Physical Change when Improving Flexibility
So my education in physiology and anatomy was never in depth and now even my old biology education has gotten, well, old. My web searching has brought up some very technical stuff so.. here goes:
What physically changes internally as you improve flexibility?
Bonus question: How old of material can you trust on these type of physical training questions? Has the field been advancing and everything is out of date quickly or is older stuff I learned still valid?