Generating high levels of muscular strength and power are important for success in sport and may have long-term implications for sporting careers in youth athletes. Importantly, maturation may confound the neuromuscular adaptations to resistance training when attempting to differentiate between training-vs. growth-induced strength and power gains; thus, potentially leading to erroneous conclusions regarding the efficacy of resistance training in youth athletes. The aim of this review was to critically appraise the literature concerning the efficacy of externally loaded free-weight resistance training on strength and power measures in youth athletes at different stages of maturity. Strength underpins power production; thus, developing strength through traditional resistance training methods can positively influence powerful sporting movements. In addition, weightlifting has the capacity to improve muscular power via explosive lower-body triple extension, which is essential for many sports. Despite the complexity of the techniques involved, it can be a safe and effective method to improve athletic qualities in young athletes, potentially more so than plyometric training. While low-load, high-velocity training can have a positive effect influence on high speed movements such as sprinting, the reduced intensity appears to be disadvantageous post peak-height velocity. Irrespective of age, well-coached progressive strength training adhering strictly to correct technique can then be periodised within a long-term athletic development program. It is important to primarily develop muscular strength, while concurrently refining the technical skill required for weightlifting. Physically mature athletes should undertake highintensity resistance training to maximise neuromuscular adaptations, leading to positive changes in strength and power.

Purpose: Much less is known about strength and conditioning (S&C) practice in women's versus men's soccer. The aim of this study was to compare S&C practice between coaches working in men's or women's soccer, at first team or academy level, worldwide. Methods: A total of 170 participants, who were involved with S&C support at their soccer club (in Europe, USA and South America, within men's or women's first team or academy settings) completed a comprehensive online survey, designed to evaluate (i) their academic qualifications and S&C coaching experience; and their preferred methods for (ii) physical testing; (iii) strength and power development; (iv) plyometric training; (v) speed development; and (vi) periodization. Results: Women's academies had fewer weekly in-season S&C sessions than men's academies (1.6±0.6 vs. 2.3±0.9, p=0.005). Relatively, fewer women's academy S&C coaches (6%) used Olympic weightlifting movements than men's academy S&C coaches (32%, p=0.030). Relatively, more women's academy coaches (47%) used the Nordic hamstring exercise (NHE) compared to men's academy coaches (15%, p=0.006), but relatively more women's vs. men's first team coaches (61% vs. 38%, p=0.028) and women's vs. men's academy (61% vs. 38% coaches, p=0.049) utilised rating of perceived exertion-based load prescriptions. Conclusion: Notable differences in S&C practice exist between coaches of men's and women's soccer squads, particularly at academy level. Fewer weekly S&C sessions in women academy players may have implications for physical development, while the greater use of subjective load prescriptions in both academy and first team women's squads may lead to sub-optimal performance gains.

Differences exist between top-tier soccer leagues (e.g. anthropometry and match demands), which may influence strength and conditioning (S&C) practice. Thus, the aim of this study was to investigate whether current S&C practice in men's and women's (first team and academy) squads differed between global regions. A total of 170 participants, involved in the delivery of S&C support at their soccer club (based on South America (SA), the USA, the UK, or other European countries (EUR)), completed a survey examining their S&C methods. The survey comprised six sections: (i) academic qualifications and S&C coaching experience; and their preferred methods for (ii) physical testing; (iii) strength and power development; (iv) plyometric training; (v) speed development; and (vi) periodization. Coaches in EUR conducted fewer formal S&C sessions, placed less importance on free-weight resistance training (RT), and performed less speed and plyometric training compared to coaches in other global regions (all p < 0.05). While coaches working with UK squads devoted more time to physical development than those in EUR, they regarded bodyweight training as the most important RT modality in comparison to USA and SA, who prioritized free-weight RT. Finally, SA academy players are introduced to formal S&C later (∼14 years old) than those in the UK (∼12 years old, p = 0.002). However, it is reasonable to suggest that the S&C practice of coaches in the USA and SA align better with scientific guidelines for strength and power development in soccer, with emphasis on free-weight RT alongside regular sprint and plyometric training, compared to coaches in the UK and EUR.

McQuilliam, SJ, Clark, DR, Erskine, RM, and Brownlee, TE. The effect of high vs. moderate-intensity resistance training on strength, power and muscle soreness in male academy soccer players. J Strength Cond Res 37(6): 1250–1258, 2023—The aims of this study were to investigate the impact of high-intensity, low-volume (HRT) vs. moderate-intensity, and high-volume resistance training (MRT) vs. soccer training only (control group [CON]) on changes in strength, power, and speed and to compare delayed onset muscle soreness (DOMS) between groups in male academy soccer players (ASP). Twenty-two ASP (age: 18 ± 1 years) were assigned to HRT (n = 8), MRT (n = 7), or CON (n = 7). High-intensity resistance training completed 2 sets of 4 repetitions parallel back squat (PBS) repetitions at 90% 1 repetition maximum (1RM), while MRT performed 3 sets of 8 repetitions PBS repetitions at 80% 1RM, both once a week for 6 weeks in-season, alongside regular soccer training. All groups completed the following pretraining and posttraining assessments: 3RM PBS, bilateral vertical and horizontal countermovement jumps (CMJ), squat jump (SJ), and 30-m sprint. Delayed onset muscle soreness was assessed using a visual analog scale throughout training. High-intensity resistance training and MRT experienced similar increases compared with CON in absolute PBS 3RM (p < 0.001), SJ height (p = 0.001), and CMJ height (p = 0.008) after training. There was a greater increase in PBS 3RM relative to body mass after HRT than MRT and CON (p = 0.001) and horizontal CMJ distance improved in HRT but not in MRT or CON (p = 0.011). There was no change in 10-m, 20-m, or 30-m sprint performance in any group. High-intensity resistance training volume was 58 ± 15% lower than that of MRT (p < 0.001), and DOMS measured throughout training did not differ between groups (p = 0.487). These findings suggest that 1 HRT session a week may be an efficient method for improving strength and power in ASP in-season with minimal DOMS.

Scientific guidelines exist regarding strength and conditioning (S&C) best practice, for both first team and academy level soccer. However, it is not known if these research-informed guidelines are followed in such applied settings. The aim of this study was to investigate current S&C practice in first team and academy level (men's and women's) soccer, in multiple countries/continents. A total of 170 participants, who were involved with the delivery of S&C support at their soccer club, completed a comprehensive survey, describing their training methods. Data were analysed using Pearson's chi-square test of independence and independent t-tests. Statistical significance was set to p < 0.05. A greater proportion of academy compared to first team coaches assessed acceleration/sprint (92% vs. 83%, p=0.026), jump (95% vs. 83%, p=0.023) and change of direction performance (77% vs. 61%, p=0.031). The weekly training structure differed between groups, particularly within women's squads, with women's academy coaches reporting the lowest session frequency of all groups (1.59 ± 0.62 session per week, 44 ± 17 min duration). A greater proportion of academy (54%) versus first team (35%) coaches prioritised bodyweight training ( p=0.031), despite a similar distribution of movement patterns trained. Overall, 44% S&C coaches reported using training intensities below strength training guidelines (≥80% 1RM). To conclude, there were many differences in S&C practice between S&C coaches working with first team and academy squads but particularly noteworthy was the greater proportion of academy coaches prioritising bodyweight training compared to first team coaches, which may limit physical development in academy players.