that's a lot of skeletal muscle
Your body is amazing. Over 650 skeletal muscles working together yield your bilaterally symmetrical biological frame, composed functionally of 325 working pairs of muscles and over 187 joints. How many can you feel?
I'm at about 150, up from just 100 a couple months ago. Yoga and other exercise activities that simultaneously strengthen and stretch your muscular system (including ligaments and tendons) enhance not only your posture and strength but also promote innervation and viscularization of tissue. Here's another serving of Body 101 a la carte: during the first couple weeks of exercising a new muscle, much of the improvement is acually increased efficiency of the nervous system to communicate with muscular fibers and cells (source: hamill and knutzen, the biomechanical basis of human movement).