RESUMO
PURPOSE: Caffeine is a commonly used ergogenic aid for endurance events; however, its efficacy and safety have been questioned in hot environmental conditions. The aim of this study was to investigate the effects of acute caffeine supplementation on cycling time to exhaustion and thermoregulation in the heat. METHODS: In a double-blind, randomised, cross-over trial, 12 healthy caffeine-habituated and unacclimatised males cycled to exhaustion in the heat (35 °C, 40% RH) at an intensity associated with the thermoneutral gas exchange threshold, on two separate occasions, 60 min after ingesting caffeine (5 mg/kg) or placebo (5 mg/kg). RESULTS: There was no effect of caffeine supplementation on cycling time to exhaustion (TTE) (caffeine; 28.5 ± 8.3 min vs. placebo; 29.9 ± 8.8 min, P = 0.251). Caffeine increased pulmonary oxygen uptake by 7.4% (P = 0.003), heat production by 7.9% (P = 0.004), whole-body sweat rate (WBSR) by 21% (P = 0.008), evaporative heat transfer by 16.5% (P = 0.006) and decreased estimated skin blood flow by 14.1% (P < 0.001) compared to placebo. Core temperature was higher by 0.6% (P = 0.013) but thermal comfort decreased by - 18.3% (P = 0.040), in the caffeine condition, with no changes in rate of perceived exertion (P > 0.05). CONCLUSION: The greater heat production and storage, as indicated by a sustained increase in core temperature, corroborate previous research showing a thermogenic effect of caffeine ingestion. When exercising at the pre-determined gas exchange threshold in the heat, 5 mg/kg of caffeine did not provide a performance benefit and increased the thermal strain of participants.
Assuntos
Regulação da Temperatura Corporal , Cafeína , Humanos , Cafeína/farmacologia , Cafeína/administração & dosagem , Masculino , Regulação da Temperatura Corporal/efeitos dos fármacos , Regulação da Temperatura Corporal/fisiologia , Adulto , Ciclismo/fisiologia , Temperatura Alta , Método Duplo-Cego , Estudos Cross-Over , Adulto Jovem , Consumo de Oxigênio/efeitos dos fármacos , Sudorese/efeitos dos fármacos , Sudorese/fisiologiaRESUMO
We estimated the effectiveness of using velocity feedback to regulate resistance training load on changes in muscle strength, power, and linear sprint speed in apparently healthy participants. Academic and grey literature databases were systematically searched to identify randomised trials that compared a velocity-based training intervention to a 'traditional' resistance training intervention that did not use velocity feedback. Standardised mean differences (SMDs) were pooled using a random effects model. Risk of bias was assessed with the Risk of Bias 2 tool and the quality of evidence was evaluated using the GRADE approach. Four trials met the eligibility criteria, comprising 27 effect estimates and 88 participants. The main analyses showed trivial differences and imprecise interval estimates for effects on muscle strength (SMD 0.06, 95% CI -0.51-0.63; I2 = 42.9%; 10 effects from 4 studies; low-quality evidence), power (SMD 0.11, 95% CI -0.28-0.49; I2 = 13.5%; 10 effects from 3 studies; low-quality evidence), and sprint speed (SMD -0.10, 95% CI -0.72-0.53; I2 = 30.0%; 7 effects from 2 studies; very low-quality evidence). The results were robust to various sensitivity analyses. In conclusion, there is currently no evidence that VBT and traditional resistance training methods lead to different alterations in muscle strength, power, or linear sprint speed.
Assuntos
Treinamento Resistido , Aclimatação , Adaptação Fisiológica , Humanos , Força Muscular/fisiologia , Treinamento Resistido/métodosRESUMO
ABSTRACT: Brown, F, Jeffries, O, Gissane, C, Howatson, G, van Someren, K, Pedlar, C, Myers, T, and Hill, JA. Custom-fitted compression garments enhance recovery from muscle damage in rugby players. J Strength Cond Res 36(1): 212-219, 2022-to evaluate the effects of custom-fitted compression garments (CG) on recovery from muscle damage in rugby players. Forty-five players were tested for lower-body strength, power, and indices of muscle damage before completing a damaging protocol (20 × 20-m sprints with 5-m deceleration, 100 drop jumps). Players were randomly assigned to wear either custom-fitted (CF, n = 13), or standard-sized CG (SSG, n = 16), or to receive sham ultrasound therapy (CON, n = 16) immediately after exercise. Players were retested immediately, then after 24 and 48 hours. Strength recovery was significantly different between groups (F = 2.7, p = 0.02), with only CF recovering to baseline values by 48 hours (p = 0.973). Time × condition effects were also apparent for creatine kinase activity (χ2 = 30.4, p < 0.001) and midthigh girth (F = 3.7, p = 0.005), with faster recovery apparent in CF compared with both CON and SSG (p < 0.05). Custom-fitted CG improved strength recovery and indices of muscle damage in rugby players, compared with controls and standard-sized garments. Athletes and coaches would be advised to use appropriately fitted CG to enhance strength recovery after damaging exercise.
Assuntos
Traumatismos do Joelho/prevenção & controle , Músculo Esquelético , Rugby , Meias de Compressão , Atletas , Vestuário , Futebol Americano , Humanos , Força Muscular , Músculo Esquelético/fisiologiaRESUMO
ABSTRACT: Jeffries, O, Simmons, R, Patterson, SD, and Waldron, M. Functional threshold power is not equivalent to lactate parameters in trained cyclists. J Strength Cond Res 35(10): 2790-2794, 2021-Functional threshold power (FTP) is derived from a maximal self-paced 20-minute cycling time trial whereby the average power output is scaled by 95%. However, the physiological basis of the FTP concept is unclear. Therefore, we evaluated the relationship of FTP with a range of laboratory-based blood lactate parameters derived from a submaximal threshold test. Twenty competitive male cyclists completed a maximal 20-minute time trial and an incremental exercise test to establish a range of blood lactate parameters. Functional threshold power (266 ± 42 W) was strongly correlated (r = 0.88, p < 0.001) with the power output associated with a fixed blood lactate concentration 4.0 mmol·L-1 (LT4.0) (268 ± 30 W) and not significantly different (p > 0.05). While mean bias was 2.9 ± 24.6 W, there were large limits of agreement (LOA) between FTP and LT4.0 (-45 to 51 W). All other lactate parameters, lactate threshold (LT) (236 ± 32 W), individual anaerobic threshold (244 ± 33 W), and LT thresholds determined using the Dmax method (221 ± 25 W) and modified Dmax method (238 ± 32 W) were significantly different from FTP (p < 0.05). While FTP strongly correlated with LT4.0, the large LOA refutes any equivalence as a measure with physiological basis. Therefore, we would encourage athletes and coaches to use alternative field-based methods to predict cycling performance.
Assuntos
Ciclismo , Ácido Láctico , Limiar Anaeróbio , Teste de Esforço , Humanos , Masculino , Consumo de OxigênioRESUMO
We conducted a systematic review and meta-analysis of randomized controlled trials examining the effect of vitamin C and/or E on exercise-induced training adaptations. Medline, Embase and SPORTDiscus databases were searched for articles from inception until June 2019. Inclusion criteria was studies in adult humans where vitamin C and/or E had to be consumed alongside a supervised exercise training program of ≥4 weeks. Nine trials were included in the analysis of aerobic exercise adaptations and nine for resistance training (RT) adaptations. Vitamin C and/or E did not attenuate aerobic exercise induced improvements in maximal aerobic capacity (VÌO2max) (SMD -0.14, 95% CI: -0.43 to 0.15, P = 0.35) or endurance performance (SMD -0.01, 95% CI: -0.38 to 0.36, P = 0.97). There were also no effects of these supplements on lean mass and muscle strength following RT (SMD -0.07, 95% CI: -0.36 to 0.23, P = 0.67) and (SMD -0.15, 95% CI: -0.16 to 0.46, P = 0.35), respectively. There was also no influence of age on any of these outcomes (P > 0.05). These findings suggest that vitamin C and/or E does not inhibit exercise-induced changes in physiological function. Studies with larger sample sizes and adequate power are still required.
Assuntos
Ácido Ascórbico , Exercício Físico , Adaptação Fisiológica , Adulto , Suplementos Nutricionais , Humanos , Ensaios Clínicos Controlados Aleatórios como AssuntoRESUMO
Jeffries, O, Hill, J, Patterson, SD, and Waldron, M. Energy drink doses of caffeine and taurine have a null or negative effect on sprint performance. J Strength Cond Res 34(12): 3475-3481, 2020-This study investigated the effects of caffeine and taurine coingestion on repeat-sprint cycling performance and associated physiological and perceptual responses. In a double-blind, cross-over, repeated measures study, 11 male subjects (age 21 ± 2 years; stature 178 ± 7 cm; body mass 80 ± 13 kg) completed 10 × 6-second sprints on a cycle ergometer, each separated by 24 seconds, one hour after ingesting: caffeine (80 mg) and taurine (1 g), equivalent to the amount observed in popular commercial energy drinks, or placebo (maltodextrin â¼1 g) in a gelatine capsule. Performance was measured on a cycle ergometer, whereas blood lactate concentration (B[la]), rating of perceived exertion (RPE), and heart rate (HR) were measured at baseline (pre-exercise) and after sprints 5 and 10. Magnitude-based inferences revealed likely, trivial differences in peak power and unclear, trivial intersprint fatigue index after ingestion of the caffeine and taurine supplement. Intrasprint fatigue was greater in the caffeine and taurine condition at sprint 10 (likely, small) and possibly smaller in sprints 6-9. The caffeine and taurine supplement had a likely large effect on HR at baseline (effect size = 0.94) and increases in B[la] after sprints 5 (likely small) and 10 (possibly small). There was no effect of the supplement on RPE (unclear, trivial). Administration of caffeine and taurine at doses equivalent to commercial energy drinks did not improve repeat-sprint cycling performance and seemed to induce greater fatigue within selected sprints, particularly at the end of the trial. This undesirable performance effect occurs in parallel with increased HR and glycolytic metabolic bi-products.
Assuntos
Desempenho Atlético , Bebidas Energéticas , Corrida , Adulto , Cafeína , Estudos Cross-Over , Método Duplo-Cego , Ergometria , Humanos , Masculino , Taurina/farmacologia , Adulto JovemRESUMO
Uddin, N, Jeffries, O, Read, P, Howe, L, Patterson, S, and Waldron, M. Physiological responses to linear and nonlinear soccer-specific match simulations and their effects on lower-limb muscle fatigue. J Strength Cond Res 34(11): 3232-3240, 2020-The aims of this study were to: (a) investigate the effects of linear and nonlinear soccer simulations on lower-limb muscle function and physiological responses and (b) evaluate the relationship between match-running demands and changes in lower-limb muscle function. In a repeated-measures cross-over design, 8 participants completed either a linear or nonlinear adapted Loughborough Intermittent Shuttle Test (LIST) on 2 occasions. The movement of players was tracked with a global positioning system, while lower-limb muscle function tests and physiological measurements were performed before and every 15 minutes during the simulation. There were no differences in distance covered, yet high-speed running (p = 0.007), accelerations (p = 0.008), and decelerations (p = 0.015) were higher in the linear LIST. Mean heart rate (p = 0.001) and ratings of perceived exertion (p = 0.013) were higher in the nonlinear LIST. Peak landing forces (p = 0.017) and jump height (p = 0.001) were reduced between baseline and 90 minutes but were not different between conditions. Changes in peak landing forces from baseline to half-time (r = -0.57, n = 16, p = 0.022) and full-time (r = -0.58, n = 16, p = 0.019) were related to high-speed running. Hamstring force was unaffected by time (p = 0.448) but was reduced in the linear LIST (p = 0.044). Protocols posing different external and internal demands elicited similar levels of fatigue across simulations. Hamstring function was not an effective indicator of fatigue, but our results highlight the greater demands placed on this muscle group when higher-speed running is performed.
Assuntos
Teste de Esforço/métodos , Músculos Isquiossurais/fisiologia , Fadiga Muscular/fisiologia , Corrida/fisiologia , Futebol/fisiologia , Aceleração , Adaptação Fisiológica , Adolescente , Adulto , Desempenho Atlético/fisiologia , Desaceleração , Sistemas de Informação Geográfica , Frequência Cardíaca , Humanos , Extremidade Inferior , Masculino , Adulto JovemRESUMO
This study investigated the effects of acute oral taurine ingestion on: (1) the power-time relationship using the 3-min all-out test (3MAOT); (2) time to exhaustion (TTE) 5% > critical power (CP) and (3) the estimated time to complete (Tlim) a range of fixed target intensities. Twelve males completed a baseline 3MAOT test on a cycle ergometer. Following this, a double-blind, randomised cross-over design was followed, where participants were allocated to one of four conditions, separated by 72 h: TTE + taurine; TTE + placebo; 3MAOT + taurine; 3MAOT + placebo. Taurine was provided at 50 mg kg-1, whilst the placebo was 3 mg kg-1 maltodextrin. CP was higher (P < 0.05) in taurine (212 ± 36 W) than baseline (197 ± 40 W) and placebo (193 ± 35 W). Work end power was not affected by supplement (P > 0.05), yet TTE 5% > CP increased (P < 0.05) by 1.7 min after taurine (17.7 min) compared to placebo (16.0 min) and there were higher (P < 0.001) estimated Tlim across all work targets. Acute supplementation of 50 mg kg-1 of taurine improved CP and estimated performance at a range of severe work intensities. Oral taurine can be taken prior to exercise to enhance endurance performance.
Assuntos
Suplementos Nutricionais , Tolerância ao Exercício/efeitos dos fármacos , Taurina/administração & dosagem , Adulto , Estudos Cross-Over , Método Duplo-Cego , Ergometria , Exercício Físico , Humanos , Ácido Láctico/sangue , Masculino , Resistência Física/efeitos dos fármacos , Esforço Físico/efeitos dos fármacos , Distribuição Aleatória , Taurina/farmacologia , Adulto JovemRESUMO
PURPOSE: The purpose of this study was to determine the primary cues regulating perceived effort and exercise performance using a fixed-RPE protocol in severe and moderate hypoxia. METHODS: Eight male participants (26 ± 6 years, 76.3 ± 8.6 kg, 178.5 ± 3.6 cm, 51.4 ± 8.0 mL kg- 1 min- 1[Formula: see text]O2max) completed three exercise trials in environmental conditions of severe hypoxia (FIO2 0.114), moderate hypoxia (FIO2 0.152), and normoxia (FIO2 0.202). They were instructed to continually adjust their power output to maintain a perceived effort (RPE) of 16, exercising until power output declined to 80% of the peak 30-s power output achieved. RESULTS: Exercise time was reduced (severe hypoxia 428 ± 210 s; moderate hypoxia 1044 ± 384 s; normoxia 1550 ± 590 s) according to a reduction in FIO2 (P < 0.05). The rate of oxygen desaturation during the first 3 min of exercise was accelerated in severe hypoxia (- 5.3 ± 2.8% min- 1) relative to moderate hypoxia (- 2.5 ± 1.0% min- 1) and normoxia (- 0.7 ± 0.3% min- 1). Muscle tissue oxygenation did not differ between conditions (P > 0.05). Minute ventilation increased at a faster rate according to a decrease in FIO2 (severe hypoxia 27.6 ± 6.6; moderate hypoxia 21.8 ± 3.9; normoxia 17.3 ± 3.9 L min- 1). Moderate-to-strong correlations were identified between breathing frequency (r = - 0.718, P < 0.001), blood oxygen saturation (r = 0.611, P = 0.002), and exercise performance. CONCLUSIONS: The primary cues for determining perceived effort relate to progressive arterial hypoxemia and increases in ventilation.
Assuntos
Doença da Altitude/fisiopatologia , Condicionamento Físico Humano/métodos , Esforço Físico , Adulto , Método Duplo-Cego , Humanos , Masculino , Consumo de Oxigênio , Percepção , Condicionamento Físico Humano/efeitos adversosRESUMO
Ischaemic preconditioning (IPC) has emerged as a potential non-invasive ergogenic aid to enhance exercise performance. Repeated application of IPC has demonstrated clinical efficacy, therefore our aims were to investigate its effect on endurance cycling performance and muscle efficiency. Twenty participants undertook 7-d repeated bilateral lower limb occlusion (4 x 5-min) of IPC (220 mmHg) or sham (20 mmHg). Prior to and 72-h following the intervention, participants performed submaximal cycling at 70, 80 and 90% of ventilatory threshold (VT) followed by an incremental exercise test. IPC had no effect on VË O2max (P = 0.110); however, time to exhaustion increased by ~ 9% and Wmax by ~ 5 % (IPC pre 307 ± 45 to post 323 ± 51 W) relative to sham (P = 0.002). There were no changes in gross efficiency (GE) (P > 0.05); however, delta efficiency (DE) increased by 3.1% following IPC (P = 0.011). Deoxyhaemoglobin (HHb) was reduced following IPC ~ 30% (P = 0.017) with no change in total haemoglobin (tHb). Repeated IPC over 7-d enhanced muscle efficiency and extended cycling performance. The physiological effects of repeated IPC on skeletal muscle efficiency explains the notable improvements in endurance performance.
Assuntos
Desempenho Atlético/fisiologia , Ciclismo/fisiologia , Precondicionamento Isquêmico , Músculo Esquelético/fisiologia , Constrição , Estudos Cross-Over , Teste de Esforço , Hemoglobinas/análise , Humanos , Extremidade Inferior , Masculino , Consumo de Oxigênio , Método Simples-Cego , Espectroscopia de Luz Próxima ao Infravermelho , Adulto JovemRESUMO
This study investigated the effects of taurine on repeated sprint exercise, performed after fixed incremental ramp exercise to exhaustion at isokinetic high (90 r/min) or low (50 r/min) cadences. In a double-blind, repeated measures design, nine females completed an incremental ramp test to volitional exhaustion, followed by 2 min active recovery and 6 × 10 s sprints on a cycle ergometer, in one of four conditions: high cadence (90 r/min) + taurine (50 mg/kg body mass); high cadence + placebo (3 mg/kg body mass maltodextrin); low cadence (50 r/min) + taurine; low cadence + placebo. Heart rate (HR) and blood lactate concentration B[La] were measured before and after the ramp test and after the sprints. Taurine lowered HR vs. placebo prior to the ramp test (P = 0.004; d = 2.1). There was an effect of condition on ramp performance (P < 0.001), with higher end-test power (d = 3.7) in taurine conditions. During repeated sprints, there was a condition × time interaction (P = 0.002), with higher peak sprint power in the placebo conditions compared to taurine (sprint 2-6; P < 0.05). B[La] was higher in taurine compared to placebo post-ramp (P = 0.004; d = 4.7). Taurine-lowered pre-exercise HR and improved incremental end-test power output, with subsequent detrimental effects on sprint performance, independent of cadence. Short endurance performance can be acutely enhanced after taurine ingestion but this effect might not be maintained across longer periods of exercise or induce the need for longer recovery periods.
Assuntos
Ciclismo , Ácido Láctico/sangue , Taurina/administração & dosagem , Adolescente , Adulto , Método Duplo-Cego , Exercício Físico , Feminino , HumanosRESUMO
This study investigated the effects of leucine or leucine + glutamine supplementation on recovery from eccentric exercise. In a double-blind independent groups design, 23 men were randomly assigned to a leucine (0.087 g/kg; n = 8), leucine + glutamine (0.087 g/kg + glutamine 0.3 g/kg; n = 8) or placebo (0.3 g/kg maltodextrin; n = 7) group. Participants performed 5 sets of drop jumps, with each set comprising 20 repetitions. Isometric knee-extensor strength, counter-movement jump (CMJ) height, delayed-onset muscle soreness (DOMS) and creatine kinase (CK) were measured at baseline, 1, 24, 48 h and 72 h post-exercise. There was a time × group interaction for isometric strength, CMJ and CK (P < 0.05), with differences between the leucine + glutamine and placebo group at 48 h and 72 h for strength (P = 0.013; d = 1.43 and P < 0.001; d = 2.06), CMJ (P = 0.008; d = 0.87 and P = 0.019; d = 1.17) and CK at 24 h (P = 0.012; d = 0.54) and 48 h (P = 0.010; d = 1.37). The leucine group produced higher strength at 72 h compared to placebo (P = 0.007; d = 1.65) and lower CK at 24 h (P = 0.039; d = 0.63) and 48 h (P = 0.022; d = 1.03). Oral leucine or leucine + glutamine increased the rate of recovery compared to placebo after eccentric exercise. These findings highlight potential benefits of co-ingesting these amino acids to ameliorate recovery.
Assuntos
Suplementos Nutricionais , Exercício Físico/fisiologia , Glutamina/farmacologia , Leucina/farmacologia , Força Muscular/fisiologia , Mialgia/prevenção & controle , Adulto , Creatina Quinase/análise , Humanos , Contração Isométrica/fisiologia , Masculino , Força Muscular/efeitos dos fármacos , Adulto JovemRESUMO
PURPOSE OF REVIEW: The aims of this meta-analysis were to investigate the effects of orally administered isolated taurine on resting systolic blood pressure (SBP) and diastolic blood pressure (DBP) in humans. RECENT FINDINGS: There is growing evidence that taurine deficiency is associated with hypertension and that oral supplementation can have antihypertensive effects in humans. However, these investigations have been conducted across a number of decades and populations and have not been collectively reviewed. A search was performed using various databases in May 2018 and later screened using search criteria for eligibility. There were seven peer-reviewed studies meeting the inclusion criteria, encompassing 103 participants of varying age and health statuses. Taurine ingestion reduced SBP (Hedges' g = - 0.70, 95% CI - 0.98 to - 0.41, P < 0.0001) and DBP (Hedges' g = - 0.62, 95% CI - 0.91 to - 0.34, P < 0.0001). These results translated to mean ~ 3 mmHg reductions in both SBP (range = 0-15 mmHg) and DBP (range = 0-7 mmHg) following a range of doses (1 to 6 g/day) and supplementation periods (1 day to 12 weeks), with no adverse events reported. These preliminary findings suggest that ingestion of taurine at the stated doses and supplementation periods can reduce blood pressure to a clinically relevant magnitude, without any adverse side effects. Future studies are needed to establish the effects of oral taurine supplementation on targeted pathologies and the optimal supplementation doses and periods.
Assuntos
Pressão Sanguínea/efeitos dos fármacos , Suplementos Nutricionais , Taurina/administração & dosagem , Diástole/efeitos dos fármacos , Humanos , Sístole/efeitos dos fármacosRESUMO
PURPOSE: This study investigated the effects of L-menthol mouth rinse and ice slurry ingestion on time to exhaustion, when administered at the latter stages (~ 85%) of baseline exercise duration in the heat (35 °C). METHOD: Ten male participants performed four time to exhaustion (TTE) trials on a cycle ergometer at 70% Wmax. In a randomized crossover design, (1) placebo-flavored non-calorific mouth rinse, (2) L-menthol mouth rinse (0.01%), or (3) ice ingestion (1.25 g kg-1), was administered at 85% of participants' baseline TTE. Time to exhaustion, core and skin temperature, heart rate, rating of perceived effort, thermal comfort and thermal sensation were recorded. RESULTS: From the point of administration at 85% of baseline TTE, exercise time was extended by 1% (placebo, 15 s), 6% (L-menthol, 82 s) and 7% (ice, 108 s), relative to baseline performance (P = 0.036), with no difference between L-menthol and ice (P > 0.05). Core temperature, skin temperature, and heart rate increased with time but did not differ between conditions (P > 0.05). Thermal sensation did not differ significantly but demonstrated a large effect size (P = 0.080; [Formula: see text] = 0.260). CONCLUSION: These results indicate that both thermally cooling and non-thermally cooling oral stimuli have an equal and immediate behavioral, rather than physiological, influence on exhaustive exercise in the heat.
Assuntos
Desempenho Atlético/fisiologia , Temperatura Corporal/fisiologia , Exercício Físico/fisiologia , Gelo , Mentol/administração & dosagem , Adulto , Temperatura Corporal/efeitos dos fármacos , Regulação da Temperatura Corporal/efeitos dos fármacos , Regulação da Temperatura Corporal/fisiologia , Estudos Cross-Over , Temperatura Alta , Humanos , Masculino , Antissépticos Bucais , Esforço Físico/fisiologia , Adulto JovemRESUMO
This study investigated the effects of a mentally fatiguing test on physical tasks among elite cricketers. In a cross-over design, 10 elite male cricket players from a professional club performed a cricket run-two test, a Batak Lite reaction time test and a Yo-Yo-Intermittent Recovery Level 1 (Yo-Yo-IR1) test, providing a rating of perceived exertion (RPE) after completing a 30-min Stroop test (mental fatigue condition) or 30-min control condition. Perceived fatigue was assessed before and after the two conditions and motivation was measured before testing. There were post-treatment differences in the perception of mental fatigue (P < 0.001; d = -7.82, 95% CIs = -9.05-6.66; most likely). Cricket run-two (P = 0.002; d = -0.51, 95% CIs = -0.72-0.30; very likely), Yo-Yo-IR1 distance (P = 0.023; d = 0.39, 95% CIs = 0.14-0.64; likely) and RPE (P = 0.001; d = -1.82, 95% CIs = -2.49-1.14; most likely) were negatively affected by mental fatigue. The Batak Lite test was not affected (P = 0.137), yet a moderate (d = 0.41, 95% CIs = -0.05-0.87) change was likely. Mental fatigue, induced by an app-based Stroop test, negatively affected cricket-relevant performance.
Assuntos
Fadiga Mental/psicologia , Resistência Física , Esportes/psicologia , Estudos Cross-Over , Humanos , Masculino , Motivação/fisiologia , Percepção/fisiologia , Esforço Físico/fisiologia , Tempo de Reação/fisiologia , Teste de Stroop , Adulto JovemRESUMO
INTRODUCTION: The effect of eccentric exercise-induced muscle damage (EIMD) on cycling efficiency is unknown. The aim of the present study was to assess the effect of EIMD on gross and delta efficiency and the cardiopulmonary responses to cycle ergometry. METHODS: Twenty-one recreational athletes performed cycling at 70%, 90%, and 110% of the gas exchange threshold (GET) under control conditions (Control) and 24 h following an eccentric damaging protocol (Damage). Knee extensor isometric maximal voluntary contraction, potentiated twitch ( Qtw,pot ), and voluntary activation were assessed before Control and Damage. Gross and delta efficiency were assessed using indirect calorimetry, and cardiopulmonary responses were measured at each power output. Electromyography root-mean-square (EMG RMS ) during cycling was also determined. RESULTS: Maximal voluntary contraction was 25% ± 18% lower for Damage than Control ( P < 0.001). Gross efficiency was lower for Damage than Control ( P < 0.001) by 0.55% ± 0.79%, 0.59% ± 0.73%, and 0.60% ± 0.87% for 70%, 90%, and 110% GET, respectively. Delta efficiency was unchanged between conditions ( P = 0.513). Concurrently, cycling EMG RMS was higher for Damage than Control ( P = 0.004). An intensity-dependent increase in breath frequency and VÌ E /VÌCO 2 was found, which were higher for Damage only at 110% GET ( P ≤ 0.019). CONCLUSIONS: Thus, gross efficiency is reduced following EIMD. The concurrently higher EMG RMS suggests that increases in muscle activation in the presence of EIMD might have contributed to reduced gross efficiency. The lack of change in delta efficiency might relate to its poor reliability hindering the ability to detect change. The findings also show that EIMD-associated hyperventilation is dependent on exercise intensity, which might relate to increases in central command with EIMD.
Assuntos
Ciclismo , Eletromiografia , Músculo Esquelético , Humanos , Masculino , Músculo Esquelético/lesões , Músculo Esquelético/fisiologia , Músculo Esquelético/fisiopatologia , Adulto , Adulto Jovem , Ciclismo/fisiologia , Consumo de Oxigênio/fisiologia , Contração Isométrica/fisiologia , Feminino , Troca Gasosa Pulmonar , Exercício Físico/fisiologia , Teste de Esforço , Calorimetria IndiretaRESUMO
Protein palmitoylation is a major dynamic posttranslational regulator of protein function. However, mechanisms that control palmitoylation are poorly understood. In many proteins, palmitoylation occurs at cysteine residues juxtaposed to membrane-anchoring domains such as transmembrane helices, sites of irreversible lipid modification, or hydrophobic and/or polybasic domains. In particular, polybasic domains represent an attractive mechanism to dynamically control protein palmitoylation, as the function of these domains can be dramatically influenced by protein phosphorylation. Here we demonstrate that a polybasic domain immediately upstream of palmitoylated cysteine residues within an alternatively spliced insert in the C terminus of the large conductance calcium- and voltage-activated potassium channel is an important determinant of channel palmitoylation and function. Mutation of basic amino acids to acidic residues within the polybasic domain results in inhibition of channel palmitoylation and a significant right-shift in channel half maximal voltage for activation. Importantly, protein kinase A-dependent phosphorylation of a single serine residue within the core of the polybasic domain, which results in channel inhibition, also reduces channel palmitoylation. These data demonstrate the key role of the polybasic domain in controlling stress-regulated exon palmitoylation and suggests that phosphorylation controls the domain by acting as an electrostatic switch.
Assuntos
Ativação do Canal Iônico/fisiologia , Canais de Potássio Ativados por Cálcio de Condutância Alta/metabolismo , Lipoilação/fisiologia , Processamento de Proteína Pós-Traducional/fisiologia , Animais , Células HEK293 , Humanos , Canais de Potássio Ativados por Cálcio de Condutância Alta/genética , Camundongos , Fosforilação/fisiologia , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Eletricidade EstáticaRESUMO
The factors explaining variance in thermoneutral maximal oxygen uptake (VËO2max) adaptation to heat acclimation (HA) were evaluated, with consideration of HA programme parameters, biophysical variables and thermo-physiological responses. Seventy-one participants consented to perform iso-intensity training (range: 45%-55% VËO2max) in the heat (range: 30°C-38°C; 20%-60% relative humidity) on consecutive days (range: 5-days-14-days) for between 50-min and-90 min. The participants were evaluated for their thermoneutral VËO2max change pre-to-post HA. Participants' whole-body sweat rate, heart rate, core temperature, perceived exertion and thermal sensation and plasma volume were measured, and changes in these responses across the programme determined. Partial least squares regression was used to explain variance in the change in VËO2max across the programme using 24 variables. Sixty-three percent of the participants increased VËO2max more than the test error, with a mean ± SD improvement of 2.6 ± 7.9%. A two-component model minimised the root mean squared error and explained the greatest variance (R2; 65%) in VËO2max change. Eight variables positively contributed (P < 0.05) to the model: exercise intensity (%VËO2max), ambient temperature, HA training days, total exposure time, baseline body mass, thermal sensation, whole-body mass losses and the number of days between the final day of HA and the post-testing day. Within the ranges evaluated, iso-intensity HA improved VËO2max 63% of the time, with intensity - and volume-based parameters, alongside sufficient delays in post-testing being important considerations for VËO2max maximisation. Monitoring of thermal sensation and body mass losses during the programme offers an accessible way to gauge the degree of potential adaptation.
Assuntos
Aclimatação , Temperatura Alta , Humanos , Aclimatação/fisiologia , Consumo de Oxigênio/fisiologia , Adaptação Fisiológica , Sudorese , Frequência CardíacaRESUMO
We determined the effects of topically applied (i) isolated menthol cream, (ii) menthol and capsaicin co-application or (iii) placebo cream on exercise tolerance, thermal perception, pain, attentional focus and thermoregulation during exercise in the heat. Ten participants cycled at 70% maximal power output until exhaustion in 35°C and 20% relative humidity after application of (i) 5% isolated menthol, (ii) 5% menthol and 0.025% capsaicin co-application or (iii) placebo cream. Thermo-physiological responses were measured during exercise, with attentional focus and pain determined post-exercise on a 0-to-10 scale. Across the three conditions, time to exhaustion was 13.4 ± 4.8â min, mean ± SD infrared tympanic and skin temperature was 37.2 ± 0.6°C and 35.1 ± 1.2°C, respectively, and heart rate was 152 ± 47 bpm, with no changes between conditions (p > 0.05). Perceived exertion was lower in the isolated menthol vs. all other conditions (p < 0.05, ηp2 = 0.44). Thermal sensation was higher in menthol-capsaicin co-application vs. isolated menthol (p < 0.05, d = 1.1), while sweat rate was higher for capsaicin and menthol co-application compared to menthol (p < 0.05, d = 0.85). The median and interquartile range scores for pain were lower (p < 0.05) in the menthol condition (8, 7-8) compared to both menthol and capsaicin (10, 9-10) and placebo (9, 9-10), which was coupled with a greater distraction (p < 0.05) in the menthol condition (9, 7-10) compared to placebo (6, 5-7). Despite no performance effects for any topical cream application condition, these data reiterate the advantageous perceptual and analgesic role of menthol application and demonstrate no advantage of co-application with capsaicin.HighlightsTopical application of isolated menthol cream to cold-sensitive areas of the body during exhaustive exercise in the heat, elicited reduced perception of pain and enhanced sensation of cooling.While this reduction in generally unpleasant feelings (i.e. pain and heat) were coupled with lower RPE scores in the menthol condition and could be considered beneficial, there was no apparent ergogenic effect in an exercise tolerance test.Co-application of capsaicin and menthol appeared to inhibit the positive sensory effects elicited by menthol.Isolated menthol can induce changes in cognitive processes related to pain and exertion, while also reducing thermal sensation; however, the decision to use menthol creams must be balanced with the limited performance or thermoregulatory effects reported herein during exercise in hot environments.
Assuntos
Capsaicina , Mentol , Humanos , Regulação da Temperatura Corporal/fisiologia , Capsaicina/farmacologia , Tolerância ao Exercício , Temperatura Alta , Mentol/farmacologia , Dor , Percepção da Dor , Sensação Térmica , Estudos Cross-Over , Masculino , Feminino , AdultoRESUMO
AbstractWe investigated the effects of taurine supplementation on cycling time to exhaustion in cold conditions. Eleven males cycled to exhaustion at a power output equivalent to the mid-point between ventilatory threshold and maximum aerobic power following 15-min rest in the cold (apparent temperature of â¼ 4°C; air flow of 4.17â mâ s-1). Two hours before, participants ingested taurine (50â mg·kg-1) or placebo beverage. Pulmonary gases, carbohydrate (CHO) and fat oxidation, body temperatures, mean local sweat rate, heart rate, rate of perceived exertion (RPE) and thermal comfort were recorded. Time to exhaustion was not different between trials (taurine = 14.6 ± 4.7â min; placebo = 13.4 ± 5.6â min, P = 0.061, d = 0.27). There were no effects (P > 0.05) of taurine on core temperature, mean skin temperature or local sweat rates. However, the placebo condition showed greater (P < 0.05) reductions in arm-to-finger temperature gradient (i.e. vasodilation) across pre-exercise passive cold exposure and increased CHO oxidation (P < 0.05). Participants also reached a thermally 'comfortable' level quicker in the taurine condition (P < 0.05). A 50â mg·kg-1 dose of taurine did not statistically benefit endurance exercise after moderate cold exposure but conferred some potential vascular and metabolic effects.