Three portable blood lactate analysers, Lactate Pro (LP), Lactate Scout (LS) and Lactate Plus (L
+
), were evaluated. Analyser reliability and accuracy was assessed. For reliability, intra- and ...inter-analyser comparisons demonstrated that the LP (intra-TE = 0.5 mM, inter-TE = 0.4 mM) and L
+
(intra-TE = 0.4, inter-TE = 0.4 mM) displayed greater overall reliability than the LS (intra-TE = 1.0, inter-TE = 0.8 mM). At BLa < 4.0 mM, the LP (intra-TE = 0.1 mM) demonstrated greater reliability than the LS (intra-TE = 0.5 mM) and L
+
(intra-TE = 0.4 mM). At BLa > 8.0 mM, the LP (intra-TE = 0.5 mM, inter-TE = 0.4 mM) and L
+
(intra- and inter-TE = 0.4 mM) displayed greater reliability than the LS (intra-TE = 1.1 mM, inter-TE = 0.9 mM). For accuracy, the L
+
(SEE = 0.6 mM) compared more favourably to the LP than the LS (SEE = 1.1 mM). At BLa ~1.0–18.0 mM, the LS produced values that were up to 0.9 mM higher than the LP; the L
+
produced BLa that were within ±0.1 mM. All portable analysers tended to under-read the ABL 700 analyser. The suitability of the LP and L
+
as accurate analysers is supported by strong correlations (
r
= 0.91 and
r
= 0.94) and limits of agreement ≤2.1 mM. This study showed that the LP and L
+
, compared well to each other, displayed good reliability and accuracy when compared to a laboratory-based analyser. Although the LS also displayed relatively good reliability, it was not as reliable or accurate as the LP or L
+
.
Key points
Three weeks of intensified training and mild energy deficit in elite race walkers increases peak aerobic capacity independent of dietary support.
Adaptation to a ketogenic low ...carbohydrate, high fat (LCHF) diet markedly increases rates of whole‐body fat oxidation during exercise in race walkers over a range of exercise intensities.
The increased rates of fat oxidation result in reduced economy (increased oxygen demand for a given speed) at velocities that translate to real‐life race performance in elite race walkers.
In contrast to training with diets providing chronic or periodised high carbohydrate availability, adaptation to an LCHF diet impairs performance in elite endurance athletes despite a significant improvement in peak aerobic capacity.
We investigated the effects of adaptation to a ketogenic low carbohydrate (CHO), high fat diet (LCHF) during 3 weeks of intensified training on metabolism and performance of world‐class endurance athletes. We controlled three isoenergetic diets in elite race walkers: high CHO availability (g kg−1 day−1: 8.6 CHO, 2.1 protein, 1.2 fat) consumed before, during and after training (HCHO, n = 9); identical macronutrient intake, periodised within or between days to alternate between low and high CHO availability (PCHO, n = 10); LCHF (< 50 g day−1 CHO; 78% energy as fat; 2.1 g kg−1 day−1 protein; LCHF, n = 10). Post‐intervention, V̇O2 peak during race walking increased in all groups (P < 0.001, 90% CI: 2.55, 5.20%). LCHF was associated with markedly increased rates of whole‐body fat oxidation, attaining peak rates of 1.57 ± 0.32 g min−1 during 2 h of walking at ∼80% V̇O2 peak . However, LCHF also increased the oxygen (O2) cost of race walking at velocities relevant to real‐life race performance: O2 uptake (expressed as a percentage of new V̇O2 peak ) at a speed approximating 20 km race pace was reduced in HCHO and PCHO (90% CI: −7.047, −2.55 and −5.18, −0.86, respectively), but was maintained at pre‐intervention levels in LCHF. HCHO and PCHO groups improved times for 10 km race walk: 6.6% (90% CI: 4.1, 9.1%) and 5.3% (3.4, 7.2%), with no improvement (−1.6% (−8.5, 5.3%)) for the LCHF group. In contrast to training with diets providing chronic or periodised high‐CHO availability, and despite a significant improvement in V̇O2 peak , adaptation to the topical LCHF diet negated performance benefits in elite endurance athletes, in part due to reduced exercise economy.
Key points
Three weeks of intensified training and mild energy deficit in elite race walkers increases peak aerobic capacity independent of dietary support.
Adaptation to a ketogenic low carbohydrate, high fat (LCHF) diet markedly increases rates of whole‐body fat oxidation during exercise in race walkers over a range of exercise intensities.
The increased rates of fat oxidation result in reduced economy (increased oxygen demand for a given speed) at velocities that translate to real‐life race performance in elite race walkers.
In contrast to training with diets providing chronic or periodised high carbohydrate availability, adaptation to an LCHF diet impairs performance in elite endurance athletes despite a significant improvement in peak aerobic capacity.
Introduction We repeated our study of intensified training on a ketogenic low-carbohydrate (CHO), high-fat diet (LCHF) in world-class endurance athletes, with further investigation of a "carryover" ...effect on performance after restoring CHO availability in comparison to high or periodised CHO diets. Methods After Baseline testing (10,000 m IAAF-sanctioned race, aerobic capacity and submaximal walking economy) elite male and female race walkers undertook 25 d supervised training and repeat testing (Adapt) on energy-matched diets: High CHO availability (8.6 gâkg.sup.-1 âd.sup.-1 CHO, 2.1 gâkg.sup.-1 âd.sup.-1 protein; 1.2 gâkg.sup.-1 âd.sup.-1 fat) including CHO before/during/after workouts (HCHO, n = 8): similar macronutrient intake periodised within/between days to manipulate low and high CHO availability at various workouts (PCHO, n = 8); and LCHF (<50 gâd.sup.-1 CHO; 78% energy as fat; 2.1 gâkg.sup.-1 âd.sup.-1 protein; n = 10). After Adapt, all athletes resumed HCHO for 2.5 wk before a cohort (n = 19) completed a 20 km race. Results All groups increased VO.sub.2 peak (mlâkg.sup.-1 âmin.sup.-1) at Adapt (p = 0.02, 95%CI: 0.35-2.74). LCHF markedly increased whole-body fat oxidation (from 0.6 gâmin.sup.-1 to 1.3 gâmin.sup.-1 ), but also the oxygen cost of walking at race-relevant velocities. Differences in 10,000 m performance were clear and meaningful: HCHO improved by 4.8% or 134 s (95% CI: 207 to 62 s; p < 0.001), with a trend for a faster time (2.2%, 61 s -18 to +144 s; p = 0.09) in PCHO. LCHF were slower by 2.3%, -86 s (-18 to -144 s; p < 0.001), with no evidence of superior "rebound" performance over 20 km after 2.5 wk of HCHO restoration and taper. Conclusion Our previous findings of impaired exercise economy and performance of sustained high-intensity race walking following keto-adaptation in elite competitors were repeated. Furthermore, there was no detectable benefit from undertaking an LCHF intervention as a periodised strategy before a 2.5-wk race preparation/taper with high CHO availability. Trial registration Australia New Zealand Clinical Trial Registry: ACTRN12619000794101.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Key points
•
A single bolus of ∼20 g of protein after a bout of resistance exercise provides a maximal anabolic stimulus during the early post‐exercise recovery period (∼5 h), but the effect of ...various protein feeding strategies on skeletal muscle protein synthesis during an extended recovery period (12 h) is unknown.
•
We compared three different patterns of ingestion of 80 g of protein during 12 h recovery after resistance exercise and the associated anabolic response in human skeletal muscle. Protein was ingested in 10, 20 or 40 g feedings using a pulsed, intermediate or bolus ingestion regimen, respectively.
•
Our results indicate that repeated ingestion of 20 g of protein was superior for stimulating muscle protein synthesis during the 12 h experimental period.
•
The three dietary treatments induced differential phosphorylation of signalling proteins and changes in mRNA abundance.
•
This study shows that the distribution of protein intake is an important variable to promote attainment and maintenance of peak muscle mass.
Quantity and timing of protein ingestion are major factors regulating myofibrillar protein synthesis (MPS). However, the effect of specific ingestion patterns on MPS throughout a 12 h period is unknown. We determined how different distributions of protein feeding during 12 h recovery after resistance exercise affects anabolic responses in skeletal muscle. Twenty‐four healthy trained males were assigned to three groups (n= 8/group) and undertook a bout of resistance exercise followed by ingestion of 80 g of whey protein throughout 12 h recovery in one of the following protocols: 8 × 10 g every 1.5 h (PULSE); 4 × 20 g every 3 h (intermediate: INT); or 2 × 40 g every 6 h (BOLUS). Muscle biopsies were obtained at rest and after 1, 4, 6, 7 and 12 h post exercise. Resting and post‐exercise MPS (l‐ring‐13C6 phenylalanine), and muscle mRNA abundance and cell signalling were assessed. All ingestion protocols increased MPS above rest throughout 1–12 h recovery (88–148%, P < 0.02), but INT elicited greater MPS than PULSE and BOLUS (31–48%, P < 0.02). In general signalling showed a BOLUS>INT>PULSE hierarchy in magnitude of phosphorylation. MuRF‐1 and SLC38A2 mRNA were differentially expressed with BOLUS. In conclusion, 20 g of whey protein consumed every 3 h was superior to either PULSE or BOLUS feeding patterns for stimulating MPS throughout the day. This study provides novel information on the effect of modulating the distribution of protein intake on anabolic responses in skeletal muscle and has the potential to maximize outcomes of resistance training for attaining peak muscle mass.
We investigated the effect of pre- "race" ingestion of a 1,3-butanediol acetoacetate diester on blood ketone concentration, substrate metabolism and performance of a cycling time trial (TT) in ...professional cyclists. In a randomized cross-over design, 10 elite male cyclists completed a ~31 km laboratory-based TT on a cycling ergometer programmed to simulate the 2017 World Road Cycling Championships course. Cyclists consumed a standardized meal 2 g/kg body mass (BM) carbohydrate (CHO) the evening prior to a trial day and a CHO breakfast (2 g/kg BM CHO) with 200 mg caffeine on the morning of a trial day. Cyclists were randomized to consume either the ketone diester (2 × 250 mg/kg) or a placebo drink, followed immediately by 200 mL diet cola, given ~ 30 min before and immediately prior to commencing a 20 min incremental warm-up. Blood samples were collected prior to and during the warm-up, pre- and post- TT and at regular intervals after the TT. Urine samples were collected pre- and post- warm-up, immediately post TT and 60 min post TT. Pre-exercise ingestion of the diester resulted in a 2 ± 1% impairment in TT performance that was associated with gut discomfort and higher perception of effort. Serum β-hydroxybutyrate, serum acetoacetate, and urine ketone concentrations increased from rest following ketone ingestion and were higher than placebo throughout the trial. Ketone ingestion induces hyperketonemia in elite professional cyclists when in a carbohydrate fed state, and impairs performance of a cycling TT lasting ~50 min.
We investigated extreme changes in diet patterns on the gut microbiota of elite race walkers undertaking intensified training and its possible links with athlete performance. Numerous studies with ...sedentary subjects have shown that diet and/or exercise can exert strong selective pressures on the gut microbiota. Similar studies with elite athletes are relatively scant, despite the recognition that diet is an important contributor to sports performance. In this study, stool samples were collected from the cohort at the beginning (baseline; BL) and end (post-treatment; PT) of a three-week intensified training program during which athletes were assigned to a High Carbohydrate (HCHO), Periodised Carbohydrate (PCHO) or ketogenic Low Carbohydrate High Fat (LCHF) diet (post treatment). Microbial community profiles were determined by 16S rRNA gene amplicon sequencing. The microbiota profiles at BL could be separated into distinct "enterotypes," with either a
or
dominated enterotype. While enterotypes were relatively stable and remained evident post treatment, the LCHF diet resulted in a greater relative abundance of
and
and a reduction of
Significant negative correlations were observed between
and fat oxidation and between
and economy test following LCHF intervention.
l-menthol (menthol) is an organic compound derived from peppermint which imparts a refreshing mint flavor and aroma to oral hygiene products, chewing gum, and topical analgesics. Menthol has been ...identified as a non-thermal sensory cooling strategy for athletes when ingested or mouth-rinsed during exercise in hot environments. Therefore, sports nutrition products delivering a controlled concentration of menthol could be beneficial for athletes exercising in the heat. We sought to test the performance and perceptual outcomes of a novel menthol energy gel during treadmill running in the heat (33 °C, 49% RH). Fourteen trained runners (mean ± SD; age: 31 ± 6 years, VO
: 56.5 ± 10.1 mL·kg
·min
, BMI: 23.2 ± 2.4 kg/m
; six female) participated in a randomized, crossover, double-blind, and placebo-controlled study. A menthol-enhanced energy gel (0.5% concentration; MEN) or flavor-matched placebo (PLA) was ingested 5 min before and again at 20 and 40 min of a 40 min treadmill exercise preload at 60% VO
, followed by a 20 min self-paced time trial. The total distance, vertical distance, perceptual measures (thermal comfort, thermal sensation, rating of perceived exertion, and affect), and cognitive performance via computerized neurocognitive assessment were measured. No difference between 20 min self-paced time trial total distance (MEN: 4.22 ± 0.54 km, PLA: 4.22 ± 0.55 km,
= 0.867), vertical distance (MEN: 49.2 ± 24.6 m, PLA: 44.4 ± 11.4 m,
= 0.516), or any perceptual measures was observed (all
> 0.05). Cognitive performance was not different between the trials (all
> 0.05). These results suggest that a menthol energy gel is not superior to a non-menthol gel in terms of performance or perception during treadmill running in the heat. More research is needed to confirm whether these findings translate to ecologically valid settings, including outdoor exercise in ambient heat and during competition.
To develop evidence-informed, expert consensus research diagnostic criteria for traumatic encephalopathy syndrome (TES), the clinical disorder associated with neuropathologically diagnosed chronic ...traumatic encephalopathy (CTE).
A panel of 20 expert clinician-scientists in neurology, neuropsychology, psychiatry, neurosurgery, and physical medicine and rehabilitation, from 11 academic institutions, participated in a modified Delphi procedure to achieve consensus, initiated at the First National Institute of Neurological Disorders and Stroke Consensus Workshop to Define the Diagnostic Criteria for TES
April, 2019. Before consensus, panelists reviewed evidence from all published cases of CTE with neuropathologic confirmation, and they examined the predictive validity data on clinical features in relation to CTE pathology from a large clinicopathologic study (n = 298).
Consensus was achieved in 4 rounds of the Delphi procedure. Diagnosis of TES requires (1) substantial exposure to repetitive head impacts (RHIs) from contact sports, military service, or other causes; (2) core clinical features of cognitive impairment (in episodic memory and/or executive functioning) and/or neurobehavioral dysregulation; (3) a progressive course; and (4) that the clinical features are not fully accounted for by any other neurologic, psychiatric, or medical conditions. For those meeting criteria for TES, functional dependence is graded on 5 levels, ranging from independent to severe dementia. A provisional level of certainty for CTE pathology is determined based on specific RHI exposure thresholds, core clinical features, functional status, and additional supportive features, including delayed onset, motor signs, and psychiatric features.
New consensus diagnostic criteria for TES were developed with a primary goal of facilitating future CTE research. These criteria will be revised as updated clinical and pathologic information and in vivo biomarkers become available.
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.
Purpose
The extent to which hepcidin regulation after acute bouts of exercise is influenced by baseline (resting) concentrations of key iron parameters remains uncertain. This investigation explored ...the influence of selected iron parameters and 25-km race walk time on 3-h post-exercise hepcidin-25 levels in international-level race walkers.
Methods
Twenty-four male race walkers completed a graded exercise test and a 25-km race-walk trial. Throughout the 25-km race-walk, venous blood samples were collected pre-exercise, immediately post-exercise, and at 3-h post-exercise. Blood was analysed for serum ferritin, serum iron, Interleukin-6 (IL-6), and hepcidin-25 concentration.
Results
IL-6 and hepcidin-25 increased (7.6- and 7.5-fold, respectively) in response to the 25-km race-walk trial (both
p
< 0.01). Significant individual relationships were evident between 3-h post-exercise hepcidin-25, baseline serum ferritin and serum iron (
r
> 0.62;
p
< 0.05). Multiple regression analysis showed that these two iron parameters, in addition to post-exercise IL-6 concentration and 25-km race-walk time, accounted for ~77% of the variance in 3-h post-exercise hepcidin-25 (
p
< 0.01). A median split by the cohort’s baseline serum ferritin concentration (LOW: 58.0 vs. HIGH: 101.8 µg/L;
p
< 0.01) showed a significant between group difference in the 3-h post-exercise hepcidin-25 (LOW: 6.0 ± 3.6 vs. 11.3 ± 5.4 nM;
p
= 0.01), despite no differences in baseline serum iron, post-exercise IL-6, or 25-km race-walk time (all
p
> 0.05).
Conclusion
Despite exercise activating numerous hepcidin regulators, baseline iron status appears to play a dominant role in the regulation of hepcidin-25 in elite-level athletes subsequent to endurance exercise.
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