We are going look at how to decrease or increase your maximal glycolytic rate.
In simple terms, this is the maximum rate at which you can produce energy by breaking down carbohydrates in a process known as glycolysis. This isn’t to be confused with VLaMax which is the maximum rate of lactate production, however it is closely related to the maximal glycolytic rate.
In this post we are going to review key training approaches, workout designs and nutritional strategies that are needed to build a training program that can develop or suppress glycolysis as needed to achieve the optimal balance for the specific demands of a particular cycling event or discipline.
Firstly, though why you might want to increase or decrease your maximal glycolytic rate? To understand this, we need to look at the Impact of your glycolytic rate on performance.
The body has several energy systems that can be used to generate energy, and these pathways are always in use concurrently. Depending on the intensity and duration of the effort, these different energy systems will contribute to greater or lesser extents.
‘Glycolysis’ is one of the fastest energy pathways and is one of several ‘anaerobic’ processes that do not require oxygen to facilitate the rapid production of ATP, the body’s energy currency. Athletes who compete in short duration, high intensity events require a high maximal glycolytic rate to enable rapid energy production. A perfect example of this is track cycling or a sprinter over 100/200/400m.
In these events, a significant portion of the total energy produced throughout is provided by the glycolytic system, meaning athletes need a high rate of glycolysis (break down of glycogen, the body’s storage form of glucose) to keep up with this high energy demand.
One limitation of having a high glycolytic rate is that this can lead to a reduced ‘fractional utilisation’. Fractional utilisation is the percentage of your aerobic capacity (i.e. VO2max) at which your threshold power sits. A high glycolytic rate can have a detrimental impact on fractional utilisation, as it will generally lead to a higher rate of production of lactate and associated metabolites that have been linked with fatigue. When oxygen supply is insufficient, this can lead to an accumulation of lactate and fatigue-signalling metabolites.
In very short duration disciplines, the fractional utilisation IS NOT the primary determinant of performance (though still important). Therefore, in short disciplines, having a high glycolytic rate is usually desirable.
For athletes competing in longer duration disciplines fractional utilisation IS one of the key predictors of success. In this case, a lower maximal glycolytic rate is generally more desirable, and training may often focus on reducing the maximal glycolytic rate to raise threshold power and fractional utilisation.
The extent to which the glycolytic system should be developed also depends upon the size of the aerobic capacity (also known as VO2max). This is because the aerobic system influences how quickly lactate and associated fatiguing metabolites can be cleared, and thus how great a rate of glycolysis can be tolerated without rapid fatigue. Athletes with a higher aerobic capacity can tolerate a higher glycolytic rate than those with a lower aerobic capacity.
Increasing Glycolytic Rate
The following training methods can be used to increase the maximal glycolytic rate to the required level:
High glycogen availability
The body uses the most easily accessible substrate available to it. So training with high levels of muscle glycogen can promote use of the glycolytic energy system during exercise, and thereby train the body to metabolise carbohydrate more effectively. Glycogen stores can be topped up by consuming a relatively high daily intake of carbohydrates (between 6-12g of carbohydrates per kg body weight, depending on your overall energy needs). It can also be beneficial to eat a carbohydrate-rich meal or snack containing between 1-2g of carbohydrates per kg of body weight 2-4 hours before your training session to make sure your blood glucose levels are also high.
Very short sprints <5 seconds will primarily use the phosphocreatine energy system, which is a different pathway to the glycolytic system. However, sprint efforts longer than this (such as 10-30 second all-out bursts), will encourage a very high rate of glycolysis and train the body’s ability to produce energy via this pathway. We recommend taking relatively long recoveries between these high-power bursts (e.g. several minutes) to make sure you’re able to maximise your power over each effort.
Including very fast, explosive strength training into a program will help to activate a greater number of Type II (fast twitch) muscle fibres, which in turn will enable a larger proportion of glycolytically-inclined muscle fibres to be recruited. Such movements should be repeated quickly and recovery time kept low to avoid replenishment of creatine phosphate and its contribution to energy production.
Tailored gym training
Specifically designed strength training in the gym can also promote the use of glycolysis. Sets that use relatively high weight (not so heavy to cause complete failure), feature no significant in-set recovery time and use relatively short set durations (e.g. <10 reps per set) are ideal.
High power efforts
Training sessions that feature a series of intervals in the neighbourhood of 45-90 seconds each will also serve to raise glycolytic activity and train the production of lactate. There will be a greater contribution of the aerobic system in these longer efforts, but this will remain a very effective workout design for development of glycolysis.
Decreasing Glycolytic Rate
When the maximal glycolytic rate needs to be reduced, the main training methods that can be used are:
Low Glycogen Availability
One of the best means of training the body to rely less on glycolysis for the production of energy is to restrict its availability to glycogen and force the combustion of fat as the primary fuel source. Performing low intensity rides on a weekly basis in low-carbohydrate availability state is a simple but effective way to tip the aerobic-anaerobic balance favourably.
When there are long periods between training sessions, such as with those athletes who can only train around the weekend, the tendency is for aerobic adaptations to degrade and anaerobic adaptations (such as tendency for glycolysis) to become more dominant. Therefore, consistent training day after day is one of the best ways to reduce reliance on glycolysis.
A key factor that contributes to maximal glycolytic rate is muscle fibre composition, where Type IIa and Type IIx are generally more inclined towards anaerobic energy pathways (including glycolysis), and are generally less effective at producing energy through aerobic pathways.
However, it’s possible to train Type IIa fibres to become more aerobically efficient, and in particular to become better adapted to use fats for fuel instead of glycolysis.
By training at intensities just below the lactate threshold, it is possible to recruit a portion of Type IIa fibres and turn them into muscle fibres that possess qualities more akin to the Type I fibres, making them more aerobically capable and better able to use fat oxidation for energy production.
These sweetspot sessions can be usefully combined with carbohydrate restriction to further enhance the stimulus for improved fat oxidation.
Low cadence/high torque
Sweetspot training (or slightly lower Zone 3 training) can also be performed at a low cadence to further augment the training benefits. Riding at a low cadence increases the force demands on the muscles, which in turn leads to greater recruitment of Type IIa muscle fibres, helping to bring about aerobic adaptations within a greater proportion of these muscle fibres.
Finally, here are some final points that may be helpful in the context of fine tuning your maximal glycolytic rate:
It is important not to lose sight of the need for a perpetually strong aerobic capacity. The higher the aerobic capacity, the more energy can be produced without accumulation of fatiguing metabolites. You can think of the aerobic capacity as providing an important base to any effort on the bike. This is true even for relatively short efforts lasting just several minutes.
Furthermore, the stronger the aerobic capacity, the greater the ability to clean up the fatiguing products of glycolysis, meaning that hard efforts with a significant reliance on the glycolytic system can be sustained for longer.
Seeing meaningful increases in aerobic capacity can take months and years, and this fact means that it is something to work on constantly throughout the training cycle. In contrast, maximisation of the glycolytic rate, especially towards a level that is optimal in endurance competition can be achieved in a matter of weeks. Thus, training to develop glycolysis often should not be integrated too early and certainly not be overdone. If you’re looking to build a high maximal glycolytic rate, then you should also make sure you build in enough time training your aerobic capacity and other aerobic abilities beforehand, to make sure you can tolerate and deal with the high glycolytic rate and associated fatiguing metabolites.