Effects of exercise on life satisfaction of people diagnosed with cancer: a systematic review and meta-analysis.

PURPOSE: A cancer diagnosis is commonly associated with a decline in patient's life satisfaction and more pessimistic expectations about the future. The identification of strategies to improve life satisfaction in patients with cancer is of great interest to health practitioners since it may be associated with a better prognosis of cancer and higher survival rates. Previous meta-analyses and reviews concluded that exercise could significantly improve health-related quality of life in this population, but the effects of exercise on life satisfaction are still not well-known. This review aims to analyse the effects of exercise programs on life satisfaction in people with cancer and individuals who have overcome cancer. METHODS: The present systematic review and meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. A thorough search of databases including Web of Science and PubMed/MEDLINE was carried out. Six studies (535 participants) in which the effect of an exercise program was compared to a non-exercise program control condition in patients with cancer were considered eligible. A subsequent meta-analysis was performed using the random effects model to calculate the standardized mean differences (SMD) and 95% confidence intervals (CI). RESULTS: Exercise intervention improved satisfaction with life compared with a control condition (SMD = 1.28; p = 0.02 with a 95% CI of 0.22 to 2.34). CONCLUSION: Exercise could be considered an effective tool to improve life satisfaction in patients with cancer. Hence, professionals might consider the possibility of integrating physical exercise into strategies aimed at enhancing the low life satisfaction often experienced by patients. PROSPERO: CRD42023438146.

Influence of a football match on landing biomechanics and jump performance in female football players.

This study aimed to assess the acute effect of a competitive football match on jump performance and kinematic parameters during jump landing in semiprofessional female football players. Twenty-two semiprofessional players (20 ± 3 years) underwent a drop jump task for a posterior video analysis of the landing phase. These measurements were obtained at (1) baseline, (2) after, and (3) 48 h after a competitive football match. A one-way ANOVA with repeated measures was employed to detect differences over the time. There was a main effect of time for maximal knee flexion angle during drop landing (p = 0.001). In comparison with baseline, maximal knee flexion angle was reduced immediately post-match and was still reduced 48 h after the match (63.4 ± 8.6 vs 57.0 ± 11.7 vs 48.9 ± 19.1, p ≤ 0.038). There was also a main effect of time for drop jump height (p < 0.001). Drop jump height was reduced immediately post-match and remained low 48 h after the match in comparison with baseline (27.3 ± 3.6 vs 24.5 ± 2.8 ~ 25.5 ± 3.0 cm, p ≤ 0.002). There was a main effect of time on hip flexion angle during landing (p = 0.001), but the pairwise comparison revealed that this variable was not affected immediately post-match but was lower 48 h after the match than at baseline (50.1 ± 10.1 ~ 50.8 ± 13.2 vs 38.1 ± 17.8 °, p ≤ 0.005). A competitive football match worsened jump performance and several landing biomechanical parameters in female football players, which were still decreased in comparison with baseline even 48 h after the match.

Influence of the time of day in the effect of caffeine on maximal fat oxidation during exercise in women: a randomized, crossover, double-blind, and placebo-controlled study.

PURPOSE: Caffeine is a stimulant with well-recognized performance and metabolic benefits, however, there is a lack of studies investigating the time-of-day influence in the properties of caffeine to enhance fat oxidation in women. Thus, the aim of the present study was to evaluate the influence of the time of the day on the effect of caffeine on the maximal rate of fat oxidation during aerobic exercise in trained women. METHODS: Fourteen female athletes (25.5 ± 7.1 years) took part in a randomized, crossover, double-blind study. All participants undertook four different experimental trials combining the ingestion of 3 mg/kg caffeine and a placebo either in the morning (8.00-10.00 h) and in the evening (17.00-19.00 h) realizing an incremental test on a cycle ergometer with 3 min stages at workloads from 30 to 70% of maximal oxygen uptake (VO2max). Substrate oxidation rates were measured by indirect calorimetry. In each trial, the maximum rate of fat oxidation (MFO) and the intensity that elicited MFO (Fatmax) were measured. RESULTS: In comparison to placebo, MFO was significantly higher with caffeine both in the morning (0.24 ± 0.13 vs 0.30 ± 0.14 g/min; p < 0.001; ES = 0.79) and in the evening (0.21 ± 0.08 vs 0.28 ± 0.10 g/min; p = 0.002; ES = 0.72). No time-of-day effect on the capacity of caffeine to increase MFO was found (all p = 0.336) CONCLUSION: The intake of 3 mg/kg of caffeine increased the use of fat as a fuel during exercise independently of the time-of-day in trained women. TRIAL REGISTRATION: The study was registered in ClinicalTrials.gov with the following ID: NCT05880186 by 15 May 2023.

Muscle hypertrophy induced by N-3 PUFA supplementation in absence of exercise: a systematic review of randomized controlled trials.

The use of omega-3 polyunsaturated fatty acids (n-3 PUFA) has been studied in physically active population, however, there is a lack of information about the effects of n-3 PUFA supplementation on people with a sedentary behavior or who are undergoing a period of limb immobilization. This systematic review aims to examine the effect of n-3 PUFA on lean mass and muscle protein synthesis (MPS) in absence of physical training. The PubMed, Web of Science, MEDLINE, CINAHL and SPORTDiscus databases were searched following the PRISMA guidelines. Only randomized controlled trials, at least single blind, performed with sedentary humans were considered. Seven studies on a total of 192 individuals were included. Five of the six studies which measured changes in skeletal muscle volume and mass showed higher values with n-3 PUFA. Only two studies measured skeletal muscle protein expression. Both showed beneficial effects of supplementation in muscle protein fractional synthesis rate (FSR), while no effect of n-3 PUFA was observed for mechanistic target of rapamycin (mTOR) and kinase protein (Akt). In addition, ribosomal protein S6 kinase 1 (p70s6k) improved with n-3 PUFA only in one study. Finally, the two studies which measured the skeletal muscle gene expression observed no effect of supplementation.

Effects of acute caffeine intake on combat sports performance: A systematic review and meta-analysis.

The interest in the benefits of caffeine in combat sports has grown exponentially in the last few years, evidenced by the significant rise of post-competition urine caffeine concentration. We conduct a systematic review and meta-analysis on the effects of caffeine on different performance variables in combat sports athletes. In total, we included 25 studies. All studies included had blinded, and cross-over experimental designs, and we conducted a risk of bias analysis. For nonspecific outcomes, there was an ergogenic effect of caffeine on vertical jump height (SMD: 0.38; 95% CI: 0.04, 0.71) and reaction time (SMD: -0.98, 95% CI: -1.46,-0.50). For outcomes specific to combat sports, there was an increase in the number of throws with caffeine in the Special Judo Fitness Test (SMD: 0.62; 95% CI: 0.14, 1.09). Caffeine ingestion increased the number of offensive actions during combats (SMD: 0.40; 95% CI: 0.06, 0.74). Caffeine ingestion increased the duration of offensive actions during combat (SMD: 0.58; 95% CI: 0.21, 0.96). Finally, caffeine ingestion increased blood lactate concentration after bout 1 (SMD: 1.35) bout 2 (SMD: 1.43) and bout 3 (SMD: 1.98). Overall, athletes competing in combat sports may consider supplementing with caffeine for an acute increase in exercise performance.

Effect of caffeine intake on fat oxidation rate during exercise: is there a dose-response effect?

PURPOSE: The effect of caffeine to enhance fat utilisation as fuel for submaximal aerobic exercise is well established. However, it is unknown whether this effect is dose dependent. The aim of this study was to investigate the effect of 3 and 6 mg of caffeine per kg of body mass (mg/kg) on whole-body substrate oxidation during an incremental cycling exercise test. METHODS: In a double-blind, randomised, and counterbalanced experiment, 18 recreationally active males (maximal oxygen uptake [VO2max] = 56.7 ± 8.2 mL/kg/min) performed three experimental trials after ingesting either 3 mg/kg of caffeine, 6 mg/kg of caffeine or a placebo (cellulose). The trials consisted of an incremental exercise test on a cycle ergometer with 3-min stages at workloads from 30 to 80% of VO2max. Energy expenditure, fat oxidation rate, and carbohydrate oxidation rate were continuously measured by indirect calorimetry. RESULTS: During exercise, there was significant effect of substance (F = 7.969; P = 0.004) on fat oxidation rate. In comparison to the placebo, the rate of fat oxidation was higher with 3 mg/kg of caffeine at 30, 40, 50 and 70% of VO2max [all P < 0.050, effect sizes (ES) from 0.38 to 0.50] and with 6 mg/kg of caffeine at 30, 40, 50, 60 and 70% of VO2max (all P < 0.050, ES from 0.28 to 0.76). Both 3 mg/kg (0.40 ± 0.21 g/min, P = 0.021, ES = 0.57) and 6 mg/kg of caffeine (0.40 ± 0.17 g/min P = 0.001, ES = 0.60) increased the maximal rate of fat oxidation during exercise over the placebo (0.31 ± 0.15 g/min). None of the caffeine doses produced any significant effect on energy expenditure or heart rate during exercise, while both caffeine doses reduced perceived fatigue at 80% of VO2max (all P < 0.050, ES from 0.71 to 1.48). CONCLUSION: The effect of caffeine to enhance fat oxidation during submaximal aerobic exercise is of similar magnitude with 3 and 6 mg of caffeine per kg of body mass. Thus, a dose of 3 mg of caffeine per kg of body mass would be sufficient to enhance fat utilisation as fuel during submaximal exercise.

Effect of 3 and 6 mg/kg of caffeine on fat oxidation during exercise in healthy active females.

The aim of this study was to investigate the effect of 3 and 6 mg of caffeine per kg of body mass (mg/kg) on whole-body substrate oxidation during an incremental cycling exercise test in healthy active women. Using a double-blind placebo-controlled counterbalanced experimental design, 14 subjects performed three identical exercise trials after the ingestion of 3 or 6 mg/kg of caffeine or placebo. The exercise trials consisted of an incremental test on a cycle ergometer with 3-min stages at workloads from 30 to 70% of maximal oxygen uptake (VO2max). Substrate oxidation rates were measured by indirect calorimetry. During exercise, there was a significant effect of substance (F = 5.221; p = 0.016) on fat oxidation rate. In comparison to the placebo, 3 mg/kg of caffeine increased fat oxidation rates at 30 to 60% of VO2max (all p < 0.050) and 6 mg/kg at 30 to 50% of VO2max (all p < 0.050). There was also a significant effect of substance (F = 5.221; p = 0.016) on carbohydrate oxidation rate (F = 9.632; p < 0.001). In comparison to placebo, both caffeine doses decreased carbohydrate oxidation rates at 40 to 60% VO2max (all p < 0.050). The maximal rate of fat oxidation with placebo was 0.24 ± 0.03 g/min, which increased with 3 mg/kg to 0.29 ± 0.04 g/min (p = 0.032) and to 0.29 ± 0.03 with 6 mg/kg of caffeine (p = 0.042). Acute intake of caffeine improves the utilization of fat as a fuel during submaximal aerobic exercise in healthy active women with an effect of similar magnitude after the intake of 3 and 6 mg of caffeine per kg of body mass. Thus, the use of 3 mg/kg of caffeine would be more recommended than 6 mg/kg for women seeking increased fat utilization during submaximal exercise.

The Effect of Acute Caffeine Intake on Resistance Training Volume, Prooxidant-Antioxidant Balance and Muscle Damage Markers Following a Session of Full-Body Resistance Exercise in Resistance-Trained Men Habituated to Caffeine.

No previous study has analyzed the impact of caffeine intake on prooxidant-antioxidant balance and muscle damage following resistance exercise. The aim of this study was to determine the effect of 3 mg/kg of caffeine on the number of repetitions and the prooxidant-antioxidant balance and muscle damage after a session of full-body resistance exercise. Ten resistance-trained men habituated to caffeine participated in a randomized, crossover and double-blind experiment. Each participant performed two identical resistance training sessions after the intake of 3 mg/kg of caffeine or a placebo. Blood was collected before and 60 min after substance intake, just after exercise, 60 minutes after exercise, and 24 hours after testing to evaluate the activity of antioxidant enzymes (superoxide dismutase, glutathione peroxidase, catalase), non-enzymatic antioxidants (reduced glutathione, uric acid) levels of oxidative stress markers (plasma malondialdehyde) and muscle damage markers (creatine kinase, lactate dehydrogenase). There were no significant differences between placebo and caffeine conditions in the total number of repetitions (180 ± 15 vs 185 ± 14 repetitions, respectively; p = 0.276; Effect size [ES] = 0.34), the total time under tension (757 ± 71 vs 766 ± 56 s, respectively; p = 0.709; ES = 0.14) or the rating of perceived exertion (13.8 ± 2.7 vs 14.7 ± 2.7 a.u., respectively; p = 0.212; ES = 0.32). Reduced glutathione concentration obtained 1 hour after exercise was higher with caffeine than with placebo (p = 0.047), without significant difference between conditions for any other prooxidant-oxidant or muscle damage marker at any time point (p > 0.050 for all). The oral intake of 3 mg/kg of caffeine by resistance-trained men habituated to caffeine did not enhance the number of repetitions during a medium load full-body resistance training session to failure and had a minimal impact on the prooxidant-antioxidant balance and muscle damage. The study was registered prospectively at ClinicalTrials.gov with the following ID: NCT05230303.

Synergy of carbohydrate and caffeine ingestion on physical performance and metabolic responses to exercise: A systematic review with meta-analysis.

Carbohydrates (CHO) and caffeine (CAF) are two ergogenic aids commonly used among athletes to enhance performance. However, there is some controversy as to whether the concurrent intake of both supplements might result in an additive and synergistic improvement in exercise performance. The aim of this systematic review and meta-analysis was to determine the effect of adding CAF to a protocol of CHO ingestion, compared with the intake of each ergogenic aid alone and with placebo, on exercise performance and metabolic responses in healthy young physically active adults. This study was conducted according to PRISMA 2020 guidelines. The PubMed, Web of Science, Medline Complete, CINAHL, SPORTDiscus and CENTRAL databases were searched including randomized controlled trials (RCT) that were at least single blind. The risk of bias assessment was performed using the Cochrane Risk-of-Bias tool 2. Meta-analysis were performed on performance variables and rating of perceived exertion (RPE) using the random-effects model. Thirteen RCT with 128 participants (117 men and 11 women) were included in this study. The ingestion of CAF and CHO reduced sprint time during repeated sprint protocols in comparison with CHO isolated ingestion (SMD: -0.45; 95% CI: -0.85, -0.05) while there was a tendency for a reduction in the time employed during time trials (SMD: -0.36; 95% CI: -0.77, 0.05). The RPE tended to be lower with CAF and CHO compared with CHO isolated ingestion during steady-state exercise (SMD: -0.43; 95% CI: -0.91, 0.05) with no differences between conditions in performance trials (SMD: -0.05, 95% CI: -0.39, 0.29). Although most of the studies showed higher values of blood glucose when CHO was co-ingested with CAF compared with PLA, only two studies observed higher values with CHO and CAF co-ingestion with respect to the isolated intake of CHO. One study observed greater fat oxidation and lower glycogen use when CAF was added to CHO. In terms of cortisol levels, one study showed an increase in cortisol levels when CAF was co-ingested with CHO compared with PLA. In summary, concurrent CHO and CAF intake may produce an additive ergogenic effect respect of the isolated ingestion of CHO. This additive effect was present when CHO was provided by a 6-9% of CHO solution (maltodextrin/dextrin + fructose) and CAF is administered in a dose of 4-6.5 mg/kg.

Effect of caffeine on muscle oxygen saturation during short-term all-out exercise: a double-blind randomized crossover study.

PURPOSE: The ergogenic effect of oral caffeine administration on short-term all-out exercise performance is well established. However, the potential mechanisms associated with caffeine's ergogenicity in this type of exercise are poorly understood. The aim of this study was to investigate whether caffeine intake modifies muscle oxygen saturation during the 15-s Wingate Anaerobic Test. METHODS: Fifteen moderately trained individuals (body mass = 67.4 ± 12.3 kg; height 171.3 ± 6.9 cm; age 31 ± 6 years) took part in two identical experimental trials after the ingestion of (a) 3 mg/kg of caffeine or (b) 3 mg/kg of cellulose (placebo). After 60 min for substances absorption, participants performed a 15-s Wingate test on a cycle ergometer against a load representing 7.5% of participant's body mass. Muscle oxygen saturation was continuously measured during exercise with near-infrared spectroscopy and blood lactate concentration was measured 1 min after exercise. RESULTS: In comparison to the placebo, the oral administration of caffeine increased peak power by 2.9 ± 4.5% (from 9.65 ± 1.38 to. 9.92 ± 1.40 W/kg, P = 0.038; effect size (ES), 95% confidence intervals = 0.28, 0.05-0.51), mean power by 3.5 ± 6.2% (from 8.30 ± 1.08 to 8.57 ± 1.12 W/kg, P = 0.044; ES = 0.36, 0.01-0.71) and blood lactate concentration by 20.9 ± 24.7% (from 12.4 ± 2.6 to 14.8 ± 4.0 mmol/L, P = 0.005; ES = 0.59, 0.16-1.02). However, caffeine did not modify the curve of muscle oxygen desaturation during exercise (lowest value was 23.1 ± 14.1 and 23.4 ± 14.1%, P = 0.940). CONCLUSION: Caffeine's ergogenic effect during short-term all-out exercise seems to be associated with an increased glycolytic metabolism with no influence of enhanced muscle oxygen saturation.

Acute effects of two caffeine doses on bar velocity during the bench press exercise among women habituated to caffeine: a randomized, crossover, double-blind study involving control and placebo conditions.

PURPOSE: The main goal of this study was to evaluate the effectiveness of two different doses of caffeine (3 and 6 mg/kg) to enhance bar velocity during the bench press in women habituated to caffeine. METHODS: Twelve recreationally trained women (age: 23.3 ± 0.8 years, body mass: 60.7 ± 5.7 kg, bench press one-repetition maximum (1RM): 44.3 ± 7.8 kg, daily caffeine ingestion: 5.7 ± 2.0 mg/kg/day) participated in a randomized double-blind experimental design. Each participant performed four different experimental sessions: after no supplementation (control, CON), after ingesting 3 and 6 mg/kg of caffeine (CAF-3 and CAF-6, respectively), or after ingesting a placebo (PLAC). In each experimental session, the participants performed 3 sets of 3 repetitions of the bench press exercise at 50% 1RM. RESULTS: A two-way repeated-measures ANOVA with subsequent post hoc analyses indicated significant increases in peak velocity (p < 0.01; ES = 0.91) and mean velocity (p < 0.01; ES = 0.78) after the intake of CAF-6 compared to CON. The study did not show significant differences in bar velocity between CAF-6 and PLAC and between CAF-3 and PLAC. No significant differences in bar velocity were observed between CAF-3 and CAF-6 conditions. CONCLUSION: These results suggest that 6 mg/kg of caffeine can be an effective dose to improve power-specific training outcomes in women habituated to caffeine. However, the ergogenic effect of 6 mg/kg of caffeine may be derived from a combination of biological effects and expectancy, as this dose was only superior to the control condition with no differences over the placebo.

Caffeine increases exercise intensity and energy expenditure but does not modify substrate oxidation during 1 h of self-paced cycling.

AIM: Oral caffeine intake has been deemed as an effective supplementation strategy to enhance fat oxidation during aerobic exercise with a steady-state intensity. However, in real exercise scenarios, individuals habitually train with autoregulation of exercise intensity. This study aimed to analyze the effect of oral caffeine intake during self-paced cycling on autoregulated exercise intensity and substrate oxidation. METHODS: Fifteen young and healthy participants (11 men and 4 women) participated in a double-blind, randomized, cross-over investigation. Each participant took part in 2 experimental days consisting of pedaling for 1 h with a self-selected wattage. Participants were told that they had to exercise at a moderate intensity to maximize fat oxidation. On one occasion participants ingested 3 mg/kg of caffeine and on the other occasion ingested a placebo. Energy expenditure, fat oxidation rate, and carbohydrate oxidation rate were continuously measured during exercise by indirect calorimetry. RESULTS: In comparison to the placebo, caffeine intake increased the self-selected wattage (on average, 105 ± 44 vs 117 ± 45 W, respectively, P < 0.001) which represented a higher total work during the cycling session (377 ± 157 vs 422 ± 160 kJ, P < 0.001). Caffeine increased total energy expenditure (543 ± 161 vs 587 ± 155 kcal, P = 0.042) but it did not affect total fat oxidation (24.7 ± 12.2 vs 22.9 ± 11.5 g, P = 0.509) or total carbohydrate oxidation (87.4 ± 22.4 vs 97.8 ± 32.3 g, P = 0.101). CONCLUSION: Acute caffeine ingestion before an exercise session with an individual's freedom to regulate intensity induces a higher self-selected exercise intensity and total work. The selection of a higher exercise intensity augments total energy expenditure but eliminates the effect of caffeine on substrate oxidation during exercise.

Risk or benefit? Side effects of caffeine supplementation in sport: a systematic review.

PURPOSE: The aim of this study was to systematically review evidence on the prevalence and magnitude of side effects associated with caffeine supplementation in athletes. METHODS: Systematic searches through the PubMed, VHL, Scopus, and Web of Science databases were conducted according to the PRISMA guidelines. Peer-reviewed articles written in English that reported the prevalence/percentage or magnitude/effect size of side effects after caffeine supplementation in athletes in a sports context were included. Studies were grouped by the dose of caffeine administered as follows: low = ≤ 3.0 mg/kg; moderate = from 3.1 to 6.0 mg/kg; high = ≥ 6.1 mg/kg. The magnitude of the side effects was calculated with effect sizes. RESULTS: The search retrieved 25 studies that met the inclusion/exclusion criteria with a pooled sample of 421 participants. The supplementation with caffeine produced a higher prevalence or magnitude of all side effects under investigation when compared to placebo/control situations. The prevalence (magnitude) was between 6 and 34% (ES between 0.13 and 1.11) for low doses of caffeine, between 0 and 34% (ES between -0.13 and 1.20) for moderate doses of caffeine, and between 8 and 83% (ES between 0.04 and 1.52) with high doses of caffeine. The presence of tachycardia/heart palpitations and the negative effects on sleep onset had the highest prevalence and magnitude, in athletes using supplementation with caffeine. CONCLUSION: In summary, caffeine supplementation in the doses habitually used to enhance physical performance produces several side effects, both after exercise and at least 24 h after the ingestion. However, the prevalence and magnitude of side effects with high doses of caffeine were habitually higher than with low doses of caffeine. From a practical perspective, using ~3.0 mg/kg of caffeine may be the dose of choice to obtain the ergogenic benefits of caffeine with the lowest prevalence and magnitude of side effects.

Genetics and sports performance: the present and future in the identification of talent for sports based on DNA testing.

The impact of genetics on physiology and sports performance is one of the most debated research aspects in sports sciences. Nearly 200 genetic polymorphisms have been found to influence sports performance traits, and over 20 polymorphisms may condition the status of the elite athlete. However, with the current evidence, it is certainly too early a stage to determine how to use genotyping as a tool for predicting exercise/sports performance or improving current methods of training. Research on this topic presents methodological limitations such as the lack of measurement of valid exercise performance phenotypes that make the study results difficult to interpret. Additionally, many studies present an insufficient cohort of athletes, or their classification as elite is dubious, which may introduce expectancy effects. Finally, the assessment of a progressively higher number of polymorphisms in the studies and the introduction of new analysis tools, such as the total genotype score (TGS) and genome-wide association studies (GWAS), have produced a considerable advance in the power of the analyses and a change from the study of single variants to determine pathways and systems associated with performance. The purpose of the present study was to comprehensively review evidence on the impact of genetics on endurance- and power-based exercise performance to clearly determine the potential utility of genotyping for detecting sports talent, enhancing training, or preventing exercise-related injuries, and to present an overview of recent research that has attempted to correct the methodological issues found in previous investigations.

The Effects of Match Congestion on Physical Performance in Football Referees.

We examined the changes in performance during congested (two matches within a 7-day interval) and non-congested (one match within≥7-day interval) fixtures in 17 elite football (soccer) referees during 181 official matches. External demands comprised 20 GPS-based metrics. Internal load was assessed by heart rate and rating of perceived exertion. Compared to non-congested fixtures, referees decreased their running distance at 21-24 km·h-1 (p=0.027, effect size [ES]=0.41) and > 24 km·h-1 (p=0.037, ES=0.28), the number of sprints (p=0.012, ES=0.29), and distance sprinting (p=0.022, ES=0.29) in congested matches. Most play metrics were lower in congested versus non-congested fixtures with low-to-moderate ES. During the 2nd half of non-congested fixtures, referees covered larger distances at low-speed running (p=0.025, ES=0.47). Match congestion due to officiating two matches less than a week apart caused a notable decrease in match running activity in professional football referees, especially at above 21 km·h-1. These data reiterate the need for specific conditioning and post-match recovery strategies in high-level referees to ensure optimal judgment performance favouring the quality of the competition. Governing bodies should take these outcomes into account when designating referees for a match.

Influence of the Weekly and Match-play Load on Muscle Injury in Professional Football Players.

The aim of this investigation was to examine the impact of the weekly training load and the match running patterns prior to a muscle injury as potential risk factors of muscle injury in professional football players. Forty male professional football players participated in the investigation. Running distances at different intensities 5 min and 15 min prior to the injury were compared to the same time-points in official matches of the same player with no injury events. Furthermore, the cummulative session rating of perceived exertion (sRPE) and training load of the week prior to the injury were compared to a control week (mean value of training weeks without injury). Nineteen players suffered 31 non-contact muscle injuries during matches. The distance covered at 21-24 km/h (p<0.001; effect size (ES)=0.62) and at>24 km/h (p=0.004; ES=0.51) over the 5-min period prior to the injury was greater than in matches without injury. The cumulative sRPE (p=0.014; ES=1.33) and training volume (p=0.002; ES=2.45) in the week prior to the injury was higher than in a control week. The current data suggest that the combination of a training week with a high load and a short period of high intensity running during the match might increase the risk of muscle injury in professional footballers.

Association between offensive and defensive playing style variables and ranking position in a national football league.

The aim of this study was to determine the association of playing style and efficacy variables with football success in a professional football league. Match statistics were obtained from 23 football teams competing in the 2017-2018 and 2018-2019 seasons of the Spanish national league(LaLiga). Offensive and defensive playing style and efficacy variables were calculated. Pearson's correlation coefficient tests and principal component analysis (PCA) were applied to establish the influence of these variables on the number of points obtained at the end of the season and on the ranking position. In isolation, the efficacy of completion showed the highest association with ranking points and position. A two-dimension PCA explained 77.8% of the variance in the ranking position. In dimension-1 (58.5%), game initiative and attack building, and in dimension-2 (19.3%), efficacy of defensive containment and a lower rate of long passes were within the variables that explained more variance in the ranking position. Success in football, measured by ranking position at the end of the Spanish national league, was associated with several playing style and efficacy variables. Overall, a dominant game style with high efficacy to finish attacking plays, and an offensive game initiative, are most associated with successful football.

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

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

Intra and inter-tester reliability of a novel device to assess gluteal muscle strength in professional football players.

The aim of this study is to investigate inter-tester and intra-tester reliability of a novel clam test (CLAMT) for the measurement of gluteal muscle strength and to detect possible differences between CLAMT values in football players with and without a history of groin injuries. Twenty male football players participated in the test-retest and sixty-two male professional football players participated in the case-control study. Hip abductor maximal muscle strength was evaluated either using CLAMT or in a supine position with the hip in a neutral pose. For CLAMT, intraclass correlation coefficient (ICC) for inter-tester-intra-day reliability was 0.80 (95% CI: 0.60-0.90), with a standard error of measurement of 34.2 N. The intra-tester-intra-day ICC was 0.92 (95% CI: 0.87-0.95), with a standard error of measurement of 23.6 N. The inter-week ICC was 0.96 (95% CI: 0.92-0.98), with a standard error of measurement of 18.9 N. CLAMT showed lower (but not significant) strength values in football players with a history of groin injuries to non-injured players. CLAMT showed good to excellent levels of reliability, intraday and inter-week, with low standard errors of measurement while it was effective (possible) to identify residual weakness in players with previous groin injuries.

Effects of acute caffeine ingestion on futsal performance in sub-elite players.

PURPOSE: To date, no previous investigation has studied the effect of acute caffeine ingestion on futsal performance during futsal-specific testing and during a simulated match. Therefore, the aim of this investigation was to establish the effects of acute caffeine intake on futsal-specific tests and match-play running performance in male futsal players. METHODS: Sixteen high-performance futsal players participated in a randomized, crossover, placebo-controlled and double-blind experiment. Each player completed two identical trials after ingesting either caffeine (3 mg/kg) or a placebo (cellulose). The trials consisted of a battery of futsal-specific tests (countermovement jump, 20-m sprint test, and a futsal kicking velocity and accuracy test) followed by a simulated futsal match (2 halves of 7.5 min). During the match, players' running performance was assessed with local positioning system devices. RESULTS: In comparison to the placebo, caffeine ingestion increased jump height by 2.8% (p = 0.048; ES = 0.29) and reduced the time to complete the 20-m sprint test by -2.2% (p = 0.044; ES = - 0.54). Additionally, acute caffeine intake improved the distance covered at above 14.4 km/h by 19.6% (p = 0.021; ES = 0.58), the number of body impacts by 8.1% (p = 0.040; ES = 0.27) and the number of accelerations/decelerations by 4.2% (p = 0.044; ES = 0.57) during the simulated futsal match. However, no differences were reported in ball velocity or shooting accuracy in the futsal kicking test. There were no differences in the prevalence of side effects reported in the hours after the ingestion of the treatments. CONCLUSION: Three mg/kg of caffeine enhanced several physical variables associated with futsal such as jump and sprint performance, and improved high-speed running and accelerations/decelerations during a simulated futsal match. Caffeine supplementation with a moderate dose can be considered as an effective ergogenic aid for futsal performance with low prevalence of side effects. TRIAL REGISTRATION: The study was registered in ClinicalTrials.gov with the following ID: NCT04852315. The study was retrospectively registered by 18 April 2020.