Glycolysis and Metabolic Optimization: Workout Strategies to Get the Most From Your Metcon

Michael McCastle


Endurance Sports, Sports Psychology, Personal Training, Strength and Conditioning


Physical performance, regardless of whether it is working out at the gym, laboring in the fields, or running a marathon, takes much more than determination and training. Nutrition is an essential key to optimum training and peak physical performance, which is why so many athletes and gym enthusiasts take their diets seriously. There is plenty of science behind food intake as it relates to physical performance, and entire career paths are dedicated to this study.


One such path the study of glycolysis, which is the body’s method to convert glucose to pyruvate. In layman’s terms, glycolysis is the body’s process of breaking down carbohydrates into acids that your body uses to sustain itself during physical performance.



Everyone who participates in physically demanding activities should understand how their food intake can impact their real-world ability. Knowledge of the effects of meal frequency and timing with reference to physical performance, as well as the intricacies of metabolic optimization, will increase physical prowess and performance gains.


Fuel Before the Clock Starts

Pre-workout nutrition is incredibly important for the overall quality of physical performance, as well as lasting endurance. A 2014 research review found that:


“Carbohydrate feedings prior to endurance exercise are common and have generally shown to enhance performance, despite increasing insulin levels and reducing fat oxidation. These metabolic effects may be attenuated by consuming low glycemic index carbohydrates and/or modified starches before exercise. High fat meals seem to have beneficial metabolic effects.”1


Simply put, eating meals with a high concentration of carbs with a low glycemic index, as well as modified starches, is perhaps the best way to ready yourself for physical performance. Through glycolysis, these carbohydrates are transformed into beneficial acids that help propel the body forward, increasing your capacity for endurance and intensity, resulting in a much more satisfactory workout. While eating meals rich in carbs is not a necessity, it certainly does help, and is much more beneficial when compared to working out on an empty stomach, in terms of raw performance. Pre-exercise meals should not be eaten directly before athletic ability, but should be eaten within one to two hours of activity, allowing the body to naturally digest and consume the carbs.


The Gray Area of Intra-Workout Nutrition

Metabolic optimization can also be increased by eating the right foods during physical performance. This is perhaps the most complex aspect of performance-enhancing nutrition, as there is not really a perfect time during physical activity to eat. According to Dr. Jenna Bell-Wilson:



“Succinct recommendations for carbohydrate intake during the energy phase or during activity are difficult to nail down…Research supports the use of carbohydrate during activity, but the amount and form are still foggy…Ingestion of protein during the energy phase may be advantageous in addition to carbohydrate”


Once again, carbohydrates are the primary means in which nutrition should be obtained during physical performance. However, the timing of the ingestion of nutrtition rich in carbohydrates is still hotly debated, and is heavily dependent on the duration and intensity of the activity. Those who choose to replenish themselves during physical performance find that liquids are much more advantageous than solid foods, as liquids are much easier to take in and keep down. They are also easier to absorb. That being said, what you eat and when you eat during physical activity is highly dependent on the individual and the sport.



It’s Not Over When It’s Over

Metabolic optimization can be enhanced even after physical performance has ceased. Post-workout nutrition is every bit as important as pre-workout and intra-workout nutrition, but there is a specific timeframe in which this nutrition should be consumed. An extensive 2013 review noted that:



“…when training is initiated more than ~3-4 hours after the preceding meal, the classical recommendation to consume protein (at least 25g) as soon as possible seems warranted in order to reverse the catabolic state, which in turn could expedite muscular recovery and growth.”2


The science here states that post-exercise nutrition is important, but it is less important if proper pre-exercise nutrition was heeded. In the event that pre-exercise nutrition was skipped or otherwise unattainable, then post-workout nutrition heavily favors proteins over carbohydrates. And not just that, but a rather large supplement of protein is favored in order to offset any naturally occurring muscular catabolism. With all of this in mind, it may not be a bad idea to engage in post-workout nutrition even if proper pre- and intra-workout nutrition was heeded; there certainly is no negative effect that can occur, so it is better to be overly safe than do nothing at all.


Get the Most From Your Metcon

Now that you have your pre-workout and intra-workout nutrition dialed in, let's look at how to maximize your time if your primary goal is metabolic conditioning. Nutrition alone can go a long way in preparing you for a great workout, but it can all be undone if your workout isn't just as dialed as your food intake. As with any form of exercise, it boils down to the SAID principle: specific adaptation to imposed demand.


There are a few tried-and-true strategies to maximize metabolism during your workout. One such strategy is high-intensity interval training (HIIT). HIIT has been shown to increase both fat and carbohydrate metabolism in human skeletal muscle.3 While there is research showing that, given unlimited time to train, steady-state cardio can be just as effective as HIIT for increasing both total metabolism and fat metabolism, the latter is the most time-efficient form of metabolic conditioning (metcon). In under 20 minutes, HIIT generates oxygen deficits (and thus increased fat metabolism) for a period of time extending after the workout. To achieve the same effect doing steady state cardio, it takes closer to 60 minutes.4


Manipulating rest periods will also enhance the effectiveness of metabolic conditioning by creating the progressive oxygen debt crucial for fat burning. Exact rest periods vary based on the fitness level and work capacity of the individual, but as a general rule of thumb, you should be breathing hard throughout the entire workout. Resting between 15 and 60 seconds between sets should work for the majority of people, and the "talk test" can be used to measure your effort level: if you can speak in complete sentences without taking a breath, you’re not quite working hard enough.


The take-home message from the research on metabolic conditioning boils down to two simple ideas: increase your intensity and decrease your rest to optimize your workout.



Physical performance is a combination of many factors. Perhaps chief among them is proper nutrition, occurring before, during, and after physical activity. Pre-workout nutrition should focus heavily on carbohydrate; intra-workout nutrition should focus on a combination of carbohydrates and proteins, and post-workout nutrition should focus heavily on proteins. By following this regimen, metabolic optimization through glycolysis should occur, resulting in more satisfactory physical performance. Making this a part of your routine will greatly improve your performance and guarantee a much more noticeable burn before, during, and after your workout.



1. 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, no. 5 (2014): 1782-1808.

2. Aragon, Alan Albert, and Brad Jon Schoenfeld. "Nutrient timing revisited: is there a post-exercise anabolic window?" Journal of the International Society of Sports Nutrition 10, no. 1 (2013): 5.

3. Perry, Christopher GR, George JF Heigenhauser, Arend Bonen, and Lawrence L. Spriet. "High-intensity aerobic interval training increases fat and carbohydrate metabolic capacities in human skeletal muscle." Applied Physiology, Nutrition, and Metabolism 33, no. 6 (2008): 1112-1123.

4. Skelly, Lauren E., Patricia C. Andrews, Jenna B. Gillen, Brian J. Martin, Michael E. Percival, and Martin J. Gibala. "High-intensity interval exercise induces 24-h energy expenditure similar to traditional endurance exercise despite reduced time commitment." Applied Physiology, Nutrition, and Metabolism 39, no. 7 (2014): 845-848.

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