Work-rest Ratio Research Articles

Creatinine clearance is maintained in a range of wet-bulb globe temperatures and work-rest ratios during simulated occupational heat stress.

We tested the hypothesis that compliance with the National Institute for Occupational Safety and Health (NIOSH) heat stress recommendations will prevent reductions in glomerular filtration rate (GFR) across a range of wet-bulb globe temperatures (WBGTs) and work-rest ratios at a fixed work intensity. We also tested the hypothesis that noncompliance would result in a reduction in GFR compared with a work-rest matched compliant trial. Twelve healthy adults completed five trials (four NIOSH compliant and one noncompliant) that consisted of 4 h of exposure to a range of WBGTs. Subjects walked on a treadmill (heat production: approximately 430 W) and work-rest ratios (work/h: 60, 45, 30, and 15 min) were prescribed as a function of WBGT (24°C, 26.5°C, 28.5°C, 30°C, and 36°C), and subjects drank a sport drink ad libitum. Peak core temperature (TC) and percentage change in body weight (%ΔBW) were measured. Creatinine clearance measured pre- and postexposure provided a primary marker of GFR. Peak TC did not differ among NIOSH-compliant trials (P = 0.065) but differed between compliant versus noncompliant trials (P < 0.001). %ΔBW did not differ among NIOSH-compliant trials (P = 0.131) or between compliant versus noncompliant trials (P = 0.185). Creatinine clearance did not change or differ among compliant trials (P ≥ 0.079). Creatinine clearance did not change or differ between compliant versus noncompliant trials (P ≥ 0.661). Compliance with the NIOSH recommendations maintained GFR. Surprisingly, despite a greater heat strain in a noncompliant trial, GFR was maintained highlighting the potential relative importance of hydration.NEW & NOTEWORTHY We highlight that glomerular filtration rate (GFR) is maintained during simulated occupational heat stress across a range of total work, work-rest ratios, and wet-bulb globe temperatures with ad libitum consumption of an electrolyte and sugar-containing sports drink. Compared with a work-rest matched compliant trial, noncompliance resulted in augmented heat strain but did not induce a reduction in GFR likely due to an increased relative fluid intake and robust fluid conservatory responses.

Violation of Allowable Work Intensity does not Augment Acute Kidney Injury Risk During Simulated Occupational Heat Stress

We recently demonstrated that violation of the National Institute of Occupational Safety and Health (NIOSH) heat stress recommendations by exceeding the allowable wet bulb globe temperature (WBGT) for a given moderate work intensity and work:rest ratio augmented acute kidney injury (AKI) risk. However, the role of work intensity (at a fixed work:rest ratio) on AKI risk during NIOSH compliant and non-compliant scenarios remains largely unknown. This study tested the hypothesis that violating the NIOSH recommendations by exceeding the allowable work intensity at a given WBGT and fixed work:rest ratio would augment AKI risk. Twelve healthy adults completed two NIOSH recommendation compliant trials and one noncompliant trial consisting of a 4 h exposure to a fixed WBGT and work intensity. Work-rest ratio was fixed at 30 min of walking and 30 min of rest each hour. Work intensity (i.e., Hprod) was prescribed as a function of WBGT— 412±51 W (27.3±0.3°C; high intensity compliant [Chigh]), 290±75 W (31.6±0.2°C; low intensity compliant [Clow]), and 410±61 W (31.7±0.2°C; high intensity noncompliant [NChigh]). All subjects were provided 237 mL of sport drink every 15 min and drank ad libitum. TC is presented as peak across the 4 h exposure. Urine samples were collected preexposure, and immediately and 1 h postexposure. Urinary inflammatory (monocyte chemotactic protein-1 [MCP-1]), oxidative stress (thioredoxin 1 [TRX-1]), and AKI risk (the product of insulin-like growth factor-binding protein 7 and tissue inhibitor of metalloproteinase 2 [IGFBP7·TIMP-2]) biomarkers were measured and normalized to urine flow rate. Urinary biomarkers were log transformed before statistical analysis and data are presented as mean ± SD. Peak Tc was higher during the NChigh trial (38.3±0.4°C) compared to the compliant trials (Chigh: 38.0±0.3°C; Clow: 37.8±0.4°C; p≤0.0095). Body weight change from pre- to postexposure did not differ between trials (p=0.7817). MCP-1 increased from pre- to immediately postexposure in all trials (p≤0.0031) but was not different between trials (p=0.1354). TRX-1 increased from pre- to immediately postexposure in all trials (p≤0.0085) but was not different between trials (p=0.6372). [IGFBP7·TIMP-2] increased from pre- to immediately postexposure in all trials (p=0.0454) but the increase was not different between trials (Chigh: -1.7±2.6 LOG [ng/mL2]/1000; Clow: -1.6±2.4 LOG [ng/mL2]/1000; NChigh:-1.2±2.3 LOG [ng/mL2]/1000; p=0.2076). Simulated occupational heat stress elevates AKI risk, likely due to both inflammation and oxidative stress. Violating the NIOSH recommendations by exceeding either the allowable WBGT (i.e., NChigh versus Chigh) or work intensity (i.e., NChigh versus Clow) resulted in a modest elevation in peak Tc but did not modify AKI risk and/or the urinary inflammatory and oxidative stress responses. RCT: NCT04767347; Supported By: R01OH011528. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A Systematic Review on the Physical, Physiological, Perceptual, and Technical-Tactical Demands of Official 3 × 3 Basketball Games.

To systematically review the physical, physiological, perceptual, and technical-tactical demands of official 3 × 3 basketball games. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines were followed. Three electronic databases (PubMed, Scopus, and Web of Science) were systematically searched to identify studies assessing physical, physiological, perceptual, and technical-tactical demands of 3 × 3 games. Data were also coded according to player sex and tournament phase. Quality assessment of the included studies was performed using a modified Downs and Black checklist. Thirteen articles were finally included, with a mean quality of 8.6 (1.1) out of 11. Three-by-three basketball games have an intermittent profile (1:1 work-rest ratio), with a duration of ∼15minutes, and are characterized by short (6-8s) ball possessions and considerable physical (17-33 accelerations, 24-44 decelerations, 62-94 changes of directions, and 17-24 jumps per game) and physiological (lactate: ∼6.2mmol·L-1) demands. Overall, the game performance profile is similar in males and females, with minor changes happening across tournament phases. Several key technical-tactical indicators were identified as discriminating winning and losing teams, such as better shooting and defensive efficiency, low number of turnovers, and implementing tactical actions involving more players, passing first, and ending possessions with shots from outside of the arch from the top of the key. Three-by-three basketball is an intermittent, physically demanding sport characterized by quick plays and specific tactical constraints. This review provides information that should be considered by performance staff to improve training prescription, game tactical plans, and for player selection and talent identification.

Occupational Heat Stress Recommendation Compliance Attenuates AKI Risk Compared with a Work-Rest Ratio-Matched, Positive Control Scenario.

Key Points Occupational heat stress recommendations attenuate AKI risk compared with a work–rest ratio–matched positive control scenario.Heat-induced AKI risk is strongly related to peak core temperature.The peak change in serum creatinine largely paralleled peak changes in urinary [insulin-like growth factor-binding protein 7·tissue inhibitor metalloproteinase 2].

АНАЛИЗ ДОРОЖНО-ТРАНСПОРТНОГО ТРАВМАТИЗМА НА ОБЩЕСТВЕННОМ ТРАНСПОРТЕ В РЕСПУБЛИКЕ ТАТАРСТАН ЗА 2018-2022 гг.

Report. Introduction. Road traffic accidents involving passenger transport vehicles are characterized by highly severe consequences and usually cause massive public outcry. Major accidents involving public transport occur infrequently, but they are always characterized by many victims, injured and dead. Aim of this paper is to study the injury degree of road traffic accidents involving passenger transport vehicles, such as buses, trolleybuses, or trams. Materials and Methods. The study is based on the data made available via the federal statistical observation over road accidents involving motor and public transport in the Republic of Tatarstan over the years 2018-2022. For this purpose, we used generalization methods and quantitative, qualitative, and comparative analysis techniques. Mathematical simulation techniques were used to analyze the data with the computational tools of the MS Excel electronic package. Необходимо повышение осведомленности пассажиров о правилах безопасности и процедурах эвакуации в случае чрезвычайного проис- шествия. Results and Discussion. An acute problem of modern society is the lack of effectively ensuring passenger transport safety, which leads to more frequent road accidents and injuries on the roads. Transporting passengers by urban public transport is one of the most important industries in the economy of the Republic of Tatarstan. Road safety issues are a priority in many strategic and program documents of the socio-economic development of the Republic. Human factor is one of the key factors in ensuring road safety. The most common causes of such accidents are speed limit violations and drivers’ inattention and negligence. Eventually, drivers’ failure to comply with the work-rest ratio leads to accidents and loss of life. There is a need for raising passengers’ awareness of safety rules and emergency evacuation procedures. Conclusions. There are still serious shortcomings in traffic management, leading to accidents with many dead and injured. Implementing measures aimed at preventing road accidents will help enhance road safety and significantly reduce the number of accidents.

Recovery time variation during sprint interval training impacts amateur soccer players adaptations - a pilot study.

The objective of the present study was to investigate the selected performance adaptations of amateur soccer players to 2 different running-based sprint interval training (SIT) protocols with different recovery intervals and work-rest ratios (1:5 & 1:1). Twenty-three subjects (age 21.4 ± 1.1 years; height 175.4 ± 4.7 cm; body mass 69 ± 6.4 kg) participated in the study. Before the 6-weeks training period, participants completed 3-weeks of low-intensity training preparation. Subsequently, the pre-tests (anthropometric measurements, repeated sprint test [12 × 20-m with 30-s recovery intervals], Yo-YoIRT1 & Yo-YoIRT2 and treadmill VO2max test) were conducted. Thereafter, participants were randomly divided into 3 sub-groups (1 - SIT with 150 s recovery intervals [SIT150, n = 8]; 2 - SIT with 30 s recovery intervals [SIT30, n = 7]; and 3 - control group [CG, n = 8]). SIT150 and SIT30 training groups completed sprint interval training (2-days/week; 30-s all-out running, 6-10 repetition with 150 s recovery intervals for SIT150 and 30 s for SIT30 groups, respectively), a soccer match (1-day) and routine soccer training (3-days) per week. The CG attended only routine training sessions and the soccer-match (4-days). The study experiments and the trainings were conducted during off-season. Yo-YoIRT1, Yo-YoIRT2, and VO2max were significantly improved both in SIT30 and SIT150 (p < 0.05) groups. Yo-YoIRT1 and VO2max were also significantly improved in CG (p < 0.05). Both the SIT150 and SIT30 training were shown to improve Yo-YoIRT1, Yo-YoIRT2 and VO2max performance compared to the control group, nevertheless, SIT150 was more efficient in improving the Yo-YoIRT1, Yo-YoIRT2 than SIT30. The authors of this study suggest using SIT150 to induce more effective performance outputs in amateur soccer players.

Exploring the effects of interchange rotations on high-intensity activities of elite futsal players

The literature lacks an understanding of the physical demands of team sports with unlimited substitutions (player interchange rotations). Because of this characteristic of the game, it is necessary to analyze the physical requirements through player rotation rather than analyzing global averages. The objective of this research is to investigate the relationship between high-intensity activities (HIA; sum of accelerations, decelerations, and high-speed running actions) performed per interchange rotations and match time variables (playtime, rest time, and work–rest ratio) in elite futsal players. A retrospective observational design was used. Twelve matches from an elite male team competing in the Premier Spanish Futsal League were analyzed using a local positioning system, yielding a total sample of 17 players. The number of HIA performed per interchange rotation varies between players and allows the identification of three distinct activity profiles—lower HIA (10 HIA), medium HIA (28 HIA), and higher HIA (38 HIA). Furthermore, these profiles were found to be stable alongside the existing interchange rotations throughout the match. Playtime ( F = 40.9, p &lt; .001) and work–rest ratio ( F = 15.6, p &lt; .001) are the time variables that best differentiate match activity profiles. Players with more playing time (4.6 ± 1.0 min) and a work–rest ratio equal to or greater than 1 (1.1 ± 0.6 a.u.) have a greater ability to repeat HIA per rotation.

Ad libitum drinking prevents dehydration during physical work in the heat when adhering to occupational heat stress recommendations

ABSTRACT Government entities issue recommendations that aim to maintain core temperature below 38.0°C and prevent dehydration [>2% body mass loss] in unacclimated workers exposed to heat. Hydration recommendations suggest drinking 237 mL of a cool sport drink every 15–20 min. This is based on the premise that ad libitum drinking results in dehydration due to inadequate fluid replacement, but this has never been examined in the background of recommendation compliant work in the heat. Therefore, we tested the hypothesis that ad libitum drinking results in >2% body mass loss during heat stress recommendation compliant work. Ten subjects completed four trials consisting of 4 hours of exposure to wet bulb globe temperatures (WBGT) of 24.1 ± 0.3°C (A), 26.6 ± 0.2°C (B), 28.5 ± 0.2°C (C), 29.3 ± 0.6°C (D). Subjects walked on a treadmill and work-rest ratios were prescribed as a function of WBGT [work:rest per hour – A: 60:0, B: 45:15, C: 30:30, D: 15:45] and were provided 237 mL of a cool sport drink every 15 min to drink ad libitum. Mean core temperature was higher in Trial A (37.8 ± 0.4°C; p = 0.03) and Trial B (37.6 ± 0.3°C; p = 0.01) versus Trial D (37.3 ± 0.3°C) but did not differ between the other trials (p ≥ 0.20). Body mass loss (A: −0.9 ± 0.7%, B: −0.7 ± 0.5%, C: −0.3 ± 0.5%, D: −0.4 ± 0.6%) was greater in Trial A compared to Trial D (p = 0.04) and was different from 2% body mass loss in all trials (p ≤ 0.01). Ad libitum drinking during recommendation compliant work in the heat rarely resulted in dehydration. Registered Clinical Trial (NCT04767347)

Comparison of physiological and perceptual load between uke and tori after intermittent osaekomi-waza exercise in judo

ABSTRACT This study investigated differences in physiological and perceptual responses between uke and tori during intermittent osaekomi-waza exercise. Twenty-one male judo athletes voluntarily participated in this study. Following anthropometric measurements and 1 min uchi-komi test, athletes executed 20 s × 6 sets (1:½ work rest ratio) intermittent osaekomi-waza exercise with kesa-gatame as both uke and tori. Athletes’ heart rate and lactate concentration were monitored at rest, 1 min, and 6 min following the exercise while the athletes classified the rate of perceived exertion just after the exercise. During the experiment, the changes in heart rate were different between positions with higher values in uke position compared to tori position after the intermittent exercise (F2,40 = 4.28, p = 0.03). Moreover, athletes in the uke position stated a higher rating of perceived exertion than athletes in the tori position (p = 0.01). However, blood lactate responses were found to be similar between positions (p > 0.05). Intermittent osaekomi-waza exercises resulted in similar metabolic load for uke and tori positions, while higher cardiovascular load was observed in the uke position compared to the tori position. Thus, it can be concluded that the athletes in uke position are exposed to more cardiovascular load compared to those in tori position and present higher perceptual responses.

The Relationship Between Relative External Training Load and Sports Injury in Collegiate Football Players

PURPOSE: This study aimed to investigate the relationship between relative training load and non-contact injuries in collegiate football players.METHODS: Eleven players were enrolled in this study. During sports competitions, data were collected using global positioning system (GPS) units (10 Hz), and information on sport-related injuries of the lower extremities was recorded. The acute-to-chronic workload ratio (ACWR) of total distance covered, high-intensity distance (≥18 km/hours), sprint distance (≥21 km/hours) and bouts, work-torest ratio, and acceleration-deceleration bouts were calculated. Data were evenly split into quartiles, with the lowest ACWR range used as a reference group. Odds ratios were calculated to determine the injury risk at a given ACWR of each GPS variable, using a logistic regression analysis.RESULTS: Six players experienced nine injuries, yielding an incidence of 132.93 injuries per 1,000 athlete exposures. Based on ACWR values, the highest risk of injury was most associated with total distance covered, followed by high-intensity distance, and sprint bouts. The lowest risk of injury was associated with sprint distance, which yielded a lower injury risk than that in the reference group.CONCLUSIONS: Our study shows the need for continued monitoring of in-game athlete performance in preventing non-contact sportrelated injuries in football players.

Voluntary drinking prevents dehydration when following occupational heat stress recommendations

INTRODUCTIONFederal and local entities issue guidance that aims to maintain core temperature (TC) below 38.0°C in unacclimated workers exposed to heat. These heat stress recommendations prescribe work‐rest ratios as a function of wet bulb globe temperature (WBGT) and metabolic heat production (Hprod). Hydration recommendations are less nuanced and suggest drinking 237 mL of a cool sport drink every 15‐20 min for work in the heat exceeding 2 h. This drinking regimen is based on the premise that ad libitum drinking during heat exposure results in dehydration [defined as &gt;2% body mass loss (BML)] due to inadequate drinking. To our knowledge, this hydration guidance has not been examined under heat stress recommendation compliant scenarios. Thus, it is unknown if ad libitumdrinking results in dehydration during recommendation compliant work in the heat.PURPOSETest the hypothesis that ad libitum drinking during heat stress recommendation compliant work in the heat will result in &gt;2% BML.METHODSSix, healthy, unacclimated, euhydrated subjects (2 women; 27±5 y) completed four trials consisting of 4 h (half a workday) of exposure to WBGTs of 23.9±0.2°C (A), 26.3±0.9°C (B), 28.4±0.1°C (C), 29.2±0.7°C (D). Subjects walked on a treadmill evoking a Hprod of 481±95 W, which is the average Hprod for outdoor workers in the U.S. NIOSH‐compliant work‐rest ratios were prescribed as a function of WBGT and Hprod [work:rest per hour (in min) ‐ A: 60:0, B: 45:15, C: 30:30, D: 15:45] and subjects were provided 237 mL of a cool (10±4°C) flavor preferred sport drink (Gatorade) every 15 min and drank ad libitum. BML was determined from changes in nude body mass and correction for fluid intake and urine loss provided an estimate of sweat rate. TC (telemetry pill) is reported as an average over the trial and as the percent of time TC exceeded 38.0°C (Time &gt;38). Thirst perception (1 = not thirsty, 9 = very, very thirsty) is reported as an average over the trial. Data are presented as mean±SD (parametric) or median (interquartile range) (nonparametric).RESULTSAverage TC was higher in Trial A (37.8±0.4°C; p=0.05) and Trial B (37.6±0.3°C; p=0.03) versus Trial D (37.3±0.4°C) but did not differ between the other trials (p≥0.20). Time &gt;38 did not differ between trials (A: 24 (5,43)%, B: 6 (0,5)%, C: 0 (0,5)%, D: 0 (0,0)%; p=0.17). Sweat rate was higher in Trial A (0.5±0.1 L/h) versus Trial D (0.4±0.1 L/h; p=0.05) but did not differ between any other trials (p≥0.12). Thirst perception (A: 2±1 a.u., B: 2±0 a.u, C: 2±1 a.u, D: 2±0 a.u; p=0.20) and fluid intake (A: 1.6±0.6 L, B: 1.5±0.5 L, C: 1.7±0.5 L, D: 1.6±0.7 L; p=0.88) did not differ between trials. BML did not differ between trials (A: ‐0.9±0.9%, B: ‐0.8±0.6%, C: ‐0.5±0.4%, D: ‐0.3±0.6%; p=0.24). One subject in one trial lost &gt;2% body mass (Trial A: ‐2.7%).CONCLUSIONAd libitumdrinking during recommendation compliant work in the heat rarely resulted in dehydration. Modification of work‐rest ratios across a range of WBGTs while working at a fixed Hprod mostly maintained TC &lt;38.0°C when ad libitumdrinking was permitted. Thus, absolute fluid prescription may not be necessary to prevent dehydration if adhering to occupational heat stress recommendations and cool fluids are readily available.

Impact of ball material change from celluloid to plastic on game statistics in elite women table-tennis

ABSTRACT This study compared the statistics of 24 matches played by elite women table-tennis players using the old celluloid versus new plastic balls to provide insight into the on-court adaptations made. Matches played by five, top-10 world ranked female players, using the celluloid (n = 12) versus plastic balls (n = 12) in international competitions from 2011 to 2017 were analysed. The results showed that the average strokes per point and point duration were approximately 15% and 13% shorter when playing with the plastic (4.79 ± 0.59; 3.91 ± 0.54s) compared with celluloid balls (5.52 ± 0.62; 4.49 ± 0.53s). Rally intensity was, however, higher for matches played with plastic (1.57 ± 0.27 strokes/s) versus celluloid (1.49 ± 0.25 strokes/s) balls. Overall work-rest ratio was smaller by 3% for the former versus the latter. The trade-off between more intense rallies and more rest time on energy expenditure remains unknown and would be an interesting area to investigate for targeted prescriptions of training programmes.

The Contribution of Energy Systems in Repeated-Sprint Protocols: The Effect of Distance, Rest, and Repetition

ABSTRACT Purpose: This study aims to investigate the effects of rest intervals, sprint distance, and number of repetitions on performance variables, physiological responses, and energy system contributions in repeated-sprint protocols when total distance variable was the controlled (300 m). Method: Sixteen male soccer players participated in this study. The four protocols, each totaling a distance of 300 m, consisted of the combination of 15 and 30 m sprints with 30 s rest intervals (15meters30sec and 30meters30sec, respectively) and 1:5 work–rest ratios (15meters12sec and 30meters22sec, respectively). Aerobic, glycolytic, and phosphagen energy systems’ contributions were calculated from the oxygen consumption (VO2) during the exercise, net lactate production, and the recovery VO2 kinetics using mono-exponential models. Repeated measures ANOVA with the Bonferroni correction was applied to examine the hypothesized differences. Results: The findings indicated that total sprint duration (F3:45=281.14; p<0.001), percentage of performance decline (F3:45=16.58; p<0.001), delta lactate (F3:45=39.72, p<0.001), rating of perceived exertion (F3:45=28.64; p<0.001), energy demand (F3:45=101.6; p<0.001), VO2 during the rest intervals (F3:45=42.72; p<0.001), and the absolute contribution of glycolytic (F3:45=119.6; p<0.001) and phosphagen energy systems (F3:45=72.9; p<0.001) were lowest in the 15meters30sec compared to other protocols. However, the relative contribution of aerobic system was greatest in the 15meters30sec compared to other protocols (F3:45=28.1, p<0.001). Both absolute (F3:45=119.6; p<0.001) and relative contribution of glycolytic system (F3:45=88.5, p<0.001) were greatest in the 30meters22sec compared to other protocols. Conclusion: This study showed that increasing sprint distance when rest interval is equal and decreasing rest interval when sprint distance is equal can increase the glycolytic system contribution.

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The relationship between global positioning system variables and injury occurrences in female field hockey

The noncontact and soft-tissue injuries to lower extremities that occur as a result of excessive running loads are largely preventable. This study investigated the relationship between global positioning system variables and noncontact soft-tissue injuries in female field hockey players based on their position on the field. Fifty-two players enrolled in the Korea National Team were monitored using global positioning system units in game-based training and competitions. The measurements obtained were total distance covered, high-intensity running distance, work–rest ratio, meters per minute, repeated high-intensity effort bouts, maximal velocity, and acceleration and deceleration bouts. Noncontact soft-tissue injuries in lower extremities were documented throughout the same period. For measuring the absolute external workload of each global positioning system variable, players’ data were averaged for 1- and 4-week periods before they were injured (injury-related block), averaging values across 1 and 4 weeks before the injury-related block (non-injury block), as well as averaging values from the beginning of the data collection to the point of injury (total average). These blocks were compared to each other and to the corresponding total averages for the 1- and 4-week periods, depending on their position on the field. Of the 52 players, 28 players (8 forwards, 11 midfielders, and 9 defenders) injured their lower extremities for a total of 38 injuries. Of these injuries, 11 occurred in forwards, 17 occurred in midfielders, and 10 occurred in defenders with some players experiencing more than one injury. Different positions on the field have different global positioning system variables related to the occurrence of noncontact soft-tissue injuries in lower extremities, but there was a significant difference in global positioning system variable of injury-related block for only the 4-week period among their position on the field. Especially, increases in high-intensity running distance and repeated high-intensity effort bouts of defenders during the 4-week period were significantly related to the occurrence of injuries. To decrease the risk of injury in female field hockey players, different global positioning system variables should be monitored and modified in planned future training or competitions.

Specifying and Mitigating Thermal Stress Effects on Cognition During Personal Protective Equipment Use.

To report present understanding concerning selected task and environmental factors influencing the changing performance capacity associated with use of personal protective equipment (PPE). Much knowledge is available concerning change in complex cognitive capacities under the effects of thermal stress. Our science can inform critical care facilities as to remediation strategies such as work-rest schedules to minimize performance error in highly cognitively demanding circumstances such as intensive care units. The present exposition draws from the state-of-the-art understanding concerning thermal stress effects on cognition and workload in complex and demanding tasks. The summation and synthesis of HF/E findings provides important insights into combinatorial effects of forms of stress, typically dealt with only as discrete sources in traditional standards and regulations. The identified interaction between ascending thermal stress and cognitive task demand provides an instance of the plurality of ways HF/E can specify performance limitations in safety-critical circumstances, as witnessed in the current pandemic. Accumulated HF/E insights provide systematic ways in which to address and ameliorate the combined forces of physical and cognitive stress on medical personnel constrained to use varying forms of PPE. These principles extend beyond this specific domain to all who are required to work in differential and isolated microclimates. To minimize the possibility of critical and life-threatening error in intensive care facilities which necessitate PPE use, we need principled work-rest ratio and heat stress mitigation guidance. To promote health, we need to champion healthy work practices in our health workers. HF/E insights can help achieve this important goal.

Effects of Work and Recovery Duration and Their Ratio on Cardiorespiratory and Metabolic Responses During Aerobic Interval Exercise.

Myrkos, A, Smilios, I, Zafeiridis, A, Iliopoulos, S, Kokkinou, EM, Douda, H, and Tokmakidis, SP. Effects of work and recovery duration and their ratio on cardiorespiratory and metabolic responses during aerobic interval exercise. J Strength Cond Res 36(8): 2169-2175, 2022-This study examined the effect of work and recovery durations and of work-to-rest ratio (WRR) on total exercise time and oxygen consumption (V̇ o2 max), on exercise time above 80, 90, and 95% of V̇ o2 max and HRmax, and on blood lactate concentrations during aerobic interval exercise. Twelve men (22.1 ± 1 year) executed, until exhaustion, 4 interval protocols at an intensity corresponding to 100% of maximal aerobic velocity. Two protocols were performed with work bout duration of 120 seconds and recovery durations of 120 (WRR: 1:1) or 60 seconds (WRR: 2:1), and 2 protocols with work bout duration of 60 seconds and recovery durations of 60 (WRR: 1:1) or 30 seconds (WRR: 2:1). When compared at equal exercise time, total V̇ o2 and exercise time at V̇ o2 above 80, 90, and 95% of V̇ o2 max were longer ( p < 0.05) in 120:120, 120:60 and 60:30 vs. the 60:60 protocol. When analyzed for total exercise time (until exhaustion), total V̇ o2 was higher ( p < 0.01) in the 60:60 compared with all other protocols, and in the 120:120 compared with 120:60. Exercise time >95% of V̇ o2 max and HRmax was higher ( p < 0.05) in the 120:120 vs. the 60:60 protocol; there were no differences among protocols for exercise time >90% of V̇ o2 max and HRmax. Blood lactate was lower ( p < 0.05) in the 60:60 compared with all other protocols and in the 60:30 vs. the 120:60. In conclusion, when interval exercise protocols are executed at similar effort (until exhaustion), work and recovery durations do not, in general, affect exercise time at high oxygen consumption and HR rates. However, as work duration decreases, a higher work-to-recovery ratio (e.g., 2:1) should be used to achieve and maintain high (>95% of maximum) cardiorespiratory stimulus. Longer work bouts and higher work-to-recovery ratio seem to activate anaerobic glycolysis to a greater extent, as suggested by greater blood lactate concentrations.

Comparison of the Physical Demands of Friendly Matches and Different Types On-Field Integrated Training Sessions in Professional Soccer Players.

The aim of this study was to investigate the relationships among physical demands of two friendly matches (FMs) and three task training sessions (TS1,2,3) combining in a different way: a Small-Sided Game (SSG), Mini-Goals (MG), a ball Circuit Training (CT) and a Large-Sided Game (LSG): SSG+MG+LSG (TS1), SSG+CT+LSG (TS2) and MG+CT+LSG (TS3). The TS and match demands in running intensities were monitored in fourteen professional soccer players (age = 23.2 ± 2.7 years, height = 178 ± 6 cm, body mass = 73.2 ± 6.9 kg, mean and SD, respectively) using 10-Hz global positioning system devices, and players’ perception of exertion was recorded after each session or match using a visual analogue scale. A one-way repeated measures ANOVA with a Bonferroni correction coupled with magnitude-based inferences were used. A principal component (PC) analysis was conducted on all variables to account for covariance. Three PCs were retained, explaining 76% of the variance: Component 1 explained 46.9% with the associated variables: Total Distance (TD) and distance covered in ranges of speed from >2.2 to <5 m/s, Player Load and Work Rest Ratio; component 2 explained 19.7% and was composed of TD at > 5 m/s and maximal running speed (MRS); and component 3 explained 9.5% and was represented by TD < 2.2 m/s, decelerations and accelerations. The ANOVA results showed significant differences (p < 0.05) among TS vs. FM in TD3, TD4, TD5, and TD > 5, TD, deceleration rate, acceleration rate, maximal running speed, exertion index, work rest ratio, and self-reported exertion. Therefore, the training routines did not replicate the main set of high intensity efforts experienced in competitive conditions. Additionally, PC analysis could be applied in order to select the most representative training and competitive conditions.

Physical fitness improvements of 8-week light vs. heavy tyre flip training in young adults.

This study compared the effects of eight-week tyre flipping training intervention using light and heavy tyres on physical fitness performance. Twenty-nine young physically active males were divided into light (n = 15) and heavy (n = 14) tyre flipping groups evenly according to body weight and height. Body-to-tyre weight ratios were 0.61 ± 0.06 for the light tyre (LTTG) and 1.51 ± 0.16 for the heavy tyre training (HTTG) groups. Fitness parameters were measured before and after the intervention. One-way ANCOVA analysis indicated no significant between-group differences when pre-test values were controlled. Both groups demonstrated within-group improvements in 6RM bench press (ES: 0.98 in LTTG and 1.10 in HTTG), intermittent endurance (ES: 0.45 in LTTG and 0.66 in HTTG), five horizontal jumps (ES: 0.35 in LTTG and 0.26 in HTTG), and agility (ES: 0.34 in LTTG and 0.41 in HTTG). Both groups improved tyre flipping efficiency, through decreasing average set duration and work-rest ratios in the first six training sessions, and reached a plateau starting from the 7th training session. This study provides the first empirical evidence for coaches to justify usage of tyre flip training and the timing to progressive overload for a population with limited weight training and no tyre flip training experience.

Effects of intermittent hypoxic training performed at high hypoxia level on exercise performance in highly trained runners

ABSTRACTThis study exanimated the effects of intermittent hypoxic training (IHT) conducted at a high level of hypoxia with recovery at ambient air on aerobic/anaerobic capacities at sea level and hematological variations. According to a double-blind randomized design, fifteen highly endurance-trained runners completed a 6-weeks regimented training with 3 sessions per week consisting of intermittent runs (6x work-rest ratio of 5ʹ:5ʹ) on a treadmill at 80–85% of maximal aerobic speed (). Nine athletes (hypoxic group, HG) performed the exercise bouts at FI02 = 10.6–11.4% while six athletes (normoxic group, NG) exercised at ambient air. Running time to exhaustion at a velocity corresponding to 95% significantly increased for HG while no effect was found for NG. Regarding , no significant effects were found in either training group. In addition, the decline of jumping performances over a 45s-continuous maximal vertical jump test (i.e. anaerobic capacity index) tended to be lower in HG compared to NG. The levels of the studied hematological variables, including erythropoietin and hematocrit, did not significantly change for either HG or NG. These results highlight that our IHT protocol may induce additional effects on aerobic performance without compromising the anaerobic capacity index in highly-trained athletes.