Effect of Menstrual Cycle Phase and Hormonal Contraceptives on Resting Metabolic Rate and Body Composition.

The cyclical changes in sex hormones across the menstrual cycle (MC) are associated with various biological changes that may alter resting metabolic rate (RMR) and body composition estimates. Hormonal contraceptive (HC) use must also be considered given their impact on endogenous sex hormone concentrations and synchronous exogenous profiles. The purpose of this study was to determine if RMR and dual-energy X-ray absorptiometry body composition estimates change across the MC and differ compared with HC users. This was accomplished during a 5-week training camp involving naturally cycling athletes (n = 11) and HC users (n = 7 subdermal progestin implant, n = 4 combined monophasic oral contraceptive pill, n = 1 injection) from the National Rugby League Indigenous Women's Academy. MC phase was retrospectively confirmed via serum estradiol and progesterone concentrations and a positive ovulation test. HC users had serum estradiol and progesterone concentrations assessed at the time point of testing. Results were analyzed using general linear mixed model. There was no effect of MC phase on absolute RMR (p = .877), relative RMR (p = .957), or dual-energy X-ray absorptiometry body composition estimates (p > .05). There was no effect of HC use on absolute RMR (p = .069), relative RMR (p = .679), or fat mass estimates (p = .766), but HC users had a greater fat-free mass and lean body mass than naturally cycling athletes (p = .028). Our findings suggest that RMR and dual-energy X-ray absorptiometry body composition estimates do not significantly differ due to changes in sex hormones in a group of athletes, and measurements can be compared between MC phases or with HC usage without variations in sex hormones causing additional noise.

Field- and Laboratory-derived Power-Cadence Profiles in World-Class and Elite Track Sprint Cyclists.

Previous investigations comparing Torque-Cadence (T-C) and Power-Cadence (P-C) profiles derived from seated and standing positions and field and laboratory conditions are not congruent with current methodological recommendations. Consequently, the aim of this investigation was to compare seated and standing T-C and P-C profiles generated from field and laboratory testing. Thirteen world-class and elite track sprint cyclists (n = 7 males, maximal power output (Pmax) = 2112 ± 395 W; n = 6 females, Pmax = 1223 ± 102 W) completed two testing sessions in which field- and laboratory-derived T-C and P-C profiles were identified. Standing P-C profiles had significantly (p < 0.05) greater Pmax than seated profiles, however there were no significant differences in optimal cadence (Fopt) between seated and standing positions. Pmax and Fopt were significantly lower in field-derived profiles in both positions compared to laboratory-derived profiles. However, there was no significant difference in the goodness-of-fit (R2) of the P-C profiles between laboratory (0.985 ± 0.02) and field-testing (0.982 ± 0.02) in each position. Valid T-C and P-C profiles can be constructed from field and laboratory protocols; however, the mechanical variables derived from the seated and standing and field and laboratory profiles cannot be used interchangeably. Both field and laboratory-derived profiles provide meaningful information and provide complementary insights into cyclists' capacity to produce power output.

The influence of cadence on fatigue during maximal sprint cycling in world-class and elite sprint cyclists.

Optimising cadence through appropriate gear selection is a key consideration for track sprint cycling performance, yet the influence of cadence on fatigue (i.e., decrement in power output) within a maximal sprint is not well understood. The aim of this study was to identify the influence of cadence on fatigue during maximal sprint cycling. Eleven world-class and elite track sprint cyclists (n = 6 men, maximal power output (Pmax) = 1894 ± 351 W, optimal cadence (Fopt) = 134 ± 8 rev∙min-1: n = 5 women, Pmax = 1114 ± 80 W, Fopt = 124 ± 8 rev∙min-1) completed two testing sessions where power-cadence profiles were constructed to determine the Fopt associated with Pmax. Cyclists also performed three maximal 15-s sprints (Fopt, ±15%Fopt) to identify fatigue per pedal stroke across these cadence ranges. There was no significant difference (p = 0.2) in the absolute fatigue per pedal stroke when cadence was fixed 15% above (16.7 ± 6.1 W∙stroke-1) and below (15.3 ± 5.1 W∙stroke-1) Fopt. Similarly, there was no significant difference in the relative fatigue per pedal stroke (% peak power∙stroke-1) across Fopt and ± 15%Fopt trials (p = 0.12). The relative decrement in power output is equivalent across the ± 15%Fopt cadence range. As such, a higher-geared, lower-cadence approach to maximal sprint cycling could be a viable method to minimise maximal pedal strokes and reduce the decrement in power output.

Behind enemy lines: Expressing locomotor movements of athletes in the National Rugby League Women's (NRLW) competition relative to opposition data.

We provide a novel analysis of the locomotor movements of athletes in the National Rugby League Women's (NRLW) competition by presenting the data of opposing teams expressed as a relative (%) difference and explore the association with match outcome. 117 rugby league athletes from the four NRLW clubs participated in this study. Mean speed (m·min-1), mean high-speed running (>12 km·h-1; m·min-1), and mean acceleration (m·s-2) were measured in 12 matches (370 individual match files) using the Global Navigation Satellite System (GNSS). Individual GNSS-derived data from each match-half were summed across each team and the association with total points and the points differential in each match-half was determined using linear mixed models. Greater high-speed running and lower mean acceleration were associated with more points being scored. A greater relative difference in mean high-speed running between competing teams was associated with a higher points differential. That is, if a team completed 10% more high-speed running than their opposition, they were likely to score an average of 3.2 points more during a given match-half. This unique analysis of GNSS-derived data may assist coaches and performance support staff to interpret the locomotor movements of female rugby league players with the appropriate considerations for the opposition team.

Blood oxidative stress biomarkers in women: influence of oral contraception, exercise, and N-acetylcysteine.

PURPOSE: To compare physiological responses to submaximal cycling and sprint cycling performance in women using oral contraceptives (WomenOC) and naturally cycling women (WomenNC) and to determine whether N-acetylcysteine (NAC) supplementation mediates these responses. METHODS: Twenty recreationally trained women completed five exercise trials (i.e., an incremental cycling test, a familiarisation trial, a baseline performance trial and two double-blind crossover intervention trials). During the intervention trials participants supplemented with NAC or a placebo 1 h before exercise. Cardiopulmonary parameters and blood biochemistry were assessed during 40 min of fixed-intensity cycling at 105% of gas-exchange threshold and after 1-km cycling time-trial. RESULTS: WomenOC had higher ventilation (ß [95% CI] = 0.07 L·min-1 [0.01, 0.14]), malondialdehydes (ß = 12.00 mmol·L-1 [6.82, 17.17]) and C-reactive protein (1.53 mg·L-1 [0.76, 2.30]), whereas glutathione peroxidase was lower (ß =  22.62 mU·mL-1 [- 41.32, - 3.91]) compared to WomenNC during fixed-intensity cycling. Plasma thiols were higher at all timepoints after NAC ingestion compared to placebo, irrespective of group (all p < 0.001; d = 1.45 to 2.34). For WomenNC but not WomenOC, the exercise-induced increase in malondialdehyde observed in the placebo trial was blunted after NAC ingestion, with lower values at 40 min (p = 0.018; d = 0.73). NAC did not affect cycling time-trial performance. CONCLUSIONS: Blood biomarkers relating to oxidative stress and inflammation are elevated in WomenOC during exercise. There may be an increased strain on the endogenous antioxidant system during exercise, since NAC supplementation in WomenOC did not dampen the exercise-induced increase in malondialdehyde. Future investigations should explore the impact of elevated oxidative stress on exercise adaptations or recovery from exercise in WomenOC.

Injury risk factors and barriers to their mitigation for women playing rugby league: a Delphi study.

This study aimed to 1) develop a consensus (≥70% agreement between experts) on injury risk factors specific to women playing rugby league, 2) establish the importance of the identified injury risk factors and the feasibility of mitigating these risk factors and 3) establish context specific barriers to injury risk management. Aim 1: A Delphi panel, consisting of 12 experts in rugby league and injury (e.g., physiotherapists, research scientists) were asked to identify injury risk factors specific to women playing rugby league. Aim 2: seven coaches of women's rugby league teams were asked to rate each risk factor that achieved consensus by their importance and feasibility to manage. Aim 3: Coaches reported barriers which restrict injury risk factor mitigation. Of the 53 injury risk factors which achieved consensus, the five injury risk factors with the highest combination of importance and feasibility ratings were: "poor tackle technique", "a lack of pre-season intensity", "training session are too short", "the current medical standards", and "limited access to physiotherapists". Following the identification of injury risk factors, their feasibility to manage and context specific barriers, this study proposes three constraint driven, integrated solutions which may reduce the barriers which limit injury risk factor management.

The Validity of Automated Tackle Detection in Women's Rugby League.

ABSTRACT: Cummins, C, Charlton, G, Naughton, M, Jones, B, Minahan, C, and Murphy, A. The validity of automated tackle detection in women's rugby league. J Strength Cond Res 36(7): 1951-1955, 2022-This study assessed the validity of microtechnology devices to automatically detect and differentiate tackles in elite women's rugby league match-play. Elite female players (n = 17) wore a microtechnology device (OptimEye S5 device; Catapult Group International) during a representative match, which involved a total of 512 tackles of which 365 were defensive and 147 were attacking. Tackles automatically detected by Catapult's tackle detection algorithm and video-coded tackles were time synchronized. True positive, false negative and false positive events were utilized to calculate sensitivity (i.e., when a tackle occurred, did the algorithm correctly detect this event) and precision (i.e., when the algorithm reported a tackle, was this a true event based on video-coding). Of the 512 video-derived attacking and defensive tackle events, the algorithm was able to detect 389 tackles. The algorithm also produced 81 false positives and 123 false negatives. As such when a tackle occurred, the algorithm correctly identified 76.0% of these events. When the algorithm reported that a tackle occurred, this was an actual event in 82.8% of circumstances. Across all players, the algorithm was more sensitive to the detection of an attacking event (sensitivity: 78.2%) as opposed to a defensive event (sensitivity: 75.1%). The sensitivity and precision of the algorithm was higher for forwards (sensitivity: 81.8%; precision: 92.1%) when compared with backs (sensitivity: 64.5%; precision: 66.1%). Given that understanding the tackle demands of rugby league is imperative from both an injury-prevention and physical-conditioning perspective there is an opportunity to develop a specific algorithm for the detection of tackles within women's rugby league.

Time to Be Negative About Acceleration: A Spotlight on Female Football Players.

ABSTRACT: Griffin, J, Horan, S, Keogh, J, Andreatta, M, and Minahan, C. Time to be negative about acceleration: A spotlight on female football players. J Strength Cond Res 36(11): 3264-3271, 2022-Women's football requires players to perform frequent changes in velocity (i.e., speed and direction) for successful performance. Although increases in velocity ("acceleration") are important, decreases in velocity ("deceleration") should also be considered equally important to performance and load monitoring. Currently, there is a disproportionate focus on acceleration and creating faster players. The aim of this review is to provide an understanding of deceleration for female football players. Given the limited research in this area, data from studies involving male football players and from other team-sport athletes were used to supplement the review where necessary. Most research focused on eccentric strength and its relationship with deceleration ability, highlighting the importance of slow eccentric strength of the quadriceps and hamstrings to deceleration. Technical and kinematic characteristics of deceleration were also investigated. Importantly, with deceleration being a unilateral motor skill, development requires similar amounts of training for both legs. Imbalances between legs in skill and strength characteristics may compromise performance or increase the risk of injury. Given the dependent nature of deceleration, several contextual factors were identified as important when considering deceleration as a part of training programs and performance. Deceleration is affected by the following factors: an athlete's momentum, the approach speed, change of direction angle, time or distance, anticipated or unanticipated task, fatigue, and the positional requirements of female football players. Further research is needed into deceleration and the physical characteristics associated with deceleration performance, particularly for female football players.

Determinants of last lap speed in paced and maximal 1500-m time trials.

PURPOSE: The present study identified the physiological and performance characteristics that are deterministic during a maximal 1500-m time trial and in paced 1500-m time trials, with an all-out last lap. METHODS: Thirty-two trained middle-distance runners (n = 21 male, VO2peak: 72.1 ± 3.2; n = 11, female, VO2peak: 61.2 ± 3.7 mL kg-1 min-1) completed a 1500-m time trial in the fastest time possible (1500FAST) as well as a 1500MOD and 1500SLOW trial whereby mean speed was reduced during the 0-1100 m by 5% and 10%, respectively. Anaerobic speed reserve (ASR), running economy (RE), the velocity corresponding with VO2peak (VVO2peak), maximal sprint speed (MSS) and maximal accumulated oxygen deficit (MAOD) were determined during additional testing. Carnosine content was quantified by proton magnetic resonance spectroscopy in the gastrocnemius and expressed as a Z-score to estimate muscle fibre typology. RESULTS: 1500FAST time was best explained by RE and VVO2peak in female runners (adjusted r2 = 0.80, P < 0.001), in addition to the 0-1100-m speed relative to VVO2peak in male runners (adjusted r2 = 0.72, P < 0.001). Runners with a higher gastrocnemius carnosine Z-score (i.e., higher estimated percentage of type II fibres) and greater MAOD, reduced their last lap time to a greater extent in the paced 1500-m trials. Neither ASR nor MSS was associated with last lap time in the paced trials. CONCLUSION: These findings suggest that VVO2 peak and RE are key determinants of 1500-m running performance with a sustained pace from the start, while a higher carnosine Z-score and MAOD are more important for last lap speed in tactical 1500-m races.

Temporal changes in blood oxidative stress biomarkers across the menstrual cycle and with oral contraceptive use in active women.

PURPOSE: To examine the temporal changes in blood oxidative stress biomarkers in recreationally-trained women that were naturally-cycling (WomenNC) or using oral contraceptives (WomenOC) across one month. METHODS: Blood samples were acquired at three timepoints of the menstrual cycle (1: early-follicular, 2: late-follicular and 3: mid-luteal) and oral contraceptive packet (1: InactiveOC, 2: Mid-activeOC and 3: Late-activeOC) for determination of estradiol, progesterone, oxidative stress, C-reactive protein (CRP) and other cardiometabolic biomarkers in plasma and serum. RESULTS: There was a Group by Time effect on estradiol (p < 0.001, partial η2 = 0.64) and progesterone (p < 0.001, partial η2 = 0.77). Malondialdehyde, lipid hydroperoxides and CRP concentrations were higher in WomenOC during Late-activeOC compared to InactiveOC (+ 96%, + 23% and + 104%, respectively, p < 0.05). However, there were no changes in these biomarkers across the menstrual cycle in WomenNC (p > 0.05). At all timepoints (i.e., 1, 2 and 3), WomenOC had elevated lipid hydroperoxides (+ 28, + 48% and + 50%) and CRP (+ 71%, + 117% and + 130%) compared to WomenNC (p < 0.05, partial η2 > 0.25). There was no Group by Time effect on non-enzymatic antioxidants or glutathione peroxidase; however, glutathione peroxidase was lower in WomenOC, i.e., main effect of group (p < 0.05, partial η2 > 0.20). CONCLUSION: These findings demonstrate that WomenOC not only have higher oxidative stress and CRP than WomenNC, but also a transient increase across one month of habitual oral contraceptive use. Since changes in oxidative stress and CRP often relate to training stress and recovery, these outcomes may have implications to workload monitoring practices in female athletes.

Reliability of a point-of-care device to determine oxidative stress in whole blood before and after acute exercise: A practical approach for the applied sports sciences.

Measuring alterations in redox homoeostasis in athletes can provide insights into their responses to training such as adaptations or fatigued states. However, redox monitoring is impractical in athletes given the time burden of venepuncture and subsequent laboratory assays. The ability of point-of-care tests (POC): 1) Free Oxygen Radical Test (FORT) and 2) Free Oxygen Radical Defence (FORD), to reliably measure whole blood oxidative stress between days and after exercise is unknown as well as their relationship with laboratory measures (F2-isoprostanes, total antioxidant capacity; TAC). Participants completed two trials performed on separate days comprising blood sampling at rest (n=22) and after treadmill-running (n=14). Between-day CVs for FORT (4.6%) and FORD (4.8%) were acceptable at rest. There was no difference in the between-day magnitude of change in any biomarker from pre- to post-exercise (p>0.05), yet the within-trial change in FORD was variable (trial one: +4.5%, p=0.15; trial two: +6.3%, p<0.05). TAC and FORD were significantly correlated pre- and post-exercise (r=~0.53, p<0.05), whereas F2-isoprostanes and FORT had a significant correlation pre-exercise only (r=0.45, p=0.03). Overall, the POC tests are reliable and could be used for baseline longitudinal redox monitoring. More data is required on POC tests for assessing redox perturbations induced by exercise.

Quantification of maximal power output in well-trained cyclists.

This study aimed to compare mechanical variables derived from torque-cadence and power-cadence profiles established from different cycle ergometer modes (isoinertial and isokinetic) and modelling procedures (second- and third-order polynomials), whilst employing a novel method to validate the theoretical maximal power output (Pmax). Nineteen well-trained cyclists (n = 12 males) completed two experimental sessions comprising six, 6-s maximal isoinertial or isokinetic cycling sprints. Maximal pedal strokes were extracted to construct power-cadence relationships using second- and third-order polynomials. A 6-s sprint at the optimal cadence (Fopt) or optimal resistance (Topt) was performed to assess construct validity of Pmax. No differences were found in the mechanical parameters when derived from isokinetic (Pmax = 1311 ± 415, Fopt = 118 ± 12) or isoinertial modes (Pmax = 1320 ± 421, Fopt = 116 ± 19). However, R2 improved (P < 0.02) when derived from isoinertial sprints. Third-order polynomial modelling improved goodness of fit values (Standard Error, adjusted R2), but derived similar mechanical parameters. Finally, peak power output during the optimised sprint did not significantly differ from the theoretical Pmax in both cycling modes, thus providing construct validity. The most accurate P-C profile can be derived from isoinertial cycling sprints, modelled using third-order polynomial equations.

Strong, Fast, Fit, Lean, and Safe: A Positional Comparison of Physical and Physiological Qualities Within the 2020 Australian Women's Rugby League Team.

ABSTRACT: Minahan, C, Newans, T, Quinn, K, Parsonage, J, Buxton, S, and Bellinger, P. Strong, Fast, Fit, Lean, and Safe: A positional comparison of physical and physiological qualities within the 2020 Australian Women's Rugby League team. J Strength Cond Res 35(12S): S11-S19, 2021-The purpose of the present study was to report the physical and physiological characteristics of elite women Rugby League (RL) players. Thirty-nine women (25.6 ± 4.3 years, 171.3 ± 7.7 cm, 83.5 ± 13.9 kg) from the 2020 Australian women's RL squad were recruited for this study. Players were categorized as adjustables (n = 7), backs (n = 15), or forwards (n = 17) for analysis. Each player was assessed for anthropometry, body composition (dual-energy X-ray absorptiometry), speed (5, 10 and 20 m sprint times), lower-body power (countermovement jump), upper-body power (medicine ball throw and explosive push up force), estimated one repetition maximum (e1RM) bench press, squat and bench pull, isometric mid-thigh pull strength, eccentric knee flexor strength, isometric hip abduction and adduction, and intermittent endurance performance (30-15 intermittent fitness test; 30-15 IFT). Linear mixed models were performed to compare positional groups. Forwards were significantly heavier and had greater fat mass, fat-free mass, and body fat percentage compared with backs and adjustables (P < 0.01). Backs were faster over 20 m compared with forwards (P = 0.025), whereas forwards had a lower 30-15 IFT peak velocity and estimated V̇o2peak compared with backs and adjustables. Nonetheless, when including body mass in the model, there were no differences between groups in 30-15 IFT peak velocity. There were no significant differences in other variables. These results provide contemporary benchmark physical, physiological, and anthropometric data for elite women RL players, which can inform recruitment, selection, training, and testing.

Quantifying the Activity Profile of Female Beach Volleyball Tournament Match-Play.

Effective time-motion analysis can provide information directly applicable to the design of physical conditioning and testing programmes. The aim of the present study was to determine the external output of female beach volleyball players during tournament match-play and to assess the effect of competition level, margin of score differential and alterations of external output within matches. The external output profile of ten adult level (age 27 ± 3 y) and ten under 23 ('U23'; age 19 ± 2 y) female beach volleyball players were determined using GPS technology (10 Hz) during 60 matches (n = 50 first and second sets and 20 third sets files) played during their respective Australian Beach Volleyball Championship tournaments. Comparisons between groups and the influence of contextual factors on the external output within matches were analysed using linear mixed models. Adult beach volleyball players covered a greater relative distance (i.e., m·min-1) in speed zone 2 (1.0-1.99 m·s-1; 42.0% of total relative distance) and zone 3 (≥2.0 m·s-1; 10.9% of total relative distance) compared to U23 players. Relative distance, mean acceleration/deceleration and the relative distance covered in acceleration zone 2 and deceleration zone 2 and 3 was greater in set 1 compared to set 2. Sets that were decided by smaller score margins (<6-point score differential) were comprised of a greater relative distance, peak speed, greater mean acceleration and deceleration output and a greater relative distance in speed zone 1 and 3 compared to sets decided by larger score margins (>5-point score differential). The findings from this study suggest that there are contextual factors that influence the speed and acceleration/deceleration profile of female beach volleyball players such as tournament level, score margin and set-to-set variations that may have implications for the physiological and mechanical requirements of female players preparing for competition.

Fusing Accelerometry with Videography to Monitor the Effect of Fatigue on Punching Performance in Elite Boxers.

Wearable sensors and motion capture technology are accepted instruments to measure spatiotemporal variables during punching performance and to study the externally observable effects of fatigue. This study aimed to develop a computational framework enabling three-dimensional inverse dynamics analysis through the tracking of punching kinematics obtained from inertial measurement units and uniplanar videography. The framework was applied to six elite male boxers performing a boxing-specific punch fatigue protocol. OpenPose was used to label left side upper-limb landmarks from which sagittal plane kinematics were computed. Custom-made inertial measurement units were embedded into the boxing gloves, and three-dimensional punch accelerations were analyzed using statistical parametric mapping to evaluate the effects of both fatigue and laterality. Tracking simulations of a sub-set of left-handed punches were formulated as optimal control problems and converted to nonlinear programming problems for solution with a trapezoid collocation method. The laterality analysis revealed the dominant side fatigued more than the non-dominant, while tracking simulations revealed shoulder abduction and elevation moments increased across the fatigue protocol. In future, such advanced simulation and analysis could be performed in ecologically valid contexts, whereby multiple inertial measurement units and video cameras might be used to model a more complete set of dynamics.

Muscle Damage and Metabolic Responses to Repeated-Sprint Running With and Without Deceleration.

Minahan, CL, Poke, DP, Morrison, J, and Bellinger, PM. Muscle damage and metabolic responses to repeated-sprint running with and without deceleration. J Strength Cond Res 34(12): 3423-3430, 2020-This study aimed to determine whether repeated-sprint running with deceleration aggravates markers of muscle damage or delays the recovery of performance compared with repeated-sprint running without deceleration. Fourteen male team-sport athletes performed 2 randomly ordered testing sessions on a nonmotorized treadmill with one session requiring subjects to decelerate (TMd) within 4 seconds before stopping or immediately step to the side of the treadmill belt at the completion of each sprint (TMa). Peak and mean velocities, speed decrement, blood lactate concentrations, and oxygen uptake were monitored during the repeated-sprint running protocols. Countermovement vertical jump (CMJ) performance, perceived muscle soreness, sit-and-reach flexibility, plasma creatine kinase (CK), lactate dehydrogenase (LDH), and myoglobin (Mb) concentrations were quantified immediately before and after and 45 minutes, 24 and 48 hours after repeated-sprint running protocols. Although muscle damage was indicated by increases in CK, LDH, and Mb (p ≤ 0.05) in both groups, there was no significant effect of condition (TMa vs. TMd) on any of the measured performance or physiological variables (p > 0.05). The present study indicated that the removal of deceleration from repeated-sprint running on a nonmotorized treadmill has no effect on metabolism or performance during or after repeated-sprint running or markers of muscle damage.

Women's Football: An Examination of Factors That Influence Movement Patterns.

Griffin, J, Larsen, B, Horan, S, Keogh, J, Dodd, K, Andretta, M, and Minahan, C. Title: Women's football: An examination of factors that influence movement patterns. J Strength Cond Res 34(8): 2384-2393, 2020-The popularity and professionalism of women's football has increased in conjunction with participation rates over the last 10 years, with projected female participation rates to double worldwide by 2026. Scientific interest has also increased, in part due to Fédération Internationale de Football Association now allowing global positioning system (GPS) units to be worn during all competitive matches, resulting in investigations into the match demands of women's football. Therefore, the purpose of the present review is to provide a summary of the literature specific to the movement patterns of women's football matches. Contemporary scientific investigation using GPS match data has led to a greater understanding of the movement patterns of football. Greater emphasis has been placed on high-speed running and sprinting during matches because of the strong link to scoring opportunities and being a distinguishing factor between international and national along with elite and subelite competition levels. Further research, however, is warranted in regard to accelerations and decelerations, given the high metabolic and mechanical loads and contribution to high-speed running and sprinting. With an influx of research into the movement patterns of match-play, investigators have begun to examine factors affecting match performance such as positional demands, age, level of competition, opponent, scoreline, and phase of the game. An understanding of the factors that influence match demands is vital to ultimately be able to understand the effects on performance and how manipulating these factors may improve football performance and reduce the risk of injury.

Modelling the Acceleration and Deceleration Profile of Elite-level Soccer Players.

The ability to change velocity rapidly is a key element of field-based sports. This study quantified the acceleration and deceleration profiles of soccer players during match play. Global positioning system measures were collected from 20 male soccer players competing in the Australian Hyundai A-League during 58 matches. Match data were organized into ten 9 min periods (i. e., P1: 0-9 min) and the time spent at moderate (1-2 m·s-2) and high (>2 m·s-2) acceleration and deceleration thresholds were quantified. Additionally, a novel deceleration: acceleration ratio was quantified to identify the transient nature of deceleration activity. Linear mixed models were used to model the acceleration and deceleration profiles. All acceleration and deceleration metrics displayed negative logarithmic curves within each half. There was no change in the ratio of high deceleration: acceleration; however, a significant increase in the ratio of moderate deceleration:acceleration was evident. Using negative logarithmic curves to illustrate the acceleration and deceleration decay provides a novel methodological approach to quantify the high-intensity actions during match play. A decrease in the time spent decelerating throughout a match may be attributed to a lack of opportunity. Practitioners can use the coefficients, intercepts, and deceleration: acceleration ratios to monitor a player's deceleration profile in match play.

Repeated Treadmill Sprints Impair Cognitive Performance in Amateur Team-Sport Athletes When Performed in Normobaric Hypoxia.

This study determined if a single bout of repeated-sprint running under hypoxic (RSH) conditions was associated with impaired cognitive function when compared with repeated-sprint running under normoxic (RSN) conditions. Eleven amateur team-sport athletes performed a repeated-sprint running protocol (4 sets of 4, 4-s all-out sprints; i.e., RSR444) under both conditions (14.5% and 20.9% O2) on a non-motorized treadmill. Changes in SpO2, pre-frontal cortex total haemoglobin (Δ[THb]), oxyhaemoglobin (Δ[O2Hb]), deoxyhaemoglobin (Δ[HHb]) and cognitive function (detection task: DET; identification task: IDN; one card learning task: OCL; performed pre and 20 min post RSR444) were examined. During RSH, SpO2 was lower following each set (p ≤ 0.05), while [HHb] was higher after each set (p ≤ 0.05) compared with RSN. In addition, while there was no effect of condition on DET (p = 0.20) or IDN (p = 0.14), OCL accuracy was lower after, compared with before, RSH (p=0.04), but not RSN (p = 0.52). A significant relationship was observed between Δ[HHB] and ΔOCL accuracy (r = -0.68, p = 0.01). Performance of a single bout of RSH with 14.5% O2 resulted in impaired cognitive function in amateur team-sport athletes. Coaches should be mindful of timing of RSH prescription with regard to other training sessions that challenge speed and movement accuracy.

Cerebral oxygenation declines but does not impair peak oxygen uptake during incremental cycling in women using oral contraceptives.

PURPOSE: To compare prefrontal cortex oxygenation in recreationally-active women using oral contraceptives (WomenOC; n = 8) to women with a natural menstrual cycle (WomenNC; n = 8) during incremental exercise to exhaustion. METHODS: Participants performed incremental cycling to exhaustion to determine lactate threshold 1 (LT1) and 2 (LT2) and peak oxygen uptake (VO2peak). Prefrontal cortex oxygenation was monitored via near-infrared spectroscopy through concentration changes in oxy-haemoglobin (Δ[HbO2]), deoxy-haemoglobin (Δ[HHb]), total-haemoglobin (Δ[tHb]) and tissue saturation index (TSI). RESULTS: 17ß-oestradiol and progesterone were lower in WomenOC (35 ± 26; 318 ± 127 pmol·L-1, respectively) than WomenNC (261 ± 156; 858 ± 541 pmol·L-1, respectively). There were no differences in full blood examination results or serum nitric oxide (p > 0.05). However, WomenOC presented lower concentrations in ferric-reducing ability of plasma (- 8%; effect size; ES - 0.52 ± 0.61), bilirubin (- 32%; ES - 0.56 ± 0.62) and uric acid (- 17%; ES - 0.53 ± 0.61). Cardiopulmonary parameters were similar between groups during cycling, including VO2peak (p = 0.99). While there was a significant effect of time on all parameters measured by near-infrared spectroscopy during incremental cycling, there was no effect of OC at LT1, LT2 or exhaustion calculated as a change from baseline (TSI; p = 0.096, Δ[HbO2]; p = 0.143, Δ[HHb]; p = 0.085 and Δ[tHb]; p = 0.226). The change in TSI from LT1 to LT2 was significantly different between groups (WomenNC; mean difference + 2.06%, WomenOC; mean difference - 1.73%; p = 0.003). CONCLUSION: Prefrontal tissue oxygenation declined at a lower relative exercise intensity in WomenOC as compared to WomenNC, however, this did not influence VO2peak. The results provide the first evidence for variance in the cerebral oxygenation response to exercise, which may be associated with female sex hormones.