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8 Popular Non-Prescription Substances and How They Affect Your Clients’ Performance

In a recent post, we talked about how your clients’ prescription medications can affect their performance and outcomes. From reduced strength and endurance to blocking weight loss, your clients’ meds may be a pivotal factor that keeps them from reaching their goals.

Fortunately, most health history questionnaires provide a place to list prescription drugs, and some basic research can help alert you to the side effects of many medications, and give you more insight into your client’s overall health profile.


But have you ever thought about the non-prescription substances your clients may be using, and the risks and obstacles they pose?

10 Common Non-Prescription Substances and How They Affect Performance

There are a number of products and substances that are commonly consumed by a vast variety of people, and your clients may be among the users. These substances are not listed on your client’s health history questionnaire, and often fly under the radar. Here is a partial list of substances you should look out for:

  1. NSAIDs: Perhaps the most abused and overused substance among the fitness community, ongoing use of non-steroidal anti-inflammatory drugs like naproxen and ibuprofen can have harmful side effects. Even short term use of NSAIDs can increase your risk of heart attack and stroke, can cause bleeding in your GI tract, and can wreak havoc on your liver. During training, NSAIDs can mask pain that indicates overuse. NSAIDs should not be taken more that three days in a row.
  1. Energy Drinks: With their high caffeine content (up to 100 mg per oz), energy drinks can rev up your metabolism and keep you awake and alert. But the tradeoff is serious health risks, including elevated blood pressure, heart disease, kidney disease, anxiety and obesity.
  1. Ergogenic Aids: This substance category covers a broad range of pills and powders taken to enhance performance and promote post-exercise recovery. Most are not regulated by the FDA, and many have questionable effects on performance and recovery. Taking a lot of EAs over time can cause liver and kidney damage.
  1. Anabolic Steroids: Despite their bad rap for decades, ‘roids remain popular among bodybuilders because they promote rapid and massive muscle hypertrophy. However, users pay a high price in side effects, including male pattern baldness, liver damage, sexual dysfunction, shrinking testicles, lysing of muscle cells, and premature death. And let’s not forget Roid Rage, the aggression that can lead to criminal behavior.
  1. Testosterone Boosters: Testosterone is often prescribed to treat sexual dysfunction in men (they may be embarrassed to list it with their other meds), but it is also abused as a performance enhancing substance to boost strength and muscle mass. Side effects include increased risk of heart disease, enlarged prostate and male breast swelling and tenderness.
  1. Diet Pills: There is a wide range of weight loss supplements on the market, with an equally wide range of ingredients. Many have large amounts of caffeine, which increases risk of heart disease and stroke. Fat blockers and carb blockers can interfere with nutrient absorption, leaving your client deficient in essential micronutrients.
  1. Opioids: Opioid abuse has reached epidemic proportions in the United States, causing serious life-threatening addiction. Users often get hooked from prescription pain meds after an injury or surgery. However, once addicted, they will go to great lengths to get the drugs in any way they can. Opioids can slow heart rate, increase the risk of falls, desensitize your client to pain, reduce endurance and interfere with breathing.
  1. Alcohol: You may not expect your client to show up roaring drunk, but even a couple of beers or glasses of wine consumed at lunch or happy hour can seriously impair your client’s performance and increase their risk of injury.

Your Responsibility as a Trainer

If you are aware or suspect that your client is abusing substances that may harm their health, there are a few steps you can take:

  • Educate your client about the harmful effects of the substance and how it affects their performance.
  • If you work in a studio or gym and you are not the owner, notify a supervisor or manager about the abuse.
  • If your client shows up for a session impaired by a substance, refuse to train them to avoid injury and protect yourself from liability.
  • If the abuse appears to be an addiction, refer them to a licensed professional who can help them.


To build a successful fitness career, increasing your knowledge about health issues is a must. You cannot help your clients if you do not understand their medical conditions, and how drugs affect their performance. As always, W.I.T.S. has valuable resources to help you grow. Consider a certification in Older Adult Fitness, or get continuing education credits with Essentials of Diabetes and Prediabetes, Introduction to Cardiovascular Disease and Exercise, or any of our other MFEF courses.

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