What Happens to Your Body When You Take Pre-Workout

Pre-workout supplements have become a popular product for increasing energy, supporting muscle growth, and improving endurance during exercise. Common pre-workout ingredients have some evidence-based benefits for your gym sessions, but they also come with some risks.

Pre-workout supplements often contain caffeine as a main ingredient to make you feel more alert and energetic at the gym, said Alexander LeRitz, MSc, RDN, CDN, CNSC, CPT, registered dietitian and sports nutritionist at JM Nutrition. Health.

Caffeine has a chemical structure similar to the compound adenosine, also known as the “fatigue” molecule. Adenosine builds up in your brain throughout the day, making you tired.

When you consume caffeine, it blocks adenosine receptors in your brain, making you feel more alert and attentive, LeRitz explained.

This process also triggers the release of excitatory hormones, such as epinephrine (adrenaline), which increase your heart rate and increase your energy.

Caffeine can also help your muscles work harder and longer, said Brian Cole, MD, MBA, a sports medicine surgeon, head team physician for the Chicago Bulls and team physician for the Chicago White Sox.

When caffeine blocks your adenosine receptors, you can exercise your muscles more without normal “fatigue signals” reaching your brain, Cole explained.. Essentially, caffeine “helps your muscles contract longer without reaching failure,” he said. Health.

Your pre-workout supplement may also contain beta-alanine, an amino acid that increases your muscle carnosine levels. Carnosine helps fight acids that build up during strenuous exercise, delaying muscle fatigue and the “proverbial ‘burning’ feeling,” LeRitz said. This can ultimately lead to improved physical performance.

If you’re doing cardio, pre-workout caffeine can also help improve your endurance, LeRitz said. Caffeine can boost your respiratory function and aerobic capacity, he explained, meaning you may be able to run, bike, or swim more before fatigue sets in.

Another common pre-workout ingredient is citrulline malate, a compound that can improve blood flow to your working muscles. This helps provide your muscles with fresh oxygen while effectively flushing out muscle waste, LeRitz said, which can help improve endurance.

Some people may be more sensitive to the effects of pre-workout depending on their caffeine tolerance and metabolism. In a 2019 survey of 1,045 people taking a pre-workout, more than half (54%) reported side effects.

Common pre-workout side effects include:

• Skin reactions including redness, rash, irritation and itching
• Nausea
• Heart abnormalities, such as rapid heart rate, high blood pressure, and heart palpitations
• Dizziness or vertigo
• Feelings of nervousness and anxiety
• Inability to sleep or insomnia

It’s generally recommended to keep caffeine intake below 400 milligrams per day, “which can easily be exceeded with the use of pre-workout supplements, as they can often contain more than 200 to 300 milligrams of caffeine per serving,” LeRitz said.

“When taking supplements pre-workout, it’s a good idea to monitor your stimulant intake throughout the day, which may look like skipping morning coffees to keep your overall caffeine intake below the recommended daily threshold,” LeRitz added.

Beta-alanine is also known to cause a side effect called paresthesia, a tingling sensation or “pins and needles” sensation, often in the face, hands, and neck. It’s usually temporary and harmless, but “can be slightly uncomfortable for some people and cause anxiety if someone isn’t expecting it,” LeRitz said.

According to Cole, pre-workout is not recommended for anyone under 18 or during pregnancy. It is also not recommended for people with pre-existing conditions, such as heart disease, arrhythmia, hypertension, anxiety, liver disease or kidney disease, because the ingredients in the pre-workout may make base symptoms worse, Cole said.

If you’re trying a pre-workout supplement, LeRitz suggested starting with one that’s low in caffeine and free of proprietary blends, which don’t disclose the exact amount of each ingredient.

LeRitz also recommended starting with a quarter or half dose to gauge your reaction to the pre-workout before taking the full dose. “Dipping your toes in the water” can help protect your sleep and recovery, and lessen side effects, he said.