Improve Time Trial Performance Research Articles

Blood Flow Restricted Training and Time Trial Performance: A Cohort Study of World Class Rowers.

This study aimed to explore the potential impact of incorporating blood-flow restriction (BFR) training within a training block characterized by minimal high-intensity work on 2000-m rowing ergometer time-trial (TT) performance in elite/world-class rowers. Physiological markers often associated with endurance performance (maximal aerobic capacity - VO2max, blood lactate thresholds and hemoglobin mass - Hbmass) were measured to determine whether changes are related to an improvement in performance. Using a quasi-experimental, observational study design (no control group), 2000-m TT performance, VO2max, submaximal work rates eliciting blood lactate concentrations of ~2 and ~ 4 mmol·L-1, and Hbmass were measured before and after 4 weeks of non-competitive season training, which included BFR rowing. BFR training consisted of 11 sessions of 2x10 minutes of BFR rowing at a workload equating to blood lactate concentrations of ~2 mmol·L-1. Paired t-tests were used to compare pre/post values, and Pearson correlation was used to examine whether physiological changes were associated with changes to TT performance. TT performance improved in both female (1.09 ± 1.2%, ~4.6 ± 5.2 s; p < 0.01) and male (1.17 ± 0.48%, ~4.5 ± 1.9 s; p < 0.001) athletes. VO2max increased in female rowers only (p < 0.01), but both sexes had an increase in work rates eliciting blood lactate concentrations of 2 (female:184 ± 16 to 195 ± 15 W, p < 0.01; male:288 ± 23 to 317 ± 26 W, p = 0.04) and 4 mmol·L-1 (female:217 ± 13 to 227 ± 14 W, p = 0.02; male:339 ± 43 to 364 ± 39 W, p < 0.01). No changes in Hbmass (both sexes, p = 0.8) were observed. Improvements in TT performance were not related to physiological changes (all correlations p ≥ 0.2). After 4 weeks of training with BFR, the improvement in TT performance was greater than what is typical for this population. Physiological variables improved during this training block but did not explain improved TT performance.

Rhodiola rosea as an adaptogen to enhance exercise performance: a review of the literature.

Rhodiola rosea (RR) is a plant whose bioactive components may function as adaptogens, thereby increasing resistance to stress and improving overall resilience. Some of these effects may influence exercise performance and adaptations. Based on studies of rodents, potential mechanisms for the ergogenic effects of RR include modulation of energy substrate stores and use, reductions in fatigue and muscle damage and altered antioxidant activity. At least sixteen investigations in humans have explored the potential ergogenicity of RR. These studies indicate acute RR supplementation (∼200 mg RR containing ∼1 % salidroside and ∼3 % rosavin, provided 60 min before exercise) may prolong time-to-exhaustion and improve time trial performance in recreationally active males and females, with limited documented benefits of chronic supplementation. Recent trials providing higher doses (∼1500 to 2400 mg RR/d for 4–30 d) have demonstrated ergogenic effects during sprints on bicycle ergometers and resistance training in trained and untrained adults. The effects of RR on muscle damage, inflammation, energy system modulation, antioxidant activity and perceived exertion are presently equivocal. Collectively, it appears that adequately dosed RR enhances dimensions of exercise performance and related outcomes for select tasks. However, the current literature does not unanimously show that RR is ergogenic. Variability in supplementation dose and duration, concentration of bioactive compounds, participant characteristics, exercise tests and statistical considerations may help explain these disparate findings. Future research should build on the longstanding use of RR and contemporary clinical trials to establish the conditions in which supplementation facilitates exercise performance and adaptations.

Effects of tapering on performance in endurance athletes: A systematic review and meta-analysis.

To assess the responses to taper in endurance athletes using meta-analysis. Systematic searches were conducted in China National Knowledge Infrastructure, PubMed, Web of Science, SPORTDiscus, and EMBASE databases. Standardized mean difference (SMD) and 95% confidence interval (CI) of outcome measures were calculated as effect sizes. 14 studies were included in this meta-analysis. Significant improvements were found between pre- and post-tapering in time-trial (TT) performance (SMD = -0.45; P < 0.05) and time to exhaustion (TTE) performance (SMD = 1.28; P < 0.05). However, There were no improvements in maximal oxygen consumption ([Formula: see text]) and economy of movement (EM) (P > 0.05) between pre- and post-tapering. Further subgroup analysis showed that tapering combined with pre-taper overload training had a more significant effect on TT performance than conventional tapering (P < 0.05). A tapering strategy that reduced training volume by 41-60%, maintained training intensity and frequency, lasted ≤7 days, 8-14 days, or 15-21 days, used a progressive or step taper could significantly improve TT performance (P < 0.05). The tapering applied in conjunction with pre-taper overload training seems to be more conducive to maximize performance gains. Current evidence suggests that a ≤21-day taper, in which training volume is progressively reduced by 41-60% without changing training intensity or frequency, is an effective tapering strategy.

The Effect of Isolated and Combined Application of Menthol and Carbohydrate Mouth Rinses on 40 km Time Trial Performance, Physiological and Perceptual Measures in the Heat.

The current study compared mouth swills containing carbohydrate (CHO), menthol (MEN) or a combination (BOTH) on 40 km cycling time trial (TT) performance in the heat (32 °C, 40% humidity, 1000 W radiant load) and investigates associated physiological (rectal temperature (Trec), heart rate (HR)) and subjective measures (thermal comfort (TC), thermal sensation (TS), thirst, oral cooling (OC) and RPE (legs and lungs)). Eight recreationally trained male cyclists (32 ± 9 y; height: 180.9 ± 7.0 cm; weight: 76.3 ± 10.4 kg) completed familiarisation and three experimental trials, swilling either MEN, CHO or BOTH at 10 km intervals (5, 15, 25, 35 km). The 40 km TT performance did not differ significantly between conditions (F2,14 = 0.343; p = 0.715; η2 = 0.047), yet post-hoc testing indicated small differences between MEN and CHO (d = 0.225) and MEN and BOTH (d = 0.275). Subjective measures (TC, TS, RPE) were significantly affected by distance but showed no significant differences between solutions. Within-subject analysis found significant interactions between solution and location upon OC intensity (F28,196 = 2.577; p < 0.001; η2 = 0.269). While solutions containing MEN resulted in a greater sensation of OC, solutions containing CHO experienced small improvements in TT performance. Stimulation of central CHO pathways during self-paced cycling TT in the heat may be of more importance to performance than perceptual cooling interventions. However, no detrimental effects are seen when interventions are combined.

Effects of Heat Acclimatization, Heat Acclimation, and Intermittent Exercise Heat Training on Time-Trial Performance.

The purpose of this study was to investigate effects of heat acclimatization (HAz) followed by heat acclimation (HA), and intermittent heat training (IHT) on time-trial performance. Time-trial performance will improve after HA and will further improve with twice a week of IHT. Interventional study. Level 3. A total of 26 male athletes (mean ± SD; age, 35 ± 12 years; body mass, 72.8 ± 8.9 kg; peak oxygen consumption [VO2peak], 57.3 ± 6.7 mL·kg-1·min-1) completed five 4-km time trials (baseline, post-HAz, post-HA, post-IHT4, post-IHT8) in the heat (ambient temperature, 35.4°C ± 0.3°C; relative humidity, 46.7% ± 1.2%) on a motorized treadmill. After baseline time trial, participants performed HAz (109 ± 10 days) followed by post-HAz time trial. Then, participants completed 5 days of HA, which involved exercising to induce hyperthermia (38.50°C-39.75°C) for 60 minutes. Participants were then divided into 3 groups and completed IHT either twice per week (IHTMAX), once per week (IHTMIN), or not at all (IHTCON) over an 8-week period. The exercise used for the IHT matched the HA. Four-kilometer time trials were performed after 4 weeks (post-IHT4) and 8 weeks of IHT (post-IHT8). Time trial was faster in post-HA (17.98 ± 2.51 minutes) compared with baseline (18.61 ± 3.06 minutes; P = 0.037) and post-HAz (18.66 ± 3.12 minutes; P = 0.023). Percentage change in time trial was faster in IHTMAX (-3.9% ± 5.2%) compared with IHTCON (11.5% ± 16.9%) (P = 0.020) and approached statistical significance with large effect (effect size = 0.96) compared with IHTMIN (1.6% ± 6.2%; P = 0.059) at post-IHT8. Additionally, IHTMAX (-2.2% ± 4.2%) was faster than IHTCON (3.6% ± 6.9%) (P = 0.05) at post-IHT4. These results indicate that HA after HAz induces additional improvement in time-trial performance. IHT twice per week shows improvement after 8 weeks, while once per week maintains performance for 8 weeks. No IHT results in a loss of adaptations after 4 weeks and even greater losses after 8 weeks. HA after HAz improves time-trial performance, twice a week of IHT improves performance further, and once a week of IHT maintains performance for at least 8 weeks.

Hydration Is More Important Than Exogenous Carbohydrate Intake During Push-to-the-Finish Cycle Exercise in the Heat.

Dehydration ≥2% loss of body mass is associated with reductions in performance capacity, and carbohydrate (CHO)-electrolyte solutions (CES) are often recommended to prevent dehydration and provide a source of exogenous carbohydrate during exercise. It is also well established that performance capacity in the heat is diminished compared to cooler conditions, a response attributable to greater cardiovascular strain caused by high skin and core temperatures. Because hydration status, environmental conditions, and carbohydrate availability interact to influence performance capacity, we sought to determine how these factors affect push-to-the-finish cycling performance. Ten young trained cyclists exercised at a moderate intensity (2.5 W·kg−1) in a hot-dry condition [40°C, 20% relative humidity (RH)] until dehydration of ~2% body mass. Subjects then consumed either no fluid (NF) or enough fluid (water, WAT; Gatorade®, GAT; or GoodSport™, GS) to replace 75% of lost body mass over 30 min. After a 30-min light-intensity warm-up (1.5 W·kg−1) in a 35°C, 20% RH environment, subjects then completed a 120-kJ time trial (TT). TT time-to-completion, absolute power, and relative power were significantly improved in WAT (535 ± 214 s, 259 ± 99 W, 3.3 ± 0.9 W·kg−1), GAT (539 ± 226 s, 260 ± 110 W, 3.3 ± 1.0 W·kg−1), and GS (534 ± 238 s, 262 ± 105 W, 3.4 ± 1.0 W·kg−1) compared to NF (631 ± 310 s, 229 ± 96 W, 3.0 ± 0.9 W·kg−1) all (p < 0.01) with no differences between WAT, GAT, and GS, suggesting that hydration is more important than carbohydrate availability during exercise in the heat. A subset of four subjects returned to the laboratory to repeat the WAT, GAT, and GS treatments to determine if between-beverage differences in time-trial performance were evident with a longer TT in thermoneutral conditions. Following dehydration, the ambient conditions in the environmental chamber were reduced to 21°C and 20% RH and subjects completed a 250-kJ TT. All four subjects improved TT performance in the GS trial (919 ± 353 s, 300 ± 100 W, 3.61 ± 0.86 W·kg−1) compared to WAT (960 ± 376 s, 283 ± 91 W, 3.43 ± 0.83 W·kg−1), while three subjects improved TT performance in the GAT trial (946 ± 365 s, 293 ± 103 W, 3.60 ± 0.97 W·kg−1) compared to WAT, highlighting the importance of carbohydrate availability in cooler conditions as the length of a push-to-the-finish cycling task increases.

The Comparative Effects Of Periodized Lower Body Strength Training Versus High Intensity Circuit Programming In Experienced Runners

While current research offers evidence-based strength training approaches to enhance endurance running performance, numerous popular strength training models have not been empirically tested in this context. PURPOSE: Compare the effects of periodized lower body strength training versus high intensity circuit strength training on running performance and related variables in experienced runners. METHODS: Participants (N = 19) were randomized to 8 weeks of periodized lower body strength training (PLB), n = 9, or high intensity circuit training (CT), n = 10. All participants strength trained 2 d·wk-1 and followed their typical running schedule. PLB sessions included 2 sets of the back squat, standing calf raise, leg press, and dumbbell lunge, with intensity linearly periodized. PLB initially completed sets at 10-repetition maximum (10-RM) and progressed each 2 weeks to 8-RM, 6-RM, and 4-RM. CT sessions included a high intensity, whole body resistance circuit followed by 2-4 heavy (>10-RM) sets of a compound lift, simulating CrossFit©-style programming. 3-km time trial (TT), VO2 max, relative leg press 1-RM, running economy (RE) at 2 standard submaximal velocities (SV1, SV2) between 11 and 14 km·hr-1, RPE at SV1/SV2, and peak/mean power during the Wingate Anaerobic Test were assessed pre and post-intervention. RESULTS: Two-way ANOVA showed a significant main effect of time on RE at 11 km·hr-1 (F = 8.31, p = .02, ηp2 = 0.51) and RPE at SV1 (F = 11.2, p = .004, ηp2 = .40), and a significant group*time interaction on 1-RM (F = 7.66, p = .015, ηp2 = .35) and RPE at SV2 (F = 5.30, p = .037, ηp2 = .28). Similar (p ≤ .02) increases occurred in RE at 11 km·hr-1 (36.4 ± 3.1 to 35.4 ± 2.4 ml·kg-1·min-1) and RPE at SV 1 (12.5 ± 1.3 to 11.4 ± 1.6). Relative 1-RM (2.54 ± 0.41 to 3.40 ± 0.72) and RPE at SV2 (14.1 ± 1.3 to 12.9 ± 1.8) improved in both groups (p ≤ .03). However, PLB showed larger improvements in 1-RM (0.43 ± 0.18 vs. 0.2 ± 1.9, t = 2.75, p = .015) and RPE at SV2 (-1.75 ± 0.9 vs. -0.63 ± 1.1, t = 2.30, p = .037). TT, VO2 max, RE at 12-14 km·hr-1, and power were unchanged (p ≥ .27). CONCLUSIONS: Both modalities enhanced lower body strength, RE at 11 km·hr-1 and submaximal RPE at submaximal, but neither improved TT performance, VO2 max, power, or RE at faster velocities. PLB resulted in greater improvements in lower body strength and RPE at higher submaximal running velocity.

Exogenous Ketone Salt Supplementation and Whole-Body Cooling Do Not Improve Short-Term Physical Performance.

Exogenous ketone supplementation and whole-body cooling (WBC) have shown to independently influence exercise metabolism. Whether readily available ketone salts, with and without WBC, would provide similar metabolic benefits during steady-state aerobic and time-trial performances was investigated. Nine active males (VO2peak: 56.3 ± 2.2 mL·kg−1·min−1) completed three single-blind exercise sessions preceded by: (1) ingestion of placebo (CON), (2) ketone supplementation (0.3 g·kg−1 β-OHB) (KET), and (3) ketone supplementation with WBC (KETCO). Participants cycled in steady-state (SS, 60% Wmax) condition for 30-min, immediately followed by a 15-min time trial (TT). Skin and core temperature, cardio-metabolic, and respiratory measures were collected continuously, whereas venous blood samples were collected before and after supplementation, after SS and TT. Venous β-OHB was elevated, while blood glucose was lower, with supplementation vs. CON (p < 0.05). TT power output was not different between conditions (p = 0.112, CON: 190 ± 43.5 W, KET: 185 ± 40.4 W, KETCO: 211 ± 50.7 W). RER was higher during KETCO (0.97 ± 0.09) compared to both CON (0.88 ± 0.04, p = 0.012) and KET (0.88 ± 0.05, p = 0.014). Ketone salt supplementation and WBC prior to short-term exercise sufficiently increase blood β-OHB concentrations, but do not benefit metabolic shifts in fuel utilization or improve time trial performance.

Effects of jump training on physical fitness and athletic performance in endurance runners: A meta-analysis

ABSTRACT This systematic review and meta-analysis aimed to assess the effects of jump training (JT) on measures of physical fitness and athletic performances in endurance runners. Controlled studies which involved healthy endurance runners, of any age and sex, were considered. A random-effects model was used to calculate effect sizes (ES; Hedge’s g). Means and standard deviations of outcomes were converted to ES with alongside 95% confidence intervals (95%CI). Twenty-one moderate-to-high quality studies were included in the meta-analysis, and these included 511 participants. The main analyses revealed a significant moderate improvement in time-trial performance (i.e. distances between 2.0 and 5.0 km; ES = 0.88), without enhancements in maximal oxygen consumption (VO2max), velocity at VO2max, velocity at submaximal lactate levels, heart rate at submaximal velocities, stride rate at submaximal velocities, stiffness, total body mass or maximal strength performance. However, significant small-to-moderate improvements were noted for jump performance, rate of force development, sprint performance, reactive strength, and running economy (ES = 0.36–0.73; p < 0.001 to 0.031; I2 = 0.0% to 49.3%). JT is effective in improving physical fitness and athletic performance in endurance runners. Improvements in time-trial performance after JT may be mediated through improvements in force generating capabilities and running economy.

Programming Interval Training to Optimize Time-Trial Performance: A Systematic Review and Meta-Analysis.

Interval training has become an essential component of endurance training programs because it can facilitate a substantial improvement in endurance sport performance. Two forms of interval training that are commonly used to improve endurance sport performance are high-intensity interval training (HIIT) and sprint interval training (SIT). Despite extensive research, there is no consensus concerning the optimal method to manipulate the interval training programming variables to maximize endurance performance for differing individuals. The objective of this manuscript was to perform a systematic review and meta-analysis of interval training studies to determine the influence that individual characteristics and training variables have on time-trial (TT) performance. SPORTDiscus and Medline with Full Text were explored to conduct a systematic literature search. The following criteria were used to select studies appropriate for the review: 1. the studies were prospective in nature; 2. included individuals between the ages of 18 and 65years; 3. included an interval training (HIIT or SIT) program at least 2weeks in duration; 4. included a TT test that required participants to complete a set distance; 5. and programmed HIIT by power or velocity. Twenty-nine studies met the inclusion criteria for the quantitative analysis with a total of 67 separate groups. The participants included males (n = 400) and females (n = 91) with a mean group age of 25 (range 19-45) years and mean [Formula: see text] of 52 (range 32-70) mL·kg-1·min-1. The training status of the participants comprised ofinactive (n = 75), active (n = 146) and trained (n = 258) individuals. Training status played a significant role in improvements in TT performance with trained individuals only seeing improvements of approximately 2% whereas individuals of lower training status demonstrated improvements as high as 6%. The change in TT performance with HIIT depended on the duration but not the intensity of the interval work-bout. There was a dose-response relationship with the number of HIIT sessions, training weeks and total work with changes in TT performance. However, the dose-response was not present with SIT. Optimization of interval training programs to produce TT performance improvements should be done according to training status. Our analysis suggests that increasing interval training dose beyond minimal requirements may not augment the training response. In addition, optimal dosing differs between high intensity and sprint interval programs.

Three km Track Time Trial Performance Changes after HIIT in Competitive Cross-Country Skiers

Background: Limited research surrounding sex differences in fatigue and performance after high intensity interval training (HIIT) exists in the field setting. While lab-based protocols provide a controlled environment, physiological mechanisms of fatigue and performance response in competitive athletes are best measured by time-trial (TT). Few studies, however, have investigated fatigue in TT performance while controlling for the menstrual cycle (MC). Objective: The study investigated the influence of sex and MC phase on 3km track TT performance after a HIIT session in Competitive Cross Country (XC) skiers. Methods: A quasi-experimental design was employed and athletes over the age of 16 years (30F, 9M), were recruited from across Canada and completed 3 days of testing/training: a 3km track TT on Day 1 and Day 3; and a HIIT session (4-8x, 800m) on Day 2. MC phase was verified by ovulation testing and salivary hormone samples; athletes were classified as either “Low Hormone” or “High Hormone” for analysis. Results: An overall improvement in performance from pre- to post-HIIT TTs occurred (p&lt;0.01). No significant differences in TT performance after HIIT were observed between sexes (p=0.16) or MC phase (p=0.26). Conclusion: These results indicate that competitive XC skiers will likely experience an improvement in TT performance after a bout of HIIT. Coaches and athletes should plan their workouts prior to testing accordingly to maximize TT performance. These results also suggest that no special adjustments need to be considered for differences in performance after HIIT between sexes and MC phase, although further studies with a greater sample size and repeated testing are warranted.

Protein supplementation increases adaptations to endurance training: A systematic review and meta-analysis

Trials that assessed the impact of protein supplementation on endurance training adaptations have reported conflicting findings. To determine the impact of protein supplementation during chronic endurance training on aerobic capacity, body composition and exercise performance in healthy and clinical populations. A systematic database search was conducted for randomised controlled trials addressing the effects of protein supplementation during endurance training on aerobic capacity, body composition and exercise performance in PubMed, Embase, Web of Science, and CINAHL. Meta-analyses were performed to outline the overall effects of protein supplementation with all studies containing endurance training components. The effects of endurance training and add-on effects of protein supplementation were evaluated by the meta-analyses with endurance training-focused studies. Nineteen studies and 1162 participants contributed to the analyses. Compared with the control group, the protein supplementation group demonstrated greater improvements in aerobic capacity measured by mixed peak oxygen uptake (V̇O2peak) and peak workload power (Wpeak) (standardised mean difference [SMD]=0.36, 95% confidence interval [CI]: 0.05 to 0.67), and V̇O2peak (mean difference [MD]=0.89mL‧kg-1‧min-1, 95% CI: 0.07 to 1.70); had a greater lean mass gain (MD=0.32kg, 95% CI: 0.07 to 0.58); and had a greater improvement in time trial performance (MD=-29.1s, 95% CI:-55.3 to-3.0). Secondary analyses showed that, in addition to the substantial improvement in V̇O2peak (MD=3.67mL‧kg-1‧min-1, 95% CI: 2.32 to 5.03) attributed to endurance training, protein supplementation provided an additional 26.4% gain in V̇O2peak (MD=0.97mL‧kg-1‧min-1, 95% CI:-0.03 to1.97). Protein supplementation further increased aerobic capacity, stimulated lean mass gain, and improved time trial performance during chronic endurance training in healthy and clinical populations. PROSPERO REGISTRATION NUMBER: (CRD42020155239).

Ketone bodies as an energy source: regular-grade, premium, or super-fuel to power the mitochondrial engine?

Ketone bodies as an energy source: regular-grade, premium, or super-fuel to power the mitochondrial engine?

Sprint Interval Training and Endurance Exercise Performance: Influence of Constant vs Variable Time of Day of Training and Time of Assessment

In light of the many demands competing for our attention in today’s modern lifestyle, scheduling healthy behaviors, such as daily exercise, at or around the same time of day can be difficult. Accordingly, the purpose of this study was to compare the endurance benefits of short‐term sprint interval training (SIT) when SIT was completed at a constant or variable time of day. The influence of the time of day of assessment relative to the time of day of training was also examined. SIT consisted of six sessions of 4‐to‐7 x 30‐second sprints on a stationary cycle ergometer completed over two weeks. Endurance exercise performance was assessed via a laboratory‐based cycle ergometer time trial equivalent to 10‐km. Two habituation time trials were completed prior to pre‐SIT assessment. Twenty healthy adults (age: 23 ± 7 years, body mass index: 24.7 ± 3.0 kg/m2, maximal oxygen uptake: 44 ± 9 ml/kg/min (mean ± SD)) were randomly assigned to one of two training conditions: (1) Constant (6 males, 3 females), in which all training and pre/post time‐trials occurred at a fixed time of day that was not necessarily the same time for each participant; or, (2) Variable (7 males, 4 females), in which all training was scheduled such that each session never occurred within 6‐hours of the time of day of the previous session; post‐SIT time trials for the Variable group were completed at the same time of day as pre‐SIT time trials. A second post‐SIT time trial (Post2) was scheduled for all participants to occur at a time of day a minimum of 6‐hours earlier/later than the time of day of the first post‐SIT time trial. SIT improved time trial performance (main effect P=0.019) but only when the time trial did not occur at the same time of day as training (i.e. Post2); the magnitude of improvement was not influenced by whether the training was completed at a constant or variable time of day (Constant: Pre 1153 ± 173, Post 1136 ± 179, &amp; Post2 1123 ± 154 s vs. Variable: Pre 1186 ± 159, Post 1166 ± 158, &amp; Post2 1149 ± 130 s; group x training interaction P=0.646). SIT did not influence body mass or composition, as determined by dual energy X‐ray absorptiometry (all P&gt;0.34). At the start of each SIT session, oral temperature was measured. The co‐efficient of variation appeared lower for the Constant compared with the Variable group (0.6 ± 0.3 vs. 1.1 ± 0.7%; P=0.099). Our preliminary data suggest that SIT improves endurance exercise performance when assessed at a variable time of day, irrespective of whether training is scheduled at a constant or variable time of day. From a public health perspective, scheduling regular exercise at or around the same time of day does not appear to be important for obtaining endurance benefits.

5-Hydroxymethylfurfural and α-ketoglutaric acid supplementation increases oxygen saturation during prolonged exercise in normobaric hypoxia

This double-blinded, randomized and placebo-controlled, crossover study investigated whether α-ketoglutaric-acid (α-KG) and 5-hydroxymethylfurfural (5-HMF) supplementation improves exercise performance in hypoxia and affects physiological responses during the exercise task. Eight moderately trained male participants (age: 25.3±2.0 y, VO2max: 48.0±8.3ml/min/kg) performed an incremental exercise test to exhaustion in normoxia and two 2-hour cycle time trial (TT) tests in hypoxia (3,500m) each separated by 1-week. Prior to the TT, participants supplemented with either α-KG and 5-HMF or placebo (random order). Supplementation did not improve TT performance at altitude and did not affect heart rate, effort perception and oxidative stress levels (p>0.05). Oxygen saturation (SpO2) was enhanced during the α-KG and 5-HMF supplementation trial (79.5±3.3 vs. 78.2±3.7%, p=0.026). Even though TT performance was unaffected, the enhanced SpO2 - possibly originated from changed O2-affinity - deserves further consideration as the exercise performance decline at altitude is strongly linked to the SpO2 decline. The inclusion of moderately fit participants, not specifically cycle trained, might have prevented any visible performance enhancement.

Response.

Dear Editor-in-Chief, Heuberger and Cohen (1) address a potential concern regarding our recent conclusion that autologous blood transfusion (ABT) of approximately 135-mL packed red blood cells improves cycling time trial performance (2). The concern is related to our reported finding that total hemoglobin mass (tHb) was approximately 35 g lower in the ABT than placebo trial before transfusion. This result most likely reflects that our participants had not fully recovered from the phlebotomy performed 4 wk earlier. The question is whether this fact impacts our conclusion. We conclude that ABT of approximately 135 mL of packed red cells improves time-trial performance and this result cannot be questioned. However, it may be questioned whether the effect of ABT on performance is dependent on an initial difference in hemoglobin mass of 35 g. Although we cannot rule this out, it seems highly unlikely. Indeed, data from less-controlled studies of both moderately (3) and highly trained (4) subjects, where the initial hemoglobin mass must be expected to differ markedly (5), indicate that 900 to 1350 mL ABT improves performance. Thus, we argue that the valid concern related to initial tHb appears to be of little importance. Furthermore, Heuberger and Cohen postulate that time trial performance differs between ABT and placebo at the pretransfusion time point and argue that this may affect the conclusion. However, as described in our article, no significant difference in performance was apparent before transfusion. The significant time–treatment interaction only demonstrates that the effect of time may depend on the level of treatment. The subsequent post hoc analysis revealed that mean power output only increased significantly over time in ABT. Thus, the conclusion that approximately 135 mL ABT improves time trial performance compared with placebo is valid. Our recent study (2) was the first to investigate whether ABT of only approximately 135 mL packed red blood cells improves time trial performance in a relatively small number of participants. Thus, it is evident that the findings need to be validated, and we encourage further studies in the area. However, the conclusions drawn in our studies rest on solid scientific principles and are unlikely to be confounded by the difference in initial tHb. Jacob Bejder Andreas Breenfeldt Andersen Sara Amalie Solheim Nikolai B. Nordsborg Department of Nutrition, Exercise and Sports University of Copenhagen Copenhagen, DENMARK

Whey Protein Isolate Supplementation While Endurance Training Does Not Alter Cycling Performance or Immune Responses at Rest or After Exercise.

This study examined whey protein isolate supplementation combined with endurance training on cycling performance, aerobic fitness and immune cell responses. Eighteen male cyclists were randomly assigned to either placebo (PLA) or whey protein supplementation (WS; 1.0 g·kg body mass−1·d−1 in addition to their dietary intake). Both groups completed the identical endurance training program, 4 days per week for 6 weeks. Blood samples were obtained at rest and after 5 and 60 min of recovery from a simulated 40 km cycling time trial (TT) and were repeated after training. Baseline dietary intake of protein prior to supplementation was 1.52 ± 0.45 and 1.46 ± 0.44 g·kg body mass−1·d−1 for the WS and PLA groups, respectively. There were similar improvements in TT performance (WS: 71.47 ± 12.17 to 64.38 ± 8.09 min; PLA: 72.33 ± 12.79 to 61.13 ± 8.97 min), and peak oxygen uptake (WS: 52.3 ± 6.1 to 56.1 ± 5.4 mL·kg−1·min−1; PLA: 50.0 ± 7.1 to 54.9 ± 5.1 mL·kg−1·min−1) after training in both groups. White blood cells (WBC) and neutrophil counts were elevated 5 min after the TT and further increased after 60 min (P < 0.05). The exercise-induced increase in WBC and neutrophil counts at 5 and 60 min after the TT were attenuated after training compared to before training (P < 0.05). Lymphocytes increased 5 min after the TT and decreased below rest after 60 min of recovery (P < 0.05). Following training lymphocytes were lower after 60 min of recovery compared to before training. There was no change in natural killer cell activity with exercise, training or between groups. It was concluded that whey protein isolate supplementation while endurance training did not differentially change cycling performance or the immune response at rest or after exercise. However, endurance training did alter performance, aerobic fitness and some post exercise immune cell counts.

Chronic high-dose beetroot juice supplementation improves time trial performance of well-trained cyclists in normoxia and hypoxia

Dietary nitrate (NO3−) supplementation via beetroot juice (BR) is known to improve endurance performance in untrained and moderately trained individuals. However, conflicting results exist in well-trained individuals. Evidence suggests that the effects of NO3− are augmented during conditions of reduced oxygen availability (e.g., hypoxia), thereby increasing the probability of performance improvements for well-trained athletes in hypoxia vs. normoxia. This randomized, double-blinded, counterbalanced-crossover study examined the effects of 7 days of BR supplementation with 12.4 mmol NO3− per day on 10-km cycling time trial (TT) performance in 12 well-trained cyclists in normoxia (N) and normobaric hypoxia (H). Linear mixed models for repeated measures revealed increases in plasma NO3− and NO2− after supplementation with BR (both p < 0.001). Further, TT performance increased with BR supplementation (∼1.6%, p < 0.05), with no difference between normoxia and hypoxia (p = 0.92). For respiratory variables there were significant effects of supplementation on VO2 (p < 0.05) and VE (p < 0.05) such that average VO2 and VE during the TT increased with BR, with no difference between normoxia and hypoxia (p ≥ 0.86). We found no effect of supplementation on heart rate, oxygen saturation or muscle oxygenation during the TT. Our results provide new evidence that chronic high-dose NO3− supplementation improves cycling performance of well-trained cyclists in both normoxia and hypoxia.

Identification of the threshold ambient temperature above which pre-cooling has a performance benefit for time trials in the heat

Introduction. Endurance exercise performance progressively deteriorates as the surrounding ambient temperature increases, 1 which is exacerbated when combined with increasing humidity 2 and solar radiation. 3 It is clear that there is a strong link between increases in thermoregulatory strain, due to elevations in both metabolic and ambient heat, and impaired endurance performance. 4 It has become commonplace to implement pre-cooling prior to competition to alleviate this performance decline, with ~50% of athletes having a defined strategy prior to competing in the heat. 5 Such strategies include the use of ice-vests, which have been suggested to improve time trial performance in the heat by approximately 5%. 6 However, little is known about the ambient temperature threshold above which pre-cooling becomes an effective strategy for enhancing endurance performance. With most studies focusing on a single ambient temperature, typically above 30EsC or a Wet Globe Bulb Temperature (WGBT) of 26EsC. 7 Therefore, it was the aim of this study to investigate the effect of pre-cooling in different environmental temperatures on time trial performance. It was hypothesized that pre-cooling would improve time trial performance in all environmental temperatures, with the magnitude of effect dependent on environmental temperature. Methods. In an independent groups design, 24 trained male cyclists (age 24.3 ± 5.1 years; VO 2max 61.3 ± 3.7 mL . kg . min -` ; training frequency ≥3 times per week) completed two time trials with (COLD) and without (CON) of pre-cooling using an ice-vest and sleeves ensemble. Pre-cooling was implemented for 30 minutes at rest and during a 9 minute progressive warm up, in ambient temperatures of 24.0 ± 0.1°C & 49.5 ± 1.4% rh (WBGT 19.2°C); 27.2 ± 0.3°C & 50.7 ± 5.3% rh (WBGT 22.1°C); or 35.0 ± 0.4°C & 50.6% ± 1.3% rh (29.2°C). Participants removed the cooling vest (if warn) on completion of the warm up, prior to completing a self-paced time trial designed to last ~60 minutes when ridden at ~75% W max . Results. Time trial performance was 6.2% and 2.6% faster following COLD in both 35EsC and 27EsC (figure 1A) but not 24EsC (1.2%). Magnitude based inferential statistics indicate that COLD was very likely beneficial to performance in 35EsC and likely beneficial in 27EsC and possibly beneficial in 24°C. Mean power was 2.4% 2.5% and 5.6% higher following COLD (figure 1B,C) and considered to be likely beneficial in 24°C and very likely beneficial in 27EsC and 35EsC. There was no effect of COLD on gastrointestinal temperature at any point. Conclusions. Pre-cooling with an ice-vest and sleeves is likely to have a positive effect on time trial performance at temperatures above 24EsC, with a clear relationship between ambient temperature and the magnitude of effect of pre-cooling. These results indicate that cyclists should start to consider implementing a pre-cooling procedure prior to racing a time-trial in environmental temperatures of 24EsC and above. Importantly, utilising pre-cooling in lower ambient temperatures is unlikely to have a detrimental effect on performance at the cooling intensities used here. To the authors’ knowledge, this is the first time that a lower ambient temperature threshold has been identified above which pre-cooling has a significant ergogenic impact on performance.

Acute Caffeinated Coffee Consumption Does not Improve Time Trial Performance in an 800-m Run: A Randomized, Double-Blind, Crossover, Placebo-Controlled Study.

Introduction: Studies evaluating caffeinated coffee (CAF) can reveal ergogenic effects; however, studies on the effects of caffeinated coffee on running are scarce and controversial. Aim: To investigate the effects of CAF consumption compared to decaffeinated coffee (DEC) consumption on time trial performances in an 800-m run in overnight-fasting runners. Methods: A randomly counterbalanced, double-blind, crossover, placebo-controlled study was conducted with 12 healthy adult males with experience in amateur endurance running. Participants conducted two trials on two different occasions, one day with either CAF or DEC, with a one-week washout. After arriving at the data collection site, participants consumed the soluble CAF (5.5 mg/kg of caffeine) or DEC and after 60 min the run was started. Before and after the 800-m race, blood pressure and lactate and glucose concentrations were measured. At the end of the run, the ratings of perceived exertion (RPE) scale was applied. Results: The runners were light consumers of habitual caffeine, with an average ingestion of 91.3 mg (range 6–420 mg/day). Time trial performances did not change between trials (DEF: 2.38 + 0.10 vs. CAF: 2.39 + 0.09 min, p = 0.336), nor did the RPE (DEC: 16.5 + 2.68 vs. CAF: 17.0 + 2.66, p = 0.326). No difference between the trials was observed for glucose and lactate concentrations, or for systolic and diastolic blood pressure levels. Conclusion: CAF consumption failed to enhance the time trial performance of an 800-m run in overnight-fasting runners, when compared with DEC ingestion. In addition, no change was found in RPE, blood pressure levels, or blood glucose and lactate concentrations between the two trials.