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Endurance exercise can disturb intestinal epithelial integrity, leading to increased systemic indicators of cell injury, hyperpermeability, and pathogenic translocation. However, the interaction between exercise, diet, and gastrointestinal disturbance still warrants exploration. This study examined whether a 6-day dietary intervention influenced perturbations to intestinal epithelial disruption in response to a 25-km race walk. Twenty-eight male race walkers adhered to a high carbohydrate (CHO)/energy diet (65% CHO, energy availability = 40 kcal·kg FFM−1·day−1) for 6 days prior to a Baseline 25-km race walk. Athletes were then split into three subgroups: high CHO/energy diet (n = 10); low-CHO, high-fat diet (LCHF: n = 8; <50 g/day CHO, energy availability = 40 kcal·kg FFM−1·day−1); and low energy availability (n = 10; 65% CHO, energy availability = 15 kcal·kg FFM−1·day−1) for a further 6-day dietary intervention period prior to a second 25-km race walk (Adaptation). During both trials, venous blood was collected pre-, post-, and 1 hr postexercise and analyzed for markers of intestinal epithelial disruption. Intestinal fatty acid-binding protein concentration was significantly higher (twofold increase) in response to exercise during Adaptation compared to Baseline in the LCHF group (p =.001). Similar findings were observed for soluble CD14 (p <.001) and lipopolysaccharide-binding protein (p =.003), where postexercise concentrations were higher (53% and 36%, respectively) during Adaptation than Baseline in LCHF. No differences in high CHO/energy diet or low energy availability were apparent for any blood markers assessed (p >.05). A short-term LCHF diet increased intestinal epithelial cell injury in response to a 25-km race walk. No effect of low energy availability on gastrointestinal injury or symptoms was observed. [ABSTRACT FROM AUTHOR]

Purpose: To examine the effects of a high-carbohydrate diet (HCHO), periodized-carbohydrate (CHO) diet (PCHO), and ketogenic low-CHO high-fat diet (LCHF) on training capacity. Methods: Elite male racewalkers completed 3 weeks of periodic training while adhering to their dietary intervention. Twenty-nine data sets were collected from 21 athletes. Each week, 6 mandatory training sessions were completed, with additional sessions performed at the athlete's discretion. Mandatory sessions included an interval session (10 × 1-km efforts on a 6-min cycle), tempo session (14 km with a 450-m elevation gain), 2 long walks (25–40 km), and 2 easy walks (8–12 km) where "sleep-low" and "train-low" dietary strategies were employed for PCHO. Racewalking speed, heart rate, rating of perceived exhaustion, and blood metabolites were collected around key sessions. Results: LCHF covered less total distance than HCHO and PCHO (P <.001); however, no differences in training load between groups were evident (P =.285). During the interval sessions, walking speed was slower in LCHF (P =.001), equating to a 2.8% and 5.6% faster speed in HCHO and PCHO, respectively. LCHF was also 3.2% slower in completing the tempo session than HCHO and PCHO (P =.001). Heart rate was higher (P =.002) and lactate concentrations were lower (P <.001) in LCHF compared to other groups, despite slower walking speeds during the interval session. No between-groups differences in rating of perceived exhaustion were evident (P =.077). Conclusion: Athletes adhering to an LCHF diet showed impaired training capacity relative to their high-CHO-supported counterparts, completing lower training volumes at slower speeds, with higher heart rates. [ABSTRACT FROM AUTHOR]

Purpose: To document a world-class race walking athlete's preparation for the 2019 International Association of Athletics Federations (IAAF) World Championships (Doha, Qatar), including periodized training, physiological data, cooling strategies and nutritional practices. Methods: Physiological data (VO2max, mL·kg−1·min−1; submaximal economy, mL·kg−1·min−1; and %VO2max), training volume (km) and intensity (min·km−1) were recorded (January–May 2019). Additional training strategies and interventions (altitude training, heat acclimation/acclimatization, cooling methods and pre- and during-race nutrition) were described (February–October 2019). Performances in IAAF-sanctioned 20 km races were also reported. Results: The athlete's highest VO2max result was 74.6 mL·kg−1·min−1, and his highest 4 mmol·L−1 walking speed was 15.7 km·h−1. The best submaximal economy measures (the lowest proportional oxygen use at 13 km·h−1) were 48.4 mL·kg−1·min−1 (65.2% VO2max). The best performance outcome was a bronze medal-winning performance at the 2019 IAAF World Championships (32°C; 77% RH). Six blocks of altitude training were performed (119 days). Five blocks of heat acclimatization training (127 days), one block of heat acclimation training (8 days) and two blocks of post-training passive heat sessions (16 days) were completed. Internal and external cooling strategies were used, and the athlete's nutritional intake focused on carbohydrate and fluid intake prior to and during races, pre-race supplementation with sodium bicarbonate using chronic and acute protocols, caffeine supplementation during races and pre-race hyperhydration. Conclusion: The strategies used by this elite athlete included repeated heat acclimation, heat acclimatization, passive heat exposure, hypoxic training and heat mitigation strategies. Similar strategies may provide benefit to elite athletes preparing for major international competitions in hot conditions. [ABSTRACT FROM AUTHOR]

Purpose: The effect of acetaminophen (ACT, also known as paracetamol) on endurance performance in hot and humid conditions has been shown previously in recreationally active populations. The aim of this study was to determine the effect of ACT on physiological and perceptual variables during steady-state and time-trial cycling performance of trained triathletes in hot and humid conditions. Methods: In a randomized, double-blind crossover design, 11 triathletes completed ∼60 minutes steady-state cycling at 63% peak power output followed by a time trial (7 kJ·kg body mass−1, ∼30 min) in hot and humid conditions (∼30°C, ∼69% relative humidity) 60 minutes after consuming either 20 mg·kg body mass−1 ACT or a color-matched placebo. Time-trial completion time, gastrointestinal temperature, skin temperature, thermal sensation, thermal comfort, rating of perceived exertion, and fluid balance were recorded throughout each session. Results: There was no difference in performance in the ACT trial compared with placebo (P =.086, d = 0.57), nor were there differences in gastrointestinal and skin temperature, thermal sensation and comfort, or fluid balance between trials. Conclusion: In conclusion, there was no effect of ACT (20 mg·kg body mass−1) ingestion on physiology, perception, and performance of trained triathletes in hot and humid conditions, and existing precooling and percooling strategies appear to be more appropriate for endurance cycling performance in the heat. [ABSTRACT FROM AUTHOR]

This study implemented a 2-week high carbohydrate (CHO) diet intended to maximize CHO oxidation rates and examined the iron-regulatory response to a 26-km race walking effort. Twenty international-level, male race walkers were assigned to either a novel high CHO diet (MAX = 10 g/kg body mass CHO daily) inclusive of gut-training strategies, or a moderate CHO control diet (CON = 6 g/kg body mass CHO daily) for a 2-week training period. The athletes completed a 26-km race walking test protocol before and after the dietary intervention. Venous blood samples were collected pre-, post-, and 3 hr postexercise and measured for serum ferritin, interleukin-6, and hepcidin-25 concentrations. Similar decreases in serum ferritin (17–23%) occurred postintervention in MAX and CON. At the baseline, CON had a greater postexercise increase in interleukin-6 levels after 26 km of walking (20.1-fold, 95% CI [9.2, 35.7]) compared with MAX (10.2-fold, 95% CI [3.7, 18.7]). A similar finding was evident for hepcidin levels 3 hr postexercise (CON = 10.8-fold, 95% CI [4.8, 21.2]; MAX = 8.8-fold, 95% CI [3.9, 16.4]). Postintervention, there were no substantial differences in the interleukin-6 response (CON = 13.6-fold, 95% CI [9.2, 20.5]; MAX = 11.2-fold, 95% CI [6.5, 21.3]) or hepcidin levels (CON = 7.1-fold, 95% CI [2.1, 15.4]; MAX = 6.3-fold, 95% CI [1.8, 14.6]) between the dietary groups. Higher resting serum ferritin (p =.004) and hotter trial ambient temperatures (p =.014) were associated with greater hepcidin levels 3 hr postexercise. Very high CHO diets employed by endurance athletes to increase CHO oxidation have little impact on iron regulation in elite athletes. It appears that variations in serum ferritin concentration and ambient temperature, rather than dietary CHO, are associated with increased hepcidin concentrations 3 hr postexercise. [ABSTRACT FROM AUTHOR]

Purpose: Traditional physiological testing and monitoring tools have restricted our ability to capture parameters that best relate to cycling performance under variable-intensity race demands. This study examined the validity of a 1-h variable cycling test (VCT) to discriminate between different-performance-level cyclists. Methods: Ten male national- and 13 club-level cyclists (body mass, 67 [9] and 79 [6] kg; peak power output, 359 [43] and 362 [21] W, respectively) completed a VO2max test and two 1-h VCT protocols on 3 separate occasions. The VCT consisted of 10 × 6-min segments containing prescribed (3.5 W·kg−1) and open-ended phases. The open-ended phases consisted of 4 × 30–40 s of "recovery," 3 × 10 s at "hard" intensity, and 3 × 6-s "sprint" with a final 10-s "all-out" effort. Results: Power output for the 6- and 10-s phases was moderately higher for the national- compared with club-level cyclists (mean [SD] 10.4 [2.0] vs 8.6 [1.6] W·kg−1, effect size; ±90% confidence limits = −0.87; ±0.65 and mean [SD] 7.5 [0.7] vs 6.2 [1.0] W·kg−1, effect size; ±90% confidence limits = −1.24; ±0.66, respectively). Power output for the final 10-s "all-out" sprint was 15.4 (1.5) for the national- versus 13.2 (1.9) W·kg−1 for club-level cyclists. Conclusion: The 1-h VCT can successfully differentiate repeat high-intensity effort performance between higher-caliber cyclists and their lower-performing counterparts. [ABSTRACT FROM AUTHOR]

Purpose: Anaerobic speed reserve (ASR), defined as the speed range from velocity associated with maximal oxygen uptake (vVO2max) to maximal sprint speed, has recently been shown to be an important tool for middle-distance coaches to meet event surge demands and inform on the complexity of athlete profiles. To enable field application of ASR. the relationship between gun-to-tape 1500-m average speed (1500v) and the vVO2max for the determination of lower landmark of the ASR was assessed in elite middle-distance runners. Methods: A total of 8 national and 4 international middle-distance runners completed a laboratorymeasured vVO2max assessment within 6 wk of a nonchampionship 1500-m gun-to-tape race. ASR was calculated using both laboratory-derived vVO2max (ASR-LAB) and 1500v (ASR-1500v), with maximal sprint speed measured using radar technology. Results: 1500v was on average +2.06 ± 1.03 km/h faster than vVO2max (moderate effect, very likely). ASR-LAB and ASR-1500v mean differences were -2.1 ± 1.5 km/h (large effect, very likely). 1500v showed an extremely large relationship with vVO2max, r = .90 ±.12 (most likely). Using this relationship, a linear-regression vV02max-estimation equation was derived as vVO2max (km/h) = (1500v [km/h] - 14.921 )/0.4266. Conclusions: A moderate difference was evident between 1500v and vVO2max in elite middle-distance runners. The present regression equation should be applied for an accurate field prediction of vV02max from 1500-m gun-to-tape races. These findings have strong practical implications for coaches lacking access to a sports physiology laboratory who seek to monitor and profile middle-distance runners. [ABSTRACT FROM AUTHOR]

Purpose: To determine whether combining training in heat with "Live High, Train Low" hypoxia (LHTL) further improves thermoregulatory and cardiovascular responses to a heat-tolerance test compared with independent heat training. Methods: A total of 25 trained runners (peak oxygen uptake = 64.1 [8.0] mL·min−1·kg−1) completed 3-wk training in 1 of 3 conditions: (1) heat training combined with "LHTL" hypoxia (H+H; FiO2 = 14.4% [3000 m], 13 h·d−1; train at <600 m, 33°C, 55% relative humidity [RH]), (2) heat training (HOT; live and train <600 m, 33°C, 55% RH), and (3) temperate training (CONT; live and train <600 m, 13°C, 55% RH). Heat adaptations were determined from a 45-min heat-response test (33°C, 55% RH, 65% velocity corresponding to the peak oxygen uptake) at baseline and immediately and 1 and 3 wk postexposure (baseline, post, 1 wkP, and 3 wkP, respectively). Core temperature, heart rate, sweat rate, sodium concentration, plasma volume, and perceptual responses were analyzed using magnitude-based inferences. Results: Submaximal heart rate (effect size [ES] = −0.60 [−0.89; −0.32]) and core temperature (ES = −0.55 [−0.99; −0.10]) were reduced in HOT until 1 wkP. Sweat rate (ES = 0.36 [0.12; 0.59]) and sweat sodium concentration (ES = −0.82 [−1.48; −0.16]) were, respectively, increased and decreased until 3 wkP in HOT. Submaximal heart rate (ES = −0.38 [−0.85; 0.08]) was likely reduced in H+H at 3 wkP, whereas CONT had unclear physiological changes. Perceived exertion and thermal sensation were reduced across all groups. Conclusions: Despite greater physiological stress from combined heat training and "LHTL" hypoxia, thermoregulatory adaptations are limited in comparison with independent heat training. The combined stimuli provide no additional physiological benefit during exercise in hot environments. [ABSTRACT FROM AUTHOR]

Purpose: To determine the effect of altitude training at 1600 and 1800 m on sea-level (SL) performance in national-level runners. Methods: After 3 wk of SL training, 24 runners completed a 3-wk sojourn at 1600 m (ALT1600, n = 8), 1800 m (ALT1800, n = 9), or SL (CON, n = 7), followed by up to 11 wk of SL racing. Race performance was measured at SL during the lead-in period and repeatedly postintervention. Training volume (in kilometers) and load (session rating of perceived exertion) were calculated for all sessions. Hemoglobin mass was measured via CO rebreathing. Between-groups differences were evaluated using effect sizes (Hedges g). Results: Performance improved in both ALT1600 (mean [SD] 1.5% [0.9%]) and ALT1800 (1.6% [1.3%]) compared with CON (0.4% [1.7%]); g = 0.83 (90% confidence limits −0.10, 1.66) and 0.81 (−0.09, 1.62), respectively. Season-best performances occurred 5 to 71 d postaltitude in ALT1600/1800. There were large increases in training load from lead-in to intervention in ALT1600 (48% [32%]) and ALT1800 (60% [31%]) compared with CON (18% [20%]); g = 1.24 (0.24, 2.08) and 1.69 (0.65, 2.55), respectively. Hemoglobin mass increased in ALT1600 and ALT1800 (∼4%) but not CON. Conclusions: Larger improvements in performance after altitude training may be due to the greater overall load of training in hypoxia compared with normoxia, combined with a hypoxia-mediated increase in hemoglobin mass. A wide time frame for peak performances suggests that the optimal window to race postaltitude is individual, and factors other than altitude exposure per se may be important. [ABSTRACT FROM AUTHOR]

Purpose: To determine the effect of training at 2100-m natural altitude on running speed (RS) during training sessions over a range of intensities relevant to middle-distance running performance. Methods: In an observational study, 19 elite middle-distance runners (mean ± SD age 25 ± 5 y, VO2max, 71 ± 5 mL ⋅ kg-1 ⋅ min-1) completed either 4-6 wk of sea-level training (CON, n = 7) or a 4- to 5-wk natural altitude-training camp living at 2100 m and training at 1400-2700 m (ALT, n = 12) after a period of sea-level training. Each training session was recorded on a GPS watch, and athletes also provided a score for session rating of perceived exertion (sRPE). Training sessions were grouped according to duration and intensity. RS (km/h) and sRPE from matched training sessions completed at sea level and 2100 m were compared within ALT, with sessions completed at sea level in CON describing normal variation. Results: In ALT, RS was reduced at altitude compared with sea level, with the greatest decrements observed during threshold- and VO2 max-intensity sessions (5.8% and 3.6%, respectively). Velocity of low-intensity and race-pace sessions completed at a lower altitude (1400 m) and/or with additional recovery was maintained in ALT, though at a significantly greater sRPE (P = .04 and .05, respectively). There was no change in velocity or sRPE at any intensity in CON. Conclusion: RS in elite middle-distance athletes is adversely affected at 2100-m natural altitude, with levels of impairment dependent on the intensity of training. Maintenance of RS at certain intensities while training at altitude can result in a higher perceived exertion. [ABSTRACT FROM AUTHOR]

High altitude exposure can increase resting metabolic rate (RMR) and induce weight loss in obese populations, but there is a lack of research regarding RMR in athletes at moderate elevations common to endurance training camps. The present study aimed to determine whether 4 weeks of classical altitude training affects RMR in middle-distance runners. Ten highly trained athletes were recruited for 4 weeks of endurance training undertaking identical programs at either 2200m in Flagstaff, Arizona (ALT, n = 5) or 600m in Canberra, Australia (CON, n = 5). RMR, anthropometry, energy intake, and hemoglobin mass (Hbmass) were assessed pre- and posttraining. Weekly run distance during the training block was: ALT 96.8 ± 18.3km; CON 103.1 ± 5.6km. A significant interaction for Time*Group was observed for absolute (kJ.day-1) (F-statistic, p-value: F(1,8)=13.890, p = .01) and relative RMR (F(1,8)=653.453, p = .003) POST-training. No significant changes in anthropometry were observed in either group. Energy intake was unchanged (mean ± SD of difference, ALT: 195 ± 3921kJ, p = .25; CON: 836 ± 7535kJ, p = .75). A significant main effect for time was demonstrated for total Hbmass (g) (F(1,8)=13.380, p = .01), but no significant interactions were observed for either variable [Total Hbmass (g): F(1,8)=1.706, p = .23; Relative Hbmass (g⋅kg-1): F(1,8)=0.609, p = .46]. These novel findings have important practical application to endurance athletes routinely training at moderate altitude, and those seeking to optimize energy management without compromising training adaptation. Altitude exposure may increase RMR and enhance training adaptation,. During training camps at moderate altitude, an increased energy intake is likely required to support an increased RMR and provide sufficient energy for training and performance. [ABSTRACT FROM AUTHOR]

CONTEXT: Road cycle racing is characterized by significant variability in exercise intensity. Existing protocols attempting to model this aspect display inadequate variation in power output. Furthermore, the reliability of protocols representative of road cycle racing is not well known. There are also minimal data regarding the physiological parameters that best predict performance during variable-power cycling. PURPOSE: To determine the reliability of mean power output during a new test of variable-power cycling and establish the relationship between physiological attributes typically measured during an incremental exercise test and performance during the variable-power cycling test (VCT). METHODS: Fifteen trained male cyclists (mean ± SD age 33 ± 6.5 y, VO2max 57.9 ± 4.8 mL • kg-1 • min-1) performed an incremental exercise test to exhaustion for determination of physiological attributes, 2 VCTs (plus familiarization), and a 30-km time trial. The VCT was modeled on data from elite men's road racing and included significant variation in power output. RESULTS: Mean power output during the VCT showed good reliability (r = .92, CV% = 1.98). Relative power during the self-paced sections of the VCT was most correlated with maximal aerobic power (r = .79) and power at the second ventilatory threshold (r = .69). Blood lactate concentration showed poor reliability between trials (CV% = 13.93%). CONCLUSIONS: This study has demonstrated a new reliable protocol simulating the stochastic nature of road cycling races. Further research is needed to determine which factors predict performance during variable-power cycling and the validity of the test in monitoring longitudinal changes in cycling performance. [ABSTRACT FROM AUTHOR]

Key points: Brief (5–6 days) adaptation to a low carbohydrate high fat diet in elite athletes increased exercise fat oxidation to rates previously observed with medium (3–4 weeks) or chronic (>12 months) adherence to this diet, with metabolic changes being washed out in a similar time frame.Increased fat utilisation during exercise was associated with a 5–8% increase in oxygen cost at speeds related to Olympic Programme races.Acute restoration of endogenous carbohydrate (CHO) availability (24 h high CHO diet, pre‐race CHO) only partially restored substrate utilisation during a race warm‐up. Fat oxidation continued to be elevated above baseline values although it was lower than achieved by 5–6 days' keto adaptation; CHO oxidation only reached 61% and 78% of values previously seen at exercise intensities related to race events.Acute restoration of CHO availability failed to overturn the impairment of high‐intensity endurance performance previously associated with low carbohydrate high fat adaptation, potentially due to the blunted capacity for CHO oxidation. We investigated substrate utilisation during exercise after brief (5–6 days) adaptation to a ketogenic low‐carbohydrate (CHO), high‐fat (LCHF) diet and similar washout period. Thirteen world‐class male race walkers completed economy testing, 25 km training and a 10,000 m race (Baseline), with high CHO availability (HCHO), repeating this (Adaptation) after 5–6 days' LCHF (n = 7; CHO: <50 g day−1, protein: 2.2 g kg−1 day−1; 80% fat) or HCHO (n = 6; CHO: 9.7 g kg−1 day−1; protein: 2.2 g kg−1 day−1) diet. An Adaptation race was undertaken after 24 h HCHO and pre‐race CHO (2 g kg−1) diet, identical to the Baseline race. Substantial (>200%) increases in exercise fat oxidation occurred in the LCHF Adaptation economy and 25 km tests, reaching mean rates of ∼1.43 g min−1. However, relative V̇O2 (ml min−1 kg−1) was higher (P < 0.0001), by ∼8% and 5% at speeds related to 50 km and 20 km events. During Adaptation race warm‐up in the LCHF group, rates of fat and CHO oxidation at these speeds were decreased and increased, respectively (P < 0.001), compared with the previous day, but were not restored to Baseline values. Performance changes differed between groups (P = 0.009), with all HCHO athletes improving in the Adaptation race (5.7 (5.6)%), while 6/7 LCHF athletes were slower (2.2 (3.4)%). Substrate utilisation returned to Baseline values after 5–6 days of HCHO diet. In summary, robust changes in exercise substrate use occurred in 5–6 days of extreme changes in CHO intake. However, adaptation to a LCHF diet plus acute restoration of endogenous CHO availability failed to restore high‐intensity endurance performance, with CHO oxidation rates remaining blunted. Key points: Brief (5–6 days) adaptation to a low carbohydrate high fat diet in elite athletes increased exercise fat oxidation to rates previously observed with medium (3–4 weeks) or chronic (>12 months) adherence to this diet, with metabolic changes being washed out in a similar time frame.Increased fat utilisation during exercise was associated with a 5–8% increase in oxygen cost at speeds related to Olympic Programme races.Acute restoration of endogenous carbohydrate (CHO) availability (24 h high CHO diet, pre‐race CHO) only partially restored substrate utilisation during a race warm‐up. Fat oxidation continued to be elevated above baseline values although it was lower than achieved by 5–6 days' keto adaptation; CHO oxidation only reached 61% and 78% of values previously seen at exercise intensities related to race events.Acute restoration of CHO availability failed to overturn the impairment of high‐intensity endurance performance previously associated with low carbohydrate high fat adaptation, potentially due to the blunted capacity for CHO oxidation. [ABSTRACT FROM AUTHOR]

Carbohydrate (CHO) availability could alter mucosal immune responses to exercise. This study compared the effect of three dietary approaches to CHO availability on resting and post-exercise s-IgA levels. Elite race walkers (n = 26) adhered to a high CHO diet (HCHO), periodised CHO availability (PCHO) or a low CHO/high fat diet (LCHF) for 3 weeks while completing an intensified training program. HCHO and PCHO groups consumed 8.0-8.5 g.kg−1 CHO daily, with timing of ingestion manipulated to alter CHO availability around key training sessions. The LCHF diet comprised 80% fat and restricted CHO to < 50 g.day−1. A race walk test protocol (19 km females, 25 km males) was completed at baseline, after adaptation, and following CHO restoration. On each occasion, saliva samples were obtained pre- and post-exercise to quantify s-IgA levels. Resting s-IgA secretion rate substantially increased ~ two-fold post-intervention in all groups (HCHO: 2.2 ± 2.2, PCHO: 2.8 ± 3.2, LCHF: 1.6 ± 1.6; fold-change± 95% confidence limits), however, no substantial differences between dietary treatments were evident. Post-exercise, substantial 20-130% increases in s-IgA concentration and 43-64% reductions in flow rate occurred in all dietary treatments, with trivial differences evident between groups. It appears that high volume training overrides any effect of manipulating CHO availability on mucosal immunity in elite athletes. [ABSTRACT FROM AUTHOR]

Although short (up to 3 days) exposure to major shifts in macronutrient intake appears to alter acid-base status, the effects of sustained (>1 week) interventions in elite athletes has not been determined. Using a non-randomized, parallel design, we examined the effect of adaptations to 21 days of a ketogenic low carbohydrate high fat (LCHF) or periodized carbohydrate (PCHO) diet on pre- and post-exercise blood pH, and concentrations of bicarbonate [HCO3-] and lactate [La-] in comparison to a high carbohydrate (HCHO) control. Twenty-four (17 male and 7 female) elite-level race walkers completed 21 days of either LCHF (n = 9), PCHO (n = 7), or HCHO (n = 8) under controlled diet and training conditions. At baseline and post-intervention, blood pH, blood [HCO3-], and blood [La-] were measured before and after a graded exercise test. Net endogenous acid production (NEAP) over the previous 48-72 h was also calculated from monitored dietary intake. LCHF was not associated with significant differences in blood pH, [HCO3-], or [La-], compared with the HCHO diet pre- or post-exercise, despite a significantly higher NEAP (mEq⋅day-1) (95% CI = (10.44; 36.04)). Our results indicate that chronic dietary interventions are unlikely to influence acid-base status in elite athletes, which may be due to pre-existing training adaptations, such as an enhanced buffering capacity, or the actions of respiratory and renal pathways, which have a greater influence on regulation of acid-base status than nutritional intake. [ABSTRACT FROM AUTHOR]