Joint-specific Postactivation Potentiation Enhances Serve Velocity in Young Tennis Players.

ABSTRACT: Baiget, E, Colomar, J, and Corbi, F. Joint-specific postactivation potentiation enhances serve velocity in young tennis players. J Strength Cond Res 37(4): 840-847, 2023-This study aimed (a) to analyze the influence of sport-specific postactivation potentiation (PAP) on serve velocity (SV) and serve accuracy (SA) in young tennis players, (b) to compare the PAP effects of 2 different conditioning activities (CA) on SV and SA, and (c) to explore if changes in SV would be related to tennis player's neuromuscular performance. Sixteen competition young tennis players performed 3 testing sessions in a randomized order. In the control session, subjects performed a warm-up protocol followed by the SV and SA tests. The experimental sessions involved 1 (shoulder internal rotation [SHIR]) or 2 (SHIR + shoulder flexion [SHF]) repetitions of a 5 second maximal voluntary isometric contraction (MVIC) executed before the SV and SA tests. Results showed a moderate significant (p = 0.037) difference between SV at control session and following the SHIR + SHF CA protocol at minute 0 (3.4 ± 4.6%; 4.6 km·h-1; ES = 0.711). Serve accuracy did not differ between CA protocols and control session at any time point. No significant relations were found between force-time curve parameters and SV percent changes at different recovery times. Performing 2, short (5 seconds), upper-limb, tennis joint-specific MVIC seems to enhance SV without negatively affecting SA in young competition tennis players. On the contrary, performing one MVIC does not seem to obtain the same effects. Moreover, tennis players with improved neuromuscular performance do not seem to exhibit a better predisposition to postactivation performance enhancement.

Effects of Maturation on Lower-Body Neuromuscular Performance in Youth Tennis Players.

ABSTRACT: Fernandez-Fernandez, J, Canós-Portalés, J, Martinez-Gallego, R, Corbi, F, and Baiget, E. Effects of maturation on lower body neuromuscular performance in youth tennis players. J Strength Cond Res 37(1): 167-173, 2023-The aim of this study was to examine the maturational status differences in neuromuscular performance of young tennis players. One hundred fifty-five junior tennis players (91 boys and 64 girls; age 13.1 ± 2.2 years, body mass 50.0 ± 12.2 kg, height 159.7 ± 12.4 cm, and estimated age at peak height velocity [PHV] 12.7 ± 1.6 years) participated in the study and were divided into pre-PHV (n = 57), circa-PHV (n = 50), and post-PHV (n = 48) groups. Physical tests included speed (5, 10, and 20 m), modified 5-0-5 change of direction (COD) test, hexagon test, and bilateral or unilateral countermovement jump (CMJ). The main results showed that compared with the post-PHV, pre-PHV players presented lower levels of performance in CMJs (p < 0.001; effect size [ES]: 0.76-0.88), linear sprints, and COD ability tests (p < 0.001; ES: 1.4-1.5). In addition, compared with circa-PHV, pre-PHV players also demonstrated lower performance levels in both linear sprints (p < 0.001; ES: 0.93-1.12) and COD abilities (p < 0.01; ES: 0.58-0.94). On the contrary, COD deficit (CODDEF) was significantly lower in the pre-PHV group than the circa-PHV (p < 0.001; ES: 0.76-0.79) and post-PHV (p < 0.001; ES: 1.04-1.05) groups. These results highlight the need to use the maturity stage (i.e., PHV) instead of chronological age as a more appropriate parameter when designing training programs. Furthermore, based on the differences found between groups, specific training strategies, such as neuromuscular training and COD workouts, related to the different maturation stages should be recommended.

Influence of anthropometric, ball impact and landing location parameters on serve velocity in elite tennis competition.

This study aimed (i) to analyse the associations between serve velocity (SV) and anthropometric, ball impact and landing location parameters in total serves (TS) and fastest serves (FS) performed during an ATP Tour event; (ii) to observe differences between first (S1) and second (S2) serves, and (iii) to determine a SV prediction model based on the relationship between the observed variables. Using Foxtenn technology, 30 S1 and 15 S2 were registered in 14 matches in twenty-one male professional tennis players. Ball impact (impact height [IH], impact projection angle [IPA] and relative impact height [RIH]), bounce landing (width and depth) location parameters, S1 and S2 SV in TS (TSV1 and TSV2) and FS (FSV1 and FSV2) alongside anthropometric characteristics of tennis players (body height [BH], body mass [BM] and body mass index [BMI]) were analysed. Significant moderate to large associations were found between BH and BM and TSV1, FSV1 and FSV2 (r = 0.315 to 0.593; p < 0.001), and between IH and IPA and TSV1 and TSV2 (r = 0.294 to -0.409; p < 0.001). BH and BM were the unique significant contributors of FS explaining 22 to 35% of FSV1 and FSV2. Only BM appears in the model to predict FSV1 and FSV2 (r2 = 0.48 and 0.21). We concluded that all three anthropometric, ball impact and bounce landing location parameters small to moderately influence TSV. Anthropometric parameters show an impact on SV when tennis players serve at or near maximal speed, highlighting the influence of BM above BH.

Effects of different maturity status on change of direction performance of youth tennis players.

The aim of this study was to examine the maturational status (i.e., peak height velocity [PHV]) differences in neuromuscular performance (i.e., vertical jump, linear sprint, change of direction (COD) using different tests, and change of direction deficit [CODD]) of young tennis players. One hundred and two tennis players (70 boys and 52 girls; age 13.9 ± 2.0 years, body mass 53.3 ± 12.7 kg, height 163.1 ± 11.9 cm) participated in the study and were divided into Pre-PHV (n = 26), Circa-PHV (n = 33) and Post-PHV (n = 43) groups. Testing included speed (5, 10, and 20 m), COD tests (i.e., modified 5-0-5, pro-agility and hexagon), and bilateral/unilateral countermovement jump (CMJ). Pre- and Circa-PHV players presented lower levels of performance in jumping ability (i.e., both bilateral and unilateral CMJs; P < 0.001; ES: 0.85 to 0.98), linear sprints (5 to 20 m; P < 0.05 to < 0.001; ES: 0.67 to 1.19) and COD ability tests (modified 5-0-5 test, pro-agility and hexagon) compared to the Post-PHV players. Moreover, Pre-PHV players presented lower CODD% (p < 0.05; ES: 0.68-0.72) than Post-PHV for both forehand and backhand sides, and Circa-PHV showed lower values in the CODD of the rolling situation to the forehand side (p < 0.05; ES: 0.58). Among the COD tests, the pro-agility test seems to be a simple, easy-to-implement and reliable test, which can provide interesting information about the COD with higher entry speeds. Moreover, specific training strategies related to the PHV and focused not only on the neuromuscular training and COD workouts, but also on maximizing motor skill proficiency, should be recommended.

Functional Threshold Power as an Alternative to Lactate Thresholds in Road Cycling.

ABSTRACT: Sitko, S, Cirer-Sastre, R, Corbi, F, and López-Laval, I. Functional threshold power as an alternative to lactate thresholds in road cycling. J Strength Cond Res 36(11): 3179-3183, 2022-This study assessed the relationship between functional threshold power (FTP) and 7 lactate landmarks (Dmax, modified Dmax, fixed blood lactate concentrations of 2 and 4 mmol·L -1 , lactate increases of 1 and 2 mmol·L -1 above baseline, and lactate increases of 1.5 mmol·L-1 above the point of minimum ratio between lactate and work rate) in a sample of 46 road cyclists with a wide range of fitness levels (age 38 ± 9 years, height 177 ± 9 cm, body mass 71.4 ± 8.6 kg, body mass index 22.7 ± 2.2 kg·m -1 , fat mass 7.8 ± 4%, and V̇ o2 max = 61.1 ± 9.1 ml·min -1 ·kg -1 ). The cyclists performed a graded exercise test in which power outputs (POs) at the lactate landmarks were identified. Functional threshold power was established as 95% of the PO during a 20-minute test. Significance was set as p < 0.05. Statistical analyses revealed large to very large correlations between PO, relative PO (RPO), and cadence at FTP and lactate thresholds (LTs) established through Dmax, modified Dmax, and fixed lactate concentrations of 4 mmol·L -1 ( r = 0.68-0.93). Significant differences ( p < 0.001) were also observed for PO and RPO at FTP, fixed blood lactate concentrations of 2 mmol·L -1 , and lactate increases of 1 mmol·L -1 above baseline. Therefore, although FTP estimated from a 20-minute test is strongly related to several lactate landmarks, caution is required when substituting this concept for LTs. This information will allow coaches, cyclists, and scientists to better choose assessments when attempting to estimate LT through power-based field testing.

Effects of isoinertial or machine-based strength training on performance in tennis players.

The objective of this study was to analyze the effects of two 8-week neuromuscular training (NMT) interventions on selected physical indicators in young tennis players. Twenty-four junior male tennis players were assigned to a machine-based (MG) (n = 8), flywheel (FG) (n = 8) or a control training group (CG) (n = 8). Tests at baseline, week 4 and 8 included: countermovement jump (CMJ); speed (S; 5, 10, 15 m); agility (right [AR] and left [AL]); serve velocity (SV) and medicine ball throws (MBT; overhead [O], forehand [FH], backhand [BH]). MG and FG attained large positive effects at week 4 in CMJ, S 10 m; AR, AL and MBT FH only in FG. Regarding inter- to post-test, MG achieved large positive effects in MBT O, FH and both groups in BH. Large negative effects appeared for FG in S 5 and 10 m and AR and AL. Both NMT interventions led to positive effects from baseline to week 4 measures in CMJ, S 5 m, 10 m and agility and at week 8 in MBT. Conducting the same NMT for a longer period of time did not lead to the same improvements and other negative effects in FG appeared. Results indicate that performing these interventions with little exercise variability or load management, especially after technical-tactical sessions, could interpose further beneficial outcomes and initial gains could be impaired.

Force-Time Curve Variable Outcomes Following a Simulated Tennis Match in Junior Players.

This study examined the alterations induced by a simulated tennis competition on maximal isometric voluntary contraction (MVC), peak rate of force development (PRFD) and rate of force development (RFD) at different stages of contraction. Twenty junior tennis players performed an 80-minute simulated tennis match and two (pre and post) muscular performance tests. Variables tested included MVC, PRFD and RFD at 50, 100, 150 and 200 ms while performing a 90º shoulder internal rotation (IR90), 90º shoulder external rotation (ER90), shoulder horizontal adduction (ADD), shoulder horizontal abduction (ABD) and isometric mid-thigh pull (IMTP). Serve velocity (SV) was also registered. No significant changes were found regarding MVC, PRFD or SV. Non-significant moderate effect size (ES) towards a decrease in the IR90 RFD at 50 ms could be observed (16%; ES = 0.5) alongside an increase in the ADD and IMTP RFD at 150 ms (-15.8%, -8.2%; ES = -0.53, -0.54) and IMTP RFD at 200 ms (-13%; ES = -0.54). Results indicate that MVC, PRFD, RFD at different time intervals and SV are unaltered following an 80-minute simulated match, possibly due to insufficient alterations triggered on key factors affecting the tested variables.

Characteristics of Pedaling Muscle Stiffness among Cyclists of Different Performance Levels.

Background and Objectives: The aim of the present study was to compare the impact of an incremental exercise test on muscle stiffness in the rectus femoris (RF), vastus lateralis (VL), biceps femoris (BF), and gastrocnemius (GL) among road cyclists of three performance levels. Materials and Methods: The study group consisted of 35 cyclists grouped according to their performance level; elite (n = 10; professional license), sub-elite (n = 12; amateur license), and recreational (n = 13; cyclosportive license). Passive muscle stiffness was assessed using myometry before and after an incremental exercise test. Results: There was a significant correlation between time and category in the vastus lateralis with stiffness increases in the sub-elite (p = 0.001, Cohen's d = 0.88) and elite groups (p = 0.003, Cohen's d = 0.72), but not in the recreational group (p = 0.085). Stiffness increased over time in the knee extensors (RF, p < 0.001; VL, p < 0.001), but no changes were observed in the knee flexors (GL, p = 0.63, BF, p = 0.052). There were no baseline differences among the categories in any muscle. Conclusions: Although the performance level affected VL stiffness after an incremental exercise test, no differences in passive stiffness were observed among the main muscles implicated in pedaling in a resting state. Future research should assess whether this marker could be used to differentiate cyclists of varying fitness levels and its potential applicability for the monitoring of training load.

Cardiac Biomarker Release After Exercise in Healthy Children and Adolescents: A Systematic Review and Meta-Analysis.

PURPOSE: The authors evaluated the impact of acute exercise and 24-hour recovery on serum concentration of cardiac troponins T and I (cTnT and cTnI) and N-terminal fragment of the prohormone brain natriuretic peptide (NT-proBNP) in healthy children and adolescents. The authors also determined the proportion of participants exceeding the upper reference limits and acute myocardial infarction cutoff for each assay. METHOD: Web of Science, SPORTDiscus, MEDLINE, ScienceDirect, and Scopus databases were systematically searched up to November 2017. Studies were screened and quality-assessed; the data was systematically extracted and analyzed. RESULTS: From 751 studies initially identified, 14 met the inclusion criteria for data extraction. All 3 biomarkers were increased significantly after exercise. A decrease from postexercise to 24 hours was noted in cTnT and cTnI, although this decrease was only statistically significant for cTnT. The upper reference limit was exceeded by 76% of participants for cTnT, a 51% for cTnI, and a 13% for NT-proBNP. Furthermore, the cutoff value for acute myocardial infarction was exceeded by 39% for cTnT and a 11% for cTnI. Postexercise peak values of cTnT were associated with duration and intensity (Q(3) = 28.3, P < .001) while NT-proBNP peak values were associated with duration (Q(2) = 11.9, P = .003). CONCLUSION: Exercise results in the appearance of elevated levels of cTnT, cTnI, and NT-proBNP in children and adolescents. Postexercise elevations of cTnT and NT-proBNP are associated with exercise duration and intensity.

Contralateral Effects After Unilateral Strength Training: A Meta-Analysis Comparing Training Loads.

There is solid evidence on the cross-training phenomenon, but the training load required to achieve it has yet to be established. The aim of this meta-analysis was to deduce which unilateral strength training load (duration, frequency, intensity, rest and type) would enable the biggest strength increases to be obtained in the inactive contralateral limb. The examined studies were limited to those written in the English language within the Web of Science, PubMed and SPORTDiscus databases. Ten of the 43 eligible studies were included, covering a total of 409 participants. The studies included in the meta-analysis showed a low risk of bias and had an estimated pooled effect size of 0.56 (95% CI from 0.34 to 0.78). Greater effect sizes were observed in lengthy protocols involving fast eccentric exercises using designs of 3 sets of 10 repetitions and a 2-minute rest time. Effect size did not relate to absolute volume, relative intensity, absolute duration and speed of execution. In conclusion, to optimize contralateral strength improvements, cross-training sessions should involve fast eccentric sets with moderate volumes and rest intervals.

The influence of a biopsychosocial educational internet-based intervention on pain, dysfunction, quality of life, and pain cognition in chronic low back pain patients in primary care: a mixed methods approach.

BACKGROUND: Low back pain is the highest reported musculoskeletal problem worldwide. Up to 90 % of patients with low back pain have no clear explanation for the source and origin of their pain. These individuals commonly receive a diagnosis of non-specific low back pain. Patient education is a way to provide information and advice aimed at changing patients' cognition and knowledge about their chronic state through the reduction of fear of anticipatory outcomes and the resumption of normal activities. Information technology and the expedited communication processes associated with this technology can be used to deliver health care information to patients. Hence, this technology and its ability to deliver life-changing information has grown as a powerful and alternative health promotion tool. Several studies have demonstrated that websites can change and improve chronic patients' knowledge and have a positive impact on patients' attitudes and behaviors. The aim of this project is to identify chronic low back pain patients' beliefs about the origin and meaning of pain to develop a web-based educational tool using different educational formats and gamification techniques. METHODS/DESIGN: This study has a mixed-method sequential exploratory design. The participants are chronic low back pain patients between 18-65 years of age who are attending a primary care setting. For the qualitative phase, subjects will be contacted by their family physician and invited to participate in a personal semi-structured interview. The quantitative phase will be a randomized controlled trial. Subjects will be randomly allocated using a simple random sample technique. The intervention group will be provided access to the web site where they will find information related to their chronic low back pain. This information will be provided in different formats. All of this material will be based on the information obtained in the qualitative phase. The control group will follow conventional treatment provided by their family physician. DISCUSSION: The main outcome of this project is to identify chronic low back pain patients' beliefs about the origin and meaning of pain to develop a web-based educational tool using different educational formats and gamification techniques. TRIAL REGISTRATION: ClinicalTrials.gov NCT02369120 Date: 02/20/2015.

Muscle Tone, Stiffness, and Elasticity in Elite Female Cyclists after Consecutive Short Competitions.

Background: For professional road cyclists, most overload injuries affect the lower limbs. They are mostly represented by contractures or muscle shortening, characterised by a variation of muscular tone, stiffness, and elasticity. This real-life study aimed to assess specific mechanical parameters in top-class female cyclists who participated in 3 races a week. Hypothesis. Muscle tone, stiffness, and elasticity will be affected immediately after competition and at the end of the week due to accumulated fatigue. Methods: Six professional cyclists were evaluated. This pilot study consisted of a controlled trial and three days of competition, with rest days between them. MyotonPRO was used to measure tone, stiffness, and elasticity in six leg muscles: vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF), biceps femoris (BF), lateral gastrocnemius (LG), and medial gastrocnemius (MG). Daily basal and pre- and postrace measures were carried through to the 3 races in a week. Results: The muscular tone of VL, VM, LG, and MG and the stiffness of VL, VM, RF, BF, LG, and MG decreased after races. VL and RF were mostly affected by (p=0.05) and (p=0.009), respectively. Basal elasticity improved over time until the last day. Conclusions: Muscle tone and stiffness decreased after a very intense and exhausting cycling endurance competition. Basal elasticity improved immediately after the race and continued this trend until the end of the week. More research is needed on changes in mechanical properties in competition and risk prevention of injuries.

Six-Week Joint-Specific Isometric Strength Training Improves Serve Velocity in Young Tennis Players.

PURPOSE: Evaluate the effects of 6 weeks of specific-joint isometric strength training on serve velocity (SV), serve accuracy (SA), and force-time curve variables. METHODS: Sixteen young competition tennis players were divided into an intervention (n = 10) or control group (n = 6). SV, SA, maximal voluntary isometric contraction, peak rate of force development, rate of force development, and impulse (IMP) at different time frames while performing a shoulder internal rotation (SHIR) or flexion were tested at weeks 0, 3, and 6. RESULTS: The intervention group showed significant increases in SV from pretest to posttest (7.0%, effect size [ES] = 0.87) and no variations in SA. Moreover, the intervention group showed significant increases from pretest to posttest in shoulder-flexion rate of force development at 150 (30.4%, ES = 2.44), 200 (36.5%, ES = 1.26), and 250 ms (43.7%, ES = 1.67) and in SHIR IMP at 150 (35.7%, ES = 1.18), 200 (33.4%, ES = 1.19), and 250 ms (35.6%, ES = 1.08). Furthermore, significant increases were found in shoulder-flexion rate of force development from intertest to posttest at 150 ms (24.5%, ES = 1.07) and in SHIR IMP at 150 (13.5%, ES = 0.90), 200 (19.1%, ES = 0.98), and 250 ms (27.2%, ES = 1.16). SHIR IMP changes from pretest to intertest were found at 150 ms (25.6%, ES = 1.04). The control group did not show changes in any of the tested variables. CONCLUSIONS: Six weeks of upper-limb specific-joint isometric strength training alongside habitual technical-tactical workouts results in significant increases in SV without SA detriment in young tennis players.

Performance Outcomes Following Isoinertial or Machine-Based Training Interventions in Female Junior Tennis Players.

PURPOSE: To evaluate changes in physical performance indicators after executing a flywheel or machine-based neuromuscular training program in young female tennis players. METHODS: Twenty-four players were divided into a machine-based  group (MG), flywheel  group (FG), and control group. Countermovement jump (CMJ), sprint time (5, 10, and 15 m), change-of-direction (COD) performance (right and left), medicine-ball throws (overhead, forehand, and backhand), and serve velocity were included as tests at baseline, week 4, and week 8. RESULTS: Both MG and FG largely improved from baseline to weeks 4 and 8 of training in CMJ (11.6, 10.6%; effect size [ES] = 1.24, 1.95). Also, sprint time 5 m and 10 m, COD performance-right, and COD performance-left improved moderately to very largely at week 4 in MG (-5.0% to -6.2%; ES = -1.79 to -4.19) and FG (-2.9% to -5.1%; ES = -1.13 to -1.64), respectively. Regarding medicine-ball throw, only FG improved moderately to very largely from weeks 4 to 8 in overhead (9.3%; ES = 1.46), forehand (8.0%; ES = 1.08), and backhand (6.1%; ES = 1.15). Serve velocity improved moderately from weeks 4 to 8 in MG (5.8%; ES = 0.87). CONCLUSIONS: Four weeks of the tested programs seem sufficient to improve physical determinants in young female participants. Greater improvements in CMJ and medicine-ball throw following flywheel neuromuscular training indicate the importance of including exercises that emphasize the stretch-shortening cycle and involve the entire kinetic chain. Performing the same intervention with no load adjustments may stall or even decrease performance in some parameters from weeks 4 to 8.

Possible relationship between the gut leaky syndrome and musculoskeletal injuries: the important role of gut microbiota as indirect modulator.

This article aims to examine the evidence on the relationship between gut microbiota (GM), leaky gut syndrome and musculoskeletal injuries. Musculoskeletal injuries can significantly impair athletic performance, overall health, and quality of life. Emerging evidence suggests that the state of the gut microbiota and the functional intestinal permeability may contribute to injury recovery. Since 2007, a growing field of research has supported the idea that GM exerts an essential role maintaining intestinal homeostasis and organic and systemic health. Leaky gut syndrome is an acquired condition where the intestinal permeability is impaired, and different bacteria and/or toxins enter in the bloodstream, thereby promoting systemic endotoxemia and chronic low-grade inflammation. This systemic condition could indirectly contribute to increased local musculoskeletal inflammation and chronificate injuries and pain, thereby reducing recovery-time and limiting sport performance. Different strategies, including a healthy diet and the intake of pre/probiotics, may contribute to improving and/or restoring gut health, thereby modulating both systemically as local inflammation and pain. Here, we sought to identify critical factors and potential strategies that could positively improve gut microbiota and intestinal health, and reduce the risk of musculoskeletal injuries and its recovery-time and pain. In conclusion, recent evidences indicate that improving gut health has indirect consequences on the musculoskeletal tissue homeostasis and recovery through the direct modulation of systemic inflammation, the immune response and the nociceptive pain.

Cardiac Troponin Release after Exercise in Healthy Young Athletes: A Systematic Review.

Cardiac troponin (cTn) is a recognized marker used to assess damage to the heart muscle. Actual research has indicated that the levels of cTn increase after doing exercise in individuals who are in good health, and this is believed to be a result of a normal cellular process rather than a pathological one. The main goal of this study was to investigate the evidence of a postexercise release of cTn in child and adolescent athletes (6-17.9 years old) of different ages, sex, and sports disciplines. The Web of Science, MEDLINE, and Scopus databases were used to conduct the research up to March 2023. Three hundred and twenty-eight records were identified from the databases, however, only twenty-three studies were included in the review after being screened and quality-assessed by two independent authors. The gender, age of the participants, maturational status, and training level of the participants, the timing of sample collection, the exercise modality, and the number of participants with values above the cut-off reference were the data analyzed. Males, older young people, and individual sports seemed to have higher levels of serum cTn after practice exercise. Different methodologies, analyzers, and cut-off reference values make it difficult to compare the data among studies.

Relationship between isometric force-time curve variables and serve velocity in young tennis players.

This study aimed to investigate the associations between serve velocity (SV), maximal absolute and relative isometric voluntary contraction (MVC and RMVC), peak rate of force development (PRFD), rate of force development (RFD) and impulse (IMP) at different stages of contraction (≤200 ms). Sixteen players performed four maximum isometric tests in positions involved in the tennis serve motion. Variables tested included MVC, PRFD, RFD and IMP at 50, 100, 150 and 200 ms while performing a 90º shoulder internal rotation (SHIR), shoulder flexion (SHF), horizontal shoulder abduction (SHABD) and an isometric mid-thigh pull (IMTP). Significant (p ≤ 0.05) moderate-to-very-large correlations were found between SV, MVC and PRFD. RFD at different time intervals showed positive associations with SV, except in the SHF0-200 ms and IMTP0-200 ms. Accordingly, IMP values positively correlated with SV in all positions except in the SHIR0-50 ms and the IMTP in late contraction stages. Results indicate that the combination of maximum isometric strength in several body positions involved in the serve kinetic chain alongside RFD and IMP in short periods of time (≤200 ms) positively influences SV in young participants.

Inter-Limb Muscle Property Differences in Junior Tennis Players.

The goal of this study was to investigate side-to-side differences and asymmetries regarding muscle characteristics in young tennis players. Thirty-four participants performed contractile property measurements (stiffness, tone, elasticity and time to relaxation) on the dominant and non-dominant extremities including nine muscle groups involved in the kinetic chain of main tennis strokes. Significant differences (p≤0.05) and small-to-moderate effect sizes for greater stiffness and tone were found for the dominant biceps femoris (-11.1% and -5.6%; ES=0.53 and 0.54) and the non-dominant vastus medialis (5.4% and 3.2%; ES=-0.33 and -0.41), while greater tone was present in the non-dominant pectoralis major (4.0%; ES=-0.56). Time to relaxation was increased in the dominant biceps femoris (10.3%; ES=-0.58), the non-dominant pectoralis major (5.1%; ES=-0.56) and the gastrocnemius (9.1%; ES=-0.5). The non-dominant infraspinatus and dominant rectus abdominis showed greater elasticity than contralateral muscles (9.9% and -8.0%; ES=-0.58 and 0.6, respectively). These results reflect the existence of small-to-moderate differences when comparing side-to-side values of contractile characteristics in a small amount of the muscle groups tested. However, passive measurements of a relaxed muscle do not seem to fully reflect possible adaptation and changes derived from gameplay in young tennis players.

Upper-Limb Force-Time Characteristics Determine Serve Velocity in Competition Tennis Players.

PURPOSE: (1) To analyze the associations between serve velocity (SV) and various single-joint upper-limb isometric force-time curve parameters, (2) to develop a prediction model based on the relationship between these variables, and (3) to determine whether these factors are capable of discriminating between tennis players with different SV performances. METHOD: A total of 17 high-performance tennis players performed 8 isometric tests of joints and movements included in the serve kinetic chain (wrist and elbow flexion [EF] and extension; shoulder flexion [SHF] and extension [SHE], internal [SHIR] and external rotation). Isometric force (IF), rate of force development (RFD), and impulse (IMP) at different time intervals (0-250 ms) were obtained for analysis. RESULTS: Significant (P < .05 to P < .01) and moderate to very large correlations were found between SV and isometric force (IF), RFD and impulse (IMP) at different time intervals in all joint positions tested (except for the EF). Stepwise multiple regression analysis highlighted the importance of RFD in the SHIR from 0 to 50 milliseconds and isometric force (IF) in the SHF at 250 milliseconds on SV performance. Moreover, the discriminant analyses established SHIR RFD from 0 to 30 milliseconds as the most important factor discriminating players with different serve performances. CONCLUSIONS: Force-time parameters in upper-limb joints involved in the serve moderate to very largely influence SV. Findings suggest that the capability to develop force in short periods of time (<250 ms), especially in the shoulder joint, seems relevant to develop high SV in competition tennis players.

Determinant Physical Factors of Tennis Serve Velocity: A Brief Review.

PURPOSE: To review the main physical aspects that could positively or negatively influence serve velocity (SV). METHODS: An examination of existing literature including studies analyzing positive (biomechanical aspects, anthropometrics, range of motion, strength, and power) and negative (competition-induced fatigue) associations to SV are summarized in this review. RESULTS: Aspects such as lower-leg drive, hip and trunk rotations, upper-arm extension, and internal rotation seem to be the major contributors to racquet and ball speed. Favorable anthropometric characteristics, such as body height, arm length, and a greater lean body mass, seem to positively influence SV. Also, strength indicators such as maximal isometric strength and rate of force development in specific joint positions involved in the kinetic chain alongside upper-body power seem to be related to faster serves. On the other hand, the effects of prolonged or repetitive match play may impair the aforementioned factors and negatively influence SV. CONCLUSIONS: Following specific serving models that seem to enhance velocity production and efficient motion is highly recommended. Moreover, achieving a higher impact point, alongside shifting body composition toward a greater lean body mass, will most likely aid toward faster serves. Programs aiming at improving maximal isometric strength and rate of force development in specific positions involved in the kinetic chain including stretch-shortening cycle predominance and the mimicking of the serve motion seem of great interest to potentially increase SV. Effective recovery and monitoring of these variables appear to be essential to avoid impairments produced by continued or repetitive competition loads.