Explore the vast range of titles available.

Purpose The aim of this study was to investigate the association of rs6598964 (A > G), a molecular marker located in the LIN28A gene, with the performance of Brazilian soccer players using the VO 2 max predicted by performance in the Yo-Yo test as the phenotype. Methods The study sample comprised 227 male players on a team in the first division of Brazilian soccer distributed in the following categories: U15 ( n  = 67, VO2max = 52.75 ± 4.74 ml/kg/min), U17 ( n  = 43, VO2max = 54.37 ± 5.47 ml/kg/min), U20 ( n  = 79, VO2max = 54.97 ± 5.13 ml/kg/min), and Professional ( n  = 38, VO2max = 55.84 ± 4.37 ml/kg/min). Genotype models (codominance, A-recessive, A-dominant and overdominance models) were tested using Kruskal–Wallis and Mann–Whitney tests with Bonferroni correction for multiple comparisons tests. Results Significantly higher predicted VO2max was observed in individuals with the A/A genotype (VO2max = 62.12 ± 3.97 mL/kg/min) compared to both the A/G (53.44 ± 8.88 mL/kg/min) and G/G (52.44 ± 6.11 mL/kg/min) genotypes ( p  < 0.001). Model comparisons suggested the differences in predicted VO2max were best explained by the A-recessive model. Conclusion This study is the first to associate the LIN28A polymorphism with endurance performance in soccer players. However, further studies are needed to confirm the associations described here and to investigate how LIN28A interacts with other genes related to athletic performance.

Environmental heat stress impairs endurance performance by enhancing exercise-induced physiological and perceptual responses. However, the time course of these responses during self-paced running, particularly when comparing hot and temperate conditions, still needs further clarification. Moreover, monitoring fatigue induced by exercise is paramount to prescribing training and recovery adequately, but investigations on the effects of a hot environment on post-exercise neuromuscular fatigue are scarce. This study compared the time course of physiological and perceptual responses during a 10 km self-paced treadmill run (as fast as possible) between temperate (25°C) and hot (35°C) conditions. We also investigated the changes in countermovement jump (CMJ) performance following exercise in these two ambient temperatures. Thirteen recreational long-distance runners (11 men and 2 women), inhabitants of a tropical region, completed the two experimental trials in a randomized order. Compared to 25°C, participants had transiently higher body core temperature (T CORE ) and consistently greater perceived exertion while running at 35°C ( p < 0.05). These changes were associated with a slower pace, evidenced by an additional 14 ± 5 min (mean ± SD) to complete the 10 km at 35°C than at 25°C ( p < 0.05). Before, immediately after, and 1 h after the self-paced run, the participants performed CMJs to evaluate lower limb neuromuscular fatigue. CMJ height was reduced by 7.0% (2.3 ± 2.4 cm) at 1 h after the race ( p < 0.05) compared to pre-exercise values; environmental conditions did not influence this reduction. In conclusion, despite the reduced endurance performance, higher perceived exertion, and transiently augmented T CORE caused by environmental heat stress, post-exercise neuromuscular fatigue is similar between temperate and hot conditions. This finding suggests that the higher external load (faster speed) at 25°C compensates for the effects of more significant perceptual responses at 35°C in inducing neuromuscular fatigue.

Methodology: Ten well trained male subjects (means 26 years old, range 22-31; 64kg of body weight, range 55-77 and 71mLkg+1min+1 maximal oxygen consumption, range 53-80) completed 5kmx60km cycling time trials (TT) punctuated with 4kmx1km sprints at 14, 29, 44 and 59km in a 5x5 latin square design. The mean number...

PurposeThis study investigated the effects of both an active warm-up and the time-of-day variation on repeated-sprint performance. A second objective was to compare the post-exercise recovery between the experimental conditions.MethodsEleven male participants performed ten maximal cycling sprints (6 s each, with a 30-s interval between them) in the morning and late afternoon, either after a warm-up or control condition. The warm-up consisted of cycling for 10 min at 50% of the peak aerobic power.ResultsRest measurements of rectal, muscle, and skin temperatures were higher in the afternoon compared to the morning (p < 0.05), with no significant differences in heart rate (p = 0.079) and blood lactate concentration (p = 0.300). Warm-up increased muscle temperature, heart rate, and lactate, and reduced skin temperature (all p < 0.001), though no significant differences were observed for rectal temperature (p = 0.410). The number of revolutions (p = 0.034, ηp2 = 0.375), peak (p = 0.034, ηp2 = 0.375), and mean (p = 0.037, ηp2 = 0.365) power of the first sprint (not the average of ten sprints) were higher in the afternoon compared to the morning, regardless of warm-up. However, beneficial performance effects of warming up were evident for the first (p < 0.001) and the average of ten sprints (p < 0.05), regardless of time of day. More remarkable changes during the 60-min post-exercise were observed for rectal temperature (p = 0.005) and heart rate (p = 0.010) in the afternoon than in the morning.ConclusionWarming-up and time-of-day effects in enhancing muscular power are independent. Although warm-up ensured further beneficial effects on performance than the time-of-day variation, a faster post-exercise recovery was observed in the late afternoon.

Genetic factors can interfere with sporting performance. The identification of genetic predisposition of soccer players brings important information to trainers and coaches for individual training loads adjustment. Different responses to eccentric training could be observed by the genotype referred to as α-actinin-3 (ACTN3) in biomarkers of muscle damage, hormones and inflammatory responses. The aim of this study was to compare acute inflammatory responses, muscle damage and hormonal variations according to the eccentric training in soccer professional athletes with different genetic profiles of ACTN3 (XX, RX and RR). 37 soccer professional athletes (9 XX, 13 RX, 15 RR) were randomly divided into five stations associated to eccentric muscle contraction and plyometrics. Blood samples were taken from athletes pre-eccentric training, immediately after (post), 2- and 4-h post-eccentric training to determine hormone responses (cortisol and testosterone), muscle damage (CK and α-actin), and inflammatory responses (IL-6). After eccentric training, athletes XX presented higher levels for CK (4-h post), α-actin (post and 2-h post) and cortisol (post) compared to RR and RX athletes. However, RR and RX athletes presented higher levels of testosterone (post) and IL-6 (2 h post and 4 h post) compared to athletes XX. The main conclusion of this study is that professional soccer athletes homozygous to ACTN3XX gene are more susceptible to eccentric damage and present a higher catabolic state, demonstrated by metabolic, hormonal and immune responses post an eccentric training, in comparison to ACTN3RR and ACTN3RX groups.

The aim of the present study was to compare the highest heart rate (HR) of soccer players recorded during competition matches with the maximum HR (HR(max)) estimated from age and the highest HR recorded in effort tests within a single category (intracategory) and between categories (intercategories). The sample was made up of 19 under-17 athletes, 12 under-20 athletes and 14 professional athletes of a Brazilian first division soccer team. Players' HR was monitored during official competition matches and maximum effort test with a set of HR monitors. The highest HR recorded during competitive matches (MHR1) was considered as the highest HR value attained by each player during matches. HR(max) estimated from age (MHR2) was estimated by using the equation HR(max)= (220-age). The highest HR recorded in effort tests (MHR3) was determined as being the highest HR value recorded during a maximum effort test (1 000-m run). The Wilcoxon test was used in intracategory statistical analysis. The Kruskal Wallis test was used in intercategory statistical analysis. The significance level adopted was P<0.05. In all categories, MHR3 was lower than MHR1. Concerning intercategory analysis, the three categories did not exhibit a difference in MHR1 Relative to MHR3, the under-17 and under-20 categories were not different from each other. These two categories exhibited larger MHR3 values than the professional one did. HR(max) measured during field tests can be underestimated in relation to that measured during competition activities, maybe because the tests represent an artificial situation for athletes, who do not feel as motivated as during competitions.

This study evaluated double blind ingestions of placebo (PLA) versus 6% carbohydrate (CHO) either as capsules (c) or beverage (b) during 60 km self-paced cycling in the heat (32°C and 50% relative humidity). Ten well-trained males (mean ± SD: 26±3 years; 64.5±7.7 kg and 70.7±8.8 ml.kg-1.min-1 maximal oxygen consumption) completed four separate 60 km time trials (TT) punctuated by 1 km sprints (14, 29, 44, 59 km) whilst ingesting either PLAb or PLAc or CHOb or CHOc. The TT was not different among treatments (PLAb 130.2±11.2 min, CHOb 140.5±18.1 min, PLAc 143.1±29.2 min, CHOc 137.3±20.1 min; P>0.05). Effect size (Cohen's d) for time was only moderate when comparing CHOb - PLAb (d = 0.68) and PLAb - PLAc (d = 0.57) whereas all other ES were 'trivial' to 'small'. Mean speed throughout the trial was significantly higher for PLAb only (P<0.05). Power output was only different (P<0.05) between the sprints and low intensity efforts within and across conditions. Core and mean skin temperatures were similar among trials. We conclude that CHO ingestion is of little or no benefit as a beverage compared with placebo during 60 km TT in the heat.

Lacerda, ACR, Alecrim, P, Damasceno, WC, Gripp, F, Pinto, KMC, and Silami-Garcia, E. Carbohydrate ingestion during exercise does not delay the onset of fatigue during submaximal cycle exercise. J Strength Cond Res 23(4)1276-1281, 2009-The objective of this study was to evaluate the effect of the ingestion of carbohydrate (CHO, in the form of maltodextrin) or placebo (PLAC, in the form of gelatin) on the physical performance of cyclists during submaximal exercise until fatigue on an ergometric cycle. Nine volunteers exercised on 2 separate occasions at least 2 days apart. On each occasion, after 48 hours of a balanced diet, they pedaled at approximately 66% o2peak until fatigue. Every 15 minutes, 150 mL of water and 18 capsules, containing either 0.5 g of CHO or PLAC (∼0.13 g·kg of body weight), were ingested in accordance with a double-blind, randomized protocol. The results show that after 40% of total exercise time, blood glucose levels in the CHO test returned to baseline levels. However, in the PLAC trial these levels failed to return to baseline levels, remaining lower than levels recorded in the CHO test after 60% of total exercise time. Despite these results, CHO ingestion failed to delay the onset of fatigue (CHO91.8 ± 10.1 minutes vs. PLAC93.3 ± 16.1 minutes; p = 0.87). In practical terms, coaches and trainers should consider that CHO ingestion in previously fed users does not delay the onset of fatigue during submaximal cycle exercise.

The aim of this study was to investigate the possibility of estimating the maximal lactate steady state (MLSS) on a cycle ergometer using the blood lactate concentrations [La^sup -^] of 4 mM (OBLA) and 5 mM (LA-5mM). Thirty-five volunteers (23.9±2.4 years, 75.9±7.3 kg and 47.8±4.9 mL*kg^sup -1^*min^sup -1^) performed an incremental test and 3 to 5 constant intensity exercises for the determination of MLSS. There was no difference between the MLSS intensity (177.9±36.8 W) and the LA-5mM (183.9±42.4 W). However, OBLA (168.3±42.8 W) underestimated the MLSS (p < .05). Heart rate (HR) in the MLSS (162.3±10.8 bpm) was similar to the HR in the LA-5mM (160.4±11.4 bpm), but was higher (p < .05) than HR in OBLA (151.6±12.4 bpm). There was no significant difference between the rate of perceived exertion in the MLSS (16±2), LA-5mM (17±1) and OBLA (16±2). Our results suggest that LA-5mM was more efficient to estimate the MLSS in cycle ergometer. [PUBLICATION ABSTRACT]