Christian J Cook

Christian J Cook
Bangor University

PhD (Paediatrics)

About

231
Publications
176,285
Reads
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8,553
Citations
Additional affiliations
January 2017 - present
University of Canberra
Position
  • Professor
June 2012 - December 2016
Bangor University
Position
  • Professor
January 2009 - present
Imperial College London
Position
  • Professor

Publications

Publications (231)
Article
Full-text available
The digit ratio (2D:4D) is a negative correlate of boy's physical fitness, and thought to arise from organizational effects of prenatal testosterone on different bodily systems. During human ontogeny, activational effects of testosterone on body size and strength offers another pathway to physical fitness. We tested these hypotheses by examining th...
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In this short report we explore the predictive nature of finger digit ratio (i.e., second/index finger length divided by fourth/ring finger length; 2D:4D) and achievement. This research, with niche and specialized populations, was intended to support and grow on knowledge obtained from other large population 2D:4D studies and help form a directiona...
Article
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The 24 h responses to professional female netball-specific training were examined. British Superleague players (n = 14) undertook a 90-min on-court training session incorporating key movement, technical, and scenario-specific match-play drills. Perceptual (mood, fatigue, soreness), neuromuscular (countermovement jump peak power output [PPO], PPO re...
Article
Objectives To compare two modes (general and cricket-specific) of morning priming exercise on afternoon physical and cognitive performance, and subjective readiness to perform in professional male cricketers. Design Randomised, crossover, counterbalanced. Methods On three occasions, 16 professional men’s cricketers completed afternoon tests of co...
Article
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Objective The hypothalamic-pituitary-gonadal (HPG) and -adrenal (HPA) axes are traditional viewed as mutually inhibitory systems. However, several diurnal studies have reported positive within-person testosterone and cortisol relationships, as evidence of facilitative processes, but with some constraints (e.g., low-frequency sampling, use of static...
Article
Studies indicate that high-frequency repetitive transcranial magnetic stimulation (HF-rTMS) can lower cortisol concentration or output, with some evidence suggesting a link to testosterone. Together, these stress and social hormones might help regulate the emotional response to HF-rTMS. This pilot study evaluated the effect of HF-rTMS on acute test...
Article
Purpose: To establish if training volume was associated with androgen baselines and androgen responsiveness to acute exercise. Methods: During a "high-volume" training phase, 28 cyclists (14 men and 14 women) undertook oxygen-uptake and maximal-work-capacity testing. Two days later, they completed a repeat-sprint protocol, which was repeated 3 w...
Article
Reproducibility of social research is ambitious, and evidence supporting this argument is increasing in psychology and social science research. This may be attributed to, in part, the high volume of qualitative research methodology used in social research along with difficulties in the reliability of measurement techniques. Therefore, use of more a...
Article
The 20 h responses of International female netball players to training days requiring two sessions (netball and strength, separated by two hours) ordered alternatively were examined. Eleven players completed strength followed by netball training two hours later (STR-NET), with the order reversed (NET-STR) on a separate day. Well-being, neuromuscula...
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Studies have compared HPA and HPG stress reactivity across the follicular and luteal phases to assess the menstrual impact of estradiol and progesterone fluctuations. Ovulatory shifts in baseline and stressor-induced testosterone among athletic women offer a new framework to explore these responses. Here we investigated menstrual variation in basel...
Article
In sport, testosterone has been positioned as a substrate for motivation with both directional and time dependencies. However, evidence is scarce when considering the complexities of competitive sport and no work has explicitly modeled these dependencies. To address these gaps, we investigated the bidirectional and time-dependent interrelationships...
Article
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High-performance sport coaches are leaders in their field; therefore, they sometimes operate under ‘regular’ workplace leadership role requirements. However, they are also subject to highly uncertain and pressured environments. Thus, most coaching/leadership positions in high-performance sport may be both ‘normal’ and ‘unique’ in leadership role re...
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Purpose: Reported associations between vitamin 25(OH)D and exercise performance are equivocal, perhaps due to complex interplay with cortisol and testosterone. In this study, the authors investigated serum 25(OH)D and cortisol as moderators of the testosterone relationship with exercise performance in adolescent male athletes. Methods: A total o...
Article
Background: The influence of menstrual cycle phase in perceptual responses and exercise performance still unclear in the literature. Therefore, the main aim of this study investigated salivary estradiol (sal-E2) and cortisol (sal-C) concentrations, mood, anxiety and exercise (aerobic, anaerobic) performance in physically-active women across two me...
Article
Purpose: This study aimed to examine the link between stress (measured via salivary cortisol and testosterone), cognition (measured via pupillometry, with greater pupil constriction and reduced pupil constriction latency associated with increased attention and improved information processing), and motor skill capacity (measured via somatosensory p...
Article
The physical demands of English Premier League soccer goalkeepers were quantified during training and match-play in a two-part study. Goalkeeper-specific micromechanical electrical systems (MEMS) devices, profiled training and match-day activities throughout one competitive week (n=8; part A). Changes in MEMS-derived outputs were also profiled thro...
Article
Objectives: Research has linked physiological (e.g., hormonal, affective, fatigue) outcomes to performance indicators in rugby competition, but no work has integrated and contextualised these factors within atest-match environment. We addressed this gap by monitoring 29 athletes from a training squad across eight international rugby matches. Design...
Article
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Purpose Team effectiveness is often predicated by a group’s ability to communicate. However, the effect of stress response on communication success, particularly nonverbal engagement, and how this might affect team performance, is not clear; a “phenomenon” this study sought to explore. Design/methodology/approach This was an observational study in...
Article
Background: Testosterone (T) is taken or prescribed to enhance appearance, increase athletic performance and libido and to treat hypogonadism. Digit ratio (2D:4D) is thought to be a negative correlate of prenatal T. Here we consider the relationship between 2D:4D and T supplementation. Aims: Our sample was taken from the BBC internet study. Resp...
Article
Objectives: This study profiled the 24h neuromuscular, endocrine and mood responses to a single versus a double training day in soccer players. Design: Repeated measures. Methods: Twelve semi-professional soccer players performed small-sided-games (SSG's; 4 vs 4+goalkeepers; 6×7-min, 2-min inter-set recovery) with neuromuscular (peak-power out...
Article
To examine responses to an International netball tournament, female athletes (n= 11) played three matches over consecutive days. External (accelerometry) and internal (heart rate; HR, session; sRPE, and differential; dRPE, rating of perceived exertion) load measures quantified match intensity. On match-day mornings, and three days after match 3, we...
Article
Literature suggests that women experience ovulatory shifts in risk-taking behaviours across different domains, which might be partly attributed to changes in testosterone (T). Thus, we investigated associations between menstrual variability in T concentrations and economic risk-related decisions among athletic women. Thirty-five women were monitore...
Article
BACKGROUND: The 2nd to 4th digit ratio (2D:4D) is regarded as a sexually dimorphic trait governed by prenatal testosterone (T) and estradiol exposure. However, relationships between the 2D:4D and adult sex hormone concentrations are inconsistent in females. Environmental contingencies (e.g., physical training) may provide a stronger basis for estab...
Article
This study examined a possible link between the elective preferences of medical students (surgical vs. non-surgical) and their emotional and hormonal responses to a psychological stressor. Forty medical students completed a laboratory stressor comprising of 10 puzzles in a time-limited format. Emotional state was assessed before (competitiveness, a...
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The cortisol (C) and testosterone (T) responses to experimental stress have been linked to sport and health outcomes several days to years later. Here we examined the utility of these biomarkers, taken across a simulated Olympic weightlifting (OWL) competition, as predictors of future competitive performance in young athletes. Seventy junior athlet...
Article
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Whilst the movement demands of players completing a whole soccer match have been well-documented, comparable information relating to substitutes is sparse. Therefore, this study profiled the match-day physical activities performed by soccer substitutes, focusing separately on the pre and post pitch-entry periods. Seventeen English Championship socc...
Article
Physiological monitoring solutions and biofeedback technologies allow sport psychology practitioners to demonstrate physiological changes due to psychological stress, and provide their clients with an enhanced awareness of their stress response. These technologies can also provide evidence for the efficacy of stress management techniques, whether c...
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Purpose: To examine changes in, and relationships between, sleep quality and quantity, salivary testosterone, salivary cortisol, testosterone-to-cortisol ratio (T:C), and self-reported muscle soreness during a residential-based training camp in elite rugby players. Methods: Nineteen male rugby players age 26.4 (3.9) years, height 186.0 (9.4) cm, an...
Article
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Goalkeepers are typically the last defensive line for soccer teams aiming to minimise goals being conceded, with match rules permitting ball handling within a specific area. Goalkeepers are also involved in initiating some offensive plays, and typically remain in close proximity to the goal line while covering ~ 50% of the match distances of outfie...
Article
The concept of competition has implications for educational contexts, as hormonal and emotional changes under competitive stress can modulate learning and memory processes. This study examined the impact of a competitive learning environment and associated hormonal and emotional responses on skill acquisition and expression in a medical domain. Usi...
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Depending upon competition regulations, the laws of soccer allow between three and an unlimited number of substitutions that can be made on either a permanent or rolling basis. Substitutes are typically introduced to minimise/offset the effects of fatigue, alter tactics, replace players deemed as underperforming or injured, and/or give playing time...
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The use of physical tests to profile physical capabilities, and provide training direction to athletes is common practice. Likewise, in professional team sports, notational analysis codes the key contributions of each player during competition. Limited studies have however investigated relationships between physical capabilities and key performance...
Data
(Table A) Game KPIs for International, European, and Premiership level rugby union during 2014–2015 season. Actions are per 80 mins of play. (Table B) Physical performance test results. (DOCX)
Article
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Pre-conditioning strategies to potentiate performance are a common feature of pre-competition routines. The elevation of muscle temperature is seen as a vital component of preparing for physical performance, while pre-cooling strategies have been adopted to offset fatigue during repeated efforts. We investigated the individual and combined effects...
Article
Human gaze is an important indicator of dominant and submissive behaviours related to positioning in a social hierarchy. This study investigated face gazing after a chance-determined contest and its linkage to salivary testosterone (sal-T) reactivity in athletic women. Twenty-six women athletes completed a coin-toss game on days 7 (D7), 14 (D14) an...
Article
Objective: This study examined the effect of a physical treatment (speed, power and strength training) and psychosocial treatment (group motivational presentation) on salivary testosterone (sal-T), salivary cortisol (sal-C), and sal-T to sal-C ratio (T:C) in professional rugby. Methods: Fourteen male rugby players aged 25.9 ± 2.5 years, height 1...
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The assessment of competitive movement demands in team sports has traditionally relied upon global positioning system (GPS) analyses presented as fixed-time epochs (e.g., 5–40 min). More recently, presenting game data as a rolling average has become prevalent due to concerns over a loss of sampling resolution associated with the windowing of data o...
Data
Main effect and interaction beta estimates for window length as a function of method. (DOCX)
Data
Estimates and confidence intervals for differences between forwards and backs as a function of method. (DOCX)
Article
Full-text available
Some equivocality exists regarding the effect of testosterone (T) on competitive performance with cortisol (C) implicated as a moderating factor. This study investigated whether C is moderating the T relationship with Olympic weightlifting (OWL) performance during real and simulated competitions. We monitored 105 male athletes (age 19.3±3.7 years);...
Article
Objectives The effects of vascular occlusion on recovery of physiological and neuromuscular markers over 24 h, and hormonal reactivity to subsequent exercise were investigated. Design Counterbalanced, randomised, crossover Methods Academy rugby players (n = 24) completed six 50-m sprints (five-min inter-set recovery) before occlusion cuff applica...
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Objectives: Rugby union is a high intensity intermittent sport, typically analysed via set time periods or rolling average methods. This study reports the demands of international rugby union via global positioning system (GPS) metrics expressed as mean ball in play (BiP), maximum BiP (max BiP), and whole match outputs. Design: Single cohort cro...
Article
Background: There is evidence linking women's T to competitive behaviours in sport and exercise. To advance this work, we examined the longitudinal relationships between salivary testosterone (sal-T) and competitiveness in athletic women who differ in training status. Methods: Elite (n = 9) and non-elite (n = 21) women athletes were monitored on...
Article
The effect of ischemic preconditioning (IPC) on swimming performance was examined. Using a randomized, crossover design, National-and International-level swimmers (n=20; 14 males, 6 females) participated in three trials (Con, IPC-2h, IPC-24h). Lower-body IPC (4 x 5 min bi-lateral blood-flow restriction at 160-228 mmHg, and 5 min reperfusion) was us...
Article
This study investigated salivary testosterone (sal-T) variation across the menstrual cycle in female athletes, at different competitive levels, and its association with motivation and neuromuscular power. Six elite and 16 non-elite female athletes were monitored on days 7 (D7), 14 (D14) and 21 (D21) across three menstrual cycles for basal sal-T con...
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Background Two common single nucleotide polymorphisms within the COL5A1 gene (SNPs; rs12722 C/T and rs3196378 C/A) have previously been associated with tendon and ligament pathologies. Given the high incidence of tendon and ligament injuries in elite rugby athletes, we hypothesised that both SNPs would be associated with career success. Results In...
Article
Despite the prevalence of caffeine as an ergogenic aid, few studies have examined the use of caffeinated gums, especially during half-time in team sports. The physiological (blood lactate, salivary hormone concentrations) and performance (repeated sprints, cognitive function) effects of consuming caffeine gum during a simulated half-time were exami...
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Objectives: To investigate the effect of oral contraceptive (OC) use on salivary testosterone (sal-T) concentrations and performance-related statistics in international field hockey matches. Design: A cohort observational study with repeated measures. Methods: Twenty-three elite female athletes were monitored across four international field ho...
Article
Objectives Evidence suggests that stress-induced changes in testosterone and cortisol are related to future competitive behaviours and team-sport outcomes. Therefore, we examined whether salivary testosterone and cortisol reactivity to a mid-week stress test can discriminate a match outcome in international rugby union competition. Design Single g...
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Objectives In thermoneutral conditions, half-time is associated with reductions in body temperature that acutely impair performance. This laboratory-based study compared active, passive, and combined methods of half-time heat maintenance. Design Randomised, counterbalanced, cross-over Methods After a standardised warm-up (WU) and 15 min of rest,...
Article
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Linear and multidirectional acceleration underpins success in professional soccer match-play. However, the physical qualities that determine these performance indicators are poorly understood in elite players. English Premier League players (n=26) performed isometric mid-thigh pulls (IMTP), bilateral and unilateral drop jumps (DJ; from 40 and 20 cm...
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This study examined the moderating effect of cortisol (C) on the relationship between testosterone (T) and hand-grip strength (HGS) in healthy young men. Sixty-five males were monitored for salivary T, C and HGS before and 15 min after a short bout (5 × 6-s trials) of sprint cycling exercise. Sprint exercise promoted (p < .05) positive changes in T...
Article
Resonant frequency training (RFT) is a heart rate variability (HRV) biofeedback technique where participants learn bespoke breathing patterns to inhibit autonomic nervous system changes resulting from stress. To demonstrate RFT in sport, we present an intervention case study with an elite female shooter that enabled her to perform optimally, even a...
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Background FTO gene variants have been associated with obesity phenotypes in sedentary and obese populations, but rarely with skeletal muscle and elite athlete phenotypes. Methods In 1089 participants, comprising 530 elite rugby athletes and 559 non-athletes, DNA was collected and genotyped for the FTO rs9939609 variant using real-time PCR. In a s...
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This study compared the movement demands of elite international Under-20 age grade (U20s) and senior international rugby union players during competitive tournament match play. Forty elite professional players from an U20 and 27 elite professional senior players from international performance squads were monitored using 10Hz global positioning syst...
Data
Table A. Supplementary Movement Characteristics for Senior and U20s, Forwards and Backs Groups. Data presented as Mean ± S.D Table B. Supplementary Movement Characteristics Presented by Playing Groups. FR = Front Row (Prop & Hooker), SR = Second Row, BR = Back Row, HB = Half Backs, MF = Midfield/Centres, B3 = Back Three (Wing & Fullback). Data pres...
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Objectives: Biochemical (e.g. creatine kinase (CK)) and neuromuscular (e.g. peak power output (PPO)) markers of recovery are expensive and require specialist equipment. Perceptual measures are an effective alternative, yet most validated scales are too long for daily use. Design: This study utilises a longitudinal multi-level design to test an a...
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Purpose: To examine the steroid hormone effect on the physical performance of young athletes during an Olympic weightlifting competition. Methods: 26 boys and 26 girls were monitored across 2 weightlifting competitions. Pre- and post-competition testosterone (T), cortisol (C) and dehydroepiandrosterone-sulphate (DHEA-s) were measured in blood, w...
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Support and management staff in elite sport experience work-related stress and emotional disturbance to a similar extent as athletes (Fletcher and Wagstaff 2009). The resonant frequency breathing technique (Lehrer et al. 2000) can inhibit autonomic changes associated with stressful situations or events and as such provides a potential emotional reg...
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Background The loads to which professional rugby players are subjected has been identified as a concern by coaches, players and administrators. In November 2014, World Rugby commissioned an expert group to identify the physical demands and non-physical load issues associated with participation in professional rugby. Objective To describe the curre...
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Background: Surgical training and practice is stressful, but adaptive changes in the stress circuitry (e.g. perceptual, physiological, hormonal, neural) could support skill development. This work examined skill acquisition and stress adaptations in novice surgeons during laparoscopic surgery (LS) training and detraining. Methods: Twelve medical...
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Objective: To address the rapid influence of testosterone (T) on neuromuscular performance, we compared the T and physical performance responses of adults exposed to a physical and psychological stimulus. Design: A group of healthy men (n=12) and women (n=14) each completed three treatments using a randomised, crossover design: exercise involvin...
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To advance our understanding of the hormonal contribution to athletic performance, we examined the temporal associations between individual changes in testosterone (T) and/or cortisol (C) concentrations, training motivation and physical performance in elite and non-elite trained men. Two male cohorts classified as elites (n = 12) and non-elites (n...
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In professional youth soccer players, the physiological, performance and perceptual effects of a single whole body cryotherapy (WBC) session performed shortly after repeated sprint exercise were investigated. In a randomized, counter-balanced and crossover design, 14 habituated English Premier League academy soccer players performed 15 x 30 m sprin...
Article
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The purpose of this study was to quantify movement demands of elite international age grade (U20) rugby union players during competitive tournament match play. Forty elite professional players from an U20 international performance squad were monitored using 10Hz global positioning systems (GPS) during 15 international tournament matches during the...
Article
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Purpose: The aim of this study was to compare the acute neuromuscular, biochemical, and endocrine responses of a training day consisting of a speed session only to performing a speed and weight training session on the same day Methods: Fifteen male academy level rugby players completed two protocols in a randomized order. The speed only protocol i...