Wavelet Transform-based techniques (WT) and derived parameters, as well as other original approaches, are analyzed, illustrated and discussed, based on results from preliminary experiments.

Materials and Methods

In the actual study we used the SEMG-derived parameters and blood oxygen saturation, non-invasively acquired with surface electrodes and ear pulse-oximeter transducer, respectively.

We monitored SEMG due to its ability to show the installation and development of NMF through its spectral compression to lower frequencies and the blood oxygen saturation (SaO2) because of its role in maintaining proper physical/muscular activity.

Under these premises, to quantitatively monitor the neuromuscular fatigue and to compare methods, we recorded the SEMG together with the SaO2.

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