Comment on 'Two enigmas in proprioception: Abundance and location of muscle spindles' by T. Kokkorogiannis

I present observations on the numbers and distributions of muscle spindles indicating that spindle number is an important controlled variable of muscle design, but the distribution of spindles within a muscle is not. Although our understanding of the functional correlates of spindle number is far from complete, I argue that nothing that is known about their number or distribution is inconsistent with them acting as length sensors, in contradiction to Kokkorogiannis's comment [Brain Res. Bull., this issue] on Windorst's review [U. Windhorst, Muscle proprioceptive feedback and spinal networks, Brain Res. Bull. 73 (2007) 155-202].