Low-Cost Continuous Force Measurement Systems for Quadriceps and Hamstrings Strength Assessment: A Scoping Review and Perspective for Clinical Application in Physiotherapy

Accurate assessment of muscle strength is vital in physiotherapy for diagnosis, prognosis, and evaluating interventions. While methods like manual muscle testing (MMT), handheld dynamometry (HHD), and isokinetic dynamometry exist, limitations such as subjectivity (MMT), examiner influence (HHD), cost, and lack of portability (isokinetic/fixed systems) persist. This scoping review examines the literature on quadriceps and hamstrings strength assessment methods, focusing on the potential, development, and validation requirements of low-cost Continuous Force Measurement Systems (CFMS). A literature search was conducted using PubMed, MEDLINE, and Google Scholar for English-language studies published between January 2000 and December 2024. Data regarding study design, assessment methods, equipment, psychometric properties, and key findings were extracted and synthesized. The review confirmed the limitations of existing methods and indicated a growing interest and feasibility in developing low-cost CFMS using readily available sensors and microcontrollers. These systems offer the potential for continuous data capture, including Rate of Torque Development (RTD), providing deeper insights into neuromuscular function than peak force alone. Preliminary studies demonstrate promising results for custom-built, affordable systems. Low-cost CFMS presents a promising avenue to enhance quantitative muscle strength assessment in physiotherapy while combining the objectivity with affordability and portability, facilitating wider adoption in clinical practice, education, and research.