**Author details**

Computational Intelligence in Electromyography Analysis – 92 A Perspective on Current Applications and Future Challenges

conflicting (Perry 1992): more cushioning brings less stability.

those findings respect to the TA and the ST; but not for the BF.

shod condition, there is more damping of the impact force. Cushioning and stability are

Nigg et al. (2003) speculated that the body reacts to changes in input signal to adapt the muscle activity to reduce the vibrations of the soft tissues. In principle, the proximal muscles would be less required than the distal ones. These authors found that the TA activity increased more than that of the proximal ones (BF and ST). Our results are consistent with

According to Mundermann et al. (2003), changes in the intensity of leg muscles activity predict better the differences in comfort than changes in the impact force. As the muscle activity decreased in the stance phase, the kinematic differences between the conditions disappeared (De Wit et al. 2000). This result is consistent with the absence of muscle activity. The signal amplitude indicates the level of activation of the muscle: there is a relationship between activity and strength, implying that increased activity is the source of increased muscle strength. The change in muscle electrical activity may be due to the role of the

According to Arsenault et al. (1987), it seems clear that the kinematics of locomotion is not very variable. From the scientific literature one can obtain the parameters describing the movement and explain muscle activity during jogging in different conditions. When the peak of the RF, VM, GN, BF, and ST muscles appears, the hip stretches, the knee flexes, and the ankle flexes dorsally. Rectus femoris and VM undergo an eccentric contraction, BF and ST concentric, and GN concentric in the knee and eccentric in the ankle. Biceps femoris and GN promote the flexing of the knee and the GN transfers energy from the ankle to the knee. The activation of the muscles acting as antagonists (i.e., contracting eccentrically) promote the absorption of energy recovered in the immediate concentric contraction. In the condition barefoot, the BF presented electrical activity at the end of the swing phase, in the final flight, and at the onset of stance phase, acting first as antagonist and then as agonist. With shoes, the activity increased in both phases, increasing the energy absorbed in the non-support phase. During the concentric contraction at the beginning of the stance phase, the increased activity means more power generation. The increase of the absorbed energy and the energy produced could be interpreted as an effort at the beginning of the stance phase in order to do hip extension, perhaps to counterbalance the increased frictional force that opposes the advance in the shod condition. At the beginning of the support phase, the GN, RF, and VM are active in eccentric contraction. The reduction of the duration of the support phase in the

muscles to adapt to the characteristics of elasticity and friction of the shoes used.

shod condition may improve the efficacy of the stretching-shortening cycle.

In any case, cross-talk cannot ever be fully cancelled.

The potential problem of crosstalk was reduced using a double differential technique, which is based on a single amplifier fed with three electrodes (De Luca & Merletti, 1988; Winter, 1990; Winter et al., 1994). It is already widely accepted that double-differential technique reduces the level of cross-talk (see, *e.g.*, De Luca & Merletti, 1988; and Meinecke et al., 2004).

As the human body is a biological system that has many possibilities of action and reaction, it would be advisable to evaluate the electrical activity of other additional muscles when Begoña Gavilanes-Miranda *Faculty of Physical Activity and Sport Science, University of Basque Country, Vitoria, Spain* 

Juan J. Goiriena De Gandarias *Faculty of Medicine, University of Basque Country, Bilbao, Spain* 

Gonzalo A. Garcia\* *Biorobotics Department, TECNALIA, Bilbao, Spain* 

<sup>\*</sup> Corresponding Author
