Getting Back Into Yoga

Ever since finishing the SD marathon, I've dropped yoga like a load of smelly laundry. Yoga for me is only a means to an end.  I don't have the patience for it, and I get easily bored with the same routines.  However, it's the only exercise that helps me stretch and prevent running-related injuries. So, I've returned to it reluctantly after having felt some tightness in the hamstrings.  After Monday's class I started feeling sore in my core...who'da thunk.  Maybe I'm not doing it correctly...