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Purpose: This meta-analysis aimed to (1) provide a comparison of peak changes in indirect markers of exercise-induced muscle damage (EIMD) in youths versus adults and (2) determine if the involved limb moderated this effect. Method: Studies were eligible for inclusion if they (1) provided a human youth versus adult comparison; (2) provided data on muscle strength, soreness, or creatine kinase markers beyond ≥24 hours; and (3) did not provide a recovery treatment. Effect sizes (ES) were presented alongside 95% confidence intervals. Results: EIMD exhibited larger effects on adults than in youths for muscle strength (ES = −2.01; P <.001), muscle soreness (ES = −1.52; P <.001), and creatine kinase (ES = −1.98; P <.001). The random effects meta-regression indicated that the effects of upper- and lower-limb exercise in youths and adults were significant for muscle soreness (coefficient estimate = 1.11; P <.001) but not for muscle strength or creatine kinase (P >.05). As such, the between-group effects for muscle soreness (ES = −2.10 vs −1.03; P <.05) were greater in the upper than lower limbs. Conclusion: The magnitude of EIMD in youths is substantially less than in their adult counterparts, and this effect is greater in upper than lower limbs for muscle soreness. These findings help guide practitioners who may be concerned about the potential impact of EIMD when training youth athletes. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of a 10-month neuromuscular training (NMT) intervention on muscle architecture, isometric force production, and stretch-shortening cycle (SSC) function. Thirty-seven girls aged 6-12 years were placed into gymnastics + NMT (gNMT; n = 15), gymnastics only (GYM; n = 10), or maturity-matched control (CON; n = 12) groups. The gNMT group followed a 10-month NMT program in addition to gymnastics training, whereas the GYM group only participated in gymnastics training. Isometric midthigh pull (IMTP) and drop jump (DJ) kinetics were measured, in addition to muscle thickness, fascicle length, and pennation angle of the gastrocnemius medialis at baseline and at 4, 7, and 10 months. A3 x 4 (group x time) repeated-measures ANCOVA (covariate, % predicted adult height) was used to evaluate within-group changes. Significance level was set at p < 0.05. Significant interaction effects were observed in muscle thickness, absolute (PFabs) and relative peak force (PFrel) in the IMTP and various DJ variables. The gNMT group demonstrated improvements in muscle thickness, IMTP PFabs and PFrel, and DJ kinetics, most commonly evidenced from 7 months onward. The GYM group's muscle thickness also significantly improved, accompanied by improvements in some DJ kinetics. The CON group did not experience any desirable changes. Overall, NMT elicited positive changes in muscle thickness, PFabs and PFrel, and SSC function to a greater extent than gymnastics training alone or growth and maturation. As most adaptations took 7 months, longer-term NMT programs should be implemented with youth female gymnasts. [ABSTRACT FROM AUTHOR]

Relationships between force-generating capabilities and weightlifting performance (e.g., snatch, clean and jerk [C&J], and combined total) have previously been explored in adult weightlifters; however, associations in young athletes are unknown. The purpose of this study was twofold: (a) to examine the relationships between countermovement jump (CMJ) and isometric midthigh pull (IMTP) kinetics and weightlifting performance in young weightlifters and (b) to determine the proportion of weightlifting performance that could be accounted for by CMJ and IMTP kinetics using principal component analysis (PCA). Thirty-seven young weightlifters (12-18 years of age) completed 3 trials of CMJ and 2 trials of the IMTP assessments on dual force plates. Recent competition maximum loads, obtained within 2 weeks of the data collection, for the C&J and snatch were also recorded. Pearson's zero-order correlation coefficients demonstrated moderate to very high correlations (r = 0.359-0.801; all p ≤ Benjamini-Hochberg critical values [B-Hα]) between CMJ kinetic variables, including jump height, average braking force, average braking velocity, absolute and relative braking net impulse, absolute and relative force at minimum displacement, absolute and relative propulsive force, absolute and relative propulsive net impulse and average propulsive velocity, and weightlifting performance. High to very high correlations were evident between IMTP peak force and relative peak force and all weightlifting performance metrics (snatch, C&J, combined total, combined total [kg]/body mass [kg-0.67], and Sinclair's total; r = 0.538-0.796; p ≤ B-Hα). Components from the PCA were used to conduct stepwise, multiple, linear regression analyses. Moderate (45.8-52.9%) and large percentages (79.1-81.3%) of variance in absolute measures of weightlifting performance were explained by IMTP peak force variables and CMJ propulsive variables, respectively. These novel findings indicate that IMTP peak force variables and CMJ propulsive variables could provide valuable insight for talent identification and long-term athletic development in junior weightlifting pathways. [ABSTRACT FROM AUTHOR]

This study investigates the inter-week test-retest reliability of 9.14 meter (10 yard) sprint times in youth athletes. Although essential for assessing athletic ability and training efficacy, the critical and comprehensive examination of both relative and absolute reliability indices for short-distance sprints has been insufficient in youth contexts. One hundred ninety-eight youth athletes (128 males and 70 females) underwent 2 sprint attempts across 2 separate trials 24 hours apart and within 7 days of each other. The sprints were measured using dual-beam timing gates to capture split times for 0-4.57 meter (0-5 yards), 4.57-9.14 meter (5-10 yards), and 0-9.14 meter (0-10 yards). The minimal mean difference between the best sprint times across trials was 0.02 ± 0.13 seconds for males and 0.003 ± 0.14 seconds for females. No significant mean differences were found between trials for either gender (males: p = 0.0875; females: p = 0.8752), suggesting no systematic bias in sprint times. The SEM was 0.092 seconds for males and 0.099 seconds for females, with a corresponding SEMCV% of 4.6 and 4.8%. The overall coefficient of variation was 9.8% for males and 8.9% for females. Intraclass correlation coefficient values suggested that the sprint times across trials were reliable (males: 0.80; females: 0.76). The minimal detectable change was 0.25 seconds for males, 0.27 seconds for females. Cohen's d indicated trivial effects (<0.2) for males (0.154) and females (0.021). Minimal mean differences, a low SEM, and consistent ICC values demonstrate that the 0-9.14 meter sprint is a reliable assessment in youth athletes. [ABSTRACT FROM AUTHOR]

Chronic exercise training is associated with an "athlete's artery" phenotype in young adults and an attenuated age-related decline in endothelium-dependent arterial function. Adolescence is associated with an influx of sex-specific hormones that may exert divergent effects on endothelial function, but whether training adaptations interact with biological maturation to produce a "youth athlete's artery" has not been explored. We investigated the influence of exercise-training status on endothelium-dependent arterial function during childhood and adolescence. Brachial artery flow-mediated dilation (FMD) was assessed in n = 102 exercise-trained (males, n = 25; females, n = 29) and untrained (males, n = 23; females, n = 25) youths, characterized as pre (males, n = 25; females, n = 26)- or post (males, n = 23; females, n = 28)-predicted age at peak height velocity (PHV). Baseline brachial artery diameter was larger in post- compared with pre-PHV youths (P ≤ 0.001), males compared with females (P ≤ 0.001), and trained compared with untrained youths (3.26 ± 0.51 vs. 3.11 ± 0.42 mm; P = 0.041). Brachial FMD was similar in pre- and post-PHV youths (P = 0.298), and males and females (P = 0.946). However, exercise-trained youths demonstrated higher FMD when compared with untrained counterparts (5.3 ± 3.3 vs. 3.0 ± 2.6%; P ≤ 0.001). Furthermore, brachial artery diameter (r2 = 0.142; P = 0.007 vs. r2 = 0.004; P = 0.652) and FMD (r2 = 0.138; P = 0.008 vs. r2 = 0.003; P = 0.706) were positively associated with cardiorespiratory fitness in post-, but not pre-PHV youths, respectively. Collectively, our data indicate that exercise training is associated with brachial artery remodeling and enhanced endothelial function during youth. However, arterial remodeling and endothelium-dependent function are only associated with elevated cardiorespiratory fitness during later stages of adolescence. NEW & NOTEWORTHY: We report preliminary evidence of the "youth athlete's artery," characterized by training-related arterial remodeling and elevated endothelium-dependent arterial function in children and adolescents. However, training-related adaptations in brachial artery diameter and flow-mediated dilation (FMD) were associated with cardiorespiratory fitness in adolescents, but not in children. Our findings indicate that endothelium-dependent arterial function is modifiable with chronic exercise training during childhood, but the association between FMD and elevated cardiorespiratory fitness is only apparent during later stages of adolescence. [ABSTRACT FROM AUTHOR]

This aim of this study was to investigate the effects of a 12-week resistance training program in talented junior golfers. Eighteen talented youth golfers were pair matched by maturity status and handicap, and subsequently allocated to an experimental (EXP) or control group. During the 12-week intervention, both groups continued with their normal golf practice while the EXP group also completed a progressive twice-weekly resistance training program. At baseline, subjects performed multiple trials of an isometric midthigh pull (IMTP), counter-movement jump (CMJ), standing long jump, golf movement screen (GMS), and isometric plank hold. Club head speed (CHS) and carry distance for a 6-iron and driver were also measured using a commercial launch monitor. When controlled for maturity offset, there were significant (p < 0.05) interaction effects in favor of the EXP group for absolute (g = 1.29) and relative (g = 2.06) peak force forthe IMTP, CMJ absolute (g = 0.73) and relative (g = 0.66) peak power, jump height (g = 1.05), modified reactive strength index (g = 1.30), lateral (g = 0.48-0.88) and horizontal jump distance (g = 1.20), and GMS total score (g = 1.07). Significant interaction effects were also reported in 6-iron and driver CHS and carry distance in favor of the EXP group (p < 0.05; g = 0.41-1.64). These findings indicate that twice-weekly resistance training in combination with regular golf practice can stimulate increases in measures of strength, power, and movement competency in youth golfers, which should contribute to enhanced golf swing performance. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the effects of maturity status on drop jump (DJ) kinetics in young male athletes (categorized as early-pre-peak height velocity [PHV] [<â2.51 years], late-pre-PHV [â'1.99 to â'1.00 years], circa-PHV [â'0.50 to 0.50 years], and post-PHV [>1.00 years]). All athletes performed a DJ from a 30-cm box onto force plates with performance variables (jump height, ground contact time, and reactive strength index) and absolute and relative kinetic variables during the braking and propulsive phases assessed. Subjects were categorized into GOOD (no impact-peak and spring-like), MODERATE (impact-peak and spring-like), or POOR (impact-peak and not spring-like) stretch-shortening cycle (SSC) function. The post-PHV group exhibited significantly greater values for most absolute kinetic variables compared with early-pre-PHV, late-pre-PHV, and circa-PHV (p < 0.05). The differences observed between consecutive maturity groups were similar in magnitude for most absolute variables (Cohen's d = 0.53-1.70). Post-PHV male athletes outperform their less mature counterparts during a DJ, and this may be attributed to the growth and maturity-related structural and motor control strategy changes that occur in children. Stretch-shortening cycle function in boys seems to improve with maturity status reflected by a greater number of post-PHV participants displaying GOOD SSC function (65.8%) and a greater number of early-pre-PHV participants displaying POOR SSC function (54.4%). However, a number of mature boys displayed POOR SSC function (17.8%), suggesting that the development of SSC function is not exclusively related to maturation. [ABSTRACT FROM AUTHOR]

New Findings: What is the central question of this study?Gonadal hormones modulate cerebrovascular function while insulin‐like growth factor 1 (IGF‐1) facilitates exercise‐mediated cerebral angiogenesis; puberty is a critical period of neurodevelopment alongside elevated gonadal hormone and IGF‐1 activity: but whether exercise training across puberty enhances cerebrovascular function is unkown.What is the main finding and its importance?Cerebral blood flow is elevated in endurance trained adolescent males when compared to untrained counterparts. However, cerebrovascular reactivity to hypercapnia is faster in trained vs. untrained children, but not adolescents. Exercise‐induced improvements in cerebrovascular function are attainable as early as the first decade of life. Global cerebral blood flow (gCBF) and cerebrovascular reactivity to hypercapnia (CVRCO2${\mathrm{CV}}{{\mathrm{R}}_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$) are modulated by gonadal hormone activity, while insulin‐like growth factor 1 facilitates exercise‐mediated cerebral angiogenesis in adults. Whether critical periods of heightened hormonal and neural development during puberty represent an opportunity to further enhance gCBF and CVRCO2${\mathrm{CV}}{{\mathrm{R}}_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ is currently unknown. Therefore, we used duplex ultrasound to assess gCBF and CVRCO2${\mathrm{CV}}{{\mathrm{R}}_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ in n = 128 adolescents characterised as endurance‐exercise trained (males: n = 30, females: n = 36) or untrained (males: n = 29, females: n = 33). Participants were further categorised as pre‐ (males: n = 35, females: n = 33) or post‐ (males: n = 24, females: n = 36) peak height velocity (PHV) to determine pubertal or 'maturity' status. Three‐factor ANOVA was used to identify main and interaction effects of maturity status, biological sex and training status on gCBF and CVRCO2${\mathrm{CV}}{{\mathrm{R}}_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$. Data are reported as group means (SD). Pre‐PHV youth demonstrated elevated gCBF and slower CVRCO2${\mathrm{CV}}{{\mathrm{R}}_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ mean response times than post‐PHV counterparts (both: P ≤ 0.001). gCBF was only elevated in post‐PHV trained males when compared to untrained counterparts (634 (43) vs. 578 (46) ml min−1; P = 0.007). However, CVRCO2${\mathrm{CV}}{{\mathrm{R}}_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ mean response time was faster in pre‐ (72 (20) vs. 95 (29) s; P ≤ 0.001), but not post‐PHV (P = 0.721) trained youth when compared to untrained counterparts. Cardiorespiratory fitness was associated with gCBF in post‐PHV youth (r2 = 0.19; P ≤ 0.001) and CVRCO2${\mathrm{CV}}{{\mathrm{R}}_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ mean response time in pre‐PHV youth (r2 = 0.13; P = 0.014). Higher cardiorespiratory fitness during adolescence can elevate gCBF while exercise training during childhood primes the development of cerebrovascular function, highlighting the importance of exercise training during the early stages of life in shaping the cerebrovascular phenotype. [ABSTRACT FROM AUTHOR]

Golfers who want to improve their technical proficiency will undoubtedly hire a swing coach who may also influence and give advice on how the golfer can improve outside of technical enhancement (i.e. strength and conditioning, warm-ups, cool-downs etc.). With research examining the effects of strength and conditioning on youth golfers beginning to materialise, it is important to ascertain golf coaches' perceptions of strength and conditioning, warm-ups and cool-downs and how they are utilised with youth golfers. Fifty Professional Golfers' Association Professionals and Assistant Professionals completed an online questionnaire on their perceptions of, and approaches to, strength and conditioning, warm-up and cool-down activities for youth golfers. Data indicated that 84% and 80% of coaches perceived strength and conditioning could enhance golf swing performance and reduce the risk of injury, respectively. Although all coaches agreed golfers aged 18 years and under can take part in strength and conditioning activities, there was no consensus on when a golfer should start strength and conditioning activities, with most coaches unaware of the existing guidelines surrounding youth resistance training. Warm-ups are perceived by coaches to be beneficial for youth golfers with > 75% of coaches stating their players completed a warm-up, however, the modes of exercise coaches deemed suitable for a warm-up were varied. Cool-downs were deemed beneficial for aiding recovery post-round, yet over half of coaches selected their players did not habitually complete one. Findings from the questionnaire highlight that although perceptions towards strength and conditioning, warm-ups and cool-downs are positive, educational solutions to disseminate the underlying contemporary guidelines and practical applications to coaches and players are required. [ABSTRACT FROM AUTHOR]

This study investigated measures of physical fitness and golf swing performance in competitive youth golfers. Sixty-four golfers, subdivided into three handicap groups (CAT0, <1 handicap, n = 21; CAT1, 1–5 handicap, n = 20; CAT2, >5 handicap, n = 23), were assessed for isometric strength, power, movement competency and core endurance. Clubhead speed (CHS) and carry distance for 6-iron and driver were also measured. When controlled for maturity offset, CAT0 golfers produced significantly greater peak power, isometric absolute and relative peak force, movement competency, and jump distance than higher handicap golfers (all p < 0.05). Maturity status was strongly associated with CHS and carry distance for both clubs (R2 = 0.552–0.784). Linear regressions showed maturity offset explained a larger amount of variance in CHS (driver = 78.4%, 6-iron = 71.3%) and carry distance (driver = 55.2%, 6-iron = 57.4%) than handicap. Multiple linear regression analyses showed that peak power explained 79.4% and 82.4% of variation in 6-iron and driver CHS, respectively, while isometric absolute peak force explained 69.6% and 74.3% of the variation in 6-iron and driver carry distance, respectively. Subsequently, interventions targeting the development of peak force and power could aid golf swing performance in young golfers. [ABSTRACT FROM AUTHOR]

Purpose: To quantify speed, peak momentum, standing long jump (SLJ), and the ratio of vertical to horizontal take-off velocity (Ratiovert–hori TOV) in young female gymnasts of different maturity status and their influence on vaulting vertical TOV. Methods: One hundred twenty gymnasts age 5–14 years were subdivided into maturity groupings using percentage of predicted adult height. Participants performed three 20-m sprints, SLJ, and straight jump vaults that were recorded using 2-dimensional video and analyzed using digitizing software. Results: All speed intervals, peak speed, peak momentum, SLJ distance, vault height, and vertical TOV increased between the early prepubertal and late prepubertal (P <.001; d = 0.65–1.10) and early prepubertal and pubertal (P <.001; d = 0.75–1.00) groups. No differences between these metrics were observed between the 2 most mature groups (d = 0.01–0.55). Multiple regression analyses revealed peak speed had the strongest association with vertical TOV (R2 = 59%) and also identified the Ratiovert–hori as a secondary determinant (R2 = 12%). A separate regression model indicated that maturity status (percentage of predicted adult height) moderately influences vertical TOV during vaulting (R2 = 41%). Conclusion: Speed and SLJ performance increase between the early prepubertal and late prepubertal years in young female gymnasts. However, given that peak speed and Ratiovert–hori combined to explain 71% of the total variance in vaulting vertical TOV, in order to increase aerial time for more advanced vaulting, practitioners should attempt to enhance peak speed alongside takeoff technique to develop gymnasts' ability to transfer linear speed to vertical TOV. [ABSTRACT FROM AUTHOR]

Context: Single-leg hop tests are used to assess functional performance following anterior cruciate ligament (ACL) reconstruction. Recording 6-m timed hop scores using a stopwatch increases the potential for misclassification of patient status due to the number of error sources present. Objective: To examine the consistency of pass/fail (>90% limb symmetry index [LSI]) decisions in athletes tested at discharge following ACL reconstruction during the 6-m timed hop and the agreement between different human raters using a stopwatch and an electronic timing system. Setting: Clinic, rehabilitation. Participants: A total of 20 professional soccer players (age 24.6 [4.2] y; height 175.3 [10.2] cm; mass 73.6 [14.5] kg; 36 [10.5] wk following ACL reconstruction) volunteered to take part in this study. Main Outcome Measures: Two individual raters recorded each trial of the 6-m timed hop test on each limb with a stopwatch and an electronic timing system acted as the criterion measure. LSI scores were also computed with a pass score >90% LSI. Results: No significant differences were observed between limbs for any scoring method (P >.05). Mean differences indicated the electronic timing system was slower than both human raters (P <.05). Five participants failed the test (<90% LSI) but on each occasion this was only recorded by one method of rating. Kappa statistics showed no agreement in LSI scores across all 3 methods of scoring (κ = −.13) and no agreement when comparing the light gates to individual raters and rater 1 versus 2 (κ < 0). 95% limits of agreement in LSI scores recorded values of approximately ±20%. Conclusions: The 6-m timed hop test recorded using a stopwatch is not a valid measure to make clinical decisions following ACL reconstruction. Systematic bias between methods also suggests that a stopwatch and electronic timing system cannot be used interchangeably. [ABSTRACT FROM AUTHOR]