It could be that some quirk of human anatomy - say, the way the wrist bones are configured or how the thumb is shaped - allows him to do that especially well.
(Your body normally manufactures Vitamin D with the help of sunlight.) Prolonged deficiency can cause bone and muscle weakness, but two months probably isn't enough to do long-term damage.
3
老师:你知道人体有多少块骨头吗?
Teacher: Do you know how many bones are there in a human body?