Physical exercise can 'train' the immune system. The finding comes from a study of older adults with a history of endurance training, which involves prolonged physical activity such as long-distance running, cycling, swimming, rowing, and walking.
Zone zero: The rise of effortless exercise. In the language of endurance training, zone 1 usually means about 50-60% of your maximum heart rate. Zone zero dips beneath that. It has become shorthand for very light activity, with surprising benefits.
Scientists Shed New Light on How Endurance Training Transforms Your Muscles
