Endurance performance is predicted by maximal oxygen uptake, its fractional utilisation at lactate threshold (FULT) and exercise economy. These variables are used to estimate speed or power at lactate threshold (LT) and lactate turnpoint (LTP), which serve as performance proxies. This study examined the relationships between these variables in a large cohort of runners and cyclists and quantified their relative contributions to performance prediction. 495 runners (105 females) and 393 cyclists (42 females) completed incremental exercise tests to determine maximal oxygen uptake (running [R]: 56mL/kg/min, 3.94 L/min; cycling [C]: 52mL/kg/min, 3.99 L/min), economy (R: 220mL/kg/km; C: 14.7mL/min/W), FULT(R: 78%; C: 70%), FULTP(R: 88%; C: 84%), and speed or power at LT (R: 12.0km/h; C: 190 W) and LTP (R: 13.9km/h; C: 240 W). Single and multiple linear regression models were used to examine the relationship and relative contribution of physiological determinants to performance proxies. Speed or power at LT and LTP correlated strongly and positively with maximal oxygen uptake (R2 = 0.65-0.77;P < 0.001), and inversely with economy (R2 = 0.24-0.26;P < 0.001). In contrast, trivial relationships were observed with FULT (R2 ≤ 0.04;P = 0.01-0.05) or FULTP(R2 ≤ 0.01;P = 0.01-0.09). Regression models estimating LT and LTP from physiological determinants showed very strong agreement with measured performance proxies (R2 = 0.94-0.99;P < 0.001), indicating consistency in their relative contribution to performance proxies. Maximal oxygen uptake contributed most to performance proxies (65-76%) followed by running economy (20-24%), with marginal contributions from FULT or FULTP(4-11%). These results indicate that maximal oxygen uptake and economy collectively predict ~ 95% of speed or power at LT and LTP, and by extension performance, whilst the contribution of FULT or FULTPis limited in populations with heterogeneous characteristics.

Background/Objectives: Masters athletes are adults aged ≥40 who compete in sport, exhibiting superior physical function and healthier aging than their sedentary peers. However, even highly trained masters athletes experience age-related performance declines. Women masters athletes represent a growing yet understudied population who may face unique physiological challenges. This scoping review synthesizes literature from 1984 to 2024, examining the impact of age and menopause on determinants of endurance performance in women masters athletes. Methods: Following JBI scoping review methodology, six databases were searched (Medline, Embase, Central, CINAHL, SPORTdiscus, Scopus). Studies were evaluated for population characteristics, methodological approaches, and physiological determinants of performance (i.e., aerobic capacity, lactate kinetics, and exercise economy). Results: Twenty-nine studies were included. Most (n = 28) assessed aerobic capacity, reporting declines between 0.36 and 0.84 mL·kg-1·min-1·year-1 (0.5-2.4%·year-1). These reductions were primarily associated with decreased cardiac output followed by changes in body composition. Training volume emerged as a predictor of aerobic capacity, but the effects of menopause were unclear. Findings on lactate kinetics and exercise economy were mixed but preliminary research indicated that lactate threshold relative to VO2max generally increased, peak lactate remained stable and energy cost increased with age. Fitness and health characteristics among women athletes differed from sedentary populations, emphasizing the need for athlete-specific data to support training and health decisions. Conclusions: Aging is associated with decreased aerobic capacity and variable changes in lactate kinetics and exercise economy. While training volume may attenuate performance decrements, the impact of menopause remains uncertain, underscoring the need for longitudinal research to better support this growing segment of the population.

This study compares the effects of high-intensity interval training (HIIT) and moderate-to-vigorous-intensity continuous training (MVICT) on physiological adaptations and physical performance across a broad population, from the general public to athletes. Additionally, it also explores how participant characteristics (e.g., sex, age, and training status) and training protocol parameters (e.g., mode, interval type, and intensity) influence the comparison. Following PRISMA guidelines, a systematic search was conducted in PubMed, Web of Science, and CNKI databases, completed on September 21, 2024. Eligible studies were randomized controlled trials comparing the chronic effects of HIIT and MVICT. A three-level meta-analysis was employed to calculate standardized mean differences (SMD, Hedge's g), with subgroup analyses and meta-regression used to examine potential moderators of any observed effects. A total of 115 studies involving 3196 participants were included, with a mean age range from 8 to 68 years, spanning populations from untrained sedentary individuals to elite/world-class athletes. Compared to MVICT, HIIT demonstrated significantly superior improvements in relative maximal oxygen uptake (SD = 1.30 mL·kg-1·min-1, g = 0.39, 95% CI [0.27, 0.51]), absolute maximal oxygen uptake (SD = 0.09 L·min-1, g = 0.29, 95% CI [0.15, 0.43]), maximal aerobic power/speed (g = 0.31, 95% CI [0.17, 0.47]), and mean anaerobic power (g = 0.47, 95% CI [0.08, 0.86]). No significant differences were observed between HIIT and MVICT in peak anaerobic power (g = 0.31, 95% CI [-0.06, 0.68]), first intensity thresholds (g = 0.43, 95% CI [-0.38, 1.25]), second intensity threshold (g = 0.06, 95% CI [-0.25, 0.36]), exercise economy (g = 0.26, 95% CI [-0.03, 0.54]), and on indices of physical performance (g = 0.04, 95% CI [-0.46, 0.54]). Subgroup analyses revealed that training status (6-tiered participant classification framework), age, sex, interval type, and exercise mode significantly moderated the effect. Specifically, compared to MVICT, HIIT demonstrated greater improvements in maximal oxygen uptake among individuals at Tier 0 (inactive; g = 0.34), Tier 1 (recreationally active; g = 0.57), and Tier 3 (elite/national; g = 0.83), in males (g = 0.43) and mixed-sex populations (g = 0.42), using short-interval (g = 0.55) or long-interval HIIT (g = 0.57), and with rowing (g = 0.71), running (g = 0.53), or cycling (g = 0.29) as the training modes. Compared to MVICT, HIIT offers superior benefits for improving maximal oxygen uptake and anaerobic capacity, whereas both modalities show comparable outcomes for intensity thresholds, exercise economy, and physical performance. The relative superiority of HIIT compared to MVICT is influenced by participant characteristics (e.g., training background, age, and sex) and by the characteristics of the HIIT protocol.

While traditional sports nutrition emphasizes high carbohydrate intake for endurance athletes, trained athletes may achieve metabolic adaptation to low-carbohydrate and ketogenic diets with maintained or improved performance outcomes. This systematic review and meta-analysis synthesize evidence on the effects of low-carbohydrate (≤130 g·day-1 or ≤25% total energy) and ketogenic (<50 g·day-1 or <10% total energy) diets on aerobic performance variables in trained athletes. A comprehensive search of five electronic databases (PubMed, SCOPUS, Web of Science, SPORTDiscus, and Cochrane Central Register of Controlled Trials) identified 33 aerobic-focused studies meeting comprehensive inclusion criteria. Selected studies examined trained athletes (≥6 months structured training, age 18-45 years) randomized to low-carbohydrate, ketogenic, or high-carbohydrate control conditions with outcome data on aerobic performance variables (VO2max, time trial performance, time to exhaustion, and exercise economy) and metabolic markers (fat oxidation and substrate utilization). Quality assessment employed Newcastle-Ottawa Scale methodology. Maximal aerobic capacity (VO2max) was preserved in 50.0% of studies, with 11.1% documenting improvements. Submaximal exercise economy showed the greatest sensitivity, with 50.0% documenting impaired efficiency. Time to exhaustion demonstrated context-dependent effects, with 69.2% maintaining performance. All 30 studies measuring fat oxidation demonstrated consistent increases (+28% to +200%). Critically, temporal analysis identified a 1-week adaptation threshold: studies measuring outcomes within ≤7 days documented performance impairment, while studies measuring at >1 week consistently demonstrated maintained or improved performance. Low-carbohydrate diets reliably induce metabolic adaptation characterized by dramatically increased fat oxidative capacity. However, aerobic performance responses are nuanced, with preserved maximal aerobic power, transient submaximal efficiency impairments, and context-dependent endurance effects. Adaptation involves initial acute-phase decrements (≤7 days) followed by recovery. Evidence supports periodized carbohydrate strategies balancing metabolic adaptation benefits from low-carbohydrate training phases with carbohydrate requirements during competition.

The development and trainability of key physical capabilities during childhood and adolescence are fundamental for health, performance, and injury prevention. This symposium will explore three interrelated domains: (1) cardiorespiratory fitness, focusing on maximal aerobic capacity (VO₂max), exercise economy, and endurance performance; (2) neuromuscular performance, encompassing muscle morphology as well as neural components of strength and power production; and (3) sensorimotor function, including postural control, motor coordination, and motor skill execution. Together, these systems underpin cardiorespiratory and muscular fitness, movement efficiency, and motor proficiency across growth and maturation. The symposium aims to elucidate typical developmental trajectories of these capabilities from early childhood through adolescence and to determine their specific trainability at different maturational stages. By integrating evidence from longitudinal and interventional studies, along with our own recent pilot data from the decade-study, we will discuss underlying physiological mechanisms, sex- and maturation-related differences, and methodological challenges in distinguishing growth-related changes from true training adaptations. Ultimately, the session seeks to establish an integrative framework describing how biological development and targeted training interact to shape performance potential, coordination, and health outcomes in youth, thereby, providing implications for evidence-based training design, talent development, and long-term well-being.

Beetroot juice (BRJ), a concentrated dietary source of nitrate alongside betalains and polyphenols, influences physiology through enhanced nitrate-nitrite-NO bioavailability, antioxidant activity, and interactions with oral and gut nitrate-reducing microbiota. The efficiency of these mechanisms depends on dose, timing, and preservation of oral bacteria, with antibacterial mouthwash or thiocyanate-rich foods potentially blunting NO2- generation. Acute BRJ ingestion consistently elevates circulating nitrate and nitrite, yet its impact on glucose, insulin, and lipid regulation is modest; chronic intake may reinforce nitrate-reduction capacity, improve redox balance, and shift microbial composition, though long-term metabolic outcomes remain variable. Cardiovascular adaptations appear more coherent, with acute reductions in systolic blood pressure and improved endothelial function complemented in some cases by microvascular enhancements during multi-week supplementation. Neuromuscular and cognitive effects are less uniform; BRJ does not reliably increase maximal strength or global cognition but may support electrophysiological recovery after muscle-damaging exercise and improve executive performance under fatigue. In exercise settings, dose and timing are critical, as BRJ most consistently benefits endurance performance by reducing oxygen cost, improving exercise economy, and enhancing time-trial or time-to-exhaustion outcomes, whereas effects on sprint, power, and team-sport tasks are more sensitive to contraction duration, recovery intervals, and athlete training status. Overall, available evidence supports a role for NO-mediated vascular and metabolic pathways in the physiological effects of BRJ, although marked inter-individual variability highlights the need for responder-focused dosing strategies and further mechanistic investigation integrating metabolic, microbial, and performance-related outcomes.

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.

BackgroundPhase angle (PhA), derived from bioelectrical impedance analysis (BIA), is considered a non-invasive marker of cellular health and membrane integrity. Whether PhA relates to muscular efficiency during exercise remains unclear.MethodsThis pilot study investigated the association between PhA and delta efficiency (DE), gross efficiency (GE), and exercise economy (EC) during submaximal cycling in 30 healthy young adults (15 females, mean age 21.4 ± 3.8 years). Whole-body and lower-body PhA were assessed using multifrequency BIA. Participants completed a graded cycling test (20–80 W) with energy expenditure determined via indirect calorimetry. DE, GE, and EC were calculated using standard procedures, and associations with PhA were examined using Pearson correlations, median-split group comparisons, and multivariable linear regression models adjusting for sex and fat-free mass.ResultsNeither whole-body nor lower-body PhA was significantly correlated with DE, GE, or EC (all p > 0.05). Group comparisons based on PhA medians showed no significant differences in performance indicators. The largest observed correlation was between whole-body PhA and GE (r = −0.32, p = 0.081). Regression models adjusting for sex and fat-free mass confirmed that PhA did not independently predict DE, GE, or EC.ConclusionsPhA did not predict submaximal cycling efficiency or economy in healthy young adults. These findings suggest that cellular health, as reflected by PhA, may not directly influence muscular energetics under steady-state conditions. Future studies with larger samples and mechanistic measurements are warranted to clarify this relationship.

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 10 min 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 ± 248 s vs. MCC90min 1554.8 ± 226.7 s, 2.83% performance improvement). Performance was significantly enhanced for trained (US 1496.6 ± 173.1 s vs. MCC90min 1466.8 ± 157.6 s) 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 ± 3.22 nmol. L−1 vs. MCC30min 15.80 ± 8.69 nmol. L−1, MCC90min 12.65 ± 4.84 nmol. L−1) and vanillic acid (US 25.14 ± 10.91 nmol.L−1 vs. MCC30min 153.07 ± 85.91 nmol. L−1, MCC90min 164.58 ± 59.06 nmol. 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 ∼90 min 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.

Purpose:To determine if time-efficient, high-resistance inspiratory muscle strength training (IMST), comprising 30 inhalation-resisted breaths per day, improves cardiorespiratory fitness, exercise tolerance, physical function and/or regional body composition in healthy midlife and older adults.Methods:We performed a double-blind, randomized, sham-controlled clinical trial (NCT03266510) testing 6 weeks of IMST (30 breaths/day, 6 days/week, 55%−75% maximal inspiratory pressure) versus low-resistance sham training (15% maximal inspiratory pressure) in healthy men and women aged 50–79 years. Subjects performed a graded treadmill exercise test to exhaustion, physical performance battery (e.g., handgrip strength, leg press), and body composition testing (dual x-ray absorptiometry) at baseline and after 6 weeks of training.Results:Thirty-five participants (17 women, 18 men) completed high-resistance IMST (n=17) or sham training (n=18). Cardiorespiratory fitness (V̇O2peak) was unchanged, but exercise tolerance, measured as treadmill exercise time during a graded exercise treadmill test, increased with IMST (baseline: 539±42s, end-intervention: 606±42s; p=0.01) but not sham training (baseline: 562±39s, end-intervention: 553±38s; p=0.69). IMST increased peak respiratory exchange ratio (baseline: 1.09±0.02, end-intervention: 1.13±0.02; p=0.012), peak ventilatory efficiency (baseline: 25.2±0.8, end-intervention: 24.6±0.8; p=0.036) and improved submaximal exercise economy (baseline: 23.5±1.1ml/kg/min, end-intervention: 22.1±1.1ml/kg/min; p<0.001); none of these factors were altered by sham training (all p>0.05). Changes in plasma acylcarnitines (targeted metabolomics analysis) were consistently positively correlated with changes in exercise tolerance following IMST but not sham training. IMST was associated with regional increases in thorax lean mass (+4.4%; p=0.06) and reductions in trunk fat mass (−4.8%; p=0.04); however, peripheral muscle strength, muscle power, dexterity and mobility were unchanged.Conclusions:These data suggest that high-resistance IMST is an effective, time-efficient lifestyle intervention for improving exercise tolerance in healthy midlife and older adults.

ObjectiveThis pilot study aimed to assess the efficacy of a 16-week at-home high-intensity interval training (HIIT) program among individuals with spinal cord injury (SCI).MethodsEight individuals (age: 47±11 (SD) years, 3 females) with SCI below the sixth thoracic vertebrae participated in a 16-week at-home HIIT program using an arm ergometer. Participants completed baseline graded exercise tests to determine target heart rate zones. HIIT was prescribed thrice per week. Each training session consisted of six one-minute bouts with a target heart rate ~80% heart rate reserve (HRR), interspersed with two minutes of recovery at ~30% HRR. A portable heart rate monitor and phone application provided visual feedback during training and allowed for measurements of adherence and compliance. Graded exercise tests were completed after 8 and 16 weeks of HIIT. Surveys were administered to assess participation, self-efficacy, and satisfaction.ResultsParticipants demonstrated a decrease in submaximal cardiac output (P=0.028) and an increase in exercise capacity (peak power output, P=0.027) following HIIT, indicative of improved exercise economy and maximal work capacity. An 87% adherence rate was achieved during the HIIT program. Participants reached a high intensity of 70% HRR or greater during ~80% of intervals. The recovery HRR target was reached during only ~35% of intervals. Self-reported metrics of satisfaction and self-efficacy with at-home HIIT scored moderate to high.ConclusionParticipants demonstrated an improvement in exercise economy and maximal work capacity following at-home HIIT. Additionally, participant adherence, compliance, satisfaction, and self-efficacy metrics suggest that at-home HIIT was easily implemented and enjoyable.

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.