## 4 Discussion  
According to the spatio-temporal analysis results shown in Table 1, and by taking the barefoot case as a reference, we affirm that as the heel height increased, the steps shortened and, consequently, so did the gait cycle length; however, cadence was not apparently affected. These results align with the findings provided by several other authors [42; 43; 44; 45], and confirm the validity of our measuring method for spatio-temporal parameters.  
The angles of action at the tibotalar and metatarsophalangeal joints can be described as curves that are a function of the gait cycle over time. These can be represented by wavy lines with variable amplitudes and irregular periods. However, generalized shapes can be found in a statistically averaged scenario (Figures 4 and 5) and can, therefore, be used to find their angles, among other parameters [5; 7; 19; 42].  
Focusing on tibiotalar joints (Figure 4) under the barefoot conditions, the obtained results agree with several authors' findings [11; 19]. [PERSON] analyzed gait from a kinematic, kinetic and electromyographic point of view, and observed how dorsiflexion reached a maximum angle of \(8^{\circ}\), which occurred in the stance phase, and plantar flexion had a minimum angle of only \(-20^{\circ}\) immediately after take-off, with a total RoM of \(28^{\circ}\)[11]. [PERSON] et al. [3] evaluated changes in electromyographic (EMG) activity of the lower limb muscles, and hip, knee and ankle kinematics during gait while wearing low-(4-cm) and high-heeled (10 cm) shoes in young and middle-aged adult women, and found that the mean RoM values at ankle joints for barefoot participants were around \(25^{\circ}\) for middle-aged women and \(29^{\circ}\) for young women, which falls in line with our findings.  
[PERSON] et al. [19] did not monitor ankle joints, but worked with hallux dorsi/plantar flexion angles, and reported that they ranged from \(-8.68\pm 1.13\) (plantar-flexion) to \(22.55\pm 1.62\) (dorsiflexion) during the full cycle. Once again, this finding falls in line  
Figure 5: Metatarsophalangeal joint kinematics on the sagittal plane (\({}^{\circ}\)) during a full gait cycle for heel heights 0, 2, 6 and 10 cm.  
with our results. These findings support the validity of the measuring procedure and suggest that it can be used for other heel heights.  
The present study revealed that as heel height increased, the RoM at ankles considerably narrowed, and this finding also agrees with other authors' previous findings [3]. [PERSON] et al. [46] investigated whether a graded response in gait kinematics, kinetics, and EMG occurs as shoe heel height increases, and found that ankle plantar flexion increased while wearing high heels, which was also observed herein. This falls in line with the findings of [PERSON] et al. [3], who observed that the angles at ankles increased when heels contacted the ground, with a significant effect when the heel height increased. Regarding the ankle angle, it appears that wearing high heels forces the foot into a more plantar flexed position. Therefore, the ankle angle is noticeably different in the initial stance phase and after toe off [6].  
When centering on metatarsophalangeal joint kinematics (Figure 5), RoM notably narrowed with increasing heel height, which was also previously reported [18]. On the values obtained for joint dorsiflexion angles, the scientific literature is, as far as the authors know, inexistent for the 2 cm and 10 cm high heels, but the values presented here for barefoot and 6 cm high heels fall in line with other authors' findings [18].