Time Performance Research Articles

Modelling performance by continents in swimming.

Introduction: There is a growing interest in the scientific community about the progression and congruity in the performance of talented participants who complete representing different nations in the most important international events. The prediction of incoming performances is nowadays in demand with the objective of returning in talent investment. Talent identification programs have tried to select and develop sports talent over years. However, to our knowledge, there is a lack of research about success in swimming World Championships (WCs) performance considering continents-country and how successful outcomes are influenced by these variables. Therefore, the primary goal is to analyze the effect of early specialization comparing the performance progression model of the countries gathered by continents. Methods: Participant's data from all Junior and Senior WCs between 2006 and 2017 from International Swimming Federation (FINA). One-way ANOVA, ANCOVA and regression model were used to explain whether the variable category, age, best z-score, experience, and continent influences the performance obtained in Absolute WC. Results: Significant differences (p < 0.01) were found between the average performance obtained by the two different categories (junior: swimmers participating in junior WCs before senior WCs; senior: swimmers participating in senior WCs without previous participation in junior WCs), where swimmers from category junior showed significant better performance's times than seniors, except in America. ANCOVA results showed that generally, the greatest differences where in the earliest ages, with best performance registered in category junior in all the continents. Also, the experience was a significant variable in the general model. Conclusion: Swimmers who had participated in junior category prior absolute obtained better performance's times than those swimmers who participated directly in absolute, in the first participation in senior WC. Thus, early specialization is a key factor to obtain better results in senior WCs for all the continents, except in America.

1006 Supersized-Simulation vs Traditional Cardiothoracic Surgery Education: A Prospective, Randomised Controlled Trial

Abstract Aim Exposure to cardiothoracic surgery is limited during medical school in the United Kingdom. This study evaluated the effectiveness of a supersized simulation model (SSM) compared to traditional methods (TM) in developing coronary anastomosis surgical skills. Method This was a prospective, randomised controlled trial with a 1:1 allocation ratio. Undergraduate medical students with no prior cardiothoracic surgical skills training were eligible for inclusion. Both groups received a guided didactic lecture followed by modified Objective Structured Assessment of Technical Skills (OSATS) assessment for baseline. The control group then received traditional teaching and the intervention group received additional teaching with SSM before being reassessed. Modified OSATS score were the primary outcome, adjudicated by two senior cardiothoracic registrars. Performance time (PT), self-assessment (SA), confidence (CON) and global rating scale (GRS) were secondary outcomes. Results 48 novice medical students were randomised. OSATS scores were significantly higher in SSM group compared to TM group (13.2 vs 9.8, p&amp;lt;0.01). The secondary outcomes PT (17.7 minutes vs 22.2 minutes, p&amp;lt;0.01) and CON (3.04 vs 1.73, p&amp;lt;0.01) were also significantly different between groups, favouring SSM. SSM participants were more likely to want to pursue a career in cardiothoracic surgery (12 participants vs 2 participants). All participants agreed that SSM improved visualisation and comprehension of surgical procedure. SSM cost £0.75 per model. Conclusions Supersized simulation is effective for coronary anastomosis surgical training with technical skills successfully transferred to a clinical task. Supersized models can accelerate the novice trainee's surgical skill progression and represents a valuable resource in one's educational armamentarium.

Time and Cost Estimation of Pre-Fabrication Construction by Using ANN

Abstract: The ANN has received a lot of attention recently because of its ability to tackle both quantitative and qualitative challenges in the building sector. This paper proposes using the ANN to forecast the Cost Performance (CP) and Time Performance (TP) of the prefabrication process in a building project. In this case, various percentages of prefabrication contents are added to the building, and estimated duration, real duration, estimated cost, and actual cost are utilised as inputs to the ANN process. Keywords: Time and cost estimation, ANN, construction, pre-fabrication

Biomechanical Associates of Performance and Knee Joint Loads During A 70-90° Cutting Maneuver in Subelite Soccer Players.

McBurnie, AJ, Dos'Santos, T, Jones, PA. Biomechanical associates of performance and knee joint loads during a 70-90° cutting maneuver in subelite soccer players. J Strength Cond Res 35(11): 3190-3198, 2021-The aim of this study was to explore the "performance-injury risk" conflict during cutting, by examining whole-body joint kinematics and kinetics that are responsible for faster change-of-direction (COD) performance of a cutting task in soccer players, and to determine whether these factors relate to peak external multiplanar knee moments. 34 male soccer players (age: 20 ± 3.2 years; body mass: 73.5 ± 9.2 kg; height: 1.77 ± 0.06 m) were recruited to investigate the relationships between COD kinetics and kinematics with performance and multiplanar knee joint moments during cutting. Three-dimensional motion data using 10 Qualisys Oqus 7 infrared cameras (240 Hz) and ground reaction force data from 2 AMTI force platforms (1,200 Hz) were collected to analyze the penultimate foot contact and final foot contact (FFC). Pearson's or Spearman's correlations coefficients revealed performance time (PT), peak external knee abduction moment (KAM), and peak external knee rotation moment (KRM) were all significantly related (p < 0.05) to horizontal approach velocity (PT: ρ = -0.579; peak KAM: ρ = 0.414; peak KRM: R = -0.568) and FFC peak hip flexor moment (PT: ρ = 0.418; peak KAM: ρ = -0.624; peak KRM: ρ = 0.517). Performance time was also significantly (p < 0.01) associated with horizontal exit velocity (ρ = -0.451) and, notably, multiplanar knee joint loading (peak KAM: ρ = -0.590; peak KRM: ρ = 0.525; peak KFM: ρ = -0.509). Cohen's d effect sizes (d) revealed that faster performers demonstrated significantly greater (p < 0.05; d = 1.1-1.7) multiplanar knee joint loading, as well as significantly greater (p < 0.05; d = 0.9-1.2) FFC peak hip flexor moments, PFC average horizontal GRFs, and peak knee adduction angles. To conclude, mechanics associated with faster cutting performance seem to be "at odds" with lower multiplanar knee joint loads. This highlights the potential performance-injury conflict present during cutting.

Sodium bicarbonate supplementation does not improve elite women's team sport running or field hockey skill performance.

Team sports, such as field hockey, incorporate high‐intensity repeated sprints, interspersed with low‐intensity running, which can result in acidosis. The aim of the present study was to examine the effect of acute sodium bicarbonate (SB) supplementation on team sport running and skill performance. Eight elite female field hockey players (age 23 ± 5 years, body mass 62.6 ± 8.4 kg, height 1.66 ± 0.05 m) completed three Field Hockey Skill Tests (FHST) interspersed with four sets of the Loughborough Intermittent Shuttle Test (LIST). Prior to exercise, participants were supplemented with capsules equivalent to 0.2 g·kg−1 body mass (BM) of a placebo (maltodextrin) or 0.3 g·kg−1 BM SB. Field hockey skill performance incorporated overall performance time (PFT), movement time (MT), decision‐making time (DMT), and penalty time (PT). Sprint time (ST), rating of perceived exertion (RPE), blood lactate concentration, bicarbonate anion (HCO3−) concentration, pH, and base excess were measured at various time points. Data (mean ± SD) were analyzed using a two‐way analysis of variance (ANOVA) with repeated measures, with Hedges g effect sizes used to interpret the magnitude of differences. Bicarbonate anion concentration (+5.4 ± 2.6 mmol·L−1) and pH (+0.06 ± 0.03) were greater during the bicarbonate trial compared with the placebo (P < 0.001). Bicarbonate did not alter PFT (placebo: 87.9 ± 6.9 sec; bicarbonate: 89.0 ± 7.8 sec, P = 0.544, g = 0.14), MT, DMT, PT (all P > 0.30) or ST (placebo: 2.87 ± 0.12 sec; bicarbonate: 2.86 ± 0.12 sec, P = 0.893, g = −0.08). RPE was lower during the SB condition (placebo: 13 ± 2; bicarbonate: 12 ± 2, P = 0.021, g = −0.41). Acute ingestion of bicarbonate did not improve sprint or sport‐specific skill performance. Bicarbonate ingestion did result in a lower perception of effort during team‐sport running, which may have performance implications in a competitive match situation.

New Procedural Path for F&B Operation and Its Risk Impact on a Nuclear Power Plant

Although a feed and bleed (F&B) operation is an important emergency task having a significant effect on the risk of a pressurized water reactor–type nuclear power plant, there is a high uncertainty regarding its modeling and analysis in a probabilistic safety assessment (PSA). This paper introduces a study on the design of an operational strategy for an F&B operation based on human reliability analysis (HRA) with plant-specific thermal-hydraulic (TH) and human performance time (PT) analyses. The emergency operating procedures (EOPs) of a reference plant were modified by adding a new procedural path for the F&B operation to reduce its effect on the plant’s risk. To support the modification of the procedure, an intensive TH analysis was conducted to evaluate the plant’s behavior in diverse accident conditions and to revise the success criteria for the HRA of the F&B operation. In addition, an empirical analysis of PT required to carry out the F&B operation was conducted based on plant-specific simulator records. The PSA model of the reference plant was revised by reflecting the modified EOPs and new success criteria for the HRA of the F&B operation, which showed that core damage frequency of the revised PSA was about 50% lower than that of the original PSA.

Is sodium a good hyperhydration strategy in 10k runners?

The objective of the present study was to evaluate the effect of pre-exercise hyperhydration with sodium (PEHS), on the state of hydration and performance in runners of a 10K. Ten male runners (age 40.5 ± 9.7 yrs, weight 72.5 ± 8.4 kg, body fat 18.8 ± 4.5%) participated in the study and performed 10 km of street running under two different forms of prehydration: pre-exercise hydration (PEH), consisting of water intake ad libitum, and pre-exercise sodium hyperhydration (PEHS), consisting of sodium ingestion (12 mg of sodium for each 5 mL of water) diluted 1 h before the test. The variables evaluated were heart rate (HR), body temperature (BT), body mass (BM), blood pressure (BP), relative dehydration (RD), absolute dehydration (AD), total ingested water (TH2OING), degree of dehydration (DD), sweating rate (SR), specific gravity of urine (SGU), urine pH, and performance time (PT). There was no difference between intervention groups in the variables HR, BT, BM, BP, SGU, urine pH, and PT. RD (0.76 ± 0.41 kg vs. 1.16 ± 0.43 kg; Cohen’s d = 0.95; p = 0.042); AD (0.63 ± 0.36 kg vs. 0.99 ± 0.43 kg; Cohen’s d = 0.90; p = 0.038); DD (0.63 ± 0.52% vs. 1.35 ± 0.56%; Cohen’s d = 1.33; p = 0.009); SR (2255.03 ± 1297.25 mL vs. 3550.06 ± 1527.35 mL; Cohen’s d = 0.91; p = 0.048) were lower in the state of PEHS. PEH presented greater TH2OING (0.16 ± 0.12 mL vs. 0.34 ± 0.41 mL; Cohen’s d = 0.59; p = 0.008). It was concluded that PEHS produces better hydration in runners during long distance running.

The effects of multiple firefighting activities on information processing and work performance in a smoke‐diving room: An intervention study

AbstractFirefighters perform various tasks during firefighting operations under unknown and unpredictable conditions. The present study investigated the impact of firefighting activities and cooling tactics on information processing and work performance. Firefighters performed typical firefighting tasks in the four experimental conditions, namely i) no cooling device (NC), ii) cooling gel (CG), iii) cool vest (CV), and iv) cooling gel and cool vest (CG + CV). The measurement of information processing, Paced Auditory Serial Addition Test (PASAT) scores decreased significantly after the firefighting activities in the four conditions, relative to baseline. The results revealed no significant difference in PASAT scores among the four conditions. However, the performance time (PT) was significantly shorter for the CV and CG + CV compared to the NC and CG conditions. The findings confirmed that the firefighting activities have a detrimental effect on information processing. The CG + CV and CV were more effective than CG and NC in improving PT during firefighting. However, the cooling strategies have a negligible effect on improving information processing performance.

Surgical performance of large loop excision of the transformation zone in a training model: A prospective cohort study.

Large loop excision of the transformation zone (LLETZ) is one of the most common procedures in operative gynecology and it is a routine part of the surgical training program of residents. There is, however, no established and standardized method of teaching residents how to perform LLETZ. Here, we present a surgical training model and assessed the improvement of surgical skills during repeated hands-on trainings of LLETZ in this model.Surgical novices and experts were recruited and were shown a LLETZ training video and then performed 3 LLETZ training sessions on consecutive days. Surgical skills were assessed by Objective Structured Assessment of Technical Skills (OSATS). Global rating scale (GRS), confidence (CON), fragmentation rate (FR), performance time (PT), and OSATS scores were calculated. Intra- and interobserver variabilities were determined. The construct validity of OSATS was assessed comparing metric scores of novices with those of experts.Sixty-eight probands (58 novices, 10 experts) were recruited. GRS, 2.3 ± 1.3 (median ± SD) versus 1.4 ± 0.6, P < .001; CON, 2.7 ± 0.9 versus 1.6 ± 0.6, P < .001; FR, 81% versus 100%, P < .001; PT, 152 ± 33 versus 120 ± 27 seconds, P = .006; and OSATS scores, 18.8 ± 1.3 versus 19.1 ± 1.1, P = .16 of novices improved from session 1 to session 3. OSATS showed construct validity with metric scores (GRS, 1.1 ± 0.3 vs 2.3 ± 0.8, P < .001; CON, 1.0 ± 0.0 vs 2.7 ± 0.9, P < .001; PT 125 ± 30 vs 152 ± 33 seconds, P = .02; OSATS scores, 19.6 ± 0.7 vs. 18.8 ± 1.3, P = .02) reliably discriminating between experts and novices. Intra- and interobserver variabilities across probands were 0.99 ± 0.03 and 0.64 ± 0.10, respectively. OSATS scores were independent of handedness, sex, and regular sports activity in univariate and multivariate analyses.Repeated hands-on trainings improve surgical performance of LLETZ in a surgical training model with construct validity.

Evaluation of a 7-Gene Genetic Profile for Athletic Endurance Phenotype in Ironman Championship Triathletes.

Polygenic profiling has been proposed for elite endurance performance, using an additive model determining the proportion of optimal alleles in endurance athletes. To investigate this model’s utility for elite triathletes, we genotyped seven polymorphisms previously associated with an endurance polygenic profile (ACE Ins/Del, ACTN3 Arg577Ter, AMPD1 Gln12Ter, CKMM 1170bp/985+185bp, HFE His63Asp, GDF8 Lys153Arg and PPARGC1A Gly482Ser) in a cohort of 196 elite athletes who participated in the 2008 Kona Ironman championship triathlon. Mean performance time (PT) was not significantly different in individual marker analysis. Age, sex, and continent of origin had a significant influence on PT and were adjusted for. Only the AMPD1 endurance-optimal Gln allele was found to be significantly associated with an improvement in PT (model p = 5.79 x 10−17, AMPD1 genotype p = 0.01). Individual genotypes were combined into a total genotype score (TGS); TGS distribution ranged from 28.6 to 92.9, concordant with prior studies in endurance athletes (mean±SD: 60.75±12.95). TGS distribution was shifted toward higher TGS in the top 10% of athletes, though the mean TGS was not significantly different (p = 0.164) and not significantly associated with PT even when adjusted for age, sex, and origin. Receiver operating characteristic curve analysis determined that TGS alone could not significantly predict athlete finishing time with discriminating sensitivity and specificity for three outcomes (less than median PT, less than mean PT, or in the top 10%), though models with the age, sex, continent of origin, and either TGS or AMPD1 genotype could. These results suggest three things: that more sophisticated genetic models may be necessary to accurately predict athlete finishing time in endurance events; that non-genetic factors such as training are hugely influential and should be included in genetic analyses to prevent confounding; and that large collaborations may be necessary to obtain sufficient sample sizes for powerful and complex analyses of endurance performance.

Utility and feasibility of integrating pulse oximetry into the routine assessment of young infants at primary care clinics in Karachi, Pakistan: a cross-sectional study.

BackgroundHypoxemia may occur in young infants with severe acute illnesses or congenital cardiac anomalies, but is not reliably detected on physical exam. Pulse oximetry (PO) can be used to detect hypoxemia, but its application in low-income countries has been limited, and its feasibility in the routine assessment of young infants (aged 0–59 days) has not been previously studied. The aim of this study was to characterize the operational feasibility and parent/guardian acceptability of incorporating PO into the routine clinical assessment of young infants in a primary care setting in a low-income country.MethodsThis was a cross-sectional study of 862 visits by 529 infants at two primary care clinics in Karachi, Pakistan (March to June, 2013). After clinical assessment, oxygen saturation (Sp02) was measured by a handheld PO device (Rad-5v, Masimo Corporation) according to a standardized protocol. Performance time (PT) was the time between sensor placement and attainment of an acceptable PO reading (i.e., stable SpO2 + 1 % for at least 10 s, heart rate displayed, and adequate signal indicators). PT included the time for one repeat attempt at a different anatomical site if the first attempt did not yield an acceptable reading within 1 min. Parent/guardian acceptability of PO was based on a questionnaire and unprompted comments about the procedure. All infants underwent physician assessment.ResultsAcceptable PO readings were obtained in ≤1 and ≤5 min at 94.4 % and 99.8 % of visits, respectively (n = 862). Median PT was 42 s (interquartile range 37; 50). Parents/guardians overwhelmingly accepted PO (99.6 % overall satisfaction, n = 528 first visits). Of 10 infants with at least one visit with Sp02 <92 % on a first PO attempt, 3 did not have a significant acute illness on physician assessment. There were no PO-related adverse events.DiscussionUsing a commercially available handheld pulse oximeter, acceptable Sp02 measurements were obtained in nearly all infants in under 1 minute. The procedure was readily integrated into existing assessment pathways and parents/guardians had positive views of the technology.ConclusionsWhen incorporated into routine clinical assessment of young infants at primary care clinics in a low-income country, PO was feasible and acceptable to parents/guardians. Future research is needed to determine if the introduction of routine PO screening of young infants will improve outcomes in low-resource settings.

Imputation of Missing Values in Daily Wind Speed Data Using Hybrid AR-ANN Method

Wind speed data collection process faces several problems as failure of data observing devices. Therefore, windspeed data naturally contains missing values. Imputing these missing values using an effective method isimportant before performing time series analysis. The classical methods as linear, nearest neighbor, and statespace may not provide accurate imputations when the wind speed contains nonlinearity. In this study, the hybridartificial neural network (ANN) and autoregressive (AR) method is proposed for imputing the missing values.ANN is a nonlinear method that is capable of imputing the missing values in wind speed data with nonlinearcharacteristic. AR model is used for determining the structure of the input layer for the ANN. Listwise deletion isused before AR modeling to handle the missing values. A case study is carried out using daily Iraqi andMalaysian wind speed data. The proposed imputation method is compared with linear, nearest neighbor, andstate space methods. The comparison has shown that AR-ANN outperformed the classical methods. Inconclusion, the missing values in wind speed data with nonlinear characteristic can be imputed more accuratelyusing AR-ANN. Therefore, imputing the missing values using AR-ANN leads to more accurate performance oftime series modeling and analysis.

Objective Structured Assessment of Technical Skills (OSATS) evaluation of hysteroscopy training: a prospective study

ObjectivesTo describe the performance curve of hysteroscopy-naïve probands repeatedly working through a surgery algorithm on a hysteroscopy trainer. Study designWe prospectively recruited medical students to a 30min demonstration session teaching a standardized surgery algorithm. Subjects subsequently performed three training courses immediately after training (T1) and after 24h (T2) and 48h (T3). Skills were recorded with a 20-item Objective Structured Assessment of Technical Skills (OSATS) at T1, T2, and T3. The presence of a sustained OSATS score improvement from T1 to T3 was the primary outcome. Performance time (PT) and self assessment (SA) were secondary outcomes. Statistics were performed using paired T-test and multiple linear regression analysis. Results92 subjects were included. OSATS scores significantly improved over time from T1 to T2 (15.21±1.95 vs. 16.02±2.06, respectively; p<0.0001) and from T2 to T3 (16.02±2.06 vs. 16.95±1.61, respectively; p<0.0001). The secondary outcomes PT (414±119s vs. 357±88s vs. 304±91s; p<0.0001) and SA (3.02±0.85 vs. 3.80±0.76 vs. 4.41±0.67; p<0.0001) also showed an improvement over time with quicker performance and higher confidence. SA, but not PT demonstrated construct validity. In a multiple linear regression analysis, gender (odds ratio (OR) 0.96; 95% confidence interval (CI) 0.35–2.71; p=0.9) did not independently influence the likelihood of OSATS score improvement. ConclusionsIn a hysteroscopy-naïve population, there is a continuous and sustained improvement of surgical proficiency and confidence after multiple training courses on a hysteroscopy trainer. Serial hysteroscopy trainings may be helpful for teaching hysteroscopy skills.

Objective Structured Assessment of Technical Skills (OSATS) evaluation of theoretical versus hands-on training of vaginal breech delivery management: a randomized trial

ObjectiveTo compare the skills of performing a vaginal breech (VB) delivery after hands-on training versus demonstration. Study designWe randomized medical students to a 30-min demonstration (group 1) or a 30-min hands-on (group 2) training session using a standardized VB management algorithm on a pelvic training model. Subjects were tested with a 25 item Objective Structured Assessment of Technical Skills (OSATS) scoring system immediately after training and 72h thereafter. OSATS scores were the primary outcome. Performance time (PT), self assessment (SA), confidence (CON), and global rating scale (GRS) were the secondary outcomes. Statistics were performed using the Mann–Whitney U-test, chi-square test, and multiple linear regression analysis. Results172 subjects were randomized. OSATS scores (primary outcome) were significantly higher in group 2 (n=88) compared to group 1 (n=84) (21.18±2.29 vs. 20.19±2.37, respectively; p=0.006). The secondary outcomes GRS (10.31±2.28 vs. 9.17±2.21; p=0.001), PT (214.60±57.97s vs. 246.98±59.34s; p<0.0001), and CON (3.14±0.89 vs. 2.85±0.90; p=0.04) were also significantly different between groups, favoring group 2. After 72h, primary and secondary outcomes were not significantly different between groups. In a multiple linear regression analysis, group assignment (odds ratio [OR] 1.60; 95% confidence interval [CI] 1.14–2.05; p<0.0001) and gender (OR 2.91; 95% CI 2.45–3.38; p<0.0001) independently influenced OSATS scores. ConclusionHands-on training leads to a significant improvement of VB management in a pelvic training model, but this effect was only seen in the short term.

Effects of Liquid Cooling Garments on Recovery and Performance Time in Individuals Performing Strenuous Work Wearing a Firefighter Ensemble

This study investigated the effects of body cooling using liquid cooling garments (LCG) on performance time (PT) and recovery in individuals wearing a fully equipped prototype firefighter ensemble (PFE) incorporating a self-contained breathing apparatus (SCBA). Six healthy male participants (three firefighters and three non-firefighters) completed six experimental sessions in an environmental chamber (35°C, 50% relative humidity), consisting of three stages of 15 min exercise at 75% VO2max, and 10 min rest following each exercise stage. During each session, one of the following six conditions was administered in a randomized order: control (no cooling, CON); air ventilation of exhaust SCBA gases rerouted into the PFE (AV); top cooling garment (TCG); TCG combined with AV (TCG+AV); a shortened whole body cooling garment (SCG), and SCG combined with AV (SCG+AV). Results showed that total PT completed was longer under SCG and SCG+AV compared with CON, AV, TCG, and TCG+AV (p < 0.01). Magnitude of core temperature (Tc) elevation was significantly decreased when SCG was utilized (p < 0.01), and heart rate recovery rate (10 min) was enhanced under SCG, SCG+AV, TCG, and TCG+AV compared with CON (p < 0.05). Estimated Esw rate (kg·h−1) was the greatest in CON, 1.62 (0.37), and the least in SCG+AV 0.98 (0.44): (descending order: CON > AV > TCG = TCG+AV > SCG > SCG+AV) without a statistical difference between the conditions (p < 0.05). Results of the present study suggest that the application of LCG underneath the PFE significantly improves the recovery during a short period of rest and prolongs performance time in subsequent bouts of exercise. LCG also appears to be an effective method for body cooling that promotes heat dissipation during uncompensable heat stress.

Reproducibility of Physiological Measures in Protective Ensemble User Performance Testing

The firefighter protective ensemble (PE), including Self-Contained Breathing Apparatus (SCBA), provides the wearer protection from hazardous environments, but increases physiological burden due to the additional weight and thermoregulatory challenges. User performance testing can be used to determine the level of physiological stress caused by the PE. PURPOSE: To examine the reproducibility of physiological variables in subjects performing repeated PE performance testing. METHODS: Ten healthy subjects (7 males and 3 females) participated in two repeated sessions of an exercise protocol involving treadmill exercise at 50% VO2max in an environmental chamber (22°C, 50% relative humidity) while wearing a standard firefighter PE with SCBA. Physiological responses in measurements included core temperature (Tc), skin temperature (Tsk), heart rate (HR), sweat rate (SR), and performance time (PT). The measured variables were analyzed in terms of within-subjects and between-sessions by performing Pearson's correlations and paired samples t-test, respectively. RESULTS: All subjects completed two sessions while potential confounding variables such as hydration, circadian rhythms, etc were carefully controlled to be as identical as possible. The results showed that mean change (Δ) per min were: Tc: 0.021 (0.005), 0.021 (0.008) °C, ΔTsk: 0.113 (0.029), 0.116 (0.039) °C, ΔHR:2.9 (0.8), 3.0 (0.9), SR: 1.31 (0.52), 1.17 (0.38) kg/h, and PT: 28.8 (8.1), 28.5 (7.9) min, (session 1, 2) respectively. The measured variables found to be significantly highly correlated were Tc (r=0.649), Tsk (r=0.691), and HR (r=0.679). While there was no statistical difference in any variable analyzed for between-sessions, it was noted that a few subjects showed about 20-30% difference in PT between the two sessions. CONCLUSION: Physiological responses, as indexed by Tc, Tsk, and HR, in PE user performance testing were highly reproducible and variations in the measurements between the two repeated sessions were not statistically meaningful at the controlled experimental conditions. Factor(s) influencing the differences in PT observed in a few subjects was not clear, but elevation in body temperature did not seem to be responsible in the present study when considering Tc and Tsk.

Effects Of Cooling On Performance Time And Recovery In Individuals Wearing A Prototype Firefighter Ensemble

While providing protection in hazardous environments, a firefighter ensemble (FE) contributes to the development of uncompensable heat stress due to high clothing insulation and the reduction in evaporative heat loss. Prolonged exposure to heat stress increases the risk of overexertion and heat illness in firefighters and reduces the performance time (PT) and rate of recovery even at low work intensity. PURPOSE: The purpose of this study was to investigate the effects of body cooling (BC) by utilizing water (conductive) cooled garments on PT and recovery in individuals exercising while wearing a prototype FE (PFE). METHODS: Six male subjects completed three randomly assigned exercise sessions in an environmental chamber (35 °C, 50% relative humidity) while wearing a PFE under control (CON; no cooling) or two cooling conditions: a top (head, neck, forearms) cooling garment (TCG) or a whole body cooling garment (CG); at water inlet temperature (Tin) of 18 °C. The treadmill walking protocol consisted of 3 stages of 15 min exercise at 75% VO2max, and 3 stages of 10 min rest following each exercise stage. Each stage of exercise was stopped if the subjects reached 90% of HRmax or requested to stop. Core and skin temperatures, and heart rate (HR) were measured pre, during, and post session, and PT was recorded. RESULTS: The results showed that PT for CG was 13.5 and 12.8 min longer than CON and TCG (p≤ 0.05), respectively, while thermal strain on HR (DHRt=HRendrecovery -HR0) in CON was 14.7 and 26.8 (beats/min) greater than TCG and CG (p≤ 0.01), respectively. The rate of increase (total change divided by PT) in mean body temperature (Tb) was also significantly less in CG than either CON or TCG (p≤ 0.05). CONCLUSIONS: The results of this study suggest that the application of a BC garment prolongs performance duration and improves the recovery time of individuals working in this PFE. These results also suggest that conductive BC was effective in promoting heat dissipation from the body while wearing the PFE and mitigated a level of uncompensable heat stress. In addition, the study also showed that the BC on a greater body surface area (CG) better suppressed elevation in Tb and elicited a longer PT than cooling on a limited area (TCG). However, the optimal level of cooling needed to support firefighting activities is not conclusive in this study.