Pre-Workout Nutrition & Supplementation for Athletes - What Works, What Doesn't Work | Perfect Timing, Fast or Slow Carbs, Glucose & Fructose, Fats, Protein & More

For sedentary, video-game and smartphone addicted youths, it's they're the gateway drug.. ah, I mean drink to insulin therapy for full-blown diabetes. For athletes CHO + caffeine containing drinks can be very useful.

As Michael J. Ormsbee and his colleagues point out in their latest review, "[e]ndurance athletes rarely compete in the fasted state, as this may compromise fuel stores." The means by which means endurance athletes (and anyone who is about to embark on a long(er) workout) should (pre-)fuel their workouts is yet still debated.

Some swear by whole foods, others stick to special carbohydrate mixes, others again combine carbohydrates and protein and many simply grab the next best energy drink or supplement with an allegedly "science-based" formula. What is optimal, however, isn't just determined by the amount of energy it delivers. It's also influenced by the metabolic effects of the preworkout meal.
Having a ton of fat, but no carbohydrates, for example, could steer an athletes metabolism away from carbohydrate and toward fat metabolism. For a sprinter this would be a disaster, for an endurance athlete, on the other hand, it could have certain benefits.

When I look at the tabular overview of the studies, Ormsbee et al. reviewed in their latest paper, there is yet another factor that appears to have an even greater impact on the benefits of pre-workout meals / supplementation and that's timing! In the discussion of their results, the South African researchers write.

Figure 1: Drop in glucose in well-trained cyclist on the onset of 30min cycling exercise after ingestion of 75g glucose or fructose or placebo (Koivisto. 1981)

"The timing of CHO intake influences its metabolic effects. Indeed, insulin and blood glucose elevations are positively correlated with CHO meal proximity to exercise (Moseley. 2003). Studies in which CHO is consumed 1–4 h prior to exercise often report glucose and insulin levels declining to near-basal levels prior to exercise (Coyle. 1985; Kotsiopoulou. 2002; Chen. 2009).

Alternatively, when subjects consume CHO ≤60 min before exercise, insulin and blood glucose levels are reported to be elevated immediately prior to exercise (Koivisto. 1981; Chryssanthopoulos. 1994; Febbraio. 2000a,b)." (Ormsbee. 2014)

What both the 1-4h prior and the <60 min pre-exercise approach have in common is that they trigger an initial drop in blood glucose at the onset of the exercise period. Interestingly, the latter is more pronounced for shorter time-spans between the ingestion of the meal / nutrient supplement and the workout.
In view of the aforementioned problem with reductions in blood glucose it should be obvious that consuming high glycemic index (high GI) carbohydrates before a race may not be ideal.

Figure 2: When they are ingested 30 min before an endurance exercise bouts, slow digesting carbohydrates (LGI) from muesli have no advantage over fast digesting carbs (HGI) from instant mashed potatoes [please not that this study also shows that it doesn't have to be Gatorade or other sugar water]; on the contrary, the lactate levels after the workout were lower and the total work was higher (albeit not significantly) in the HGI trial (Febbraio. 2000a)

The experimental evidence, on the other hand, shows that when the high GI meal (instant mashed potatoes) is consumed 30 minutes before the workout, there are no negative effects on the exercise performance of 8 trained men who cycled at 70% peak oxygen uptake for 120 min followed by a 30-min performance cycle (see Figure 2).

Fat burning machines train low and compete high!?

Similarly, the evidence for the usefulness of high fat feeding immediately before a competition isn't there (Ormsbee. 2014). Rather than that many endurance athletes who follow a lowe(er) carbohydrate diet, "train low" and "compete high" - in this case "high" and "low" don't refer to the altitude, thought, but indicate training with a low carbohydrate intake and increasing the carbohydrate intake shortly before a competition. Some experts see this critically, though. Louise M. Burke, for example, writes:

"More recently, it has been suggested that athletes should train with low carbohydrate stores but restore fuel availability for competition (‘‘train low, compete high’’), based on observations that the intracellular signaling pathways underpinning adaptations to training are enhanced when exercise is undertaken with low glycogen stores. The present literature is limited to studies of ‘‘twice a day’’ training (low glycogen for the second session) or withholding carbohydrate intake during training sessions. Despite increasing the muscle adaptive response and reducing the reliance on carbohydrate utilization during exercise, there is no clear evidence that these strategies enhance exercise performance. Further studies on dietary periodization strategies, especially those mimicking real-life athletic practices, are needed." (Burke. 2010; my emphasis)

In an article in the Journal of Sports Sciences Burke wrote with John A. Hawley, Stephen H. S. Wong & Asker E. Jeukendrup, the authors accordingly classify the "train low, compete high"-principle as principle with "equivocal evidence" (Burke. 2011).
More recent research again suggests that we may not even be dealing with an "either or" problem, here. In fact, an experiment Murakamiet al. conducted only recently would suggest:

Could using fat and carbs, instead of fat or carbs increase performance even more?

The scientist from the Fukuoka University examined the performance effect of consuming either: (1) a high-fat meal 4 h pre-exercise + a placebo jelly 3 min before exercise (HFM + P); (2) a high-fat meal 4 h pre-exercise + maltodextrin jelly 3 min before exercise (HFM+ M); or (3) a high-CHO meal 4 h pre-exercise + placebo jelly 3 min before exercise (HCM + P).

The study was conducted after the subjects, eight  male collegiate long-distance athletes, who engaged in physical training almost every day, had consumed an isocaloric, high-CHO diet for three days (2562 ± 19 kcal). The isocaloric test meals (1007 ± 21 kcal) were consumed 4 h before a standardized exercise test consisting of 80 min submaximal runing on a treadmill at each runner’s pre-determined lactate threshold (LT) speed.
The endurance component was immediately followed by a time trial to exhaustion (TTE), where the HFM + M group were able to run 8% (8 minutes) longer than their peers in the HFM + P  and the 10% longer than the HCM + P group. As Ormsbee et al. highlight in their review:

"This suggests that CHO feeding subsequent to a HFM pre-exercise and three days of a proper CHO loading protocol can elicit an enhancement in the endurance performance of well-trained runners.[...] however, Murakami and colleagues did not include a HCM + M group, which raises questions about whether the HFM + M group performed longer primarily due to HFM [i.e. due to the extra fat] or rather as a result of the increased caloric consumption of maltodextrin immediately pre-exercise." (Ormsbee. 2014)

It appears likely that this methodological issue renders the study results more or less worthless, because previous studies have found more or less unequivocally that fat and fat & carbohydrate supplements don't increase the exercise performance of endurance athletes:

• Figure 3: Next to changes in substrate oxidation (CHO ￬ | FAT ￪) the blunted growth hormone response was the only sign. difference Whitley et al. found when they compared a high carbohydrate to a high fat meal (Whitley. 1998)

  Whitley et al. (1998) who couldn't find a performance increase w/ 50g of carbohydrates, 14g protein and 80g fat during 90 min cycling 70% VO2max and a 10 km TT
• Okano, G., et al. (1996) who didn't find performance increases in response to the ingestion of a 30% carbohydrate, 61% fat and 9% protein meal 4h before an exercise test that consisted of cycling at 65% of the maximal oxygen consumption for the first 120 min of exercise, followed by an increased dose of 80 % V0_max,
• Rowlands et al. (2002) who found no benefits of consuming a high fat meal before a 50-km time trial, and
• Paul, et al. (2003) who found that even dosed at 1.3g/kg body weight a high fat meal has no effect on timetrial performance of 8 trained men.

Overall, the combination of fat and carbohydrates or the use of fat instead of carbohydrates does therefore appear similarly futile. What is important, though, is that having fats in your preworkout meal is not going to decrease your workout performance significantly. Moreover, it remains to be seen, whether the results differ in "fat adapted" athletes in future studies.

Caffeine & protein, the bodybuilder's darlings

Both caffeine and protein have been shown to be useful for endurance athletes, but only the former, i.e. caffeine supplements will lead to significant performance increases.

"Regardless of an athlete’s genetic disposition, a dose of 3–6 mg of caffeine/kg of body weight has been shown to enhance performance in most individuals, with no further benefit from higher doses." (Ormsbee. 2014)

For the latter, i.e. protein, the latest review clearly states that the contemporary evidence shows that

"[...] when carbohydrate supplementation was delivered at optimal rates during or after exercise, protein supplements provided no further ergogenic effect, regardless of the performance metric used." (McLellan. 2014)

What protein supplements can do, though, is to speed up the glycogen resynthesis and glycogen hypersaturation after workouts (Morifuji. 20045) and contribute and "enhance skeletal muscle remodelling and stimulate adaptations that promote an endurance phenotype" (Moore. 2014).
References:

• Burke, L. M. "Fueling strategies to optimize performance: training high or training low?." Scandinavian journal of medicine & science in sports 20.s2 (2010): 48-58.
• Burke, Louise M., et al. "Carbohydrates for training and competition." Journal of Sports Sciences 29.sup1 (2011): S17-S27.
• Casey, Anna, et al. "Effect of carbohydrate ingestion on glycogen resynthesis in human liver and skeletal muscle, measured by 13C MRS." American Journal of Physiology-Endocrinology And Metabolism 278.1 (2000): E65-E75.
• Chen, Y. J., et al. "Effects of glycemic index meal and CHO-electrolyte drink on cytokine response and run performance in endurance athletes." Journal of Science and Medicine in Sport 12.6 (2009): 697-703. 
• Coyle, Edward F., et al. "Substrate usage during prolonged exercise following a preexercise meal." J Appl Physiol 59.2 (1985): 429-33.
• Chryssanthopoulos, C., L. C. Hennessy, and C. Williams. "The influence of pre-exercise glucose ingestion on endurance running capacity." British journal of sports medicine 28.2 (1994): 105-109.
• Febbraio, Mark A., et al. "Effects of carbohydrate ingestion before and during exercise on glucose kinetics and performance." Journal of Applied Physiology 89.6 (2000a): 2220-2226.
• Febbraio, Mark A., et al. "Preexercise carbohydrate ingestion, glucose kinetics, and muscle glycogen use: effect of the glycemic index." Journal of Applied Physiology 89.5 (2000b): 1845-1851.
• Kotsiopoulou, Christina, and Veronica Vleck. "The effect of a high carbohydrate meal on endurance running capacity." International journal of sport nutrition and exercise metabolism 12 (2002): 157-171.
• Koivisto, Veikko A., Sirkka-Lisa Karonen, and Esko A. Nikkila. "Carbohydrate ingestion before exercise: comparison of glucose, fructose, and sweet placebo." J Appl Physiol 51.4 (1981): 783-787. 
• McLellan, Tom M., Stefan M. Pasiakos, and Harris R. Lieberman. "Effects of Protein in Combination with Carbohydrate Supplements on Acute or Repeat Endurance Exercise Performance: A Systematic Review." Sports Medicine 44.4 (2014): 535-550.
• Moseley, Luke, Graeme I. Lancaster, and Asker E. Jeukendrup. "Effects of timing of pre-exercise ingestion of carbohydrate on subsequent metabolism and cycling performance." European journal of applied physiology 88.4-5 (2003): 453-458.
• Moore, Daniel R., et al. "Beyond muscle hypertrophy: why dietary protein is important for endurance athletes 1." Applied Physiology, Nutrition, and Metabolism 39.999 (2014): 1-11.
• Morifuji, Masashi, et al. "Dietary whey protein increases liver and skeletal muscle glycogen levels in exercise-trained rats." British journal of nutrition 93.04 (2005): 439-445.
• Murakami, Ikuma, et al. "Significant effect of a pre-exercise high-fat meal after a 3-day high-carbohydrate diet on endurance performance." Nutrients 4.7 (2012): 625-637.
• Okano, G., et al. "Effect of 4h preexercise high carbohydrate and high fat meal ingestion on endurance performance and metabolism." International journal of sports medicine 17.07 (1996): 530-534.
• Ormsbee, Michael J., Christopher W. Bach, and Daniel A. Baur. "Pre-Exercise Nutrition: The Role of Macronutrients, Modified Starches and Supplements on Metabolism and Endurance Performance." Nutrients 6.5 (2014): 1782-1808.
• Paul, David, et al. "No effect of pre-exercise meal on substrate metabolism and time trial performance during intense endurance exercise." International journal of sport nutrition and exercise metabolism 13 (2003): 489-503.
• Rowlands, David S., and Will G. Hopkins. "Effect of high-fat, high-carbohydrate, and high-protein meals on metabolism and performance during endurance cycling." International journal of sport nutrition and exercise metabolism 12 (2002): 318-335.
• van Loon, Luc JC, et al. "Maximizing postexercise muscle glycogen synthesis: carbohydrate supplementation and the application of amino acid or protein hydrolysate mixtures." The American journal of clinical nutrition 72.1 (2000): 106-111.
• Volek, Jeff S., Timothy Noakes, and Stephen D. Phinney. "Rethinking fat as a fuel for endurance exercise." European journal of sport science ahead-of-print (2014): 1-8. 
• Whitley, Helena A., et al. "Metabolic and performance responses during endurance exercise after high-fat and high-carbohydrate meals." Journal of Applied Physiology 85.2 (1998): 418-424.