Assessment of Overall Muscle Strength in Children and Adolescents Using Handheld Dynamometry: A Systematic Review of Reference Values and Quality of Data

Background/Objectives: Muscle strength is a vital indicator of the development and health-related fitness in children and adolescents, and it also plays a crucial role in clinical assessments across pediatric rehabilitation. The aim of this review was to evaluate the available literature on handheld dynamometry (HHD) assessments of the overall muscle strength in the pediatric population, focusing on measurement protocols, validity and reliability, and the availability of reference and normative data. Methods: Following PRISMA 2020 guidelines, a systematic review was conducted across PubMed, Scopus, Cochrane CENTRAL, CINAHL, and Web of Science. The protocol was registered in PROSPERO (CRD42024537557). Eligible studies (2005–2023) included healthy participants under the age of 18 reporting on isometric muscle strength using HHDs. Studies reporting handgrip strength or alternative methods (e.g., isokinetic and 1RM) of assessment were excluded. Due to the heterogeneity of the studies, the JBI and COSMIN risk of bias checklists were used to assess risk of bias. A narrative synthesis approach was used to summarize the findings. Results: Twelve studies were included, with a total of 1683 participants aged 4–17 years (764 girls and 919 boys). Test re-test reliability and low measurement error were established in measuring the toe strength, while the concurrent validity of lower limb torque was determined as poor. Conclusions: When standardized protocols and fixed stabilization are implemented, studies confirm good intra- and inter-rater reliability. Substantial heterogeneity in measurement protocols highlights the need for standardized procedures. It is essential to establish normative or reference values by age and sex to enhance clinical decision making and the utility of HHDs in pediatric overall strength assessments.