Search

A difficulty in identifying the optimal age, height, and body mass of swimmers is the heterogeneity of the athletes examined (i.e., gender, caliber), the variability in race distance and stroke, and the influence of time. Nonetheless, age, height, and body mass remains the most readily available data of all athlete characteristics, supporting their contribution to the prediction of performance. This review presents the findings of previous studies over the last 50 years and offers new insights by examining data from swimmers competing at the 1968, 1992, and 2016 Olympic Games. Our data investigates gender differences in age, before exploring gender-specific variations in the age, height, and body mass across year, distance, stroke, and caliber. We show that there are differences in swimmers competing at the 2016 compared to the 1968 and 1992 Olympic Games. Today the age of world-class swimmers is independent of gender, race distance and stroke, as well as caliber. Swimmers competing in freestyle are taller and heavier than in butterfly, while height remains associated with performance in some, but not all events in female swimmers. In 2016 the average age, height and body mass of World-class swimmers is 22.7 ± 3.6 and 23.2 ± 23.3 years, 175.1 ± 6.6 cm and 188.3 ± 6.0 cm and 63.8 ± 6.8 and 81.3 ± 7.3 kg for females and males respectively. These findings provide coaches with a new perspective on the optimal age, height, and body mass of world-class female and male swimmers.

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.

Pacing is arguably more crucial for optimal performance in swimming than in land-based sports, however little is known about the process of developing pacing skills in swimmers. The aim of this study was to examine the current practices of high-performance swimming coaches in relation to pacing entrainment and competition preparation. Twenty-one swimming coaches who were currently coaching or had coached swimmers at national open, international age or international open level, participated in a semi-structured interview. Interview transcripts were examined using hierarchical content (qualitative) analysis to identify general dimensions, higher-order themes and sub-themes. Data were categorised into two main areas: training and competition. The general dimensions of monitoring, pacing aids, periodisation and training for multiple events emerged within training; whereas optimal strategy, racing, warm up swims and multiple main events emerged within competition. Coaches identified the importance of a highly individualised approach based on swimmer needs and characteristics. However, the difficulty in achieving this goal when working with large groups of swimmers was identified as a challenge. Although swimming is a time-based sport, efficient technique and pacing were considered vital to success. Despite this, it appears that key variables including stroke rate, stroke count, split times and rating of perceived exertion were not monitored by a number of coaches. These parameters are likely important tools to maximise pacing skill development, especially in young swimmers. However, given the current lack of information on how athletes learn and develop pacing skills, coaches would benefit from evidence-based guidelines in this area.

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.

We investigate waveguide efficiency of CsPbI3 microwire waveguides and their photodegradation over a range of continuous wave laser excitation energies and intensities. Under modest laser input intensities

The perceptions of high-performance swimming coaches regarding the relative contribution of the upper and lower limbs are crucial in optimising athletic performance through subsequent prescription of training. Problematically, examination of these perspectives is lacking. To develop knowledge in this area, perceptions regarding the upper and lower limb velocity and metabolic contributions and reasoning surrounding whole body, arms-only and legs-only training prescription (referred to as swim, pull and kick, respectively) were garnered from seven male expert swimming coaches. The semi-structured interviews were transcribed verbatim by the lead researcher. Thematically analysed through open and axial-coding, results revealed that all coaches believed the upper limbs were the primary velocity generators but placed great importance on having well-conditioned muscles of the lower limbs. All coaches identified multiple interrelated parameters contributing to velocity generation and metabolic cost. In a typical training week, coaches allocate, on average, 58% (40–85%), 19% (0–30%) and 22% (10–40%) of the total training volume to swim, pull and kick training, respectively. All training prescription was based on anecdotal evidence and personal experience. Considering the variability in training allocation reported by these high-performance coaches, sport scientists and developmental coaches are encouraged to understand how factors such as the distance specialisation of the swimmers, injury status, stroke technique and physiological conditioning status of the upper and lower limb muscles influence the prescription of swim, pull and kick training within a typical training season.

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.

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.

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.

Hoffmann, SM, Skinner, TL, van Rosendal, SP, Osborne, MA, Emmerton, LM, and Jenkins, DG. The efficacy of the lactate threshold: A sex-based comparison. J Strength Cond Res XX(X): 000-000, 2018-The second lactate threshold (LT2) has previously been associated with endurance performance; however, comparisons between sexes are lacking regarding its 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.

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 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.

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.

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.

Photoluminescent quantum dots are used in a range of applications that exploit the unique size tuneable emission, light harvesting and quantum efficient properties of these semiconductor nanocrystals. However, optical instabilities such as photoluminescence intermittency, the stochastic switching between bright, emitting states and dark states, can hinder quantum dot performance. Correlations between this blinking of emission and the dielectric properties of the nanoenvironment between the quantum dot interface and host medium, suggest surface ligands play a role in modulating on-off switching rates. Here we elucidate the nature of the cadmium selenide nanocrystal surface, by combining magic angle spinning NMR and x-ray photoelectron spectroscopy to determine ligand surface densities, with molecular dynamics simulation to assess net ligand filling at the nanocrystal interface. Results support a high ligand coverage and are consistent with photoluminescence intermittency measurements that indicate a dominant contribution from surface ligand to the dielectric properties of the local quantum dot environment. Photoluminescent quantum dots are an important technology but can exhibit undesirable intermittent quenching of the photoluminescence. Here, a combination of NMR techniques with XPS and simulations are used to describe the surface coverage of ligands on CdSe nanoparticles and to relate the blinking dynamics to the local dielectric environment.

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.

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.

PRITCHARD-PESCHEK, K. R., M. A. OSBORNE, G. J. SLATER, D. R. TAAFFE, and D. G. JENKINS. Pseudoephedrine and Preexercise Feeding: Influence on Performance. Med. Sci. Sports Exerc., Vol. 45, No. 6, pp. 1152-1157, 2013. Purpose: This study examined the influence of preexercise food intake on plasma pseudoephedrine (PSE) concentrations and subsequent high-intensity exercise. In addition, urinary PSE concentrations were measured under the same conditions and compared with the present threshold of the World Anti-Doping Agency (WADA). Methods: Ten highly trained male cyclists and triathletes (age = 30.6 T 6.6 yr, body mass (BM) = 72.9 T 5.1 kg, and VO2max = 64.8 T 4.5 mLIkg j1 Imin j1 ; mean T SD) undertook four cycling time trials (TT), each requiring the completion of a set amount of work (7 kJIkg j1 BM) in the shortest possible time. Participants were randomized into a fed or nonfed condition and orally ingested 2.8 mgIkg j1 BM of PSE or a placebo (PLA) 90 min before exercise; in the fed trials, they consumed a meal providing 1.5 gIkg j1 BM of CHO. Venous blood was sampled at 30, 50, and 70 min and pre-warm-up and postexercise for the analysis of plasma PSE and catecholamine concentrations, and urine was also collected for the analysis of PSE concentration. Results: Inde- pendent of the preexercise meal, 2.8 mgIkg j1 BM of PSE did not significantly improve cycling TT performance. The fed trials resulted in lower plasma PSE concentrations at all time points compared with the nonfed trials. Both plasma epinephrine and blood lactate concentrations were higher in the PSE compared with the PLA trials, and preexercise and postexercise urinary PSE concentrations were significantly higher than the threshold (150 KgImL j1 ) used by WADA to determine illicit PSE use. Conclusion: Irrespective of the preexercise meal, cycling TT performance of approximately 30 min was not improved after PSE supplementation. Furthermore, 2.8 mgIkg j1 BM of PSE taken 90 min before exercise, with or without food, resulted in urinary PSE concentrations exceeding the

The present study evaluated what are considered common and contentious differences in paddling technique within the surfing population, across the three distinct categories of: 1) Paddle Stroke length (Reach); 2) Torso Inclination (Chest Position); and 3) Arm Recovery. To assess the differences among paddling techniques, this study employed a within-subjects comparison of sprint paddling kinematic performance differences. Twenty competitive male surfers (19.1±6.8 years, 168.2±11.3 cm, 61.7±13.6 kg) performed 2 maximal trials each of Long vs. Short Reach, Chest Up vs. Down Position, and High vs. Low Arm Recovery during 15 m sprint paddle trials. The sprint paddle efforts were initiated from a stationary, prone lying position, using a horizontal position transducer attached to the rear waistline of each subjects' board-shorts such that kinematic data was obtained for 5 m, 10 m, and 15 m distances, and peak paddling velocity determined. There was no difference observed between Short and Long paddle strokes for any of the distance intervals, nor for peak paddling velocity (p>0.05). For chest position, the Down condition was found to be faster than the Chest Up position for all criterion variables (p=0.01–0.05), with moderate magnitude (d=0.25–0.43). The Low Arm Recovery resulted in superior performance compared to the High Arm Recovery (p=0.02–0.04), with low and moderate magnitudes (d=0.19–0.47). Sprint paddling is likely best conducted with the surfer's chest low to the board, without considerable extension through the back, and with a low arm recovery.

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., Author summary PCNA is a homotrimeric complex that clamps around the DNA to provide a sliding platform for DNA polymerases and other replication and repair enzymes. The covalent modification of PCNA by ubiquitin on lysine reside 164 has been extensively studied in the context of DNA repair: it is required to mediate the bypass of damaged template bases during DNA replication. Previous work has shown that PCNA is modified by ubiquitin during normal S phase in the absence of DNA damage, but the significance of this modification has not been explored. Here we show that, in addition to regulating bypass of damaged bases, lysine 164 ubiquitylation plays a role in ensuring the completion of unperturbed DNA replication.

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%.

Understanding instabilities in the photoluminescence (PL) from light emitting materials is crucial to optimizing their performance for different applications. Semiconductor quantum dots (QDs) offer bright, size tunable emission, properties that are now being exploited in a broad range of developing technologies from displays and solar cells to biomaging and optical storage. However, instabilities such as photoluminescence intermittency, enhancement and bleaching of emission in these materials can be detrimental to their utility. Here, we report dielectric dependent blinking, intensity-"spikes" and low-level, "grey"-state emission, as well as PL enhancement in ZnS capped CdSe QDs; observations that we found consistent with a charge-tunnelling and self-trapping (CTST) description of exciton-dynamics on the QD-host system. In particular, modulation of PL in grey-states and PL enhancement are found to have a common origin in the equilibrium between exciton charge carrier core and surface-states within the CTST framework. Parameterized in terms of size and electrostatic properties of the QD and its nanoenvironment, the CTST offers predictive insight into exciton-dynamics in these nanomaterials.

VAN ROSENDAL, S. P., N. A. STROBEL, M. A. OSBORNE, R. G. FASSETT, and J. S. COOMBES. Performance Benefits of Rehydration with Intravenous Fluid and Oral Glycerol. Med. Sci. Sports Exerc., Vol. 44, No. 9, pp. 1780-1790, 2012. Purpose: Intravenous (IV) saline has been used by athletes attempting to accelerate rehydration procedures. The diuresis from IV rehydration may be circumvented through the concomitant use of oral glycerol. We aimed to examine the effects of rehydrating with four different regimens of IV fluid and oral glycerol on subsequent 40-km cycling time trial performance. Methods: Nine endurance-trained men were dehydrated by 4% bodyweight via exercise in the heat. They then rehydrated with 150% of the fluid lost via four protocols using a randomized crossover design: 1) oral = sports drink and water; 2) oral glycerol = sports drink, water, and glycerol; 3) IV = half as normal saline, half of sports drink, and water, and 4) IV with oral glycerol = half as normal saline, half as sports drink, water, and glycerol. After this, they completed a 40-km cycling performance test in the heat. Results: Compared with oral rehydration, there were significant performance benefits (P < 0.05) when rehydrating with oral glycerol (improved time to complete 40 km by 3.7%), IV (3.5%), and IV with oral glycerol (4.1%). Plasma volume restoration was highest in IV with oral glycerol, then IV, then oral glycerol, then oral (P < 0.01 for all of these comparisons). There were no differences in HR, tympanic/skin temperatures, sweat rate, blood lactate concentration, thermal stress, or RPE between groups. Conclusions: Combining IV fluid with oral glycerol resulted in the greatest fluid retention; however, it did not improve exercise performance compared with either modality alone.

This study demonstrates that petroleum and source rocks are enriched in Pt and Pd to the ppb level, and that the 187Os/188Os composition coupled with the Pt/Pd value permits the fingerprinting of petroleum to its source. Oils from the United Kingdom Atlantic Margin (sourced from the Upper Jurassic Kimmeridge Clay Fm.) as well as source rock samples have been analysed for Pt and Pd. When the Pt/Pd value is compared with 187Os/188Os (calculated at the time of oil generation; Osg) the values from both the known source and the oils are similar, demonstrating that they can be used as an oil to source fingerprinting tool. This inorganic petroleum fingerprinting tool is particularly important in heavily biodegraded petroleum systems where traditional fingerprinting techniques (e.g. biomarkers) are severely hampered, e.g. the world's largest oil sand deposit, the West Canadian Oil Sands (WCOS). This has caused the source of the WCOS to be hotly debated, with no present day consensus between inputs from potential source units e.g. Exshaw and Gordondale Fms. 187Os/188Os and Pt/Pd fingerprinting of the oil sands shows that the majority of the petroleum have similar 187Os/188Os and Pt/Pd values, supporting the hypothesis of one principal source. Analysis of the potential source rocks establishes that the principal source of the oil sands to be from the Jurassic Gordondale Fm., with a minor Exshaw Fm. input. Thus, the combination of previously pioneered Re–Os petroleum geochronology with 187Os/188Os and Pt/Pd values of petroleum permits both a temporal and spatial understanding of petroleum systems.

Semiconductor nanocrystals or quantum dots (QDs) exhibit a number of unique optical properties including fluorescence intermittency (FI), photoluminescence (PL) enhancement, and darkening. Here we report PL activation (PLA) and darkening over populations of single colloidal ZnS-capped CdSe QDs under continuous illumination, which is described well by a simple consecutive elementary reaction (CER) scheme in the 1 to 10 kW cm(-2) excitation intensity regime. The scheme allows determination of rate constants for both fluorescence activation and decay processes as well as the measurement of initial bright, fluorescent and dark, nonfluorescent QD fractions. The latter parameters can function as a "quality control" on the total population of detectable QDs in an imaging experiment or a synthesis. We further show reversible PLA at low intensities0.5 kW cm(-2) and a photoinduced conditioning of the QD that results in increased rates of PLA following repeated cycles of illumination and an induction period that precedes photoactivation upon initial exposure to light. By interrogating individual QD fluorescence trajectories, the population fractions found exclusive to each of three illumination cycles, common to any two cycles and fluorescent in all three cycles, show that only a small number of QDs (∼5%) remain fluorescent through multiple cycles of photoactivation and recovery.

In the present study, 200-m swim time in highly trained male swimmers was measured on two consecutive days (Trial 1 and Trial 2) and under three conditions [(1) acute loading, AcL; (2) chronic loading, ChL; (3) Placebo, PLA]. No sodium bicarbonate (NaHCO(3)) was administered between Trial 1 and Trial 2 under each condition. Blood lactate concentration ([La(-)]), base excess of extracellular fluid (BE(ecf)), plasma bicarbonate concentration ([HCO(3) (-)]) and pH were determined before and after capsule administration as well as at 0, 3, 5, 15 and 30 min after each 200-m swim trial. Swim time was not different among AcL, ChL or PLA for Trial 1 or 2 and we observed no change in 200-m swim time from Trial 1 to 2 under any condition (F = 0.48, P = 0.80). [HCO(3) (-)], pH and BE(ecf) measured after capsule administration was higher during AcL and ChL when compared with PLA (P0.05). We did not observe any difference in blood [La(-)] between the three conditions at any stage post-exercise (P0.05). The results indicate that acute and chronic loading of NaHCO(3) does not improve 200-m swim time in highly trained male swimmers.

We demonstrate that the Re-Os system can be used to understand the temporal evolution of a petroleum system as well as aid in the identification of source units. Traditional geochemical methods (high-performance liquid chromatography, carbon isotope, gas chromatography, and biomarker analysis) indicate that the main source of 18 oils analyzed for Re-Os geochronology from the United Kingdom Atlantic margin (Clair, Schiehallion, Cuillin, and Foinaven fields) is Late Jurassic marine shales. This is supported by the Os isotopic composition ( 187 Os/ 188 Os) of the Late Jurassic source (∼0.9–2.4) at the timing of oil generation being similar to that of the oil (68 Ma; 0.92–1.12), indicating that the Re-Os system can potentially be used to fingerprint the source of an oil. The Re-Os data for the 18 oils yield an age (68 ± 13 Ma) that agrees with both the relative (basin models) and absolute (Ar-Ar geochronology) timing of oil generation, indicating that that Re-Os oil geochronology records oil generation events.

The objective of this paper is to measure the clinical course (months) in young athletes with persistent fatigue and to identify any covariates affecting the duration of recovery. This was a prospective longitudinal study of 68 athletes; 87% were elite (42 males, 26 females), aged 20.5±3.74 years (SD), who presented with the symptom of persistent fatigue. The collective duration to full clinical recovery was estimated using Kaplan-Meier product-limit curves, and covariates associated with prolonging recovery were identified from Cox proportional hazard models. The median recovery was 5 months (range 1-60 months). The range of presenting symptom duration was 0.5-36 months. The covariates identified were an increased duration of presenting symptoms [hazard ratio (HR), 1.06; 95% confidence interval (CI), 1.02-1.12; P=0.005] and the response of serum cortisol concentration to a standard exercise challenge (HR, 1.92; 95% CI, 1.09-3.38; P=0.03). Delay in recovery was not associated with categories of fatigue that included medical, training-related diagnoses, or other causes. In conclusion, the fatigued athlete represents a significant clinical problem with a median recovery of 5 months, whose collective clinical course to recovery can be estimated by Kaplan-Meier curves and appears to be a continuum.

187 Os/ 188 Os, as expected from a Kimmer- idge Clay Formation source. However, oils from the Viking Graben, with which the Brent fi eld is associated, and main East Shetland Basin display unradiogenic 187 Os/ 188 Os. In this study we seek to demonstrate that these anomalous results are due to interaction with a mantle-like fl uid that propagated through the main fault zone of the Viking Graben and East Shetland Basin. This study enhances our understanding of the Re-Os oil systematics, and supports cur- rent ideas regarding fault architecture, crustal thinning, and associated fl uid fl ow and interac- tion in the North Sea oil system. ABSTRACT United Kingdom North Sea oils sourced from the Kimmeridge Clay Formation contain unradiogenic (~0.17 to ~0.48) and radiogenic (~1.04 to ~3.34) 187 Os/ 188 Os values. The unra- diogenic 187 Os/ 188 Os values are spatially associated with the main basin-bounding faults of the Viking Graben and East Shetland Basin. In contrast, the radiogenic 187 Os/ 188 Os values are associated with North Sea basins located farther away from the basin boundary faults. We suggest that crustal thinning and strain localization within the Viking Graben and East Shetland Basin are suffi cient to have allowed basin-bounding faults to propagate to suffi cient depth to act as conduits for mantle-derived fl uids to interact with oil. This hypothesis is sup- ported by previous geochemical data for North Sea oil fi elds. Furthermore, we demonstrate the use of Os isotopes as an important tracker of crustal-scale fl uid dynamics and petroleum migration pathways in extensional basins.

The aim of the current study was to investigate the effect of 180 mg of pseudoephedrine (PSE) on cycling time-trial (TT) performance. Six well-trained male cyclists and triathletes (age 33 ± 2 yr, mass 81 ± 8 kg, height 182.0 ± 6.7 cm, VO2max 56.8 ± 6.8 ml ⋅ kg−1 ⋅ min−1; M ± SD) underwent 2 performance trials in which they completed a 25-min variable-intensity (50–90% maximal aerobic power) warm-up, followed by a cycling TT in which they completed a fixed amount of work (7 kJ/kg body mass) in the shortest possible time. Sixty minutes before the start of exercise, they orally ingested 180 mg of PSE or a cornstarch placebo (PLA) in a randomized, crossover, double-blind manner. Venous blood was sampled immediately pre- and postexercise for the analysis of pH plus lactate, glucose, and norepinephrine (NE). PSE improved cycling TT performance by 5.1% (95% CI 0–10%) compared with PLA (28:58.9 ± 4:26.5 and 30:31.7 ± 4:36.7 min, respectively). There was a significant Treatment × Time interaction (p = .04) for NE, with NE increasing during the PSE trial only. Similarly, blood glucose also showed a trend (p = .06) for increased levels postexercise in the PSE trial. The ingestion of 180 mg of PSE 60 min before the onset of high-intensity exercise improved cycling TT performance in well-trained athletes. It is possible that changes in metabolism or an increase in central nervous system stimulation is responsible for the observed ergogenic effect of PSE.

Dehydration in athletes alters cardiovascular and thermoregulatory function and may inhibit endurance exercise capacity if fluid loss exceeds 2% of bodyweight (BW). If this level of dehydration cannot be prevented when starting from a state of euhydration, then athletes may create a state of hyperhydration by consuming extra fluid prior to exercise. From this hyperhydrated situation, individuals have a greater capacity to tolerate fluid loss before becoming dehydrated. Furthermore, excess pre-exercise fluid intake enhances thermoregulatory ability, as well as increasing plasma volume to maintain cardiac output. However, hyperhydrating before exercise is difficult, because a large fluid intake is typically accompanied by diuresis. Glycerol-containing beverages create an osmotic gradient in the circulation favouring fluid retention, thereby facilitating hyperhydration and protecting against dehydration. Many studies have shown that increases in body water by 1 L or more are achievable through glycerol hyperhydration. This article analyses the evidence for glycerol use in facilitating hyperhydration and rehydration, and provides guidelines for athletes wishing to use this compound. An analysis of the studies in this area indicates that endurance athletes intending to hyperhydrate with glycerol should ingest glycerol 1.2 g/kg BW in 26 mL/kg BW of fluid over a period of 60 minutes, 30 minutes prior to exercise. The effects of glycerol on total body water when used during rehydration are less well defined, due to the limited studies conducted. However, ingesting glycerol 0.125 g/kg BW in a volume equal to 5 mL/kg BW during exercise will delay dehydration, while adding glycerol 1.0 g/kg BW to each 1.5 L of fluid consumed following exercise will accelerate the restoration of plasma volume. Side effects from glycerol ingestion are rare, but include nausea, gastrointestinal discomfort and light-headedness. In summary, glycerol ingestion before, during or following exercise is likely to improve the hydration state of the endurance athlete.

Studies have shown that beverages containing glycerol can enhance and maintain hydration status and may improve endurance exercise performance by attenuating adverse physiological changes associated with dehydration. Improvements to performance include increased endurance time to exhaustion by up to 24%, or a 5% increase in power or work. However, some studies have found no performance benefits during either prolonged exercise or specific skill and agility tests. In studies that have shown benefits, the improvements have been associated with thermoregulatory and cardiovascular changes. These include increased plasma volume and sweat rates, as well as reduced core temperature and ratings of perceived exertion. In a very small number of subjects, glycerol consumption has been associated with side-effects including nausea, gastrointestinal discomfort, dizziness, and headaches. In summary, while glycerol and fluid ingestion results in hyperhydration, the documented benefits to exercise performance remain inconsistent.

The offshore Indus Basin is a rift and passive margin basin offshore Pakistan and northwest India. Rifting associated with break up of the India/Madagascar/Seychelles plates began during the Late Cretaceous and was accompanied by a major period of volcanism associated with the Deccan volcanic event. A major volcanic centre was located along the south of the basin adjacent to the Saurashtra Arch transform fault and resulted in the deposition of up to 7 km of extrusive basalts interbedded with Late Cretaceous–Paleocene marine sediments. The basalts show stacked prograding reflection patterns on seismic data. A chain of northeast–southwest-trending volcanic seamounts in the central part of the deep-water basin formed topographic highs for the development of shallow-water carbonates during the Eocene post-rift phase. The passive margin stratigraphy includes up to 9 km of Oligocene–Recent age clastic sediments from the Indus River system. The proximal part of the Indus Fan contains spectacular large-scale channel-levees in the Miocene and Plio-Pleistocene intervals. Fourteen major channel-levee systems have been identified in the Plio-Pleistocene and represent potential reservoir targets. Trap types include extensional rollover anticlines at the shelf edge, drape structures over the Eocene carbonate highs, stratigraphic traps along the Murray Ridge and folds associated with strike-slip faults along the Murray Ridge. A key challenge for future exploration is to determine whether source rocks are present in sufficient quality for commercial discoveries.

Purpose:The present investigation examined the physiological and performance effects of lower-body compression garments (LBCG) during a one-hour cycling time-trial in well-trained cyclists.Methods:Twelve well-trained male cyclists ([mean ± SD] age: 20.5 ± 3.6 years; height: 177.5 ± 4.9 cm; body mass: 70.5 ± 7.5 kg; VO2max: 55.2 ± 6.8 mL·kg−1·min−1) volunteered for the study. Each subject completed two randomly ordered stepwise incremental tests and two randomly ordered one-hour time trials (1HTT) wearing either full-length SportSkins Classic LBCG or underwear briefs (control). Blood lactate concentration ([BLa−]), heart rate (HR), oxygen consumption (VO2) and muscle oxygenation (mOxy) were recorded throughout each test. Indicators of cycling endurance performance were anaerobic threshold (AnT) and VO2max values from the incremental test, and mean power (W), peak power (W), and total work (kJ) from the 1HTT Magnitude-based inferences were used to determine if LBCG demonstrated any performance and/or physiological benefits.Results:A likely practically significant increase (86%:12%:2%; η2 = 0.6) in power output at AnT was observed in the LBCG condition (CONT: 245.9 ± 55.7 W; LBCG: 259.8 ± 44.6 W). Further, a possible practically significant improvement (78%:19%:3%; η2 = 0.6) was reported in muscle oxygenation economy (W·%mOxy−1) across the 1HTT (mOxy: CONT: 52.2 ± 12.2%; LBCG: 57.3 ± 8.2%).Conclusions:The present results demonstrated limited physiological benefits and no performance enhancement through wearing LBCG during a cycling time trial.

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.

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 ( $$ \dot{V}{\text{O}}_{2} $$ ) and metabolic cost (C) between whole body (WB) and arms only (AO) front-crawl swimming across various intensities while controlling SR. 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). $$ \dot{V}{\text{O}}_{2} $$ was continuously measured, with C, velocity, SR, and kick rate calculated for each effort. Regardless of the SR condition and sex, AO velocity was consistently lower than WB velocity by ~11.0 % (p

The purpose of this study was to determine whether muscle glycogen reduction prior to exercise would alter muscle fibre recruitment pattern and change either on-transient O2 uptake ( ) kinetics or the slow component. Eight recreational cyclists ( , 55.6 ± 1.3 ml kg −1 min−1) were studied during 8 min of heavy constant-load cycling performed under control conditions (CON) and under conditions of reduced type I muscle glycogen content (GR). was measured breath-by-breath for the determination of kinetics using a double-exponential model with independent time delays. was higher in the GR trial compared to the CON trial as a result of augmented phase I and II amplitudes, with no difference between trials in the phase II time constant or the magnitude of the slow component. The mean power frequency (MPF) of electromyography activity for the vastus medialis increased over time during both trials, with a greater rate of increase observed in the GR trial compared to the CON trial. The results suggest that the recruitment of additional type II motor units contributed to the slow component in both trials. An increase in fat metabolism and augmented type II motor unit recruitment contributed to the higher in the GR trial. However, the greater rate of increase in the recruitment of type II motor units in the GR trial may not have been of sufficient magnitude to further elevate the slow component when was already high and approaching .

Single-molecule orientational imaging using total internal reflection fluorescence microscopy has been employed to investigate the dynamics of a protein-ligand system. Emission patterns from single tetramethylrhodamine (TMR)-biocytin molecules bound to streptavidin show that the TMR dipole adopts a limited number of favored orientations. The angular trajectories of individual dipoles exhibit remarkably similar patterns that are characteristic of single TMR molecules interacting with a relatively homogeneous population of nanoenvironments. Analysis of the polar and azimuthal angle distributions reveals a tendency for the dipole to assume three primary and two secondary orientations. Autocorrelation analysis of the dipole trajectories shows a predominantly bimodal behavior in the reorientation rates with the slow and fast components corresponding to the primary and secondary orientations, respectively. A number of mechanisms by which the observed orientations might be stabilized have been considered, in particular specific interactions between the zwitterionic TMR probe and charged residues on the streptavidin surface. Variations in the reorientation rates have been discussed in terms of local thermal fluctuations in the protein.

Molecular simulations and an inherent structure analysis are used to investigate how the response of a glass to stress depends on its thermal history. Although the stress response at low and high strains is independent of the thermal history of the glass, the stress response at intermediate strains depends strongly on the thermal history. Previous experiments and simulations have shown that the peak stress, defined as the maximum stress the system can withstand before flowing, increases as a glass is annealed. The present inherent structure analysis addresses this phenomenon. The present results show that as glasses are strained, more highly annealed glasses remain in their initial metabasin up to larger strains (and thus larger stresses). This greater stress-absorbing capacity of the metabasins that characterize more highly annealed systems allows the more annealed systems to withstand more stress before flowing.

We describe a rapid, accurate method for calculating rovibrational distributions in diatomic products from elementary chemical reactions. The basis of the model is momentum interconversion at a critical configuration defined in terms of molecular dimensions of the species involved. This approach shares common elements with recent models of inelastic processes and the kinematic reactive model of Elsum and Gordon. We point out that these and related approaches represent a development of Newtonian mechanics equivalent to that followed in the conventional formulation of classical mechanics, but one in which motive force for change at the molecular level is attributed to dp/dt rather than to dV/dq. This leads to a particularly transparent form of mechanics that uses only familiar data such as bond length, mass, spectroscopic constants, and velocity, yet may be applied to the highly resolved single collision experiments of molecular reaction dynamics. We describe key aspects of the computational method, e.g., the definition of the critical configuration, the disposal of reaction enthalpy, the manner of assigning product vibrational states, and the way in which conservation of energy is ensured. Examples are chosen to illustrate the range of reactions to which the method may be applied. Each would represent a challenge to conventional theory. We show that velocity-angular momentum diagrams may be used to interpret data and to give physical insight into the origins of observed rotational distributions. Good agreement is obtained between experimental and calculated (v,j) distributions for a wide range of elementary reactions suggesting that our model, despite its simplicity, captures the principal physics of chemical change at the molecular level.

The roots of a polynomial can be represented as points in the complex plane. The time value of money (TVM) equation that is commonly used in finance is a polynomial equation. (See the appendix for a short description of the TVM equation and an example of its use in finance.) In [1] and [2] it is shown that concepts from financial mathematics can be obtained from the pattern of the roots of the TVM equation. The concepts are given in terms of distances between the roots and other salient points in the plane. This note shows that this particular polynomial, and the technique, can be applied more generally. When a series of data is fed into the coefficients of the polynomial, the mean and standard deviation of the data are seen in the complex plane as combinations of distances between the roots and other salient points. The results are aesthetically pleasing as well as mathematically interesting.

The aim of this study was to compare accumulated oxygen deficit data derived using two different exercise protocols with the aim of producing a less time-consuming test specifically for use with athletes. Six road and four track male endurance cyclists performed two series of cycle ergometer tests. The first series involved five 10 min sub-maximal cycle exercise bouts, a VO2peak test and a 115% VO2peak test. Data from these tests were used to estimate the accumulated oxygen deficit according to the calculations of Medbø et al. (1988). In the second series of tests, participants performed a 15 min incremental cycle ergometer test followed, 2 min later, by a 2 min variable resistance test in which they completed as much work as possible while pedalling at a constant rate. Analysis revealed that the accumulated oxygen deficit calculated from the first series of tests was higher (P0.02) than that calculated from the second series: 52.3 +/- 11.7 and 43.9 +/- 6.4 ml x kg(-1), respectively (mean +/- s). Other significant differences between the two protocols were observed for VO2peak, total work and maximal heart rate; all were higher during the modified protocol (P0.01 and P0.02, respectively). Oxygen kinetics were also significantly faster during the modified 2 min maximal test. We conclude that the difference in accumulated oxygen deficit between protocols was probably due to a reduced oxygen uptake, possibly caused by a slower oxygen on-response during the 115% VO2peak test in the first series, and VO2-power output regression differences caused by an elevated VO2 during the early stages of the second series.

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 (V̇O2max) and speed at V̇O2max, 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.

We have employed single molecule fluorescence spectroscopy, using a total internal reflection geometry and wide-angle detection, to study the attachment of singly fluorescently labeled DNA to a silica surface by either a streptavidin−biotin or a covalent linkage. In both cases the DNA is highly monodispersed with no evidence for aggregation. The covalent coupling gave higher signal-to-noise than the streptavidin−biotin linkage and was therefore studied in more detail. Two components in the photobleaching times, corresponding to different states of the tetramethyl rhodamine probe, were observed: a short and long component with populations in the ratio 6.7:1. Only rarely was interconversion between these two states detected during the 30-s observation time of the experiment. Hybridization experiments using a complementary strand of DNA labeled with a different fluorophore gave a low level of colocalized fluorescence, indicating a significant fraction of the surface attached DNA was not available for hybrid...