**2.6. Statistical analysis**

The influence of footwear on speed, the phases of locomotion, right-left legs symmetry, general effort, and on the maximum amplitude of the EMG activity of the 12 target muscles was evaluated by analysis of variance (ANOVA) for one factor with the statistical package of Matlab (The MathWorks, Massachusetts, USA), using the following factorial model: footwear, with three levels (barefoot, shod with standard shoes, and shod with athletic shoes). The statistic F has been analyzed and the significance level considered was p <0.05.

#### **3. Results**

The aim of our study was to evaluate the influence of footwear on the electrical activity of muscles of both legs when jogging barefoot and jogging with two types of footwear featuring different geometry and damping characteristics. The barefoot condition was interpreted as the one in which the external protection and shock reduction at the beginning of the stance phase were minimal. The standard shoe was harder than the athletic one, cushioning less the impact.

For the realization of this goal we propose more specific objectives: to determine the profile of the muscle electrical activity and the order of muscle participation, to detect changes in the amplitude of the electrical signal muscles, and to measure the level of coactivation of antagonistic muscles. The different phases of the gait cycle were measured based on the records obtained by the pressure sensors (see **Figure 1**) located under the foot or shoe sole.

**Figure 1.** Bilateral support and non-support patterns from each foot obtained with pressure sensors.

The speed was higher when jogging with the own athletic shoes, and of a similar magnitude when jogging barefoot than when using standard sneakers. **Figure 2** shows the mean values of the speed and, for both legs, the mean values of the phases of: support, non support, and double flight. When running shod, the duration of the phases of the stride was different with respect the barefoot condition. The stance phase was shorter and the non-support phase, longer. The time length of the double flight increased. Between the two types of footwear used (standard and athletic) there were differences in speed but not in phases.
