Testing heart rate variability (HRV) is a valuable tool in personal training, as it provides insights into an individual's autonomic nervous system response and recovery status. Monitoring HRV can help trainers assess fatigue levels and overtraining, enabling them to adjust workout intensity and recovery protocols accordingly. A high HRV typically indicates a well-recovered state, while low HRV may point towards stress or inadequate recovery. Using HRV data can enhance personalized training programs, optimize performance, and support overall wellness in clients.