Oxidation of Carbohydrates - One of the Keys to Athletic Performance
As an athlete, we are all curious to find the magic bullet – always trying to extend our knowledge base on what will help us perform better. One of the biggest controversies is over the hype of carbohydrates one should be consuming during and after competition. With this in mind we need to back up to what are we providing fuel for and why?
The misconception is that what we are consuming is to fuel the muscles – and although partially correct, the main reason we are consuming carbohydrates is to provide glucose to our brain. Our brains only fuel source is glucose and during exercise it can consume around 3-5 grams per minute depending on intensity of exercise. The body provides glucose via the blood at a constant rate and therefore is constantly being drained of its glucose source primarily by the brain; so here in-lies the problem to resolve.
Our bodies ability to metabolize carbohydrate is dependent on the type of carbs and “gastric emptying“, (the process of digestion where the stomach releases food into the body) and osmolarity plays a major role of how this is done. The rate of oxidation, meaning how fast carbohydrates are delivered as glucose into the bloodstream is dependent upon gastric emptying and the following:
Particle size, as in simple sugars aka (dextrose/glucose, single chain) is fast and complex carbohydrates aka (maltodextrins or multi chain) are slower.
Osmolarity, the number of particles in solution.
Using certain carbohydrates in mixtures such as glucose and fructose will speed up the rate of oxidation. Other factors that will speed up oxidation rates are adding nutrients such as vitamins B3 in specific forms and/or caffeine, theobromine etc... So if the brain burns at a rate of 3-5 grams per minute the end goal is to at least match or exceed the rate of delivery – right?
Example: Using maltodextrins as your primary source achieves a slower oxidation rate (.75 grams per minute) combined with the brains burning rate of 3-5 grams per minute creates a deficit in which the brain will not function unless supplied with glucose. Hence “The Bonk” ---. The brain tells the liver to get glucose from muscle glycogen for extra delivery and when the muscle is left with lower stores which leads to enhanced muscle fatigue. So --- --- --- --- is to achieve a higher rate of oxidation as to delay the onset of muscular fatigue, which leaves you, the athlete with more energy at the end of training or competition. This also achieves less overall fatigue in the CNS hence there is less of a delay of glucose being delivered to the brain (see “CNS Fatigue”). Below is a chart of oxidation rates of different mixtures of carbohydrates and micronutrients.
| Carbohydrate |
Oxidation Rate |
Consumpiton Rate |
Osmolarity |
| Dextrose/Fructose - mixture |
1.75 grams/minute |
1.8 grams /minute |
6-7% |
| Maltodextrin/Fructose/dextrose - mixture |
1.25 grams/minute |
1.8 grams /minute |
6-7% |
| Dextrose/Sucrose - mixture |
1.25 grams/minute |
1.8 grams /minute |
6-7% |
| Sucrose |
1.15 grams/minute |
2.44 grams /minute |
6-7% |
| Maltodextrin/Sucrose - mixture |
.98 grams/minute |
2.0 grams /minute |
6-7% |
| Dextrose/Glucose |
.95 grams/minute |
2.44 grams /minute |
6-7% |
| Fructose |
.89 grams./minute |
2.44 grams /minute |
6-7% |
| Maltodextrin - DE 18 |
.75 grams/minute |
2.44 grams /minute |
6-7% |
When deciding on a sports drink it’s easy to see with this concept in mind why we have the carbohydrates we do in Rapidade™. It is a far superior delivery system, easier on the stomach, no need for artificial sweeteners, and will keep you fueled and replenished during and after exercise. Related articles: “Gastric Emptying” - GI distress during exercise.
High rates of exogenous carbohydrate oxidation from a mixture of glucose and fructose ingested during prolonged cycling exercise.
Jentjens RL, Jeukendrup AEHuman Performance Laboratory, School of Sport and Exercise Sciences, University of Birmingham, Edgbaston B15 2TT, UK.A recent study from our laboratory has shown that a mixture of glucose and fructose ingested at a rate of 1.8 g/min leads to peak oxidation rates of approximately 1.3 g/min and results in approximately 55% higher exogenous carbohydrate (CHO) oxidation rates compared with the ingestion of an isocaloric amount of glucose. The aim of the present study was to investigate whether a mixture of glucose and fructose when ingested at a high rate (2.4 g/min) would lead to even higher exogenous CHO oxidation rates (>1.3 g/min). Eight trained male cyclists (VO2max: 68+/-1 ml/kg per min) cycled on three different occasions for 150 min at 50% of maximal power output (60+/-1% VO2max) and consumed either water (WAT) or a CHO solution providing 1.2 g/min glucose (GLU) or 1.2 g/min glucose+1.2 g/min fructose (GLU+FRUC). Peak exogenous CHO oxidation rates were higher (P<0.01) in the GLU+FRUC trial compared with the GLU trial (1.75 (SE 0.11) and 1.06 (SE 0.05) g/min, respectively). Furthermore, exogenous CHO oxidation rates during the last 90 min of exercise were approximately 50% higher (P<0.05) in GLU+FRUC compared with GLU (1.49 (SE 0.08) and 0.99 (SE 0.06) g/min, respectively). The results demonstrate that when a mixture of glucose and fructose is ingested at high rates (2.4 g/min) during 150 min of cycling exercise, exogenous CHO oxidation rates reach peak values of approximately 1.75 g/min.
High oxidation rates from combined carbohydrates ingested during exercise.
Jentjens RL Achten J Jeukendrup AEHuman Performance Laboratory, School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, United Kingdom.Studies that have investigated oxidation of a single carbohydrate (CHO) during exercise have reported oxidation rates of up to 1 g x min(-1). Recent studies from our laboratory have shown that a mixture of glucose and sucrose or glucose and fructose ingested at a high rate (1.8 g x min(-1)) leads to peak oxidation rates of approximately 1.3 g x min(-1) and results in approximately 20 to 55% higher exogenous CHO oxidation rates compared with the ingestion of an isocaloric amount of glucose. PURPOSE: The purpose of the present study was to examine whether a mixture of glucose, sucrose and fructose ingested at a high rate would result in even higher exogenous CHO oxidation rates (>1.3 g x min(-1)). METHODS: Eight trained male cyclists (VO2max: 64 +/- 1 mL x kg(-1) BM x min(-1)) cycled on three different occasions for 150 min at 62 +/- 1% VO2max and consumed either water (WAT) or a CHO solution providing 2.4 g x min(-1) of glucose (GLU) or 1.2 g x min(-1) of glucose + 0.6 g x min(-1) of fructose + 0.6 g x min(-1) of sucrose (MIX). RESULTS: High peak exogenous CHO oxidation rates were found in the MIX trial (1.70 +/- 0.07 g x min(-1)), which were approximately 44% higher (P < 0.01) compared with the GLU trial (1.18 +/- 0.04 g x min(-1)). Endogenous CHO oxidation was lower (P < 0.05) in MIX compared with GLU (0.76 +/- 0.12 and 1.05 +/- 0.06 g x min(-1), respectively). CONCLUSION: When glucose, fructose and sucrose are ingested simultaneously at high rates (2.4 g x min(-1)) during cycling exercise, exogenous CHO oxidation rates can reach peak values of approximately 1.7 g x min(-1) and estimated endogenous CHO oxidation is reduced compared with the ingestion of an isocaloric amount of glucose.
Oxidation of combined ingestion of glucose and sucrose during exercise.
Jentjens RL Shaw C Birtles T Waring RH Harding LK Jeukendrup AEHuman Performance Laboratory, School of Sport and Exercise Science, University of Birmingham, Birmingham B15 2TT, UK.The first purpose of the study was to examine whether combined ingestion of glucose and sucrose at an intake rate of 1.2 g/min would lead to higher oxidation rates compared with the ingestion of an isocaloric amount of glucose or sucrose alone. The second aim of the study was to investigate whether a mixture of glucose and sucrose when ingested at a high rate (2.4 g/min) would result in exogenous CHO oxidation rates higher than 1.2 to 1.3 g/min. Eight trained cyclists (maximal oxygen consumption: 64 +/- 2 mL . kg -1 . min -1 , mean +/- SE) performed 5 exercise trials in random order. Each trial consisted of 120 minutes of cycling at 50% maximum power output (63% +/- 2% maximal oxygen consumption), whereas subjects received a solution providing either 1.2 g/min of glucose (GLU), 1.2 g/min of sucrose (SUC), 0.6 g/min of glucose + 0.6 g/min of sucrose (M-GLU+SUC), 1.2 g/min of glucose + 1.2 g/min of sucrose (H-GLU+SUC), or water (WAT). Peak exogenous CHO oxidation rates in the H-GLU+SUC trial (1.20 +/- 0.07 g/min) were significantly higher ( P < .01) compared with the GLU, M-GLU+SUC, and SUC trials (0.77 +/- 0.04, 0.90 +/- 0.07, 0.98 +/- 0.04 g/min, respectively). Furthermore, peak exogenous CHO rates in M-GLU+SUC and SUC trials were significantly higher ( P < .05) compared with the GLU trial. In conclusion, combined ingestion of moderate amounts of glucose and sucrose (144 g) during cycling exercise resulted in approximately 21% higher exogenous CHO oxidation rates compared with the ingestion of an isocaloric amount of glucose. Furthermore, when a mixture of glucose and sucrose was ingested at high rates (2.4 g/min), exogenous CHO oxidation rates reached peak values of approximately 1.20 g/min.
Oxidation of exogenous glucose, sucrose, and maltose during prolonged cycling exercise.
Jentjens RL Venables MC Jeukendrup AEHuman Performance Laboratory, School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.The purpose of the present study was to investigate whether combined ingestion of two carbohydrates (CHO) that are absorbed by different intestinal transport mechanisms would lead to exogenous CHO oxidation rates of >1.0 g/min. Nine trained male cyclists (maximal O(2) consumption: 64 +/- 2 ml x kg body wt(-1) x min(-1)) performed four exercise trials, which were randomly assigned and separated by at least 1 wk. Each trial consisted of 150 min of cycling at 50% of maximal power output (60 +/- 1% maximal O(2) consumption), while subjects received a solution providing either 1.8 g/min of glucose (Glu), 1.2 g/min of glucose + 0.6 g/min of sucrose (Glu+Suc), 1.2 g/min of glucose + 0.6 g/min of maltose (Glu+Mal), or water. Peak exogenous CHO oxidation rates were significantly higher (P < 0.05) in the Glu+Suc trial (1.25 +/- 0.07 g/min) compared with the Glu and Glu+Mal trials (1.06 +/- 0.08 and 1.06 +/- 0.06 g/min, respectively). No difference was found in (peak) exogenous CHO oxidation rates between Glu and Glu+Mal. These results demonstrate that, when a mixture of glucose and sucrose is ingested at high rates (1.8 g/min) during cycling exercise, exogenous CHO oxidation rates reach peak values of approximately 1.25 g/min.