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The Ultimate Supplement

N-Acetyl Cysteine affect on strength and endurance

What is N-Acetyl Cysteine?

N-Acetyl Cysteine (NAC) is an acetylated variant of the amino acid L-cysteine. Glutathione is comprised of three amino acids - cysteine, glycine, and glutamate. L-cysteine represents the rate-limiting factor in cellular glutathione production. Glutathione is one of the most important and prevalent antioxidants in the body, which is why NAC is able to have such a positive impact on numerous ailments. By increasing glutathione, oxidative stress and free radicals are directly and significantly reduced helping to achieve redox balance in cells.

What is NAC Used For?

After doing extensive research, NAC is quite possibly the most impressive supplement I’ve come across. NAC is used on a wide variety of conditions from traumatic brain injuries to acne. In this article, I’ll be focusing on NAC’s effects on strength and endurance, but below I have included a list of conditions and diseases that NAC has been shown to positively impact. If you are interested in further researching anything mentioned below I have included links to research studies, so you can simply click any of them to learn more.

  Bipolar disorder
  Prostate cancer
  Lung cancer
  Breast cancer
  Brain injuries
  Chronic obstructive pulmonary disease (COPD)

    Strength & Endurance

    Study 1

    In this double-blind, crossover study, 8 male endurance athletes intravenously received either NAC or a saline placebo. After 45 minutes of cycling at 71% peak oxygen consumption (VO2 peak) followed by cycling to fatigue at 92% VO2 peak they saw a 26.3% increase in time to fatigue. This exemplified NAC’s ability to improve endurance by reducing oxidative stress caused by intense exercise.

    Study 2

    NAC does not increase strength in non-fatigued muscles but it does play a causal role in reducing muscular fatigue caused oxidative stress. This effect was shown in a study published in the Journal of Clinical Investigation. Participants were intravenously given either 150 mg/kg of NAC or 5% dextrose (placebo) in water by intravenous infusion. Then they were seated in a wheelchair to have their calf muscles electrically stimulated while force output by the muscles was recorded. Impressively, the group given NAC saw a 15% increase in strength over the placebo group. This change became evident after 3 minutes of continuous stimulation and maintained throughout the duration of the 30-minute protocol. 

    Study 3

    It was theorized that free radicals produced during strenuous muscle contractions contribute to respiratory muscle fatigue. Because NAC is known to be a very effective free radical scavenger it was used to test this theory. In this study, they exposed the animals to an increased inspiratory load which was set up to induce fatigue of the respiratory muscle and ultimately end with respiratory arrest. The animals that received NAC had higher levels of glutathione and lasted significantly longer before respiratory failure. This displayed NAC’s powerful ability to deter respiratory failure and promote cardiovascular endurance.


    N-Acetyl Cysteine dramatically improves endurance both in strength and cardiovascular endurance. It will not directly improve max strength on any exercises, but it may indirectly improve max strength in the long-run by improving workout volume capacity. What I mean by this is if endurance is improved you can do more reps per set with a given weight. This will allow you to increase weight in relatively high rep sets which may lead to faster strength gains. Athletes that will benefit most from NAC are those that require a notable amount endurance. For example, football players, soccer players, and track and field athletes will likely see substantial improvements in performance when taking NAC. Because NAC substantially increases the antioxidant glutathione I believe everyone can greatly benefit from taking it. For some, the benefits will be completely life-changing, and for others, there may not be any noticeable changes. Just keep in mind, you don’t have to feel a difference for it to be working. Similarly to if you eat healthy for a week, you may not feel any different even though you will certainly be improving your health.