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1.
Effect of carbohydrate ingestion during cycling exercise on affective valence and activation in recreational exercisers.
Lee, V, Rutherfurd-Markwick, K, Ali, A
Journal of sports sciences. 2018;(3):340-347
Abstract
Carbohydrate (CHO) ingestion enhances "feel-good" responses during acute exercise but no study has examined the effect of regular ingestion of CHO on affective valence. We investigated the effect of CHO ingestion on perceptual responses and perceived work intensity of individual exercise sessions throughout a 10-week cycling ("spin") exercise intervention. We also assessed whether any changes in affect and/or perceived work intensity would influence health and fitness parameters. Twelve recreational exercisers (46 ± 9 years; nine females and three males) were randomly allocated to either CHO (7.5% CHO; 5 mL · kg-1 per exercise session; n = 6; CHO) or placebo (0% CHO, taste- and volume-matched solution; n = 6; PLA) groups. Participants exercised 2 × 45-min per week, over a 10-week intervention period. Perceptual measures of exertion (RPE), affect (feeling scale, FS) and activation (felt arousal scale, FAS) were assessed after each exercise session. The FAS ratings increased over time in CHO but decreased throughout the intervention in PLA (P = 0.03). There were no differences in heart rate (P = 0.70), RPE (P = 0.05) and FS (P = 0.84) between trials. Furthermore, no changes in health and fitness parameters were observed over time or between groups. CHO ingestion enhanced ratings of activation in recreational exercisers throughout a 10-week cycling intervention.
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2.
Perception of Breakfast Ingestion Enhances High-Intensity Cycling Performance.
Mears, SA, Dickinson, K, Bergin-Taylor, K, Dee, R, Kay, J, James, LJ
International journal of sports physiology and performance. 2018;(4):504-509
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Abstract
PURPOSE To examine the effect on short-duration, high-intensity cycling time-trial (TT) performance when a semisolid breakfast containing carbohydrate (CHO) or a taste- and texture-matched placebo is ingested 90 min preexercise compared with a water (WAT) control. METHODS A total of 13 well-trained cyclists (mean [SD]: age = 25 [8] y, body mass = 71.1 [5.9] kg, height = 1.76 [0.04] m, maximum power output = 383 [46] W, and peak oxygen uptake = 4.42 [0.53] L·min-1) performed 3 experimental trials examining breakfast ingestion 90 min before a 10-min steady-state cycle (60% maximum power output) and an ∼20-min TT (to complete a workload target of 376 [36] kJ). Subjects consumed either WAT, a semisolid CHO breakfast (2 g carbohydrate CHO·kg-1 body mass), or a taste- and texture-matched placebo (PLA). Blood lactate and glucose concentrations were measured periodically throughout the rest and exercise periods. RESULTS The TT was completed more quickly in CHO (1120 [69] s; P = .006) and PLA (1112 [50] s; P = .030) compared with WAT (1146 [74] s). Ingestion of CHO caused an increase in blood glucose concentration throughout the rest period in CHO (peak at 30-min rest = 7.37 [1.10] mmol·L-1; P < .0001) before dropping below baseline levels after the steady-state cycling. CONCLUSION A short-duration cycling TT was completed more quickly when subjects perceived that they had consumed breakfast (PLA or CHO) 90 min prior to the start of the exercise. The improvement in performance is likely attributable to a psychological rather than physiological effect.
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3.
Ketogenic diets for drug-resistant epilepsy.
Martin-McGill, KJ, Jackson, CF, Bresnahan, R, Levy, RG, Cooper, PN
The Cochrane database of systematic reviews. 2018;(11):CD001903
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BACKGROUND Ketogenic diets (KDs), being high in fat and low in carbohydrates, have been suggested to reduce seizure frequency in people with epilepsy. At present, such diets are mainly recommended for children who continue to have seizures despite treatment with antiepileptic drugs (AEDs) (drug-resistant epilepsy). Recently, there has been interest in less restrictive KDs, including the modified Atkins diet (MAD), and the use of these diets has extended into adult practice. This is an update of a review first published in 2003 and last updated in 2016. OBJECTIVES To assess the effects of KDs for drug-resistant epilepsy by reviewing the evidence from randomised controlled trials. SEARCH METHODS For the latest update we searched the Cochrane Epilepsy Group's Specialized Register (11 April 2017), the Cochrane Central Register of Controlled Trials (CENTRAL) via the Cochrane Register of Studies Online (CRSO, 11 April 2017), MEDLINE (Ovid, 11 April 2017), ClinicalTrials.gov (11 April 2017) and the WHO International Clinical Trials Registry Platform (ICTRP, 11 April 2017). We imposed no language restrictions. We checked the reference lists of retrieved studies for additional reports of relevant studies. SELECTION CRITERIA Randomised controlled trials or quasi-randomised controlled trials of ketogenic diets for people with drug-resistant epilepsy. DATA COLLECTION AND ANALYSIS Two review authors independently applied predefined criteria to extract data and assessed study quality. MAIN RESULTS We identified 11 randomised controlled trials (RCTs) that generated 15 publications.All trials applied an intention-to-treat analysis with varied randomisation methods. The 11 studies recruited 778 patients; 712 children and adolescents and 66 adults. We assessed all 11 studies to be at low to unclear risk of bias for the following domains: random sequence generation, allocation concealment and selective reporting. For the other domains (blinding, incomplete outcome data, other bias) assessments were varied (low, unclear and high risk of bias). We could not conduct a meta-analysis due to the heterogeneity of the studies and the quality of the evidence was low to very low (GRADE ratings).Reported rates of seizure freedom reached as high as 55% in a classical 4:1 KD group after three months and reported rates of seizure reduction reached as high as 85% in a classical 4:1 KD group after three months (GRADE rating low).One trial found no significant difference between the fasting-onset and gradual-onset KD for rates of seizure freedom, and reported a greater rate of seizure reduction in the gradual-onset KD group.Studies assessing the efficacy of the MAD reported seizure freedom rates of up to 25% and seizure reduction rates of up to 60% in children. One study used a simplified MAD (sMAD) and reported seizure freedom rates of 15% and seizure reduction rates of 56% in children. One study utilised a MAD in adults and reported seizure reduction rates of 35%, but no patients became seizure free (GRADE rating low).Adverse effects of the dietary interventions were experienced in all studies. The most commonly reported adverse effects were gastrointestinal syndromes. It was common that adverse effects were the reason for participants dropping out of trials (GRADE rating low). Other reasons for dropout included lack of efficacy and non-acceptance of the diet (GRADE rating low).Although there was some evidence for greater antiepileptic efficacy for a classical 4:1 KD over lower ratios, the classical 4:1 KD was consistently associated with more adverse effects.One study assessed the effect of dietary interventions on quality of life, cognition and behavioural functioning, reporting participants in the KD group to be more active, more productive and less anxious after four months, compared to the control group. However, no significant difference was found in quality-adjusted life years (QALYs) between the KD group and control group at four or 16 months (GRADE rating very low). AUTHORS' CONCLUSIONS The RCTs discussed in this review show promising results for the use of KDs in epilepsy. However, the limited number of studies, small sample sizes and the limited studies in adults, resulted in a low to very low overall quality of evidence.There were adverse effects within all of the studies and for all KD variations, such as short-term gastrointestinal-related disturbances and increased cholesterol. However, study periods were short, therefore the long-term risks associated with these adverse effects is unknown. Attrition rates remained a problem with all KDs and across all studies; reasons for this being lack of observed efficacy and dietary tolerance.Only one study reported the use of KDs in adults with epilepsy; therefore further research would be of benefit.Other more palatable but related diets, such as the MAD, may have a similar effect on seizure control as the classical KD, but this assumption requires more investigation. For people who have medically intractable epilepsy or people who are not suitable for surgical intervention, KDs remain a valid option; however, further research is required.
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Effect of Carbohydrate Mouth Rinse on Performance after Prolonged Submaximal Cycling.
Jensen, M, Klimstra, M, Sporer, B, Stellingwerff, T
Medicine and science in sports and exercise. 2018;(5):1031-1038
Abstract
UNLABELLED Previous studies have shown improved shorter duration (∼1 h) performance with carbohydrate (CHO) mouth rinsing (WASH), especially in overnight fasted/non-fuelled subjects. PURPOSE To determine the effect of WASH on cycling time trial (TT) performance and muscle activity (EMG) after 2 h of submaximal cycling while receiving CHO (FED). METHODS In a double-blind, placebo-controlled crossover design, 10 well-trained males cyclists (V˙O2max: 65 mL·kg·min) completed two experimental trials. Each trial consisted of a standardized pretrial snack (2 h prior) followed by 120 min of steady-state (SS) cycling (∼60% V˙O2max) followed by an approximately 30-min TT, randomized as follows: 1) 30 g CHO·h during SS + WASH during TT (every 20% of TT) (FEDWASH); 2) 30 g CHO·h during SS + placebo (PLA) wash during TT (FEDPLA). RESULTS Although FEDWASH was not significantly different than FEDPLA (P = 0.51), there was a 1.7% (90% confidence interval, +6.4% to -3.2%; ES, 0.21) decrease in TT time (35 s) for FEDWASH compared with FEDPLA, with qualitative probabilities of a 60% positive and 23% trivial outcome. For EMG, soleus showed significant increase, whereas medial gastrocnemius showed significant decrease in muscle recruitment from the beginning 20% TT segment to the last 20% only in the FEDPLA condition, which coincided with a slower (P = 0.01) last 20% of the TT in FEDPLA versus FEDWASH. CONCLUSIONS Contrary to previous studies, this investigation utilized conditions of high ecological validity including a pretrial snack and CHO during SS. Significant changes in muscle recruitment and time over the last 20% of the TT, along with an average 1.7% improvement in TT time, suggest CHO mouth rinse helps maintain power output late in TT compared with placebo. Although marginal gains were achieved with a CHO mouth rinse (35 s), small performance effects can have significant outcomes in real-world competitions.
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Carbohydrate quality and quantity and risk of coronary heart disease among US women and men.
AlEssa, HB, Cohen, R, Malik, VS, Adebamowo, SN, Rimm, EB, Manson, JE, Willett, WC, Hu, FB
The American journal of clinical nutrition. 2018;(2):257-267
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BACKGROUND The carbohydrate-to-fiber ratio is a recommended measure of carbohydrate quality; however, its relation to incident coronary heart disease (CHD) is not currently known. OBJECTIVE We aimed to assess the relation between various measures of carbohydrate quality and incident CHD. DESIGN Data on diet and lifestyle behaviors were prospectively collected on 75,020 women and 42,865 men participating in the Nurses' Health Study (NHS) and the Health Professionals Follow-Up Study (HPFS) starting in 1984 and 1986, respectively, and every 2-4 y thereafter until 2012. All participants were free of known diabetes mellitus, cancer, or cardiovascular disease at baseline. Cox proportional hazards regression models were used to assess the relation between dietary measures of carbohydrate quality and incident CHD. RESULTS After 1,905,047 (NHS) and 921,975 (HPFS) person-years of follow-up, we identified 7,320 cases of incident CHD. In models adjusted for age, lifestyle behaviors, and dietary variables, the highest quintile of carbohydrate intake was not associated with incident CHD (pooled-RR = 1.04; 95% CI: 0.96, 1.14; P-trend = 0.31). Total fiber intake was not associated with risk of CHD (pooled-RR = 0.94; 95% CI: 0.85, 1.03; P-trend = 0.72), while cereal fiber was associated with a lower risk for incident CHD (pooled-RR = 0.80; 95% CI: 0.74, 0.87; P-trend < 0.0001). In fully adjusted models, the carbohydrate-to-total fiber ratio was not associated with incident CHD (pooled-RR = 1.04; 95% CI: 0.96, 1.13; P-trend = 0.46). However, the carbohydrate-to-cereal fiber ratio and the starch-to-cereal fiber ratio were associated with an increased risk for incident CHD (pooled-RR = 1.20; 95% CI: 1.11, 1.29; P-trend < 0.0001, and pooled-RR = 1.17; 95%CI: 1.09, 1.27; P-trend < 0.0001, respectively). CONCLUSION Dietary cereal fiber appears to be an important component of carbohydrate quality. The carbohydrate-to-cereal fiber ratio and the starch-to-cereal fiber ratio, but not the carbohydrate-to-fiber ratio, was associated with an increased risk for incident CHD. Future research should focus on how various measures of carbohydrate quality are associated with CHD prevention. This trial was registered at clinicaltrials.gov as NCT03214861.
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Post-Exercise Carbohydrate-Energy Replacement Attenuates Insulin Sensitivity and Glucose Tolerance the Following Morning in Healthy Adults.
Taylor, HL, Wu, CL, Chen, YC, Wang, PG, Gonzalez, JT, Betts, JA
Nutrients. 2018;(2)
Abstract
The carbohydrate deficit induced by exercise is thought to play a key role in increased post-exercise insulin action. However, the effects of replacing carbohydrate utilized during exercise on postprandial glycaemia and insulin sensitivity are yet to be determined. This study therefore isolated the extent to which the insulin-sensitizing effects of exercise are dependent on the carbohydrate deficit induced by exercise, relative to other exercise-mediated mechanisms. Fourteen healthy adults performed a 90-min run at 70% V ˙ O 2 max starting at 1600-1700 h before ingesting either a non-caloric artificially-sweetened placebo solution (CHO-DEFICIT) or a 15% carbohydrate solution (CHO-REPLACE; 221.4 ± 59.3 g maltodextrin) to precisely replace the measured quantity of carbohydrate oxidized during exercise. The alternate treatment was then applied one week later in a randomized, placebo-controlled, and double-blinded crossover design. A standardized low-carbohydrate evening meal was consumed in both trials before overnight recovery ahead of a two-hour oral glucose tolerance test (OGTT) the following morning to assess glycemic and insulinemic responses to feeding. Compared to the CHO-DEFICIT condition, CHO-REPLACE increased the incremental area under the plasma glucose curve by a mean difference of 68 mmol·L-1 (95% CI: 4 to 132 mmol·L-1; p = 0.040) and decreased the Matsuda insulin sensitivity index by a mean difference of -2 au (95% CI: -1 to -3 au; p = 0.001). This is the first study to demonstrate that post-exercise feeding to replaceme the carbohydrate expended during exercise can attenuate glucose tolerance and insulin sensitivity the following morning. The mechanism through which exercise improves insulin sensitivity is therefore (at least in part) dependent on carbohydrate availability and so the day-to-day metabolic health benefits of exercise might be best attained by maintaining a carbohydrate deficit overnight.
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Carbohydrate mouth rinse does not affect performance during a 60-min running race in women.
Chryssanthopoulos, C, Ziaras, C, Oosthuyse, T, Lambropoulos, I, Giorgios P, P, Zacharogiannis, E, Philippou, A, Maridaki, M
Journal of sports sciences. 2018;(7):824-833
Abstract
This study examined the effect of carbohydrate mouth rinsing on endurance running performance in women. Fifteen female recreational endurance runners, who used no oral contraceptives, ran two races of 1-h duration on an indoor track (216-m length) at 18:00 h after an 8-h fast with a 7-days interval between races, corresponding to the 3rd-10th day of each premenopausal runner's menstrual cycle, or any day for the postmenopausal runners. In a double-blind random order, participants rinsed their mouth with 25 ml of either a 6.4% carbohydrate (RCHO) or a placebo solution (RP). No fluid was ingested during exercise. Serum 17β-Εstradiol (P = 0.59) and Progesterone (P = 0.35) did not differ between treatments. There was no difference in 1-hour running performance (RCHO: 10,621.88 ± 205.98 m vs. RP: 10,454.00 ± 206.64 m; t = 1.784, P = 0.096). Furthermore, the mean percentage effect (±99%CI) of RCHO relative to RP, 1.67% (-1.1% to 4.4%), and Cohen's effect size (d = 0.21) support a trivial outcome of RCHO for total distance covered. In conclusion, carbohydrate mouth rinsing did not improve 60-min track running performance in female recreational runners competing in a low ovarian hormone condition, after an 8-h fast and when no fluid was ingested during exercise.
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Carbohydrate knowledge, lifestyle and insulin: an observational study of their association with glycaemic control in adults with type 1 diabetes.
Smythe, K, Saw, M, Mak, M, Wong, VW
Journal of human nutrition and dietetics : the official journal of the British Dietetic Association. 2018;(5):597-602
Abstract
BACKGROUND The ability to achieve optimal glycaemic control varies widely among individuals with type 1 diabetes. The present study aimed to explore the factors that are associated with optimal glycaemic control compared to suboptimal control. METHODS An observational study design was used to explore the association of various factors with glycaemic control. Surveys were completed by individuals who attended the type 1 diabetes clinic at a tertiary hospital in New South Wales (NSW), Australia. Clinical and demographic information and attendance at dietary review were also collected. RESULTS One hundred and three individuals completed the survey. Those with optimal control [glycated haemoglobin ≤7.0% (53 mmol mol-1 )] had a significantly shorter mean (SD) duration of diabetes [10.1 (12.6) years versus 18.8 (12.8) years, P = 0.005), were less likely to omit basal and bolus insulin (18.2% versus 47.5%, P = 0.016; 36.4% versus 61.8%, P = 0.034, respectively), and were less likely to report low confidence in managing their diabetes (9.1% versus 35.4%, P = 0.017). Participants who were able to identify carbohydrate sources were significantly more likely to have attended dietary review in the past 12 months (60.5% versus 20.0%, P = 0.001). However, they were not more likely to have better glycaemic control. CONCLUSIONS The present study identified that consistency in taking insulin and confidence in self-management was associated with better glycaemic control. An association was also found between recent dietary review and better carbohydrate knowledge, although this did not translate into better glycaemic control. Future investigation into the application of carbohydrate knowledge is required.
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The effects of acute carbohydrate and caffeine feeding strategies on cycling efficiency.
Cole, M, Hopker, JG, Wiles, JD, Coleman, DA
Journal of sports sciences. 2018;(7):817-823
Abstract
To assess the effect of carbohydrate and caffeine on gross efficiency (GE), 14 cyclists (V̇O2max 57.6 ± 6.3 ml.kg-1.min-1) completed 4 × 2-hour tests at a submaximal exercise intensity (60% Maximal Minute Power). Using a randomized, counter-balanced crossover design, participants consumed a standardised diet in the 3-days preceding each test and subsequently ingested either caffeine (CAF), carbohydrate (CHO), caffeine+carbohydrate (CAF+CHO) or water (W) during exercise whilst GE and plasma glucose were assessed at regular intervals (~30 mins). GE progressively decreased in the W condition but, whilst caffeine had no effect, this was significantly attenuated in both trials that involved carbohydrate feedings (W = -1.78 ± 0.31%; CHO = -0.70 ± 0.25%, p = 0.008; CAF+CHO = -0.63 ± 0.27%, p = 0.023; CAF = -1.12 ± 0.24%, p = 0.077). Blood glucose levels were significantly higher in carbohydrate ingestion conditions (CHO = 4.79 ± 0.67 mmol·L-1, p < 0.001; CAF+CHO = 5.05 ± 0.81 mmol·L-1, p < 0.001; CAF = 4.46 ± 0.75 mmol·L-1; W = 4.20 ± 0.53 mmol·L-1). Carbohydrate ingestion has a small but significant effect on exercise-induced reductions in GE, indicating that cyclists' feeding strategy should be carefully monitored prior to and during assessment.
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Combined Carbohydrate and Protein Ingestion During Australian Rules Football Matches and Training Sessions Does Not Reduce Fatigue or Accelerate Recovery Throughout a Weeklong Junior Tournament.
Lee, NA, Fell, JW, Pitchford, NW, Hall, AH, Leveritt, MD, Kitic, CM
Journal of strength and conditioning research. 2018;(2):344-355
Abstract
Lee, NA, Fell, JW, Pitchford, NW, Hall, AH, Leveritt, MD, and Kitic, CM. Combined carbohydrate and protein ingestion during Australian rules football matches and training sessions does not reduce fatigue or accelerate recovery throughout a weeklong junior tournament. J Strength Cond Res 32(2): 344-355, 2018-Australian rules football (ARF) is a physically demanding sport that can induce high levels of fatigue. Fatigue may be intensified during periods where multiple matches are played with limited recovery time. Combined carbohydrate and protein (CHO + PRO) intake during physical activity may provide performance and recovery benefits. The aim of this study was to investigate whether CHO + PRO ingestion during ARF matches and training sessions throughout a tournament would enhance performance or recovery in comparison with CHO-only ingestion. Australian rules football players (n = 21) competing in a 7-day national tournament participated in this randomized and double-blinded study. Beverages containing either CHO (n = 10) or CHO + PRO (n = 11) were provided during matches (day 1, day 4, and day 7) and training sessions (day 2 and day 3). Countermovement jumps (CMJs), ratings of muscle soreness, and autonomic function were assessed throughout the tournament. Gastrointestinal tract (GI) discomfort was measured after matches. Countermovement jump peak velocity increased in the CHO + PRO group (p = 0.01) but not in the CHO group. There were no differences in the other CMJ variables. In both groups, muscle soreness increased from days 0 and 1 to day 2 (p ≤ 0.05) but did not remain elevated. R-R intervals (time elapsed between successive peaks in QRS complexes) increased in both groups from day 1 to day 7 (mean difference = 59.85 ms, p < 0.01). Postmatch GI discomfort was not different (p > 0.05) between groups. When daily dietary protein is adequate (>1.8 g·kg·d), the ingestion of CHO + PRO during matches and training sessions throughout a tournament does not reduce muscle soreness nor have clear benefits for neuromuscular recovery or modulate autonomic function in junior ARF athletes, compared with that of CHO alone.