(Image credit: Future) If you’re an Apple Watch wearer, the Health app on your iPhone holds an encyclopedia of (encrypted) data about your overall fitness and wellbeing. From predicting the exact day you ovulate and the time you spend in different stages of sleep, to allowing you to log your daily mood, spending five minutes a day in the Health app can help you spot patterns and trends in your health, and download anything unusual to send to your doctor. I’ve worn an Apple Watch for the better part of the last decade, but like most people, a lot of the data my watch has been collecting has gone unnoticed. I recently spent some time diving into the Health app, and one big one that passed me by is my cardiovascular fitness level. Cardiovascular fitness, measured as VO2 max, is widely considered to be the most important predictor of long-term health.…