Bayesian prediction of winning times for elite swimming events.

To develop a statistical model of winning times for international swimming events with the aim of predicting winning time distributions and the probability of winning for the 2020 and 2024 Olympic Games. The data set included first and third place times from all individual swimming events from the Olympics and World Championships from 1990 to 2019. We compared different model formulations fitted with Bayesian inference to obtain predictive distributions; comparisons were based on mean percentage error in out-of-sample predictions of Olympics and World Championships winning swim times from 2011 to 2019. The Bayesian time series regression model, comprising auto-regressive and moving average terms and other predictors, had the smallest mean prediction error of 0.57% (CI 0.46-0.74%). For context, using the respective previous Olympics or World Championships winning time resulted in a mean prediction error of 0.70% (CI 0.59-0.82%). The Olympics were on average 0.5% (CI 0.3-0.7%) faster than World Championships over the study period. The model computes the posterior predictive distribution, which allows coaches and athletes to evaluate the probability of winning given an individual's swim time, and the probability of being faster or slower than the previous winning time or even the world record.

Predicting performance in 4 x 200-m freestyle swimming relay events.

AIM: The aim was to predict and understand variations in swimmer performance between individual and relay events, and develop a predictive model for the 4x200-m swimming freestyle relay event to help inform team selection and strategy. DATA AND METHODS: Race data for 716 relay finals (4 x 200-m freestyle) from 14 international competitions between 2010-2018 were analysed. Individual 200-m freestyle season best time for the same year was located for each swimmer. Linear regression and machine learning was applied to 4 x 200-m swimming freestyle relay events. RESULTS: Compared to the individual event, the lowest ranked swimmer in the team (-0.62 s, CI = [-0.94, -0.30]) and American swimmers (-0.48 s [-0.89, -0.08]) typically swam faster 200-m times in relay events. Random forest models predicted gold, silver, bronze and non-medal with 100%, up to 41%, up to 63%, and 93% sensitivity, respectively. DISCUSSION: Team finishing position was strongly associated with the differential time to the fastest team (mean decrease in Gini (MDG) when this variable was omitted = 31.3), world rankings of team members (average ranking MDG of 18.9), and the order of swimmers (MDG = 6.9). Differential times are based on the sum of individual swimmer's season's best times, and along with world rankings, reflect team strength. In contrast, the order of swimmers reflects strategy. This type of analysis could assist coaches and support staff in selecting swimmers and team orders for relay events to enhance the likelihood of success.

Live-cell single-molecule tracking highlights requirements for stable Smc5/6 chromatin association in vivo.

The essential Smc5/6 complex is required in response to replication stress and is best known for ensuring the fidelity of homologous recombination. Using single-molecule tracking in live fission yeast to investigate Smc5/6 chromatin association, we show that Smc5/6 is chromatin associated in unchallenged cells and this depends on the non-SMC protein Nse6. We define a minimum of two Nse6-dependent sub-pathways, one of which requires the BRCT-domain protein Brc1. Using defined mutants in genes encoding the core Smc5/6 complex subunits, we show that the Nse3 double-stranded DNA binding activity and the arginine fingers of the two Smc5/6 ATPase binding sites are critical for chromatin association. Interestingly, disrupting the single-stranded DNA (ssDNA) binding activity at the hinge region does not prevent chromatin association but leads to elevated levels of gross chromosomal rearrangements during replication restart. This is consistent with a downstream function for ssDNA binding in regulating homologous recombination.

The Efficacy of the Lactate Threshold: A Sex-Based Comparison.

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 34(11): 3190-3198, 2020-The second lactate threshold (LT2) has previously been associated with endurance performance; however, comparisons between sexes are lacking regarding its efficacy. The aim of this study was to compare LT2 between men and women, specifically regarding its (a) relationship with endurance performance and (b) capacity to establish training and competition intensities. Competitive male (mean ± SD: age, 27.7 ± 4.7 years; V[Combining Dot Above]O2max, 59.7 ± 5.2 ml·kg·min; n = 10) and female (mean ± SD: age, 27.3 ± 6.2 years; V[Combining Dot Above]O2max, 54.5 ± 5.3 ml·kg·min; n = 12) cyclists and triathletes completed an incremental cycle trial to volitional fatigue (for determination of V[Combining Dot Above]O2max and LT2 via the modified D-max method), a constant load (±5%) exercise trial of 30 minutes at LT2 power output, and a 40-km cycle time trial. The LT2 significantly correlated with 40-km cycling performance in both men (r = -0.69 to -0.77; p < 0.01-0.05) and women (r = -0.63 to -0.75; p < 0.01-0.05). All men sustained LT2 power output for 30 minutes, compared with 82% of women. Despite LT2 reflecting a similar heart rate, V[Combining Dot Above]O2, and [La] to those elicited during a 40-km time trial in both men and women, power output at LT2 was 6% higher (p < 0.05) than mean time trial power output in women, with no significant difference in men. Based on these findings, sex-specific recommendations have been suggested in regard to the use of LT2 for establishing performance potential, prescribing endurance training intensities and setting 40-km performance intensity.

Pacing and Performance in Swimming: Differences Between Individual and Relay Events.

PURPOSE: Although pacing is considered crucial for success in individual swimming events, there is a lack of research examining pacing in relays. The authors investigated the impact of start lap and pacing strategy on swimming performance and whether these strategies differ between relays and the corresponding individual event. METHODS: Race data for 716 relay (4 × 200-m freestyle) finals from 14 international competitions between 2010 and 2018 were analyzed retrospectively. Each swimmer's individual 200-m freestyle season's best time for the same year was used for comparison. Races were classified as a fast, average, or slow start lap strategy (lap 1) and as an even, negative, or positive pacing strategy (laps 2-4) to give an overall race strategy, for example, average start lap even pacing. RESULTS: A fast start lap strategy was associated with slower 200-m times (range 0.5-0.9 s, P ≤ .04) irrespective of gender, and positive pacing led to slower 200-m (0.4-0.5 s, P ≤ .03) times in females. A fast start lap strategy led to positive pacing in 71% of swimmers. Half of the swimmers changed pacing strategy, with 13% and 7% more female and male swimmers, respectively, displaying positive pacing in relays compared with individual events. In relays, a fast start lap and positive pacing was utilized more frequently by swimmers positioned on second to fourth relay legs (+13%) compared with lead-off leg swimmers (+3%). CONCLUSION: To maximize performance, swimmers should be more conservative in the first lap and avoid unnecessary alterations in race strategy in relay events.

Practice does not make perfect: A brief view of athletes' knowledge on the menstrual cycle and oral contraceptives.

OBJECTIVES: To assess the knowledge of Australian elite female athletes surrounding the menstrual cycle and oral contraceptives. DESIGN: Cross sectional survey. METHODS: Australian female athletes (n=189) representing their state and/or country in their respective sport completed a questionnaire comprising questions (multiple choice and short answer) relating to the menstrual cycle and oral contraceptives. A knowledge 'score' was calculated by allocating one point for each correct answer; the highest knowledge score that could be achieved was 14. Linear regression analysis was used to identify variables that were independently associated with menstrual cycle and oral contraceptive knowledge. RESULTS: Almost half (47.1 %) of the athletes surveyed were currently using hormonal contraception, the majority (75.3 %) of which used an oral contraceptive pill. Nevertheless, the mean knowledge score achieved by athletes on the questionnaire was 5.03±3.06, with only 8.5 % of athletes achieving a knowledge score of 10 or above. Hormonal contraceptive use and 'identifying as an individual athlete' were two factors that were significantly associated with overall knowledge score (p≤0.004), with current hormonal contraceptive users and individual athletes scoring 1.79 and 1.66 points on average higher than non-users and team sport athletes, respectively. CONCLUSIONS: Our findings indicate that knowledge surrounding the menstrual cycle and oral contraceptives was low in most elite athletes. Further education is warranted to enable athletes to make informed decisions regarding hormonal contraception, and any educational interventions should be implemented across all athlete groups.

Clinical Course of Motor Deficits from Lumbosacral Radiculopathy Due to Disk Herniation.

BACKGROUND: The clinical course of motor deficits from lumbosacral radiculopathy appears to improve with or without surgery. Strength measurements have been confined to manual muscle testing (MMT) and have not been extensively followed and quantified in prior studies. OBJECTIVE: To determine if motor weakness and patient-reported outcomes related to lumbosacral radiculopathy improve without surgical intervention over the course of 12 months. DESIGN: Prospective observational cohort. SETTING: Outpatient academic spine practice. PARTICIPANTS: Adults with acute radicular weakness due to disk herniation. METHODS: Forty patients with radiculopathy and strength deficit were followed over a 12-month period. Objective strength and performance tests as well as survey-based measurements were collected at baseline and then every 3 months. Patients underwent comprehensive pain management and rehabilitation and/or surgical approaches as determined in coordination with the treating specialist. This study was approved by the institutional review board of Colorado. MAIN OUTCOME MEASUREMENTS: Testing of strength was through MMT, handheld dynamometer, and performance-based testing. Furthermore, visual analog scale, modified Oswestry Disability Index, and 36-Item Short Form Health Survey (SF-36) were used to measure pain and disability outcomes. RESULTS: Of the 40 patients, 33 (82.5%) did not have surgery; 7 (17.5%) had surgery. Twenty-four of the 33 patients (60%) did not undergo surgery and were followed for 12 months (Comprehensive Pain Management and Rehabilitation, Complete [CPM&R-C]), and 9 (22%) did not have surgery and lacked at least one follow-up evaluation (Comprehensive Pain Management and Rehabilitation, Incomplete [CPM&R-I]). No statistically significant differences were found on baseline measures of strength deficits and SF-36 domains between the CPM&R-C, Surgery, and CPM&R-I groups. Pain and disability scores in the Surgery group were significantly higher than in the CPM&R-C at baseline. There were statistically significant improvements in all areas of strength, pain, and function when comparing measurements at the 12-month follow-up to baseline in the CPM&R-C group. CONCLUSIONS: Individuals with motor deficits due to lumbosacral radiculopathy improve over time regardless of treatment choice. Most did not choose surgery, and almost all of these patients regained full strength at 1 year. Strength recovery typically occurred in the first 3 months, but there was ongoing recovery over the course of a year. LEVEL OF EVIDENCE: II.

Can anti-gravity running improve performance to the same degree as over-ground running?

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 = 7) ran twice a week on an AG treadmill and once per week over-ground. The CON group (n = 8) completed all sessions OG on grass. Both AG and OG training resulted in similar improvements in time trial and shuttle run performance. Maximal running performance showed moderate differences between the groups, however the AG condition resulted in less improvement. Large differences in maximal blood lactate concentrations existed with OG running resulting in greater improvements in blood lactate concentrations measured during maximal running. Moderate increases in stride length paired with moderate decreases in stride rate also resulted from AG training. The use of AG training to supplement regular OG training for performance should be used cautiously, as extended use over long periods of time could lead to altered stride mechanics and reduced blood lactate.

Sizing Up Excitons in Core-Shell Quantum Dots via Shell-Dependent Photoluminescence Blinking.

Semiconductor nanocrystals or quantum dots (QDs) are now widely used across solar cell, display, and bioimaging technologies. While advances in multishell, alloyed, and multinary core-shell QD structures have led to improved light-harvesting and photoluminescence (PL) properties of these nanomaterials, the effects that QD-capping have on the exciton dynamics that govern PL instabilities such as blinking in single-QDs is not well understood. We report experimental measurements of shell-size-dependent absorption and PL intermittency in CdSe-CdS QDs that are consistent with a modified charge-tunnelling, self-trapping (CTST) description of the exciton dynamics in these nanocrystals. By introducing an effective, core-exciton size, which accounts for delocalization of charge carriers across the QD core and shell, we show that the CTST models both the shell-depth-dependent red-shift of the QD band gap and changes in the on/off-state switching statistics that we observe in single-QD PL intensity trajectories. Further analysis of CdSe-ZnS QDs, shows how differences in shell structure and integrity affect the QD band gap and PL blinking within the CTST framework.

PCNA ubiquitylation ensures timely completion of unperturbed DNA replication in fission yeast.

PCNA ubiquitylation on lysine 164 is required for DNA damage tolerance. In many organisms PCNA is also ubiquitylated in unchallenged S phase but the significance of this has not been established. Using Schizosaccharomyces pombe, we demonstrate that lysine 164 ubiquitylation of PCNA contributes to efficient DNA replication in the absence of DNA damage. Loss of PCNA ubiquitylation manifests most strongly at late replicating regions and increases the frequency of replication gaps. We show that PCNA ubiquitylation increases the proportion of chromatin associated PCNA and the co-immunoprecipitation of Polymerase δ with PCNA during unperturbed replication and propose that ubiquitylation acts to prolong the chromatin association of these replication proteins to allow the efficient completion of Okazaki fragment synthesis by mediating gap filling.

Velocity, Oxygen Uptake, and Metabolic Cost of Pull, Kick, and Whole-Body Swimming.

PURPOSE: The contributions of the limbs to velocity and metabolic parameters in front-crawl swimming at different intensities have not been identified considering 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 limbs only (kick) were compared with stroke and kick rate controlled. METHODS: Twenty elite swimmers completed six 200-m trials: 2 swim, 2 pull, and 2 kick. Swim trials were guided by underwater lights at paces equivalent to 65% ± 3% and 78% ± 3% of participants' 200-m-freestyle personal-best pace; paces were described as low and moderate, respectively. In the pull and kick trials, swimmers aimed to match the stroke and kick rates, respectively, recorded during the swim trials. V̇O2 was measured continuously, with velocity and metabolic cost calculated for each 200-m effort. RESULTS: The velocity contribution of the upper limbs (mean ± SD; low 63.9% ± 6.2%, moderate 59.6% ± 4.2%) was greater than that of the lower limbs to a large extent at both intensities (low ES = 4.40, moderate ES = 4.60). The V̇O2 used by the upper limbs differed between the intensities (low 55.5% ± 6.9%, moderate 51.4% ± 4.0%; ES = 0.74). The lower limbs were responsible for a greater percentage of the metabolic cost than the upper limbs at both intensities (low 56.1% ± 9.5%, ES = 1.30; moderate 55.1% ± 6.6%, ES = 1.55). CONCLUSIONS: Implementation of this testing protocol before and after a pull- or kick-training block will enable sport scientists to determine how the velocity contributions and/or metabolic cost of the upper- and lower-limb actions have responded to the training program.

Elite sprint swimming performance is enhanced by completion of additional warm-up activities.

This study investigated the effect of completing additional warm-up strategies in the transition phase between the pool warm up and the start of a race on elite sprint swimming performance. Twenty-five elite swimmers (12 men, 20 ± 3 years; 13 women, 20 ± 2 years, performance standard ~807 FINA2014 points) completed a standardised pool warm up followed by a 30-min transition phase and a 100-m freestyle time trial. During the transition phase, swimmers wore a tracksuit jacket with integrated heating elements and performed a dry land-based exercise routine (Combo), or a conventional tracksuit and remained seated (Control). Start (1.5% ± 1.0%, P = 0.02; mean ± 90% confidence limits) and 100-m time trial (0.8% ± 0.4%, P < 0.01) performances were improved in Combo. Core temperature declined less (-0.2°C ± 0.1°C versus -0.5°C ± 0.1°C, P = 0.02) during the transition phase and total local (trapezius) haemoglobin concentration was greater before the time trial in Combo (81 µM ± 25 µM versus 30 µM ± 18 µM, P < 0.01; mean ± standard deviation) than in Control. Combining swimmers traditional pool warm up with passive heating via heated jackets and completion of dry land-based exercises in the transition phase improves elite sprint swimming performance by ~0.8%.

The value of CT cardiac angiography and CT calcium score testing in a modern cardiology service in New Zealand: a report of a single centre eight-year experience from 5,237 outpatient procedures.

BACKGROUND: Computed tomographic (CT) cardiac angiography is of increasing value in several areas of patient management in cardiology. We assessed the ability of CT cardiac angiography to effectively 'rule out' severe coronary stenoses in patients presenting with 'atypical' symptoms and/or an equivocal stress test, which offers a new approach to the management of coronary artery disease. We also examined the use of the CT calcium score test in cardiovascular (CVS) risk assessment. METHODS: From a large single centre (Mercy Hospital) in Auckland, using a prospectively acquired, comprehensive database, we audited the entire eight-year experience of 5,169 patients (7/8/06 to 31/1/14) who underwent 5,237 64-slice computed tomographic (CT) cardiac angiogram or CT calcium score tests (GE Lightspeed scanner). RESULTS: From 5,169 patients there were 5,237 CT procedures. The mean patient age was 57 (SD 10) years; 42% patients were female. Of the 3,603 (69%) full CT cardiac angiogram scans, 3,509 (67%) included a calcium score test. One thousand four hundred and eighty-three (28%) of scans were a calcium score test only. Of the 3,603 (69%) full CT cardiac angiogram scans, it was possible to 'rule out' significant coronary atheroma (stenosis ≥50%) in 2,947 (82%) of these procedures. Of the 4,903 (94%) patients who had a CT calcium score test, in whom we could calculate the NZ Framingham-based CVS risk, it was possible to reassign 532 (22%) of these patients who were previously thought to be at 'low risk' to be at a higher CVS risk. CONCLUSION: CT cardiac angiography has become established in the modern management of cardiology patients. It has particular value as a tool to 'rule out' severe coronary stenoses, and as a tool to give a more accurate assessment of CVS risk. It adds significant value to the care of many patients within an established cardiology practice.

Velocity, aerobic power and metabolic cost of whole body and arms only front crawl swimming at various stroke rates.

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. METHODS: Twenty Australian national swimmers performed six 200 m front-crawl efforts under two conditions: (1) WB swimming and, (2) AO swimming. Participants completed the 200 m trials under three SR conditions: "low" (22-26 stroke-cycles min(-1)), "moderate" (30-34 stroke-cycles min(-1) and "high" (38-42 stroke-cycles min(-1)). [Formula: see text] was continuously measured, with C, velocity, SR, and kick rate calculated for each effort. RESULTS: Regardless of the SR condition and sex, AO velocity was consistently lower than WB velocity by ~11.0 % (p < 0.01). AO [Formula: see text] was lower than WB [Formula: see text] at all SR conditions for females (p < 0.01) and at the "high" SR for males (p < 0.01). C did not differ between WB and AO at any SR for both sexes (p > 0.01). When C was expressed as a function of velocity, WB and AO regression equations differed for males (p = 0.01) but not for females (p = 0.087). Kick rate increased as SR increased (p < 0.01), though the kick-to-stroke rate ratio remained constant. CONCLUSION: Elite swimmers gain ~11 % in velocity from their kick and, when used in conjunction with the arm stroke at the swimmers' preferred frequency, the metabolic cost of WB and AO swimming is the same. Coaches should consider these results when prescribing AO sets if their intention is to reduce the metabolic load.

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.

Salivary testosterone and cortisol responses to four different rugby training exercise protocols.

This study assessed the acute response of salivary testosterone and cortisol concentrations to four exercise protocols in 27 elite male rugby players. Each athlete completed four protocols in random order on separate in-season weeks. Two protocols were resistance training based consisting of four exercises (high pull, bench press, squat and chin-ups/prone row): Protocol 1 consisted of 5 sets of 15 repetitions at 55% of 1 repetition maximum (1 RM) with 1-minute rest (5 × 15-55%). Protocol 2 consisted of three sets of five repetitions at 85% 1 RM with 2-minute rest (3 × 5-85%). Protocol 3 was a strongman (STRNG) session consisting of three stations within a circuit of exercises that included exercises such as battling ropes, prowler push, farmer's walk and tyre flips. Protocol 4 was based on boxing and wrestling inspired exercises (combative--COMB). Salivary testosterone and cortisol concentrations were measured before (PRE) and immediately after exercise (POST). Testosterone did not significantly change as a result of any intervention, whereas cortisol declined and the testosterone to cortisol (T/C) ratio increased significantly in both the 5 × 15-55% and 3 × 5-85% protocol. When results were retrospectively grouped and analysed according to the protocol that demonstrated the greatest absolute testosterone response, significant (P < 0.01) increases for the 5 × 15-55%, STRNG and COMB protocols were observed. The individualised hormone response to exercise observed in this study highlights the importance of recognising a protocol-dependent approach to training athletes. Furthermore this study also highlights a potential usefulness of employing STRNG and COMB training protocols as an alternative stimulus to resistance training.

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.

Quantification of DNA-associated proteins inside eukaryotic cells using single-molecule localization microscopy.

Development of single-molecule localization microscopy techniques has allowed nanometre scale localization accuracy inside cells, permitting the resolution of ultra-fine cell structure and the elucidation of crucial molecular mechanisms. Application of these methodologies to understanding processes underlying DNA replication and repair has been limited to defined in vitro biochemical analysis and prokaryotic cells. In order to expand these techniques to eukaryotic systems, we have further developed a photo-activated localization microscopy-based method to directly visualize DNA-associated proteins in unfixed eukaryotic cells. We demonstrate that motion blurring of fluorescence due to protein diffusivity can be used to selectively image the DNA-bound population of proteins. We designed and tested a simple methodology and show that it can be used to detect changes in DNA binding of a replicative helicase subunit, Mcm4, and the replication sliding clamp, PCNA, between different stages of the cell cycle and between distinct genetic backgrounds.

The dose-response relationship between pseudoephedrine ingestion and exercise performance.

OBJECTIVES: The purpose of the present study was to examine a possible dose-response between pre-exercise pseudoephedrine intake and cycling time trial performance. DESIGN: Randomised, double-blind, crossover trial. METHODS: Ten trained male endurance cyclists (26.5 ± 6.2 years, 75.1 ± 5.9 kg, 70.6 ± 6.8 mL kg(-1)min(-1)) undertook three cycling time trials in which a fixed amount of work (7 kJ kg(-1) body mass) was completed in the shortest possible time. Sixty minutes before the start of exercise, subjects orally ingested either 2.3 mg kg(-1) or 2.8 mg kg(-1) body mass of pseudoephedrine or a placebo in a randomised and double-blind manner. Venous blood was sampled at baseline, pre- and post-warm up and post-exercise for the analysis of pH and lactate and glucose concentrations; plasma catecholamine and pseudoephedrine concentrations were measured at all times except post-warm up. RESULTS: Cycling time trial performance (∼ 30 min) was not enhanced by pseudoephedrine ingestion. Plasma pseudoephedrine concentration increased from pre-warm up to post-exercise in both treatment conditions, with the 2.8 mg kg(-1) body mass dose producing the highest concentration at both time points (2.8 mg kg(-1)>2.3 mg kg(-1)>placebo; p<0.001). CONCLUSIONS: There was large individual variation in plasma pseudoephedrine concentration between subjects following pseudoephedrine administration. A number of factors clearly influence the uptake and appearance of pseudoephedrine in the blood and these are not yet fully understood. Combined with subsequent differences in plasma pseudoephedrine between individuals, this may partially explain the present findings and also the inconsistencies in performance following pseudoephedrine administration in previous studies.