Most exercise occurs in the evening (when there is little or no Vitamin D)
Peak times for leisure and sports
Shading added by Vitamin D Life

See also Vitamin D Life
People who get little noon-day sun must supplement with Vitamin D – systematic review June 2017
20 cent vitamin D pill similar to 2 hours sunbathing at 60 degree latitude – RCT Aug 2013
60 minutes of sunlight needed to decrease vitamin D deficiency in sunny climate – Dec 2012
Indoor bicycling and 2000 IU of vitamin D lowers heart rate by 6 percent – RCT Dec 2016
But, The Shadow Rule – you make more Vitamin D when you are taller than your shadow – 1992
shows that lots of vitamin D can be generated in the morning at 23 degrees latitude
