e6776 10.1097/MCO.0b013e32832e6776 de Oliveira , E.P. , & Burini , R.C . ( 2014 ). Carbohydrate-dependent, exercise-induced gastrointestinal distress . Nutrients, 6 ( 10 ), 4191 – 4199 . doi:10.3390/nu6104191 10.3390/nu6104191 Flood , T.R. , Montanari , S. , Wicks , M. , Blanchard , J
Andy J. King, Joshua T. Rowe, and Louise M. Burke
fat oxidation and gastrointestinal distress without changing performance . Nutrients, 8 ( 7 ), 392 . PubMed ID: 27347999 doi:10.3390/nu8070392 10.3390/nu8070392 Braakhuis , A.J. , Meredith , K. , Cox , G.R. , Hopkins , W.G. , & Burke , L.M. ( 2003 ). Variability in estimation of self
Kristin J. Stuempfle, Martin D. Hoffman, and Tamara Hew-Butler
Gastrointestinal (GI) distress is common during ultrarunning.
To determine if race diet is related to GI distress in a 161-km ultramarathon.
Fifteen (10 male, 5 female) consenting runners in the Javelina Jundred (6.5 loops on a desert trail) participated. Body mass was measured immediately prerace and after each loop. Runners reported if they had nausea, vomiting, abdominal cramps, and/or diarrhea after each loop. Subjects were interviewed after each loop to record food, fluid, and electrolyte consumption. Race diets were analyzed using Nutritionist Pro.
Nine (8 male, 1 female) of 15 runners experienced GI distress including nausea (89%), abdominal cramps (44%), diarrhea (44%), and vomiting (22%). Fluid consumption rate was higher (p = .001) in runners without GI distress (10.9 ± 3.2 ml · kg−1 · hr−1) than in those with GI distress (5.9 ± 1.6 ml · kg−1 · hr−1). Runners without GI distress consumed a higher percentage fat (p = .03) than runners with GI distress (16.5 ± 2.6 vs. 11.1 ± 5.0). In addition, fat intake rate was higher (p = .01) in runners without GI distress (0.06 ± 0.03 g · kg−1 · hr−1) than in runners with GI distress (0.03 ± 0.01 g · kg−1 · hr−1). Lower fluid and fat intake rates were evident in those developing GI distress before the onset of symptoms.
A race diet with higher percentage fat and higher intake rates of fat and fluid may protect ultramarathoners from GI distress. However, these associations do not indicate cause and effect, and factors other than race diet may have contributed to GI distress.
Jeffrey J. Zachwieja, David L. Costill, Glenn C. Beard, Robert A. Robergs, David D. Pascoe, and Dawn E. Anderson
To determine the effect of a carbonated carbohydrate (CHO) drink on gastric function and exercise performance, eight male cyclists completed four 120- min bouts of cycling. Each bout consisted of a 105-min ride at 70%
Patrick B. Wilson
Gastrointestinal (GI) symptoms may affect up to 90% of competitors during endurance races. Studies have typically assessed GI symptoms retrospectively or only over an acute timeframe, and information on the validity and reliability of the questionnaires employed is lacking. This investigation aimed to estimate the frequency of GI distress experienced by runners over 30 days and to establish the validity and reliability of a retrospective GI symptom questionnaire. Runners (70 men, 75 women) recorded GI symptoms with a prospective journal for 30 days. Retrospective GI symptom data were then collected after the 30-day period on two occasions within one week. GI symptoms were rated on a 0–10 scale. Descriptive statistics for GI symptoms are reported as medians (interquartile ranges) because of nonnormal distributions. Men and women experienced at least one GI symptom on 84.0% (59.8–95.1%) and 78.3% (50.0–95.2%) of runs, respectively. Moderate-to-severe GI symptoms (score of ≥5) were experienced on 13.8% (6.7–37.3%) and 21.7% (5.3–41.2%) of runs for men and women. Spearman’s rho correlations between journal ratings and retrospective questionnaire ratings ranged from 0.47 to 0.82 (all p < .001), although they were highest when journal ratings were quantified as mean 30-day values (all rho ≥ 0.59). Reliability of the retrospective questionnaire ratings was high (rho = 0.78–0.92; p < .001). In comparison with tracking GI symptoms with a daily journal, retrospective questionnaires seem to offer a convenient and reasonably valid and reliable method of quantifying GI symptoms over 30 days.
Mahdi Sareban, David Zügel, Karsten Koehler, Paul Hartveg, Martina Zügel, Uwe Schumann, Jürgen Michael Steinacker, and Gunnar Treff
The ingestion of exogenous carbohydrates (CHO) during prolonged endurance exercise, such as long-distance triathlon, is considered beneficial with regard to performance. However, little is known about whether this performance benefit differs among different forms of CHO administration. To this end, the purpose of our study was to determine the impact of CHO ingestion from a semisolid source (GEL) on measures of performance and gastrointestinal (GI) comfort compared with CHO ingestion from a liquid source (LIQ). Nine well-trained triathletes participated in this randomized crossover study. Each participant completed a 60-min swim, 180-min bike exercise, and a 60-min all-out run in a laboratory environment under 2 conditions, once while receiving 67.2 ± 7.2 g · h−1 (M ± SD) of CHO from GEL and once while receiving 67.8 ± 4.2 g · h−1 of CHO from LIQ. The amount of fluid provided was matched among conditions. Respiratory exchange ratio (RER), blood glucose, and lactate as well as GI discomfort were assessed at regular intervals during the experiment. The distance covered during the final all-out run was not significantly different among participants ingesting GEL (11.81 ± 1.38 km) and LIQ (11.91 ± 1.53 km; p = .89). RER, blood glucose, and lactate did not differ significantly at any time during the experiment. Seven participants reported GI discomfort with GEL, and no athlete reported GI discomfort with LIQ (p = .016). This study suggests that administration of GEL does not alter long-distance triathlon performance when compared with LIQ, but GEL seems to be associated with reduced GI tolerance. Athletes should consider this a potential disadvantage of GEL administration during long-distance triathlon.
Beate Pfeiffer, Alexandra Cotterill, Dominik Grathwohl, Trent Stellingwerff, and Asker E. Jeukendrup
Two studies were conducted to investigate gastrointestinal (GI) tolerance of high carbohydrate (CHO) intakes during intense running. The first study investigated tolerance of a CHO gel delivering glucose plus fructose (GLU+FRC) at different rates. The second study investigated tolerance of high intakes of glucose (GLU) vs. GLU+FRC gel. Both studies used a randomized, 2-treatment, 2-period crossover design: Endurance-trained men and women (Study 1: 26 men, 8 women; 37 ± 11 yr; 73 ± 9 kg; 1.76 ± 0.07 m. Study 2: 34 men, 14 women; 35 ± 10 yr; 70 ± 9 kg; 1.75 ± 0.09 m) completed two 16-km outdoor-runs. In Study 1 gels were administered to provide 1.0 or 1.4 g CHO/min with ad libitum water intake every 3.2 km. In Study 2 GLU or GLU+FRC gels were given in a double-blind manner to provide 1.4 g CHO/min. In both studies a postexercise questionnaire assessed 17 symptoms on a 10-point scale (from 0 to 9). For all treatments, GI complaints were mainly scored at the low end of the scale. In Study 1 mean scores ranged from 0.00 ± 0.00 to 1.12 ± 1.90, and in Study 2, from 0.00 ± 0.0 to 1.27 ± 1.78. GI symptoms were grouped into upper abdominal, lower abdominal, and systemic problems. There were no significant treatment differences in these categories in either study. In conclusion, despite high CHOgel intake, and regardless of the blend (GLU vs. GLU+FRC), average scores for GI symptoms were at the low end of the scale, indicating predominantly good tolerance during a 16-km run. Nevertheless, some runners (~10–20%) experienced serious problems, and individualized feeding strategies might be required.
Ernst Albin Hansen, Anders Emanuelsen, Robert Mørkegaard Gertsen, and Simon Schøler Raadahl Sørensen
It was tested whether a marathon was completed faster by applying a scientifically based rather than a freely chosen nutritional strategy. Furthermore, gastrointestinal symptoms were evaluated. Nonelite runners performed a 10 km time trial 7 weeks before Copenhagen Marathon 2013 for estimation of running ability. Based on the time, runners were divided into two similar groups that eventually should perform the marathon by applying the two nutritional strategies. Matched pairs design was applied. Before the marathon, runners were paired based on their prerace running ability. Runners applying the freely chosen nutritional strategy (n = 14; 33.6 ± 9.6 years; 1.83 ± 0.09 m; 77.4 ± 10.6 kg; 45:40 ± 4:32 min for 10 km) could freely choose their in-race intake. Runners applying the scientifically based nutritional strategy (n = 14; 41.9 ± 7.6 years; 1.79 ± 0.11 m; 74.6 ± 14.5 kg; 45:44 ± 4:37 min) were targeting a combined in-race intake of energy gels and water, where the total intake amounted to approximately 0.750 L water, 60 g maltodextrin and glucose, 0.06 g sodium, and 0.09 g caffeine per hr. Gastrointestinal symptoms were assessed by a self-administered postrace questionnaire. Marathon time was 3:49:26 ± 0:25:05 and 3:38:31 ± 0:24:54 hr for runners applying the freely chosen and the scientifically based strategy, respectively (p = .010, effect size=-0.43). Certain runners experienced diverse serious gastrointestinal symptoms, but overall, symptoms were low and not different between groups (p > .05). In conclusion, nonelite runners completed a marathon on average 10:55 min, corresponding to 4.7%, faster by applying a scientifically based rather than a freely chosen nutritional strategy. Furthermore, average values of gastrointestinal symptoms were low and not different between groups.
Mathilde Guillochon and David S. Rowlands
Carbohydrate sports drinks produce worthwhile benefits to endurance performance compared with noncaloric controls. However, athletes now consume carbohydrate in a range of formats, including gels and bars, but the comparable performance outcomes are unknown. Therefore, the aim of this study was to establish the relative effects of drink, gel, bar, and mixed carbohydrate formats on intense cycling performance. In a treatmentapparent randomized crossover design, 12 well-trained male cyclists completed 4 trials comprising a 140-min race simulation, followed by a double-blind slow-ramp to exhaustion (0.333 W·s-1). Carbohydrate comprising fructose and maltodextrin was ingested every 20 min via commercial drink, gel, bar, or mix of all 3, providing 80 g carbohydrate·h-1. Fluid ingestion was 705 ml·h-1. Exertion, fatigue, and gastrointestinal discomfort were measured with VAS. Performance peak power (SD) was 370 (41), 376 (37), 362 (51) and 368 W (54) for drink, gels, bars, and mix respectively. The reduction in power (-3.9%; 90%CI ±4.3) following bar ingestion vs. gel was likely substantial (likelihood harm 81.2%; benefit 0.8%), but no clear differences between drinks, gels, and the mix were evident. Bars also produced small-moderate standardized increases in nausea, stomach fullness, abdominal cramps, and perceived exertion, relative to gels (likelihood harm 95–99.5%; benefit <0.01%) and drink (75–95%; <0.01%); mix also increased nausea relative to gels (95%; <0.01%). Relative to a gel, carbohydrate bar ingestion reduced peak power, gut comfort, and ease of exertion; furthermore, no clear difference relative to drink suggests bars alone are the less favorable exogenous-carbohydrate energy source for intense endurance performance.
Bryan Saunders, Craig Sale, Roger C. Harris, and Caroline Sunderland
To determine whether gastrointestinal (GI) distress affects the ergogenicity of sodium bicarbonate and whether the degree of alkalemia or other metabolic responses is different between individuals who improve exercise capacity and those who do not.
Twenty-one men completed 2 cycling-capacity tests at 110% of maximum power output. Participants were supplemented with 0.3 g/kg body mass of either placebo (maltodextrin) or sodium bicarbonate (SB). Blood pH, bicarbonate, base excess, and lactate were determined at baseline, preexercise, immediately postexercise, and 5 min postexercise.
SB supplementation did not significantly increase total work done (TWD; P = .16, 46.8 · 9.1 vs 45.6 · 8.4 kJ, d = 0.14), although magnitude-based inferences suggested a 63% likelihood of a positive effect. When data were analyzed without 4 participants who experienced GI discomfort, TWD (P = .01) was significantly improved with SB. Immediately postexercise blood lactate was higher in SB for the individuals who improved but not for those who did not. There were also differences in the preexercise-to-postexercise change in blood pH, bicarbonate, and base excess between individuals who improved and those who did not.
SB improved high-intensity-cycling capacity but only with the exclusion of participants experiencing GI discomfort. Differences in blood responses suggest that SB may not be beneficial to all individuals. Magnitude-based inferences suggested that the exercise effects are unlikely to be negative; therefore, individuals should determine whether they respond well to SB supplementation before competition.