Methods to assess maximal strength in elite adolescent soccer players: A narrative systematic review

Abstract

Background – Maximal strength (MS) is a key physical quality for the talent development (TD) and talent identification (TI) of youth elite soccer players. This is due to strengths key role in underpinning explosive soccer actions such as sprinting and decelerating and the relationship between strength and injury occurrence. Due to the developmental nature of youth soccer, conducting MS assessments within this population requires several considerations. Nonetheless, a narrative systematic review of MS assessments has not been conducted in youth elite male and female soccer athletes. Objectives - The aims of this narrative systematic review were to: (1) identify the tests and modalities used to assess MS in youth elite soccer players; (2) identify how chronological and biological age may impact the selection of strength tests; (3) report the reliability values of included tests. Methods – A systematic narrative review of the academic databases PubMed (MEDLINE), Scopus, Web of Science, CINHL and SPORT Discus were conducted for studies published until March 2023, using the Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRIMSA) Guidelines. Studies were eligible for inclusion if they: (1) included a population younger than 18 years old (i.e, mean age of the group); (2) players were part of an elite academy or national governing body; (3) included a MS assessment, with reported absolute values; (4) was original work published in a peer-reviewed article and not as a review, in English. Key results – This review returned 86 studies; 22 different tests were implemented with a total of 181 individual evaluations performed. The most common assessments were knee extensor strength (23% of evaluations), and knee flexor strength (22% of evaluations). Three different modalities of strength assessment were identified, maximal voluntary contractions (MVC), maximal voluntary isometric contractions (MVIC) and dynamic free weight (DFW) assessment. The most popular modality was MVC assessments which were assessed in 40 studies (47%) with the majority evaluations performed being isokinetic dynamometry (55% of all evaluations). The implementation of DFW tests were generally employed in older populations (15 years and above). Thirteen studies reported reliability (15%), all of which reported acceptable reliability. However, only the Isometric Mid-Thigh Pull (IMTP) (ICC = 0.93 – 0.98) and NHE (ICC = 0.84-0.96) were shown to have good to excellent within-session reliability within athletes aged less than 15 years old. Conclusions – The broad range of different testing within this review highlights the variety of strength assessments available to practitioners. It is important to determine factors such as maturity status, technical competency and outcome goals when designing a testing battery for youth elite athletes. Given the lack technical proficiency that may exist in younger athletes and athletes experiencing rapid growth, it should be advised that practitioners conduct their own reliability assessments within their environment.