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Context: The aim of this study was to investigate the effects of 8-week ballistic-strength-training program using a validated specific throwing device (ie, Arm/Shoulder Specific Strength Device), on isokinetic shoulders' rotation muscle-torques and ratios as well as range of motion in team handball players. Design: A repeated-measures experimental design with a randomized controlled trial was used. Methods: Twenty-six high-level competitive male U-19 team handball players were randomly assigned into training (TG, n = 15) and control (n = 11) groups. The TG undertook a twice a week for 8-week periodized throws program with an individually predetermined optimal load. The program incorporated shackled eccentric and concentric exercises using the Arm/Shoulder Specific Strength Device. Peak torques, functional, and conventional ratios for both arms at different angular velocities (60°·s−1, 180°·s−1, and 300°·s−1) were assessed over time and between groups, using an isokinetic dynamometer. Results: A significant improvement for TG (P <.01; d = 1.13 [moderate]; +20.2%) of the concentric peak torques for dominant arm in external rotation was observed at 300°·s−1. Significant (P <.05–.01) increases were also noted for nondominant arm at the 3 studied angular velocities. In addition, 300°·s−1 eccentric peak torques of the dominant arm and nondominant arm have significantly improved for both external and internal rotations (P <.05; d =.99 [moderate] and d = 1.21 [large]; +15.7% and + 17.9%, respectively) with small changes at the other angular assessed velocities. Posttraining, TG's dominant arm showed significant improvements (P <.05–.01) in functional and conventional ratios at all velocities. Notably, significant differences (P <.05–.01) were observed at 60°·s−1 and across all velocities when comparing the TG with the control group. TG showed significant increase for internal rotation and external rotation shoulder range of motions (P <.05; d = 1.22–1.27 [large]), +5.0% and +7.7%, respectively). Conclusions: The specific 8-week throwing training program on the Arm/Shoulder Specific Strength Device showed significant performance improvements in almost all assessed isokinetic concentric and eccentric peak torques as well as internal and external range of motion increase for both arms while ensuring rotator cuff torque ratios and shoulder mobility in team handball real sport-specific condition. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the accuracy of ChatGPT (Chat generative pretrained transformer), a large language model, in calculating sample size for sport-sciences and sports-medicine research studies. Methods: We conducted an analysis on 4 published papers (ie, examples 1–4) encompassing various study designs and approaches for calculating sample size in 3 sport-science and -medicine journals, including 3 randomized controlled trials and 1 survey paper. We provided ChatGPT with all necessary data such as mean, percentage SD, normal deviates (Zα/2 and Z1−β), and study design. Prompting from 1 example has subsequently been reused to gain insights into the reproducibility of the ChatGPT response. Results: ChatGPT correctly calculated the sample size for 1 randomized controlled trial but failed in the remaining 3 examples, including the incorrect identification of the formula in one example of a survey paper. After interaction with ChatGPT, the correct sample size was obtained for the survey paper. Intriguingly, when the prompt from Example 3 was reused, ChatGPT provided a completely different sample size than its initial response. Conclusions: While the use of artificial-intelligence tools holds great promise, it should be noted that it might lead to errors and inconsistencies in sample-size calculations even when the tool is fed with the necessary correct information. As artificial-intelligence technology continues to advance and learn from human feedback, there is hope for improvement in sample-size calculation and other research tasks. However, it is important for scientists to exercise caution in utilizing these tools. Future studies should assess more advanced/powerful versions of this tool (ie, ChatGPT4). [ABSTRACT FROM AUTHOR]

The authors reflect on a teamwork modeling method to achieve good performance management in elite football (soccer) and ensure the health and availability of players during games. The model focuses on key performance indicators (KPI) to improve the performance of players and the pillars of the model like creating a systematic monitoring system and establishing an appropriate training process.

Background: The effect of the 2020 COVID-19 lockdown on athlete sleep and training behavior is documented, albeit without a worldwide soccer-specific focus. Method: Soccer (football) players (N = 1639; 30 countries; age 22.5 [5.7] y; 81% ≤25 y; 56% male; 30% elite; 66% Muslim) answered a retrospective, cross-sectional questionnaire related to their behavioral habits before and during COVID-19 lockdown (survey period July to September 2020), including (1) Pittsburgh Sleep Quality Index PSQI, (2) Insomnia Severity Index (ISI), (3) bespoke questions about training behaviors, and (4) Muslim player focused sleep and training behavior questions. Results: During lockdown (compared to prelockdown), PSQI (P <.001; moderate effect size [ES]) and ISI (P <.001; moderate ES) scores were higher in the overall sample and in elite versus nonelite (PSQI: P <.05; small ES and ISI: P <.001; small ES), >25 years versus ≤25 years (PSQI: P <.01; small ES and ISI: P <.001; moderate ES), females versus males (PSQI: P <.001; small ES), <1 month versus >1 month lockdown (PSQI: P <.05; small ES and ISI: P <.05; small ES), and players maintaining versus reducing training intensity (PSQI: P <.001; moderate ES and ISI: P <.001; small ES). Muslim players (41%) reported unfavorable sleep and/or training behaviors during Ramadan in lockdown compared to lockdown outside of Ramadan. Conclusions: Specific subgroups appear more vulnerable to lockdown effects, with training-intensity maintenance moderating negative effects relative to sleep. Policy and support (respectful of subgroup nuances) during lockdown-like challenges that facilitate training (including intensity) appear prudent, given their favorable relationship with sleep, mental health, and physical health, in the present data and elsewhere. [ABSTRACT FROM AUTHOR]

Coronavirus disease 2019 (COVID-19) resulted in sporting event suspensions and cancellations, affecting competition calendars worldwide during 2020 and 2021. This challenged high-performance athletes' capacity to complete physical, technical, or tactical training during restricted movement measures (lockdown). With the Football World Cup organized in the last quarter of 2022, the past period of training and match disturbances challenged footballers concerning their performance and potential higher risk of injury at official matches' resumption. There has been considerable debate about the management of resuming professional football (soccer) during the COVID-19 pandemic. Governing bodies worldwide implemented measures to ensure a safe resumption of football. These precautionary measures aimed to protect the health of players, their support staff, and officials around the pitch and ensure the enjoyment of the event by spectators in the football stadiums. We have therefore narratively reviewed scientific papers about how football has resumed on the pitch and in the stands with special focus on the COVID-19 infection control strategies allowing footballers to perform again and supporters to enjoy the game after the 2020 global stop to sport. [ABSTRACT FROM AUTHOR]

Purpose: To survey elite athletes and practitioners to identify (1) knowledge and application of heat acclimation/acclimatization (HA) interventions, (2) barriers to HA application, and (3) nutritional practices supporting HA. Methods: Elite athletes (n = 55) and practitioners (n = 99) completed an online survey. Mann–Whitney U tests (effect size [ES; r]) assessed differences between ROLE (athletes vs practitioners) and CLIMATE (hot vs temperate). Logistic regression and Pearson chi-square (ES Phi [ϕ]) assessed relationships. Results: Practitioners were more likely to report measuring athletes' core temperature (training: practitioners 40% [athletes 15%]; P =.001, odds ratio = 4.0, 95% CI, 2%–9%; competition: practitioners 25% [athletes 9%]; P =.020, odds ratio = 3.4, 95% CI, 1%–10%). Practitioners (55% [15% athletes]) were more likely to perceive rectal as the gold standard core temperature measurement site (P =.013, ϕ =.49, medium ES). Temperate (57% [22% hot]) CLIMATE dwellers ranked active HA effectiveness higher (P <.001, r =.30, medium ES). Practitioners commonly identified athletes' preference (48%), accessibility, and cost (both 47%) as barriers to HA. Increasing carbohydrate intake when training in the heat was more likely recommended by practitioners (49%) than adopted by athletes (26%; P =.006, 95% CI, 0.1%–1%). Practitioners (56% [28% athletes]) were more likely to plan athletes' daily fluid strategies, adopting a preplanned approach (P =.001; 95% CI, 0.1%–1%). Conclusions: Practitioners, and to a greater extent athletes, lacked self-reported key HA knowledge (eg, core temperature assessment/monitoring methods) yet demonstrated comparatively more appropriate nutritional practices (eg, hydration). [ABSTRACT FROM AUTHOR]

Purpose: To survey soccer practitioners' recovery strategy: (1) use, (2) perceived effectiveness, and (3) factors influencing their implementation in professional soccer. Methods: A cross-sectional convenience sample of professional soccer club/confederation practitioners completed a web-based survey (April to July 2020). Pearson chi-square and Fisher exact tests with Cramer V (φ − c) assessed relationships and their strength, respectively, between the perceived effectiveness and frequency of strategy use. Results: A total of 80 soccer practitioners (13 countries) completed the survey. The 3 most important recovery objectives were "alleviating muscle damage/fatigue," "minimizing injury risk," and "performance optimization." The most frequently used strategies were active recovery, structured recovery day, extra rest day, massage, cold-water therapy, and carbohydrate provision (predominantly on match day and match day + 1). Relationships were identified between perceived effectiveness and frequency of strategy use for sleep medication (P <.001, φ − c = 0.48), carbohydrate provision (P =.007, φ − c = 0.60), protein provision (P =.007, φ − c = 0.63), an extra rest day (P <.001, φ − c = 0.56), and a structured recovery day (P =.049, φ − c = 0.50). Conclusions: The study demonstrates that professional soccer practitioners have a range of objectives geared toward enhancing player recovery. A disconnect is apparent between the perceived effectiveness of many recovery strategies and their frequency of use in an applied setting. Novel data indicate that strategies are most frequently employed around match day. Challenges to strategy adoption are mainly competing disciplinary interests and resource limitations. Researchers and practitioners should liaise to ensure that the complexities involved with operating in an applied environment are elucidated and apposite study designs are adopted, in turn, facilitating the use of practically effective and compatible recovery modalities. [ABSTRACT FROM AUTHOR]

Purpose: To compare the effect of a 20-minute nap opportunity (N20), a moderate dose of caffeine (CAF; 5 mg·kg−1), or a moderate dose of caffeine before N20 (CAF+N) as possible countermeasures to the decreased performance and the partial sleep deprivation–induced muscle damage. Methods: Nine male, highly trained judokas were randomly assigned to either baseline normal sleep night, placebo, N20, CAF, or CAF+N. Test sessions included the running-based anaerobic sprint test, from which the maximum (Pmax), mean (Pmean), and minimum (Pmin) powers were calculated. Biomarkers of muscle, hepatic, and cardiac damage and of enzymatic and nonenzymatic antioxidants were measured at rest and after the exercise. Results: N20 increased Pmax compared with placebo (P <.01, d = 0.75). CAF+N increased Pmax (P <.001, d = 1.5; d = 0.94), Pmin (P <.001, d = 2.79; d = 2.6), and Pmean (P <.001, d = 1.93; d = 1.79) compared with placebo and CAF, respectively. Postexercise creatine kinase increased whenever caffeine was added, that is, after CAF (P <.001, d = 1.19) and CAF+N (P <.001, d = 1.36). Postexercise uric acid increased whenever participants napped, that is, after N20 (P <.001, d = 2.19) and CAF+N (P <.001, d = 2.50) and decreased after CAF (P <.001, d = 2.96). Conclusion: Napping improved repeated-sprint performance and antioxidant defense after partial sleep deprivation. Contrarily, caffeine increased muscle damage without improving performance. For sleep-deprived athletes, caffeine before a short nap opportunity would be more beneficial for repeated sprint performance than each treatment alone. [ABSTRACT FROM AUTHOR]

Objectives: To investigate whether tethered swimming (TS) performed 8 minutes before a 50-m freestyle swimming sprint could be an effective postactivation potentiation method to improve performance in young swimmers. Methods: Fourteen regional-level male adolescent swimmers (age 13.0 [2.0] y; height 161.1 [12.4] cm; body mass 52.5 [9.5] kg) underwent 2 trial conditions in a randomized and counterbalanced order (1 experimental [TS], 1 control) on different days. During the experimental session, the participants performed a standard warm-up of 1200 m followed by a TS exercise, which consisted of 3 × 10-second maximal efforts of TS with 1-minute rests between bouts. In the control condition, the warm-up phase was immediately followed by 200 m at a moderate pace (same duration as the TS in the experimental session). Performance (time trial); biomechanical (stroke length), physiological (blood lactate concentrations), and psychophysiological (ratings of perceived exertion) variables; and countermovement-jump (CMJ) flight time were collected. Results: TS warm-up had no significant effect on 50-m swimming performance (P =.27), postexercise ratings of perceived exertion, stroke length, or CMJ flight time (P ≥.05). Blood lactate concentrations significantly increased at the end of the warm-up in the TS condition only (interaction effect: F1.91,29.91 = 4.91, P =.01, η2 =.27) and after the 50-m trial in both conditions (F1.57,20.41 = 62.39, P =.001, η2 =.82). Conclusions: The present study demonstrated that 3 × 10-second TS exercises performed 8 minutes prior to the event did not affect ratings of perceived exertion, stroke length, or CMJ flight time. In addition, tethered swimming did not affect 50-m freestyle sprint performance in young swimmers. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effects of napping after partial sleep deprivation (PSD) on reaction time, mood, and biochemical response to repeated-sprint exercise in athletes. Methods: Nine male judokas performed 4 test sessions in a counterbalanced and randomized order. Participants accomplished 1 control session after a normal sleep night (NSN) and 3 after PSD with (1) no nap, (2) -20-min nap (N20), and (3) -90-min nap (N90) opportunities. Test sessions included the running-based anaerobic sprint test, reaction time, Hooper index, and Epworth Sleepiness Scale. Muscle-damage biomarkers and antioxidant status were evaluated before and after exercise. Results: PSD decreased maximum (P < .001, d = 1.12), mean (P < .001, d = 1.33), and minimum (P < .001, d = 1.15) powers compared with NSN. However, N20 and N90 enhanced maximum power compared with PSD (P < .05, d = 0.54; P < .001, d = 1.06, respectively). Minimum power and mean power increased only after N90 (P < .001, d = 1.63; P < .001, d = 1.16, respectively). Epworth Sleepiness Scale increased after PSD (P < .001, d = 0.86) and decreased after N20 (P < .001, d = 1.36) and N90 (P < .001, d = 2.07). N20 reduced multiple-choice reaction time (P < .001, d = 0.61). Despite performance decrement, PSD increased postexercise aspartate aminotransferase (P < .001, d = 4.16) and decreased glutathione peroxidase (P < .001, d = 4.02) compared with NSN. However, the highest performances after N90 were accompanied with lesser aspartate aminotransferase (P < .001, d = 1.74) and higher glutathione peroxidase (P < .001, d = 0.86) compared with PSD. Conclusions: Napping could be preventive against performance degradation caused by sleep loss. A short nap opportunity could be more beneficial when the subsequent effort is brief and requires frequent decision making. However, a longer nap opportunity could be preventive against muscle and oxidative damage, even for higher performances. [ABSTRACT FROM AUTHOR]

Purpose: To explore the immediate (15-s post-warm-up) and the delayed (after 20 and 40 min of simulated volleyball play) effects of 2 different warm-up protocols—a stretching-free volleyball warm-up (NS) and a warm-up incorporating dynamic stretching (DS)—on subsequent change of direction (COD) performance in young elite volleyball players. Methods: Sixteen male players (age 16.88 [0.34] y, body mass 75.81 [5.41] kg, body height 1.91 [0.05] m, body mass index 20.84 [1.79] kg·m−2, and body fat percentage 9.48 [1.83]%) from the U-17 national volleyball team performed NS and DS on 2 different nonconsecutive days. During each testing session (NS and DS), half T-test performance measurements were performed after 5 minutes of a general warm-up (ie, baseline), immediately post-warm-up (after 15 s), and after 20 and 40 minutes of simulated volleyball play. Results: For DS, a significant improvement in COD performance (2.08%, P <.001) was observed after 20 minutes of play compared with the baseline values. In addition, COD performance recorded after 40 minutes of play was better than after 15-second post-warm-up (5.85%, P =.001). Inferential statistics showed better COD performance in the DS condition after 20 minutes of play (2.32%, likely negative, d = 0.61). Conclusions: Compared with NS, DS tended to affect the pattern of improvement of COD performance during play by intensifying and accelerating it. Consequently, to enhance COD performance for up to 40 minutes into the game, it is recommended that DS be incorporated to the warm-up preceding the match. [ABSTRACT FROM AUTHOR]

Purpose: To assess the technical and tactical demands of elite karate athletes in relation to 3 match sequences (ie, advantage, disadvantage, and drawing) and match outcome (ie, win/defeat).Methods: One hundred twenty elite seniors' (60 men and 60 women) World Karate Federation combats were analyzed during 2 World Championships (2012 and 2014). Specific karate attributes (strategy, technique, tactic, target, and effectiveness) were evaluated and classified into 3 sequences: advantage, disadvantage, and drawing. Results: Karatekas performed more combination techniques in disadvantage sequences than in drawing sequences (P =.011). A higher number of timed-attack actions were reported during advantage sequences than during drawing sequences (P =.048). Winners of the whole combat had higher lower-limb technique rate (1.0 [0.9] vs 0.1 [0.3]; P =.044) and less rate of timed attack (0.3 [0.5] vs 0.6 [1.0]; P =.030) than defeated karatekas during advantage and drawing sequences, respectively. Conclusions: Winners used higher lower-limb technique and less timed-attack rates than defeated karatekas in advantage and drawing sequences, respectively. Indeed, using lower-limb technique during advantageous situations could be a powerful strategy to increase the lead. Therefore, it seems fundamental for coaches of top elite karatekas to put their athletes in simulated situations and push them to increase their use of lower-limb techniques. [ABSTRACT FROM AUTHOR]

Purpose: Limb dominance and consequent between-limbs muscle strength in soccer players should be explored to determine a standard musculoskeletal profile to maintain and establish during screening protocols and postinjury rehabilitation. The primary aim of this review was to identify dominant- vs non-dominant-lower-extremity muscle-strength characteristics of healthy soccer players, with secondary aims to consider available between-limbs outcome measures and directions for future research. Methods: Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. Five electronic databases were used for study identification with guidance from a medical librarian. Inclusion criteria consisted of studies employing a cross-sectional design assessing soccer players of all ages, genders, and levels of play that identified limb dominance and associated lower-extremity muscle strength as a main purpose of the experiment. Results: The literature search identified 3471 articles. After screening titles, abstracts, and full texts, 17 articles were included in the review. Peak torques and hamstring-to-quadriceps ratios via isokinetic dynamometry were commonly used, and subsequent meta-analyses were conducted to yield remarkable between-limbs symmetry. Additional results of individual studies also demonstrate symmetry, except 1 article of velocity-dependent measures that reported greater strength in the dominant limb. Conclusions: In soccer, between-limbs muscle strength measured by maximal isokinetic dynamometry demonstrates symmetry across ages, genders, and levels of play. Future testing using alternative measures that more specifically replicate the movement demands of soccer players may further classify between-limbs characteristics. [ABSTRACT FROM AUTHOR]

Purposes: To determine actions during bouts that generate serious enough injury to stop the bout; verifying the injury incidence, types, and prevalence of doctor stoppages (doc-stoppage); and identify potential risk factors by analyzing technical-tactical profiles for injury in sanctioned mixed martial arts bouts taking place over a 12-y period. Methods: This research analyzed 440 paired mixed martial arts matches separated by doc-stoppage (n = 220) and no doc-stoppage (n = 220) from 2002 to 2014. Technical knockouts for doc-stoppage were diagnosed and managed by attending ringside doctors, and the time–motion variables were categorized into total combat time separated by low- or high-intensity activities per round, stand-up, or groundwork actions, P ≤.05. Results: The main cause of injuries in doc-stoppage situations was due to facial injuries (>90%), with 87.1% occurring after striking actions during the second round. Lacerations were the leading type of injury, which occurred with 80% frequency. The results showed differences between doc-stoppage and no doc-stoppage for standing combat with low-intensity actions (130.6 [8.5] s vs 83.3 [6.9] s for first round; 115.7 [10.5] s vs 100.1 [9.6] s for second round, and 121.5 [19.5] s vs 106.3 [11.7] s for third round) and total strike attempts (34.5, 23.0–51.8 vs 25.0, 12.0–40.8); in standing combat, head strike attempts (21, 10–33 vs 11, 4–21) and body strikes (2.5, 1.0–5.8 vs 1.0–2), and in groundwork combat, head strikes landed (0.0–3.0 vs 0.0–5.0). Conclusions: This research showed higher values of strike attempts with 2 main orientations, namely the head (on the ground and in stand-up actions) and body (in stand-up actions), and may provide important information regarding the technical knockout and when it can be called by officials supervising mixed martial arts bouts. [ABSTRACT FROM AUTHOR]

The authors comment on the postponement/cancellation of sporting events around the world, including the 2020 summer Olympic Games caused by the coronavirus disease-2019 (COVID-19) pandemic. Topics covered include the problems posed to sports by the social protocols instituted in response to pandemic present, the ability of sport science to help minimize the impact of COVID-19 given its contribution to competitive sport, and the opportunities presented to sports by the health crisis.

Purpose: To evaluate the concept of decisive moment (DM) as a novel analysis approach providing insights into factors leading to successful high-performance kumite karate outcomes using time–motion variables. DM represents the moment from which 1 of the 2 opponents uninterruptedly dominates the other until the end of the fight. Methods: A total of 120 elite seniors (60 men and 60 women) World Karate Federation combats were analyzed during 2 World Championships (2012 and 2014). Specific characteristics of karate combat (strategy, technique, tactic, target, and effectiveness) were evaluated and classified in 3 sections: at, before, and after DM. Results: DM occurred at about 49% (32.8%) of bout duration. Up to DM no clearly identifiable differences in performance characteristics were found between winners and losers. At and after DM, an offensive strategy with focus on upper-limb techniques, attack and counterattack, targeting the head showed highest potential to achieve and maintain dominance and to win. After DM, losers showed increasingly reactive techniques, mainly timed attacks and combinatory techniques. Conclusion: The DM concept presents a novel approach to time–motion analysis, which for the first time allowed identification of clear discriminating factors of success and defeat in kumite karate at the highest performance level. [ABSTRACT FROM AUTHOR]

The authors reflect on their aspirations to help improve the quality of statistics in sport science. Among the recommendations are collaboration with statisticians or related methodologists to reduce possible errors in design, analysis and reporting of research, provision of data visualization for statistical models, and inclusion of multiple testing methods.

Purpose: To examine the effects of 3 d of intermittent fasting (3d-IF: abstaining from eating/drinking from dawn to sunset) on physical performance and metabolic responses to repeated sprints (RSs). Methods: Twenty-one active males performed an RS test (2 sets: 5 x 5-s maximal sprints with 25 s of recovery between and 3 min of recovery between sets on an instrumented treadmill) in 2 conditions: counterbalanced fed/control session (CS) and fasting session (FS). Biomechanical and biochemical markers were assessed preexercise and postexercise. Results: Significant main effects of IF were observed for sprints: maximal speed (P = .016), mean speed (P = .015), maximal power (P = .035), mean power (P = .049), vertical stiffness (P = .032), and vertical center-of-mass displacement (P = .047). Sprint speed and vertical stiffness decreased during the 1st (P = .003 and P = .005) and 2nd sprints (P = .046 and P = .048) of set 2, respectively. Postexercise insulin decreased in CS (P = .023) but not in FS (P = .230). Free-fatty-acid levels were higher in FS than in CS at preexercise (P < .001) and at postexercise (P = .009). High-density lipoprotein cholesterol (HDL-C) was higher at postexercise in FS (1.32 ± 0.22 mmol/L) than in CS (1.26 ± 0.21 mmol/L, P = .039). The triglyceride (TG) concentration was decreased in FS (P < .05) compared with CS. Conclusions: 3d-IF impaired speed and power through a decrease in vertical stiffness during the initial runs of the 2nd set of RS. The findings of the current study confirmed the benefits of 3d-IF: improved HDL-C and TG profiles while maintaining total cholesterol and low-density lipoprotein cholesterol levels. Moreover, improving muscle power might be a key factor to retain a higher vertical stiffness and to partly counteract the negative effects of intermittent fasting. [ABSTRACT FROM AUTHOR]

Purpose: To examine differences between ground-reaction-force (GRF)-based parameters collected from 5 types of plyometric push-ups. Between-trials reliability and the relationships between parameters were also assessed. Methods: Thirty-seven highly active commando soldiers performed 3 trials of 5 variations of the plyometric push-up in a counterbalanced order: standard countermovement push-up (SCPu), standard squat push-up (SSPu), kneeling countermovement push-up (KCPu), kneeling squat push-up (KSPu), and drop-fall push-up (DFPu). Vertical GRF was measured during these exercises using a portable Kistler force plate. The GRF applied by the hands in the starting position (initial force supported), peak GRF and rate of force development during takeoff, flight time, impact force, and rate of force development impact on landing were determined. Results: During standard-position exercises (SCPu and SSPu) the initial force supported and impact force were higher (P < .001) than with kneeling exercises (KCPu, KSPu, and DFPu). The peak GRF and rate of force development during takeoff were higher (P < .001) in the countermovement push-up exercises ([CMP] SCPu, KCPu, and DFPu) than squat push-up exercises ([SP] SSPu and KSPu). Furthermore, the flight time was greater (P < .001) during kneeling exercises than during standard-position exercises. A significant relationship (P < .01) between impact force and the rate of force development impact was observed for CMP and SP exercises (r = .83 and r = .62, respectively). The initial force supported was also negatively related (P < .01) to the flight time for both CMP and SP (r = -.74 and r = -.80, respectively). It was revealed that the initial force supported and the peak GRF during takeoff had excellent reliability; however, other parameters had poor absolute reliability. Conclusions: It is possible to adjust the intensity of plyometric push-up exercises and train athletes' muscle power by correctly interpreting GRF-based parameters. However, caution is required as some parameters had marginal absolute reliability. [ABSTRACT FROM AUTHOR]

Purpose: To determine the performance aspects (time--motion and technical-tactical analysis) of top-level low-kick kickboxers according to gender, weight category, combat round, and match outcome. Methods: Seventy-two kickboxers (44 male, 28 female) were studied. Thirty-six bouts (male = 61, female = 41 rounds) were analyzed using a time--motion system. Time structure was classified into 3 phases: preparatory-activity time (PT), fighting time (FT), and stoppage time (ST). Results: Referee decisions caused an overall effort:pause ratio (E:P) of ~1:1.5, with a significant difference between weight categories (light and middleweights = 1:1.5, heavyweight = 1:1). This ratio was ~1:6 when high-intensity actions--to-pause activities were considered. Significant differences were also observed between rounds (all P < .001), with 1st-, 2nd-, and 3rd-round E:Ps of 1:1, 1:1.5, and ~1:2, respectively. The relative times of FT and PT, total attacking actions, upper-limb actions, number of technical actions performed on the head, and the number of high-intensity actions were higher in males than females (all P = .05). Males performed more jab-cross actions and fewer low kicks than females (P < .001). Males used upper-limb (63.4%) more than lower-limb techniques (36.6%), targeting the head (56.9%) more than the body/leg (43.1%), with no significant difference from females (P > .05). E:P was similar between winners and losers. However, the numbers of technical actions performed on the head, counterattack actions, jab-cross technique, and total punches were higher in winners than losers (all P < .05). Conclusion: Training programs need to be adapted to the specific requirements of kickboxers' weight categories and gender to develop the technical-tactical abilities that improve athletes' chances of winning. [ABSTRACT FROM AUTHOR]

Purpose: To examine the relation between game performance, physiological responses, and field-test results in Tunisian basketball referees. Methods: Computerized time-motion analysis, heart rate (HR), and blood lactate concentration [La-] were measured in 15 referees during 8 competitive games (under-19-y-old Tunisian league). Referees also performed a repeated-sprint test (RSA), Yo-Yo Intermittent Recovery Test level 1 (YYIRTL1), agility T-test, and 30-m sprint with 10-m lap time. Computerized video analysis determined the time spent in 5 locomotor activities (standing, walking, jogging, running, and sprint), then grouped in high-, moderate-, and low-intensity activities (HIAs, MIAs, and LIAs, respectively). Results: YYIRTL1 performance correlated with (1) total distance covered during the 4th quarter (r = .52, P = .04) and (2) distance covered in LIA during all game periods (P < .05). Both distance covered and time spent in MIA during the 1st quarter were negatively correlated with the YYIRTL1 performance (r = -.53, P = .035; r = -.67, P = .004, respectively). A negative correlation was found between distance covered at HIA during the 2nd half (3rd quarter + 4th quarter) and fatigue index of the RSA test (r = -.54, P = .029). Mean HR (expressed as %HRpeak) during all game periods was correlated with YYIRTL1 performance (.61 ≤ r < .67, P < .01). Conclusions: This study showed that (1) the YYIRTL1 performance is a moderate predictor of game physical performance in U-19 basketball referees and (2) referees' RSA correlates with the amount of HIA performed during the 2nd half, which represents the ability to keep up with play. [ABSTRACT FROM AUTHOR]

The authors discuss some important issues to consider in order to succeed as an athlete. Topics discussed include the 1981 film "Chariots of Fire," the ability of elite athletes to tolerate large physical loads and recover in a timely way, and contribution of sports scientists as members of coach-led teams.

An introduction is presented in which the editor discusses various reports within the issue on topics including maturation-related changes in running performance, gastrointestinal hormones, and impact of eccentric muscle actions on jump performance.

Purpose: To examine the concurrent validity and absolute and relative reliabilities of a commando-specific power test. Participants: 21 antiterrorism commandos. Methods: All participants were assessed on a 5-m rope-climbing test (RCT) and the following tests: pull-ups, push-ups, estimated-1-repetition-maximum (est-1RM), medicine-ball put, and handgrip-strength test. The stopwatch method related to the execution time (ET) was validated by comparison with video motion analysis. The best individual attempt of 3 trials was kept for analysis, and the performance was expressed in absolute power output (APO) and body-mass relative power output (RPO). Results: Stopwatch assessment had an excellent criterion validity (r = .99, P < .001), intraclass correlation coefficient (ICC3,1) of .98, standard errors of measurement (SEM%) of 1.19%, bias ± the 95% limits of agreement of 0.03 ± 0.26 s, and minimal detectable change (MDC95) of 0.51 s. The ET, APO, and RPO were significantly correlated (P < .05) with all cited tests (absolute-value r range .55-.98), while est-1RM was not significantly correlated with the other tests. Test-retest reliability coefficients were excellent for ET, APO, and RPO (ICC3,1 > .90). The SEM% values for the ET, APO, and RPO were all under 5% (range 3.73-4.52%), all being smaller than the corresponding smallest worthwhile change. The coefficients of variation for the ET, APO, and RPO were all under 10%. %MDC95 ranged from 10.37% to 12.53%. Conclusions: Considering the strong concurrent validity and excellent test-retest reliability, the RCT is simple to administer, has ecological validity, and is a valid specific field test of upper-body power for commandos and, in addition, can be accurately assessed with a stopwatch. [ABSTRACT FROM AUTHOR]

PURPOSE: This study determined the validity and reliability of a new specific field test that was based on the scientific data from the latest research. METHODS: Seventeen international-level karatekas participated in the study: 14 men (age 24.1 ± 4.6 y, body mass 65.7 ± 10.8 kg) and 3 women (age 19 ± 3.6 y, body mass 54.1 ± 0.9 kg). All performed the new karate-specific test (KST) 2 times (test and retest sessions were carried out on separated occasions 1 wk apart). Thirteen men also performed a laboratory test to assess maximal oxygen uptake (VO2max). RESULTS: Test-retest results showed the KST to be reliable. Peak oxygen uptake (VO2peak), peak heart rate (HRpeak), blood lactate concentration, rating of perceived exertion, and time to exhaustion (TE) did not display a difference between the test and the retest. The SEM and ICC for relative and absolute VO2peak and TE were <5% and >.90, respectively. Significant correlations were found between VO2peak (mL • kg-1 • min-1) and TE measured from the KST (r = .71, 95%CI 0.35-0.88, P < .0001). There was also no significant difference between VO2peak measured from the KST and VO2max recorded from the cycle-ergometer laboratory test (55.1 ± 4.8 vs 53.2 ± 6.6 mL • kg-1 • min-1, respectively; t = -1.85, df = 12, P = .08, dz = 0.51 [small]). The Bland and Altman analyses reported a mean difference (bias) ± the 95% limits of agreement of 1.9 ± 7.35 mL • kg-1 • min-1. CONCLUSIONS: This study showed that the new KST test, with effort patterns replicating real karate combat sessions, can be considered a valid and reliable karate-specific field test for assessing karatekas' endurance fitness. [ABSTRACT FROM AUTHOR]

The aim of this study was to measure and compare physiological and time–motion variables during karate fighting and to assess eventual differences between winners and defeated elite karatekas in an ecologically valid environment. Methods: Fourteen elite male karatekas who regularly participated in national and international events took part in a national-level competition. Results: There were no significant differences between winners and defeated karatekas regarding all the studied variables. Karatekas used more upper-limb (76.19%) than lower-limb techniques (23.80%). The kisami-zuki represented the most frequent technique, with 29.1% of all used techniques. The duration of each fighting activity ranged from <1 s to 5 s, with 83.8% ± 12.0% of the actions lasting less than 2 s. Karatekas executed 17 ± 7 high-intensity actions per fight, which corresponded to ~6 high-intensity actions per min. Action-to-rest ratio was about 1:1.5, and high-intensityaction- to-rest ratio was ~1:10. The mean blood lactate response at 3 min postcombat (Lapost) elicited during karate fighting was 11.18 ± 2.21 mmol/L (difference between Lapre and Lapost = 10.01 ± 1.81 mmol/L). Mean heart rate (HR) was 177 ± 14 beats/min (91% ± 5% of HRpeak). Karatekas spent 65% of the time exercising at HR >90% of the individual HRpeak. Conclusion: Karatekas predominantly use upper-limb karate techniques. Karate’s nature is intermittent, with fighting activities representing ~6% of total combat’s duration and ~84% of actions lasting less than 2 s, with ~21-s mean time interval in between. Kumite combat sessions induced high La and near-maximal cardiovascular strain. Other key success factors should be investigated to properly discriminate winners and defeated athletes. [ABSTRACT FROM AUTHOR]

The authors discuss projects that are aimed at discovering genomics-based biomarkers with an adequate predictive power. Topics mentioned include the role of the biological and genetic makeup of an athlete in exercise physiology in terms of performance, the impact of exercise on the human proteome, and the relationship between internal and external load indicators during a football season.

The effect of endurance interval training (IT) on hematocrit (Ht), hemoglobin (Hb), and estimated plasma- volume variation (PVV) in response to maximal exercise was studied in 15 male subjects (21.1 ± 1.1 y ; control group n = 6, and training group, n = 9). The training group participated in interval training 3 times a week for 7 wk. A maximal graded test (GXT) was performed to determine maximal aerobic power (MAP) and maximal aerobic speed (MAS) both before and after the training program. To determine Ht, Hb concentration, and lactate concentrations, blood was collected at rest, at the end of GXT, and after 10 and 30 min of recovery. MAP and MAS increased significantly (P < .05) after training only in training group. Hematocrit determined at rest was significantly lower in the training group than in the control group after the training period (P < .05). IT induced a significant increase of estimated PVV at rest for training group (P < .05), whereas there were no changes for control group. Hence, significant relationships were observed after training between PVV determined at the end of the maximal test and MAS (r= .60, P < .05) and MAP(r = .76, P< .05) only for training group. In conclusion, 7 wk of IT led to a significant increase in plasma volume that possibly contributed to the observed increase of aerobic fitness (MAP and MAS). [ABSTRACT FROM AUTHOR]

Purpose: This study examined the effects of Ramadan on cycling repeated-sprint ability (RSA) and corresponding diurnal variations. Methods: Twelve active men performed an RSA test (5 x 6-s maximal sprints interspersed with 24 s passive recovery) during morning and afternoon sessions 1 wk before Ramadan (BR), during the second (R2) and the fourth (R4) weeks of Ramadan, and 2 wk after Ramadan (AR). Maximal voluntary contraction was assessed before (MVCpre), immediately after (MVCpost), and 5 min after the RSA test (MVCpost5). Moreover, hematocrit, hemoglobin, and plasma sodium and potassium (K+) concentrations were measured at rest and after the RSA test and MVCpost. Results: Overall, peak power (Ppeak) during the RSA test decreased throughout the 5 sprints. Ppeak measured in the first sprint and MVCpre were lower during Ramadan than BR in the afternoon (P < .05) and higher in the afternoon than the morning BR and AR (P < .05). However, this diurnal rhythmicity was not found for the last 4 sprints' Ppeak, MVCpost, and MVCpost5in all testing periods. Furthermore, the last 4 sprints' Ppeak, MVCpost, MVCpost5, and morning MVCpre were not affected by Ramadan. [K+] measured at rest and after the RSA test and MVCpost were higher during Ramadan than BR in the afternoon (P < .05) and higher in the afternoon than the morning during Ramadan (P < .05). Conclusions : Fatigability is higher in the afternoon during Ramadan, and, therefore, training and competition should be scheduled at the time of day when physical performance is less affected. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the effect of time-of-day-specific training on the diurnal variations of short-term performances in boys. Twenty-four boys were randomized into a morning-training-group (07:00-08:00h; MTG), an evening-training- group (17:00-18:00h; ETG) and a control-group (CG). They performed four tests of strength and power (unilateral isometric maximal voluntary contraction of the knee extensor muscles, Squat-Jump, Counter-Movement-Jump and Wingate tests) at 07:00 and 17:00h just before (T0) and after 6 weeks of resistance training (T1). In T0, the results revealed that short-term performances improved and oral temperature increased significantly from morning to afternoon (amplitudes between 2.36 and 17.5% for both oral temperature and performances) for all subjects. In T1, the diurnal variations of performances were blunted in the MTG and persisted in the ETG and CG. Moreover, the training program increase muscle strength and power especially after training in the morning hours and the magnitude of gains was greater at the time-of-day-specific training than at other times. In conclusion, these results suggest that time-of-day-specific training increases the child's anaerobic performances specifically at this time-of-day. Moreover, the improvement of these performances was greater after morning than evening training. [ABSTRACT FROM AUTHOR]

The objective of this study was to examine the response and recovery to a single set of maximal, low and high angular velocity isokinetic leg extension-flexion contractions with boys. Sixteen boys (11-14 yrs) performed 10 isokinetic contractions at 60°.s-1 (Isok60) and 300°.s-1 (Isok300). Three contractions at both velocities, blood lactate and ratings of perceived exertion were monitored pretest and at 2, 3, 4, and 5 min of recovery (RI). Participants were tested in a random counterbalanced order for each velocity and recovery period. Only a single contraction velocity (300°.s-1 or 60°.s-1) was tested during recovery at each session to remove confounding influences between the recovery intervals. Recovery results showed no change in quadriceps' power at 300°.s-1, quadriceps' power, work and torque at 60°.s-1 and hamstrings' power and work with 60°.s-1. There was an increase during the 2 min RI in hamstrings' power, work and torque and quadriceps' [ABSTRACT FROM AUTHOR]

The month-long diurnal Ramadan fast imposes a major challenge to Islamic athletes. Sporting events are programmed throughout the year, with the result that training and competition are often scheduled during Ramadan. The small numbers of well-controlled studies that have examined the effects of Ramadan on athletic performance suggest that few aspects of physical fitness are negatively affected, and only modest decrements are observed. Whereas subjective feelings of fatigue and other mood indicators are often cited as implying additional stress on the athlete throughout Ramadan, most studies show these measures may not be reflected in decreases in performance. The development and early implementation of sensible eating and sleeping strategies can greatly alleviate the disruptions to training and competitiveness, thus allowing the athlete to perform at a high level while undertaking the religious intermittent fast. Nevertheless, further research is required to understand the mechanisms and energy pathways that allow athletes to maintain their performance capacities during Ramadan, and which factors are responsible for the observed decrements in performance of some individuals. [ABSTRACT FROM AUTHOR]

Purpose: To study the relationship between performance and exercise-induced arterial hypoxemia (EIAH), 5 internationally ranked (INT) and 8 regionally ranked (REG) triathletes performed cycle-run successions (CR) and control runs (R) in competitionlike conditions: at ≈75% VO2max. Methods: Ventilatory parameters and oxyhemoglobin saturation (SpO2) data were collected continuously. Arteriolized partial pressure in O2 (PaO2) and alveolar ventilation (VA) were measured before and after cycling (CRcycle), the successive run (CRrun), and R. Pulmonary diffusing capacity (DLco) was measured at rest and 10 minutes post-CR. Training and short-distance triathlon data were collected. Results: INT showed significantly greater experience than REG in competition years (P > .05), training regimen (P > .05), and swimming (P > .05), and cycling (P > .05) volumes; running showed a trend (P < .06). Cycling, running, and total triathlon performances were significantly higher in INT than REG (P > .01). SpO2 during CR dropped significantly more in INT than in REG. Both groups showed significant inverse correlations between the magnitude of the SpO2 change from CRcycle to CRrun and the triathlon running time (r = -0.784; P < .05 and r = -0.699; P < .05; respectively). When compared with CRcycle, PaO2 significantly decreased and VA significantly increased after CRrun and R in both groups (P < .01). DLco significantly dropped between pre- and postexercise in CR and R with no between-group difference (P < .05). Conclusions: EIAH was aggravated in higher performers during simulated cycle-run segments, related to longer experience and heavier training regimens. Possibly, relative hypoventilation caused this aggravated EIAH in INT, although pulmonary diffusion limitation was observed in both groups. Beyond EIAH severity, the magnitude of SpO2 variations during the cycle-run transition may affect triathlon running performance. [ABSTRACT FROM AUTHOR]

The author conveys his thoughts about the role of scientists in keep science running. Topics mentioned include numbers of publications, citations, and corresponding statistical indicators as vital indicators of success of scientists irrespective of their potential validity, the book "Ethics of the Physician," by Ishaq bin Ali Al Rahwi, and the inventions of carbon paper in 1890 and the copier in 1959.

The author reflects on the significant role of elite athletes and expert coaches with academic profiles in establishing sound sport science. He notices how deep sport-discipline knowledge improved the quality of publications at the "International Journal of Sports Physiology and Performance." He discusses study conception and article writing and the manuscript peer-review process. He urges academics in sports to keep their efforts in improving sport science in their fields.

The author discusses the importance of evidence-informed injury prevention and management for increasing positive match and competition in elite sports. He cites proposal for an acute chronic workload ratio as a promising predictor of training-related injuries and the need for future studies that will define criteria for establishing appropriate training loads while affording an acceptable/minimal risk of injury for reaching peak elite sport performance.

Despite various contributing factors, session rating of perceived exertion has the potential to affect a large proportion of the global sporting and clinical communities since it is an inexpensive and simple tool that is highly practical and accurately measures an athlete’s outcome of training or competition. Its simplicity can help optimize performance and reduce negative outcomes of hard training in elite athletes. [ABSTRACT FROM AUTHOR]