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Background Eccentric resistance training is recognised as an effective stimulus for enhancing measures of muscular strength and power in adult populations; however, its value in youth athletes is currently not well understood. Objective The aim of this systematic review was to critically appraise the effects of eccentric resistance training on measures of physical performance (i.e. muscular strength, jump, sprint and change of direction) in youth athletes 18 years of age and under. Methods Original journal articles published between 1950 and June 2022 were retrieved from electronic search engines of PubMed, SPORTDiscus and Google Scholar’s advanced search option. Full journal articles investigating the acute and chronic effects of eccentric resistance training on measures of physical performance in youth athletes (i.e. a person 18 years of age or under who competes in sport) were included. The methodological quality and bias of each study were assessed prior to data extraction using a modified Downs and Black checklist. Results The search yielded 749 studies, of which 436 were duplicates. Three-hundred studies were excluded based upon title and abstract review and a further 5 studies were removed following the modified Downs and Black checklist. An additional 14 studies were identified during backward screening. Accordingly, 22 studies were included in our systematic review. The Nordic hamstring exercise and flywheel inertial training were the most frequently used eccentric resistance training methods in youth athletes. Improvements in physical performance following the Nordic hamstring exercise are dependent upon an increase in the breakpoint angle, rather than training volume (sets and repetitions), and are further elevated with the addition of hip extension exercises or high-speed running. A minimum of 3 familiarisation trials is necessary to elicit meaningful adaptations following flywheel inertial training. Furthermore, an emphasis should be placed upon decelerating the rotating flywheel during the final one to two thirds of the eccentric phase, rather than gradually throughout the entire eccentric phase. Conclusions The findings of this systematic review support the inclusion of eccentric resistance training in youth athletes to improve measures of muscular strength, jump, sprint and change of direction performance. The current eccentric resistance training methods are predominantly limited to the Nordic hamstring exercise and flywheel inertial training; however, the efficacy of accentuated eccentric loading to improve jump performance warrants attention in future investigations.

The purpose of this study was to determine the intrasession reliability of countermovement jump (CMJ) braking and propulsive phase variables in youth athletes. Thirty youth athletes between the age of 10- and 16-years volunteered to take part in this study. All participants performance 3 CMJ trials on a force platform. Thirteen of 16 CMJ variables were found to have acceptable absolute reliability in the pre-PHV group (CV% = 3.51-9.96) whilst the circa-PHV group contained 10 variables demonstrating acceptable absolute reliability (CV% = 2.37-9.67). Almost all variables (14 out of 16) in the post-PHV group were found to have acceptable absolute reliability (CV% = 2.59-9.61). Mean and peak braking RFD displayed poor absolute reliability in all maturity groups (CV% = 10.89-21.55). Time to take-off, braking and propulsive phase time and propulsive impulse demonstrated the largest differences between pre- and circa-PHV groups (p < 0.005; d > 0.95). Braking phase time, peak and mean braking force, mean braking power and RSImod demonstrated the biggest differences between the circa- and post-PHV groups (p < 0.001; d > 1.81). The poorest reliability scores were found in the circa-PHV group, demonstrating the need for additional familiarisation at this stage of maturity.