Exercise monitoring provides valuable insights into the cardio-respiratory health and physical fitness levels of exercisers. However, most existing studies focus on the monitoring of a specific phase in the full fitness cycle, limiting the comprehensive understanding of exercising performance. This study proposes a novel concept of camera-based monitoring across the full fitness cycle, encompassing the phases of pre-exercise, during-exercise (sport), and post-exercise. Validated video monitoring algorithms are utilized to measure physiological parameters. Physiological parameters, including heart rate (HR), heart rate variability (HRV), and respiratory rate (RR) are measured by a camera in front of a treadmill. The results show that cameras achieve high accuracy in measuring HR and RR, and show a strong correlation with the reference for HRV parameters including mean IBI, VLF, LF, and SD2. This study compares subjects with and without exercise habits, revealing that subjects with exercise habits (ES, exercise subjects) have more robust cardio-respiratory functioning, evidenced by lower HR during the exercise phase and faster post-exercise recovery compared to those without exercise habits (NS, non-exercise subjects). Cameras can achieve the same effectiveness as the reference in showing the differences of monitored parameters (RR, HR, and HRV) between ES and NS. These findings validate the feasibility of camera-based monitoring throughout the full fitness cycle and reveal the contrasting physiological responses of subjects with and without exercise habits.