Figure 1: The six models used for simulating accelerated contractions of a muscle with an overall mass of are arranged from the left to the right. The models differ (i) by having split the muscle mass into an increasing number () of point masses (PMs; depicted by circles) connected through a corresponding number of CEs (depicted by “brushes”) and (ii) by distributing the optimal muscle length homogeneously to the optimal CE lengths . The sum of the circle areas, symbolising the muscle mass, is constant across the six models. The uppermost PM is always fixed to the world, whereas all other PMs can be accelerated by their adjacent CEs. Note that there is no gravity. Generally, is the overall muscle length .