## 4 Discussion
These ergonomic differences in body placement may partially account for the variability observed between devices, particularly during phases of intense exertion. The results of our study suggest some essential practical applications. First of all, armband devices seem to be reliable systems that are very interesting in specific sports field contexts, especially if they are at a stable exercise intensity. However, when using their data, each time an intensity change occurs, the first data from the device should be disregarded because of the error associated with them. This suggests the need for post-exercise signalprocessing that could be automated by applying algorithms but, at the same time, could influence data accuracy. Therefore, the use of chest straps is recommended for sports or exercises with high intensity demands over short periods of time. The findings of this research have direct applications in sports training and monitoring, particularly for sports or activities of stable intensity. Armband devices, such as the Coospo HW807, can be useful for HR monitoring in low- to medium-intensity sports where comfort is a priority. However, chest straps are recommended in high-intensity activities or those requiring rapid changes in exertion, given their greater accuracy under these conditions. This study also suggests the need to apply post-exercise signal processing algorithms in armband devices to improve data accuracy when rapid variations in intensity occur. Furthermore, the study findings indicate that the Coospo HW807 armband could be effectively used for clinical monitoring of heart rate (HR) in patients who need to engage in moderate physical activity. Although the armband presented lower reliability and accuracy in detecting HR during these activities, it can be considered a valuable tool for patients who could benefit from real-time, non-intrusive HR tracking. Additionally, the ease of use and comfort of armband devices may enhance patient adherence compared to traditional chest straps, which can be less practical for daily use outside of clinical or athletic settings. Our research also aimed to perform the measurements in controlled situations to isolate possible measurement errors due to arm movements [24], leading to some limitations. The indoor cycling test makes it difficult to generalise results to other sports and environmental contexts with more specific sporting movements required. Furthermore, other limitations regarding gender and age diversity should be considered relative to participants, so the findings may not directly apply to female populations or individuals in different age ranges. In addition, three devices were analysed, which restricts possible comparisons and does not reflect the full range of technologies available today. Concerning data analysis, future studies may consider complementary methods or robust statistical techniques to minimise the influence of outliers when assessing agreement between devices with differing measurement methodologies. Furthermore, to advance the understanding and validity of HR monitoring devices, future research should replicate this study in competitive settings and with a broader diversity of participants in terms of gender, age, and training level. Comparisons with devices from new brands and emerging technologies would also be of interest, given the constant technological evolution and introduction of new models into the market. Finally, investigating the accuracy of the devices in sports activities with significant arm movements or in diverse environmental conditions could provide additional information for applicability in real situations.