Exercise Economy Research Articles

We describe the physiological adaptations evoked during a 3-mo training block in an elite female swimmer building toward a 34.3-km ultraendurance solo swim across Lake Tahoe (ambient temperature ∼13.9°C, water temperature ∼17.5°C, and elevation 1,900 m). The athlete underwent physiological assessments including measures of resting metabolic rate, peak oxygen uptake (V̇o2peak), cycling exercise economy, simple reaction time, and grip strength. In addition to training history and measures taken before the record attempt, we captured the physiological responses immediately following completion of the 34.3 km distance. The athlete completed the ultraswim across Lake Tahoe in a record-setting 10:34:48 (hh:mm:ss)-the fastest time ever recorded for a woman. From the beginning of training to the weeks preceding the Lake Tahoe swim, resting metabolic rate increased from 1,382.9 kcal·day-1 to 1,647.6 kcal·day-1. Exercise economy and V̇o2peak remained relatively constant throughout the training. Following the 10.5-h swim, body mass changed by <1 kg. Simple reaction time and grip strength values declined to substantial and mixed quantities, respectively. This study provides insights into the training regimen adopted by a female swimmer and the physiological ramifications of a record-breaking ultraendurance performance.NEW & NOTEWORTHY Ultraendurance exercise requires cardiometabolic fitness, intentionality toward nutrient replenishment, psychological resilience, and some degree of musculoskeletal durability. When ultraendurance exercise requires sustained swimming, add to these the burdens of phase-locked breathing, immersion in cold water, and the need to stay afloat. Here, we record the record-breaking performance of an elite female ultraswimmer, demonstrating that although body mass remains stable following completion of the event, psychological processing speed is strongly compromised.

ABSTRACTPeak neuromuscular power and endurance are distinct qualities of dynamic exercise performance. Dynamometry is used to assess peak neuromuscular power, often during performance across a single joint, for example, isotonic or isokinetic torque, whereas aptitude for endurance exercise may be inferred by measurement of critical power/speed or cardiopulmonary exercise testing to determine, for example, gas exchange threshold (GET), maximum oxygen uptake (V̇O2max), and exercise economy. Specificity is a critical component of any training program, but oversimplification of the specificity principle has contributed to the view that training adaptations to increase peak neuromuscular power or the ability to endure high power outputs are mutually exclusive, due to (i) differences in the types of motor units recruited and their patterns of activation and (ii) induction of distinct, antagonistic molecular signaling pathways in response to resistance and endurance exercise training (the “interference effect”).This review explores evidence for reciprocation between peak neuromuscular power and endurance performance in sport, aging, and among general and clinical populations. We also review the molecular events that mediate peak neuromuscular power and endurance training adaptations and their interactions. Finally, we describe the musculo-cardio-pulmonary exercise test (mCPET) to demonstrate that peak neuromuscular power and aerobic mediators of endurance performance are less polar opposites and more willing partners.

ObjectivesNon-anaemic iron deficiency (IDNA) is highly prevalent in exercising females. Although iron therapy can be used to correct this issue, its impact on exercise performance is equivocal. Our aim was...

Meta-analysts have found that high-intensity interval training (HIIT) improves physical performance, but limited evidence exists regarding its effects on highly trained athletes, measures beyond maximum oxygen uptake ( O2max), and the moderating effects of different types of HIIT. In this study, we present meta-analyses of the effects of HIIT focusing on these deficits. The effects of 6 types of HIIT and other moderators were derived from 34 studies involving highly trained endurance and elite athletes in percent units via log-transformation from separate meta-regression mixed models for sprint, time-trial, aerobic/anaerobic threshold, peak speed/power, repeated-sprint ability, O2max, and exercise economy. The level of evidence for effect magnitudes was evaluated based on the effect uncertainty and the smallest important change of 1%. Compared with control training, HIIT showed good to excellent evidence for the substantial enhancement of most measures for some athlete subgroups in practically important study settings defined by effect moderators (maximum of 12.6%, for endurance female athletes after 6 weeks of aerobic traditional long intervals). The assessment of the moderators indicated good evidence of greater effects as follows: with more aerobic types of HIIT for O2max (+2.6%); with HIIT added to conventional training for most measures (+1.1-2.3%); during the competition phase for O2max (+4.3%); and with tests of longer duration for sprint (+5.5%) and time trial (+4.9%). The effects of sex and type of athlete were unclear moderators. The heterogeneity of HIIT effects within a given type of setting varied from small to moderate (standard deviations of 1.1%-2.3%) and reduced the evidence of benefit in some settings. Although athletes in some settings can be confident of the beneficial effects of HIIT on some measures related to competition performance, further research is needed. There is uncertainty regarding the mean effects on exercise economy and the modifying effects of sex, duration of intervention, phase of training, and type of HIIT for most measures. https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=236384.

To investigate metabolism and exercise economy during prolonged race simulation (>4h) in a world-class, full-distance triathlete to help guide/adjust strategies for training, nutrition, hydration, and thermoregulation. Two experimental race-simulation days, designed to mimic the demands of a full-distance triathlon, were executed by a world-class maletriathlete(MD; 25y, body weight 82kg, V˙O2max 6.2L·min-1, blood lactate threshold ∼410W, and 18km · h-1 in cycling and running) who at the time ranked second in the world. Race simulation was performed 23 and 10 days prior to competing in Challenge Roth 2023, where MD won in a new world record/best time (7:24:40h:min:s). Both test days lasted ∼4 to 5hours with physiologic testing every ∼45 to 60minutes in a "stationary" setting during cycling on a direct-mount trainer (∼320W) and treadmill running (16km · h-1), enabling gas exchange measurements (V˙O2 and respiratory exchange ratio) and other physiologic measurements of interest (ie,core temperature and heart rate). This was combined with "real activity" as repeated loops in an open-air field setting at expected race pace in swimming, biking, and running. V˙O2 was maintained at ∼4.2L·min-1, with carbohydrates being the dominant fuel for oxidation as respiratory exchange ratio values dropped from ∼1 at the start of cycling to ∼0.85 during running. Cycling economy was stable, whereas a slight impairment in running economy occurred over time. High aerobic energy turnover and stable exercise economy can be maintained in a world-class record-breaking triathlete for prolonged period of time (+4h), showcasing the importance of both for success in competition.

IntroductionOur recent meta-analyses have demonstrated that high-intensity interval training (HIIT) causes a range of mean changes in various measures and predictors of endurance and sprint performance in athletes. Here, we extend the analyses to relationships between mean changes of these measures and consider implications for understanding and improving HIIT that were not apparent in the previous analyses.MethodsThe data were mean changes from HIIT with highly trained endurance and elite other (mainly team sport) athletes in studies where two or more measures or predictors of performance were available. Relationships between changes in pairs of measures were visualized in scatterplots with points identified by aerobic and anaerobic types of HIIT; simple linear relationships were quantified via log-transformation of factor changes with a meta-regression mixed model.ResultsIn endurance athletes, there were positive linear relationships between mean changes in time-trial speed/power (reflecting competition endurance performance) and mean changes in endurance performance predictors [peak speed/power, maximal oxygen uptake (V̇O2max), and aerobic/anaerobic threshold]. There were substantial differences in time-trial speed/power between studies not explained by each predictor. Exercise economy had an unclear relationship with time-trial speed/power but a decisively negative relationship with V̇O2max. In other athletes, repeated-sprint ability had a weak positive relationship with sprint speed/power. The scatter of points in some plots was associated with the type of HIIT.DiscussionDifferences in time-trial performance between studies for a given change in peak speed/power, V̇O2max, or threshold speed/power imply that time trials should be included when assessing effects of HIIT on endurance performance. Relationships between V̇O2max, time-trial speed/power, and exercise economy suggest that combining aerobic and anaerobic types of HIIT could be more effective for endurance performance. Sprints and repeated-sprint ability are important performance measures for team-sport athletes; their poor relationship implies that both should be measured when assessing HIIT.Clinical Trial Registration:https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=236384

Montmorency cherry (MC) can improve endurance performance, but optimal pre-exercise timing of supplementation and influence of training status on efficacy are unknown. We investigated the effect of MC concentrate ingestion between 30- and 150-min pre-exercise in trained and recreational cyclists on 15-km time trial (TT) performance and exercise economy. Twenty participants (10 recreationally active, RA; 10 trained, T) completed 10min of steady-state exercise (SSE) at 40%Δ (SSE) and a TT on four separate occasions following an unsupplemented (US), 30-, 90- or 150-min pre-exercise Montmorency cherry concentrate (MCC) supplementation conditions (MCC30/90/150min). Venous and capillary blood samples were taken at regular intervals pre- and post-SSE and TT. MCC significantly improved TT performance, but not exercise economy. The greatest improvement in performance occurred following MCC90min compared to US (US 1603.1±248s vs. MCC90min 1554.8±226.7s, 2.83% performance improvement). Performance was significantly enhanced for trained (US 1496.6±173.1s vs. MCC90min 1466.8±157.6s) but not recreationally active participants. Capillary [lactate] and heart rate were significantly greater during the TT for the 90-min dose timing (p<0.05). In the MCC30min and MCC90min conditions, plasma ferulic (US 8.71±3.22nmol. L-1 vs. MCC30min 15.80±8.69nmol. L-1, MCC90min 12.65±4.84nmol. L-1) and vanillic acid (US 25.14±10.91nmol.L-1 vs. MCC30min 153.07±85.91nmol. L-1, MCC90min 164.58±59.06nmol. L-1) were significantly higher pre-exercise than in US and MCC150min conditions (p<0.05). There was no significant change in muscle oxygenation status or plasma nitrite/nitrate concentration. MCC supplementation enhanced endurance exercise performance optimally when consumed ∼90min pre-exercise producing maximal plasma phenolic metabolites during exercise. The ergogenic effect was greater for trained participants.

Ultra-endurance sports and exercise events are becoming increasingly popular for older age groups. We aimed to evaluate changes in cardiac function and physical fitness in males aged 50-60 years who completed a 50-day transoceanic rowing challenge. This case account of four self-selected males included electro- and echo-cardiography (ECG, echo), cardiorespiratory and muscular fitness measures recorded nine months prior to and three weeks after a transatlantic team-rowing challenge. No clinically significant changes to myocardial function were found over the course of the study. The training and race created expected functional changes to left ventricular and atrial function; the former associated with training, the latter likely due to dehydration, both resolving towards baseline within three weeks post-event. From race-start to finish all rowers lost 8.4-15.6 kg of body mass. Absolute cardiorespiratory power and muscular strength were lower three weeks post-race compared to pre-race, but cardiorespiratory exercise economy improved in this same period. A structured program of moderate-vigorous aerobic endurance and muscular training for>6 months, followed by 50-days of transoceanic rowing in older males proved not to cause any observable acute or potential long-term risks to cardiovascular health. Pre-event screening, fitness testing, and appropriate training is recommended, especially in older participants where age itself is an increasingly significant risk factor.

A low carbohydrate, high fat (LCHF) diet in athletes increases fat oxidation but impairs sports performance, potentially due to impaired exercise economy. Dietary nitrate supplementation can improve exercise economy via an increase in nitric oxide production, which is initiated by the reduction of nitrate to nitrite within the oral cavity. This reaction is dependent on the presence of nitrate-reducing oral bacteria, which can potentially be altered by dietary changes, including a LCHF diet. This study explored the effect of a LCHF diet on the oral microbiome and subsequent changes to plasma nitrite concentration following nitrate supplementation. Following five days of LCHF or high carbohydrate (HCHO) control dietary intervention, highly trained male race walkers consumed 140 mL beetroot juice containing 8.4 mmol nitrate; they then provided (a) blood samples for plasma nitrate and nitrite analysis and (b) saliva samples for 16S rRNA sequencing of the oral microbiome. The LCHF diet (n = 13) reduced oral bacterial diversity and changed the relative abundance of the genera Neisseria (+10%), Fusobacteria (+3%), Prevotella (−9%), and Veillonella (−4%), with no significant changes observed following the HCHO diet (n = 11). Following beetroot juice ingestion, plasma nitrite concentrations were higher for the LCHF diet compared to the HCHO diet (p = 0.04). However, the absence of an interaction with the trial (pre–post) (p = 0.71) suggests that this difference was not due to the dietary intervention. In summary, we found an increase in plasma nitrate and nitrite concentrations in response to nitrate supplementation independent of diet. This suggests the oral microbiome is adaptive to dietary changes and can maintain a nitrate reduction capacity despite a decrease in bacterial diversity following the LCHF diet.

Oral inorganic nitrate (NO3-) supplementation has been shown to increase bioavailable NO and provide potential ergogenic benefits in males; however, data in females is scarce. Estrogen is known to increase endogenous NO bioavailability and to fluctuate throughout the menstrual cycle (MC), being lowest in the early follicular (EF) phase and highest during the late follicular (LF) phase. This study examined the effects of oral NO3- supplementation on exercise economy, endurance capacity, and vascular health in young females across the MC. Ten normally menstruating females' MCs were tested in a double-blinded, randomized design during both the EF and LF phases of the MC. Participants consumed ∼13 mmol NO3-, in the form of 140 mL beetroot juice (BRJ) or an identical NO3--depleted placebo (PL) for ∼3 days before lab visits and 2 h before testing on lab visits. Plasma nitrate, nitrite, and estradiol were assessed, as was blood pressure and pulse wave velocity. Moderate-intensity exercise economy and severe intensity time to exhaustion (TTE) were tested on a cycle ergometer. As expected, plasma estradiol was elevated in the LF phase, and plasma nitrite and nitrate were elevated in the BRJ condition. Exercise economy was unaltered by BRJ or the MC, however TTE was significantly worsened by 48 s (∼10%) after BRJ supplementation (P = 0.04), but was not different across the MC with no interaction effects. In conclusion, NO3- supplementation did not affect exercise economy or vascular health and worsened aerobic endurance capacity (TTE), suggesting healthy females should proceed with caution when considering supplementation with BRJ.NEW & NOTEWORTHY Although inorganic nitrate (NO3-) supplementation has increased in popularity as a means of improving exercise performance, data in females at different phases of the menstrual cycle are lacking despite known interactions of estrogen with NO. This study revealed neither NO3- supplementation nor the menstrual cycle influenced exercise economy or vascular health in healthy young naturally menstruating females, while NO3- supplementation significantly worsened endurance capacity (10%) independent of the menstrual cycle phase.

It is known that beetroot supplements may improve exercise economy and blood pressure, but this has mainly been studied in males. Given that older female athletes are underrepresented in the literature, we aimed to determine if acute beetroot supplementation (BRS) improves exercise economy and blood pressure in masters female athletes (swimmers) during a treadmill exercise test. Methods: 11 participants (57.8±10.5 y) underwent 2 randomized, double-blinded trials, ingesting beetroot (BE) or placebo (PL). Salivary NO2- (sNO2-) and blood pressure (BP) were measured pre-ingestion (Base), pre-exercise (Pre), and 5 min post-exercise (Post). Oxygen consumption (VO2) was measured during the modified Balke test until HR reached 85% of age-predicted maximum. Exercise economy (ExEc) was defined as the average relative VO2 during min 3-4.5 of the test. sNO2- was determined using NO2- detection strips. Results: sNO2- increased from Base to Post in BE vs PL (32.5±7.0 vs 2.7±3.9% change, p=0.001). No treatment differences existed for ExEc (BE: 15.51±0.47 vs PL: 15.71±0.53 ml·kg-1·min-1, p=0.48). Diastolic BP was significantly lower in BE vs PL (Base: 74.6±1.7 vs 73.2±2.3, Pre: 73.6±1.8 vs 74.5±2.1, Post: 74.5±1.7 vs 76.1±2.2 mmHg, p=0.03, treatment by time). Conclusion: Acute BRS lowered diastolic BP, but did not improve exercise economy in these trained, normotensive athletes. Further research is warranted in menopausal and post-menopausal females, including those who are hypertensive, and in other female masters athlete groups.

Lowering of the upper body to optimize cycling time trial (TT) performance is a balance between the aerodynamic advantage related to a lower frontal area and prospective detrimental physiological effects associated with a reduction of the hip-torso angle. To explore this in elite athletes and across positions relevant for competitive cyclists, we analysed racing positions for world championships [WC] top-10 finishers and 10 national elite TT-cyclists. Subsequently, laboratory studies were completed to evaluate effects on exercise economy, muscle oxygenation and perceived exertion for the national TT-group for their habitual position and compared to standard (4-12-20˚) torso angles. Hence, covering the racing position observed for top-10 WC finishers (positioned from 4-12˚) and the national elite (range 8-18˚). Oxygen calorimetry and near-infrared spectroscopy revealed that there was no difference in overall energy expenditure, delta exercise efficiency or muscle oxygenation across the investigated range of positions. However, rating of perceived exertion was significantly elevated for the lowest position (4˚ torso angle) compared to the rider’s habitual position. This lets us conclude that elite TT-cyclists can acutely adopt to a very low upper body position without compromising exercise economy or muscle oxygenation and some WC-level TT riders have adopted this low (4˚) racing position. However, the elevated perception of exertion with an acute reduction of the torso-hip angle indicates that it presumably requires specific training in the position or factors not related to exercise economy and muscle oxygenation determine if a rider in practice can perform in the very low position.

Purpose: Positive expiratory pressure (PEP) exhalation during exercise is reported to improve body adaptation to exercise and enhance the exercise tolerance in patients with chronic obstructive pulmonary disease. Wearing mouthguards results in lower oxygen consumption and increased performance by increasing PEP in athletes. Airway resistance during expiration can be manipulated by phonation. Thus, the aim of our study was to examine the effects of phonated breathing on cardiopulmonary adaptation to moderate exercise and subsequent recovery. Methods: 26 young healthy participants conducted the same moderate steady cycling protocol using three different breathing patterns: spontaneous breathing (BrP1), phonated breathing pronouncing the sound “h” (BrP2) and phonated breathing pronouncing the sound “sh” (BrP3). Heart rate, oxygen consumption, CO2 production, respiratory rate, tidal volume, respiratory exchange ratio and ventilatory equivalents were measured (Cosmed, Italy) before, during and 20 minutes after cycling. Data were analyzed using SPSS, with significance level p&lt;0.05. Results: The analysis revealed no significant differences related to the breathing economy; respiratory rate was increased, and tidal volume decreased with spontaneous breathing compared to both phonated breathing patterns during exercise; no effect of BrPs on cardiopulmonary parameters was found in recovery. Conclusion: Our results do not confirm the assumption that PEP breathing improves exercise economy probably because of the low exercise intensity applied. Further studies should be conducted at higher exercise loads or in patients with pulmonary dysfunction.

Exercise efficiency and economy are key determinants of endurance exercise performance. In this cross-over intervention trial, we investigated the effect of adherence to a low carbohydrate, high fat (LCHF) diet versus a high carbohydrate (HC) diet on gross efficiency (GE) and (OC) during exercise, both after 2 days and after 14 days of adherence. Fourteen recreational male athletes followed a two-week LCHF diet (<10 energy % carbohydrate) and a two-week HC diet (>50 energy % carbohydrate), in random order, with a wash-out period of three weeks in between. After 2 and 14 days on each diet, the athletes performed a 90-minutes submaximal exercise session on a bicycle ergometer. Indirect calorimetry measurements were done after 60 minutes of exercise to calculate GE and OC. GE was significantly lower on the LCHF diet compared to the HC diet, after 2 days (17.6±1.9 vs. 18.8±1.2%, P=0.011, for the LCHF and HC diet respectively), not after 14 days. OC was significantly higher on the LCHF diet compared to the HC diet, after 2 days (1191±138 vs. 1087±72 mL O<inf>2</inf>/kCal, P=0.003, for the LCHF and HC diet respectively), and showed a strong tendency to remain higher after 14 days, P=0.018. Although LCHF diets are popular strategies to increase fat oxidation during exercise, adherence to a LCHF diet was associated with a lower exercise efficiency and economy compared to a HC diet.

To determine the effects of dietary nitrate (NO3-) supplementation on physiological responses, cognitive function, and performance during heavy load carriage in military cadets. Ten healthy males (81.0 ± 6.5kg; 180.0 ± 4.5cm; 56.2 ± 3.7ml·kg·min-1 VO2max) consumed140mL·d-1 of beetroot juice (BRJ; 12.8mmol NO3-) or placebo (PL) for six d preceding an exercise trial, which consisted of 45min of load carriage (55% body mass) at 4.83km·h-1 and 1.5% grade, followed by a 1.6-km time-trial (TT) at 4% grade. Gas exchange, heart rate, and perceptual responses were assessed during constant-load exercise and the TT. Cognitive function was assessed immediately prior to, during, and post-exercise via the psychomotor vigilance test (PVT). Post-TT HR (188 ± 7.1 vs. 185 ± 7.4; d = 0.40; p = 0.03), mean tidal volume (2.15 ± 0.27 vs. 2.04 ± 0.23; p = 0.02; d = 0.47), and performance (770.9 ± 78.2s vs. 809.8 ± 61.4s; p = 0.03; d = 0.63) were increased during the TT with BRJ versus PL. There were no effects of BRJ on constant-load gas exchange or perceptual responses, and cognitive function was unchanged at all time points. BRJ supplementation improves heavy load carriage performance in military cadets possibly as a result of attenuated respiratory muscle fatigue, rather than enhanced exercise economy.

Acclima(tiza)tion to heat or hypoxia enhances work capacity in hot and hypoxic environmental conditions, respectively; an acclimation response is considered to be mediated by stimuli-specific molecular/systemic adaptations and potentially facilitated by the addition of exercise sessions. Promising findings at the cellular level provided the impetus for recent studies investigating whether acclimation to one stressor will ultimately facilitate whole body performance when exercise is undertaken in a different environmental condition. The present critical Mini-Review examines the theory of cross-adaptation between heat and hypoxia with particular reference to the determinants of aerobic performance. Indeed, early functional adaptations (improved exercise economy and enhanced oxyhemoglobin saturation) succeeded by later morphological adaptations (increased hemoglobin mass) might aid acclimatized humans perform aerobic work in an alternative environmental setting. Longer-term acclimation protocols that focus on the specific adaptation kinetics (and further allow for the adaptation reversal) will elucidate the exact physiological mechanisms that might mediate gains in aerobic performance or explain the lack thereof.

Purpose: Aging deteriorates metabolic flexibility (MF). Moreover, recent studies show that glycolysis is barely increased despite impoverished lipid metabolism, in addition to increased relevance of muscle power in older adults. This study aims to analyze MF, i.e., fat and carbohydrates oxidation rates (FATox and CHOox), and the point of maximal fat oxidation (MFO), in a group of active women over-60. It also aims to delve into the role of power production and mechanical efficiency regarding MF. This will help to decipher their metabolic behavior in response to increasing intensity. Methods: Twenty-nine women (66.13 ± 5.62 years) performed a submaximal graded cycling test, increasing 10 W each 3-min15-s, from 30 W to the second ventilatory threshold (VT2). Muscle power was adjusted with a Saris-H3 roller, together with a continuous gas analysis by indirect calorimetry (Cosmed K4b2). Pre and post-test blood lactate (BLa) samples were included. Frayn’s equations, MFO and CHOoxpeak (mg/min/kg FFM) were considered for MF analysis (accounting for average VO2 and VCO2 in each last 60-s), whilst delta and gross efficiencies (DE%, GE%), and exercise economy (EC), were added for Mechanical Efficiency. Mean comparisons regarding intensities 60, 80 and 100% at VT2, completed the study together with correlation analysis among the main variables. Results: MFO and CHOoxpeak were small (6.35 ± 3.59 and 72.79 ± 34.76 g/min/kgFFM respectively) for a reduced muscle power (78.21 ± 15.84 W). Notwithstanding, GE% and EC increased significantly (p < 0.01) with exercise intensity. Importantly, coefficients of variation were very large confirming heterogeneity. Whilst muscle power outcomes correlated significantly (p < 0.01) with MFO (r = 0.66) and age (r = −0.62), these latter failed to be associated. Only GE% correlated to CHOoxpeak (r = −0.61, p < 0.01) regarding mechanical efficiency. Conclusions: Despite being active, women over-60 confirmed impaired substrates switching in response to exercise, from both FAT and CHO pathways. This limits their power production affecting exercise capacity. Our data suggest that decreased power with age has a key role above age per se in this metabolic inflexibility. Vice versa, increasing power seems to protect from mitochondrial dysfunction with aging. New studies will confirm if this higher efficiency when coming close to VT2, where GE is the more informative variable, might be a protective compensatory mechanism.

The root of the matter: nitrate-rich beetroot juice reduces skeletal muscle O2 uptake during exercise.

This study examined if acute dietary nitrate supplementation (140 mL beetroot juice, BRJ) would reduce oxygen consumption (V̇O2) during cycling at power outputs of 50 and 70% maximal oxygen consumption in 14 well-trained female Canadian University Ringette League athletes. BRJ had no effect on V̇O2 or heart rate but significantly reduced ratings of perceived exertion (RPE) at both intensities. Individually, 4 participants responded to BRJ supplementation with a ≥3% reduction in V̇O2 at the higher power output. Novelty: Acute BRJ supplementation did not improve exercise economy in well-trained females, but significantly reduced RPE. However, 4/14 subjects did respond with a ≥3% V̇O2 reduction.

Given the importance of exercise economy to endurance performance, we implemented two strategies purported to reduce the oxygen cost of exercise within a 4 week training camp in 21 elite male race walkers. Fourteen athletes undertook a crossover investigation with beetroot juice (BRJ) or placebo (PLA) [2 d preload, 2 h pre-exercise + 35 min during exercise] during a 26 km race walking at speeds simulating competitive events. Separately, 19 athletes undertook a parallel group investigation of a multi-pronged strategy (MAX; n = 9) involving chronic (2 w high carbohydrate [CHO] diet + gut training) and acute (CHO loading + 90 g/h CHO during exercise) strategies to promote endogenous and exogenous CHO availability, compared with strategies reflecting lower ranges of current guidelines (CON; n = 10). There were no differences between BRJ and PLA trials for rates of CHO (p = 0.203) or fat (p = 0.818) oxidation or oxygen consumption (p = 0.090). Compared with CON, MAX was associated with higher rates of CHO oxidation during exercise, with increased exogenous CHO use (CON; peak = ~0.45 g/min; MAX: peak = ~1.45 g/min, p < 0.001). High rates of exogenous CHO use were achieved prior to gut training, without further improvement, suggesting that elite athletes already optimise intestinal CHO absorption via habitual practices. No differences in exercise economy were detected despite small differences in substrate use. Future studies should investigate the impact of these strategies on sub-elite athletes’ economy as well as the performance effects in elite groups.