Non-invasive detection of low-level muscle fatigue using surface EMG with wavelet decomposition.

Median frequency (MDF) is widely used for detection and tracking of muscle fatigue using surface electromyography (sEMG). However, MDF does not behave consistently or accurately distinguish fatigued from non-fatigued states. In this paper, we study the concept of low-level fatigue and propose increasing average ratio (IAR) and trigger pattern index (TPI) based on discrete wavelet transform (DWT) for distinguishing low-level muscle fatigue. We recorded sEMG using an 8-electode linear monopolar array during isometric contractions from brachioradialis (BRD), biceps brachii long head (BBL), and biceps brachii short head (BBS) muscles of different subjects when performing force exertion. We then calculated the proposed parameters for characterizing low-level fatigue. The analysis indicated that the proposed approach is more consistent and stable when distinguishing low-level muscle fatigue and sheds light on the behavior of sEMG in frequency domain with respect to low-fatigue force exertion.

Additivity in perception of affect from limb motion.

In this study, the notion of additivity in perception of affect from limb motion is investigated. Specifically, we examine whether the impact of multiple limbs in perception of affect is equal to the sum of the impacts of each individual limb. Several neutral, happy, and sad walking sequences are first aligned and averaged. Four distinct body regions or limbs are defined for this study: arms and hands, legs and feet, head and neck, and torso. The three average walks are used to create the stimuli. The motion of each limb and combination of limbs from the neutral sequence are replaced with those of the happy and sad sequences. Through collecting perceptual ratings for when individual limbs contain affective features, and comparing the sums of these ratings to instances where multiple limbs of the body simultaneously contain affective features, additivity is investigated. We find that while the results are highly correlated, additivity does not hold in the classical sense. Based on the results, a mathematical model is proposed for describing the observed relationship.