Brain serotonin and dopamine modulators, perceptual responses and endurance performance during exercise in the heat following creatine supplementation

Background:The present experiment examined the responses of peripheral modulators and indices of brain serotonin (5-HT) and dopamine (DA) function and their association with perception of effort during prolonged exercise in the heat after creatine (Cr) supplementation. Methods:Twenty one endurance-trained males performed, in a double-blind fashion, two constant-load exercise tests to exhaustion at 63 ± 5% V O2 max in the heat (ambient temperature: 30.3 ± 0.5°C, relative humidity: 70 ± 2%) before and after 7 days of Cr (20 g·d-1 Cr + 140 g·d-1 glucose polymer) or placebo (Plc) (160 g·d-1 glucose polymer) supplementation.Results:3-way interaction has shown that Cr supplementation reduced rectal temperature, heart rate, ratings of perceived leg fatigue (P < 0.05), plasma free-tryptophan (Trp) (P < 0.01) and free-Trp:tyrosine ratio (P < 0.01) but did not influence the ratio of free-Trp:large neutral amino acids or contribute in improving endurance performance (Plc group, n = 10: 50.4 ± 8.4 min vs. 51.2 ± 8.0 min, P > 0.05; Cr group, n = 11: 47.0 ± 4.7 min vs. 49.7 ± 7.5 min, P > 0.05). However, after dividing the participants into "responders" and "non-responders" to Cr, based on their intramuscular Cr uptake, performance was higher in the "responders" relative to "non-responders" group (51.7 ± 7.4 min vs.47.3 ± 4.9 min, p < 0.05).Conclusion:although Cr influenced key modulators of brain 5-HT and DA function and reduced various thermophysiological parameters which all may have contributed to the reduced effort perception during exercise in the heat, performance was improved only in the "responders" to Cr supplementation. The present results may also suggest the demanding of the pre-experimental identification of the participants into "responders" and "non-responders" to Cr supplementation before performing the main experimentation. Otherwise, the possibility of the type II error may be enhance

Network Agency

The question of agency has been neglected in social network research, in part because the structural approach to social relations removes consideration of individual volition and action. But recent emphasis on purposive individuals has reignited interest in agency across a range of social network research topics. Our paper provides a brief history of social network agency and an emergent framework based on a thorough review of research published since 2004. This organizing framework distinguishes between an ontology of dualism (actors and social relations as separate domains) and an ontology of duality (actors and social relations as a mutually constituted) at both the individual level and at the social network level. The resulting four perspectives on network agency comprise individual advantage, embeddedness, micro-foundations, and structuration. In conclusion, we address current debates and future directions relating to sources of action and the locus of identity

The between-week reliability of neuromuscular, endocrine, and mood markers in soccer players and the repeatability of the movement demands during small-sided games

BACKGROUND: Establishing the reliability and repeatability of both the movement demands and the consequential responses of athletes applied settings is important. Therefore, the primary aim of this study was to assess the between-week reliability of potential fatigue monitoring methods in soccer players. Secondary aims were to establish the repeatability of the movement demands and the changes in monitoring variables from the same small-sided game (SSG) protocol programmed on consecutive weeks. METHODS: Twelve semi-professional soccer players (age, 21±2 years; mass, 80.1±6.8kg; height, 1.81±0.06m) performed the same SSG protocol (4vs4+goalkeepers; 6x7-min, 2-min inter-set recovery) separated by 7 days. Movement demands were monitored using global positioning systems (GPS), with countermovement jump (CMJ), saliva (testosterone and cortisol), and brief assessment of mood (BAM+) collected immediately pre and post SSG training. RESULTS: Results suggest that CMJ variables and hormonal markers have good between-week reliability when measuring athletes at rest (CV, 2.1–7.7%; ICC, 0.82–0.98), however BAM+ did not (CV, 23.5%; ICC, 0.47). GPS variables presented low to high repeatability during SSG training, with reliability statistics varying between metrics (CV, 4.4–62.4%; ICC, 0.30–0.81). In detecting responses from pre- to post-SSG training, CMJ and hormonal markers showed moderate to very-high reliability (ICC, 0.68–0.99), whilst BAM + did not (ICC, 0.12). CONCLUSIONS: The findings from this study suggest CMJ and hormonal markers provide good between-week reliability, yet caution should be applied when using short subjective questionnaires. Additionally, some movement demands may not be repeatable when programming the same SSG session on separate occasions

Neuromuscular, biochemical, endocrine, and mood responses to small-sided games' training in professional soccer

The 24h responses to small-sided games (SSG) soccer training were characterized. Professional soccer players (n=16) performed SSG’s (4vs4 + goalkeepers; 6x7-min, 2-min inter-set recovery) with performance (peak-power output, PPO; jump height, JH), physiological (blood creatine kinase: CK, lactate; salivary testosterone, cortisol), and mood measures collected before (baseline), and after (immediately; 0h, +2h, +24h). For PPO and JH, possibly small-moderate reductions occurred at 0h (-1.1W·kg-1; ±0.9W·kg-1, -3.2cm; ±1.9cm, respectively), before returning to baseline at +2h (trivial) and declining thereafter (small-moderate effect) at +24h (-0.9W·kg-1; ±0.8W·kg-1, -2.5cm; ±1.2cm, respectively). Lactate increased at 0h (likely-large; +1.3mmol·L-1; ±0.5mmol·L-1), reduced at +2h (likely-small; -0.5mmol·L-1; ±0.2mmol·L-1), and returned to baseline at 24h (trivial). A very-likely small increase in CK occurred at 0h (+97u·L-1; ±28u·L-1), persisting for +24h (very-likely small; +94u·L-1; ±49u·L-1). Possibly-small increases in testosterone (+20pg·ml-1; ±29pg·ml-1) occurred at 0h, before likely-moderate declines at +2h (-61pg·ml-1; ±21pg·ml-1) returning to baseline at +24h (trivial). For cortisol, possibly-small decreases occurred at 0h (-0.09ug·dl-1; -±0.16ug·dl-1), before likely-large decreases at +2h (-0.39ug·dl-1; ±0.12ug·dl-1), which persisted for 24h (likely-small; -0.12ug·dl-1; ±0.11ug·dl-1). Mood was disturbed by SSG’s at 0h (likely-moderate; +13.6AU, ±5.6AU) and +2h (likely-small; +7.9AU; ±5.0AU), before returning to baseline at +24h (trivial). The movement demands of SSG’s result in a bimodal recovery pattern of neuromuscular function and perturbations in physiological responses and mood for up to 24h. Accordingly, when programming soccer training, SSG’s should be periodized throughout the competitive week with submaximal technical/tactical activities

The effect of training order on neuromuscular, endocrine and mood response to small-sided games and resistance training sessions over a 24-h period

Objectives: This study examined the acute effect of small-sided-game (SSG) and resistance training sequence on neuromuscular, endocrine and mood response over a 24-hour (h) period. Design: Repeated measures Methods: Fourteen semi-professional soccer players performed SSG-training (4vs4 + goalkeepers; 6x7-min, 2-min inter-set recovery) followed by resistance training 2h later (back-squat, Romanian deadlift, barbell-hip-thrust; 4x4 repetitions, 4-min inter-set recovery; 85% 1 rep-max) (SSG+RES), and on a separate week reversed the session order (RES+SSG). Physical demands of SSG’s were monitored using global positioning systems (GPS) and ratings of perceived exertion (RPE). Countermovement-jump (CMJ; peak power output; jump height) and brief assessment of mood were collected before (pre), during (0h) and after (+24h) both protocols. Salivary testosterone and cortisol concentrations were obtained at the same time-points but with the inclusion of a measure immediately prior to the second training session (+2h). Results: GPS outputs and RPE were similar between SSG-training during both protocols. Between-protocol comparisons revealed no significant differences at +24h in CMJ performance, mood, and endocrine markers. Testosterone was higher at 0h during RES+SSG in comparison to SSG+RES (moderate-effect; +21.4±26.7 pg·ml-1; p= 0.010), yet was similar between protocols by +2h. Conclusions: The order of SSG and resistance training does not appear to influence the physical demands of SSG’s with sufficient recovery between two sessions performed on the same day. Session order did not influence neuromuscular, endocrine or mood responses at +24h, however a favourable testosterone response from the resistance first session may enhance neuromuscular performance in the second session of the day

Association between MAPT polymorphism but not APOE promoter and elite rugby athlete status

INTRODUCTION: Incidence and outcomes of concussions have been hypothesised to be genetically influenced. The APOE Promoter G219T (rs405509) polymorphism has been associated with differential promoter activity and unfavourable outcomes after traumatic brain injury. The TT genotype is associated with a 3-fold greater risk of multiple concussions. The TT genotype of MAPT (rs10445337) has also been associated with poorer outcomes after concussion. Rugby has one of the highest incidences of concussion in sport, so it was hypothesised that APOE Promoter TT and MAPT TT genotypes would be less prevalent in elite rugby athletes because those genotypes, previously associated with increased risk, would be less compatible with achieving elite athlete status. METHODS: Participants were from the RugbyGene project, comprising elite Caucasian male rugby athletes (n = 528; mean (standard deviation) height 1.85 (0.07) m, mass 101 (14) kg, age 29 (7) yr), including 420 rugby union (RU) athletes that for some analyses were divided into forwards and backs and 108 rugby league (RL) athletes. Non-athletes were 592 Caucasian men and women (57% male, height 1.72 (0.10) m, mass 74 (14) kg, age 31 (7) yr). PCR of genomic DNA was used to determine genotypes using TaqMan probes, then groups were compared using χ2 and odds ratio (OR) statistics. RESULTS: All genotype data were in Hardy-Weinberg equilibrium. For MAPT (rs10445337), the risk genotype (TT) was underrepresented in rugby athletes (60%) compared to non-athletes (66%), CT more common in rugby athletes (34%) than non-athletes (29%) and little difference in CC genotype frequencies (χ2 = 7.092, P = 0.029; TT genotype frequency OR = 0.80, 95% confidence intervals (CI) = 0.62-1.02). There were no differences in MAPT (rs10445337) genotype frequencies between RU forwards and backs. For APOE Promoter G219T (rs405509), there were no differences in genotype frequencies between all athletes (RU and RL) and non-athletes (27% TT genotype in players and non-athletes), nor between RU forwards and backs. CONCLUSION: The MAPT (rs10445337) TT genotype is 6% less common in elite rugby athletes than non-athletes. Therefore, carrying at least one rs10445337 C allele appears to increase the probability of sustained career success in the high-risk concussion environment of elite rugby, perhaps via a greater ability to recover from concussions.Peer reviewe

Association of MMP3 but not TIMP2 gene variants with elite rugby player status and rugby code

Introduction: Achilles tendon pathology and anterior cruciate ligament rupture are multifactorial conditions for which genetic risk factors have been identified. Single nucleotide polymorphisms (SNPs) within the MMP3 (rs591058, rs679620, rs650108) and TIMP2 (rs4789932) genes have previously been associated with tendon and ligament pathologies. Although not entirely clear, prior literature indicates the risk alleles for Achilles tendon pathology as T (rs591058), G (rs679620) and A (rs650108) for MMP3. However, prior evidence regarding TIMP2 is equivocal. MMP3 is considered an essential regulator of matrix degradation and remodelling within diseased and normal musculoskeletal soft tissues. TIMP2 maintains homeostasis in the extracellular matrix in part by inhibiting MMP function. Given the high incidence and severity of tendon and ligament injuries in elite rugby athletes, we hypothesised that the aforementioned SNPs would be associated with career success. Methods: Participants from the RugbyGene project were elite Caucasian male rugby athletes (n = 566; mean (standard deviation) height 1.85 (0.07) m, mass 101 (14) kg, age 29 (7) yr), including 420 rugby union (RU) athletes that for some analyses were divided into forwards and backs and 120 rugby league (RL) athletes. Non-athletes were 589 Caucasian men and women (n = 589, 57% male, height 1.72 (0.10) m, mass 74 (14) kg, age 31 (7) yr). PCR of genomic DNA was used to determine genotypes using TaqMan probes, then groups were compared using Χ2 and odds ratio (OR) statistics. Results: As hypothesized, the MMP3 rs591058 risk genotype (TT) was less frequent in rugby athletes (28%) compared to non-athletes (33%) (Χ2 = 7.265, P = 0.026; OR = 1.18, 95% confidence intervals (CI) = 0.86-1.63). No differences were found for MMP3 rs679620, rs650108 or TIMP2 rs4789932 between rugby athletes and non-athletes. When RL athletes were compared to non-athletes, the risk genotype (TT) of MMP3 rs591058 was underrepresented in RL athletes (19%) compared to non-athletes (33%). The MMP3 rs679620 ‘protective’ allele (C) was more frequent in RL athletes (55%) compared to non-athletes (48%) (OR = 1.3, 95% CI = 0.98-1.74). However, for MMP3 rs650108 the ‘risk’ allele (A) was overrepresented in RL athletes (32%) compared to non-athletes (26%). There were no genotype differences for any gene variant between RU athletes and non-athletes. The ‘risk’ allele (T) of the MMP3 rs679629 polymorphism and the ‘protective’ allele (G) of the MMP3 rs650108 polymorphism were less common in RL (45%, 68%, respectively) than RU athletes (54%, 76%, respectively). Conclusion: We provide evidence for elite rugby athletes possessing a protective genetic profile regarding tendon and ligament injury risk. Notably, a less frequent rs591058 TT genotype in athletes suggests a lower risk of injury could therefore enhance career success in rugby. Furthermore, RL players appear to have differing genetic characteristics compared to their RU counterparts, which might reflect some differences in physiological demands between codes.Peer reviewedFinal Published versio

The paradox of agency: feeling powerful reduces brokerage opportunity recognition yet increases willingness to broker

Research suggests positions of brokerage in organizational networks provide many benefits, but studies tend to assume everyone is equally able to perceive and willing to act on brokerage opportunities. Here we challenge these assumptions in a direct investigation of whether people can perceive brokerage opportunities and are willing to broker. We propose that the psychological experience of power diminishes individuals’ ability to perceive opportunities to broker between people who are not directly connected in their networks, yet enhances their willingness to broker. In Study 1, we find that employees in a marketing and media agency who had a high sense of power were likely to see fewer brokerage opportunities in their advice networks. In Study 2, we provide causal evidence for this claim in an experiment where the psychological experience of power is manipulated. Those who felt powerful, relative to those who felt little power, tended to see fewer brokerage opportunities than actually existed, yet were more willing to broker, irrespective of whether there was a brokerage opportunity present. Collectively, these findings present a paradox of agency: Individuals who experience power are likely to underperceive the very brokerage opportunities for which their sense of agency is suited. (PsycINFO Database Record (c) 2018 APA, all rights reserved

The Effects Of Female Size On Fecundity In A Large Marine Gastropod Rapana Venosa (Muricidae)

The life history strategy of the veined rapa whelk Rapana venosa, a temperate marine gastropod, includes generation times of 1 y, individual longevity of \u3e 10 y, annual production of egg cases, and an adult size range of 40 to \u3e 160 mm shell length (SL). This life history combined with the animal\u27s generalist ecological preferences and broad physiological tolerances makes rapa whelks well suited for ecological success along a gradient of habitat and community types. Ballast water transport of veliger larvae across traditional zoogeographic boundaries has resulted in the establishment of invasive rapa whelk populations in Chesapeake Bay, USA, as well as European habitats. Although the need for a quantitative understanding of rapa whelk reproductive biology in terms of annual embryo production or fecundity is acknowledged as a necessary step in assessing the biological and ecological consequences of such an invasion, rapa whelk fecundity in relation to size for the entire adult size range (40-\u3e 160 mm SL) has not previously been quantified. The relationships between rapa whelk female size and egg case height, number of embryos egg case(-1), number of egg cases produced female whelk(-1) yr(-1) and fecundity, and the number of embryos female-(1) yr(-1), are described for a size range of individuals from Chesapeake Bay. In 2001 and 2003, egg laying began in mid to late May at water temperatures of approximately 18 degrees C and salinities 14-20 ppt and continued for 11-12 wk. The smallest rapa whelk observed (45 mm SL, 5.8 g wet tissue weight) laid egg cases with heights of approximately 7 mm. The largest whelk (163 mm SL, 220 g) laid egg cases with heights 30-33 mm. The number of embryos observed in egg cases produced by Chesapeake Bay rapa whelks ranged from 123 embryos in a 7.4 mm high egg case to 3,673 embryos in a 33.5 mm high egg case. Rapa whelk fecundity (number of embryos female(-1)yr(-1)) increased with female size. Egg case production was observed in rapa whelks that had hatched from egg cases and recruited within the previous year (\u3c 1 y old). Small (\u3c 80 mm SL, \u3c 28 g wet tissue weight) rapa whelks have relatively lower annual fecundities (1 x 10(5) embryos fernale(-1) yr(-1)) than large (\u3e 80 mm SL, \u3e 28 g wet tissue weight) rapa whelks that may produce between 1 x 10(6) and 4 x 10(6) embryos female(-1) yr(-1). Estimates of rapa whelk fecundity, even for small rapa whelks, are at least an order of magnitude greater than similar estimates for native United States Atlantic coast gastropods

Physical characteristics underpinning lunging and change of direction speed in fencing

Lunge velocity (LV) and change of direction speed (CODS) are considered fundamental to success during fencing competitions; investigating the physical characteristics that underpin these is the aim of this study. Seventy fencers from the British Fencing National Academy took part and on average (± SD) were 16.83 ± 1.72 years of age, 178.13 ± 8.91 cm tall, 68.20 ± 9.64 kg in mass and had 6.25 ± 2.23 years fencing experience. The relationship between anthropometric characteristics (height, arm-spam and adductor flexibility) and measures of lower-body power (bilateral and unilateral countermovement jump height and reactive strength index) were examined in their ability to influence LV and CODS. In testing the former, fencers lunged (over a self-selected distance) to and from a force plate, where front leg impact and rear leg propulsive force was quantified; the lunging distance was divided by time to establish LV. CODS was measured over 12 m involving shuttles of between 2 and 4 m. Results revealed that LV and CODS averaged at 3.35 m/s and 5.45 s respectively and in both cases, standing broad jump was the strongest predictor (r = 0.51 and -0.65 respectively) of performance. Rear leg drive and front leg impact force averaged at 14.61 N/kg and 3-times bodyweight respectively, with single leg jumps revealing an asymmetry favoring the front leg of 9%. In conclusion, fencers should train lower-body power emphasizing horizontal displacement, noting that this seems to offset any advantage one would expect fencers of a taller stature to have. Also, the commonly reported asymmetry between legs is apparent from adolescence and thus also requires some attention