## 1 Introduction  
Human gait kinematic and spatio-temporal parameters change with age [1, 2, 3, 4]. In particular, there is a reduction in the range of motion (ROM) in the joints of the limbs and spine and reduced muscle activity when walking. The time for double support is longer, the stride length is shortened, and the stride width is increased. Also, the walking speed is reduced by around 0.8-1.2 m/s, and the gait cadence is increased [1, 2, 5, 6], related to a safer walking strategy, limiting the risk of losing balance and, consequently, dangerous falls in older adults [7]. These changes are associated with the involution of the musculoskeletal system, including muscle weakness, limited ROM in the joints, and poorer coordination and stability of body posture. They can also be affected by diseases more common in old age. For older adults, gait is an activity that requires good balance control. It decreases with age, resulting in changes in the gait pattern and limiting the duration of the phases and gait cycles associated with gait disturbance [1; 8; 9; 10]. There is also an additional phenomenon occurring in the gait. Age is associated with more significant intra-individual gait variability for most gait measures [3; 6], which may severely influence the power of statistical tests while investigating different gait patterns. Nordic walking (NW) has been suggested as a method for preventing degenerative changes and increasing the functional effectiveness of the musculoskeletal system, influencing older adults' gait [11]. Using poles while walking increases the ROM in the joints of the limbs and the involvement of muscles, especially the upper limbs [12]. In older individuals, NW resulted in longer strides and increased times of both double and single support compared to walking freely (without poles). During the NW gait, these people also had a lower walking speed and reduced step rate [13]. The literature demonstrates that NW reduces the load of the lumbar spine and lower limb joints and increases energy expenditure in comparison with recreational walking in older adults [14]. In addition, the beneficial effects of NW on different health parameters, such as resting heart rate, blood pressure, exercise capacity, and maximal oxygen consumption, have been established in elderly populations [15; 16]. Other studies report improvements in muscle strength and flexibility in both upper and lower limbs along with enhanced general endurance among healthy older adults [17; 18]. It should be emphasised that studies on the NW gait pattern among older people are sparse. Most concern the gait examination of pathological gaits or the use of NW during rehabilitation [11]. Having the correct walking technique with poles is essential to achieve the benefits of NW. With classic poles, learning this technique is difficult, especially for older adults. Mastering the correct gait style would be easier with the help of poles that are equipped with systems analysing the kinematic and spatio-temporal parameters of the gait in real time, informing the user about any gait abnormalities through a voice or light signal [19]. The paucity of studies on such systems necessitates further research [19]. In light of the results from other researchers and our prior observations, a model of NW mechatronic poles (classic NW poles equipped with sensors analysing the biomechanics of gait) was developed, which would allow for feedback on the NW gait technique with the possibility of its correction in real time [20]. In the mobile system of mechatronic NW poles, we have developed measures, records, and processes for selected kinematic values that allow for the assessment of the correctness of gait during NW walking in field conditions. The sensors are placed in the poles and in special inserts placed in the shoes. The measurement system is equipped with the necessary data recorders and user interfaces so that the acquired information can be easily analysed.