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Ischemic preconditioning (IPC), which involves episodes of blood flow restriction followed by reperfusion, has uncertain effects on athletes. Additionally, employing sports-specific tests that are highly familiar to athletes can enhance methodological rigor in determining IPC's effects on taekwondo performance. This study aimed to investigate IPC's influence on taekwondo athletes' performance through two studies. To induce occlusion in both studies, the cuff was inflated to an individualized occlusion pressure established for each athlete's lower limb, with four cycles of occlusion lasting five minutes each, alternated with five-minute reperfusion intervals. Both traditional frequentist statistics and Bayesian analysis were employed. In the first study, eleven high-level athletes were subjected to either IPC or a placebo (SHAM) procedure on both legs, followed by performing countermovement jumps (CMJs) and a specific taekwondo endurance test. However, no significant differences were observed in taekwondo endurance performance or CMJ between the IPC and SHAM conditions. The second study involved fourteen elite athletes who underwent the same IPC or SHAM conditions, performing CMJ and three bouts of the Multiple Frequency Speed of Kick test (FSKTmult) in three blocks, each separated by approximately thirty minutes. Again, the results indicated no significant differences in FSKTmult measures or CMJ performance between the two conditions. In conclusion, IPC did not significantly affect neuromuscular (in both studies), endurance (in the first study), or anaerobic (in the second study) performance in these taekwondo athletes.

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Introduction: The application of muscle force is a determinant of football success as it is inherent to the motor control and sport. The aims of this study are: (1) to describe force variables Isometric Maximal Force (IMF), Concentric Peak Force (CPPF), and Dynamic Strength Index (DSI) in football goalkeepers from different age groups; (2) to compare these variables' behavior between those groups. Methods: The sample was formed by 19 youth players (15.97 ± 1.55 years old) from a first-division Brazilian football team. The CPPF and IMF variables were obtained through the Countermovement jump and isometric squat tests, respectively. For data collection, a force plate (Cefise, Brazil) was used with an acquisition frequency of 600 Hz and mono-axial. The DSI was calculated using the ratio between CPPF and IMF. For data analysis, the sample was separated into clusters by age. After the grouping, a descriptive analysis of the data and a comparison between the groups with p < 0.05. Results: The sample was grouped into three groups (GA, GB, and GC) and one of the individuals did not enter the group, totaling 18 individuals in the analyzed sample. The comparison between the ages of the groups showed a significant difference and small and moderate effect size (ES), validating the cluster strategy. The CPPF and IMF variables showed increased values according to chronological age. CPPF showed a significant difference between GA-GB, (ES = very large) GA-GC (ES = very large), and GB-GC (ES = moderate). The IMF variable had significant differences between GA-GB (ES = moderate) and GA-GC (ES = very large). However, DSI showed significant differences only between GA GB (ES = small) and GB-GC (ES = very large). Conclusions: The CPPF and IMF variables had constant increases and distinct values with an increase according to age, and this did not occur for DSI. The difference between CPPF and IMF compared to DSI bring to light the variability in dynamics and proportionality between muscular force in the concentric phase and maximal force in the isometric regime during the developmental process over chronological age in soccer goalkeepers.

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ABSTRACT The aim of this study was to investigate the effects of acute caffeine ingestion (5 mg.kg-1) on jump, isometric strength and repeated sprint performance in amateur American football athletes. Twelve players (24.6 ± 3.66 years and 115.18 ± 24.35 kg of body weight) ingested a dose of caffeine (5 mg.kg−1) or placebo 60 min prior to a testing session consisting of: 1) countermovement jump (CMJ); 2) isometric mid-tight pull (IMTP); and 3) 3-line drills (200-yd shuttle runs with a 2-minute rest between sprints). Two testing sessions were performed using a double-blind, counterbalanced, crossover design during a pre-season training camp. Results indicated: Caffeine ingestion improved CMJ performance (p = 0.035), but no differences were observed on IMTP strength (p = 0.22) and line drill performance (total time: p = 0.65, and fatigue (%): p = 0.75) when compared to placebo condition. Conclusion: Acute caffeine ingestion improved jump performance, but not isometric strength and repeated sprint with change-of-direction performance in amateur American Football athletes.

RESUMO O objetivo deste estudo foi investigar os efeitos da ingestão aguda de cafeína (5 mg.kg-1) no salto, força isométrica e desempenho de sprints repetidos em atletas amadores de futebol americano. Doze jogadores (24,6 6 ± 3.66 anos e 115,18 ± 24.35 kg de peso corporal) ingeriram uma dose de cafeína (5 mg.kg−1) ou placebo 60 minutos antes de uma sessão de testes que consistia em: 1) Salto contramovimento (CMJ); 2) Meio-agachamento isométrico (IMTP); 3) Corrida de agilidade em L (3-line drill = corrida de agilidade de 200 jardas com 2 minutos de repouso entre os sprints). Duas sessões de teste foram realizadas usando um delineamento cruzado duplo-cego durante o período de pré-temporada de treinamento. Resultados indicaram: A ingestão de cafeína melhorou o desempenho do CMJ (p = 0,035), mas não foram observadas diferenças na força no IMTP (p = 0,22) e no desempenho do exercício de agilidade em L (tempo total: p = 0,65 e fadiga (%): p = 0,75) quando em comparação com a condição placebo. Conclusão: A ingestão aguda de cafeína melhorou o desempenho no salto, mas não na força isométrica e no desempenho de sprints repetidos com mudança de direção em atletas amadores de futebol Americano.

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BACKGROUND: The prevalence of overweight/obesity has been increasing globally and in people with Intellectual Disabilities (IDs), this problem is exacerbated even more, which added to a low physical condition that contributes to the deterioration of functionality and increases the risk of developing chronic diseases in the course of life. Therefore, the aim of this study was to establish cut-off points for levels of isometric handgrip and low limb explosive strength in children, adolescents and adults, which identify overweight/obesity in people with IDs and their respective associations. METHODS: The sample was made up of 131 individuals with IDs, belonging to four special and community educational centres in the city of Santiago, Chile. Body mass index (BMI) and waist-to-height ratio (WHR) were used as indicators of overweight/obesity. Handgrip strength was used as a measure of isometric strength, and countermovement jump was used as a measure of low limb explosive strength. For the comparison of variables by age group, the analysis of Ancova, Kruskal-Wallis and chi-square tests were used. The total area under the receiver operating characteristic curve of isometric handgrip and low limb explosive strength was identified as an indicator of overweight/obesity according to age groups. A logistic regression model was used to quantify the effect that strength categories below the cut-off point have on the risk of overweight and obesity. RESULTS: Significant differences were observed between the age groups for body weight, height, BMI and WHR, as well as in the levels of absolute handgrip strength and vertical jump with countermovement (P ≤ 0.05). Children showed the lowest cut-off points for absolute and relative strength. The adolescent group showed the highest cut-off points for relative strength and countermovement jump and adults showed the highest value for absolute strength as indicators of overweight/obesity. Different associations between cut-off points with BMI and WHR were found. CONCLUSIONS: Adolescents showed the highest cut-off point for relative strength and countermovement jump, and adults showed the highest value for absolute strength, according to overweight/obesity indicators (BMI and WHR). It is suggested to adjust resistance training programmes according to age categories for the prevention of overweight/obesity in people with IDs.

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Studies on postactivation performance enhancement (PAPE) have used different exercises as a conditioning activity to investigate potentiation, but exclusively in upper limbs (UL) or lower (LL) limbs, or contralateral potentiation. A single exercise capable of inducing PAPE in both UL and LL is currently unknown. The present study explored the effect of the clean and jerk (C&J) as a conditioning activity for simultaneously producing PAPE interlimbs at the fourth, seventh, and 12th minutes postintervention. Twelve male weightlifters with 1-repetition maximum (1RM) in the C&J equivalent to ≥1.15 × body mass were randomly submitted to 2 experimental conditions (C&J and control [CON]). The C&J condition consisted of general warm-up (running on a treadmill and self-selected preparatory exercises) and 4 sets of 3 repetitions of C&J with 2 minutes between them (30%1RM, 50%1RM, 65%1RM, and 80%1RM) followed by a countermovement jump and a bench-press throw on a Smith machine after 4, 7, and 12 minutes, to measure the magnitude of PAPE in UL and LL. No previous exercise preceded countermovement-jump and bench-press-throw tests in the CON besides general warm-up. The main finding was that, regardless of time, the C&J resulted in greater height on countermovement jump and Smith machine bench-press throw when compared with the CON, presenting a similar effect size between UL and LL (34.6 [3.9] vs 33.4 [4.1] cm [+3.66%]; P = .038; effect size = 0.30 and 30.3 [4.7] vs 29.0 [5.1] cm [+4.44%]; P = .039; effect size = 0.26), respectively. Thus, C&J can be useful to produce PAPE simultaneously among members.

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Introduction: To better understand the post-activation performance enhancement (PAPE) effect promoted by a plyometric conditioning activity (CA), the aim of this study was to investigate the temporal response of PAPE after a plyometric CA. Methods: Fourteen healthy and active adults visited the laboratory 3 times, with an interval of 7 days between each visit. On the first day they were familiarized with the countermovement jump (CMJ) test and plyometric CA. In the second and third visits, participants performed either plyometric CA or control (remaining seated) in a crossover design. The CMJ test was performed pre and 1-, 3-, 6-, and 9-min post the plyometric CA or control. The comparisons were performed using the repeated measure two-factor ANOVA and Bonferroni adjustment (significance level adopted P ≤ 0.05). Results: Time (P < 0.01), condition (P < 0.01), and interaction (P < 0.01) effects were reported for CMJ comparisons. For the control condition, CMJ increased at 3 min compared to pre (P = 0.03) and at 3 min compared to 1 min (P = 0.03). For the plyometric CA, CMJ increased at 1- (P < 0.01), 3- (P < 0.01), and 6-min (P = 0.02) compared to pre. For condition comparisons, CMJ was different at 1- (P < 0.01), 3- (P < 0.01), 6- (P < 0.01), and 9-min (P = 0.02). The Effect size of the comparisons of all moments compared to pre was null (d < 0.20) for control and small (d < 0.50) for plyometric CA. Discussion: It is possible to conclude that the plyometric CA promoted a PAPE effect for up to 9-min. Strength and conditioning coaches and practitioners may consider multiple sets of plyometric CA to produce immediate enhancement of power in the lower limbs.

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The purpose of this study was to identify changes in neuromuscular performance variables evaluated through the countermovement jump test before and after (0 hours, after session and 24h post) of a simulated futsal protocol in young university female athletes. Fourteen eumenorrheic, healthy and experienced female futsal players were randomly assigned to an intervention group n = 7) or a control group (n = 7). Both groups performed three countermovement jumps before and after the protocol using an inertial system device. The intervention group completed a short-term functional agility and fatigue protocol that simulated the characteristics of futsal, while the control group did not perform any exercise. The results showed a reduction in peak flight time (p = 0.049; d = 0.586), peak concentric work (p = 0.03; d = 1.819) and peak maximum force (p = 0.02; d = 0.782) comparing experimental and control group. No changes in other variables examined were noted between conditions (p > 0.05). These findings indicate that the changes in neuromuscular performance variables, evaluated through a simulated protocol, are established as determinants in the definition of peripheral fatigue in futsal practitioners until 24 h after a demanding intervention.

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We aimed to evaluate the effect of 4 weeks of plyometric training (PT), performed in the pre-competitive period, on the vertical jump performance of professional volleyball athletes. We recruited 17 professional female volleyball players (age: 19 ± 3 years; weight: 67.2 ± 5.50 kg; height: 1.81 ± 0.22 m; body fat: 14.4 ± 2.12%; squat 1RM test: 75.5 ± 7.82 kg; training time experience: 6.2 ± 3.4 years) to participate in four weeks of training and assessments. They were divided into an experimental group (EG = 9) and a control group (CG = 8). Both groups were submitted to friendly matches, technical, tactical and resistance training (4 weeks/˜9 sessions per week), and internal load monitoring was carried out. The EG performed PT twice a week. At the beginning and end of the four weeks, jump tests were performed. The main findings are: 1) PT when incorporated into the pre-competitive period can induce greater improvements in jumping performance (EG = 28.93 ± 3.24 cm to 31.67 ± 3.39 cm; CG = 27.91 ± 4.64 cm to 28.97 ± 4.58 cm; when comparing the percentage delta, we found a difference between groups with ES of 1.04 and P = 0.02); 2) this result is observed when the training load is similar between groups and increases over the weeks, respecting the linear progression principle. Therefore, including plyometric training in the preparatory period for volleyball, with low monotony and training strain increment, is an effective strategy for further CMJ performance improvement.

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The aim of this study was to determine the relationships between vertical jumps (VJ) and various on-ice skating performances of junior ice hockey players (n = 19). The three modes of VJ or off-ice measures were countermovement jump with arm swing (CMJ), squat jump (SJ) and depth drop jump (DDJ). The on-ice skating performance was measured by the skating multistage aerobic test (SMAT), forward and backward acceleration test, top speed test, and repeated sprint ability (RSA) test. The relationships between the variables were quantified using Pearson's product-moment correlation. DDJ showed a significant positive correlation with forward average skating speed (FASS) (r = 0.62) and strong correlations with backward average skating speed (BASS) (r = 0.81), and maximum skating speed (MSS) (r = 0.71). SJ was found to be strongly correlated with BASS (r = 0.82) and MSS (r = 0.76), whereas the only on-ice performance that significantly correlated with CMJ was BASS (r = 0.68). All three modes of VJ were inversely and non-significantly correlated with performance decrement index and fatigue index, as determined by the RSA test. SMAT was not significantly correlated with either VJ or RSA. Correlations between all three modes of VJ tests were significant. Therefore, this study concludes that: (1) DDJ can be used as a predictor of all the ice skating speed tests, whereas SJ can predict BASS and MSS. CMJ, on the other hand, can predict the performance of only BASS. (2) RSA performance cannot be predicted from CMJ, SJ, or DDJ tests, and (3) neither any of the VJ nor RSA can predict skating endurance of junior ice hockey players.

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Background: We investigated the concurrent validity and test-retest reliability of the Jumpo 2 and MyJump 2 apps for estimating jump height, and the mean values of force, velocity, and power produced during countermovement (CMJ) and squat jumps (SJ). Methods: Physically active university aged men (n = 10, 20 ± 3 years, 176 ± 6 cm, 68 ± 9 kg) jumped on a force plate (i.e., criterion) while being recorded by a smartphone slow-motion camera. The videos were analyzed using Jumpo 2 and MyJump 2 using a Samsung Galaxy S7 powered by the Android system. Validity and reliability were determined by regression analysis, typical error of estimates and measurements, and intraclass correlation coefficients. Results: Both apps provided a reliable estimate of jump height and the mean values of force, velocity, and power. Furthermore, estimates of jump height for CMJ and SJ and the mean force of the CMJ were valid. However, the apps presented impractical or poor validity correlations for velocity and power. Compared with criterion, the apps underestimated the velocity of the CMJ. Conclusions: Therefore, Jumpo 2 and MyJump 2 both provide a valid measure of jump height, but the remaining variables provided by these apps must be viewed with caution since the validity of force depends on jump type, while velocity (and as consequence power) could not be well estimated from the apps.

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This study aimed to analyse unilateral countermovement jumps (CMJ) performance and muscle soreness in lower limbs, as well as to compare lower limb asymmetry over 48h after a stretch-shortening cycle (SSC) fatigue protocol. Fourteen judo athletes performed unilateral CMJ on each leg before, and after the 5th and 10th sets over 24h and 48h of an SSC-fatigue protocol. The SSC protocol reduced CMJ performance after the 5th set and 10th sets, especially in the weaker limb (p < 0.05), but returned to the baseline values after 24h. Asymmetry increased for peak force, peak power, and mean power after the 5th set compared to the baseline (p < 0.05) and remained higher for peak force after the 10th set (p = 0.019), returning to the baseline values after 24h (p < 0.05). Soreness increased for the lower body at post, 24h, and 48h compared to the baseline (p < 0.05). In conclusion, a fatiguing SSC protocol can result in increased bilateral asymmetries in judo athletes, but after 24h and 48h of the protocol the bilateral asymmetry returned to the baseline values, with only muscle soreness still elevated.

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The objective of this study was to evaluate the effects of a training session with and without an intervention of postactivation performance enhancement (PAPE) on countermovement jump (CMJ) height, perceived recovery status (PRS), and ratings of perceived exertion (RPEs), followed by a specific volleyball training session. The sample consisted of sixteen professional male volleyball players, with an average age of 26.8±6.1 years and average height of 195.9±6.7 cm, randomly divided into a group with PAPE intervention (GPAPE) (n=8), and a control group (CTRL) without PAPE intervention (n=8). The control group carried out the training session with plyometric exercises, and the GPAPE added conditioning protocols for PAPE to plyometric training, followed by a technical tactical volleyball session. At the end of the training session, there was an increase of 16.3% in the height of the CMJ in the GPAPE, while the CTRL showed a decrease of 5% in the height of the CMJ. PRS and RPE variables did not differ between the groups. It was concluded that PAPE had a positive effect on the height of the vertical jump after plyometric training, which was maintained until the end of the technical and tactical volleyball session.

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This study examined the effect of caffeine supplementation (CAFF) in a Wingate test (WT), and the behaviour of blood lactate concentrations (BLa) and neuromuscular fatigue (NMF), measured as reduced countermovement jump (CMJ) performance, in response to the WT. In a double-blind crossover study, 16 participants attended the laboratory twice, separated by a 72-hour window. In the sessions, participants first ingested 6 mg·kg-1 of either CAFF or placebo (PLAC), and then performed a WT. BLa was measured before (L-pre), and 0.5 min (L-post-0.5) and 3.5 min (L-post-3.5) after conducting the WT. The CMJ test was conducted before (CMJ pre), after (CMJ post), and 3 min after completing (CMJ post-3) the WT. The results indicated that CAFF enhanced peak power (Wpeak: + 3.22%; p = 0.040), time taken to reach Wpeak (T_Wpeak: -18.76%; p = 0.001) and mean power (Wmean: + 2.7%; p = 0.020). A higher BLa was recorded for CAFF at L-post-0.5 (+ 13.29%; p = 0.009) and L-post-3.5 (+ 10.51%; p = 0.044) compared to PLAC. CAFF improved peak power (PP; + 3.44%; p = 0.003) and mean power (MP; + 4.78%; p = 0.006) at CMJ pre, compared to PLAC, whereas PP and MP were significantly diminished at CMJ post and CMJ post-3 compared to pre (p < 0.001 for all comparisons) under both the CAFF and PLAC conditions. PP and MP were increased at post-3 compared to post (p < 0.001 for all comparisons) for both conditions. In conclusion, CAFF increased WT performance and BLa without affecting NMF measured by CMJ. Thus, CAFF may allow athletes to train with higher workloads and enhance the supercompensation effects after an adequate recovery period.

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BACKGROUND: This study aimed to analyze the extent of fatigue responses after female soccer matches and the ensuing recovery time course of performance, physiological, and perceptual responses. METHODS: Three databases (PubMed, Web of Science, and SPORTDiscus) were searched in October 2020 and updated in November 2021. Studies were included when participants were female soccer players, regardless of their ability level. Further, the intervention was an official soccer match with performance, physiological, or perceptual parameters collected pre- and post-match (immediately, 12 h, 24 h, 48 h, or 72 h-post). RESULTS: A total of 26 studies (n = 465 players) were included for meta-analysis. Most performance parameters showed some immediate post-match reduction (effect size [ES] = - 0.72 to - 1.80), apart from countermovement jump (CMJ; ES = - 0.04). Reduced CMJ performance occurred at 12 h (ES = - 0.38) and 24 h (ES = - 0.42) and sprint at 48 h post-match (ES = - 0.75). Inflammatory and immunological parameters responded acutely with moderate-to-large increases (ES = 0.58-2.75) immediately post-match. Creatine kinase and lactate dehydrogenase alterations persisted at 72 h post-match (ES = 3.79 and 7.46, respectively). Small-to-moderate effects were observed for increased cortisol (ES = 0.75) and reduced testosterone/cortisol ratio (ES = -0.47) immediately post-match, while negligible to small effects existed for testosterone (ES = 0.14) and estradiol (ES = 0.34). Large effects were observed for perceptual variables, with increased fatigue (ES = 1.79) and reduced vigor (ES = - 0.97) at 12 h post-match, while muscle soreness was increased immediately post (ES = 1.63) and at 24 h post-match (ES = 1.00). CONCLUSIONS: Acute fatigue exists following female soccer matches, and the performance, physiological, and perceptual parameters showed distinctive recovery timelines. Importantly, physical performance was recovered at 72 h post-match, whereas muscle damage markers were still increased at this time point. These timelines should be considered when planning training and match schedules. However, some caution should be advised given the small number of studies available on this population. REGISTRATION: The protocol for this systematic review was pre-registered on the International Prospective Register of Systematic Reviews (PROSPERO, Registration Number: CRD42021237857).

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SUMMARY: The purpose of this study was to assess the correlation between the body composition, multiple repeated sprint ability (MRSAB) test, and vertical jump performance. Fifteen voluntary elite Turkish badminton players participated in the study. The MRSAB test consisted of 2 repetitions of 4 movements (4x3m) separated by 30 seconds of passive recovery. The best time (BT), meantime (MT), total time (TT), and fatigue index (FI) were measured. Body composition was evaluated through dual-energy X-ray absorptiometry (DEXA). Squat jump (SJ) test for explosive power and countermovement jump (CMJ) test for elastic power were used. The main findings were that there was a significant correlation between MRSAB MT and TT with lean body mass, lean arm mass, and trunk lean mass (kg) of male badminton players. However, no significant correlation was observed among MRSAB MT, BT, and TT with another total/regional body composition of female badminton players (p>0.05). Moreover, the results of male badminton players showed that there was a significant negative correlation between FI and percentage ofbody fat (%BF), percentage of leg fat (%LF), percentage of trunk fat (%TF), and trunk mass. In addition, there was a significant negative correlation between FI with %BF, body fat mass kg, percentage of arm fat (%AF), arm fat mass, and %LF of female badminton players. It was also found in the study that there was a significant correlation between SJ and %LF; CMJ and %BF, body fat mass kg, %AF, %LF and leg fat mass kg. However, no significant correlation was observed among CMJ and SJ with other total/regional body compositions of male badminton players (p>0,05). Finally, changes in body composition are important issues for the physical performance level of badminton players as regional excess body fat may cause deterioration, especially in repeated-sprint ability and jumping performance.

RESUMEN: El propósito de este estudio fue evaluar la correlación entre la composición corporal, la prueba de capacidad de sprint repetido (MRSAB) y el rendimiento del salto vertical. Quince jugadores voluntarios de bádminton turcos de élite participaron en el estudio. El test MRSAB consistió en 2 repeticiones de 4 movimientos (4x3m) separados por 30 segundos de recuperación pasiva. Se midieron el mejor tiempo (BT), el tiempo medio (MT), el tiempo total (TT) y el índice de fatiga (FI). La composición corporal se evaluó mediante absorciometría de rayos X de energía dual (DEXA). Se utilizó la prueba de salto desde la sentadilla (SJ) para la potencia explosiva y la prueba de salto con contramovimiento (CMJ) para la potencia elástica. Los principales hallazgos fueron una correlación significativa entre MRSAB MT y TT con la masa corporal magra, la masa magra del brazo y la masa magra del tronco (kg) de los jugadores de bádminton hombres. Sin embargo, no se observó una correlación significativa entre MRSAB MT, BT y TT con otra composición corporal total/regional de jugadoras de bádminton (p>0,05). Además, los resultados de los jugadores hombres de bádminton mostraron que había una correlación negativa significativa entre FI y el porcentaje de grasa corporal (% BF), porcentaje de grasa en las piernas (% LF), porcentaje de grasa en el tronco (% TF) y masa del tronco. Además, hubo una correlación negativa significativa entre FI con %GC, masa de grasa corporal en kg, porcentaje de grasa en el brazo (%AF), masa de grasa en el brazo y %LF de las jugadoras de bádminton. También se descubrió en el estudio que había una correlación significativa entre SJ y %LF; CMJ y %BF, masa grasa corporal kg, %AF, %LF y masa grasa de piernas kg. Sin embargo, no se observó una correlación significativa entre CMJ y SJ con otras composiciones corporales totales/regionales de los hombres jugadores de bádminton (p>0,05). Finalmente, los cambios en la composición corporal son cuestiones importantes para el nivel de rendimiento físico de los jugadores de bádminton, debido a que el exceso de grasa corporal regional, puede causar un deterioro, especialmente en la capacidad de repetir sprints y en el rendimiento de los saltos.

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The vertical jump test is one of the simplest and most prevalent physical tests used in practice and research. This study investigated the validity and reliability of a new mobile application (Jumpo) for measuring jump performance on Android devices. University-aged students (n = 10; 20 ± 3 years; 176 ± 6 cm; 68 ± 9 kg) reported to the laboratory on three occasions (2-7 days apart): to be familiarized with the jump performance measurements and then for test-retest reliability assessments. Participants performed countermovement jumps (CMJ), squat jumps (SJ), and right and left single-legged jumps in random order on a force platform while being recorded by a smartphone's slow-motion camera. Flight time was selected as the criterion variable. Strong positive correlations between the Jumpo and force platform were observed for each jump type tested (r ≥ 0.93), although the flight times obtained with the Jumpo App were systematically shorter than those provided by the force platform by 3-6% (p < 0.001). The Jumpo App demonstrated a high test-retest reliability (ICC ≥ 0.94, CV ≤ 3.7%) with no differences between the coefficients of variation obtained from the Jumpo App and force platform (p ≥ 0.25). With respect to jump type, data from double-legged jumps (CMJ and SJ) were more accurately measured than data from single-legged jumps. The Jumpo App provides a valid and reliable measurement of jump performance, but the following equation should be used to calibrate its flight time results, allowing comparisons to be made to force platform data: Force platformflight time = 0.948 × Jumpoflight time + 41.515. Future studies should cross-validate the calibration equation in a different sample of individuals.

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To investigate and compare the reliability of reactive strength index-modified (RSImod) and its associated variables (jump height [JH] and [time to take-off]) 20 combat fighters and 18 physically active men participated in this study. They visited the laboratory three times; firstly, for jump familiarization and two sessions for test-retest (2-7 days apart). For both groups, the between-day changes in performance were trivial to small (≤ 1.1%). The coefficient of variation (CV) comparisons (i.e. CV ratio) demonstrated that combat athletes had a lower test-retest variation for RSImod (0.87) and JH (0.80) than non-athletes. Combat athletes demonstrated a greater JH than physically active men (0.43 vs 0.37; p = 0.03, g = 0.73), but small and non-significant differences were observed for RSImod (0.60 vs 0.55; p = 0.24, g = 0.38) and TTT (0.70 vs 0.72; p = 0.32, g = 0.33). RSImod was more positively correlated with JH (r = 0.75-0.87; p < 0.001) than negatively correlated with TTT (r = 0.45-0.54; p < 0.001). This study suggests that RSImod is a reliable variable obtained during CMJ testing in combat athletes and physically active men, with scores being slightly better for combat athletes. In terms of performance, combat athletes jumped higher than physically active men, but no differences in RSImod or TTT were observed. Lastly, RSImod was more strongly related to JH than TTT, and this was more evident in athletes than nonathletes. This indicates that the combat athletes were able to better utilize their (equal) time spent jumping (higher), possibly via greater utilization of the stretch shortening cycle, faster or more optimal motor unit recruitment, or an array of other factors.

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The COVID-19 pandemic forced elite football leagues into extended breaks followed by prompt resumption of competition. Inadequate periods of on-pitch football-specific training may underlie the increased injury incidence reported following restart in a non-peer reviewed report. Detraining effects from isolated training are expected, but existing models do not completely describe the unprecedented conditions imposed by COVID-19.Providing insight into specific neuromuscular qualities affected by extended absence of football-specific training, we share countermovement jump performance and kinetic data from an elite team's assessments pre and post 15 weeks of isolated training, and to contextualise these trends, off-season changes with no training.The isolated circuit resistance and aerobic interval training maintained jump height and Reactive Strength Indexmodified, but there were moderate magnitude (p = 0.01-0.04) changes in eccentric 'yielding' and landing 'loading' phase variables. These changes suggest a compromised initiation of countermovement deceleration, impact attenuation and altered coordination/motor control strategies or muscle-tendon properties. This analysis may have revealed kinetic markers specifically stimulated by football-specific training/competition, relevant to post-quarantine monitoring. Lower landing forces may reduce overuse injury risk, while yielding phase alterations suggest a negative effect on reactive performance, therefore the overall effect on vulnerability to injury is unclear.

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Abstract The present study investigated the effect of eccentric overload on professional basketball players. Participants were 8 players aged 18-25 years who play in a Leb Oro League team. There was an 8 week training cycle with 1 weekly session of half squats. The control group performed training following a traditional methodology -using free weights- whereas the experimental group used inertial technology, that is, the ProSquat machine from Proinertial®. Both vertical jump and 30-meter sprint were assessed before and after intervention. The following conclusions were reached: a) strength training with vertical vector improves the 30-meter sprint test and also the vertical jump; b) training program that affects the eccentric overload of the movement results in more improvements than traditional training with the same duration; c) training in the vertical vector also has an impact on the way force is manifested in the horizontal vector, showing improvements in the 30-meter sprint.

Resumo O presente estudo investigou o efeito da sobrecarga excêntrica em jogadores profissionais de basquetebol. Os participantes foram 8 jogadores de uma equipe da Leb Gold League entre 18 e 25 anos. Um ciclo de treinamento de 8 semanas foi realizado com 1 sessão semanal no exercício de meio agachamento. O grupo controle realizou o treinamento com metodologia tradicional, com pesos livres, e o grupo experimental, por meio de tecnologia inercial, com a máquina ProSquat, Proinertial®. O salto vertical e o sprint de 30 metros foram avaliados antes e após a intervenção. As seguintes conclusões foram obtidas: a) o treinamento de força com um componente no vetor vertical mostra melhorias no teste de 30 metros e no salto vertical; b) um programa que afeta a sobrecarga de movimento excêntrico apresenta resultados com melhores desempenhos do que o treinamento tradicional; c) o treinamento no vetor vertical também afeta uma expressão da força no vetor horizontal, mostrando melhorias no sprint de 30 metros.

RESUMO

Whole-body cryotherapy (WBC) has been used as a recovery strategy following different sports activities. Thus, the aim of the study reported here was to examine the effect of WBC on vertical jump recovery following a high-intensity exercise (HIE) bout. Twelve trained men (mean ± standard deviation age = 23.9±5.9 years) were randomly exposed to two different conditions separated by 7 days: 1) WBC (3 minutes of WBC at -110°C immediately after the HIE) and 2) control (CON; no WBC after the HIE). The HIE consisted of six sets of ten repetitions of knee extensions at 60° · s(-1) concentric and 180° · s(-1) eccentric on an isokinetic dynamometer. The vertical jump test was used to evaluate the influence of HIE on lower extremity muscular performance. The vertical jump was performed on a force platform before HIE (T1) and 30 minutes after (T2) the WBC and CON conditions. As a result of HIE, jump height, muscle power, and maximal velocity (Vmax) had significant decreases between T1 and T2, however no significance was found between the WBC and CON conditions. The results indicate that one session of WBC had no effect on vertical jump following an HIE compared with a CON condition. WBC may not improve muscle-function (dependent on stretch-shortening cycle) recovery in very short periods (ie, 30 minutes) following HIE.