Final answer:
Eccentrically activated muscle fibers show an increased force production capacity with higher velocities, which is opposite to concentric muscle actions. Fast fibers with higher myosin ATPase activity contract faster and generate greater force. The force-velocity relationship is hyperbolic for concentric actions, but eccentric actions yield higher force outputs at increased velocities.
Step-by-step explanation:
The relationship between force production capacity and velocity in eccentrically activated muscle can be understood in the context of the muscular force-velocity curve, which is initially described by the Hill equation. When muscles perform eccentric contractions, they are lengthening while producing force. This type of muscle action is known for its high force-generating capacity. Generally, as the velocity of an eccentric contraction increases, muscles are able to produce and withstand greater force compared to concentric contractions. Therefore, we can match:
- High velocity = High force production capacity
- Medium velocity = Medium force production capacity
- Low velocity = Lower force production capacity (compared to higher velocities but still high compared to concentric contractions)
The terms fast fibers and slow fibers refer to the type of muscle fibers and their myosin ATPase activity, which affects their contraction speed and fatigue resistance. As described, fast fibers hydrolyze ATP approximately twice as quickly as slow fibers and thus have a faster rate of cross-bridge cycling and subsequent muscle contraction. Oxidative fibers are more fatigue-resistant, while glycolytic fibers fatigue more quickly. The force-velocity relationship shows a hyperbolic curve, meaning as velocity increases, the force decreases in a concentric action, but in eccentric action, the relationship can be more complex.