Instead, youll find much of this crucial data buried away in the Health app on your iPhone. If youre into endurance sports, VO 2 max is a metric youll want to check out. It is measured in liters per minute (Lmin): the volume of oxygen you breath in a minute.īut Apple uses a slightly more complicated metric: mL(kgmin). That means milliliters of oxygen per kilogram of body mass per minute.īy taking your body weight into account in this way, it makes the stat more comparable between different people, since a larger person is likely to consume more oxygen than a smaller person.

Running fast for a few yards is all very well, but that is not going to be much use if you are training for a marathon.

Low-intensity workouts, like walking or slow jogging, are easy to sustain for a long time because they rely on your aerobic energy system.