Disaggregating the influence of maturity status on training, anthropometric, performance, skeletal periphery, and hormonal factors in athletic boys

Maturity offset (i.e., age from peak height velocity [PHV]) is widely used to assess maturational status among youth athletes, but details on the skeletal periphery, hormones and training factors are lacking. More precision is also needed to explicate the timing, tempo, and sequence of growth-related events. These gaps were addressed in a cross-sectional study. One hundred and two athletic boys (aged 14.1 ± 0.5 years) were evaluated for training details, salivary testosterone and cortisol, height, body mass, body mass index, body fat, fat-free mass (FFM), hand and carpal bone area, bone mineral content (BMC) and density (BMD), and countermovement jump performance. Participants were assigned to circa-PHV (N = 56) and post-PHV (N = 46) groups for comparisons, before data pooling and disaggregation using generalized additive and linear regression models. The older post-PHV group had a larger body size, more testosterone, and better performance and skeletal outcomes, whilst weekly training and school-based exercise favored the younger circa-PHV group (all p < 0.001). Smoother plots verified these differences via linear, or weakly non-linear, associations. Maturity offset was predicted (R2 = 0.848) by the linear combination of FFM (42.0 % relative contribution), hand BMD (31.5 %), chronological age (16.0 %), testosterone (6.7 %), and training hours (3.8 %). In conclusion, athletic boys who presented at different stages of maturity (-0.98 to 2.84 years from PHV) also differed on many developmental features. Most variables increased at constant, or near-constant, tempo with a higher maturity offset, with FFM and hand BMD emerging as the strongest linear predictors of maturational status.

Physical determinants of golf swing performance in competitive youth golfers

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.

Tensiomyographic Assessment of Contractile Properties in Elite Youth Soccer Players According to Maturity Status

Little is known about how muscle contractile properties are affected by biological maturation in elite youth soccer players. This study aimed to determine the effects of maturation on contractile properties of rectus femoris (RF) and biceps femoris (BF) muscles assessed by tensiomyography (TMG) and provide reference values for elite youth soccer players. One hundred twenty-one elite youth soccer players (14.98 ± 1.83 years; 167.38 ± 10.37 cm; 60.65 ± 11.69 kg) took part in the study. The predicted peak height velocity (PHV) was used in order to establish players' maturity status (Pre-PHV, n = 18; Mid-PHV, n = 37; Post-PHV = 66). Maximal radial displacement of the muscle belly, contraction time, delay time, and contraction velocity for RF and BF muscles were recorded. One-way ANOVA showed no significant differences between PHV groups for any tensiomyography variables in RF and BF muscles (p > 0.05). Our results established that maturity status did not show a significant effect in mechanical and contractile properties on RF and BF muscles evaluated by TMG in elite youth soccer players. These findings and reference values can be useful for strength and conditioning coaches of elite soccer academies in order to optimize the evaluation of neuromuscular profiles.

The Association Between Chronological Age and Maturity Status on Lower Body Clinical Measurements and Asymmetries in Elite Youth Tennis Players

BACKGROUND

Tennis is one of the most popular sports among youths. At elite levels, a notable increase in injury incidence and a temporary decline in performance may occur when children progress through puberty. However, limited research has explored maturity-associated variations in clinical measurements suggested as predictors of injury and tennis performance in elite youth players. Therefore, the main purpose of this study was to analyze the association between chronological age and maturity status on several measures of neuromuscular capability and physical performance as well as bilateral (interlimb) asymmetries in elite youth tennis players.

HYPOTHESIS

Youth tennis players around peak height velocity (PHV) will show higher growth-related impairments or deficits in measures of neuromuscular capability and physical performance than their less (pre-PHV) and more (post-PHV) mature counterparts irrespective of sex.

LEVEL OF EVIDENCE

Level 4.

METHODS

A total of 68 male (age, 13.7 ± 1.1 years; height, 162.4 ± 9.4 cm; body mass, 51.4 ± 10.3 kg [Mean values ± SD]) and 60 female (age, 13.6 ± 1.1 years; height, 162.8 ± 7.2 cm; body mass, 52.7 ± 7.5 kg [Mean values ± SD]) elite youth tennis players from 2 different age groups (under 13 [U13] and under 15 [U15]) and maturity status (pre-PHV, around PHV, and post-PHV), were tested during national training camps. Tests included the Y Balance Test, isometric hip abduction and adduction strength, hip ranges of motion (ROMs), and countermovement jump (CMJ) height. Bayesian analysis was used to establish any significant between-group differences.

RESULTS

Only dynamic balance (in boys; Bayesian factor [BF₁₀] = 88.2) and jump height (in both boys and girls; BF₁₀ >100) were significatively associated with chronological age, whereby the U15 group showed lower Y Balance Test reach distances (-6%; standardized effect size δ = 0.62) but higher CMJ height scores (+18%; δ = 0.73) than the U13 group. Although boys jump higher (+11%; δ = 0.62) and were stronger in isometric hip adduction strength (+14%; δ = 0.92) than girls, the latter had greater hip internal ROM values (+15%; δ = 0.75). Furthermore, relevant maturity-associated effects (BF₁₀ = 34.6) were solely observed for the CMJ test in boys, with the most mature players demonstrating higher jump height scores (+12%; δ = 0.93). Finally, a significant percentage (>25%) of tennis players, independent of sex, demonstrated bilateral asymmetries in hip ROM, hip strength, and jump height values.

CONCLUSION

The findings of this study show that in U13 and U15 male and female tennis players, there were neither positive nor negative maturity-associated variations in the clinical measurements analyzed (with the exception of jump height in male players). The high proportion of tennis players showing bilateral asymmetries in dynamic balance, hip ROM, and strength and jump performance highlight the need of future studies to analyze these factors in relation to unilateral tennis-specific adaptations in the musculoskeletal and sensorimotor systems.

CLINICAL RELEVANCE

These results may help to better understand how different clinical measurements are associated with the process of growth and maturation in elite youth tennis players and may aid in the design of specific training interventions during these stages of development.

Relationship between Running Spatiotemporal Kinematics and Muscle Performance in Well-Trained Youth Female Athletes. A Cross-Sectional Study

The purpose of this cross-sectional study was to analyse the relationship of neuromuscular performance and spatiotemporal parameters in 18 adolescent distance athletes (age, 15.5 ± 1.1 years). Using the OptoGait system, the power, rhythm, reactive strength index, jump flying time, and jump height of the squat jump, countermovement jump, and eight maximal hoppings test (HT_8max) and the contact time (CT), flying time (FT), step frequency, stride angle, and step length of running at different speeds were measured. Maturity offset was determined based on anthropometric variables. Analysis of variance (ANOVA) of repeated measurements showed a reduction in CT (p < 0.000) and an increase in step frequency, step length, and stride angle (p < 0.001), as the velocity increased. The HT_8max test showed significant correlations with very large effect sizes between neuromuscular performance variables (reactive strength index, power, jump flying time, jump height, and rhythm) and both step frequency and step length. Multiple linear regression found this relationship after adjusting spatiotemporal parameters with neuromuscular performance variables. Some variables of neuromuscular performance, mainly in reactive tests, were the predictors of spatiotemporal parameters (CT, FT, stride angle, and VO). Rhythm and jump flying time in the HT_8max test and power in the countermovement jump test are parameters that can predict variables associated with running biomechanics, such as VO, CT, FT, and stride angle.

Developing motor competency in youths: Perceptions and practices of strength and conditioning coaches

Motor competency is integral to the long-term athletic development of youths. Strength and conditioning (S&C) coaches are recommended to deliver motor competency interventions, yet no studies have investigated their perceptions and practices for developing motor competency in youths. Sixty-seven male, and 4 female S&C coaches completed an initial and follow up questionnaire using a 5-point Likert scale, rating 1] the importance of developing competence, and 2] how frequently they developed competence across 90 motor competencies. Over 55% of S&C coaches reported a broad range of "important" (69/90) and "frequently developed" (48/90) motor competencies. The most important motor competency was "deceleration" (4.9 ± 0.3), whilst "hip hinge (bilateral)" was the most practised (4.4 ± 0.5). S&C coaches targeted upper body pushing and pulling competencies more than their perceived importance, whilst agility (e.g., turning) competencies were targeted less than their importance. Further analysis showed S&C coaches who delivered 3-4 sessions per week targeted 15-18% more competencies compared to ≤ 2 sessions per week. Overall, these findings have strong implications for youth motor competency development including the reflection of important vs. practised competencies, coach education programmes, and consideration for how S&C coaches should seek to optimise motor competency development within youths.