Eight-time Mr. Olympia Ronnie Coleman dominated bodybuilding from 1998 to 2005, and he was known for having some of the most brutal leg workouts known to man. Coleman did walking lunges along the gravel road in front of Metroflex in 100° heat with as much as 365 pounds.

Some bodybuilders love the way working out in the sun makes them feel, but this isn’t just a coincidence. Most of those benefits of sunlight have emerged with its beneficial role in boosting vitamin D, but a new U.K. study suggests sunlight’s benefits extend far beyond vitamin D.

Scientists at the University of Edinburgh discovered that sunlight enhances nitric oxide (NO) production. During the research, dermatologists studied the blood pressure of 24 volunteers under UV and heat lamps. In one session, the volunteers were exposed to both UV rays and the heat of the lamps. In the other, the UV rays were blocked so that only the heat affected the skin. The results showed that blood pressure dropped significantly for an hour after exposure to UV rays, but not after the heat-only sessions. Scientists said that this suggested it was the sun’s UV rays that brought health benefits, which were thought to be accompanied by increases in NO production. The volunteers’ vitamin D levels remained unaffected in both sessions. The researchers suspected that nitric oxide, a chemical transmitter stored in huge reserves in the skin, can be released by UV light, to great benefit for blood pressure and the cardiovascular system.

Try taking your workouts outside like Ronnie and you may feel better pumps!