ECSS Paris 2023: OP-AP26
INTRODUCTION: Gymnastics requires repeated jumping, landing and precise neuromuscular control. The drop jump (DJ) is commonly used to assess reactive performance because it involves short ground contact times and effective use of the stretch-shortening cycle (Wilder et al., 2021). The reactive strength index (RSI), calculated as jump height divided by contact time, is a key indicator of DJ performance. Although drop height affects neuromuscular and mechanical responses, the optimal DJ height in young gymnasts has not been clearly established (Moir et al., 2022). Therefore, this study aimed to determine optimal bilateral and unilateral DJ heights in young female gymnasts. METHODS: Twenty-two young female gymnasts (11.1 +/- 1.5 years, range 9-14) participated. Following anthropometric assessment, bilateral DJs were performed from 20, 30 and 40 cm, and unilateral DJs from 10 to 30 cm in 5 cm increments (Bassa et al., 2012). Participants kept their hands on their hips and were instructed to minimize ground contact time while maximizing jump height. Two trials per height were completed and the best trial was used for analysis. Jump height was calculated from flight time, and RSI was computed as jump height divided by contact time (Bishop et al., 2019). Optimal height was defined as the condition with the highest RSI (Byrne et al., 2017). For unilateral analysis, the limb with the higher mean RSI across all heights was classified as the strongest limb, while the contralateral limb was defined as the weakest. RESULTS: The effect of drop height on reactive strength index (RSI) was examined using repeated-measures ANOVA. For bilateral drop jumps (20, 30 and 40 cm), no significant main effect of height was observed (F(2,42) = 0.55, p = 0.582, eta p2 = 0.03), although the highest mean RSI was recorded at 30 cm. In contrast, a significant main effect of height was found for unilateral drop jumps in the strongest limb (10-30 cm) (F(4,84) = 4.38, p = 0.003, eta p2 = 0.17). Post-hoc comparisons (Bonferroni) indicated that RSI at 10 cm was significantly greater than at 20, 25 and 30 cm (p < 0.05). A similar significant effect was observed for the weakest limb (F(4,84) = 5.08, p = 0.001, eta p2 = 0.19), with RSI at 10 cm significantly greater than at 30 cm (p = 0.026). These findings suggest that bilateral RSI is relatively stable across heights, whereas unilateral reactive performance is optimized at lower drop heights, particularly 10 cm. CONCLUSION: These results demonstrate that drop height does not significantly influence bilateral RSI within the tested range in young female gymnasts, although the highest mean value was observed at 30 cm, suggesting potential practical relevance. However, unilateral reactive performance is clearly height-dependent, with optimal values observed at 10 cm. Therefore, lower unilateral drop heights should be considered when assessing and prescribing reactive strength training in this population.
Read CV Nazli OzgorECSS Paris 2023: OP-AP26
INTRODUCTION: In soccer, muscular strength is a determinant factor of performance. Stronger athletes may benefit from high-velocity-oriented strength training aimed at shifting the high-velocity region of the force–velocity curve, whereas weaker athletes may require a greater emphasis on maximal strength development to shift upward the entire force-velocity profile. The purpose of the study was to investigate the effects of strength-level-based organization of strength and power training on neuromuscular performance in youth soccer players. METHODS: Twenty-six male U16–U17 high-level youth soccer players completed baseline squat one-repetition maximum (1RM) testing and were divided into a stronger (SG, n=12) and a weaker group (WG, n=14). Over a 12-week in-season period, both groups performed one complex training session combining heavy resistance exercises with plyometric or ballistic exercises, whereas SG completed an additional power training session and WG an additional heavy strength session. Pre- and post-measurements included body composition, squat-1RM strength, leg extension isometric peak torque (IPT) and rate of torque development (RTD), countermovement jump (CMJ), drop jump (DJ), linear speed, repeated sprint ability (RSA), agility, shot velocity, and GPS-derived running metrics including top speed, maximal acceleration-deceleration, and aerobic capacity. A two-way repeated measures ANOVA (group x time) was used for the determination of pre- and post-differences. RESULTS: Both groups significantly improved the percentage of body fat (SG: -2.6%, p=0.01; WG: -2.4%, p=0.001) and lean mass (SG: 3.3%, p=0.005; WG: 4.35%, p=0.01). Squat 1RM strength relative to mass increased significantly in both groups (SG: 18.2%, p=0.001; WG: 27.19%, p=0.001). IPT relative to mass (SG: 10.3%, p=0.021; WG: 2.8%, p=0.03) and RTD increased for both groups (p<0.05). CMJ (SG: 5.7%, p=0.01; WG: 6%, p=0.05) and DJ reactive strength index increased in both groups (SG: 25.1%, p=0.004; WG: 26.2%, p=0.01). Linear sprint improved only in SG (30m: -1.3%, p=0.042), while RSA total time (SG: -2.7%, p=0.002; WG: -3.4%, p=0.01) and best time trial (SG: -2.4%, p=0.002; WG: -3.6%, p=0.01) improved for both groups. Shot velocity increased in both groups (SG: 8%, p=0.03; WG: 5.9%, p=0.01) while both groups increased top speed (SG: 3.2%, p=0.031; WG: 3.45%, p=0.014), maximal acceleration (SG: 7.3%, p=0.028; WG: 6.3%, p=0.01), and deceleration (SG: 7.7%, p=0.045; WG: 16.1%, p=0.003). Aerobic capacity significantly increased for both groups (SG: 1.6%, p=0.033; WG: 1.3%, p=0.047). CONCLUSION: Organizing the in-season strength and power training according to the athletes’ relative strength level is an effective strategy to enhance neuromuscular and physical performance in high-level youth soccer players. Strength and conditioning practitioners may consider allocating additional weekly training volume toward maximal strength development in weaker youth players and toward velocity-oriented power training in stronger players.
Read CV Andreas Kyriacou RossiECSS Paris 2023: OP-AP26
INTRODUCTION: Resistance training is considered safe for children and essential for youth athletes. However, valid tests for assessing strength levels in this population under field conditions remain limited. While the isometric mid-thigh pull or maximum number of pull-ups are promising tools for assessing knee-hip-extension and upper-body pulling strength, valid tests for assessing upper-body pushing strength are lacking. Embedded in a three-stage project, we introduce the upper-body isometric squeeze test (IST) as a novel and efficient field test to close this gap. METHODS: In a preceding investigation we established a high criterion validity between IST and bench press (BP) performance in strength training experienced adults (overall r=0.93, n=30; men r=0.88, n=15, 10.5 years strength training experience; women r=0.77, n=15, 9.1 years experience). To assess if this correlation remains stable in a younger cohort, we recruited 44 youth athletes with initial strength training experience (n=24 boys, 15.4±1.4 years old; n=20 girls, 14.4±1.6 years old) from regional performance development programmes in four different sports. Self-reported BP experience was 2.2±1.0 years in the boys and 1.7±0.8 years in the girls. After a standardised warm up, the participants completed a 1-to-5-repetition maximum BP protocol (RMP) and IST in a randomized order during one testing session. IST required a 3-second bilateral compression of a mobile dynamometer (DynaMo Plus, VALD, Brisbane, Australia) in front of the chest while lying in a supine position. BP performance was established using an estimated 1-repetiton-maximum (1RM) derived from the RMP. Criterion validity was assessed using Pearson correlation between BP 1RM and IST peak force. RESULTS: Mean BP 1RM was 74.7±18.5kg for the boys and 49.5±15.0kg for the girls, mean IST peak force was 458.0±102.5N and 322.2±69.2N respectively. Criterion validity for the whole cohort was high (r=0,79), for the boys moderate (r=0.64) and higher again for the girls (r=0.74). CONCLUSION: These findings indicate that IST can be considered as a valid proxy for maximal upper-body pushing strength. From our previous work we can conclude that general and/or strength-specific training experience might affect the criterion validation, suggesting to explore a more substantial familiarisation than we currently applied. By the same token, we are also still investigating why especially some boys (in contrast to the men in the previous study) struggled with the IST. However, the general ease of use of IST in its current form remains unmatched while still upholding a sufficient validity for a field test. Thus, we plan to investigate in a next step the reliability of IST in even younger youth athletes with limited to no (barbell-based) strength training experience.
Read CV Nikolai BöhlkeECSS Paris 2023: OP-AP26