Minimizing Muscle Soreness - SFuels Extended Substrate. How it Works.

Minimizing Muscle Soreness - SFuels Extended Substrate. How it Works.

Endurance athletes are more than well acquainted with post-workout muscle soreness, or whats commonly referred to as Delayed Onset Muscle Soreness (DOMS).

On the other hand, what has come as a surprise to SFuels athletes is how our ZONE 2 and ZONE 4 training products with Extended Substrate (See below) is materially reducing post-workout muscle soreness.


How is this working?

1) First - the Markers behind DOMS
As highlighted in the video (link here), the jury is still out on the mechanistic order of action - by which eccentric muscle contractions trigger DOMS.  That said, multiple research papers and random clinical trials have been consistent on heightened inflammatory markers found associated with DOMS, notably - Creatine Kinase (CK) and C-reactive protein (CRP).  CK an enzyme, and CRP a protein - these are markers of muscle damage and inflammation, but they are not the direct culprit behind your post-workout soreness.  Nevertheless, these markers are important in helping us understand and test how nutritional support can modulate the down-side effects of post-workout soreness, from all the eccentric muscle contractions in training.

2) What the studies say
In 2010, the British Medical Journal published a study (1) looking at Creatine Kinase and range of motion between a placebo group and an experimental group using Glutamine twice a day, 3 times per week, for 4 weeks.  The study abstract summarized the findings, where L-Glutamine attenuated the DOMS effect (lowered range of motion) and rise in CK serum levels.

In studies (2) on animals have also highlighted the anti-inflammatory effect of L-glutamine (and L-alanine) on key markers of inflammation and muscle damage following progressive resistance exercise. This included markers of CK, Tumor Necrosis Factor alpha (TNF-α), and various known Interleukin inflammatory mediators.  

In an interesting cross-over study (3) on athletes (basketballers), lower CK levels were noted during groups undergoing Glutamine supplementation (6grams/day for 20 days, before cross-over).  Interestingly, even adrenocorticotropic hormones which are typically secreted in response to stress and inflammation (by the pituitary gland) were lower in the glutamine-supplemented groups.

3) Empirical experience and dosage
SFuels began using and testing Glutamine in fueling formulas in 2018 and its recovery formulation (with whey isolate and Ketones) in 2021. However, in studies like those noted above and our own athlete-training testing, SFuels recognized that a critical dosage point is required for consistent, reproducible effects on post-workout muscle soreness.  From several years of product use and dosage by SFuels athletes customers, our recommended dosage range is between 4-10gr/day during days of endurance training. 

4) Need for a new ingredient - Extended Substrate
Based on our observations of studies and our athletes using our 1st generation training recovery formulations, SFuels began working on a new substrate. A new efficient glutamine delivery mechanism would be formed through a new ingredient innovation that is formed by binding specific medium-chain triglycerides to glutamine.  We call this Extended Substrate.  Now a patent-pending food ingredient, Extended Substrate is now the foundation of our 2nd Generation, SFuels ZONE 2, and ZONE 4 training and racing products. 

Prove the reduced muscle soreness yourself.
You can test the Extended Substrate effect on muscle soreness for yourself.  Simply schedule a known workout that for you, results in post-workout muscle soreness in the 24-48 hours following the workout.  Ideally, you should write down your rating of soreness and the range of motion for specific muscles involved in the exercise (running is a strong eccentric muscle contraction activity) at specific time points (4 hours, 8 hours, 24 hours etc.) post your workout.  Have 4-7 day washout period (no repeat of the workout), and then repeat the workout, but this time, using SFuels ZONE 2, or ZONE 4 during the workout.  Similarly, rate your soreness and range of motion to feel and note the difference. 

The Benefit
Clearly being able to take on heavy-load training, or training blocks with rapid day-to-day recovery is highly beneficial to consistent gains in aerobic-anaerobic training.  Using a fuel that not only fuels the metabolic adaptations during training, but also attenuates the inflammation of thee workout is a simple way to raise your training load, and support accelerated training gains.

Happy training and rapid recovery!  Leighton


(1) Somayeh Namdar Tajari et al. Assessment of the effect of L-Glutamine supplementation on DOMS. Dec, 2010.
(2) Raquel Raizel et al. Determination of the anti-inflammatory and cytoprotective effects of l-glutamine and l-alanine, or dipeptide, supplementation in rats submitted to resistance exercise. British Journal of Nutrition. May, 2016.
(3) Alfredo Cordova-Martinez et al. Effect of Glutamine Supplementation on Muscular Damage Biomarkers in Professional Basketball Players. Nutrients. Jun, 2021.

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