David G Jenkins's research while affiliated with The University of Queensland and other places

Publications (160)

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Background: Androgen deprivation therapy (ADT) in prostate cancer has been shown to deteriorate body composition (reduced lean mass and increased body and fat mass) and increase the risk of cardiovascular morbidity. The Mediterranean style dietary pattern (MED-diet) and high intensity interval training (HIIT) may synergistically alleviate these sid...
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The aim of the present study was to examine the effects of creatine (Cr) supplementation on power output during repeated sprints on a non-motorized treadmill. Sixteen recreationally active males volunteered for this study (age 25.5 ± 4.8 y, height 179 ± 5 cm, body mass 74.8 ± 6.8 kg). All participants received placebo supplementation (75 mg of gluc...
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Objectives To examine potential changes in mental and physical fatigue across an elite netball pre-season training phase and relationships between mental fatigue, physical fatigue, salivary cortisol (sCort) and alpha-amylase (sAA). Design Observational with repeated measures. Methods Across a 16-week pre-season, 10 elite female netballers (25.3 ±...
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Purpose: Mental fatigue is emerging as an important consideration for elite sporting performance, yet it is rarely monitored. The present study assessed changes in mental fatigue in professional team-sport athletes across 2 seasons and examined the relationship between mental fatigue and other athlete self-report measures of well-being. Methods:...
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Mental fatigue has been shown to negatively influence physical, technical and tactical aspects of sporting performance. However, mental fatigue is not routinely monitored or managed in elite sport and it is not clear whether mental fatigue occurs and/or changes across the varied contextual demands experienced by elite athletes in training, preparat...
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Holmberg, PM, Gorman, AD, Jenkins, DG, and Kelly, VG. Lower-body aquatic training prescription for athletes. J Strength Cond Res XX(X): 000-000, 2021-Traditionally prescribed to manage various medical ailments and promote healing, aquatic immersion may provide a favorable environment to undertake preparatory training tasks given its profound biolog...
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Professional rugby league (RL) football is a contact sport involving repeated collisions and high-intensity efforts; both training and competition involve high energy expenditure. The present review summarizes and critiques the available literature relating the physiological demands of RL to nutritional requirements and considers potential ergogeni...
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The efficacy of high-intensity interval training (HIIT) to elicit physiological and performance adaptations in endurance athletes has been established in men and to a lesser extent in women. This study compared lactate threshold (LT2) and performance adaptations to HIIT between men and women. Nine male and eight female cyclists and triathletes comp...
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Purpose: To examine potential differences in internal and external workload variables between playing positions and between training drills and games within an elite netball team during training and competition. Methods: Nine elite female netballers were monitored during 15 games and all training sessions over 28 weeks. Workload variables assess...
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Purpose: To determine the efficacy of 20 minutes of external counterpulsation (ECP) on subsequent 1.2-km shuttle run test (1.2SRT) performance and perceived recovery following fatiguing high-intensity exercise. Methods: After familiarization, 13 recreationally active males (21.4 [1.9] y) participated in 2 experimental trials in a randomized cros...
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Purpose: To examine relationships between external- and internal-workload variables in an elite female netball team, with consideration of positional differences. Methods: Nine elite female netball athletes had their weekly workloads monitored across their preseason and competition phases of a season. Internal workload was determined using summa...
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Background Cancer-related fatigue (CRF) is a prevalent and persistent symptom from androgen deprivation therapy (ADT) in prostate cancer. The Mediterranean-style dietary pattern (MED-diet) offers a plausible mechanism to mitigate CRF through reducing inflammation and improving body composition. This study aimed to evaluate the effects of a 12-week...
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Purpose: The aim of this study was to map responses over 32 hours following high-load (HL) and moderate-load (ML) half-squat priming. Methods: Fifteen participants completed control, HL (87% 1RM), and ML (65% 1RM) activities in randomized, counterbalanced order. Countermovement jump (CMJ), squat jump (SJ), saliva testosterone, saliva cortisol, a...
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Objectives: To assess the magnitude of changes in, and relationships between, physical and mental fatigue pre-to-post match in elite development netballers. Design: Observational. Methods: Twelve female netballers (21.3±2.9 years) competing in the Australian Netball League reported perceptual measures of mental and physical fatigue pre- and po...
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Recent scientific evidence supports the use of a low-volume strength–power ‘resistance priming’ session prior to sporting competition in an effort to enhance neuromuscular performance. Though research evidence relating to this strategy is presently limited, it has been shown to be effective in improving various measures of neuromuscular performance...
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Purpose: To examine relationships among physical performance, workload, and injury risk in professional rugby league players. Methods: Maximal-effort (n = 112) and submaximal (n = 1084) running performances of 45 players were recorded from 1 club over 2 consecutive seasons. Poorer and better submaximal running performance was determined by highe...
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Objectives: Recent research has revealed that low volume resistance 'priming' exercise may improve neuromuscular performance when completed within 48h before competition. The aim of this study was to investigate the current prevalence and application of this strategy by practitioners in sport. Design: This study surveyed practitioners who were c...
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The perceptions of high-performance swimming coaches regarding the relative contribution of the upper and lower limbs are crucial in optimising athletic performance through subsequent prescription of training. Problematically, examination of these perspectives is lacking. To develop knowledge in this area, perceptions regarding the upper and lower...
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Background: Despite an overwhelming body of evidence showing the benefits of physical activity (PA) and exercise for cancer survivors, few survivors meet the exercise oncology guidelines. Moreover, initiating, let alone maintaining exercise programs with cancer survivors continues to have limited success. The aim of this trial is to evaluate the i...
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Purpose: Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity shown to negatively influence physical performance. Variation exists across the literature regarding the manifestations and impact of mental fatigue; with little knowledge of the domain-specific manifestations in elite sport. The difficu...
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Purpose: Physical activity is associated with significant reductions in colorectal cancer mortality. However, the mechanisms by which exercise mediates this antioncogenic effect are not clear. Methods: Colorectal cancer survivors completed acute (n = 10) or chronic (n = 10) exercise regimes. An acute high intensity interval exercise session (HII...
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Physical profile data from elite, sub-elite, regional, under 21s (U21), under 19s (U19) and under 17s (U17) (n = 845) players from a state netball association in Australia were analysed. Within season changes were examined for the elite and sub-elite players. Longitudinal changes were examined for the elite across four consecutive netball seasons....
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Objectives: Mental fatigue resulting from prolonged periods of demanding cognitive activity, has been found to impair endurance exercise performance and performance in some sport-specific tasks. The application of such research to the elite sporting environment however is limited. Design & Methods: This article reviews the literature relevant to me...
Presentation
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This presentation covered a component of my final study within my PhD. The overall theme of the thesis was to determine the roles of the upper- and lower-limbs in velocity production and their contribution to the metabolic cost. This study used a statistical, whole-body approach rather than a comparative approach (comparing arms-only, legs-only and...
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Hoffmann, SM, Skinner, TL, van Rosendal, SP, Osborne, MA, Emmerton, LM, and Jenkins, DG. The efficacy of the lactate threshold: A sex-based comparison. J Strength Cond Res XX(X): 000-000, 2018-The second lactate threshold (LT2) has previously been associated with endurance performance; however, comparisons between sexes are lacking regarding its ef...
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Objectives: We examined: (1) relationships among sub-maximal heart rate (sub-maxHR) following 4 minutes of the Yo-Yo intermittent recovery test level 1 (IR1) and maximal-effort performance (distance covered at volitional exhaustion), (2) test re-test reliability of sub-maxHR, and (3) whether changes in maximal-effort Yo-Yo performance are related w...
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Purpose: Determine: 1) how change of direction (COD) workloads influence PlayerLoad variables when controlling total distance covered, and 2) relationships among collision workloads and PlayerLoad variables during rugby league match-play. Methods: Participants completed 3 protocols (crossover design) consisting of 10 repetitions of a 60 m effort...
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This study examined the changes in running performance, maximal blood lactate concentrations and running kinematics between 85%BM anti-gravity (AG) running and normal over-ground (OG) running over an 8-week training period. Fifteen elite male developmental cricketers were assigned to either the AG or over-ground (CON) running group. The AG group (n...
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Introduction Deteriorations in cardiorespiratory fitness (V̇O2peak) and body composition are associated with poor prognosis following colorectal cancer treatment. However, the optimal intensity and frequency of aerobic exercise training to improve these outcomes in colorectal cancer survivors is unknown. Methods This trial compared eight weeks of...
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Purpose: Menstruation and menstrual symptoms are commonly-cited barriers to physical activity in women. The delay or avoidance of menstruation through extended oral contraceptive regimens may mitigate these barriers, yet information on menstrual manipulation practices in young physically-active women is sparse. The objective of this study was to i...
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Objectives: Collision frequency during rugby league matches is associated with team success, greater and longer lasting fatigue and increased injury risk. This study researched the sensitivity and specificity of microtechnology to count collision events during rugby league matches. Design: Diagnostic accuracy study. Methods: While wearing a mi...
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Purpose: The contributions of the limbs to velocity and metabolic parameters in front-crawl swimming at different intensities have not been identified with the consideration of both stroke and kick rate. Consequently, velocity, oxygen uptake (V̇O2) and metabolic cost of swimming with the whole body (swim), the upper-limbs only (pull) and lower-lim...
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Purpose: Oral contraceptive (OC) use reduces peak aerobic capacity (V˙O2peak), however, whether it also influences adaptations to training has yet to be determined. This study aimed to examine the influence of OC use on peak performance [peak power output (PPO)] and physiological adaptations [V˙O2peak and peak cardiac output (Q˙peak)] following sp...
Presentation
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Aim: Previous studies aiming to identify the contributions of the upper and lower limbs to freestyle swimming velocity have disregarded the influence of the stroke rate and kick rate. This study aimed to determine the relative importance of biomechanical parameters (stroke and kick rate) and individual characteristics (200 m freestyle personal best...
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Objectives: Fluctuating endogenous and exogenous ovarian hormones may influence exercise parameters; yet control and verification of ovarian hormone status is rarely reported and limits current exercise science and sports medicine research. The purpose of this study was to determine the effectiveness of an individualised three-step method in ident...
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Following exercise-induced muscle damage (EIMD), masters athletes take longer to recover than younger athletes. The purpose of this study was to determine the effect of higher than recommended post-exercise protein feedings on the recovery of knee extensor peak isometric torque (PIT), perceptions of recovery, and cycling time trial (TT) performance...
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Purpose Following colorectal cancer diagnosis and anti-cancer therapy, declines in cardiorespiratory fitness and body composition lead to significant increases in morbidity and mortality. There is increasing interest within the field of exercise oncology surrounding potential strategies to remediate these adverse outcomes. This study compared 4 wee...
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Objectives: To investigate β-alanine supplementation use and level of knowledge amongst professional footballers. Design: Cross-sectional survey of Australian professional football players. Methods: Questionnaires assessing β-alanine supplementation behaviours, level of knowledge and sources of information were completed by professional rugby...
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Purpose: Stroke rate (SR) has not been considered in previous research examining the relative roles of the limbs in front-crawl performance. This study compared velocity, aerobic power ([Formula: see text]) and metabolic cost (C) between whole body (WB) and arms only (AO) front-crawl swimming across various intensities while controlling SR. Metho...
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Purpose: The objective of this study is to compare the integrated muscle protein synthesis (MPS) rates of masters and younger triathletes over three consecutive days of intense endurance training. Recovery of cycling performance, after muscle-damaging running, was also compared between groups. Methods: Five masters (age, 53 ± 2 yr; V˙O2max, 55.7...
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Exercise and physical activity have been shown to reduce the risk of many common cancers and strongly influence tumor biology. A cause-effect mechanism explaining this relationship is dependent on cellular pathways that can influence tumor growth and are exercise responsive. The insulin-like growth factor (IGF) axis is reported to promote the devel...
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Post-exercise nutrition is a critical component of an athlete’s recovery from training and competition. However, little is known about athletes’ post-exercise dietary practices or knowledge of dietary recommendations, particularly among masters athletes. The purpose of this study was to compare and contrast the knowledge of post-exercise nutritiona...
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The aims of this study were to describe normative values and seasonal variation of body composition in female cyclists comparing female road and track endurance cyclists, and to validate the use of anthropometry to monitor lean mass changes. Anthropometric profiles (seven site skinfolds) were measured over 16 years from 126 female cyclists. Lean ma...
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Participation rates of masters athletes in endurance events such as long distance triathlon and running continue to increase. Given the physical and metabolic demands of endurance training, recovery practices influence the quality of successive training sessions, and consequently, adaptations to training. Following muscle-damaging endurance exercis...
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To assess the impact of different repeated high-intensity effort (RHIE) bouts on player activity profiles, skill involvements and neuromuscular fatigue during small-sided games. Twenty-two semi-professional rugby league players (age 24.0 ± 1.8 years; body mass 95.6 ± 7.4 kg) participated in this study. During 4 testing sessions, players performed R...
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Regular exercise has been recommended as a potential strategy to counteract the age-related bone loss experienced by men; however, the optimal exercise prescription is not known. To perform a pilot study to examine the osteogenic effect, safety and feasibility of a combined program of upper body resistance exercise and two doses of impact-loading e...
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The aim of this study was to determine whether the fatigue responses to the same intensified rugby league competition differed depending on playing standard and physical fitness. Players from a high-standard (n = 15) and a low-standard (n = 16) junior rugby league team had lower body neuromuscular fatigue, perceptual wellbeing, and blood creatine k...
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To examine whether a calcium-rich pre-exercise meal attenuates exercise-induced perturbations of bone calcium homeostasis caused by maintenance of sweat calcium losses. Using a randomized, counterbalanced crossover design, 32 well-trained female cyclists completed two 90 min cycling trials separated by 1 day. Exercise trials were preceded 2 hours b...
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To assess the influence of playing standard and physical fitness on pacing strategies during a junior team sport tournament. A between-group, repeated measures design was used. Twenty-eight junior team sport players (age 16.6 ± 0.5 years; body mass 79.9 ± 12.0 kg) from a high-standard and low-standard team, participated in a junior rugby league tou...
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The use of 3 or more efforts (running and contact), separated by short recovery periods, is widely used to define a 'repeated high-intensity effort' (RHIE) bout in rugby league. It has been suggested that due to fatigue, players become less effective following RHIE bouts; however, there is little evidence to support this. This study determined if p...
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Purpose: This study investigated the satisfaction of elite female cyclists with their body weight (BW) in the context of race performance, the magnitude of BW manipulation, and the association of these variables with menstrual function. Methods: Female competitors in the Australian National Road Cycling Championships (n = 32) and the Oceania Cha...
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The majority of lightweight rowers undertake acute weight loss prior to competition. Given the competitive advantage afforded to larger, more muscular rowers over their smaller counterparts, the use of moderate, acute weight loss may be justified, at least among larger, leaner athletes who struggle to achieve the specified body mass requirement and...
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Physical activity (PA) is related to colorectal cancer (CRC) mortality, with approximately 15% of CRC deaths worldwide attributable to physical inactivity. Moreover, higher levels of PA in CRC survivors have been associated with a reduced risk of the disease recurring. Despite the recognised nexus between PA and the risk of CRC, the physiological m...
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Some athletes avoid dairy in the meal consumed before exercise due to fears about gastrointestinal discomfort. Regular exclusion of dairy foods may unnecessarily reduce intake of high quality proteins and calcium with possible implications for body composition and bone health. This study compared the effects of meals that included (Dairy) or exclud...
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Purpose: To determine the influence the number of contact efforts during a single bout has on running intensity during game-based activities and assess relationships between physical qualities and distances covered in each game. Methods: Eighteen semiprofessional rugby league players (age 23.6 ± 2.8 y) competed in 3 off-side small-sided games (2...
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Rugby league is a team sport in which players engage in repeated high-intensity exercise involving frequent collisions. Recent research, much of which has involved global positioning system (GPS) technology, has provided coaches and sport scientists with a deeper understanding of match demands, particularly at the elite level. This has allowed for...
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Objectives This study examined the influence of physical qualities on markers of fatigue and muscle damage following rugby league match-play. Design Between subjects design. Methods Twenty-one male youth rugby league players (age 19.2 ± 0.7 years; height 180.7 ± 5.6 cm; body mass 89.9 ± 10.0 kg) participated in the study. Yo-Yo intermittent recov...
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Repeated-sprinting incorporating tackles leads to greater reductions in sprint performance compared with repeated-sprinting alone. However, the influence of physical contact on the running demands of game-based activities is unknown. The aim of this study was to determine whether the addition of physical contact altered pacing strategies during gam...
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Physical contact is frequent in rugby league competition and is thought to be a major contributor to the fatigue and creatine kinase (CK) response, although direct evidence is lacking. The aim of this study was to investigate the influence that physical contact had on the fatigue and CK response to small-sided games. Cross-over, counter-balanced st...