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

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.