A model for calculating the mechanical demands of overground running.

An energy-based approach to quantifying the mechanical demands of overground, constant velocity and/or intermittent running patterns is presented. Total mechanical work done (Wtotal) is determined from the sum of the four sub components: work done to accelerate the centre of mass horizontally (Whor), vertically (Wvert), to overcome air resistance (Wair) and to swing the limbs (Wlimbs). These components are determined from established relationships between running velocity and running kinematics; and the application of work-energy theorem. The model was applied to constant velocity running (2-9 m/s), a hard acceleration event and a hard deceleration event. The estimated Wtotal and each sub component were presented as mechanical demand (work per unit distance) and power (work per unit time), for each running pattern. The analyses demonstrate the model is able to produce estimates that: 1) are principally determined by the absolute running velocity and/or acceleration; and 2) can be attributed to different mechanical demands given the nature of the running bout. Notably, the proposed model is responsive to varied running patterns, producing data that are consistent with established human locomotion theory; demonstrating sound construct validity. Notwithstanding several assumptions, the model may be applied to quantify overground running demands on flat surfaces.

Repeated Ischemic Preconditioning Effects on Physiological Responses to Hypoxic Exercise.

INTRODUCTION: Repeated ischemic preconditioning (IPC) can improve muscle and pulmonary oxygen on-kinetics, blood flow, and exercise efficiency, but these effects have not been investigated in severe hypoxia. The aim of the current study was to evaluate the effects of 7 d of IPC on resting and exercising muscle and cardio-pulmonary responses to severe hypoxia.METHODS: A total of 14 subjects received either: 1) 7 d of repeated lower-limb occlusion (4 × 5 min, 217 ± 30 mmHg) at limb occlusive pressure (IPC) or SHAM (4 × 5 min, 20 mmHg). Subjects were tested for resting limb blood flow, relative microvascular deoxyhemoglobin concentration ([HHB]), and pulmonary oxygen (Vo2p) responses to steady state and incremental exercise to exhaustion in hypoxia (fractional inspired O2 = 0.103), which was followed by 7 d of IPC or SHAM and retesting 72 h post-intervention.RESULTS: There were no effects of IPC on maximal oxygen consumption, time to exhaustion during the incremental test, or minute ventilation and arterial oxygen saturation. However, the IPC group had higher delta efficiency based on pooled results and lower steady state Δ[HHB] (IPC ∼24% vs. SHAM ∼6% pre to post), as well as slowing the [HHB] time constant (IPC ∼26% vs. SHAM ∼3% pre to post) and reducing the overshoot in [HHB]: Vo2 ratio during exercise onset.CONCLUSIONS: Collectively, these results demonstrate that muscle O2 efficiency and microvascular O2 distribution can be improved by repeated IPC, but there are no effects on maximal exercise capacity in severe hypoxia.Chopra K, Jeffries O, Tallent J, Heffernan S, Kilduff L, Gray A, Waldron M. Repeated ischemic preconditioning effects on physiological responses to hypoxic exercise. Aerosp Med Hum Perform. 2022; 93(1):13-21.

A new energetics model for the assessment of the power-duration relationship during over-ground running.

We evaluated the reliability of an over-ground running three-minute all-out test (3MT) and compared this to traditional multiple-visit testing to determine the critical speed (CS) and distance > CS (D´). Using a novel energetics model during the 3MT, critical power (CP) and work > CP (W´) were also evaluated for reliability and compared to the multiple-visit tests. Over-ground running speed was measured using Global Positioning Systems during fixed-speed trials on a 400 m track to exhaustion, at four intensities corresponding to: (i) maximal oxygen uptake (V˙O2max) (Vmax), (ii) 110% V˙O2max(110%Vmax), (iii) Δ70% (i.e. 70% of the difference between gas exchange threshold and Vmax) and (iv) Δ85%. The participants subsequently performed the 3MT across two days to determine its reliability. There were no differences between the multiple-visit testing and the 3MT for CS (P = 0.328) and D´ (P = 0.919); however, CP (P = 0.02) and W´ (P < 0.001) were higher in the 3MT. The reliability of the 3MT was stable (P > 0.05) between trials for all variables, with coefficient of variation ranging from 2.0-8.1%. The current over-ground energetics model can reliably estimate CP and W´ based on GPS speed data during the 3MT, which supports its use for most athletic training and monitoring purposes. The reliability of the over-ground running 3MT for power- and speed-related indices was sufficient to detect typical training adaptations; however, it may overestimate CP (∼ 25 W) and W´ (∼ 7 kJ) compared to multiple-visit tests.

Conceptualising Rugby League Performance Within an Ecological Dynamics Framework: Providing Direction for Player Preparation and Development.

Across team sports, it is critically important to appropriately define, evaluate and then aptly describe individual and team performance. This is of particular significance when we consider that performance models govern the direction of player preparation (short term) and development (long term) frameworks. Within the context of rugby league, this has traditionally been undertaken through hierarchical and linear processes. Such approaches have resulted in research and performance analysis techniques which aim to support these operational outcomes. Yet, these methods may deliver limited application on how or why match-play unfolds and therefore might be sub-optimal in providing insights to truly support coaches. In this paper, we propose the conceptualisation of rugby league performance through the lens of ecological dynamics, which may offer a different view to this traditional approach. We propose that this approach eliminates the silos of disciplinary information (e.g. technical, physical and medical) that may currently exist, allowing for a holistic approach to performance, preparation and development. Specifically, we consider that through the implementation of this ecological approach, all performance coaches (technical, physical and medical) may (co-)design learning environments that more collaboratively develop players for rugby league match-play. As a result, we put forward a new rugby league performance model from which preparation and development programs can be anchored toward. We conclude the paper by offering practical examples where these concepts are contextualised within the landscape familiar to practitioners working within rugby league.

Co-expression analysis identifies networks of miRNAs implicated in biological ageing and modulated by short-term interval training.

Exercise training seems to promote healthy biological ageing partly by inducing telomere maintenance, yet the molecular mechanisms are not fully understood. Recent studies have emphasised the importance of microRNAs (miRNAs) in ageing and their ability to mirror pathophysiological alterations associated with age-related diseases. We examined the association between aerobic fitness and leukocyte telomere length before determining the influence of vigorous exercise training on the regulation of leukocyte miRNA networks. Telomere length was positively correlated to aerobic fitness (r = 0.32, p = 0.02). 104 miRNAs were differentially expressed after six weeks of thrice-weekly sprint interval training (SIT) in healthy men (q < 0.05). Gene co-expression analysis (WGCNA) detected biologically meaningful miRNA networks, five of which were significantly correlated with pre-SIT and post-SIT expression profiles (p < 0.001) and telomere length. Enrichment analysis revealed that the immune response, T cell differentiation and lipid metabolism associated miRNAs clusters were significantly down-regulated after SIT. Using data acquired from the Gene Expression Omnibus (GEO), we also identified two co-expressed miRNAs families that were modulated by exercise training in previous investigations. Collectively, our findings highlight the miRNA networks implicated in exercise adaptations and telomere regulation, and suggest that SIT may attenuate biological ageing through the control of the let-7 and miR-320 miRNA families.

A New Foot-Mounted Inertial Measurement System in Soccer: Reliability and Comparison to Global Positioning Systems for Velocity Measurements During Team Sport Actions.

The aims of this study were to i) compare a foot-mounted inertial system (PlayerMaker™) to three commercially available Global Positioning Systems (GPS) for measurement of velocity-based metrics during team sport movements and ii) evaluate the inter-unit reliability of the PlayerMaker™. Twelve soccer players completed a soccer simulation, whilst wearing a PlayerMaker™ and three GPS (GPS#1, #2 and #3). A sub-sample (n = 7) also wore two PlayerMaker™ systems concurrently. The PlayerMaker™ measured higher (p < 0.05) total distance (518 ± 15 m) compared to GPS#1 (488 ± 15 m), GPS#2 (486 ± 15 m), and GPS#3 (501 ± 14 m). This was explained by greater (p < 0.05) distances in the 1.5-3.5 m/s zone (356 ± 24 m vs. 326 ± 26 m vs. 324 ± 18 m vs. 335 ± 24 m) and the 3.51-5.5 m/s zone (64 ± 18 m vs. 35 ± 5 vs. 43 ± 8 m vs. 41 ± 8 m) between the PlayerMaker™, GPS#1, GPS#2 and GPS#3, respectively. The PlayerMaker™ recorded higher (p < 0.05) distances while changing speed. There were no systematic differences (p > 0.05) between the two PlayerMaker™ systems. The PlayerMaker™ is reliable and records higher velocity and distances compared to GPS.

Predicting Temporal Gait Kinematics From Running Velocity.

ABSTRACT: Gray, A, Price, M, and Jenkins, D. Predicting temporal gait kinematics from running velocity. J Strength Cond Res 35(9): 2379-2382, 2021-The manner in which stride frequency (f) changes in response to running velocity (v) is well established. Notably, as running velocity increases, duty factor (d, the % of the stride in stance) decreases, concomitantly with higher stride frequencies. Mathematical descriptions of this relationship do not exist, limiting our ability to reasonably predict gait-based metrics from wearable technologies. Therefore, the purpose of this study was to establish prediction equations for stride frequency and duty factor from running velocity. On 2 occasions, 10 healthy men (aged, 21.1 ± 2.2 years) performed constant pace running efforts at 3, 4, 5, 6, 7, and 8 m·s-1 over a 10-m segment on a tartan athletics track. Running efforts were filmed using a digital video camera at 300 frames per second, from which stride duration, support duration, and swing duration were determined. Regression equations to predict stride frequency and duty factor from running velocity were established by curve fitting. Acceptable test-retest reliability for the video-based determination of stride frequency (intraclass correlation = 0.87; typical error of the measurement [TEM] = 0.01 Hz; coefficient of variation [CV] = 2.9%) and duty factor (r = 0.93; TEM = 1%; CV = 3.9%) were established. The relationship between stride frequency and running velocity was described by the following quadratic equation: f = 0.026·v2 - 0.111·v + 1.398 (r2 = 0.903). The relationship between duty factor and running velocity was described by the quadratic equation d = 0.004·v2 - 0.061·v + 0.50 (r2 = 0.652). The relationships between v and f and between v and d are consistent with previous observations. These equations may contribute broader locomotor models or serve as input variables in data fusion algorithms that enhance outputs from wearable technologies.

Cycling Power Outputs Predict Functional Threshold Power and Maximum Oxygen Uptake.

Denham, J, Scott-Hamilton, J, Hagstrom, AD, and Gray, AJ. Cycling power outputs predict functional threshold power and maximum oxygen uptake. J Strength Cond Res 34(12): 3489-3497, 2020-Functional threshold power (FTP) has emerged as a correlate of lactate threshold and is commonly assessed by recreational and professional cyclists for tailored exercise programing. To identify whether results from traditional aerobic and anaerobic cycling tests could predict FTP and V[Combining Dot Above]O2max, we analyzed the association between estimated FTP, maximum oxygen uptake (V[Combining Dot Above]O2max [ml·kg·min]) and power outputs obtained from a maximal cycle ergometry cardiopulmonary exercise test (CPET), and a 30-second Wingate test in a heterogeneous cohort of cycle-trained and untrained individuals (N = 40, mean ± SD; age: 32.6 ± 10.6 years; relative V[Combining Dot Above]O2max: 46.8 ± 9.1 ml·kg·min). The accuracy and sensitivity of the prediction equations were also assessed in young men (N = 11) before and after a 6-week sprint interval training intervention. Moderate-to-strong positive correlations were observed between FTP, relative V[Combining Dot Above]O2max, and power outputs achieved during incremental and 30-second Wingate cycling tests (r = 0.39-0.965, all p ≤ .05). Whilst maximum power achieved during incremental cycle testing (Pmax) and relative V[Combining Dot Above]O2max were predictors of FTP (r = 0.93), age and FTP (W·kg) estimated relative V[Combining Dot Above]O2max (r = 0.80). Our findings confirm that FTP predominantly relies on aerobic metabolism and indicate that both prediction models are sensitive enough to detect meaningful exercise-induced changes in FTP and V[Combining Dot Above]O2max. Thus, coaches should consider limiting the time and load demands placed on athletes by conducting a maximal cycle ergometry CPET to estimate FTP. In addition, a 20-minute FTP test is a convenient method to assess V[Combining Dot Above]O2max and is particularly relevant for exercise professionals without access to expensive CPET equipment.

Exercise tolerance during flat over-ground intermittent running: modelling the expenditure and reconstitution kinetics of work done above critical power.

PURPOSE: We compared a new locomotor-specific model to track the expenditure and reconstitution of work done above critical power (W´) and balance of W´ (W´BAL) by modelling flat over-ground power during exhaustive intermittent running. METHOD: Nine male participants completed a ramp test, 3-min all-out test and the 30-15 intermittent fitness test (30-15 IFT), and performed a severe-intensity constant work-rate trial (SCWR) at the maximum oxygen uptake velocity (vV̇O2max). Four intermittent trials followed: 60-s at vV̇O2max + 50% Δ1 (Δ1 = vV̇O2max - critical velocity [VCrit]) interspersed by 30-s in light (SL; 40% vV̇O2max), moderate (SM; 90% gas-exchange threshold velocity [VGET]), heavy (SH; VGET + 50% Δ2 [Δ2 = VCrit - VGET]), or severe (SS; vV̇O2max - 50% Δ1) domains. Data from Global Positioning Systems were derived to model over-ground power. The difference between critical and recovery power (DCP), time constant for reconstitution of W´ ([Formula: see text]), time to limit of tolerance (TLIM), and W´BAL from the integral (W´BALint), differential (W´BALdiff), and locomotor-specific (OG-W´BAL) methods were compared. RESULTS: The relationship between [Formula: see text] and DCP was exponential (r2 = 0.52). The [Formula: see text] for SL, SM, and SH trials were 119 ± 32-s, 190 ± 45-s, and 336 ± 77-s, respectively. Actual TLIM in the 30-15 IFT (968 ± 117-s) compared closely to TLIM predicted by OG-W´BAL (929 ± 94-s, P > 0.100) and W´BALdiff (938 ± 84-s, P > 0.100) but not to W´BALint (848 ± 91-s, P = 0.001). CONCLUSION: The OG-W´BAL accurately tracked W´ kinetics during intermittent running to exhaustion on flat surfaces.

Small non-coding RNAs are altered by short-term sprint interval training in men.

Small non-coding RNAs (ncRNAs) are emerging as important molecules for normal biological processes and are deregulated in disease. Exercise training is a powerful therapeutic strategy that prevents cardiometabolic disease and improves cardiorespiratory fitness and performance. Despite the known systemic health benefits of exercise training, the underlying molecular mechanisms are incompletely understood. Recent evidence suggests a role for epigenetic mechanisms, such as microRNAs, but whether other small ncRNAs are modulated by chronic exercise training is unknown. Here, we used small RNA sequencing to explore whether sprint interval training (SIT) controls the abundance of circulating small ncRNAs in human whole blood samples. Ten healthy men performed SIT three times a week for 6 weeks. After training, subjects showed marked improvements in maximal oxygen consumption and cycling performance with concurrent changes to the abundance of diverse species of circulating small ncRNAs (n = 1266 small ncRNAs, n = 13 microRNAs, q < 0.05). Twelve microRNAs altered by 6 weeks of SIT were ubiquitously expressed microRNAs and two regulated important signaling pathways, including p53, thyroid hormone and cell cycle signaling. MicroRNAs altered by 6 weeks of SIT were unchanged after a single session of SIT (n = 24, all P > 0.05). Relative to older individuals, younger subjects exhibited an increased acute SIT-induced fold change in miR-1301-3p (P = 0.02) - a microRNA predicted to target mRNAs involved in alternative splicing, phosphoprotein and chromosomal rearrangement processes (all P < 0.001). Our findings indicate many species of circulating small ncRNAs are modulated by exercise training and that they could control signaling pathways responsible for health benefits achieved from exercise.

Beetroot supplementation improves the physiological responses to incline walking.

PURPOSE: We investigated the effects of an acute 24-h nitrate-rich beetroot juice supplement (BR) on the energy cost, exercise efficiency and blood pressure responses to intermittent walking at different gradients. METHODS: In a double-blind, cross-over design, eight participants were provided with a total of 350 ml of nitrate-rich (~ 20.5 mmol nitrate) BR or placebo (PLA) across 24 h before completing intermittent walking at 3 km/h on treadmill at gradients of 1, 5, 10, 15 and 20%. RESULTS: Resting mean arterial pressure (MAP) was ~ 4.1% lower after BR (93 vs. 89 mmHg; P = 0.001), as well as during exercise (102 vs. 99 mmHg; P = 0.011) and recovery (97 vs. 94 mmHg; P = 0.001). Exercising (1227 vs. 1129 ml/min P < 0.001) and end-stage (1404 vs. 1249 ml/min; P = 0.002) oxygen uptake ([Formula: see text]O2) was lower in BR compared to PLA, which was accompanied by an average reduction in phase II [Formula: see text]O2 amplitude (1067 vs. 940 ml/min; P = 0.025). Similarly, recovery [Formula: see text]O2 (509 vs. 458 ml/min; P = 0.001) was lower in BR. Whole blood potassium concentration increased from pre-post exercise in PLA (4.1 ± 0.3 vs. 4.5 ± 0.3 mmol/L; P = 0.013) but not BR (4.1 ± 0.31 vs. 4.3 ± 0.2 mmol/L; P = 0.188). CONCLUSIONS: Energy cost of exercise, recovery of [Formula: see text]O2, MAP and blood markers were ameliorated after BR. Previously-reported mechanisms explain these findings, which are more noticeable during less-efficient walking at steep gradients (15-20%). These findings have practical implications for hill-walkers.

Modelling Movement Energetics Using Global Positioning System Devices in Contact Team Sports: Limitations and Solutions.

Quantifying the training and competition loads of players in contact team sports can be performed in a variety of ways, including kinematic, perceptual, heart rate or biochemical monitoring methods. Whilst these approaches provide data relevant for team sports practitioners and athletes, their application to a contact team sport setting can sometimes be challenging or illogical. Furthermore, these methods can generate large fragmented datasets, do not provide a single global measure of training load and cannot adequately quantify all key elements of performance in contact team sports. A previous attempt to address these limitations via the estimation of metabolic energy demand (global energy measurement) has been criticised for its inability to fully quantify the energetic costs of team sports, particularly during collisions. This is despite the seemingly unintentional misapplication of the model's principles to settings outside of its intended use. There are other hindrances to the application of such models, which are discussed herein, such as the data-handling procedures of Global Position System manufacturers and the unrealistic expectations of end users. Nevertheless, we propose an alternative energetic approach, based on Global Positioning System-derived data, to improve the assessment of mechanical load in contact team sports. We present a framework for the estimation of mechanical work performed during locomotor and contact events with the capacity to globally quantify the work done during training and matches.

Sprint Interval Training Decreases Circulating MicroRNAs Important for Muscle Development.

Small non-coding RNAs, such as microRNAs (miRNAs), have emerged as powerful post-transcriptional regulators of gene expression that play important roles in many developmental and biological processes. In this study, we assessed the abundance of circulating microRNAs important for skeletal muscle and heart adaptations to exercise (miR-1, miR-133a, miR-133b and miR-486), following acute exercise and short-term sprint interval training (SIT). Twenty-eight individuals completed four all-out efforts on a cycle ergometer, and donated blood before and 30 min after the cessation of exercise. A subset of 10 untrained men completed 4-6 efforts of SIT, three times a week for 6 weeks, and donated resting blood samples before and after the intervention. MiRNA TaqMan qPCR was performed and whilst no changes were observed after a single session of SIT (all p>0.05), the 6-wk SIT intervention significantly reduced the whole blood content of all four miRNAs (mean fold-changes: 0.37-0.48, all p<0.01). Our data suggests that circulating miRNAs are responsive to short-term SIT and could have roles in SIT-induced health and performance adaptations. Further work is required to establish whether circulating miRNAs could serve as biomarkers for predicting exercise training responses and monitoring exercise interventions.

Energetic Demands of Interchange and Full-Match Rugby League Players.

Cummins, CJ, Gray, AJ, Shorter, KA, Halaki, M, and Orr, R. Energetic demands of interchange and full-match rugby league players. J Strength Cond Res 32(12): 3456-3464, 2018-The purpose of this study was to describe and compare the metabolic demands of rugby league for interchange and full-match players in relation to positional groups. Eighteen elite rugby league players were recruited. A time-motion model was used to estimate the energy expenditure and metabolic demands of rugby league match-play using Global Positioning System (GPS) technology. This approach uses players' GPS velocity-time curves to examine running velocity. Players were categorized into positional groups (outside backs, adjustables, wide-running, and hit-up forwards) and then further categorized into full-match or interchange players. Compared with their full-match counterparts, interchange wide-running forwards expended greater energy (43.1 ± 6.1 vs. 28.6 ± 7.5 kJ·kg, p ≤ 0.001, effect size [ES] = -2.38) and produced a higher anaerobic index (p = 0.016, ES = 0.56) and mean power (7.4%, p = 0.003, ES = 0.66) per match. Full-match adjustables expended 94.8% more energy (p ≤ 0.001, ES = -2.3) and performed more moderate accelerations (10.1%, p = 0.014, ES = -0.57) and decelerations (7.6%, p = 0.017, ES = -0.8), than their interchange counterparts. Outside backs did not interchange and hit-up forwards rarely (n = 2) played an entire match. Differing metabolic demands were identified for interchange and full-match players across positional groups, suggesting position-specific conditioning drills are required to model the energetic demands of match-play.

The Reliability of Functional Movement Screening and In-Season Changes in Physical Function and Performance Among Elite Rugby League Players.

This study aimed to (a) assess the reliability of the functional movement screening (FMS) protocol and (b) to establish changes in both FMS and tests of physical performance throughout a season. The reliability of the FMS components (12 in total) was assessed through a nonparametric statistical approach, based on 2 trials, separated by 1 week. Score on the FMS, strength (3 repetition maximum full squat, 1 repetition maximum [1 RM] bench press), running speed (10 and 40 m), and jump height of 12 elite male under-19 rugby league players was monitored at pre-, mid-, and late-season periods. There was no bias (p > 0.05) found between trials for the FMS, with the majority of components reaching 100% "perfect agreement," reflecting the good reliability of the FMS tool. There were no effects (p > 0.05) of season stage on any of the FMS components; however, an improvement (p ≤ 0.05) between the pre- and both mid- and late-season periods was apparent in every component of fitness, such as 1 RM bench press (112.92 ± 24.54 kg; 125.83 ± 21.41 kg; 125.98 ± 24.48 kg) and 40-m sprint time (5.69 ± 0.35 seconds; 5.62 ± 0.31 seconds; 5.64 ± 0.27 seconds). Our findings demonstrate that the FMS can be reliably administered to elite rugby league players but will not change in accordance with physical performance across a competitive season. Our findings should not necessarily deter practitioners from using the FMS but begin to question the specific qualities that are being assessed through its administration.

Ecological Validity and Reliability of the Rugby Sevens Simulation Protocol.

PURPOSE: To assess the ecological validity of the Rugby Sevens Simulation Protocol (R7SP) and to evaluate its interday reliability. METHODS: Ten male participants (20 ± 2 y, 74 ± 11 kg) completed 2 trials of the R7SP, separated by 7 d. The R7SP comprised typical running and collision activities, based on data recorded during international rugby sevens match play. Heart rate (HR) was monitored continuously during the R7SP, and the participants' movements were recorded through a 20-Hz global positioning system unit. Blood lactate and rating of perceived exertion were collected before and immediately after the 1st and 2nd halves of the R7SP. RESULTS: The average activity profile was 117 ± 5 m/min, of which 27 ± 2 m/min was covered at high speed, with a calculated energetic demand of 1037 ± 581 J/kg, of which ~40% was expended at a rate above 19 W/kg. Mean HR was 88% ± 4% of maximal HR. Participants spent ~45% ± 27% of time above 90% of maximal HR (t >90%HRmax). There were no significant differences between trials, except for lactate between the halves of the R7SP. The majority of the measured variables demonstrated a between-trials coefficient of variation (CV%) lower than 5%. Blood lactate measurements (14-20% CV) and t >90%HRmax (26% CV) were less reliable variables. In most cases, the calculated moderate worthwhile change was higher than the CV%. CONCLUSIONS: The R7SP replicates the activity profile and HR responses of rugby sevens match play. It is a reliable simulation protocol that can be used in a research environment to detect systematic worthwhile changes in selected performance variables.

Predicting the Sprint Performance of Adolescent Track Cyclists Using the 3-Minute All-out Test.

Waldron, M, Gray, A, Furlan, N, and Murphy, A. Predicting the sprint performance of adolescent track cyclists using the 3-minute all-out test. J Strength Cond Res 30(8): 2299-2306, 2016-This study aimed to predict 500-m time trial (TT) and 2,000-m pursuit speed of adolescent cyclists (age range = 13-15 years) using mechanical parameters derived from a critical power (CP) test and anthropometric variables. Ten well-trained competitive cyclists were assessed for body composition, body mass, stature, and frontal surface area (FSA), as well as completing the CP test. The personal best speed (km·h) of each rider during competition in 500-m TT and 2,000-m pursuit races was predicted based on the CP test data and anthropometric profiles using multiple regression analysis. A combination of the CP·FSA and internal (predicted) to external work ratio performed by the cyclists (Wint:Wext) predicted 500-m TT speed (R = 0.97; standard error of the estimate (SEE) = 0.82, P ≤ 0.001), whereas a combination of mean power·FSA (mean power) and body fat percentage predicted 2,000-m pursuit speed (R = 0.90; SEE = 1.5, p < 0.001). Between 90 and 97% of the variance in the sprint performance of adolescent cyclists can be explained by mechanical and anthropometric parameters, derived from a single visit to the laboratory. The tests and equations provided can be adopted by coaches to predict performance and set appropriate training intensities.

Running-Intensity Fluctuations in Elite Rugby Sevens Performance.

PURPOSE: To investigate temporal variation in running intensity across and within halves and evaluate the agreement between match-analysis indices used to identify fluctuations in running intensity in rugby sevens. METHODS: Data from a 15-Hz global positioning system (GPS) were collected from 12 elite rugby sevens players during the IRB World Sevens Series (N = 21 full games). Kinematic (eg, relative distance [RD]) and energetic (eg, metabolic power [MP]) match-analysis indices were determined from velocity-time curves and used to investigate between-halves variations. Mean MP and RD were used to identify peak 2-minute periods of play. Adjacent 2-minute periods (prepeak and postpeak) were compared with peak periods to identify changes in intensity. MP and RD were expressed relative to maximal oxygen uptake (VO2max) and speed at VO2max, respectively, and compared in their ability to describe the intensity of peak periods and their temporal occurrence. RESULTS: Small to moderate reductions were present for kinematic (RD; 8.9%) and energetic (MP; 6%) indices between halves. Peak periods (RD = 130 m/min, MP =13 W/kg) were higher (P < .001) than the match average (RD = 94 m/min, MP = 9.5 W/kg) and the prepeak and postpeak periods (P < .001). RD underestimated the intensity of peak periods compared with MP (bias 16%, limits of agreement [LoA] ± 6%). Peak periods identified by RD and MP were temporally dissociated (bias 21 s, LoA ± 212 s). CONCLUSIONS: The findings suggest that running intensity varies between and within halves; however, the index used will influence both the magnitude and the temporal identification of peak periods.

Copines-1, -2, -3, -6 and -7 show different calcium-dependent intracellular membrane translocation and targeting.

The copines are a family of C2- and von Willebrand factor A-domain-containing proteins that have been proposed to respond to increases in intracellular calcium by translocating to the plasma membrane. The copines have been reported to interact with a range of cell signalling and cytoskeletal proteins, which may therefore be targeted to the membrane following increases in cellular calcium. However, neither the function of the copines, nor their actual movement to the plasma membrane, has been fully established in mammalian cells. Here, we show that copines-1, -2, -3, -6 and -7 respond differently to a methacholine-evoked intracellular increase in calcium in human embryonic kidney cell line-293 cells, and that their membrane association requires different levels of intracellular calcium. We demonstrate that two of these copines associate with different intracellular vesicles following calcium entry into cells, and identify a novel conserved amino acid sequence that is required for their membrane translocation in living cells. Our data show that the von Willebrand factor A-domain of the copines modulates their calcium sensitivity and intracellular targeting. Together, these findings suggest a different set of roles for the members of this protein family in mediating calcium-dependent processes in mammalian cells.

Validity and reliability of GPS for measuring distance travelled in field-based team sports.

The aim of the present study was to examine the effects of movement intensity and path linearity on global positioning system (GPS) distance validity and reliability. One participant wore eight 1-Hz GPS receivers while walking, jogging, running, and sprinting over linear and non-linear 200-m courses. Five trials were performed at each intensity of movement on each 200-m course. One receiver was excluded from analysis due to errors during data collection. The results from seven GPS receivers showed the mean (± s) and percent bias of the GPS distance values on the 200-m linear course were 205.8 ± 2.4 m (2.8%), 201.8 ± 2.8 m (0.8%), 203.1 ± 2.2 m (1.5%), and 205.2 ± 4 m (2.5%) for the walk, jog, run, and sprint trial respectively. Walk and sprint distances were significantly different from jogging and running distances (P < 0.05). The GPS distance values on the 200-m non-linear course were 198.9 ± 3.5 m (-0.5%), 188.3 ± 2 m (-5.8%), 184.6 ± 2.9 m (-7.7%), and 180.4 ± 5.7 m (-9.8%) for the walk, jog, run, and sprint trial respectively; these were significantly lower than those for the corresponding values on the linear course (P < 0.05). Differences between all non-linear movement intensities were significant (P < 0.05). The overall coefficient of variation within and between receivers was 2.6% and 2.8% respectively. Path linearity and movement intensity appear to affect GPS distance accuracy via inherent positioning errors, update rate, and conditions of use; reliability decreases with movement intensity.