That depends entirely on what you define as 'fastest movement' and over what duration.
The act of running demands muscular activity. The world record on 100m is quite a fast movement, largely due to movement of larger scale human muscles. Also, since muscles are made up out of cells and movement of groups of these cells means movement of the muscle, I am not sure that I understand the distinction.
You are confusing things. Plus, I'm not sure there is a good answer to the way you phrased the question.
Reflexive motion is under the neural control of ganglia. The response time is very fast. Voluntary motion repsonse time is a lot slower because of all the routing of signals from the brain outward. None of this relates to fast motion in the sense of speed of muscular contraction. It relates to fast or slow repsonse time.
For a muscle to contract a joint fully from complete extension is mostly a mechanical problem. Generally, it isn't just one muscle doing the job, it is a group of muscles, so most muscles contract only partially. The mechanical part is the amount of mechanical advantage the muscle has on its target. Biceps
and triceps open and close the elbow, pretty much all by themselves. How fast they do this depends on : muscle tone and load on the joint.