## 2 Materials and Methods
### Material  
The older participants were recruited from a group of University of the Third Age students. Initially, the study group consisted of 11 participants (8 women and 3 men). However, only 7 participants had complete results on three repeated gait measurements out of the individuals enrolled in this study. Exclusion reasons included balance maintenance issues (1 participant), fatigue or weakness (2 participants), and difficulties in using poles properly despite instructions (1 participant). Ultimately, the tests were performed on 7 older adults without a medical history of musculoskeletal injuries causing pain, weakness, decreased ROM, or loss of coordination (5 women and 2 men) aged 65 to 74 (the average age was 70.6), who finally qualified for the study with no comorbidities that could cause gait disturbances and were fit and healthy on the day of the study. They either did not participate regularly in NW classes or had limited experience with NW. The characteristics of the participants are presented in Table 1.  
The participants were informed about the aims and methodology used in the experiment and gave written informed consent to participate in the investigation. The experiment was approved by the local ethics committee and conducted in accordance with the Declaration of Helsinki.  
The participants were equipped with standard NW poles and mechatronic poles. All the poles were individually adjusted to the height of each person. In particular, the pole length was adjusted for flat terrain. Individually adjusting NW pole length involved several steps: (1) Standing up straight with arms relaxed at the sides. (2) Placing the poles on the ground with the handles pointing up. (3) Grasping the handles of the poles and lifting them off the ground. (4) Bending elbows at a 90-degree angle. (5) Adjust the poles' length until the forearms are parallel to the ground. Participants wore trainers or hiking boots during the experiment. Participants were instructed and trained in the principles of walking with NW poles and performed practice walks with an instructor. Before taking the measurements, all of them reported that they felt comfortable enough with the poles to take part in the study.  
The design of the mechatronic poles has been described in our previous studies [20,21]. In short: the classic NW poles have two nine-axis inertial sensors (a three-axis gyroscope, an accelerometer, and a magnetometer). The foot of the pole has a pressure sensor that measures the force along the axis of the pole, and the handle has a contact sensor. In addition, the pole also featured distance sensors, two optical and two ultrasonic, and one  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Participants’ Initials**} & \multirow{2}{*}{**Age (Years)**} & \multicolumn{2}{c}{**Body Height**} & \multirow{2}{*}{**Body Mass**} \\  & & **(cm)** & & **(kg)** \\ \hline \multicolumn{4}{c}{Women} \\ \hline P01 & 71 & 164 & 59 \\ P02 & 65 & 174 & 62 \\ P03 & 74 & 166 & 58 \\ P04 & 69 & 164 & 58 \\ P05 & 70 & 165 & 57 \\ Mean \(\pm\) SD & 69.8 \(\pm\) 3.3 & 166.6 \(\pm\) 4.2 & 58.8 \(\pm\) 1.9 \\ \hline \multicolumn{4}{c}{Men} \\ \hline P06 & 72 & 170 & 74 \\ P07 & 73 & 176 & 77 \\ Mean \(\pm\) SD & 72.5 \(\pm\) 0.7 & 173 \(\pm\) 4.2 & 75.5 \(\pm\) 2.1 \\ \hline \multicolumn{4}{c}{Legend: SD—standard deviation.} \\ \hline \hline \end{tabular}
\end{table}
Table 1: Characteristics of the study group.  
sensor of each type at the foot and handle. The conducted signal tests from the inertial, pressure, contact, and distance sensors confirmed sufficient accuracy for the study of gait biomechanics [20; 21].