(1) Background: Regardless of the level of physical activity, performance monitoring is a valuable component of the training process. The aim of this research was to assess the reliability and sensitivity of parameter measurements using the Enode/Vmaxpro sensor. (2) Methods: Metric char- acteristics were examined for average velocity, peak velocity, average power, peak power, movement length, and movement duration. Twenty-seven participants (15 men and 12 women) underwent body composition analysis and testing on a combined leg extension/leg curl machine, performing the exercises with each leg individually under a 30% body mass load. Descriptive statistics, reliability analyses, and difference analyses were conducted to evaluate repeatability and sensitivity levels. The significance threshold was set at the level 0.05. (3) Results: Reliability parameters were found to be statistically significant, both overall (ICC: 0.937–0.991) and separately for men (ICC: 0.899–0.984) and women (ICC: 0.908–0.990). Sensitivity was confirmed through significant differences based on sex (p = 0.000), activity level (p = 0.000), and movement type (p = 0.000). No statistically significant differences were observed between right and left leg performance. (4) Conclusions: The findings suggest that the Enode/Vmaxpro sensor demonstrates sufficient sensitivity and reliability for muscle power testing in biomechanics and sports diagnostics.