Extracellular heat shock protein 70 (HSP70) acts as a damage-associated molecular pattern, or "danger signal" for the immune system. Acute prolonged exercise evokes various physiological stresses that can stimulate the release of extracellular HSP70. However, exercise-induced extracellular HSP70 responses are inconsistent in human studies. Therefore, the purpose of this meta-analysis and meta-regression was to systematically evaluate the effect of exercise on plasma HSP70 expression and to determine the exercise-associated factors contributing to plasma HSP70 response. Data were extracted from 26 experimental trials from 13 studies, including 154 participants, in which plasma HSP70 was measured before and after prolonged, continuous running or cycling exercise at a fixed intensity relative to V̇o2max. Meta-analysis was performed to determine the raw mean difference (MD) between post- and pre-exercise HSP70 concentration. Meta-regression was performed to establish the moderating effects of V̇o2max, exercise intensity, duration, modality, environmental temperature, humidity, and hypoxia on the plasma HSP70 response. There was a significant effect of exercise on plasma HSP70 concentration (MD = 0.73 ng·mL-1, 95% CI [0.13, 1.34], P = 0.02). Meta-regression explained ∼57.1% of variation in exercise-induced change in plasma HSP70 concentration (marginal R2 = 0.571). The V̇o2max (β = 0.51, 95% CI [0.03, 1.00]), exercise duration (β = 0.43, 95% CI [0.21, 0.65]), intensity (β = 0.40, 95% CI [0.08, 0.73]), and environmental temperature (β = 0.27, 95% CI [0.10, 0.43]) explained variation in the plasma HSP70 response. These data contribute to our understanding of the factors that modulate the plasma HSP70 response to acute prolonged exercise.

It is recommended that endurance athletes modulate their daily carbohydrate intake according to the demands of training, but there is limited evidence of how this is currently practiced by athletes during real-world, day-to-day training. The purpose of this observational study was to report the dietary intake of endurance athletes across a 12-week period with an emphasis on the relationship between training load and carbohydrate intake. Self-selected training and dietary intake were self-reported using a smartphone app by 46 endurance athletes (61% male) daily for 12 weeks, representing a total of 3,718 days of dietary assessments and 3,160 days of training. Fasted-state training was regularly performed by 65% of athletes and was more common in men (33.6% vs. 17.2% of training days, p = .023). Average daily carbohydrate intake for each athlete ranged from 1.2 to 7.2 g/kg (M = 3.9 ± 1.5). At the group level, significant correlations were found between mean daily carbohydrate intake and both percentage of training sessions performed in the fasted state (r = -.39, p = .008) and weekly training volume (r = .42, p = .004). Participant-level correlations between daily training load and carbohydrate intake ranged from -.42 to .83. Overall, athletes adjust daily carbohydrate intake based on exercise duration, but at the individual level, many athletes do not align carbohydrate intake with training load as recommended or do so with minimal adjustment.

BACKGROUND: Physical fitness is a key tenet of military organisations worldwide. Specifically, many consider aerobic fitness (AF) an essential physical attribute for ensuring optimal military performance and readiness. However, the intricate relationship between AF and various facets of military job performance necessitates comprehensive review to ascertain the appropriateness and effectiveness of its assessment. OBJECTIVE: This narrative review aims to describe the relationship between AF and factors influencing individual military performance and readiness, and explores the implications of the enforcement of in-service, generic AF test standards in military populations. METHODS: Databases (PubMed and Google Scholar) were searched for all relevant published peer-reviewed literature as at August 2023. RESULTS: Inconsistent associations were found between AF and outcomes influencing individual military performance (physical capabilities, cognitive capabilities, presenteeism and productivity, resilience, and technical/tactical capabilities) and readiness (mental health and wellbeing and physical health). Consequently, the level of AF needed for acceptable or optimal military performance remains uncertain. CONCLUSIONS: AF is a cornerstone of health and performance, yet linking generic AF test standards to job performance is complex, with multiple factors interacting to influence outcomes. From existing literatures, there does not appear to be a specific level of AF at, and/or above, which acceptable military performance is achieved. As such, the enforcement of and emphasis on in-service, pass/fail, generic AF test standards in military populations is questionable and requires thoughtful re-evaluation. Role/task-specific AF should be assessed through evidence-based PES and the use of generic AF tests limited to the monitoring and benchmarking of health-related fitness.

To assess relationships between heart rate (HR), ventilation (̇ V̇ E), and respiratory frequency (FR) decoupling and durability of the first ventilatory threshold (VT1), and the strength of practical models to predict power output at VT1 during prolonged exercise. Durability of VT1 was assessed via measurements of power output at VT1 before and after 2.5-h of initially moderate-intensity cycling in 51 trained cyclists, as part of four studies published elsewhere. In 12 of those participants, power output at VT1 was assessed every hour until task failure. For every assessment of power output at VT1, HR, FR, and V̇ ̇E was measured at fixed power outputs, and thus decoupling of these variables with power output was determined. Bivariate repeated-measures correlations (rrm) between decoupling and durability of VT1 were assessed. Multivariable models were created to predict power output at VT1 during prolonged exercise using generalised estimating equations. Negative correlations were observed between exercise-induced change in power output at VT1 and HR (rrm = −0.76, P < 0.001) and FR (rrm = −0.40, P = 0.013) decoupling, but not V̇ ̇E decoupling (rrm = −0.25, P = 0.136). The final prediction model, containing baseline VT1 and peak oxygen uptake, FR decoupling, and an interaction between HR decoupling and exercise duration, effectively predicted real-time VT1 (mean absolute error, 7.2 W; R2, 0.95). HR and/or FR decoupling during controlled training sessions may be a practically useful durability assessment. Our prediction models may be an effective means of improving within-session intensity regulation and training load monitoring.

Military personnel are required to operate in hot environments upon short notice. To preserve performance an elevated thermal tolerance could be maintained prior to deployment using heat acclimation (HA) followed by intermittent heat exposure (IHE). In a randomised manner, 19 participants completed 5 d of passive, post-exercise HA in either sauna or hot-water immersion (HWI) followed by 19 d of decay, or IHE every 2-3 days. A heat-stress test involving walking for 1 h in 33°C, 75% humidity in military dress was conducted before HA, after HA, and following the decay or IHE period. Following HA, performance was unaffected, while mean rectal temperature (↓0.3°C), and mean heart rate reduced (↓8 bpm). Following the decay period, performance reduced in the decay group (↓2.6 min) while no change was seen with IHE. IHE saw mean rectal temperature continued to decrease (↓0.1°C) while sweat rate increased (↑0.1 L.h-1), changes not seen in the decay group. These findings showed HA to induce beneficial thermoregulatory adaptations that could be enhanced by IHE in a manner that can be practicably implemented within groups that need to deploy into hot environments at short notice.

There is some evidence for temperature-dependent stimulation of mitochondrial biogenesis; however, the role of elevated muscle temperature during exercise in mitochondrial adaptation to training has not been studied in humans in vivo. The purpose of this study was to determine the role of elevating muscle temperature during exercise in temperate conditions through the application of mild, local heat stress on mitochondrial adaptations to endurance training. Eight endurance-trained males undertook 3 weeks of supervised cycling training, during which mild (~ 40 °C) heat stress was applied locally to the upper-leg musculature of one leg during all training sessions (HEAT), with the contralateral leg serving as the non-heated, exercising control (CON). Vastus lateralis microbiopsies were obtained from both legs before and after the training period. Training-induced increases in complex I (fold-change, 1.24 ± 0.33 vs. 1.01 ± 0.49, P = 0.029) and II (fold-change, 1.24 ± 0.33 vs. 1.01 ± 0.49, P = 0.029) activities were significantly larger in HEAT than CON. No significant effects of training, or interactions between local heat stress application and training, were observed for complex I–V or HSP70 protein expressions. Our data provides partial evidence to support the hypothesis that elevating local muscle temperature during exercise augments training-induced adaptations to mitochondrial enzyme activity.

Power output at the moderate-to-heavy-intensity transition decreases during prolonged exercise, and resilience to this has been termed ‘durability’. The purpose of this study was to assess the relationship between durability and the effect of prolonged exercise on severe-intensity performance, and explore intramuscular correlates of durability. On separate days, 13 well-trained cyclists and triathletes (V̇O2peak, 57.3 ± 4.8 mL kg−1 min−1; training volume, 12 ± 2.1 h week−1) undertook an incremental test and 5-min time trial (TT) to determine power output at the first ventilatory threshold (VT1) and severe-intensity performance, with and without 150-min of prior moderate-intensity cycling. A single resting vastus lateralis microbiopsy was obtained. Prolonged exercise reduced power output at VT1 (211 ± 40 vs. 198 ± 39 W, ∆ -13 ± 16 W, ∆ -6 ± 7

PURPOSE:The aim of this study was to determine if machine learning models could predict the perceived morning recovery status (AM PRS) and daily change in heart rate variability (HRV change) of endurance athletes based on training, dietary intake, sleep, HRV, and subjective well-being measures. METHODS:Self-selected nutrition intake, exercise training, sleep habits, HRV, and subjective well-being of 43 endurance athletes ranging from professional to recreationally trained were monitored daily for 12 weeks (3572 days of tracking). Global and individualized models were constructed using machine learning techniques, with the single best algorithm chosen for each model. The model performance was compared with a baseline intercept-only model. RESULTS:Prediction error (root mean square error [RMSE]) was lower than baseline for the group models (11.8 vs. 14.1 and 0.22 vs. 0.29 for AM PRS and HRV change, respectively). At the individual level, prediction accuracy outperformed the baseline model but varied greatly across participants (RMSE range 5.5-23.6 and 0.05-0.44 for AM PRS and HRV change, respectively). CONCLUSION:At the group level, daily recovery measures can be predicted based on commonly measured variables, with a small subset of variables providing most of the predictive power. However, at the individual level, the key variables may vary, and additional data may be needed to improve the prediction accuracy.

Exposure to environmental heat stress increases carbohydrate oxidation and extracellular heat shock protein 70 (HSP70) concentrations during endurance exercise at matched absolute, external work rates. However, a reduction in absolute work rate typically occurs when unacclimated endurance athletes train and/or compete in hot environments. We sought to determine the effect of environmental heat stress on carbohydrate oxidation rates and plasma HSP70 expression during exercise at matched heart rates (HR). Ten endurance-trained, male cyclists performed two experimental trials in an acute, randomised, counterbalanced cross-over design. Each trial involved a 90-min bout of cycling exercise at 95

Purpose Research findings are typically reported at the group level but applied to individuals. However, an emerging issue in sports science concerns nonergodicity—whereby group-level data cannot be generalized to individuals. The purpose of this study was to determine if the relationship between daily carbohydrate intake and perceived recovery status displays nonergodicity. Methods Fifty-five endurance athletes recorded daily measures of self-selected dietary intake, training, sleep, and subjective wellbeing for 12 weeks. We constructed linear models to measure the influence of daily carbohydrate intake on perceived recovery status while accounting for training load, sleep duration, sleep quality, and muscle soreness. Using linear model coefficients for carbohydrate intake we tested whether the distributions (mean and SD) differed at the group and individual levels (indicating nonergodicity). Additionally, a decision tree was created to explore factors that could provide an indication of an individual athlete’s relationship between carbohydrate intake and perceived recovery status. Results Mean values were not different between group- and individual-level analyses, but SDs at the individual level were ~2.4 times larger than at the group level, indicating nonergodicity. Model coefficients for carbohydrate intake were negative for three participants, positive for four participants, and non-significant for 37 participants. The κ value measuring accuracy of the decision tree was 0.52, indicating moderate prediction accuracy. Conclusion For most individuals, carbohydrate intake did not influence recovery status. However, the influence of dietary carbohydrate intake on daily recovery differs at the group and individual level. Therefore, practical recommendations should be based on individual-level analysis.

OBJECTIVES:To quantify energy availability (EA) in elite female rowers, determine its association with bone mineral density (BMD), and examine the ability of the low energy availability in females-questionnaire (LEAF-Q) and brief eating disorder in athletes-questionnaire (BEDA-Q) to distinguish between low and normal EA. DESIGN:Observational cross-sectional study. METHODS:Twenty-five elite female rowers participated in the study. EA was calculated by means of a 4-day food intake diary and analysis of training load. Low energy availability (LEA) was defined as EA <30 kCal * kg-1 * FFM-1 * day-1. Dual-energy X-ray absorptiometry (DXA) was used to assess fat free mass (FFM) and BMD Z-scores. LEA risk was assessed using the LEAF-Q and BEDA-Q. RESULTS:The mean EA was 23.2 ± 12.2 kCal * kg-1 * FFM-1 * day-1. Prevalence of LEA was 64 %. The mean BMD Z-score was 1.6 ± 0.6 (range: 0.7 to 2.9). Athletes with LEA had a significantly higher BEDA-Q score than the group with normal EA (mean 0.30 ± 0.17 vs. 0.09 ± 0.11, P < 0.05), but LEAF-Q score was not different between groups (mean 10.4 ± 4.6, 8.2 ± 4.5, P = 0.29). CONCLUSION:Low energy availability is common amongst elite female rowers in New Zealand and is positively correlated with higher scores on the BEDA-Q. Bone mineral density was normal irrespective of EA status.

Muscle glycogen state and carbohydrate (CHO) supplementation before and during exercise may impact responses to high-intensity interval training (HIIT). This study determined cardiorespiratory, substrate metabolism, muscle oxygenation, and performance when completing HIIT with or without CHO supplementation in a muscle glycogen depleted state. On two occasions, in a cross-over design, eight male cyclists performed a glycogen depletion protocol prior to HIIT during which either a 6% CHO drink (60 g.hr−1) or placebo (%CHO, PLA) was consumed. HIIT consisted of 5 × 2 min at 80% peak power output (PPO), 3 × 10-min bouts of steady-state (SS) cycling (50, 55, 60% PPO), and a time-to-exhaustion (TTE) test. There was no difference in SS $${\dot{\text{V}}\text{O}}_{{2}}$$ , HR, substrate oxidation and gross efficiency (GE %) between CHO and PLA conditions. A faster rate of muscle reoxygenation (%. s−1) existed in PLA after the 1st (Δ − 0.23 ± 0.22, d = 0.58, P < 0.05) and 3rd HIIT intervals (Δ − 0.34 ± 0.25, d = 1.02, P < 0.05). TTE was greater in CHO (7.1 ± 5.4 min) than PLA (2.5 ± 2.3 min, d = 0.98, P < 0.05). CHO consumption before and during exercise under reduced muscle glycogen conditions did not suppress fat oxidation, suggesting a strong regulatory role of muscle glycogen on substrate metabolism. However, CHO ingestion provided a performance benefit under intense exercise conditions commenced with reduced muscle glycogen. More research is needed to understand the significance of altered muscle oxygenation patterns during exercise.

To quantify the effects of prolonged cycling on the rate of ventilation ( V̇_E ), frequency of respiration (FR), and tidal volume (VT) associated with the moderate-to-heavy intensity transition. Fourteen endurance-trained cyclists and triathletes (one female) completed an assessment of the moderate-to-heavy intensity transition, determined as the first ventilatory threshold (VT1), before (PRE) and after (POST) two hours of moderate-intensity cycling. The power output, V̇_E , FR, and VT associated with VT1 were determined PRE and POST. As previously reported, power output at VT1 significantly decreased by 10 V̇_E associated with VT1 was unchanged from PRE to POST (72 ± 12 vs. 69 ± 13 L.min−1, ∆ − 3 ± 5 L.min−1, ∆ − 4 ± 8 V̇_E associated with VT1 was produced with increased FR (27.6 ± 5.8 vs. 31.9 ± 6.5 breaths.min−1, ∆ 4.3 ± 3.1 breaths.min−1, ∆ 16 ± 11 V̇_E remains stable. Real-time monitoring of V̇_E may be a useful means of assessing proximity to the moderate-to-heavy intensity transition during prolonged exercise and is worthy of further research.

Abstract To mitigate the effects of heat during operations in hot environments, military personnel will likely benefit from heat acclimation (HA) conducted prior to deployment. Using post-exercise, passive heating, 25 participants completed a 5 d HA regime in sauna (70 °C, 18% RH) or hot-water immersion (HWI) (40 °C) for ≤40 min, preceded and followed by a heat stress test (1-h walking at 5 km.h−1 in 33 °C, 77% RH in military uniform (20 kg) before an incremental ramp to exhaustion). Fifteen completed both regimes in a randomised, cross-over manner. While performance did not significantly improve (+14%, [-1, 29], p = .079), beneficial adaptations were observed for mean exercising core temperature (-0.2 °C, [-0.2, −0.2], p <.001), skin temperature (-0.2 °C, [-0.2, −0.2], p = 035) and heart rate (-8 bpm, [-6, −10], p<.001) in both conditions. Post-exercise, passive HA of either modality may benefit military units operating in the heat. Practitioner summary: Strategies are required to prevent health and performance impairments during military operations upon arrival in hot environments. Using a randomised, cross-over design, participants completed five-day passive, post-exercise heat acclimation using sauna or hot-water immersion. Both regimes elicited beneficial albeit modest heat adaptations. Abbreviations: HA: heat acclimation; HST: heat stress test; HWI: hot-water immersion; RH: relative humidity

This study quantified and compared the collision and non-collision match characteristics across age categories (i.e. U12, U14, U16, U18, Senior) for both amateur and elite playing standards from Tier 1 rugby union nations (i.e. England, South Africa, New Zealand). Two-hundred and one male matches (5911 min ball-in-play) were coded using computerised notational analysis, including 193,708 match characteristics (e.g. 83,688 collisions, 33,052 tackles, 13,299 rucks, 1006 mauls, 2681 scrums, 2923 lineouts, 44,879 passes, 5568 kicks). Generalised linear mixed models with post-hoc comparisons and cluster analysis compared the match characteristics by age category and playing standard. Overall significant differences (p < 0.001) between age category and playing standard were found for the frequency of match characteristics, and tackle and ruck activity. The frequency of characteristics increased with age category and playing standard except for scrums and tries that were the lowest at the senior level. For the tackle, the percentage of successful tackles, frequency of active shoulder, sequential and simultaneous tackles increased with age and playing standard. For ruck activity, the number of attackers and defenders were lower in U18 and senior than younger age categories. Cluster analysis demonstrated clear differences in all and collision match characteristics and activity by age category and playing standard. These findings provide the most comprehensive quantification and comparison of collision and non-collision activity in rugby union demonstrating increased frequency and type of collision activity with increasing age and playing standard. These findings have implications for policy to ensure the safe development of rugby union players throughout the world.

Several proteins are implicated in transmembrane fatty acid transport. The purpose of this study was to quantify the variation in fatty acid oxidation rates during exercise explained by skeletal muscle proteins involved in fatty acid transport. Seventeen endurance-trained males underwent a (i) fasted, incremental cycling test to estimate peak whole-body fatty acid oxidation rate (PFO), (ii) resting vastus lateralis microbiopsy, and (iii) 2 h of fed-state, moderate-intensity cycling to estimate whole-body fatty acid oxidation during fed-state exercise (FO). Bivariate correlations and stepwise linear regression models of PFO and FO during 0–30 min (early FO) and 90–120 min (late FO) of continuous cycling were constructed using muscle data. To assess the causal role of transmembrane fatty acid transport in fatty acid oxidation rates during exercise, we measured fatty acid oxidation during in vivo exercise and ex vivo contractions in wild-type and CD36 knock-out mice. We observed a novel, positive association between vastus lateralis FATP1 and PFO and replicated work reporting a positive association between FABPpm and PFO. The stepwise linear regression model of PFO retained CD36, FATP1, FATP4, and FABPpm, explaining 87

The three-minute all-out test (3MT), when performed on a laboratory ergometer in a linear mode, can be used to estimate the heavy–severe-intensity transition, or maximum metabolic steady state (MMSS), using the end-test power output. As the 3MT only requires accurate measurement of power output and time, it is possible the 3MT could be used in remote settings using personal equipment without supervision for quantification of MMSS. The aim of the present investigation was to determine the reliability and validity of remotely performed 3MTs (3MTR) for estimation of MMSS. Accordingly, 53 trained cyclists and triathletes were recruited to perform one familiarisation and two experimental 3MTR trials to determine its reliability. A sub-group (N = 10) was recruited to perform three-to-five 30 min laboratory-based constant-work rate trials following completion of one familiarisation and two experimental 3MTR trials. Expired gases were collected throughout constant-work rate trials and blood lactate concentration was measured at 10 and 30 min to determine the highest power output at which steady-state V̇O_2 (MMSS- V̇O_2 ) and blood lactate (MMSS-[La−]) were achieved. The 3MTR end-test power (EPremote) was reliable (coefficient of variation, 4.5 V̇O_2 , 241 ± 46 W, P = 0.0003; MMSS-[La−], 237 ± 47 W, P = 0.0003). This may have been due to failure to deplete the finite work capacity above MMSS during the 3MTR. These results suggest that the 3MTR should not be used to estimate MMSS in endurance-trained cyclists.

Completing selected training sessions with reduced glycogen availability is associated with greater signalling and improved muscle oxidative capacity, although it may impact the overall quality of the session. We examined the effects of low carbohydrate availability on high intensity exercise performance, running economy, critical speed, and substrate metabolism. On two occasions, nine male runners (V̇O2peak 60.3 ± 3.3 mL.kg-1.min-1) completed a glycogen depletion protocol involving 90-min at 75%vV̇O2peak followed by 10 × 1-min at 110% vV̇O2peak. This was followed either by high (HIGH) or low (LOW) carbohydrate intake (>6 g.kg-1.day-1 and <50 g.day-1, respectively) until completion of a performance protocol on day 2 consisting of a series of time-trials (TT) (50m to 3000m) and physiological assessments. There were no differences between LOW and HIGH for any TT distance (mean TT performance times for LOW and HIGH were: 3000m TT 651.7 ± 52.8s and 646.4 ± 52.5s, 1500 m TT 304.0 ± 20.2s and 304.2 ± 22.1s, 400 m TT 67.64 ± 4.2s and 67.3 ± 3.8s, 50 m TT 7.27 ± 0.44s and 7.25 ± 0.45s, respectively, P > 0.05), though some athletes performed better in LOW (n = 5). While fat oxidation in LOW was significantly greater than HIGH (Δ0.32 ± 0.14 g.min-1; P < 0.001 at 14 km.h-1 and Δ0.34 ± 0.12 g.min-1 at 16 km.h-1; P < 0.01), running economy did not differ between trials (P > 0.05). Acute manipulation of carbohydrate availability showed immediate effects on substrate metabolism evidenced by greater fat oxidation without changes in RE. Acute low carbohydrate availability did not affect high intensity running performance across a range of distances.Highlights Acute manipulation of muscle glycogen availability using an exercise and dietary manipulation protocol did not affect subsequent high intensity running performance across a range of running distances.Reduced muscle glycogen resulted in a marked increase in fat oxidation in low glycogen condition but no changes in running economy or critical speed.Individual factors should be considered when prescribing high intensity sessions with restricted carbohydrate availability.

Background Multiple factors influence substrate oxidation during exercise including exercise duration and intensity, sex, and dietary intake before and during exercise. However, the relative influence and interaction between these factors is unclear. Objectives Our aim was to investigate factors influencing the respiratory exchange ratio (RER) during continuous exercise and formulate multivariable regression models to determine which factors best explain RER during exercise, as well as their relative influence. Methods Data were extracted from 434 studies reporting RER during continuous cycling exercise. General linear mixed-effect models were used to determine relationships between RER and factors purported to influence RER (e.g., exercise duration and intensity, muscle glycogen, dietary intake, age, and sex), and to examine which factors influenced RER, with standardized coefficients used to assess their relative influence. Results The RER decreases with exercise duration, dietary fat intake, age, VO 2max , and percentage of type I muscle fibers, and increases with dietary carbohydrate intake, exercise intensity, male sex, and carbohydrate intake before and during exercise. The modelling could explain up to 59% of the variation in RER, and a model using exclusively easily modified factors (exercise duration and intensity, and dietary intake before and during exercise) could only explain 36% of the variation in RER. Variables with the largest effect on RER were sex, dietary intake, and exercise duration. Among the diet-related factors, daily fat and carbohydrate intake have a larger influence than carbohydrate ingestion during exercise. Conclusion Variability in RER during exercise cannot be fully accounted for by models incorporating a range of participant, diet, exercise, and physiological characteristics. To better understand what influences substrate oxidation during exercise further research is required on older subjects and females, and on other factors that could explain additional variability in RER.

Background Contemporary sports nutrition guidelines recognize that endurance athletes should periodize their daily carbohydrate (CHO) intake according to the demands of their training and competitive schedule. However, objective assessments of the dietary CHO periodization practices adopted by endurance athletes during prolonged training periods are not readily available. Objectives To objectively assess the magnitude of the CHO periodization practices adopted by endurance athletes via the formulation of a novel CHO Periodization Index (CPI). The CPI is proposed to represent a single metric to quantify how tightly an athlete’s CHO intake is matched with training load, the magnitude of adjustment, and how frequently these adjustments occur. Methods Self-selected training and dietary intake was reported daily by 55 endurance athletes (61.8% male) for 12 weeks (representing a total of 4,395 days of dietary assessments). Calculations were made for correlations between daily CHO intake and training load (product of session rating of perceived exertion and duration), CHO monotony (mean daily CHO intake divided by SD), CHO range (highest minus lowest single-day intake), and the CPI (correlation * range / monotony). Sub-group analysis was also performed to examine differences in CPI, frequency of fasted training sessions, and weekly training volume based on competitive level, habitual diet, and sex. Results Mean participant daily CHO intake was 3.9 ± 1.5 (range 1.2 to 7.2) g/kg, with the highest single-day intake being 17.6 g/kg. Mean CHO range was 6.6 ± 3.1 (range 2.0 to 15.2) g/kg. Carbohydrate monotony values ranged from 1.0 to 6.0. Pearson correlations between training load and daily CHO intake ranged from −0.34 to 0.87. Mean CPI was 1.0 ± 1.2 (range - 1.2 to 5.6) and was higher among the highest-level athletes. Conclusion Endurance athletes do not readily adjust daily CHO intake according to the demands of training. Furthermore, the CPI represents a promising tool that that can be used by researchers, coaches, and athletes to quantify CHO periodization practices and compare within and between individuals. Key Points ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement No sources of funding were used to assist in the preparation of this article. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: All study protocols and materials were approved by the Auckland University of Technology Ethics Committee (22/7). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes The R code used in this analysis is publicly available at (https://github.com/Jeffrothschild/CPI_code).