Muscle Fatigue Part 1 – Lactate and Hydrogen Ion build-up
We use the term fatigue to describe a general feeling of the overall effects of an exercise on the body or the inability to continue with an exercise. So what causes this sensation of fatigue? The reason has to do with several factors including the availability of fuel for the muscles and one of the factors we will discuss today being the mechanism of hydrogen ions in muscle cell action.
Muscles require ATP (adenosine triphosphate) as an energy source. During intense activity we rely on the anaerobic pathway but this has a limited store (ATP/CP pathway approximately 10 seconds and the Anaerobic Lactic pathway approximately 2 minutes). The aerobic pathway produces ATP copiously (with the breakdown of glucose and glycogen) and requires oxygen, carried by the blood, to support the process. The cardiovascular system is limited in its ability to deliver blood and oxygen to the working muscles.
The breakdown of glucose or glycogen produces lactate and hydrogen ions (H+). If insufficient oxygen is available to the working muscles then hydrogen ion concentrations increase and the blood and muscle become acidic. This acidic environment start to block the nerve signals from the brain to muscle fibres so the muscles begin to feel heavy and we slow down in order to allow more oxygen to get to the working muscles. Put simply, a drop in muscle pH is a major contributor to muscle fatigue.
Carnosine is one of your muscles' first lines of defence against the build-up of hydrogen ions (H+) during high-intensity exercise. This rise in H+ dramatically lowers the pH within muscle cells, negatively effecting enzyme function and muscle excitation-contraction coupling events that support continued, high-intensity output.
Think of Carnosine as the Gaviscon to the awful acid ingestion – it comes along and buffers the acid (putting the fire out so to speak), therefore delaying the onset of fatigue that is caused by the build-up of the hydrogen ions, allowing the exercise or activity to be carried out for a little while longer, and hence increasing/improving performance.
Muscle carnosine concentration is also linked with having a high percentage of Type II fast-twitch muscle fibers. For this reason, you'll find higher levels of muscle carnosine among sprinters and natural muscle freaks. Men also generally have higher muscle carnosine concentrations than women, most likely because the enzyme that breaks down carnosine is more active in women
So how do we raise our muscle carnosine levels?
The answer is simple – Beta Alanine supplementation.
Supplementing with beta-alanine will raise muscle carnosine concentrations. In fact, beta-alanine is the limiting amino acid in carnosine synthesis, meaning that its presence in the bloodstream is directly tied to muscle carnosine levels.
Supplementation with beta-alanine has been shown to increase muscle carnosine concentrations by up to 58 percent in just four weeks, and 80 percent in 10 weeks
What is Beta Alanine?
Beta-alanine, is a naturally-occurring beta-amino acid and a component of the histidine dipeptides carnosine and anserine, as well as vitamin B5.
How will I benefit?
If you're looking for a boost in short-to-medium duration high-intensity muscle performance, few supplements to date have fit the bill as consistently as beta-alanine.
Specifically, beta-alanine seems most effective for supporting exercise lasting longer than 60 seconds. It has not been shown to be significantly or consistently effective in shorter duration bouts of exercise, where the ATP-phosphocreatine energy system is in highest demand – Creatine is better for this, but makes creatine and beta alanine a fantastic combination.
In one of the earliest studies on beta-alanine and human athletic performance, subjects received either a placebo, 20 g per day of creatine monohydrate, 800 mg of beta-alanine four times per day, or the same dose of beta-alanine plus 20 g of creatine monohydrate. Maximal power output in a four-minute all-out cycling test was significantly increased in the two groups receiving beta-alanine, versus those receiving the placebo or only creatine. The most significant improvement was noted in the first and fourth minutes of cycling.
Another study showed that when football players consumed 3.2 g per day of beta-alanine for 12 weeks during a competitive season, their performance was shown to improve by 34.3 percent, compared to a -7.6 percent change in those consuming a placebo. In fact, when all subject responses were analyzed, those consuming beta-alanine improved by a range of 0 to 72.7 percent, whereas those consuming the placebo had a response range of between -37.5 and +14.7 percent.
Similarly, researchers out of the U.K. presented evidence that just four weeks of six grams per day of beta-alanine (1.5 g, four times per day) increased the punch force of amateur boxers dramatically with punch frequency increasing by four times, as compared to a placebo. However, when long rest periods (2-5 minutes) were provided between sets of a high-intensity strength training session, the effects of beta-alanine were insignificant.
Therefore, for the effects of beta-alanine to be most noticeable, we would recommend a high-intensity bodybuilding-style training program, HIIT or interval training, CrossFit, or all-out 1-5 minute bouts to exhaustion, with short rest periods of less than 2 minutes
When Should I Take It?
If you take a pre-workout supplement, you might already be taking beta alanine, but here’s the thing…. the performance benefits from beta-alanine are based upon raising muscle carnosine concentrations over time. Thus, the time of day you consume beta-alanine isn't nearly as important as consistently consuming beta-alanine each day.
Supplement companies put relatively small doses of Beta Alanine in pre workouts for the tingling effect it has, making the consumer believe that its doing something, in the short period, its not! It needs to be taken each and every day, not just pre workout!
Your muscle fiber makeup and the amount of muscle carnosine you have when you start supplementing with beta-alanine do not appear to impact how you will respond to supplementation. Likewise, the size of individual doses doesn't appear to affect the maximal concentration of muscle carnosine that you can achieve. Instead, the total dose over a period of time affects the final muscle carnosine concentration that you can achieve.
The dose response to beta-alanine increases exponentially over time because of the long clearance time of elevated muscle carnosine concentrations. Once you build up your carnosine concentration with beta-alanine, those elevated levels have been shown to drop by just two percent every two weeks after you cease supplementing
Are There Any Side Effects?
The scientific name for this "pins and needles" feeling one gets when taking beta alanine is acute paresthesia. It can also produce a burning, itching, or flushed feeling on the scalp or ears. Beta-alanine doses greater than about 800 mg have generally been reported to cause moderate to severe paresthesia lasting 60-90 minutes.
If paresthesia is a concern, then I would recommend you limit your initial consumption to no more than about 800-1200 mg of beta-alanine, every 3-4 hours, for at least four weeks. This will be sufficient to derive the supplement's performance benefits and your reaction to its use.
- BELLINGER, A.M. et al. (2008) Remodeling of ryanodine receptor complex causes "leaky" channels: A molecular mechanism for decreased exercise capacity, The Proceedings of the National Academy of Sciences, 2008
- Stellingwerff T, Decombaz J, Harris RC, Boesch C.. (2012). Optimizing human in vivo dosing and delivery of β-alanine supplements for muscle carnosine synthesis. Available: https://www.ncbi.nlm.nih.gov/pubmed/22358258?report=docsum.
- Stellingwerff T, Anwander H, Egger A, Buehler T, Kreis R, Decombaz J, Boesch C.. (2012). Effect of two β-alanine dosing protocols on muscle carnosine synthesis and washout. Available: https://www.ncbi.nlm.nih.gov/pubmed/21847611?report=docsum.