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Lactic acid is commonly associated with fatigue and the, “BURN”, we feel when we train.

This is commonly experienced during highly intense interval training or resistance training – most people believe that lactic acid is a negative bi-product of exercise that we should aim to reduce or eliminate…

In fact, new research is now demonstrating that although lactic acid increases in line with acidosis (the ‘burn’), it is NOT the actual cause of acidosis or fatigue!!

In short, for those that like to geek out on the science, during energy metabolism and ATP hydrolysis, hydrogen ions (or protons) are created; it’s this increase in these hydrogen ions that negatively affect the PH value of the muscle, dropping it below 7.0, and creating acidosis.

Robergs et al. (2004) highlighted how the hydrolysis (breakdown) of ATP and accumulation of hydrogen ions is the real cause of acidosis, and not Lactic acid.

So How Does the Burn / Acidosis Occur in a Muscle?

The accumulation of hydrogen ions are an important part of energy metabolism (e.g. they are beneficial and provide energy).

For the bodybuilder performing interval training or resistance training, the high intense anaerobic exercise causes a high accumulation of hydrogen ions in a short period of time.  This is due to a relatively large energy demand, a greater use of phosphagens (energy storage compounds), and an increased demand of the glycolytic (carbohydrate) energy system for muscular contractions.

Accompanying this, fiber-type recruitment has an effect on the level of acidosis.  As you may be aware, during highly intense exercise we recruit more fast-twitch fibers compared to slow twitch fibres (primarily used during low intense exercise).  These fast-twitch fibers have less mitochondria (powerhouse of the cell) where cell respiration and the uptake of hydrogen ions occur.  As less hydrogen ions are being up taken or removed, the greater accumulation causes acidosis (the burn).

Finally, it’s important to note that acidosis is not categorically a devil, although it may feel like it during those NOS sets!

For example, it can help protect against potassium (K+) induced force paralysis.  However, looking at it in terms of how many reps can be completed, it does not appear to aid performance in any way and, as you will well know, it can certainly be a limiting factor.

So is Lactic Acid Useful?  

We’ve established that lactic acid isn’t a negative byproduct of exercise, but does it actual provide any additional benefits?  The answer is yes – it actually provides many positive and important benefits, playing a part in the training adaptions that allow us to grow!

One benefit may be the increased cell swelling effect of lactate.  Research has highlighted lactate accumulation as the primary cause of changes in the muscle cells osmolarity (cell size).  Lang et al. (1998) demonstrated that an increase in cell swelling stimulated muscle protein synthesis (which is key for stimulating growth), and also decreased proteolysis (breakdown / catabolism of protein).  To further support this, Gunderman et al. (2012) also found increased lactate levels caused significant elevations in muscle protein synthesis.

Also. Takarada at al. (2000) found that growth hormone (GH) increases in an acidic environment and, as we discussed earlier, lactate tends to increase in line with hydrogen ions and acidosis.  While there is still debate regarding the acute role of hormonal elevations from exercise, growth hormone plays an important role in fat loss, energy metabolism, and bone health etc.

So How do we Increase Lactate and Reap the Rewards?

1. Perform Bodybuilding-style Workouts

Research has shown that multiple sets of bodybuilding style resistance training (5+ sets of ~ 10 reps) shows a significant increase in blood lactate, intramuscular lactate and glucose.  Kraemer et al. (2005) highlighted that the buildup of these metabolites have a significant and important role in the anabolic muscle-building process.  If you’re following the MI40 principles then you can sit back and relax because, as you well know, the workouts cause plenty of lactic acid!

2. Increase Time Under Tension (TUT)

Kraemer et al. (1994) highlighted that the combination of short rest periods and longer time under tension / total duration of the lift (e.g. 5 reps vs 10 reps) resulted in significantly greater blood lactate levels.  As we would expect, if you perform more reps, lactate increases.

3. Add in some Blood Flow Restriction Training (BFR)

BFR has been shown to cause a very large increase in lactate levels which helps explain the large BURN and PUMP you feel when performing this type of training (Wilson et al., 2012).  This is one of the explanations for the anabolic benefits of BFR, that the occlusion causes increased hypoxia (lack of oxygen) and therefore even more lactic acid than normal is produced.

4. Shorten your Rest Periods – up the BURN!

Shorter, more metabolic-type workouts with less than 60 seconds rest will cause a greater increase in lactic acid as you perform more sets.  Don’t forget, there are other mechanisms behind muscle growth and short rest pump work shouldn’t be the only type of training you do!

5. Dropsets, Supersets & Giant Sets?

Although we lack research on these advanced training variables, based on the fact that typical 10 rep resistance training exercise causes an increase in lactate, it’s highly likely that super sets, drop sets and giant sets cause an even greater increase.

6. Add in some Intervals!

As mentioned above, HIIT is another great tool / training method to rapidly increase lactate levels.

Research by Trapp et al. (2008) found rapid elevation in very short bouts of HIIT (less than 30 seconds).  For best results, HIIT should result in large amounts of burn and pump, but multi-joint cardio machines (such as an elliptical or X-Trainer) may not isolate one area – instead, focus on the bike, battle rope, prowler, or hill sprints.

So, Do Normal PH Levels & Avoiding Acidosis = More Reps & Greater Growth?

“PH buffers” have become popular in the sports and fitness industries of late because, much like lactate, they appear to help maintain a stable PH / slow or reduce acidosis.  Luckily, it comes in probably one of the cheapest supplements available, sodium bicarbonate, which can be purchased even from Walmart.

A reasonable amount of research has now demonstrated that sodium bicarbonate supplementation has performance benefits during exercise lasting between 1 – 10 minutes  (Nielsen et al., 2002; Kowalchuk et al., 1984).

Interestingly, these buffers appear in the plasma, outside of the muscle – this could be important.  It’s hypothesized that these buffers almost, “extract”, or, “remove”, some of the hydrogen ions from the muscle, which helps to maintain or neutralize the intramuscular PH.

It’s also hypothesized that a large increase in extracellular (outside of the muscle) acidosis may cause Central Nervous System (CNS) fatigue, so the effects of supplementary sodium bicarbonate may also help in this regard by improving your time to exhaustion, while possibly increasing your motivation / drive towards the end of a workout as well.  This is supported by studies showing lower levels of perceived exertion (intensity) when using sodium bicarbonate.

When supplementing with Sodium Bicarbonate, build-up slowly; it’s famous for causing regular restroom visits!  For performance increases, you can either supplement as a once-off for a special event, or even over the long-term.

It’s important to consume around 300-500mls of water along with it and to start by testing with lower doses.

We recommend consuming 0.3g per kg / 0.66g per lb of bodyweight (typically around 25-30g) about 60 to 90 minutes pre-workout, or, that same amount 3 times per week as a chronic dose instead.

It’s worth noting that these buffering benefits do not appear to be exclusive only to sodium bicarbonate either – other PH buffering aids such as citrate may also provide benefits as shown by Van Moonfoort et al. (2004).

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Key Points / Summary 

• Lactic acid was discovered nearly 300 years ago and has been extensively researched over the last 100 years.

• Lactic acid and lactate are not the exact same.  Lactic acid is an acid, which means it can donate a hydrogen ion and then becomes lactate.  For the purpose of this article, and for simplicity, we use them interchangeably.

• It’s now well established that lactic acid is not detrimental to performance, and is actually plays an important role in maintaining muscle PH.

• The increase in burn and fatigue when exercising is actually caused by an increase in hydrogen ions and acidosis (which is defined as the body’s PH dropping below 7).  During intense exercise, the PH value can drop to around 6.4.

• During low intense exercise, the increase in hydrogen ions causes less of an issue and plays a part in aerobic metabolism and energy production.

• In the case of high intense exercise however, the lack of oxygen and hypoxic conditions cause a large accumulation of hydrogen ions, and an increase in acidosis with a drop in the muscle PH, leading to the burn and fatigue.

• Fast-twitch fibers involved in high intense exercise such as sprints and weight training have less mitochondria compared to slow-twitch fibers and work predominately in anaerobic conditions (without oxygen).

• Benefits of lactic acid include an increase in cell size and cell swelling, which appears to be an important mechanism of hypertrophy, while also stimulating muscle protein synthesis.

• Increased lactic acid levels may also help to reduce muscle protein breakdown.

• Lactic acid may promote certain anabolic signaling pathways and cause short term increases hormones such as growth hormone.

• There are several methods for inducing a large amount of lactic acid during training, these include (but are not limited to):

1. Typical higher rep, short rest, high volume based resistance work.

2. Blood flow restriction (BFR) training.

3. Advanced techniques such as super sets, drop sets, increased time under tension work, giant sets.

4. High Intensity Interval Training (HIIT), preferably engaging in activities such as hill sprints, prowler, wingates, and battle ropes.

• PH buffering supplements may help to improve performance in short duration events (less than 10 minutes), increase time to exhaustion, reduce CNS fatigue, and improve your rate of perceived exertion.

• The two supplements with the most research in this regard include sodium bicarbonate (dosed at 0.3g/kg or 0.66g/lb of bodyweight) and beta alanine (3-5g per day, which can be split into 2 – 3 smaller doses throughout to avoid side-effects).

• Sodium bicarbonate supplementation can be used acutely for an event, or over the long term for performance.  It’s important to consume 300-500ml of water with it and to test lower doses due to the potential for gastro-intestinal issues.  0.3g/kg or 0.66g/lb of bodyweight 60-90 minutes pre-workout, or that same amount 3 times per week as a chronic dose instead.