What are you seeing in the diagram? What is their significance?
The diagram depicts three different motor units (motorneuron and the muscle fibres it innervates), that have very different force capability as shown by the twitch responses and fatigue curves. Broadly speaking they are representative of three muscle fibre types – one slow and two fast that are known by a multitude of names.
Something that has always fascinated me is this transformation between fast fibre types. As soon as we begin training our super explosive fast fatiguing (FF) muscle fibres begin transforming to the fatigue resistant (FR) fast oxidative glycolytic fibres (FOG).
Can you stop this transformation? Yes, with the right type of training.
Do you want to stop this? Most likely in sports that have one off expressions of force such as a shot-putting, but other sports?
How different are the fast twitch fibres in their force expression and is this transformation really that significant? Some would argue that muscle architecture has a greater influence on force, velocity and function? Join me in my online course "Shaping and Shifting Muscle" to find out more about fibre type.