König, D., Zdzieblik, D., Holz, A., Theis, S., & Gollhofer, A. (2016). Substrate Utilization and Cycling Performance Following Palatinose™ Ingestion: A Randomized, Double-Blind, Controlled Trial. Nutrients, 8(7), 390. doi:10.3390/nu8070390
Introduction: Carbohydrate and fats are the primary energy source during exercise. High carbohydrate (CHO) diets and ingestion during prolonged endurance exercise significantly improve performance. There are certain situations in which endurance athletes may benefit from reduced CHO oxidation and increased fat utilization. This includes phases of training in which fat metabolism is desired as well as endurance competitions performed in the aerobic range. Metabolically, the human body is flexible and can switch between utilizing fat and CHO. Macronutrient breakdown plays an important role in substrate utilization, with higher CHO diets utilizing glucose and higher fat diets utilizing ketones. Glycemic index (GI) can also play an important role in substrate utilization, with a lower GI diet resulting in increased fat oxidation. Isolmaltulose is a disaccharide with glucose and fructose linked by a 1-6 glycosidic bond. This bond results in a slow breakdown of the CHO and low GI. Therefore, the aim of this research study was to examine the influence of isomaltulose (Palintinose) vs. maltodextrin ingestion on substrate utilization during endurance exercise and time trial performance in trained cyclists.
Purpose: To elucidate whether isomaltulose ingestion prior to exercise would favor fat oxidation during endurance exercise leading to glycogen sparing in the muscle and liver. The increased glycogen stores would then facilitate performance in the time trial.
Subject Description: Twenty male athletes participated in the study (29 +/- 3 years; weight 75.6 kg +/- kg; height 183 +/- 1.1 cm; VO2 max 61.3 +/- 1 ml/kg/min). Eligibility for the study included if the subjects were experienced endurance cyclists (VO2 > 55 ml/kg/min) and have participated in previous tests on cycling ergometers with time trial events and were healthy. A medical exam and blood testing was performed prior to the study.
This studies subject description lacks details. The recruitment methods were left out, leaving the reader to wonder how they obtained these volunteers. Another interesting detail was the selection of trained cyclists via VO2 rather than years experienced. It is plausible the subjects may not have significant experience but maintain a high VO2 via other aerobic training. This would qualify the individual for this study. In my opinion, the VO2 requirement is a good component, but additionally including the training experience years would make a better argument for trained cyclists. The authors did justify the sample size by using a probabilistic magnitude based inference. The study size was determined by examining post-only crossover trials. The magnitude of the effect was tested against the standardized Cohen change of 0.2 times between conditions. Classification of Cohen’s effect size scores were 0-0.2 trivial, 0.2-0.6 small, 0.6-1.2 large, and very large >2.0. The coefficient of variation for finishing time and power output have been determined previously at 1.5% and 3.6%. Confidence intervals for substantial increase or decrease were as follows: <0.5% almost certainly not, 1%-5% very unlikely, 5%-25% unlikely, 25%-75% possibly, 75%-95% likely, and >99.5% almost certainty. An effect was declared beneficial if the odds ratio of beneficial/non-beneficial was > 66.
This section was done thoroughly, providing detail and justification for the authors sample size. The authors also provided details on the statistical methods they used to analyze the data. This gives the reader a good idea of what to expect in the results section and eliminates the reader from having to perform any statistical guesswork. I thought this section was well throughout and detail-oriented. I like the inclusion of effect sizes. In my opinion, exercise studies should almost unanimously reports both significance and effect sizes. Effect sizes give the reader a greater understanding of the magnitude of the results.
Methods: This study was designed in a randomized, double-blind, controlled cross-over design. The study included 4 laboratory sessions (2 preliminary followed by 2 experimental trials). The first session included a VO2 max test using a ramp protocol (cycling 3 min at 100 W and 3 min at 150 W, then increases of 10 W/ 10 s until exhaustion. The second session was a familiarization session. The subjects performed a pre-test with a commercial sports beverage to familiarize with the exercise protocol and beverage consumption. The final two sessions consisted of subjects ingesting 750 mL of a beverage containing either 75 g isomaltulose (Palatinose, PSE) or maltodextrin (MDX). Both drinks were identical in terms of taste and appearance. The ingestion of the beverage occurred after an overnight fast 45 minutes prior to exercise. Randomization of the drinks occurred via an outside person not involved in the conduct of the study. Exercise consisted of 90 minutes of endurance cycling (60% VO2 max) as determined during the first session. Upon completion, a time trial test commenced. The time trial was considered completed when 6.5 kJ/kg bodyweight was achieved. Subjects were instructed to complete the test as fast as possible. The evening prior to the tests the subjects consumed a standardized meal at 7 pm consisting of pasta (670 kcal, 21.5 g protein, 61.5 g carbohydrate, 38.5 g fat). Primary outcome for the study was the time required to finish the time trial. Secondary outcomes included power output during the time trial and physiological parameters including blood glucose and lactate concentrations. Blood was drawn at time intervals of 45, 30, and 15 min pre-test. Additional draws were done at 0 min, and 15, 30, 45, 60, 75, and 90 min post-test. These draws were capillary blood samples and were analyzed for blood glucose and lactate via enzymatically with ESAT 6600. VO2 and carbon dioxide production were determined over 3 minute intervals during pretest time intervals of 45, 30, 15, and 0 min as well as at time intervals during the endurance test of 0, 15, 30, 45, 75, and 90 min. The respiratory quotient was calculated and energy expenditure and substrate oxidation were determined according to the equation of Weir. Heart rate was also recorded throughout the experiment.
Results: All 20 subjects completed the study. Spirometric data was missing from 3 subjects, resulting in substrate utilization evaluation in n=17. The time to complete the time trial was 31.08 +/- 6.27 min for the MDX and 30.05 +/- 4.7 min for the PSE trial. This difference resulted in a likely small (89% likelihood) to moderate (77% likelihood) benefit of Palatinose. Power output was also higher in PSE vs. MDX, but this was only clinically relevant in the final 5 minutes of the time trial (290.61 +/- 45.85W vs. 279.42 +/- 55.91 W). The higher output resulted in a mean change of 0.8% (90% CI+/-2.8%, p=0.608) and 2.0% (90% CI +/- 3.5%, p=0.327). Analysis of the final 5 minutes revealed PSE produced higher power output by 4.6% (90% CI +/- 4.0%, p=0.053), which is a likely small benefit of Palatinose. Blood glucose significantly differed between trials (p=0.013). At rest and at 30, 15, and 0 min prior to exercise, ingestion of PSE resulted in lower blood glucose concentrations compared to MDX (99% likelihood, ES=-0.61 to -0.87 moderate effect, p>0.05 for all time points). The reduction in glycemia following the onset of exercise was attenuated with PSE (93% likelihood, ES=0.64, moderate effect, p=0.034). Fat and carbohydrate oxidation differed between the MDX and PSE trial (p=0.005 and p=0.002). During endurance exercise, PSE resulted in higher fat oxidation (88 to 99% likelihood, ES=0.65 to 1.60, moderate to large effect, p <0.05 for all time points 30-90 min) and lower carbohydrate oxidation compared with MDX (85% to 96% likelihood, ES=-0.44 to -0.63, small to moderate effect, p <0.05 for all time points 0-75 min). Total energy expenditure was not significantly different between trials.
The authors did an excellent job of reporting the results. Not only did they include tests of statistical significance, but they included effect sizes, confidence intervals, and likelihood rations. The latter of these statistical measures is often more useful to clinicians because they help decipher the magnitude of change. For example, a reader interested in Palatinose to improve performance would see the benefit of approximately 1 minute and understand the ingestion results in a likely small to moderate benefit. Depending on the athlete, the magnitude of this change may or may not be substantial enough for them to warrant Palatinose ingestion. It gives the reader a much better picture of “how” much Palatinose impacts performance. If only statistical significance was calculated, the reader would only if the results reached a certain p level, not the magnitude. In addition, the methods section was done well. The use of a randomized cross-over design increases the power of the study by reducing variability as the same subjects are in each condition. The methods were thoroughly detailed, which would allow the use of their protocol for future studies. Overall, the results and methods sections was very thorough, and the authors did a good job of really analyzing and interpreting the data.
Discussion: The main finding of this study was cycling time trial was 30.05 +/- 4.70 min following Palatinose and 31.08 +/- min following maltodextrin. The effect size of 1 min did not reach statistical significance, but the authors argue the magnitude of the change is impressive and results in a likely benefit of Palatinose. Furthermore, there was a likely benefit for power output and increased fat oxidation and reduced carbohydrate oxidation following Palatinose ingestion. The ingestion of Palatinose demonstrated a superior glucose response resulting in sustained blood glucose levels throughout exercise. The maintenance of fat oxidation during submaximal exercise resulted in glycogen sparing. This is speculated to result in improved endurance performance, which was demonstrated in the time trial following the endurance session. Also noted was Palatinose attenuated the exercise-induced rebound glycemic response, which can be contributed its slow digesting nature and increased fat utilization.
Conclusion/Limitations: In conclusion, this study demonstrated ingestion of Palatinose may improve substrate utilization and time trial performance following an endurance bout. Limitations to this study include lack of details in recruitment, small sample size, and lack of hormone measures. Overall, the results section was done with excruciating detail, providing the reader with practical knowledge of the study’s impact.
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