**2.1. Subject**

Computational Intelligence in Electromyography Analysis – 54 A Perspective on Current Applications and Future Challenges

determines the neuromuscular fatigue process.

force of contraction of the fatigued fibers [13,18].

recruitments, force produce and gender influence [20].

frequency values of the power spectrum of sEMG [22].

levels or using ramp contractions.

muscle fibers.

Research by [15] Dimitrova & Dimitrov (2002) related that Muscle fatigue is recognized as a decline in force, or failure to maintain the required or expected force. It may occur at any point from the nervous centers and conducting pathways to the contractile mechanism of

Study by [16] Moritani & Yoshitake (1998)Such changes have been shown to be related to hydrogen ion and metabolite accumulation and to sodium and potassium ion concentration shifts. These changes would in turn affect the muscle excitation traction coupling including the muscle membrane properties and muscle action potential propagation, leading to sEMG

The increase in amplitude of the sEMG signal as an empirical measure of localized muscle fatigue or as an indicator of muscle fatigue [9,17]. The RMS-sEMG values tended increase with decreasing force as a function of the number of repetitions [6] phenomenon that

The active motor units also discharge with increasing speed to compensate for the fall in the

The surface electromyography behavior at different force levels is of particular importance. This can be either achieved by performing multiple isometric contractions at various force

A ramp contraction is defined as a progressive linear increase in force over time and relationships sEMG-force is linear or quadratic [19], and then, sEMG parameters and phsyiologicasl events used ramp contraction in investigation, as well, motor unit

Study by [19] Bilodeau et al (2003), [20] Pérot et al (1996) and [21] Stulen and DeLuca (1981) related the relationship of curve in ramp contraction were this behavior can be confirmed between of recruitment of large, type II muscles fibers, with a higher muscle action potential conduction velocity, is associated with an increase in the median frequency or mean power

In the decade 80 researches showed that the ramp contraction procedure might be replaced by procedure comprising a number of distinct and constant force contraction. Ramp contractions involve the registration of sEMG while the strength performance gradually increases his or her level of effort up to maximal or submaximal levels. Although the latter procedure seems to be easier to use in some investigation, the ramp procedure has gained a wider acceptance since then. They have been extensively applied to examine muscle

activation strategies as well as in new protocols of electromyography analysis. [19,23]

*femoris caput longum* (BFCL) all of which are active during knee flexion.

The purpose of the present study was to investigate the relationships of sEMG and time during isometric strength ramp contraction in the hamstrings muscle group. Hamstrings muscle group is composed of the *semitendinosus* (ST), *semimembranosus* (SM) and *biceps* 

manifestations of muscle fatigue distinct from mechanical manifestations.

Twenty female healthy adults (age 19.5 ± 0.8 yrs, body mass 63.4 ± 1.5 kg, height: 1.65 ± 0.05 m), without muscle skeletal disorders and similar anthropometric measurement, subject in this study. Subjects were all right leg dominant. All subjects signed a written informed consent. The study was approved by the AESA Ethics Committee protocol 344/10.
