More formally, chiroplasty, or cheiroplasty, is a term which refers to plastic surgery of the hands. The term combines root word chir(o), which means hand, and the suffix -plasty, which means surgical repair.
(How Do Your Muscles Work continued) Thousands of thin spaghetti-like fibers make up muscle tissue. These fibers receive messages from the brain, causing the fibers to contract. The main muscles at work in cycling are the quadriceps and hamstrings in the upper leg, and the gastrocnemius and soleus in the calf. These muscles contract in a sequence that creates the pedaling action. The quadriceps and hamstrings do most of the work when you ride a bicycle.
As for the Calories burned, the value that BikeWatts presents is the amount of mechanical work per second being performed to move you on your bike. Bicyclists are generally 20-25% mechanically efficient, and thus the total energy used by the rider is 4-5 times the amount that is actually transferred to the bike.