Musculoskeletal conditions affect bones, joints, and muscles of the locomotor system and are a leading cause of disability worldwide. This suggests that current musculoskeletal rehabilitation techniques fail to target the characteristics (e.g., physiological/physical/psychological) most influential for long-term musculoskeletal health. To identify whether a physiological characteristic is impaired, it must be measured. In neuromuscular control, traditional research approaches use magnitude-based measurements (e.g., peak force/standard deviation of force/coefficient of variation of force). However, magnitude-based measurements miss 'hidden information' regarding a physiological system's status across time. To better identify physiological characteristics that are clinically-important for long-term musculoskeletal health, other measurement approaches currently less applied in musculoskeletal research may be helpful. The purpose of this article is to present an introduction to technical and measurement principles for quantifying the 'complexity' of muscle force control as one representation of peripheral joint neuromuscular control. Complexity measurements are time-based and consider the irregular temporal structure of physiological signals. We review theoretical principles underlying measuring complexity of muscle force control and explain its clinical relevance for musculoskeletal scientists and clinicians. The principles include sensorimotor control of peripheral joints, muscle force signal construction and features, muscle force control measurement procedures, and variability and complexity variables. We propose the potential utility of measuring the complexity of muscle force control for diagnosing sensorimotor system impairment and prognosis following musculoskeletal disease or injury. This article will serve as an educational asset and a scientific resource that will inform future research directions to optimise rehabilitation for people with peripheral joint disease and injury.

Deborah Falla is Chair in Rehabilitation Science and Physiotherapy at the University of Birmingham, UK and is the Director of the Centre of Precision Rehabilitation for Spinal Pain (CPR Spine). Her research focuses on optimising the management of musculoskeletal disorders with a particular interest in spinal pain. She has published ~400 papers in international, peer-reviewed journals which have been cited >20,000 times, and is an author/editor of four books including the latest entitled “Grieves Modern Musculoskeletal Physiotherapy (5th Ed)” (Elsevier).

She has delivered more than 40 keynote lectures and over 250 invited post-graduate workshops on the management of neck pain to health care practitioners in over 25 countries ensuring translation of her research to the benefit of the patient. Professor Falla is listed as the number 1 expert on Neck Pain on ExpertScape and is ranked #2 as the Highly Ranked Scholar – Lifetime for the topic of Neck Pain on ScholarGPS. Additionally, she is ranked in the top 0.05% of all scholars worldwide according to Scholar GPS.

She has obtained awards from major grant funding bodies (e.g., MRC, NIHR, UK Space Agency, Royal Society), charities (e.g., Versus Arthritis, DEBRA UK, Inspire Foundation), and industry (e.g., BTE Technologies, Dynamis MedTech Ltd) to support her research. Furthermore, she has received several recognitions and awards for her work including Fellow of the International Society of Electrophysiology and Kinesiology, the German Pain Research Prize, the George J. Davies - James A. Gould Excellence in Clinical Inquiry Award and the Delsys Prize for Electromyography Innovation.

She is the Editor-in-Chief of Musculoskeletal Science & Practice (Elsevier) and is an Associate Editor of the Journal of Electromyography and Kinesiology (Elsevier). From 2016 to 2018 she was President of the International Society of Electrophysiology and Kinesiology.