## 3 Results and Discussion  
### Resistance to Multiple Bending and Twisting  
Organoleptic examination of the heating inserts after multiple bending and twisting cycles showed no damage to the knitted fabric or heating thread. It was found that variant B of the heating inserts was more durable than variant A. This was due to the use of an additional openwork knitted fabric in variant B, acting as a layer protecting the heating thread (Figures 7 and 8). Figure 6: Arrangement of thermocouples in the fabric system with heating function for protective clothing for mountain rescuers. \begin{table}
\begin{tabular}{c c} \hline \hline
**No.** & **Designation of the System** & **Arrangement of Layers in the Material System** \\ \hline \multirow{7}{*}{\(1\)} & & layer I (underwear fabric): knitted fabric U1 \\  & & (100\% PES), 131 g/m\({}^{2}\) \\  & & layer II: heating insert B \\ \cline{1-1}  & U1 + insert B + Z4 + W2 & layer II (for down jacket): down package made of \\ \cline{1-1}  & & \(Z\)4 fabric (100\% PA, 131 g/m2) with filling: \\ \cline{1-1}  & & 92\% goose down, 8\% feathers \\ \cline{1-1}  & & layer III (for outer jacket): vapor-permeable laminate \\ \cline{1-1}  & & W2 (fabric: 100\% PES, membrane: 100\% PU) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Material systems with heating insert for temperature distribution testing. As demonstrated in the study, a simulation of actual use in the form of forced bending and twisting cycles did not change the power and electrical resistance of the heating inserts (Table 6). The power of the inserts remained at approx. 2.1 W and was very similar for inserts without (variant A) and with an openwork fabric (variant B). In the case of insert A, no changes in electrical resistance were observed after bending and twisting; this parameter remained at the level of approx. 6.9 \(\Omega\). However, in the case of insert B, bending led to a slight increase in electrical resistance of approx. 5% from 6.89 \(\Omega\) for a new insert to 7.21 \(\Omega\) for an insert subjected to 9000 bending and twisting cycles. However, these differences were not significant. It can, therefore, be concluded that the electrical parameters of the inserts did not deteriorate as a result of multiple bending and twisting cycles. Studies by [PERSON] et al. [33], who examined knitted structures with stainless steel, have shown that heating elements made of similar stainless steel can generate a larger amount of heat at a very low voltage (1.5-3 V). [PERSON] et al. [33] noted that stainless steel yarn is recommended where a high heat output is required. These researchers found that the interlock structure was a better choice for heating fabrics due to its stability and also because it was observed to reach a higher temperature as compared to that of a plain structure for the same amount of voltage supplied. [PERSON] et al. [34] investigated the effect of bending cycles on the electrical resistance of conductive e-textiles coated with carbon black ink, designed for heating inserts. The material was subjected to 1000 bending cycles using the developed hand-operated system, in which a sample of material was placed on a wooden base. To summarize, bending was carried out with the help of the moving part. Electrical resistance was tested with a probe at two ends of the sample after every 100 bending cycles. The tests demonstrated that the electrical resistance of the material increased by as much as 327% after 1000 bending cycles. In the case of inserts tested in the presented study, electrical resistance, practically, did not change after such a number of bending cycles, which indicates their very high durability to mechanical damage. Figure 8: Photographs of the heating insert (variant B) after 9000 cycles of bending and twisting—outer surface (**a**) and inner surface (**b**). Figure 7: Photographs of the heating insert (variant A) after 9000 cycles of bending and twisting—outer surface (**a**) and inner surface (**b**).