Ian Rollo

Influence of mouth rinsing a carbohydrate solution on 1-h running performance.

PURPOSE The aim of this study was to investigate the influence of mouth rinsing a CHO-electrolyte (CHO-E) solution on 1-h running performance. A second study determined whether mouth rinsing a CHO-E solution altered the blood glucose and plasma insulin concentrations at rest. METHODS After a 13-h fast, 10 endurance-trained male runners completed two 1-h performance runs on an automated treadmill while mouth rinsing 25 mL of either a 6.4% CHO-E (C) or placebo (P) solution immediately before and at 15-min intervals during the 1-h run. An additional 10 healthy active males followed the same mouth rinsing procedure during a 1-h resting period. Finger prick blood samples were obtained for the determination of blood glucose and plasma insulin concentrations. RESULTS Runners covered 211 m (90% confidence intervals = 42-380 m, P = 0.048) further during the C trial (14,298 ± 685 m, mean ± SD) in comparison with the P trial (14,086 ± 732 m). There was no change in blood glucose concentrations during the 1-h run (P: pre = 4.3 ± 0.2 mmol·L(-1), post = 4.3 ± 0.3 mmol·L(-1); C: pre = 4.3 ± 0.4 mmol·L(-1), post = 4.3 ± 0.3 mmol·L(-1)). At rest, there was no change in blood glucose (P: 4.3 ± 0.1 mmol·L(-1), C: 4.3 ± 0.2 mmol·L(-1)) or plasma insulin (P: 6.2 ± 1.1 mU·L(-1), CHO: 5.9 ± 1.0 1.1 mU·L(-1)) concentrations (P > 0.10). CONCLUSIONS Mouth rinsing a 6.4% CHO-E solution was associated with increased distance covered during a 1-h performance run in comparison to mouth rinsing a placebo solution. Mouth rinsing a CHO-E was not associated with changes in blood glucose concentration during exercise or at rest.

Effect of Mouth-Rinsing Carbohydrate Solutions on Endurance Performance

Ingesting carbohydrate-electrolyte solutions during exercise has been reported to benefit self-paced time-trial performance. The mechanism responsible for this ergogenic effect is unclear. For example, during short duration (≤1 hour), intense (>70% maximal oxygen consumption) exercise, euglycaemia is rarely challenged and adequate muscle glycogen remains at the cessation of exercise. The absence of a clear metabolic explanation has led authors to speculate that ingesting carbohydrate solutions during exercise may have a ‘non-metabolic’ or ‘central effect’ on endurance performance. This hypothesis has been explored by studies investigating the performance responses of subjects when carbohydrate solutions are mouth rinsed during exercise. The solution is expectorated before ingestion, thus removing the provision of carbohydrate to the peripheral circulation. Studies using this method have reported that simply having carbohydrate in the mouth is associated with improvements in endurance performance. However, the performance response appears to be dependent upon the pre-exercise nutritional status of the subject. Furthermore, the ability to identify a central effect of a carbohydrate mouth rinse maybe affected by the protocol used to assess its impact on performance. Studies using functional MRI and transcranial stimulation have provided evidence that carbohydrate in the mouth stimulates reward centres in the brain and increases corticomotor excitability, respectively. However, further research is needed to determine whether the central effects of mouth-rinsing carbohydrates, which have been seen at rest and during fatiguing exercise, are responsible for improved endurance performance.

Influence of Ingesting versus Mouth Rinsing a Carbohydrate Solution during a 1-h Run

PURPOSE To investigate the influence of ingesting versus mouth rinsing a carbohydrate-electrolyte solution on 1-h running performance. METHODS After a 14- to 15-h fast, 10 endurance-trained male runners (mean ± SD: VO2peak = 65.0 ± 4.4 mL·kg(-1)·min(-1)) completed three 1-h performance runs separated by 1 wk. In random order, runners ingested either a 8-mL·kg(-1) body mass of either a 6.4% carbohydrate-electrolyte solution (CHO) or a placebo solution (P) 30 min before or a 2-mL·kg(-1) body mass at 15-min intervals throughout the 1-h run. On a separate occasion, runners mouth rinsed (R) a 6.4% CHO, i.e., without ingestion, at the same times as in the ingestion trials. RESULTS Total distances covered in the CHO, P, and R trials were 14,515 ± 756, 14,190 ± 800, and 14,283 ± 758 m, respectively. Runners covered 320 m more (90% confidence interval = 140-510 m, P = 0.01) during the CHO trial compared with the P trial and 230 m more (90% confidence interval = 83-380 m, P = 0.019) in comparison with the R trial. There was no difference in n distance covered between the R and P trials (P = 1.0). CONCLUSIONS A greater distance was covered after the mouth rinse and ingestion of a 6.4% CHO during a 1-h performance run than when mouth rinsing the same solution or mouth rinsing followed by the ingestion of the same volume of a placebo solution.

Acute Effects of Carbohydrate Supplementation on Intermittent Sports Performance

Intermittent sports (e.g., team sports) are diverse in their rules and regulations but similar in the pattern of play; that is, intermittent high-intensity movements and the execution of sport-specific skills over a prolonged period of time (~1–2 h). Performance during intermittent sports is dependent upon a combination of anaerobic and aerobic energy systems, both of which rely on muscle glycogen and/or blood glucose as an important substrate for energy production. The aims of this paper are to review: (1) potential biological mechanisms by which carbohydrate may impact intermittent sport performance; (2) the acute effects of carbohydrate ingestion on intermittent sport performance, including intermittent high-intensity exercise capacity, sprinting, jumping, skill, change of direction speed, and cognition; and (3) what recommendations can be derived for carbohydrate intake before/during exercise in intermittent sports based on the available evidence. The most researched intermittent sport is soccer but some sport-specific studies have also been conducted in other sports (e.g., rugby, field hockey, basketball, American football, and racquet sports). Carbohydrate ingestion before/during exercise has been shown in most studies to enhance intermittent high-intensity exercise capacity. However, studies have shown mixed results with regards to the acute effects of carbohydrate intake on sprinting, jumping, skill, change of direction speed, and cognition. In most of these studies the amount of carbohydrate consumed was ~30–60 g/h in the form of a 6%–7% carbohydrate solution comprised of sucrose, glucose, and/or maltodextrin. The magnitude of the impact that carbohydrate ingestion has on intermittent sport performance is likely dependent on the carbohydrate status of the individual; that is, carbohydrate ingestion has the greatest impact on performance under circumstances eliciting fatigue and/or hypoglycemia. Accordingly, carbohydrate ingestion before and during a game seems to have the greatest impact on intermittent sports performance towards the end of the game.

Influence of ingesting a carbohydrate-electrolyte solution before and during a 1-hour run in fed endurance-trained runners

Abstract The aim of this study was to determine whether the ingestion of a carbohydrate-electrolyte solution would improve 1-h running performance in runners who had consumed a meal 3 h before exercise. Ten endurance-trained male runners completed two trials that required them to run as far as possible in 1 h on an automated treadmill that allowed changes in running speed without manual input. Following the consumption of the pre-exercise meal, which provided 2.5 g carbohydrate per kilogram body mass (BM), runners ingested either a 6.4% carbohydrate-electrolyte solution or placebo solution (i.e. 8 ml · kg BM−1) 30 min before and 2 ml · kg BM−1 at 15-min intervals throughout the 1-h run. There were no differences in total distance covered (placebo: 13,680 m, s = 1525; carbohydrate: 13,589 m, s = 1635) (P > 0.05). Blood glucose and lactate concentration, respiratory exchange ratio, and carbohydrate oxidation during exercise were not different between trials (P > 0.05). There were also no differences in ratings of perceived exertion, felt arousal or pleasure–displeasure between trials (P > 0.05). In conclusion, the ingestion of a 6.4% carbohydrate-electrolyte solution did not improve 1-h running performance when a high carbohydrate meal was consumed 3 h before exercise.

Repeatability of scores on a novel test of endurance running performance.

Abstract The aim of the present study was to determine the repeatability of a running endurance test using an automated treadmill system that requires no manual input to control running speed. On three separate occasions, 7 days apart, 10 experienced male endurance-trained runners (mean age 32 years, s = 10; [Vdot]O2peak 61 ml · kg−1 · min−1, s = 7) completed a treadmill time trial, in which they were instructed to run as far as possible in 60 min. The treadmill was instrumented with an ultrasonic feedback-controlled radar modulator that spontaneously regulated treadmill belt speed corresponding to the changing running speed of each runner. Estimated running intensity was 70%[Vdot]O2peak (s = 11) and the distance covered 13.5 km (s = 2), with no difference in mean performances between trials. The coefficient of variation, estimated using analysis of variance, with participant and trial as main effects, was 1.4%. In summary, the use of an automated treadmill system improved the repeatability of a 60-min treadmill time trial compared with time trials in which speed is controlled manually. The present protocol is a reliable method of assessing endurance performance in endurance-trained runners.

Resistance Exercise Augments Postprandial Overnight Muscle Protein Synthesis Rates

INTRODUCTION We have previously shown that protein ingestion before sleep increases overnight muscle protein synthesis rates. Whether prior exercise further augments the muscle protein synthetic response to presleep protein ingestion remains to be established. OBJECTIVE This study aimed to assess whether resistance-type exercise performed in the evening increases the overnight muscle protein synthetic response to presleep protein ingestion. METHODS Twenty-four healthy young men were randomly assigned to ingest 30 g intrinsically L-[1-C]-phenylalanine and L-[1-C]-leucine-labeled casein protein before going to sleep with (PRO + EX, n = 12) or without (PRO, n = 12) prior resistance-type exercise performed in the evening. Continuous intravenous L-[ring-H5]-phenylalanine, L-[1-C]-leucine, and L-[ring-H2]-tyrosine infusions were applied. Blood and muscle tissue samples were collected to assess whole-body protein balance, myofibrillar protein synthesis rates, and overnight incorporation of dietary protein-derived amino acids into de novo myofibrillar protein. RESULTS A total of 57% ± 1% of the ingested protein-derived phenylalanine appeared in the circulation during overnight sleep. Overnight myofibrillar protein synthesis rates were 37% (0.055%·h ± 0.002%·h vs. 0.040%·h ± 0.003%·h, P < 0.001, based on L-[ring- H5]-phenylalanine) and 31% (0.073%·h ± 0.004%·h vs. 0.055%·h ± 0.006%·h, P = 0.024, based on L-[1-C]-leucine) higher in PRO + EX compared with PRO. Substantially more of the dietary protein-derived amino acids were incorporated into de novo myofibrillar protein during overnight sleep in PRO + EX compared with PRO (0.026 ± 0.003 vs. 0.015 ± 0.003 molar percent excess, P = 0.012). CONCLUSIONS Resistance-type exercise performed in the evening augments the overnight muscle protein synthetic response to presleep protein ingestion and allows more of the ingested protein-derived amino acids to be used for de novo myofibrillar protein synthesis during overnight sleep.

The Influence of Carbohydrate Mouth Rinse on Self-Selected Intermittent Running Performance

This study investigated the influence of mouth rinsing a carbohydrate solution on self-selected intermittent variable-speed running performance. Eleven male amateur soccer players completed a modified version of the Loughborough Intermittent Shuttle Test (LIST) on 2 occasions separated by 1 wk. The modified LIST allowed the self-selection of running speeds during Block 6 of the protocol (75-90 min). Players rinsed and expectorated 25 ml of noncaloric placebo (PLA) or 10% maltodextrin solution (CHO) for 10 s, routinely during Block 6 of the LIST. Self-selected speeds during the walk and cruise phases of the LIST were similar between trials. Jogging speed was significantly faster during the CHO (11.3 ± 0.7 km · h(-1)) than during the PLA trial (10.5 ± 1.3 km · h(-1)) (p = .010); 15-m sprint speeds were not different between trials (PLA: 2.69 ± 0.18 s: CHO: 2.65 ± 0.13 s) (F(2, 10), p = .157), but significant benefits were observed for sprint distance covered (p = .024). The threshold for the smallest worthwhile change in sprint performance was set at 0.2 s. Inferential statistical analysis showed the chance that CHO mouth rinse was beneficial, negligible, or detrimental to repeated sprint performance was 86%, 10%, and 4%, respectively. In conclusion, mouth rinsing and expectorating a 10% maltodextrin solution was associated with a significant increase in self-selected jogging speed. Repeated 15-m sprint performance was also 86% likely to benefit from routinely mouth rinsing a carbohydrate solution in comparison with a taste-matched placebo.

Maximal Fat Oxidation Rates in an Athletic Population

Introduction The aim of this study was to describe maximal fat oxidation (MFO) rates in an athletic population. Method In total, 1121 athletes (933 males and 188 females), from a variety of sports and competitive level, undertook a graded exercise test on a treadmill in a fasted state (≥5 h fasted). Rates of fat oxidation were determined using indirect calorimetry. Results The average MFO was 0.59 ± 0.18 g·min−1, ranging from 0.17 to 1.27 g·min−1. Maximal rates occurred at an average exercise intensity of 49.3% ± 14.8% V˙O2max, ranging from 22.6% to 88.8% V˙O2max. In absolute terms, male athletes had significantly higher MFO compared with females (0.61 and 0.50 g·min−1, respectively, P < 0.001). Expressed relative to fat-free mass (FFM), MFO were higher in the females compared with males (MFO/FFM: 11.0 and 10.0 mg·kg·FFM−1·min−1, respectively, P < 0.001). Soccer players had the highest MFO/FFM (10.8 mg·kg·FFM−1·min−1), ranging from 4.1 to 20.5 mg·kg·FFM−1·min−1, whereas American Football players displayed the lowest rates of MFO/FFM (9.2 mg·kg·FFM−1·min−1). In all athletes, and when separated by sport, large individual variations in MFO rates were observed. Significant positive correlations were found between MFO (g·min−1) and the following variables: FFM, V˙O2max, FATMAX (the exercise intensity at which the MFO was observed), percent body fat, and duration of fasting. When taken together these variables account for 47% of the variation in MFO. Conclusion MFO and FATMAX vary significantly between athletes participating in different sports but also in the same sport. Although variance in MFO can be explained to some extent by body composition and fitness status, more than 50% of the variance is not explained by these variables and remains unaccounted for.

Pre-sleep dietary protein-derived amino acids are incorporated in myofibrillar protein during post-exercise overnight recovery

The purpose of this study was to determine the impact of ingesting 30 g casein protein with and without 2 g free leucine before sleep on myofibrillar protein synthesis rates during postexercise overnight recovery. Thirty-six healthy young men performed a single bout of resistance-type exercise in the evening (1945) after a full day of dietary standardization. Thirty minutes before sleep (2330), subjects ingested 30 g intrinsically l-[1-13C]phenylalanine-labeled protein with (PRO+leu, n = 12) or without (PRO, n = 12) 2 g free leucine, or a noncaloric placebo (PLA, n = 12). Continuous intravenous l-[ ring-2H5]phenylalanine, l-[1-13C]leucine, and l-[ ring-2H2]tyrosine infusions were applied. Blood and muscle tissue samples were collected to assess whole body protein net balance, myofibrillar protein synthesis rates, and overnight incorporation of dietary protein-derived amino acids into myofibrillar protein. Protein ingestion before sleep improved overnight whole body protein net balance ( P < 0.001). Myofibrillar protein synthesis rates did not differ significantly between treatments as assessed by l-[ ring-2H5]phenylalanine (0.057 ± 0.002, 0.055 ± 0.002, and 0.055 ± 0.004%/h for PLA, PRO, and PRO+leu, respectively; means ± SE; P = 0.850) or l-[1-13C]leucine (0.080 ± 0.004, 0.073 ± 0.004, and 0.083 ± 0.006%/h, respectively; P = 0.328). Myofibrillar l-[1-13C]phenylalanine enrichments increased following protein ingestion but did not differ between the PRO and PRO+leu treatments. In conclusion, protein ingestion before sleep improves whole body protein net balance and provides amino acids that are incorporated into myofibrillar protein during sleep. However, the ingestion of 30 g casein protein with or without additional free leucine before sleep does not increase muscle protein synthesis rates during postexercise overnight recovery.