A Little Fast Twitch Physiology
The shortening velocity of a two joint muscle is less than that of its-one joint synergist. When a joint moves muscles work together in synergy to produce or enhance movement.
The soleus muscle is known for its abundance of slow twitch fibers. During standing, to maintain posture the soleus muscle acts to control sway in an anterior and posterior direction. It is very active when you raise up on your toes. The soleus is a one- joint muscle.
The Gastrocnemius is primarily composed of fast twitch fiber and is a two-joint muscle, as it moves the foot and crosses the knee joint.
When performing an explosive movement by pushing off with the foot (plantarflexion) and simultaneously extending the knee, the shortening velocity of the gastrocnemius is less than the shortening velocity of the soleus. To really understand this phenomena of the faster gastroc moving slower read about the force-velocity relationship of muscle contraction.
The advantage of a lesser shortening velocity is timing up the movement to include as much tissue as possible to produce force, an important part of the bodies strategy in power production.
Coaches preach 'team' and understand that every player on the team is important. Your muscles understand 'team' also and are only as fast as their slowest fibers. They need to work together. So, Get them all Strong. Every fiber counts.