Abstract Introduction : Using wearable step-counting devices is a common method in scientific research to evaluate ambulatory activity. Hawthorne effect, defined as an increase in productivity or performance resulting from the perception of being monitored, is often overlooked by researchers and remains poorly understood, especially in the assessment of ambulatory activity using wearable step-counting. The present study aimed to assess ambulatory activity levels in various age groups and quantify the impact of wearing step-counting devices on the daily ambulatory activity in men. Methods A convenience sample of sixty males was included and allocated into three age groups (20-25, 40-45, and 60-65 years old), with 10 participants in the control group and 10 in the experimental group for each age category. Steps count data were collected in two stages. First, from the previous week, month, and six months; second, after full seven days of wearing a technologically sham pedometer watch. Experimental groups were told that the watch is a step counter device, and they are being monitored, even though all data were collected from the iPhone "Health" application (iOS 16.5), while the control group remained blind until the last data collection was completed. Results When comparing the before and after intervention data, the study found positive Hawthorne effect on the level of ambulatory activity in young, middle-aged, and older adults by 62.90%, 55.58%, and 81.96%, respectively. Significant differences were found between each experimental group and its respective control group after the one-week intervention (p < 0.001). Conclusions The research concludes that all experimental groups increased their step count by more than 50% compared to their initial levels