Experimental Physiology special issue: ‘Mechanotransduction, muscle spindles and proprioception’

Abstract

This special issue of Experimental Physiology contains a collection of 13 manuscripts based on oral presentations presented at the meeting on 'Mechanotransduction, Muscle Spindles and Proprioception' , which took place at the Ludwig-Maximilians-Universität in Munich in July 2022. The participants included >30 speakers from Taiwan, Canada, Australia, the USA, Israel and from all over Europe and the UK. In this Editorial, I want to present a brief personal view of how the idea to organize this meeting emerged and put the individual publications of this issue into perspective.Proprioception is essential for all coordinated movements and required for perceiving the position of the body in space (Proske & Gandevia, 2012). Given that Aristotle (384-322 BC) first defined smell, sight, touch, taste and hearing as the five senses, proprioception has often been coined the 'sixth' sense, despite >20 senses being known, with the exact number of senses remaining elusive. Although proprioception is an integrative system that processes information from a combination of peripheral sensory input, including muscle length and tension, joint angle and skin stretch (Macefield & Knellwolf, 2018), the key components of this intricate system are muscle spindles (Matthews, 2015). Embedded in almost every skeletal muscle, these primary proprioceptive sensory organs relay constant information about muscle tone and length to the CNS (Kröger, 2018;Proske & Gandevia, 2012). From this information, the CNS processes the spatial position and motion of the body in space, a process crucial for motor control, voluntary movement, posture and a stable gait (Kröger, 2018;Kröger & Watkins, 2021).During its prime time in the 1950s and 1960s, muscle spindles were at the forefront of sensory physiology, and many basic principles were discovered using muscle spindles, including, for example, the rate coding of stimulus intensity (Adrian & Zotterman, 1926). For sensory physiology, muscle spindles were similar to what the neuromuscular junction had been for the discovery of the basic principle of synaptic transmission. In fact, many scientists working on the neuromuscular junction also worked on muscle spindles, including Sir