How often should I wear my watch to get a Cardio Fitness reading? If you’re wearing your watch continuously throughout the day, you should get a reading within 24 hours. If you wear your watch for a few hours each day, it can take up to a week to get a reading. Related articles What is Cardio Fitness? How long does each battery mode last? Why am I not getting a Cardio Fitness reading? I’m not receiving notifications on my Smartwatch. How do I fix this? How can I change the size of my watch band?