Caffeine and Placebo Improved Maximal Exercise Performance Despite Unchanged Motor Cortex Activation and Greater Prefrontal Cortex Deoxygenation

Caffeine (CAF) is an ergogenic aid used to improve exercise performance. Independent studies have suggested that caffeine may have the ability to increase corticospinal excitability, thereby decreasing the motor cortex activation required to generate a similar motor output. However, CAF has also been suggested to induce a prefrontal cortex (PFC) deoxygenation. Others have suggested that placebo (PLA) may trigger comparable effects to CAF, as independent studies found PLA effects on motor performance, corticospinal excitability, and PFC oxygenation. Thus, we investigated if CAF and CAF-perceived PLA may improve motor performance, despite the likely unchanged MC activation and greater PFC deoxygenation. Nine participants (26.4 ± 4.8 years old, VO2MAX of 42.2 ± 4.6 mL kg-1 min-1) performed three maximal incremental tests (MITs) in control (no supplementation) and ∼60 min after CAF and PLA ingestion. PFC oxygenation (near-infrared spectroscopy at Fp1 position), MC activation (EEG at Cz position) and vastus lateralis and rectus femoris muscle activity (EMG) were measured throughout the tests. Compared to control, CAF and PLA increased rectus femoris muscle EMG (P = 0.030; F = 2.88; d = 0.84) at 100% of the MIT, and enhanced the peak power output (P = 0.006; F = 12.97; d = 1.8) and time to exhaustion (P = 0.007; F = 12.97; d = 1.8). In contrast, CAF and PLA did not change MC activation, but increased the PFC deoxygenation as indicated by the lower O2Hb (P = 0.001; F = 4.68; d = 1.08) and THb concentrations (P = 0.01; F = 1.96; d = 0.7) at 80 and 100% the MIT duration. These results showed that CAF and CAF-perceived PLA had the ability to improve motor performance, despite unchanged MC activation and greater PFC deoxygenation. The effectiveness of CAF as ergogenic aid to improve MIT performance was challenged

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Arterialized and venous blood lactate concentration difference during different exercise intensities

Objective: The purpose of this study was to investigate the difference between arterialized and venous blood lactate concentrations [La] during constant-load exercises at different intensities. Methods: Fifteen physically active men cycled for 30 minutes (or until exhaustion) at the first lactate threshold (LT1), at 50% of the difference between the first and second lactate threshold (TT50%), at the second lactate threshold (LT2), and at 25% of the difference between LT2 and maximal aerobic power output (TW25%). Samples of both arterialized and venous blood were collected simultaneously at rest and every 5 minutes during the exercise. Results: The arterialized blood [La] was higher at minute 5 than venous blood [La] for all exercise intensities (p  0.05). The arterialized-venous difference during the first 10 minutes was greater for the two highest exercise intensities (LT2 and TW25%) compared with the two lowest (LT1 and TT50%, p  0.05). Conclusion: These results suggest a delayed lactate appearance in the venous blood, which is accentuated at higher exercise intensities. The lactate measured in arterialized and venous blood is interchangeable only when blood samples are collected at least 10 minutes after the exercise starts

Effects of a low- or a high-carbohydrate diet on performance, energy system contribution, and metabolic responses during supramaximal exercise

The purpose of the present study was to examine the effects of a high- or low-carbohydrate (CHO) diet on performance, aerobic and anaerobic contribution, and metabolic responses during supramaximal exercise. Six physically-active men first performed a cycling exercise bout at 115% maximal oxygen uptake to exhaustion after following their normal diet for 48 h (50% of CHO, control test). Seventy-two hours after, participants performed a muscle glycogen depletion exercise protocol, followed by either a high- or low-CHO diet (70 and 25% of CHO, respectively) for 48 h, in a random, counterbalanced order. After the assigned diet period (48 h), the supramaximal cycling exercise bout (115% maximal oxygen consumption) to exhaustion was repeated. The low-CHO diet reduced time to exhaustion when compared with both the control and the high-CHO diet (−19 and −32%, respectively, p 0.05). The low-CHO diet was associated with a lower blood lactate concentration (p 0.05). In conclusion, a low-CHO diet reduces both performance and total aerobic energy provision during supramaximal exercise. As peak K+ concentration was similar, but time to exhaustion shorter, the low-CHO diet was associated with an earlier attainment of peak plasma K+ concentration

Low carbohydrate diet affects the oxygen uptake on-kinetics and rating of perceived exertion in high intensity exercise

The aim of this study was to determine if the carbohydrate (CHO) availability alters the rate of increase in the rating of perceived exertion (RPE) during high intensity exercise and whether this would be associated with physiological changes. Six males performed high intensity exercise after 48 h of controlled, high CHO (80%) and low CHO (10%) diets. Time to exhaustion was lower in the low compared to high CHO diet. the rate of increase in RPE was greater and the VO(2) slow component was lower in the low CHO diet than in the control. There was no significant condition effect for cortisol, insulin, pH, plasma glucose, potassium, or lactate concentrations. Multiple linear regression indicated that the total amplitude of VO(2) and perceived muscle strain accounted for the greatest variance in the rate of increase in RPE. These results suggest that cardiorespiratory variables and muscle strain are important afferent signals from the periphery for the RPE calculations.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Univ Fed Alagoas, Fac Nutr, Sports Sci Res Grp, BR-7072970 Maceio, Alagoas, BrazilUniv São Paulo, Sch Phys Educ & Sport, São Paulo, BrazilUniversidade Federal de São Paulo, Div Nutr Physiol, Dept Physiol, São Paulo, BrazilUniversidade Federal de São Paulo, Hosp Kidney & Hypertens, Div Nephrol, São Paulo, BrazilUniversidade Federal de São Paulo, Div Nutr Physiol, Dept Physiol, São Paulo, BrazilUniversidade Federal de São Paulo, Hosp Kidney & Hypertens, Div Nephrol, São Paulo, BrazilFAPESP: 2006-60641-6Web of Scienc

The influence of peripheral afferent signals on the rating of perceived exertion and time to exhaustion during exercise at different intensities

This study determined which peripheral variables would better predict the rating of perceived exertion (RPE) and time to exhaustion (TE) during exercise at different intensities. Ten men performed exercises at first lactate threshold (LT1), second lactate threshold (LT2), 50% of the distance from LT1 to LT2 (TT50%), and 25% of the distance from LT2 to maximal power output (TW25%). Lactate, catecholamines, potassium, pH, glucose, (V) over dotO(2), VE, HR, respiratory rate (RR) and RPE were measured and plotted against the exercise duration for the slope calculation. Glucose, dopamine, and noradrenaline predicted RPE in TT50% (88%), LT2 (64%), and TW25% (77%), but no variable predicted RPE in LT1. RPE (55%), RPE+HR (86%), and RPE+RR (92% and 55%) predicted TE in LT1, TT50%, LT2, and TW25%, respectively. At intensities from TT50% to TW25%, variables associated with brain activity seem to explain most of the RPE slope, and RPE (+HR and+RR) seems to predict the TE.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Discovery HealthMedical Research CouncilUniversity of Cape TownUniv São Paulo, Sch Phys Educ & Sport, BR-05508030 São Paulo, BrazilFed Univ Alagoas UFAL, Sports Sci Res Grp, Maceio, BrazilUniversidade Federal de São Paulo, Div Nephrol, Hosp Kidney & Hypertens, São Paulo, BrazilUniv Cape Town, MRC UCT Res Unit Exercise Sci & Sports Med, ZA-7725 Newlands, South AfricaUniv Cape Town, Sports Sci Inst South Africa, ZA-7725 Newlands, South AfricaUniversidade Federal de São Paulo, Div Nephrol, Hosp Kidney & Hypertens, São Paulo, BrazilCAPES: PDEE BEX 1900/08-0FAPESP: 2006/60641-6Web of Scienc

Cardiopulmonary, blood metabolite and rating of perceived exertion responses to constant exercises performed at different intensities until exhaustion

Objective This study analysed cardiopulmonary, metabolic and rating of perceived exertion (RPE) responses during exercise bouts performed below, at and above the second lactate threshold (LT2) intensity.Methods 10 healthy men performed constant workloads to exhaustion at the first lactate threshold (LT1), LT2 and 25% of the difference between LT2 and maximal aerobic power output (TW(25%)) identified during an incremental test. the time to exhaustion (TE) was 93.8 (18.0), 44.5 (16.0) and 22.8 (10.6) min at LT1, LT2 and TW(25%), respectively (p < 0.001). Metabolic and cardiopulmonary parameters and RPE data were time normalised to the exercise bout duration. the correlation between the slope of these variables and TE was calculated.Results Differences were found for respiratory exchange ratio (RER), RPE and potassium at LT1; RER, RPE, norepinephrine and potassium at LT2; and ventilation, respiratory rate (RR), RPE, lactate and potassium at TW(25%). Except for RR, no cardiopulmonary or metabolic parameter increased significantly after 50% of the exercise duration, indicating a physiological steady state. VO(2), heart rate and lactate at exhaustion in all exercise bouts were significantly lower than values reached in the maximal incremental test. the slope of most metabolic variables was not correlated to TE in LT1, LT2 and TW(25%), whereas the slope of RPE was significantly correlated to TE (r = -0.72 to -0.84; p < 0.05) for the three exercise intensities.Conclusion Contrary to traditional suggestions, exercise at LT1, LT2 and TW(25%) intensities is performed and terminated in the presence of an overall physiological steady state.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Medical Research CouncilUniversity of Cape TownUniv São Paulo, Sch Phys Educ & Sport, Dept Sports, BR-05508030 São Paulo, BrazilUniv Cape Town, MRC UCT Res Unit Exercise Sci & Sports Med, Dept Human Biol, Sports Sci Inst S Africa, Newlands, South AfricaUniv Fed Alagoas, Sports Sci Res Grp, Maceio, BrazilUniversidade Federal de São Paulo, Div Nutr Physiol, Dept Physiol, São Paulo, BrazilUniversidade Federal de São Paulo, Div Nutr Physiol, Dept Physiol, São Paulo, BrazilFAPESP: 2006/60641-6Web of Scienc

RELATIONSHIP BETWEEN TRAINING STATUS AND MAXIMAL FAT OXIDATION RATE

This study aimed to compare maximal fat oxidation rate parameters between moderate- and low-performance runners. Eighteen runners performed an incremental treadmill test to estimate individual maximal fat oxidation rate (Fatmax) based on gases measures and a 10,000-m run on a track. The subjects were then divided into a low and moderate performance group using two different criteria: 10,000-m time and VO2max values. When groups were divided using 10,000-m time, there was no significant difference in Fatmax (0.41 ± 0.16 and 0.27 ± 0.12 g.min-1, p = 0.07) or in the exercise intensity that elicited Fatmax (59.9 ± 16.5 and 68.7 ± 10.3 % O2max, p = 0.23) between the moderate and low performance groups, respectively (p > 0.05). When groups were divided using VO2max values, Fatmax was significantly lower in the low VO2max group than in the high VO2max group (0. 29 ± 0.10 and 0.47 ± 0.17 g.min-1, respectively, p < 0.05) but the intensity that elicited Fatmax did not differ between groups (64.4 ± 14.9 and 61.6 ± 15.4 %VO2max). Fatmax or %VO2max that elicited Fatmax was not associated with 10,000 m time. The only variable associated with 10,000-m running performance was %VO2max used during the run (p < 0.01). In conclusion, the criteria used for the division of groups according to training status might influence the identification of differences in Fatmax or in the intensity that elicits Fatmax