Change of Direction Performance in Young Tennis Players: A Comparative Study Between Sexes and Age Categories.

ABSTRACT: Fernandez-Fernandez, J, Loturco, I, Pereira, LA, Del Coso, J, Areces, F, Gallo-Salazar, C, and Sanz-Rivas, D. Change of direction performance in young tennis players: a comparative study between sexes and age-categories. J Strength Cond Res 36(5): 1426-1430, 2022-The aim of this study was to examine the differences in linear sprint, change of direction (COD) performance, and COD deficit in a large sample of under-13 (U13) and under-15 (U15) male and female tennis players. One hundred and twenty-eight junior tennis players grouped into 2 age-groups (U13 years [32 boys and 28 girls] and U15 [36 boys and 32 girls]) participated in this study. Tests included anthropometric measurements, sprints (5-, 10- and 20-m), and a modified version of the 505 COD test. The differences in performance between age-categories and sex were assessed via an independent t-test. The differences in the physical tests between U13 and U15 players were tested using a univariate analysis, with age and anthropometric variables as covariates. Effect sizes (ESs) were calculated for pairwise comparisons. Results showed that boys presented lower 20-m sprint times than girls in the U13 (ES: 0.54; p < 0.05), and lower linear sprint (5-20-m) and COD times than girls in the U15 category (ES varying from 0.67 to 1.60; p < 0.05). Comparing age-groups, U15 girls demonstrated a higher COD deficit than the U13 (p < 0.05), whereas no differences were found in the other variables. In boys, no significant differences were observed in any variable when comparing both categories. These results could be of great interest for coaches and researchers involved in the development and training of elite tennis players, suggesting the need to include strategies able to improve sprint and COD performance throughout the players' specialization process.

Polygenic Profile and Exercise-Induced Muscle Damage by a Competitive Half-Ironman.

Del Coso, J, Salinero, JJ, Lara, B, Gallo-Salazar, C, Areces, F, Herrero, D, and Puente, C. Polygenic profile and exercise-induced muscle damage by a competitive half-ironman. J Strength Cond Res 34(5): 1400-1408, 2020-To date, it is still unknown why some individuals develop higher levels of muscle damage than other individuals, despite participating in exercise with comparable levels of physical intensity. The aim of this investigation was to analyze 7 single-nucleotide polymorphisms (SNPs) that are candidates to explain individual variations in the level of muscle damage attained during a half-ironman competition. Using the model of Williams and Folland (2, 1, and 0 points for optimal, intermediate, and suboptimal genotype), we determined the total genotype score from the accumulated combination of 7 SNPs (ACE = 287bp Ins/Del; ACTN3 = p.R577X; creatine kinase, muscle type = NcoI; insulin-like growth factor 2 = C13790G; interleukin-6 = 174G>C; myosin light chain kinase = C37885A; and tumor necrosis factor-α = 308G>A) in 22 experienced triathletes. Before and after the race, a sample of venous blood was obtained to measure serum markers of muscle damage. Two groups of triathletes were established according to their postcompetition serum CK concentration: low CK responders (n = 10; 377 ± 86 U·L) vs. high CK responders (n = 12; 709 ± 136 U·L). At the end of the race, low CK responders had lower serum myoglobin concentrations (384 ± 243 vs. 597 ± 293 ng·ml, p = 0.04). Although the groups were similar in age, anthropometric characteristics, and training habits, total genotype score was higher in low CK responders than in high CK responders (7.7 ± 1.1 vs. 5.5 ± 1.1 point, p < 0.01). A favorable polygenic profile can contribute to reducing the level of muscle damage developed during endurance exercise.

The influence of a badminton competition with two matches in a day on muscle damage and physical performance in elite junior badminton players.

To investigate the effects of a badminton competition with 2 matches in a day on hip strength and range of motion (ROM) and exercise-induced muscle damage in elite junior badminton players. Twenty players (age: 17±0.8 years; body mass: 62.9±6.5 kg, height: 173.8±8.9 cm) participated in this study. Passive hip internal (IR) and external rotation (ER), abduction (ABD) and adduction (ADD) hip ROM, isometric hip ADD and ABD muscle strength, countermovement vertical jump (CMJ) height and blood creatine kinase concentration (CK) were measured before and after a badminton competition during an international tournament. Blood samples were collected 24 h after the end of the last match. Compared to baseline values, hip IR and ER ROM were significantly decreased at post-competition in the dominant (IR=-9.0%; p=0.007 and ER=-15.2%; p=0.002) and non-dominant limbs (IR=-9.08%; p=0.004 and ER=-19.4%; p<0.001). In contrast, hip ADD (13.5%; p<0.001) and ABD (14.6%; p<0.001) strength increased significantly after the competition in the dominant limb and ABD strength increased significantly in the non-dominant limb (9.2%; p=0.001). From baseline values, CK increased after the competition (430.1%) and values remained elevated over baseline values 24 h later (160.4%). Although hip muscle strength increased, a badminton competition with two consecutive matches reduced hip ROM and increased blood CK concentration. This study suggests the necessity of investigating recovery strategies after a badminton competition to return hip ROM to basal values before the next day of the competition.

ACTN3 X-allele carriers had greater levels of muscle damage during a half-ironman.

PURPOSE: Alpha-actinin-3, encoded by the ACTN3 gene, is an actin-binding protein with an important role in myofibril contraction and muscle force output. In humans, there is a relatively common deficiency of the α-actinin-3 due to homozygosity in a polymorphism of the ACTN3 gene (R577X, rs1815739), that has been related to decreased resistance to strain during voluntary muscle contractions. The purpose of this study was to investigate the influence of the ACTN3 genotype on the level of exercise-induced muscle damage attained by 23 experienced triathletes during an official half-ironman competition. METHODS: Before and after the race, a sample of venous blood was obtained and jump height was measured during a countermovement jump. The changes in serum creatine kinase (CK-MM isoform) were measured in the blood samples and muscle pain was measured with a visual analogue scale (0-10 cm). Data from RX heterozygotes and XX mutant homozygotes were grouped as X-allele carriers (n = 13) and compared to RR homozygotes (n = 10). RESULTS: Race time was very similar between groups (313 ± 31 vs. 313 ± 25 min; P = 0.45); however, pre-to-post-competition reduction in jump height was greater in X-allele carriers than RR homozygotes (-18.4 ± 11.4 vs. -8.2 ± 6.9%; P = 0.04). At the end of the race, X-allele carriers presented higher serum CK-MM concentrations (682 ± 144 vs. 472 ± 269 U/L; P = 0.03), and there was also a tendency for higher self-reported values of lower limb muscle pain (7.7 ± 1.1 vs. 6.3 ± 2.3 cm; P = 0.06). CONCLUSIONS: X-allele triathletes in the ACTN3 R577X polymorphism presented greater signs of exercise-induced muscle damage during a half-ironman race than RR homozygotes.

ACTN3 genotype influences exercise-induced muscle damage during a marathon competition.

PURPOSE: Exercise-induced muscle damage has been identified as one of the main causes of the progressive decrease in running and muscular performance in marathoners. The aim of this investigation was to determine the influence of the ACTN3 genotype on exercise-induced muscle damage produced during a marathon. METHODS: Seventy-one experienced runners competed in a marathon race. Before and after the race, a sample of venous blood was obtained and maximal voluntary leg muscle power was measured during a countermovement jump. In the blood samples, the ACTN3 genotype (R577X) and the changes in serum creatine kinase and myoglobin concentrations were measured. Data from RX heterozygotes and XX mutant homozygotes were grouped as X allele carriers and compared to RR homozygotes. RESULTS: At the end of the race, X allele carriers presented higher serum myoglobin (774 ± 852 vs 487 ± 367 U L-1; P = 0.02) and creatine kinase concentrations (508 ± 346 vs 359 ± 170 ng mL-1; P = 0.04) than RR homozygotes. Pre-to-post-race maximal voluntary leg muscle power reduction was more pronounced in X allele carriers than RR homozygotes (-34.4 ± 16.1 vs -27.3 ± 15.4%; P = 0.05). X allele carriers self-reported higher levels of lower limb muscle pain (7 ± 2 vs 6 ± 2 cm; P = 0.02) than RR homozygotes at the end of the race. CONCLUSIONS: In comparison to RR homozygotes, X allele carriers for the R577X polymorphism of the ACTN3 gene presented higher values for typical markers of exercise-induced muscle damage during a competitive marathon. Thus, the absence of a functional α-actinin-3 produced by the X allele might induce higher levels of muscle breakdown during prolonged running events.

Influence of endurance running on calcaneal bone stiffness in male and female runners.

PURPOSE: The aim of this investigation was to determine the influence of endurance running on calcaneus bone stiffness in male and female runners. METHODS: A total of 122 marathoners (longer distance runners, men = 101; women = 21) and 81 half-marathon and 10-km runners (shorter distance runners; men = 48; women = 33), competing in an international running event, underwent an ultrasonographic assessment of the right and left calcaneus. Calcaneus bone stiffness was estimated using the measurements of the speed of sound (SOS) and broadband ultrasound attenuation (BUA). Seventy-five age-matched sedentary people served as the control group. RESULTS: Male and female longer distance runners and shorter distance runners presented higher values than sedentary counterparts in SOS (P < 0.05), and calcaneus stiffness (P < 0.05). Although there were no significant differences between longer distance and shorter distance runners in the ultrasonographic variables, longer distance runners presented greater effects size in SOS (1.00 vs. 0.93 males; 1.10 vs. 0.77 females), BUA (0.62 vs. 0.25 males; 0.89 vs. 0.20 females) and calcaneus stiffness (0.88 vs. 0.66 males; 1.20 vs. 0.60 females) than shorter distance endurance runners. CONCLUSION: Calcaneus bone stiffness was higher in all endurance runners compared to a sedentary control population. The volume of ground reaction forces which occur during endurance running might induce the adaptation of the calcaneus bone.

Muscle damage produced during a simulated badminton match in competitive male players.

The purpose of the study was to assess the occurrence of muscle damage after a simulated badminton match and its influence on physical and haematological parameters. Sixteen competitive male badminton players participated in the study. Before and just after a 45-min simulated badminton match, maximal isometric force and badminton-specific running/movement velocity were measured to assess muscle fatigue. Blood samples were also obtained before and after the match. The badminton match did not affect maximal isometric force or badminton-specific velocity. Blood volume and plasma volume were significantly reduced during the match and consequently haematite, leucocyte, and platelet counts significantly increased. Blood myoglobin and creatine kinase concentrations increased from 26.5 ± 11.6 to 197.3 ± 70.2 µg·L(-1) and from 258.6 ± 192.2 to 466.0 ± 296.5 U·L(-1), respectively. In conclusion, a simulated badminton match modified haematological parameters of whole blood and serum blood that indicate the occurrence of muscle fibre damage. However, the level of muscle damage did not produce decreased muscle performance.

Acute consumption of a caffeinated energy drink enhances aspects of performance in sprint swimmers.

This study investigated the effect of a caffeinated energy drink on various aspects of performance in sprint swimmers. In a randomised and counterbalanced order, fourteen male sprint swimmers performed two acute experimental trials after the ingestion of a caffeinated energy drink (3 mg/kg) or after the ingestion of the same energy drink without caffeine (0 mg/kg; placebo). After 60 min of ingestion of the beverages, the swimmers performed a countermovement jump, a maximal handgrip test, a 50 m simulated competition and a 45 s swim at maximal intensity in a swim ergometer. A blood sample was withdrawn 1 min after the completion of the ergometer test. In comparison with the placebo drink, the intake of the caffeinated energy drink increased the height in the countermovement jump (49.4 (SD 5.3) v. 50.9 (SD 5.2) cm, respectively; P<0.05) and maximal force during the handgrip test with the right hand (481 (SD 49) v. 498 (SD 43) N; P<0.05). Furthermore, the caffeinated energy drink reduced the time needed to complete the 50 m simulated swimming competition (27.8 (SD 3.4) v. 27.5 (SD 3.2) s; P<0.05), and it increased peak power (273 (SD 55) v. 303 (SD 49) W; P <0.05) and blood lactate concentration (11.0 (SD 2.0) v. 11.7 (SD 2.1) mM; P<0.05) during the ergometer test. The caffeinated energy drink did not modify the prevalence of insomnia (7 v. 7%), muscle pain (36 v. 36%) or headache (0 v. 7%) during the hours following its ingestion (P>0.05). A caffeinated energy drink increased some aspects of swimming performance in competitive sprinters, whereas the side effects derived from the intake of this beverage were marginal at this dosage.

The ingestion of a caffeinated energy drink improves jump performance and activity patterns in elite badminton players.

The aim of this study was to investigate the effectiveness of a caffeine-containing energy drink to enhance physical and match performance in elite badminton players. Sixteen male and elite badminton players (25.4 ± 7.3 year; 71.8 ± 7.9 kg) participated in a double-blind, placebo-controlled and randomised experiment. On two different sessions, badminton players ingested 3 mg of caffeine per kg of body mass in the form of an energy drink or the same drink without caffeine (placebo). After 60 min, participants performed the following tests: handgrip maximal force production, smash jump without and with shuttlecock, squat jump, countermovement jump and the agility T-test. Later, a 45-min simulated badminton match was played. Players' number of impacts and heart rate was measured during the match. The ingestion of the caffeinated energy drink increased squat jump height (34.5 ± 4.7 vs. 36.4 ± 4.3 cm; P < 0.05), squat jump peak power (P < 0.05), countermovement jump height (37.7 ± 4.5 vs. 39.5 ± 5.1 cm; P < 0.05) and countermovement jump peak power (P < 0.05). In addition, an increased number of total impacts was found during the badminton match (7395 ± 1594 vs. 7707 ± 2033 impacts; P < 0.05). In conclusion, the results show that the use of caffeine-containing energy drink may be an effective nutritional aid to increase jump performance and activity patterns during game in elite badminton players.

A 7-day oral supplementation with branched-chain amino acids was ineffective to prevent muscle damage during a marathon.

The aim of this study was to determine the effectiveness of a 7-day oral supplementation with branched-chain amino acids (BCAA) to prevent muscle damage during a marathon. Forty-six experienced runners were randomly divided into two groups, one with BCAA supplementation (n = 25, supplemented with 5 g day(-1) of powdered 1:0.5:0.5 leucine:isoleucine:valine, during the 7 days prior to the competition) and the other as a control group (n = 21, supplemented with an isocaloric placebo). Before the marathon race and within 3 min of finishing, leg muscle power was measured with a maximal countermovement jump and a urine sample was obtained. During the race, running pace was measured by means of a time-chip. Myoglobin concentration was determined in the urine samples as an indirect marker of muscle damage. A visual analog scale (0-10 points) was used to assess leg muscle pain during the race. In the BCAA group, the mean running pace during the marathon was similar to the control group (3.3 ± 0.4 vs. 3.3 ± 0.5 m s(-1), respectively, 0.98). The pre- to post-race reduction in muscle power was similar in both BCAA and control groups (-23.0 ± 16.1 vs. -17.3 ± 13.8 %, P = 0.13). Post-race urine myoglobin concentration was similar in both BCAA and control groups (5.4 ± 7.5 vs. 4.5 ± 8.6 µg mL(-1), P = 0.70). Finally, there were no differences between groups in the perceived muscle pain during the race (6 ± 1 vs. 5 ± 1 points, P = 0.80). A 7-day supplementation of BCAA (5 g day(-1)) did not increase the running performance during a marathon. Furthermore, BCAA supplementation was ineffective to prevent muscle power loss, muscle damage or perceived muscle pain during a marathon race.

The use of energy drinks in sport: perceived ergogenicity and side effects in male and female athletes.

The use of caffeine containing energy drinks has dramatically increased in the last few years, especially in the sport context because of its reported ergogenic effect. The ingestion of low to moderate doses of caffeinated energy drinks has been associated with adverse side effects such as insomnia or increased nervousness. The aim of the present study was to assess psycho-physiological changes and the prevalence of side effects resulting from the ingestion of 3 mg caffeine/kg body mass in the form of an energy drink. In a double-blind and placebo controlled experimental design, ninety experienced and low-caffeine-consuming athletes (fifty-three male and thirty-seven female) in two different sessions were provided with an energy drink that contained 3 mg/kg of caffeine or the same decaffeinated energy drink (placebo; 0 mg/kg). At 60 min after the ingestion of the energy drink, participants completed a training session. The effects of ingestion of these beverages on psycho-physiological variables during exercise and the rate of adverse side effects were measured using questionnaires. The caffeinated energy drink increased self-perceived muscle power during exercise compared with the placebo beverage (6·41 (sd 1·7) v. 5·66 (sd 1·51); P= 0·001). Moreover, the energy drink produced a higher prevalence of side effects such as insomnia (31·2 v. 10·4 %; P< 0·001), nervousness (13·2 v. 0 %; P= 0·002) and activeness (16·9 v. 3·9 %; P= 0·007) than the placebo energy drink. There were no sex differences in the incidence of side effects (P>0·05). The ingestion of an energy drink with 3 mg/kg of caffeine increased the prevalence of side effects. The presence of these side effects was similar between male and female participants.

Prospective and Retrospective Analysis of the Sporting Success of Elite Spanish High and Long Jumpers.

The aim of the present study was to analyze the sporting progression from U14 to senior categories of elite Spanish high and long jumpers. For prospective analysis, 300 athletes ranked top 20 at U14 were analyzed (153 female and 147 male). For retrospective analysis, 64 athletes ranked in the top 20 in the senior category were included (21 female and 43 male). Ranking positions were registered in each of the seasons where they presented records. Only 6.3% (19) of athletes who reached the top 20 at U14 became successful senior athletes [4.7% (14) of athletes maintained top 20 status throughout their sporting careers from U14 to senior]. The transition rate from U14 to U16 (35.7%) was the most severe drop down in consecutive categories (after this, it ranged from 47.8 to 66.7%). Of the senior top 20 athletes (64), most of them were already ranked top 20 at U16 (59.4%, 38), at U18 (62.5%, 40), at U20 (70.3%, 45) and at U23 (78.1%, 50). Nevertheless, only 34.4% (22) were top 20 when they were U14 athletes. Transition rates in the top 20 senior athletes ranged from 86.7 to 95.5%. Around one out of four (26.6%, 17) of the top 20 senior athletes maintained top 20 status throughout their sporting careers from U14 to the senior category. Although early success is not a good predictor of senior success, successful senior athletes excelled early on and were able to remain in top rankings throughout their sporting careers of national elite jumpers.

The 8:1:1 Supplementation of Branched-Chain Amino Acids in High-Intensity Training: A Case Study of the Protective Effect on Rhabdomyolysis.

INTRODUCTION: The increasing prevalence of high-intensity sports activities, notably the burgeoning popularity of CrossFit, underscores the contemporary significance of such physical pursuits. The discernible protective impact of branched-chain amino acids on muscle fatigue and injuries is emerging as a noteworthy area of investigation. Within the realm of sports, integrating BCAA supplementation into dietary practices holds promise for aiding athletes in their recovery, particularly in mitigating Delayed-Onset Muscle Soreness. METHODOLOGY: This study adopted an experimental pilot design with repeated measures, employing a controlled and randomized approach through double-blind procedures. The participant engaged in high-intensity activity, specifically the CrossFit Karen® test, which entailed executing 150 wall ball throws (9 kg) to a height of 3 m. The trial incorporated three randomized supplementation conditions: BCAAs in an 8:1:1 ratio or a 2:1:1 ratio or a placebo condition. The participant consumed 15 g daily for 7 days, commencing 72 h prior to the initial blood sample and the first Karen® test. RESULTS: In this study, BCAA supplementation at an 8:1:1 ratio demonstrated a discernible protective effect against muscular damage, as evidenced by creatine kinase values and ratings of perceived exertion.

"You Are Not Wrong About Getting Strong:" An Insight Into the Impact of Age Group and Level of Competition on Strength in Spanish Football Players.

OBJECTIVE: This study aimed to compare the maximum and rapid force production of Spanish football players and explore the differences between age group and level of competition. METHODS: A cross-sectional study was developed to evaluate the peak force (PF), relative PF, and rate of force development over 250 ms (RFD0-250) during the isometric midthigh pull between groups of football players based on age group (senior vs junior) and level of competition (national vs regional). Using a portable isometric rig, 111 football players performed 2 isometric midthigh-pull trials on a force plate. Two-way analysis of variance with Bonferroni post hoc correction was applied, and statistical significance was set at P ≤ .05. The PF, relative PF, and RFD0-250 0, 25, 50, 75, and 100 percentiles were also calculated and descriptively reported, separated by age group and level of competition. RESULTS: The analysis of variance revealed a significant main effect of the level of competition for the PF (P < .001), relative PF (P = .003), and RFD0-250 (P < .001). There was a significant main effect of age group for the PF (P < .001). There was a significant interaction effect of the age group × level of competition for relative PF (P = .014). National players were stronger than regional players on the PF and RFD0-250 (P < .001). Senior players were stronger than junior players for the PF (P < .001). CONCLUSIONS: Maximum and rapid force production are crucial for Spanish football players as they progress in both level of competition and age group. Practitioners should encourage young football players to prioritize strength development to improve their athletic performance.

Endurance running prevents the age-related decline of calcaneal bone stiffness.

This investigation presents a comparison of calcaneus bone stiffness of endurance runners of different ages and age-matched controls. We found that there was an age-associated decline in calcaneus bone stiffness in the control group while endurance runners prevented this decline, with a higher effect as the participants increased their age. PURPOSE: Previous investigations have found that endurance runners have higher bone mineral density and other bone quality variables in mechanically loaded bones. However, it is unknown if endurance running might counteract the decline in bone stiffness that occurs with age. The purpose of this study was to compare calcaneus bone stiffness of endurance runners of different ages to age-matched controls. METHODS: In a descriptive cross-sectional study, 182 endurance-trained male runners and 116 healthy untrained male controls underwent an ultrasonographic assessment of the calcaneus bone in the right and left heels. Calcaneal bone stiffness was calculated from assessments of the broadband ultrasound attenuation and the speed of sound. RESULTS: The line of best fit for the association between age and calcaneus stiffness was different between marathoners and controls (Z = - 2.1, P = 0.02). A two-way ANCOVA (condition × age) with body mass, and body mass index as covariates, revealed that there were main effects of condition (F = 26.8, P < 0.01) and age (F = 4.2, P < 0.01) for calcaneus stiffness, with a significant interaction between these two factors (F = 2.8, P = 0.03). The post hoc analysis revealed that calcaneus stiffness was significantly higher in marathoners of 40-44 years (121.5 ± 18.2 vs 101.1 ± 21.3 arbitrary units [A.U.], P = 0.01), 45-49 years (121.5 ± 19.7 vs 104.3 ± 13.4 A.U., P = 0.04), and > 50 years (111.2 ± 17.9 vs 92.4 ± 16.0 A.U., P < 0.01) than their untrained counterparts of the same age with no statistically significant differences in the remaining age groups. CONCLUSION: Endurance runners of > 40 years had higher values of calcaneus stiffness than controls, providing evidence to support the potential effect of endurance running to reduce the age-related decline on calcaneus bone stiffness.

Game Activity and Physiological Responses of Young Tennis Players in a Competition With Two Consecutive Matches in a Day.

PURPOSE: This study aimed to determine whether the game activity and physiological responses of young tennis players differed depending on the session of play (e.g., morning (MOR) vs. afternoon (AFT)) and the final match outcome (e.g., winners vs. losers), during a simulated competition with two matches on the same day. METHODS: Twelve well-trained male tennis players (14.5±0.8 years) took part in a simulated competition of two 3-set matches separated by 3 h. All the matches were video-recorded and the participants were monitored using 10 Hz global positioning (GPS) units including a heart-rate (HR) monitor. Effect size (ES) statistics were used to investigate the magnitudes of the differences. RESULTS: During the AFT matches, in absolute terms, players covered longer total distance (ES=moderate), ran more distance between 0 and ≤ 4m·s-1 (ES=small-to-large) compared to MOR matches. Total duration was also longer (ES=large) in the AFT, where the rest time between rallies was also longer (ES=very large). HR was similar during both AFT and MOR matches, but higher rates of perceived exertion (RPE) (ES=moderate) were reported in the AFT. Only peak running velocity was observed to be likely higher for losers compared to winners (ES=small). CONCLUSIONS: Game activity and physiological responses of young tennis players differ when two consecutive matches are played on the same day. These data might help to elucidate the need for specific pre-competition training loads and/or in-between match/session recovery strategies when facing overloaded competitions.

The effects of playing two consecutive matches in the shoulder rotational profiles of elite youth badminton players.

OBJECTIVE: The aim of the present study was to analyse the effects of playing two badminton matches on the same day on the shoulder profile (i.e., range of motion (ROM) and strength) of young badminton players. DESIGN: Cross-sectional study. SETTING: Indoor sports facility. PARTICIPANTS: Thirty-one elite junior badminton players (age 16.6 ±â€¯1.0 years, body mass 63.9 ±â€¯6.1 kg, height 174.8 ±â€¯6.1 cm), including 19 boys and 12 girls. MAIN OUTCOME MEASURES: Shoulder passive internal rotation (IR) and external rotation (ER) ROM as well as shoulder IR/ER maximal isometric strength were measured before and after a competition including two competitive matches. RESULTS: Significant decreases (p < 0.05) were found in the shoulder ROM (i.e., dominant and non-dominant ER ROMs as well as in the dominant and non-dominant total arc of motion [TAM]) in boys, while in girls, significant increases (p < 0.05) were found in the non-dominant ER absolute strength, with significant decreases were found in the non-dominant ER ROM and the non-dominant TAM. CONCLUSION: Playing two badminton matches on the same day led to gender-specific changes on the shoulder profile (i.e., ROM and strength) of young elite badminton players, with more impact on the shoulder profile of boys compared to girls.

Age and sex-related upper body performance differences in competitive young tennis players.

OBJECTIVE: The aims of this study were to analyze the shoulder functional profile of young male and female tennis players and to establish the relationship among physical variables and serve speed. METHODS: A total of 128 Spanish tennis players (Under-13 (n = 32/32 males/females) and Under-15 (n = 36/28 males/females), were tested during National training camps. Tests included passive shoulder range of motion (ROM) for both internal (IR) and external rotation (ER) and isometric strength (i.e., IR and ER) of the dominant/non-dominant shoulders, medicine ball throws (MBT), and serve speed. Age and sex pairwise comparisons were carried using the Hedges' g index (dg). RESULTS: Results showed age and sex effects on serve speed and all MBT, with males showing greater changes (1.51≤dg≤1.98) with age than females (0.92≤dg≤1.35; p<0.05). U15 males showed higher (p<0.05) absolute shoulder IR and ER strength than U13, with only significant differences between males and females in the U15. Regarding ROM, U15 males showed a decreased IR ROM compared to U13 (dg = -0.84; p<0.05) and higher significant IR bilateral deficit (dg = 0.51; p<0.05). The distances obtained in the different MBT were the variables more correlated to serve speed. CONCLUSION: The present results suggest that shoulder strength, medicine ball throws and serve speed increased along with age in young elite tennis players of both sexes. However, a decreased range of motion and bilateral deficit for glenohumeral internal rotation is evident in male under-15 tennis players. Muscle strength, power and shoulder range of motion are key factors for serve speed in young tennis players.