Longitudinal trajectories of athlete burnout among young table tennis players: A 3-wave study

Purpose:The purposes of this study were to examine the trajectories of athlete burnout across a 2-month period characterized by high physical,psychological,and social demands to explore(1)whether several subgroups of athletes representing distinct burnout trajectories emerged from the analyses and(2)whether athlete burnout symptoms(reduced accomplishment,sport devaluation,and exhaustion)developed in tandem or whether some burnout dimensions predicted downstream changes in other dimensions(causal ordering model).Methods:One hundred and fifty-nine table tennis players in intensive training centers completed a self-reported athlete burnout measure across 3 time points within a 2-month period characterized by high demands.Data were analyzed through latent class growth analysis.Results:Results of latent class growth analysis showed 3 distinct trajectories for each athlete burnout dimension,indicating not only linear or quadratic change but also stability in longitudinal athlete burnout perceptions.Results also suggested that the 3 dimensions of athlete burnout did not develop in tandem.Rather,the likelihood of belonging to particular emerging trajectories of sport devaluation and physical/emotional exhaustion was significantly influenced by the athletes’perception of reduced accomplishment assessed at Time 1.Thus,reduced accomplishment predicted downstream changes in the 2 other athlete burnout dimensions.Conclusion:As a whole,these results highlighted that the multinomial heterogeneity in longitudinal athlete burnout symptoms needs to be accounted for in future research.

Limb symmetry index in competitive alpine ski racers:Reference values and injury risk identification according to age-related performance levels

Purpose： The aims of this study were to assess differences of limb symmetry index （LSI） in strength- and coordination-related tasks between high-level, competitive, noninjured ski racers of different age-related performance levels and to prospectively assess limb differences as a possible risk factor for traumatic and overuse injury in youth ski racers. Methods： The study （Study 1） included 285 high-level competitive ski racers （125 females, 160 males） of 3 age-related performance levels and based on the school system： 95 youth （10-14 years, secondary modem school）, 107 adolescent （15-19 years, grammar school）, and 83 elite athletes （20-34 years）. To investigate the second aim （Study 2）, 67 of the 95 youth athletes were included and any traumatic or overuse injuries were prospectively recorded over 2 seasons. All athletes performed 4 unilateral tests （strength related： one-leg counter movement jump （OL-CMJ） and one-leg isometric/isokinetic press strength test （OL-ILS）; coordination related： one-leg stability test （OL-ST） and one-leg speedy jump test （OL-SJ））. The LSI was calculated by dividing the dominant leg by the nondominant leg and multiplying by 100. Kruskal-Wallis H tests and binary logistic regression analyses were conducted. Results： There were significant differences between the LSI of the 3 age-related performance-level groups only in the strength-related tests： the OL-CMJ （X^2（2, 285） = 9.09; p = 0.01） and the OL-ILS （X^2（2,285） = 14.79; p 〈 0.01）. The LSI for OL-ILS was found to be a significant risk factor for traumatic injury in youth ski racers （Wald = 7.08; p 〈 0.01）. No significant risk factors were found for overuse injuries. Conclusion： Younger athletes display slightly greater LSI values only in the strength-related tests. The cut-off value of limb differences of 〈 10% for return to sport decisions seems to be appropriate for elite athletes, but for youth and adolescent athletes it has to be critically discussed. It seems to be necessary to define thresholds based on specific performance tasks （strength vs. coordination related） rather than on generalizations, and age-related performance levels must be considered. Limb differences in unilateral leg extension strength represent a significant injury risk factor in youth ski racers.2018 Published by Elsevier B.V. on behalf of Shanghai University of Sport. This is an open access article under the CC BY-NC-ND license. （http：//creativecommons.org/licenses/by-nc-nd/4.0/）.

Trunk Flexion to Extension Strength Ratio of 11- to 18- Year Old Youth Ski Racers: Data from 15 Years of Talent Development in Austria

Purpose The aim of the present study was to evaluate the trunk strength capacity of alpine ski racers aged 10-18 years,who were tested during the last 15 years,to identify reference values for trunk flexor to extensor strength ratios according to age and sex.Methods In total,2841 participants(1605 males,1236 females;10-18 years)were included,who were pupils of a famous skiing-specific secondary modern school or members of the provincial ski team between 2006 and 2020.The maximum isometric trunk flexion and extension strength was measured using the slightly modified Back Check.Sex-specific differ-ences were assessed with Student’s t test or Mann-Whitney-U test.Univariate analyses of variance or Kruskal-Wallis-H tests were used to assess differences between age groups.Descriptive sex-and age-specific reference values were calculated(norm area:mean±½standard deviation).Results Sex-specific differences were found for both flexion(starting at 11 years)and extension strength(starting at 12 years)(P<0.001).Lower flexion to extension strength ratios were identified for males(0.89±0.18)compared with females(0.82±0.15),but the ratios remained constant across age groups for both sexes.Conclusion The present study provides age-and sex-specific reference values for trunk flexion to extension strength ratios for 10-to 18-year old youth and adolescent ski racers.The data of the present study represent a large data pool of youth ski racers at a high-performance level;thus,coaches can use the reference values for comparing the ratios of their athletes.