Running Time Trial Research Articles

Effects of 16weeks of pyramidal and polarized training intensity distributions in well-trained endurance runners.

The aim of this study was to investigate the effects of four different training periodizations, based on two different training intensity distributions during a 16‐week training block in well‐trained endurance runners. Sixty well‐trained male runners were divided into four groups. Each runner completed one of the following 16‐week training interventions: a pyramidal periodization (PYR); a polarized periodization (POL); a pyramidal periodization followed by a polarized periodization (PYR → POL); and a polarized periodization followed by a pyramidal periodization (POL → PYR). The PYR and POL groups trained with a pyramidal or polarized distribution for 16 weeks. To allow for the change in periodization for the PYR → POL and POL → PYR groups, the 16‐week intervention was split into two 8‐week phases, starting with pyramidal or polarized distribution and then switching to the other. The periodization patterns were isolated manipulations of training intensity distribution, while training load was kept constant. Participants were tested pre‐, mid‐ and post‐intervention for body mass, velocity at 2 and 4 mmol·L−1 of blood lactate concentration (vBLa2, vBLa4), absolute and relative peak oxygen consumption (V˙O2peak) and 5‐km running time trial performance. There were significant group × time interactions for relative V˙O2peak (p < 0.0001), vBLa2 (p < 0.0001) and vBLa4 (p < 0.0001) and 5‐km running time trial performance (p = 0.0001). Specifically, participants in the PYR → POL group showed the largest improvement in all these variables (~3.0% for relative V˙O2peak, ~1.7% for vBLa2, ~1.5% for vBLa4, ~1.5% for 5‐km running time trial performance). No significant interactions were observed for body mass, absolute V˙O2peak, peak heart rate, lactate peak and rating of perceived exertion. Each intervention effectively improved endurance surrogates and performance in well‐trained endurance runners. However, the change from pyramidal to polarized distribution maximized performance improvements, with relative V˙O2peak representing the only physiological correlate.

Effects of Acacia Honey Drink after Exercise-Induced Dehydration on Selected Physiological Parameters and Subsequent Running Performance

This study examined the effect of honey supplementation on exercise performance and biochemical markers in comparison to plain water and sports drink in the heat. Ten recreational athletes (Age: 22.2 ± 2.0 years, weight: 65.7 ± 5.3 kg; height: 170.4 ± 3.5 cm; VO2max: 51.5 ± 3.7 mL.kg−1.min−1) participated in this study. Participants ran at 70% of their VO2max for 1 h in a pre-load phase (Run-1), followed by a rehydration phase for 2 h and then a 20 min self-paced time trial (Run-2). After Run-1, participants drank either Acacia honey, sports drink or plain water with an amount equivalent to 150% of body weight loss. Subsequently, the participants performed the 20 min self-paced time trial. Acacia honey elicited an improved running time trial performance with a significantly (p&lt;0.05) longer distance ran compared to plain water trial, but it was not different from the sports drink trial. In addition, there was no significant difference in running performance between sports drink and plain water trials. Plasma glucose, insulin and free fatty acids were significantly (p&lt;0.05) higher in H and sports drink compared to the W trial during the rehydration phase. There were no significant differences in body weight changes, oxygen uptake, heart rate, rate of perceived exertion, tympanic temperature, plasma volume changes, plasma cortisol, urine osmolality, volume, and specific gravity among the three trials. Thus, Acacia honey can be recommended to be used as a rehydration drink for individuals who train and compete in the heat.

Laboratory- and field-based performance-predictions in cross-country skiing and roller-skiing.

The purpose of the present study was to investigate how various laboratory- and field-based tests predict on-snow cross-country (XC) skiing and roller-skiing performance. Thirty-three national-level male XC skiers (19.0±2.5 years, maximal oxygen uptake [VO2max] 70.8±4.7 mL·min-1·kg-1) performed a 13.6-km roller-ski skating competition tracked by a global positioning system (GPS), which together with individual distance International Ski Federation (FIS) points was used to assess their performance level. On separate days, time in a 6.4-km uphill running time-trial (RUN-TT) and 1.3-km uphill roller-ski double-poling time-trial (DP-TT) was measured in the field and performance indices determined while running and roller-ski skating in the laboratory. The mean finishing times for the RUN-TT and the DP-TT showed moderate to large correlations with distance FIS points and performance in the roller-ski skating competition (r = 0.56–0.72; all p<0.05). RUN-TT was more strongly correlated with distance FIS points than DP-TT (r = 0.72 versus 0.56; p<0.05). Performance indices and VO2max in incremental running and roller-ski skating in the laboratory showed large to very large correlations with distance FIS points and roller-skiing performance (r = 0.50–0.90; all p<0.05). Performance indices and VO2max in running tended to be more strongly correlated with roller-skiing performance than corresponding values obtained while roller-ski skating (all p<0.10). The present findings suggest that both laboratory performance indices and field-based performance tests provide valid predictions of XC skiing and roller-skiing performance in a heterogeneous group of male XC skiers, with test values obtained in running tending to be more strongly correlated with XC skiing performance than those found for technique-specific modalities on roller skis. However, more sophisticated and mode-specific testing might be required for more homogenous groups of elite XC skiers.

Determinants of Performance in Paced and Maximal 800-m Running Time Trials.

We aimed to identify the underpinning physiological and speed/mechanical determinants of different types of 800-m running time trials (i.e., with a positive or negative pacing strategy) and key components within each 800-m time trial (i.e., first and final 200 m). Twenty trained male 800-m runners (800-m personal best time (min:s): 1:55.10 ± 0:04.44) completed a maximal 800-m time trial (800MAX) and one pacing trial, whereby runners were paced for the first lap, and speed was reduced by 7.5% (800PACE) relative to 800MAX, whereas the last lap was completed in the fastest time possible. Anaerobic speed reserve, running economy, the velocity corresponding with V˙O2peak (VV˙O2peak), maximal sprint speed (MAXSS), maximal accumulated oxygen deficit, and sprint force-velocity-power profiles were derived from laboratory and field testing. Carnosine content was quantified by proton magnetic resonance spectroscopy in the gastrocnemius and soleus and expressed as a carnosine aggregate Z (CAZ) score to estimate muscle typology. Data were analyzed using multiple stepwise regression analysis. MAXSS and vV˙O2peak largely explained the variation in 800MAX time (r2 = 0.570; P = 0.020), whereas MAXSS was the best explanatory variable for the first 200-m time in 800MAX (adjusted r2 = 0.661, P < 0.001). Runners with a higher CAZ score (i.e., higher estimated percentage of type II fibers) reduced their last lap time to a greater extent in 800PACE relative to 800MAX (adjusted r2 = 0.413, P < 0.001), whereas better maintenance of mechanical effectiveness during sprinting, a higher CAZ score and vV˙O2peak was associated with a faster final 200-m time during 800PACE (adjusted r2 = 0.761, P = 0.001). These findings highlight that diversity in the physiological and speed/mechanical characteristics of male middle-distance runners may be associated with their suitability for different 800-m racing strategies to have the best chance of winning.

Effects of a Short-Term "Fat Adaptation with Carbohydrate Restoration" Diet on Metabolic Responses and Exercise Performance in Well-Trained Runners.

Periodized carbohydrate availability can enhance exercise capacity, but the effects of short-term fat adaptation carbohydrate restoration (FACR) diets on metabolic responses and exercise performance in endurance athletes have not been conclusively determined. This study aimed to investigate the effect of a FACR diet on measures of resting metabolism, exercise metabolism, and exercise performance. Well-trained male runners (n = 8) completed a FACR dietary intervention (five days’ carbohydrate < 20% and fat > 60% energy, plus one-day carbohydrate ≥ 70% energy), and a control high-carbohydrate (HCHO) diet for six days (carbohydrate > 60% energy; fat < 20% energy) in a randomized crossover design. Pre- and post-intervention metabolic measures included resting metabolic rate (RMR), respiratory quotient (RQ), maximum fat oxidation rate during exercise (MFO), and maximum fat oxidation intensity (FATmax). Measures of exercise performance included maximal oxygen uptake (VO2max), running economy (RE), and 5 km running time trial (5 km-TT). In FACR compared with HCHO, there were significant improvements in FATmax (p = 0.006) and RE (p = 0.048). There were no significant differences (p > 0.05) between FACR and HCHO in RMR, RQ, VO2max, or 5 km-TT. Findings suggest that a short-term (six days) FACR diet may facilitate increased fat oxidation and submaximal exercise economy but does not improve 5 km-TT performance.

Relationships between physiological characteristics and match demands in elite-level male field hockey players

This study investigated the physical characteristics, match demands and their relationships in elite-level male field hockey players (n = 23; 24 ± 3 years). Testing data were collected to investigate the physiological profiles of the players, while match demands were quantified with GPS data over 26 matches. There were significant differences (p = &lt;0.05) between positional groups for pull ups, relative and absolute lower body strength, and body composition. Average total match distance for all the players was (5420 ± 1518 m). There were significant differences between positional groups for defenders (5770 ± 1419 m) vs strikers (4739 ± 1409 m) and midfielders (5549 ± 1545 m) vs strikers. The most high-speed-running (&gt;4.5 ms−1) distance was covered by midfielders (950 ± 275 m) and strikers (908 ± 284 m). Midfielders (116 ± 15 m min) and strikers (120 ± 20 m min) achieved higher intensities during matches compared to defenders (105 ± 13 m min). There were small differences between positional groups for physiological variables, but large variation between positional groups for match demands. There was a significant negative relationship between 2.4 km time trial vs high-speed running (p = &lt;0.05), player load.min and match speed (p = &lt;0.001). Also, there was a negative association between repeat sprint ability total time and high-speed running distance (p = &lt;0.02) and match speed (p = &lt;0.02). The countermovement jump height was associated with match speed (p = &lt;0.05) and there was a negative relationship between body fat % and match speed (p = &lt;0.02). When considering key performance indicators while using GPS devices, match speed (m.min) provides the most valuable information in field hockey players.

Association of Genetic Variances in ADRB1 and PPARGC1a with Two-Kilometre Running Time-Trial Performance in Australian Football League Players: A Preliminary Study.

Genetic variants in the angiotensin-converting enzyme (ACE) (rs4343), alpha-actinin-3 (ACTN3) (rs1815739), adrenoceptor-beta-1 (ADRB1) (rs1801253), and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1A) (rs8192678) genes have previously been associated with elite athletic performance. This study assessed the influence of polymorphisms in these candidate genes towards endurance test performance in 46 players from a single Australian Football League (AFL) team. Each player provided saliva buccal swab samples for DNA analysis and genotyping and were required to perform two independent two-kilometre running time-trials, six weeks apart. Linear mixed models were created to account for repeated measures over time and to determine whether player genotypes are associated with overall performance in the two-kilometre time-trial. The results showed that the ADRB1 Arg389Gly CC (p = 0.034) and PPARGC1A Gly482Ser GG (p = 0.031) genotypes were significantly associated with a faster two-kilometre time-trial. This is the first study to link genetic polymorphism to an assessment of endurance performance in Australian Football and provides justification for further exploratory or confirmatory studies.

Estimating Functional Threshold Power in Endurance Running from Shorter Time Trials Using a 6-Axis Inertial Measurement Sensor

Wearable technology has allowed for the real-time assessment of mechanical work employed in several sporting activities. Through novel power metrics, Functional Threshold Power have shown a reliable indicator of training intensities. This study aims to determine the relationship between mean power output (MPO) values obtained during three submaximal running time trials (i.e., 10 min, 20 min, and 30 min) and the functional threshold power (FTP). Twenty-two recreationally trained male endurance runners completed four submaximal running time trials of 10, 20, 30, and 60 min, trying to cover the longest possible distance on a motorized treadmill. Absolute MPO (W), normalized MPO (W/kg) and standard deviation (SD) were calculated for each time trial with a power meter device attached to the shoelaces. All simplified FTP trials analyzed (i.e., FTP10, FTP20, and FTP30) showed a significant association with the calculated FTP (p < 0.001) for both MPO and normalized MPO, whereas stronger correlations were found with longer time trials. Individual correction factors (ICF% = FTP60/FTPn) of ~90% for FTP10, ~94% for FTP20, and ~96% for FTP30 were obtained. The present study procures important practical applications for coaches and athletes as it provides a more accurate estimation of FTP in endurance running through less fatiguing, reproducible tests.

Footwear designed to enhance energy return improves running economy compared to a minimalist footwear: does it matter for running performance?

The present study compared the effects of a footwear designed to enhance energy return (thermoplastic polyurethane, TPU) vs minimalist shoes on running economy (RE) and endurance performance. In this counterbalanced and crossover design study, 11 recreational male runners performed two submaximal constant-speed running tests and two 3-km time-trials with the two shoe models. Oxygen uptake was measured during submaximal constant-speed running tests in order to determine the RE at 12 km/h and oxygen cost of running (CTO2) at individual average speed sustained during the 3-km running time-trials wearing either of the two shoes. Our results revealed that RE was improved (2.4%) with TPU shoes compared with minimalist shoes (P=0.01). However, there was no significant difference for CTO2 (P=0.61) and running performance (P=0.52) comparing the TPU (710±60 s) and the minimalist (718±63 s) shoe models. These novel findings demonstrate that shoes with enhanced mechanical energy return (i.e. TPU) produced a lower energy cost of running at low (i.e., 12 km/h) but not at high speeds (i.e., average speed sustained during the 3-km running time-trial, ∼15 km/h), ultimately resulting in similar running performance compared to the minimalist shoe.

Effects of Unilateral Versus Bilateral Plyometric Training on Endurance Running Performance

The purpose of the study was to investigate the effects of an 11-week unilateral versus bilateral plyometric training intervention on maximal isometric voluntary (MVC) knee extensor torque, countermovement jump height (CMJ), running economy (RE) and 3-km time trial (TT) performance. Twenty-seven recreationally trained endurance runners (12 females and 15 males) were randomly assigned to one of three groups: unilateral plyometric training (UPT; n = 9), bilateral plyometric training (BPT; n = 9) and control (CON; n = 9). RE, VO2max, 3-km treadmill TT, isometric MVC (bilateral and unilateral) and CMJ (bilateral and unilateral) were measured prior to and after 11 weeks of training (UPT and BPT; volume equated, 20-40 minutes, 2-3 days/week). Separate two-way repeated measures ANOVAs were used to assess within and between group differences in RE, VO2max, 3-km TT, maximal isometric knee extensor torque and CMJ. Following 11 weeks of plyometric training there were significant improvements in RE (UPT 5.6%; BPT 4.9%, p &lt; 0.01) and 3-km TT performance (UPT 2.4%; BPT 2.5%, p &lt; 0.01) in addition to CMJ (UPT 12.5%; BPT 14.5%, p &lt; 0.01) and maximal isometric knee extensor torque in the unilateral group (14.0%, p &lt; 0.01). No significant differences in VO2max or anthropometric measures were detected (p &gt; 0.05). No statistically significant differences between training interventions (p &gt; 0.05) were detected in any measure. These data demonstrate that UPT and BPT result in similar improvements in RE and 3-km TT run performance in recreational distance runners.

Effects of Unilateral Versus Bilateral Plyometric Training on Endurance Running Performance

The purpose of the study was to investigate the effects of an 11-week unilateral versus bilateral plyometric training intervention on maximal isometric voluntary (MVC) knee extensor torque, countermovement jump height (CMJ), running economy (RE) and 3-km time trial (TT) performance. Twenty-seven recreationally trained endurance runners (12 females and 15 males) were randomly assigned to one of three groups: unilateral plyometric training (UPT; n = 9), bilateral plyometric training (BPT; n = 9) and control (CON; n = 9). RE, VO2max, 3-km treadmill TT, isometric MVC (bilateral and unilateral) and CMJ (bilateral and unilateral) were measured prior to and after 11 weeks of training (UPT and BPT; volume equated, 20-40 minutes, 2-3 days/week). Separate two-way repeated measures ANOVAs were used to assess within and between group differences in RE, VO2max, 3-km TT, maximal isometric knee extensor torque and CMJ. Following 11 weeks of plyometric training there were significant improvements in RE (UPT 5.6%; BPT 4.9%, p &lt; 0.01) and 3-km TT performance (UPT 2.4%; BPT 2.5%, p &lt; 0.01) in addition to CMJ (UPT 12.5%; BPT 14.5%, p &lt; 0.01) and maximal isometric knee extensor torque in the unilateral group (14.0%, p &lt; 0.01). No significant differences in VO2max or anthropometric measures were detected (p &gt; 0.05). No statistically significant differences between training interventions (p &gt; 0.05) were detected in any measure. These data demonstrate that UPT and BPT result in similar improvements in RE and 3-km TT run performance in recreational distance runners.

Effect of Photobiomodulation Therapy in the 1500 m Run: An Analysis of Performance and Individual Responsiveness.

Objective: The aims of this study were to verify the effects of photobiomodulation therapy (PBMT) on time trial run performance over 1500 m, as well as on individual responsiveness of recreative runners. Materials and methods: Nineteen recreationally trained runners participated in a randomized, crossover, double-blind placebo-controlled trial. The study was divided in four sessions: (1) incremental maximal running test; (2) 1500 m run control (without placebo or PBMT); and (3, 4) PBMT or placebo before 1500 m run. PBMT or placebo was applied over 14 sites per lower limb immediately before time trial run using a mixed wavelength device (33 diodes: 5 LASERs of 850 nm, 12 LEDs of 670 nm, 8 LEDs of 880 nm, and 8 LEDs with 950 nm). PBMT delivered 30 J per site, with a total energy dose of 840 J. Physiological variables [maximal oxygen uptake (VO2MAX), velocity associated to VO2MAX (vVO2MAX), peak of velocity, and respiratory compensation point (RCP)] were assessed during incremental maximal test. During 1500 m races we accessed the following: time, heart rate, and lower limb rate perception exertion per lap, total time, and blood lactate concentration ([Lac]). Results: PBMT had no significant difference and likely trivial effect for performance in the total time trial run over 1500 m compared to placebo. In the responsiveness analyses, 10 participants positively responded to PBMT, whereas total time reduced for responders (-10.6 sec; -3.18%) and increased for nonresponders (+6.0 sec; +1.73%). Responders presented higher aerobic parameters (VO2MAX and RCP) than nonresponders. Moreover, responders had lower time per lap and [Lac] (1 and 3 min) when PBMT was applied. Conclusions: PBMT applied immediately before running in noncontrolled environment was not able to improve the 1500 m performance of recreationally trained runners. However, responders to PBMT presented higher aerobic capacity than nonresponders.

No significant effect of caffeine on five kilometer running performance after muscle damage.

Caffeine has documented hypoalgesic effects during exercise. However, there is a lack of research focusing on caffeine's potential analgesic effects to ameliorate delayed onset muscle soreness. A placebo controlled randomized cross-over trial was carried out to determine if 5mg/kg of body weight (mg/kgBW) of caffeine attenuates muscle pain and improves 5k running performance following delayed onset muscle soreness. Prior to participating, eleven runners (9 male; 2 female; age, 24.5±6.3years; height, 173.6±7.8cm; body mass, 66.3±7.5kg; BMI, 23.18kg/m2±1.6; VO2max 61.0±6.1ml/kg/min-1), were asked to discontinue supplement use for 72 hours and abstain from caffeine consumption for 48 hours. Participants performed a 30-minute downhill run on a treadmill set at -10% grade at 70% VO2max to induce delayed onset of muscle soreness. Participants then returned 48 hours after to complete a 5k time trial run where they consumed either 5mg/kgBW of caffeine or a placebo. Rate of perceived exertion and heart rate were taken every two minutes during the trial. There was no detectable statistical difference between 5k performance between caffeine (1074.9±119.7 sec) or placebo (1053.8±86.8 sec) (p=.41). Algometer readings were similar between both treatments for muscle soreness in the rectus femoris (p=.791) and the vastus medialis oblique (p=.371). Muscle soreness ratings were found to be greater in the caffeine condition compared to the placebo condition (p=.030). There was no effect of treatment on rating of perceived exertion between conditions (p=.574). The present study suggests that caffeine is not effective at reducing muscle soreness, rating of perceived exertion, or improving running performance in a time trial in the presence of muscle soreness.

Isometric mid-thigh pull force-time characteristics: A good indicator of running performance

Objectives: The relationship between force-time characteristics obtained from isometric mid-thigh pull (IMTP) and endurance running performance has not been studied. The purpose of this study was to investigate the relationships between force-time characteristics obtained from IMTP with indicators of endurance running performance. Design and Methods: Participants attended a familiarisation session to be familiarised with all testing protocols. Subsequently, they completed the IMTP and a 2.4-km run time trial (2.4-kmTT) on the first testing session. Post 48-72 h of the first session, they then performed a running economy (RE) test at 12 km.h‒1 and graded exercise test on the second testing session. Results: Significant inverse correlations between all IMTP measures and 2.4kmTT was observed (r = -0.53 to -0.78, p < 0.01). Similarly, all IMTP measures were significantly correlated to maximal aerobic speed (r = 0.38 to 0.66, p < 0.05) except Force at 150 ms. There were significant correlations between IMTP peak force, net peak force and rate of force development (0-150 ms) with lower limb stiffness (r = 0.41 to 0.49, p < 0.05). Force at 100 ms and all rate of force development measures were significantly correlated to RE (r = -0.44 to -0.68, p < 0.05). Conclusion: Findings showed that measures obtained from IMTP are good indicators of endurance running performance and can provide insights into the force generating capability required by endurance runners. In addition, the significant correlations between strength measures and running performance suggest that muscular strength may be an important determinant of running performance.

The Effects of 10-Day Exogenous Ketone Consumption on Repeated Time Trial Running Performances: A Randomized-Control Trial

Introduction The effects of ketone salt supplementation on repeated short-distance running time trial (TT) performance in well-trained subjects remain unknown. Purpose To determine the effects of 10-day exogenous ketone salt supplementation on two consecutive 800 m running TTs in endurance-trained subjects. Methods Male and female subjects were randomly allocated to one of the following groups: Ketone (KET) (n = 16) or placebo (CON) (n = 16) (8 m, 8f per group). Subjects underwent two consecutive 800 m TTs before and after a 10-day treatment on a self-propelled treadmill. Time-to-completion of the first (TT1) and second (TT2) TT, the average time-to-completion (TTAVG), and blood lactate response during each TT was measured pre-post-treatment. Changes in blood ketone levels in response to a single dosing were measured pre- and post-treatment. Data was analyzed with a mixed factorial ANOVA with significance set to p < 0.05. Results KET demonstrated a faster TTAVG from pre- to post-treatment (-6.1 ± 8.9 s; p = 0.02) while CON showed no change. At pre- and post-treatment, CON showed no acute changes in blood ketones after a single-dosing while KET demonstrated a significant increases (Pretreatment = +0.4 ± 0.3 mmol/L; p < 0.001; Post-Treatment = +0.4 ± 0.4 mmol/L; p < 0.001). These acute single-dosing responses in blood ketone levels for KET did not change between pre- and post-treatment. There were no interactions for blood lactate response to exercise or fatigue index. Conclusions In trained subjects, 10 days of ketone salt supplementation does not affect performance in an initial bout of short-distance running, such as during TT1. However, ergogenic effects may be observed under fatigue conditions for example during a repeated running bout.

Set distance time trials for predicting maximal aerobic speed in female Australian Rules Footballers

ObjectivesMaximal aerobic speed (MAS) may be predicted from 2.0km time trial (TT) running speed in male Australian Rules football (AF) players. Given the between-sex differences in physiological variables precursory to endurance performance, and the impact of this on MAS distance limit, this study determined running speed across various TT distances best approximating MAS in female AF players. Method33 female AF players completed assessments of MAS and TT performance separated by at least 48h. In a randomised order, half of the athletes completed TT distances of 1.2, 1.6 and 2.0km, and the other half completed distances of 1.4, 1.8 and 2.2km. Bias, limits of agreement (LOA) and linear mixed modelling determined agreement between TT-derived running speed and MAS. ResultsAverage speed for all TT distances were different to MAS (bias≥0.59±0.45km·h−1; p≤0.015) with the exception of the 1.4km TT (bias=−0.12±0.26km·h−1; p=0.34). LOA was narrowest for the 1.4km TT (±0.76km·h−1; ±6.1%) compared to other TT distances (±0.82–1.67km·h−1; ±6.7–12.9%). A significant linear association between bias and TT distance (r=−0.73; p<0.001) indicated TT speed would be equal to MAS when a 1.4–1.5km TT was completed, and that MAS may be predicted from any distance between 1.2 and 2.2km. ConclusionsMAS was best approximated by a 1.4–1.5km TT in female AF players, but may be predicted from TT speed for any distance between 1.2 and 2.2km. TT-derived MAS provides a time and resource efficient method for the quantification of aerobic fitness and prescription of future training intensities.

The Impact of Wrist Percooling on Physiological and Perceptual Responses during a Running Time Trial Performance in the Heat.

Environmental heat stress poses significant physiological challenge and impairs exercise performance. We investigated the impact of wrist percooling on running performance and physiological and perceptual responses in the heat. In a counterbalanced design, 13 trained males (33 ± 9 years, 15 ± 7% body fat, and maximal oxygen consumption, VO2max 59 ± 5 mL/kg/min) completed three 10 km running time trials (27 °C, 60% relative humidity) while wearing two cooling bands: (1) both bands were off (off/off), (2) one band on (off/on), (3) both bands on (on/on). Heart rate (HR), HR variability (HRV), mean arterial pressure (MAP), core temperature (TCO), thermal sensation (TS), and fatigue (VAS) were recorded at baseline and recovery, while running speed (RS) and rating of perceived exertion (RPE) were collected during the 10 km. Wrist cooling had no effect (p > 0.05) at rest, except modestly increased HR (3–5 ∆beats/min, p < 0.05). Wrist percooling increased (p < 0.05) RS (0.25 ∆mi/h) and HR (5 ∆beats/min), but not TCO (∆ 0.3 °C), RPE, or TS. Given incomplete trials, the distance achieved at 16 min was not different between conditions (off/off 1.96 ± 0.16 vs. off/on 1.98 ± 0.19 vs. on/on 1.99 ± 0.24 miles, p = 0.490). During recovery HRV, MAP, or fatigue were unaffected (p > 0.05). We demonstrate that wrist percooling elicited a faster running speed, though this coincides with increased HR; although, interestingly, sensations of effort and thermal comfort were unaffected, despite the faster speed and higher HR.

Dose response of a novel exogenous ketone supplement on physiological, perceptual and performance parameters

BackgroundInterest into the health, disease, and performance impact of exogenous ketone bodies has rapidly expanded due to their multifaceted physiological and signaling properties but limiting our understanding is the isolated analyses of individual types and dose/dosing protocols.MethodsThirteen recreational male distance runners (24.8 ± 9.6 years, 72.5 ± 8.3 kg, VO2max 60.1 ± 5.4 ml/kg/min) participated in this randomized, double-blind, crossover design study. The first two sessions consisted of a 5-km running time trial familiarization and a VO2max test. During subsequent trials, subjects were randomly assigned to one (KS1: 22.1 g) or two (KS2: 44.2 g) doses of beta-hydroxybutyrate (βHB) and medium chain triglycerides (MCTs) or flavor matched placebo (PLA). Blood R-βHB, glucose, and lactate concentrations were measured at baseline (0-min), post-supplement (30 and 60 min), post-exercise (+ 0 min, + 15 min). Time, heart rate (HR), rating of perceived exertion (RPE), affect, respiratory exchange ratio, oxygen consumption (VO2), carbon dioxide production, and ventilation were measured during exercise. Cognitive performance was evaluated prior to and post-exercise.ResultsKS significantly increased R-βHB, with more potent and prolonged elevations in KS2, illustrating an administrative and dosing effect. R-βHB was significantly decreased in KS1 compared to KS2 illustrating a dosing and exercise interaction effect. Blood glucose elevated post-exercise but was unchanged across groups. Blood lactate significantly increased post-exercise but was augmented by KS administration. Gaseous exchange, respiration, HR, affect, RPE, and exercise performance was unaltered with KS administration. However, clear responders and none-responders were indicated. KS2 significantly augmented cognitive function in pre-exercise conditions, while exercise increased cognitive performance for KS1 and PLA to pre-exercise KS2 levels.ConclusionNovel βHB + MCT formulation had a dosing effect on R-βHB and cognitive performance, an administrative response on blood lactate, while not influencing gaseous exchange, respiration, HR, affect, RPE, and exercise performance.

The Effects Of One-week Exogenous Ketone Consumption On Short Distance Time Trial Running Performance

Currently, there is equivocal knowledge concerning the effects of ketone salt supplementation on short distance running time trial (TT) performance in well-trained subjects. PURPOSE: To determine the effects of one-week exogenous ketone salt supplementation on 800m running TT performance during non-fatigued and pre-exhaustive states in endurance-trained subjects. METHODS: In a randomized, double-blind, placebo-controlled study, endurance-trained male and female participants were allocated to one of the following treatment groups for 8 days following an initial familiarization visit: Ketone supplementation (KET) (n=16) or placebo control (CON) (n=16). Subjects underwent two consecutive 800m TT before and after the 8-day treatment period on a self-propelled, non-motorized treadmill. Time-to-completion of the first (TT1) and second (TT2) TTs, the average time-to-completion across both TTs, and blood lactate response during the TTs were measured pre- and post-treatment. A mixed factorial ANOVA was used for data analysis. RESULTS: KET alone exhibited a significant increase in blood β-hydroxybutyrate from pre-post-treatment (p<0.05). A group x time interaction was only detected for TT2 performance (p<0.05) but not TT1. There was no pre- to post-treatment change in TT1 performance in either group. CON demonstrated no change in TT2 performance from pre- to post-treatment; however, KET improved TT2 performance as reflected by a 3.7% faster time-to-completion from pre- to post-treatment (p<0.05). When examining the average time-to-completion across both TTs, there was a significant group x time interaction (p=0.04). CON showed no change while KET demonstrated a faster average time-to-completion from pre- to post-treatment (p<0.05). Blood lactate response to TTs decreased (p<0.05) in KET but not CON. CONCLUSIONS: In endurance-trained subjects, ketone salt supplementation does not appear to affect short-distance running TT performance in a non-fatigued state reflective of competition scenarios. However, ergogenic effects may be observed in high-intensity exercise when some level of exhaustion or energy substrate depletion is experienced prior, such as during training or prolonged, intermittently high-intensity sporting bouts.

Effects of an Exogenous Ketone Supplement on Five-Kilometer Running Performance.

Numerous oral ketone supplements are marketed with the claim that they will rapidly induce ketosis and improve exercise performance. The purpose of this study was to assess exercise performance time and related physiological, metabolic and perceptual responses of recreational endurance runners after ingestion of a commercially available oral ketone supplement. Recreational endurance runners (n = 10; age: 20.8 ± 1.0 years; body mass: 68.9 ± 5.6 kg; height: 175.6 ± 4.9 cm) participated in a double-blind, crossover, repeated-measures study where they were randomized to 300 mg.kg-1 body weight of an oral β-hydroxybutyrate-salt + Medium Chain Triglyceride (βHB-salt+MCT) ketone supplement or a flavor matched placebo (PLA) 60 min prior to performing a 5-km running time trial (5KTT) on a treadmill. Time, HR, RPE, affect, RER, VO2, VCO2, and VE were measured during the 5-km run. The Session RPE and affect (Feeling Scale) were obtained post-5KTT. Plasma glucose, lactate and ketones were measured at baseline, 60-min post-supplement, and immediately post-5KTT. Plasma R-βHB (endogenous isomer) was elevated from baseline and throughout the entire protocol under the βHB-salt+MCT condition (p < 0.05). No significant difference (58.3 ± 100.40 s; 95% CI: -130.12 – 13.52; p = 0.100) was observed between the βHB-salt+MCT supplement (1430.0 ± 187.7 s) and the PLA (1488.3 ± 243.8 s) in time to complete the 5KTT. No other differences (p > 0.05) were noted in any of the other physiological, metabolic or perceptual measures.