Ex Manchester United Manager Sir Alex Ferguson used Tanning equipment to help boost his players fitness due to a lack of Sun in Manchester. He employed top scientists to think of ways to improve his players performances and gain the absolute maximum from them, VitaminD was the number 1 answer amongst other parts of the training regimes.
#VitaminD is well known for being essential in every part of your body's function (Every cell in the human body has a VDR/VitaminD receptor), but it's crucial in the maintenance of your vital organs and immune system.
Footballers who train at higher altitudes tend to gain a crucial/minimal edge as far as cardiovascular capability and immunity to general illness. The higher the altitude, the thinner the air, and hence the more your organs are pushed to their limits. This is where the handy side effect of more penetrative UVA comes in.
One of the benefits using a sunbed is the production of nitric oxide which dialaites the blood vessels around the heart thus better circulation and more oxygen supplied to the organs and muscles .Hence more muscle contractions and for longer. This is ideal before Exercise.Off the field, Ferguson greatly expanded his backroom staff and appointed a team of sports scientists to support the coaches. Following their suggestions, he installed Vitamin D booths in the players’ dressing room in order to compensate for the lack of sunlight in Manchester
The information regards Sir Alex comes from an interview he did some time ago and can be , and also another secondary reference .