The article at the link discusses the fact that Manchester United, a very good soccer team from Britain, exposes its players to ultraviolet radiation from sun lamps in order to keep vitamin D levels high. The author of the article, surprisingly, does not mention increased athletic performance; nevertheless, sun-lamp expsoure has been known to enhance athletic performance since the 1940s. I co-authored a research paper on this subject with Dr. John Cannell. (Cannell JJ, Hollis BW, Sorenson MB, Taft TN, Anderson JJ. Atheltic performance and vitamin D Med Sci Sports Exerc. 2009 May;41(5):1102-10.) In that publication, we noted that the Germans, who dominated the Olympic Games for many years, used sun-lamp treatments to decrease reaction time and to increase strength, endurance and speed.
The Manchester Club probably used the sun lamps to protect health, but the same treatment may have led to much of their success on the playing field!