Objectives: The mobile phone has become an inseparable part of everyday life, and are equipped with a variety of sensors that make it possible to monitor different aspects of human activity, including physical exercise. The aim of this study was to verify whether acceleration recorded by a mobile phone can reliably reflect the intensity of strength exercises. Methods: 40 participants with different levels of physical perfor-mance were involved in the experiment. Each subject completed 30 repetitions of the clean and jerk exercise, performed at regular intervals over the course of 11 minutes with a barbell weighing 30 kg. A mobile phone equipped with the PHYPHOX application was attached to the right forearm to record acceleration values. From each repeti-tion, both the average and maximum acceleration were evaluated. As a control pa-rameter, the barbell velocity was measured using the Tendo Power Analyzer. Results: The results showed that the mean acceleration during the exercise was 4.80 ± 0.95 m·s⁻², while the maximum acceleration reached 33.71 ± 15.19 m·s⁻². The average power output was 419.00 ± 67.34 W, and the maximum power achieved 913.81 ± 259.44 W. The mean execution velocity was 1.42 ± 0.23 m·s⁻¹, with a maximum velocity of 2.16 ± 0.38 m·s⁻¹. Data analysis revealed a significant correlation between both average and maximum acceleration and average and maximum velocity (r > 0.65, p < 0.01). Conclusions: These findings suggest that a mobile phone can serve as a practical and reliable tool for assessing the intensity of strength exercises. However, due to the small number of participants, further research on a larger sample is recommended to verify the generalizability of the results and potentially extend the application of this method to other types of physical activities.