as Liguori et al 4 reported that peak salivary caffeine concentration was faster and higher following coffee ingestion, compared with a caffeine capsule. However, Graham et al 5 concluded that only 4.5 mg·kg −1 of anhydrous caffeine increased exercise distance by 2 to 3 km when running at 85% V
Neil D. Clarke, Darren L. Richardson, James Thie and Richard Taylor
Robert W. Arnhold Jr. and Peter McGrain
The purpose of this study was to determine which set of selected kinematic variables affected the speed of visually impaired residential youth in the sprint run. The subjects were 27 students, 16 males and 11 females, between the ages of 9.4 and 16.4 years. Film data were collected during two trials of the 50-m dash. A Fortran computer program produced nine variables from these digitized data. A multiple regression analysis was performed on the variables using running speed as the dependent variable. Results of a correlation matrix yielded five variables with significant bivariate correlations to running speed. Results of a regression analysis indicated that the cycle length and hip joint range of motion had significant effects on running speed. Implications for an increase in sprinting speed include increasing stride length via the generation of greater hip extension during the drive phase and a greater hip flexion during the recovery phase of sprint running.
Marc Sim, Brian Dawson, Grant Landers, Debbie Trinder and Peter Peeling
The trace element iron plays a number of crucial physiological roles within the body. Despite its importance, iron deficiency remains a common problem among athletes. As an individual’s iron stores become depleted, it can affect their well-being and athletic capacity. Recently, altered iron metabolism in athletes has been attributed to postexercise increases in the iron regulatory hormone hepcidin, which has been reported to be upregulated by exercise-induced increases in the inflammatory cytokine interleukin-6. As such, when hepcidin levels are elevated, iron absorption and recycling may be compromised. To date, however, most studies have explored the acute postexercise hepcidin response, with limited research seeking to minimize/attenuate these increases. This review summarizes the current knowledge regarding the postexercise hepcidin response under a variety of exercise scenarios and highlights potential areas for future research—such as: a) the use of hormones though the female oral contraceptive pill to manipulate the postexercise hepcidin response, b) comparing the use of different exercise modes (e.g., cycling vs. running) on hepcidin regulation.
Darren J. Paul, Paul S. Bradley and George P. Nassis
Time-motion analysis is a valuable data-collection technique used to quantify the match running performance of elite soccer players. However, interpreting the reductions in running performance in the 2nd half or temporarily after the most intense period of games is highly complex, as it could be attributed to physical or mental fatigue, pacing strategies, contextual factors, or a combination of mutually inclusive factors. Given that research in this domain typically uses a reductionist approach whereby match running performance is examined in isolation without integrating other factors, this ultimately leads to a 1-dimensional insight into match performance. Subsequently, a cohesive review of influencing factors does not yet exist. The aim of this commentary is to provide a detailed insight into the complexity of match running performance and its most influential factors.
Jace A. Delaney, Heidi R. Thornton, Grant M. Duthie and Ben J. Dascombe
Rugby league coaches adopt replacement strategies for their interchange players to maximize running intensity; however, it is important to understand the factors that may influence match performance.
To assess the independent factors affecting running intensity sustained by interchange players during professional rugby league.
Global positioning system (GPS) data were collected from all interchanged players (starters and nonstarters) in a professional rugby league squad across 24 matches of a National Rugby League season. A multilevel mixed-model approach was employed to establish the effect of various technical (attacking and defensive involvements), temporal (bout duration, time in possession, etc), and situational (season phase, recovery cycle, etc) factors on the relative distance covered and average metabolic power (Pmet) during competition. Significant effects were standardized using correlation coefficients, and the likelihood of the effect was described using magnitude-based inferences.
Superior intermittent running ability resulted in very likely large increases in both relative distance and Pmet. As the length of a bout increased, both measures of running intensity exhibited a small decrease. There were at least likely small increases in running intensity for matches played after short recovery cycles and against strong opposition. During a bout, the number of collision-based involvements increased running intensity, whereas time in possession and ball time out of play decreased demands.
These data demonstrate a complex interaction of individual- and match-based factors that require consideration when developing interchange strategies, and the manipulation of training loads during shorter recovery periods and against stronger opponents may be beneficial.
Hassane Zouhal, Abderraouf Ben Abderrahman, Jacques Prioux, Beat Knechtle, Lotfi Bouguerra, Wiem Kebsi and Timothy D. Noakes
To determine the effect of drafting on running time, physiological response, and rating of perceived exertion (RPE) during 3000-m track running.
Ten elite middle- and long-distance runners performed 3 track-running sessions. The 1st session determined maximal oxygen uptake and maximal aerobic speed using a lightweight ambulatory respiratory gasexchange system (K4B2). The 2nd and the 3rd tests consisted of nondrafting 3000-m running (3000-mND) and 3000-m running with drafting for the 1st 2000 m (3000-mD) performed on the track in a randomized counterbalanced order.
Performance during the 3000-mND (553.59 ± 22.15 s) was significantly slower (P < .05) than during the 3000-mD (544.74 ± 18.72 s). Cardiorespiratory responses were not significantly different between the trials. However, blood lactate concentration was significantly higher (P < .05) after the 3000-mND (16.4 ± 2.3 mmol/L) than after the 3000-mD (13.2 ± 5.6 mmol/L). Athletes perceived the 3000-mND as more strenuous than the 3000-mD (P < .05) (RPE = 16.1 ± 0.8 vs 13.1 ± 1.3). Results demonstrate that drafting has a significant effect on performance in highly trained runners.
This effect could not be explained by a reduced energy expenditure or cardiorespiratory effort as a result of drafting. This raises the possibility that drafting may aid running performance by both physiological and nonphysiological (ie, psychological) effects.
Rich D. Johnston, Tim J. Gabbett and David G. Jenkins
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.
Eighteen semiprofessional rugby league players (age 23.6 ± 2.8 y) competed in 3 off-side small-sided games (2 × 10-min halves) with a contact bout performed every 2 min. The rules of each game were identical except for the number of contact efforts performed in each bout. Players performed 1, 2, or 3 × 5-s wrestles in the single-, double-, and triple-contact game, respectively. The movement demands (including distance covered and intensity of exercise) in each game were monitored using global positioning system units. Bench-press and back-squat 1-repetition maximum and the 30−15 Intermittent Fitness Test (30−15IFT) assessed muscle strength and high-intensity-running ability, respectively.
There was little change in distance covered during the single-contact game (ES = −0.16 to −0.61), whereas there were larger reductions in the double- (ES = −0.52 to −0.81) and triple-contact (ES = −0.50 to −1.15) games. Significant relationships (P < .05) were observed between 30–15IFT and high-speed running during the single- (r = .72) and double- (r = .75), but not triple-contact (r = .20) game.
There is little change in running intensity when only single contacts are performed each bout; however, when multiple contacts are performed, greater reductions in running intensity result. In addition, high-intensity-running ability is only associated with running performance when contact demands are low.
James C. Brown, Caron-Jayne Miller, Michael Posthumus, Martin P. Schwellnus and Malcolm Collins
Endurance running performance is a multifactorial phenotype that is strongly associated with running economy. Sit and reach range of motion (SR ROM) is negatively associated with running economy, suggesting that reduced SR ROM is advantageous for endurance running performance. The COL5A1 gene has been associated with both endurance running performance and SR ROM in separate cohorts. The aim of this study was to investigate whether COL5A1 is associated with ultra-marathon running performance and whether this relationship could be partly explained by prerace SR ROM.
Seventy-two runners (52 male, 20 female) were recruited from the 56 km Two Oceans ultra-marathon and were assessed for prerace SR ROM. The cohort was genotyped for the COL5A1 BsfUI restriction fragment length polymorphism, and race times were collected after the event.
Participants with a TT genotype (341 ± 41 min, N = 21) completed the 56 km Two Oceans ultra-marathon significantly (P = 0.014) faster than participants with TC and CC genotypes (365 ± 39 min, N = 50). The COL5A1 genotype and age accounted for 19% of performance variance. When the cohort was divided into performance and flexibility quadrants, the T allele was significantly (P = 0.044) over-represented within the fast and inflexible quadrant.
The COL5A1 genotype was found to be significantly associated with performance in a 56 km ultra-endurance run. This study confirms previous findings and it furthers our understanding of the relationships among ROM, COL5A1, and endurance running performance. We continue to speculate that the COL5A1 gene alters muscle-tendon stiffness.
Charilaos Papadopoulos, J. Andrew Doyle and Brian D. LaBudde
The purpose of this study was to determine the relationship between various lactate-threshold (LT) definitions and the average running velocity during a 10-km and a 21.1-km time trial (TT).
Thirteen well-trained runners completed an incremental maximal exercise test, a 10-km TT, and a 21.1-km TT on a motorized treadmill. Blood samples were collected through a venous catheter placed in an antecubital vein. Pearson's correlation coefficients were used to determine the relationship between the running velocity at the different LT definitions and the average running velocity during each TT. A dependent t test was used to determine statistical differences for the mean lactate response between the 2 running distances.
The LTDmax, the point on the regression curve that yielded the maximal perpendicular distance to the straight line formed by the 2 endpoints, was the LT definition with the highest correlation for both 10-km (r = .844) and 21.1-km TTs (r = .783). The velocity at the LTDmax was not, however, the velocity closest to the performance velocity for either distance. The mean running velocity at each LT was significantly different and tended to overestimate the mean TT performance velocities. The mean lactate concentration during the 10-km TT (3.52 ± 1.58 mmol) was significantly higher than during the 21.1-km TT (1.86 ± 0.90 mmol).
These results indicate that a single LT point cannot be reliably associated with different running distances. Furthermore, these data suggest that a different methodology for estimating the LT that considers individual responses might be required for different running distances.
Tyler J. Noble and Robert F. Chapman
differences between African and non-African distance runners, research into the impact of these differences on running performance has produced mixed results. Furthermore, the variance in performance between Africans and non-Africans is not likely to be explained by differences in energetics but, rather, by