Dose-response effects of caffeine during repeated cycling sprints in normobaric hypoxia to exhaustion.

PURPOSE: With limited studies exploring the dose-response of caffeine consumption on repeated sprint ability in hypoxia, this study aimed to determine the optimal caffeine dose (low, moderate or high) during repeated sprints in hypoxia to exhaustion. METHODS: On separate visits, twelve active males randomly performed four experimental trials in normobaric hypoxia (inspired oxygen fraction: 16.5 ± 0.2%). Participants ingested placebo (PLA) or caffeine capsules (3, 6 or 9 mg/kg or LOW, MOD and HIGH, respectively) 1 h before exercise and then underwent a repeated cycling sprint test (10 s sprint/20 s active recovery) to exhaustion. Total sprint number and work done, peak and mean power output, blood lactate concentration, cardiorespiratory and perceptual responses were recorded. RESULTS: Total sprint number was greater in MOD and HIGH compared to PLA (20 ± 7 and 18 ± 8 vs. 13 ± 4; all P < 0.05), with MOD also higher than LOW (15 ± 6; P = 0.02). Total work done was greater in MOD (111 ± 40 kJ) and HIGH (100 ± 35 kJ) compared to LOW (83 ± 29 kJ) and PLA (76 ± 25 kJ) (all P < 0.05). However, there were no significant differences in total sprint number or total work done between MOD and HIGH (all P > 0.05). Blood lactate concentration was higher in both MOD and HIGH compared to PLA (all P < 0.05). However, peak and mean power outputs, fatigue index, and ratings of perceived exertion did not differ across different caffeine dosages (all P > 0.05). CONCLUSION: A moderate dose of caffeine (6 mg/kg) is the optimal amount for enhancing repeated cycling sprint ability when compared to low and high doses in moderate normobaric hypoxia.

Metabolic, cognitive and neuromuscular responses to different multidirectional agility-like sprint protocols in elite female soccer players - a randomised crossover study.

PURPOSE: Resistance to fatigue is a key factor in injury prevention that needs to be considered in return-to-sport (RTS) scenarios, especially after severe knee ligament injuries. Fatigue should be induced under game-like conditions. The SpeedCourt (SC) is a movement platform for assessing multidirectional sprint performance, typical of game-sports, due to change-of-direction movements in response to a visual stimulus. Designing adequate fatigue protocols requires the suitable arrangement of several loading variables such as number of intervals, sprint distance or work/relief ratio (W:R). Therefore, this study analysed the acute fatigue effects of different SC protocols on metabolic load, cognitive function and neuromuscular performance. METHODS: Eighteen female soccer players (mean ± SD; age: 23.1 ± 4.6 years) of the 1st German Division participated in this randomised, crossover study. Using a random allocation sequence, players completed four volume-equated protocols differing in W:R and sprint distance per interval (P1:12 × 30 m, W:R = 1:2 s; P2:12 × 30 m, W:R = 1:3 s; P3:18 × 20 m, W:R = 1:2 s; P4:18 × 20 m, W:R = 1:3 s). Pre- and post-exercise, metabolic load was measured per blood lactate concentration (BLaC), cognitive function per reaction time (RT), and neuromuscular performance including multiple rebound jumps (MRJ height, primary outcome variable; Reactive Strength Index, RSI) and 5 m sprint times (SP5). RESULTS: Repeated-measures ANOVA revealed significant main time effects (p < .05) with improved performance post-exercise in RT (504 vs. 482 ms, d = 1.95), MRJ height (24.0 vs. 24.8 cm, d = 0.77), RSI (1.39 vs. 1.43, d = 0.52), and SP5 (1.19 vs. 1.17 s, d = 0.56). There was significant main time (p < .001) and time x protocol interaction effects in BLaC (p < .001). P1 induced higher BLaC values (4.52 ± 1.83 mmol/L) compared to P2 (3.79 ± 1.83 mmol/L; d = 0.74) and P4 (3.12 ± 1.83 mmol/L; d = 1.06), whereas P3 (4.23 ± 1.69 mmol/L) elicited higher BLaC values compared to P4 (d = 0.74). CONCLUSION: All protocols caused an improved cognitive function and neuromuscular performance. The former may be related to enhanced noradrenergic activation or exercise specificity which induced an improved stimulus processing. The latter may be explained by a possible post-activation performance enhancement effect on jump and sprint performance. A shorter relief duration in W:R as opposed to sprint distance per interval produced higher BLaC values. The protocols may serve as reference data for improved RTS decision-making in elite female soccer players. TRIAL REGISTRATION: Deutsches Register Klinischer Studien (DRKS), No.: DRKS00033496 , Registered 19. Februar 2024, Retrospectively Registered.

Effects of a Singular Dose of Mangiferin-Quercetin Supplementation on Basketball Performance: A Double-Blind Crossover Study of High-Level Male Players.

Pre-exercise mangiferin-quercetin may enhance athletic performance. This study investigated the effect of mangiferin-quercetin supplementation on high-level male basketball players during a basketball exercise simulation test (BEST) comprising 24 circuits of 30 s activities with various movement distances. The participants were divided into two groups (EXP = 19 and CON = 19) and given a placebo one hour before the BEST (PRE-condition). The following week, the EXP group received mangiferin-quercetin (84 mg/140 mg), while the CON group received a placebo (POST-condition) before the BEST in a double-blind, cross-over design. The mean heart rate (HR) and circuit and sprint times (CT and ST) during the BEST were measured, along with the capillary blood lactate levels (La-), the subjective rating of muscle soreness (RPMS), and the perceived exertion (RPE) during a resting state prior to and following the BEST. The results showed significant interactions for the mean CT (p = 0.013) and RPE (p = 0.004); a marginal interaction for La- (p = 0.054); and non-significant interactions for the mean HR, mean ST, and RPMS. Moreover, the EXP group had significantly lower values in the POST condition for the mean CT (18.17 ± 2.08 s) and RPE (12.42 ± 1.02) compared to the PRE condition (20.33 ± 1.96 s and 13.47 ± 1.22, respectively) and the POST condition of the CON group (20.31 ± 2.10 s and 13.32 ± 1.16, respectively) (p < 0.05). These findings highlight the potential of pre-game mangiferin-quercetin supplementation to enhance intermittent high-intensity efforts in sports such as basketball.

Repeated-Sprint Training With Blood-Flow Restriction Improves Repeated-Sprint Ability Similarly to Unrestricted Training at Reduced External Loads.

PURPOSE: This study examined performance and physiological adaptations following 3 weeks of repeated-sprint training (RST) with blood-flow restriction (BFR) or without (non-BFR). METHODS: Twenty-six semiprofessional and amateur adult male team-sport players were assessed for repeated-sprint ability, anaerobic capacity, leg lean mass, neuromuscular function, and maximal aerobic capacity before and after RST. Participants completed 9 cycling RST sessions (3 sets of 5-7 × 5-s sprints, 25-s passive recovery, 3-min rest) over a 3-week period with BFR or non-BFR. RESULTS: During RST sessions, the BFR group demonstrated lower mean power output compared with non-BFR (-14.5%; g = 1.48; P = .001). Significant improvements (P < .05) in mean and peak power output during repeated-sprint ability (+4.1%; g = 0.42, and + 2.2%; g = 0.25, respectively) and anaerobic capacity (+4.8%; g = 0.47, and + 4.7%; g = 0.32, respectively) tests, leg lean mass (+2.0%; g = 0.16), and peak aerobic power (+3.3%; g = 0.25) were observed from pretesting to posttesting without any between-groups differences. No significant changes (P > .05) were observed for maximal isometric voluntary contraction and maximal aerobic capacity. Peak rate of force development decreased (P = .003) in both groups following RST (-14.6%; g = 0.65), without any between-groups differences. CONCLUSIONS: Repeated-sprint ability, anaerobic capacity, leg lean mass, and peak aerobic power improved following 3 weeks of RST; however, the addition of BFR did not further enhance adaptations. Interestingly, comparable improvements were achieved between groups despite lower external loads experienced during RST sessions with BFR.

Acute consumption of a branched chain amino acid and vitamin B-6 containing sports drink does not improve multiple sprint exercise performance, but increases post-exercise blood glucose.

Purpose: The aim of this study was to investigate the ergogenicity of BioSteel High Performance Sports Drink (B-HPSD), a commercially available branched chain amino acid (BCAA) and vitamin B-6 (VitB-6) supplement, on multiple sprint exercise (MSE). Methods: Eleven experienced cyclists completed two MSE trials in counterbalanced order, after ingesting either B-HPSD (2,256 mg of BCAA, 300 mcg of VitB-6) or placebo (PLA). The MSE protocol consisted of five maximal effort 1 km sprints on a cycle ergometer separated by 2 min of active recovery. Power output (PO) was continuously measured throughout the cycling protocol. Heart rate (HR) and ratings of perceived exertion (RPE) were monitored following each sprint. Capillary blood samples were collected and analyzed for lactate and glucose before and 2 min post-trial. Cognitive function was assessed before and 15 min after the exercise protocol. Results: The PO maintained during each 1 km sprint decreased throughout the protocol (p < 0.05), but the change in PO was similar between conditions. Post-exercise blood glucose was elevated after consuming B-HPSD but not PLA (p < 0.05). Blood lactate (p < 0.05), HR (p < 0.05) and RPE (p < 0.05) increased throughout the trials, however no differences were observed between conditions. Cognitive performance improved after exercise (p < 0.05), but the change was similar between conditions. Conclusion: These results demonstrate that acute B-HPSD consumption does not have an ergogenic effect on MSE performance. However, ingestion of B-HPSD increased post-exercise blood glucose concentration when compared to PLA.

Skeletal Muscle Transcriptomic Comparison Between Men and Women in Response to Acute Sprint Exercise.

Background: Acute sprint exercise is a time-efficient physical activity that improves cardiorespiratory fitness in younger and middle-aged adults. Growing evidence has demonstrated that acute sprint exercise provides equal to or superior health benefits compared with moderate-intensity continuous training, which will dramatically increase aerobic capacity, insulin sensitivity, and muscle capillarization. Although the beneficial effects of acute sprint exercise are well documented, the mechanisms behind how acute sprint exercise prevents disease and benefits health are less understood. Method: We obtained differentially expressed genes in muscle (vastus lateralis) from men and women before and after an acute sprint exercise. Then, we identified hub genes from the protein-protein interaction (PPI) network of differentially expressed genes (DEGs) and key transcription factors in men and women related to acute sprint exercise. Finally, Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment analyses are performed on DEGs and sex-biased genes, respectively. Results: First, we identified 127 sexually dimorphic genes in men (90 upregulated and 37 downregulated) and 75 genes in women (90 upregulated and 37 downregulated) in response to acute sprint exercise. Second, CEBPB, SMAD3, and CDKN1A are identified as the top three hub genes related to men-biased genes. Accordingly, the top three hub genes related to women-biased genes are JUN, ACTB, and SMAD7. In addition, CLOCK, ZNF217, and KDM2B are the top three enriched transcriptional factors in men-biased genes, while XLR, SOX2, JUND, and KLF4 are transcription factors enriched most in women-biased genes. Furthermore, based on GO and KEGG enrichment analyses, we identified potential key pathways in regulating the exercise-related response in men and women, respectively. Conclusion: In this study, we found the difference in gene expression and enrichment pathways in muscle in men and women in response to acute sprint exercise. These results will shed new light on the mechanism underlying sex-based differences in skeletal muscle remodeling and metabolism related to acute sprint exercise, which may illustrate the mechanisms behind how acute sprint exercise prevents disease and benefits health.

Effects of Intermittent Energy Restriction Alone and in Combination with Sprint Interval Training on Body Composition and Cardiometabolic Biomarkers in Individuals with Overweight and Obesity.

The popularity of intermittent fasting (IF) and high intensity (sprint) interval training (SIT) has increased in recent years amongst the general public due to their purported health benefits and feasibility of incorporation into daily life. The number of scientific studies investigating these strategies has also increased, however, very few have examined the combined effects, especially on body composition and cardiometabolic biomarkers, which is the primary aim of this investigation. A total of thirty-four male and female participants (age: 35.4 ± 8.4 y, body mass index (BMI): 31.3 ± 3.5 kg/m2, aerobic capacity (VO2peak) 27.7 ± 7.0 mL·kg−1·min−1) were randomized into one of three 16-week interventions: (1) 5:2 IF (2 non-consecutive days of fasting per week, 5 days on ad libitum eating), (2) supervised SIT (3 bouts per week of 20s cycling at 150% VO2peak followed by 40 s of active rest, total 10 min duration), and (3) a combination of both interventions. Body composition, haemodynamic and VO2peak were measured at 0, 8 and 16 weeks. Blood samples were also taken and analysed for lipid profiles and markers of glucose regulation. Both IF and IF/SIT significantly decreased body weight, fat mass and visceral fat compared to SIT only (p < 0.05), with no significant differences between diet and diet + exercise combined. The effects of diet and/or exercise on cardiometabolic biomarkers were mixed. Only exercise alone or with IF significantly increased cardiorespiratory fitness. The results suggest that energy restriction was the main driver of body composition enhancement, with little effect from the low volume SIT. Conversely, to achieve benefits in cardiorespiratory fitness, exercise is required.

Effects of sodium pyruvate supplementation on repeated sprint exercise performance and recovery in male college soccer players: a randomized controlled trial.

BACKGROUND: Sodium pyruvate (PYR) has been reported to improve aerobic metabolism and attenuate metabolic acidosis. Aerobic capacity and the ability to remove hydrogen ions affect the recovery from repeated high intensity activities. However, the effects of PYR supplementation on repeated sprint exercise (RSE) performance have not been elucidated. This study explored the effects of PYR ingestion on RSE ability and recovery. METHODS: A total of 14 male soccer athletes (aged 20±2 years) participated in this double-blinded crossover study. The subjects completed two experimental sessions after randomized ingestion of either PYR or the maltodextrin placebo (PLA) for 1 week. At each session, participants completed high-intensity interval exercise (HIIE) and RSE 60 minutes after supplementation. Additionally, acid-base parameters in venous blood, energy system contributions, and power output were assessed. RESULTS: Compared to PLA, PYR supplementation significantly increased the relative peak power output (PPO) of the first (P=0.034) and fifth (P=0.043) sprints, and the relative mean power output (MPO) of the fifth sprint (P=0.026). In addition, the mean PPO (P=0.031) and MPO (P=0.033) of sprints 1-6 were significantly elevated after PYR supplementation. After PYR administration, the phosphagen energy system [adenosine triphosphate (ATP)-phosphocreatine (PCr)] resynthesis of the fourth (P=0.034) and the overall recovery periods during HIIE (P=0.029) were higher than PLA administration. Additionally, the ATP-PCr resynthesis of the first (P=0.033) and fifth (P=0.019) recovery periods, and the mean of the six recovery periods during RSE (P=0.041) were increased in the PYR group compared to the PLA group. Furthermore, participants on the PYR regimen had higher blood pH, HCO3-, and base excess at pre-HIIE, post-HIIE, and pre-RSE (all P<0.05) compared to participants receiving PLA. CONCLUSIONS: PYR supplementation enhanced RSE performance, and the improvement may be attributed to accelerated restoration of the acid-base balance and ATP-PCr regeneration. TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTR2100053936.

A High-Intensity Warm-Up Increases Thermal Strain But Does Not Affect Repeated Sprint Performance in Athletes With a Cervical Spinal Cord Injury.

PURPOSE: To compare the effects of typical competition versus high-intensity intermittent warm-up (WU) on thermoregulatory responses and repeated sprint performance during wheelchair rugby game play. METHODS: An intermittent sprint protocol (ISP) simulating the demands of wheelchair rugby was performed by male wheelchair rugby players (7 with cervical spinal cord injury [SCI] and 8 without SCI) following 2 WU protocols. These included a typical competition WU (control) and a WU consisting of high-intensity efforts (INT). Core temperature (Tcore), thermal sensation, and thermal comfort were recorded. Wheelchair performance variables associated to power, speed, and fatigue were also calculated. RESULTS: During the WU, Tcore was similar between conditions for both groups. During the ISP, a higher Tcore was found for SCI compared to NON-SCI (38.1 [0.3] vs 37.7 [0.3] °C: P = .036, d = 0.75), and the SCI group experienced a higher peak Tcore for INT compared with control (39.0 [0.4] vs 38.6 [0.6] °C; P = .004). Peak Tcore occurred later in the ISP for players with SCI (96 [5.8] vs 48 [2.7] min; P < .001). All players reported a higher thermal sensation and thermal comfort following INT (P < .001), with no differences between conditions throughout the ISP. No significant differences were found in wheelchair performance variables during the ISP between conditions (P ≥ .143). CONCLUSIONS: The high-INT WU increased thermal strain in the SCI group during the ISP, potentially due to increased metabolic heat production and impaired thermoregulation, while not impacting on repeated sprint performance. It may be advisable to limit high-INT bouts during a WU in players with SCI to mitigate issues related to hyperthermia in subsequent performance.

Neuromuscular fatigue of the elbow flexors during repeated maximal arm cycling sprints: the effects of forearm position.

Repeated sprint exercise (RSE) is often used to induce neuromuscular fatigue (NMF). It is currently not known whether NMF is influenced by different forearm positions during arm cycling RSE. The purpose of this study was to investigate the effects of a pronated versus supinated forearm position on elbow flexor NMF during arm cycling RSE. Participants (n = 12) completed ten 10-s maximal arm cycling sprints interspersed by 60 s of rest on 2 separate days using either a pronated or supinated forearm position. All sprints were performed on an arm cycle ergometer in a reverse direction. Prior to and following RSE, NMF measurements (i.e., maximal voluntary contraction (MVC), potentiated twitch (PT), electromyography median frequencies) were recorded. Sprint performance measures, ratings of perceived exertion (RPE) and pain were also recorded. Irrespective of forearm position, sprint performance decreased as sprint number increased. These decreases were accompanied by significant increases in RPE (p < 0.001, ηp2 = 0.869) and pain (p < 0.001, ηp2 = 0.745). Participants produced greater power output during pronated compared with supinated sprinting (p < 0.001, ηp2 = 0.728). At post-sprinting, the percentage decrease in elbow flexor MVC and PT force from pre-sprinting was significantly greater following supinated than pronated sprinting (p < 0.001), suggesting greater peripheral fatigue occurred in this position. The data suggest that supinated arm cycling RSE results in inferior performance and greater NMF compared with pronated arm cycling RSE. Novelty: NMF of the elbow flexors is influenced by forearm position during arm cycling RSE. Supinated arm cycling sprints resulted in worse repeated sprint performance and also greater NMF than pronated RSE.

Effect of Acute Sprint Exercise on Myokines and Food Intake Hormones in Young Healthy Men.

Physical exercise is known to influence hormonal mediators of appetite, but the effect of short-term maximal intensity exercise on plasma levels of appetite hormones and cytokines has been little studied. We investigated the effect of a 30 s Wingate Test, followed by a postprandial period, on appetite sensations, food intake, and appetite hormones. Twenty-six physically active young males rated their subjective feelings of hunger, prospective food consumption, and fatigue on visual analogue scales at baseline, after exercise was completed, and during the postprandial period. Blood samples were obtained for the measurement of nesfatin-1, ghrelin, leptin, insulin, pancreatic polypeptide (PP), human growth factor (hGH) and cytokine interleukin-6 (IL-6), irisin and plasma lactate concentrations, at 30 min before exercise, immediately (210 s) after exercise, and 30 min following a meal and at corresponding times in control sedentary males without ad libitum meal intake, respectively. Appetite perceptions and food intake were decreased in response to exercise. Plasma levels of irisin, IL-6, lactate, nesfatin-1 and ghrelin was increased after exercise and then it was returned to postprandial/control period in both groups. A significant rise in plasma insulin, hGH and PP levels after exercise was observed while meal intake potentiated this response. In conclusion, an acute short-term fatiguing exercise can transiently suppress hunger sensations and food intake in humans. We postulate that this physiological response involves exercise-induced alterations in plasma hormones and the release of myokines such as irisin and IL-6, and supports the notion of existence of the skeletal muscle-brain-gut axis. Nevertheless, the detailed relationship between acute exercise releasing myokines, appetite sensations and impairment of this axis leading to several diseases should be further examined.

Influence of sprint exercise on aortic pulse wave velocity and femoral artery shear patterns.

PURPOSE: Aortic stiffness may affect shear patterns in the peripheral vasculature. This study examined if sprint exercise, which typically increases aortic stiffness is associated with increased peripheral retrograde blood flow and impaired microvascular function. METHODS: Twenty participants (10 women; age: 27 ± 5 years) underwent arterial stiffness, shear rate, and microvascular function assessment at three time points: baseline; following time control; ~ 2 min post a 30-s cycle ergometer sprint against 7.0% body mass. Aortic stiffness was assessed using carotid-femoral pulse wave velocity (cfPWV). Superficial femoral artery (SFA) diameter and blood velocity were assessed using Doppler-ultrasound and were used to calculate shear rates and resistance index (RI). SFA wave reflections were obtained via wave intensity analysis. Vastus medialis microvascular function was measured as tissue saturation index reactivity pre-post exercise via near-infrared spectroscopy. RESULTS: cfPWV increased by + 0.8 ± 0.7 m·s-1 following exercise (p < 0.001). Retrograde shear was reduced following exercise compared with time control (- 4.9 ± 3.8 s-1; p < 0.001), while tissue saturation index was increased post-exercise from baseline (+ 2.3 ± 4.6%; p = 0.04). Reductions in SFA wave reflections (- 1.70 ± 1.96 aU) and RI (- 0.17 ± 0.13 aU) were also noted following exercise (p < 0.001). CONCLUSION: These data suggest sprint exercise-mediated changes in peripheral shear patterns and microvascular function in the exercised vasculature occur independent from increases in aortic stiffness. Exercise-induced reductions in SFA retrograde shear may be related to decreased wave reflections and peripheral vascular resistance.

Modulation of Endothelial Glycocalyx and Microcirculation in Healthy Young Men during High-Intensity Sprint Interval Cycling-Exercise by Supplementation with Pomegranate Extract. A Randomized Controlled Trial.

The natural components of the pomegranate fruit may provide additional benefits for endothelial function and microcirculation. It was hypothesized that supplementation with pomegranate extract might improve glycocalyx properties and microcirculation during acute high-intensity sprint interval cycling exercise. Eighteen healthy and recreationally active male volunteers 22-28 years of age were recruited randomly to the experimental and control groups. The experimental group was supplemented with pomegranate extract 20 mL (720 mg phenolic compounds) for two weeks. At the beginning and end of the study, the participants completed a high-intensity sprint interval cycling-exercise protocol. The microcirculation flow and density parameters, glycocalyx markers, systemic hemodynamics, lactate, and glucose concentration were evaluated before and after the initial and repeated (after 2 weeks supplementation) exercise bouts. There were no significant differences in the microcirculation or glycocalyx over the course of the study (p < 0.05). The lactate concentration was significantly higher in both groups after the initial and repeated exercise bouts, and were significantly higher in the experimental group compared to the control group after the repeated bout: 13.2 (11.9-14.8) vs. 10.3 (9.3-12.7) mmol/L, p = 0.017. Two weeks of supplementation with pomegranate extract does not influence changes in the microcirculation and glycocalyx during acute high-intensity sprint interval cycling-exercise. Although an unexplained rise in blood lactate concentration was observed.

Metabolic and Biomolecular Changes Induced by Incremental Long-Term Training in Young Thoroughbred Racehorses during First Workout Season.

Training has a huge effect on physiological homeostasis. The Thoroughbred racehorse is a valid animal model to investigate such changes for training schedule fine-tuning. As happens in human athletes, it is hypothesized that biochemical and immune response changes and related biomolecular variations could be induced by training programs. The aim of this study was to investigate, for the first time, the long-term metabolic and biomolecular modifications in young untrained Thoroughbred racehorses in the first 4-month timeframe training period. Twenty-nine clinically healthy, untrained, two-year-old Thoroughbred racehorses were followed during their incremental 4-month sprint exercise schedule. Blood collection was performed once a month, five times (T-30, T0, T30, T60, and T90). For each sample, lactate concentration, plasma cell volume (PCV), and hematobiochemical parameters (glucose, urea, creatinine, aspartate aminotransferase (AST), γ-glutamyltransferase (GGT), alkaline phosphatase (ALP), total bilirubin (Tbil), lactate dehydrogenase (LDH), creatine kinase (CK), cholesterol, triglycerides, albumin (Alb), total proteins (TPs), phosphorus (P), calcium (Ca2+), magnesium (Mg), sodium (Na+), potassium (K-), and chloride (Cl)) were determined. At T-30 and T90, serum protein electrophoresis (SPE), serum amyloid A (SAA), and real-time qPCR were performed on all samples to evaluate the expression of key genes and cytokines related to inflammatory and Th2 immunity responses: Interleukin-4 (IL-4), Interleukin-6 (IL-6), Interleukin-10 (IL-10), Interleukin-1ß (IL-1ß), Octamer-Binding Transcription Factor 1 (OCT1), B-cell lymphoma/leukemia 11A (BCL11A). Statistical analysis was performed (ANOVA and t test, p < 0.05). Significant modifications were identified compared with T-30 for PCV, glucose, triglycerides, cholesterol, lactate, urea, creatinine, Tbil, ALP, LDH, Na+, K-, Ca2+, SAA, TPs, SPE, IL-6, IL-4, Oct-1, and BCL11A. In conclusion, the first long-term training period was found to induce fundamental systemic changes in untrained Thoroughbreds.

High-intensity interval exercise lowers postprandial glucose concentrations more in obese adults than lean adults.

AIMS: To compare postprandial glucose responses to high-intensity interval exercise (HIE) between obese and lean individuals. METHODS: Thirty healthy young adult males (15 obese, 15 lean) ate a standardised meal, then performed HIE (4 × 30-s Wingate cycling/4-min rest) or a no-exercise control trial (CON). Blood glucose was measured preprandially and up to 150 min postprandially. RESULTS: Compared to CON, HIE reduced postprandial glucose concentrations at 120-150 min in obese (p < 0.001) and lean men (p < 0.05), with greater reductions in obese than lean subjects at 120 (-27.0% vs. -8.3%), 135 (-31.9% vs. -15.7%), and 150 min (-21.8% vs. -10.6%). The total glucose area under the curve (AUC) for the testing period was lower with HIE than CON among obese men (p < 0.05), but not lean men (p > 0.05). We found moderate correlations between body mass and postprandial glucose changes (r = 0.39-0.44, p < 0.05), and between glucose AUC and body mass and fat free mass (r = 0.39-0.48, p < 0.05). CONCLUSIONS: Our findings suggest that HIE may act as a time-efficient lifestyle intervention strategy for improving obesity-related diabetes risk factors, and might play a role in primary diabetes prevention for the healthy but sedentary population.

The impact of high-intensity interval training on the cTnT response to acute exercise in sedentary obese young women.

AIMS: This study characterized (a) the cardiac troponin T (cTnT) response to three forms of acute high-intensity interval exercise (HIE), and (b) the impact of 12 weeks of HIE training on the cTnT response to acute exercise in sedentary obese young women. METHODS: Thirty-six sedentary women were randomized to traditional HIE training (repeated 4-minute cycling at 90% V ˙ O2max interspersed with 3-minute rest, 200 kJ/session), work-equivalent sprint interval exercise (SIE) training (repeated 1-minute cycling at 120% V ˙ O2max interspersed with 1.5-minute rest) or repeated-sprint exercise (RSE) training (40 × 6-second all-out sprints interspersed with 9-second rest) group. cTnT was assessed using a high-sensitivity assay before and immediately, 3 and 4 hours after the 1st (PRE), 6th (EARLY), 20th (MID), and 44th (END) training session, respectively. RESULTS: cTnT was elevated (P < 0.05) after all forms of acute interval exercise at the PRE and EARLY assessment with cTnT response higher (P < 0.05) after HIE (307%) and SIE (318%) than RSE (142%) at the PRE assessment. All forms of acute interval exercise at MID and END had no effect on the cohort cTnT concentration post-exercise (all P > 0.05). CONCLUSION: For sedentary obese young women, both HIE and SIE, matched for total work, induced a similar elevation in cTnT after acute exercise with a smaller rise observed after RSE. By the 44th training session, almost no post-exercise cTnT elevation was observed in all three groups. Such information is relevant for clinicians as it could improve medical decisionmaking.

Continuous and intermittent heat acclimation and decay in team sport athletes.

The aim of this study was to compare the impact of continuous (CON) and intermittent (INT) heat acclimation protocols on repeat-sprint performance, and to also assess the degree of performance decay following acclimation. Using a pair-matched, between subjects design, 16 trained male team sport athletes were allocated to either INT (8 sessions over 15 days) or CON acclimation (8 sessions over 8 days) groups. Participants performed a heat tolerance test (HTT) involving 60-min of repeat-sprint cycling with a 10-min half time break (in 35.3 ± 0.7°C, 60.1 ± 4.0%; RH) two days pre- (pre-HTT) and post-acclimation (post-HTT1). Decay was investigated with two further HTT's completed over the next two weeks (post-HTT2 and post-HTT3). Results showed the post-HTT1 performance variables [mean power (pre-HTT; INT = 1002.07 ± 173.74, CON = 1057.10 ± 180.07 / post-HTT1; INT = 1097.11 ± 186.85, CON = 1163.77 ± 184.65 W), mean power (W.kg-1), total work (kJ) and work (J.kg-1)] were greater than pre-HHT (p < 0.001) after acclimation, with no differences between INT and CON. No differences in final core and mean skin temperatures or heart rate existed after INT or CON acclimation, however 30 min measures for thermal sensation, perceived thirst and ratings of perceived exertion (as well as the final measure) were lower in post-HTT1 (p < 0.05) in CON. Performance and thermoregulatory responses in post-HTT2 and 3 were similar to post-HTT1 in both INT and CON. These results indicate that prolonged repeat-sprint exercise in the heat is improved after acclimation involving short, high-intensity cycling sessions using either CON or INT protocols, with performance well-maintained over the subsequent 2 weeks, despite removal of the heat stimulus.

Mangifera indica L. Leaf Extract in Combination With Luteolin or Quercetin Enhances VO2peak and Peak Power Output, and Preserves Skeletal Muscle Function During Ischemia-Reperfusion in Humans.

It remains unknown whether polyphenols such as luteolin (Lut), mangiferin and quercetin (Q) have ergogenic effects during repeated all-out prolonged sprints. Here we tested the effect of Mangifera indica L. leaf extract (MLE) rich in mangiferin (Zynamite®) administered with either quercetin (Q) and tiger nut extract (TNE), or with luteolin (Lut) on sprint performance and recovery from ischemia-reperfusion. Thirty young volunteers were randomly assigned to three treatments 48 h before exercise. Treatment A: placebo (500 mg of maltodextrin/day); B: 140 mg of MLE (60% mangiferin) and 50 mg of Lut/day; and C: 140 mg of MLE, 600 mg of Q and 350 mg of TNE/day. After warm-up, subjects performed two 30 s Wingate tests and a 60 s all-out sprint interspaced by 4 min recovery periods. At the end of the 60 s sprint the circulation of both legs was instantaneously occluded for 20 s. Then, the circulation was re-opened and a 15 s sprint performed, followed by 10 s recovery with open circulation, and another 15 s final sprint. MLE supplements enhanced peak (Wpeak) and mean (Wmean) power output by 5.0-7.0% (P < 0.01). After ischemia, MLE+Q+TNE increased Wpeak by 19.4 and 10.2% compared with the placebo (P < 0.001) and MLE+Lut (P < 0.05), respectively. MLE+Q+TNE increased Wmean post-ischemia by 11.2 and 6.7% compared with the placebo (P < 0.001) and MLE+Lut (P = 0.012). Mean VO2 during the sprints was unchanged, suggesting increased efficiency or recruitment of the anaerobic capacity after MLE ingestion. In women, peak VO2 during the repeated sprints was 5.8% greater after the administration of MLE, coinciding with better brain oxygenation. MLE attenuated the metaboreflex hyperpneic response post-ischemia, may have improved O2 extraction by the Vastus Lateralis (MLE+Q+TNE vs. placebo, P = 0.056), and reduced pain during ischemia (P = 0.068). Blood lactate, acid-base balance, and plasma electrolytes responses were not altered by the supplements. In conclusion, a MLE extract rich in mangiferin combined with either quercetin and tiger nut extract or luteolin exerts a remarkable ergogenic effect, increasing muscle power in fatigued subjects and enhancing peak VO2 and brain oxygenation in women during prolonged sprinting. Importantly, the combination of MLE+Q+TNE improves skeletal muscle contractile function during ischemia/reperfusion.

Skeletal Muscle Pyruvate Dehydrogenase Phosphorylation and Lactate Accumulation During Sprint Exercise in Normoxia and Severe Acute Hypoxia: Effects of Antioxidants.

Compared to normoxia, during sprint exercise in severe acute hypoxia the glycolytic rate is increased leading to greater lactate accumulation, acidification, and oxidative stress. To determine the role played by pyruvate dehydrogenase (PDH) activation and reactive nitrogen and oxygen species (RNOS) in muscle lactate accumulation, nine volunteers performed a single 30-s sprint (Wingate test) on four occasions: two after the ingestion of placebo and another two following the intake of antioxidants, while breathing either hypoxic gas (PIO2 = 75 mmHg) or room air (PIO2 = 143 mmHg). Vastus lateralis muscle biopsies were obtained before, immediately after, 30 and 120 min post-sprint. Antioxidants reduced the glycolytic rate without altering performance or VO2. Immediately after the sprints, Ser293- and Ser300-PDH-E1α phosphorylations were reduced to similar levels in all conditions (~66 and 91%, respectively). However, 30 min into recovery Ser293-PDH-E1α phosphorylation reached pre-exercise values while Ser300-PDH-E1α was still reduced by 44%. Thirty minutes after the sprint Ser293-PDH-E1α phosphorylation was greater with antioxidants, resulting in 74% higher muscle lactate concentration. Changes in Ser293 and Ser300-PDH-E1α phosphorylation from pre to immediately after the sprints were linearly related after placebo (r = 0.74, P < 0.001; n = 18), but not after antioxidants ingestion (r = 0.35, P = 0.15). In summary, lactate accumulation during sprint exercise in severe acute hypoxia is not caused by a reduced activation of the PDH. The ingestion of antioxidants is associated with increased PDH re-phosphorylation and slower elimination of muscle lactate during the recovery period. Ser293 re-phosphorylates at a faster rate than Ser300-PDH-E1α during the recovery period, suggesting slightly different regulatory mechanisms.

Postexercise serum hepcidin response to repeated sprint exercise under normoxic and hypoxic conditions.

We determined the effects of repeated sprint exercise under normoxic and hypoxic conditions on serum hepcidin levels. Ten male athletes (age: 20.9 ± 0.3 years; height: 175.7 ± 6.0 cm; weight: 67.3 ± 6.3 kg) performed 2 exercise trials under normoxic (NOR; fraction of inspiratory oxygen (FiO2): 20.9%) or hypoxic conditions (HYPO; FiO2: 14.5%). The exercise consisted of 3 sets of 5 × 6 s of maximal pedaling (30-s rest periods between sprints, 10-min rest periods between sets). Blood samples were collected before exercise, immediately after exercise, and 1 and 3 h after exercise. Serum hepcidin levels were significantly elevated after exercise in both trials (both P < 0.01), with no significant difference between the trials. The postexercise blood lactate levels were significantly higher in the HYPO than the NOR (P < 0.05). Both trials caused similar increases in plasma interleukin-6 and serum iron levels (P < 0.001), with no significant difference between the trials. A significant interaction (trial × time) was apparent in terms of serum erythropoietin (EPO) levels (P = 0.003). The EPO level was significantly higher in the HYPO than the NOR at 3 h after exercise (P < 0.05). In conclusion, repeated sprint exercise significantly increased serum hepcidin levels to similar extent in 2 trials, despite differences in the inspired oxygen concentrations during both the exercise and the 3-h postexercise period.