Are Pre-Workout Powders Overloading the Heart?

Medscape

18-06-2025

Pre-workout supplements are gaining popularity in Brazil because of their promising effects, including increased focus, energy, endurance, enhanced performance, and reduced muscle fatigue. A growing number of brands are now available in specialty stores, pharmacies, and supermarkets.
However, with so many options in the market, are consumers aware of the risks and product components, and do these products benefit physical performance?
Typically sold in powdered soluble form, but also available as capsules, gummies, gels, or ready-to-drink liquids, pre-workout supplements combine various substances, such as caffeine, beta-alanine, arginine, taurine, and creatine, with formulas that vary by brand.
'Pre-workout [supplements] usually have a combination of multiple elements, such as vitamins, proteins and amino acids, but only a very small portion actually have any effect with proven scientific evidence on sports performance,' said Cristiano Barcellos, PhD, director of the Department of Sports and Exercise Endocrinology at the Brazilian Society of Endocrinology and Metabolism.
Metabolic effects vary depending on the dosage of each component. Barcellos identified four substances with 'robust evidence' supporting their benefits in physical activity:
Caffeine: increases alertness; the suggested daily dose (including coffee consumption) is 3-6 mg/kg of body weight
Beta-alanine: increases cellular carnosine, blocking hyperacidity in muscles that compromises performance; ideal for intense exercises lasting 1-4 minutes
Creatine: boosts strength and muscular endurance, particularly in short, high-intensity, intensive efforts
Nitrate: improves circulation, supports long-duration aerobic activity
Safety Concerns
In addition to the aforementioned substances, a wide variety of others are also present in pre-workout supplements. These include citrulline, malate, arginine, taurine, tyrosine, branched-chain amino acids, and other adaptogens. Although they may produce the desired effects, current evidence supporting their impact on performance remains weak to moderate. Further studies are required to understand their mechanisms and effectiveness.
Without understanding these components, individuals may take pre-workout supplements designed for short, high-intensity workouts but engage in prolonged aerobic activities, such as long-distance running or soccer. In such cases, in addition to a possible worsening of performance, there is a risk for unexpected adverse effects.
'There are reports of cases that require hospitalization and, occasionally, even result in death. The person ends up being exposed only to the side effects of these substances, so I personally do not recommend the use of these ready-made combinations,' said Barcellos. 'Qualified professionals, such as nutritionists or sports physicians, should advise using only the necessary components individually,' he concluded.
Caffeine Risks
Caffeine, one of the most common components in pre-workout supplements and proven to be effective as a stimulant and improve focus, is also among the most concerning. Some ready-made products exceed the recommended limit of 200 mg and contain up to 1 g of caffeine, posing a major health risk to consumers.
Given the wide variability in dosages, inconsistent formulations, and often a lack of transparency in product labels, Luiz Eduardo Ritt, MD, PhD, president of the Department of Ergometry, Exercise, Nuclear Cardiology, and Cardiovascular Rehabilitation at the Brazilian Society of Cardiology, also advises against the use of ready-made blends.
'There is a large variation in the individual response to each pre-workout [supplement], with reports of patients who developed arrhythmias when making a more strenuous effort, both atrial and ventricular, the latter being more severe and with the potential to progress to cardiac arrest,' he said.
Ritt emphasized a particular concern when caffeine is used in combination with hormones or antidepressants, which can increase the risk for arrhythmias.
'The mechanism involved is often related not only to increased adrenergic tone, which makes the heart more susceptible to arrhythmias, but also to the widening of the QT interval, a factor directly related to the occurrence of malignant arrhythmias, such as ventricular arrhythmias,' he explained.
Beta-Alanine
Beta-alanine, another common component of pre-workout supplements, raises concerns due to paresthesia, a side effect that causes tingling sensations in the extremities. Although this effect is common, it is not typically harmful.
'This effect is still being studied. We do not know exactly why this occurs, but we know that beta-alanine can bind to a neurologic receptor in the skin that is associated with the transmission of painful impulses to the brain, causing tingling. This is a temporary and self-limiting effect, with no apparent severity,' Barcellos explained.
The National Health Surveillance Agency in Brazil (ANVISA) delayed the approval of beta-alanine due to several factors and only authorized its use in November 2020 after pressure from the sports sector.
Until then, access was limited to imported products or compounded formulations, although this substance has been used internationally.
A detailed review by the International Society of Sports Nutrition confirmed the ergogenic effects of beta-alanine, particularly in short, high-intensity workouts, and established a recommended dosage and favorable safety profile.
Clinical Guidance
Pre-workout supplement use should be personalized. 'It is necessary to analyze which product is being used, in what dose, individual sensitivity, and whether there is concomitant use with any other substance. The risks accumulate with each of these variables,' Ritt stated.
A basic electrocardiogram can help detect cardiac rhythm abnormalities and elevated cardiovascular risk. 'We assess for signs of hypertrophy, ventricular dysfunction, impaired contractility, valvular abnormalities, or insufficiencies. Combined with a thorough medical history and physical examination, these findings help identify higher-risk individuals,' he said.
All supplements and physical activities should be accompanied by a balanced diet. Natural foods have beneficial metabolic effects on humans.
'Nitrate is one of the most natural and effective compounds found in many vegetables, such as beetroot. It favors long-lasting activity by stimulating nitric oxide production in the arteries. There is no need to rely on powdered supplements if beetroot juice can provide the same effect,' said Barcellos, noting that nitrate is the only natural product with a proven effect on individual performance.
Other natural products may have ergogenic properties without the need for commercial pre-workout supplements. These include coffee and guarana powder, which act as stimulants, and cinnamon and ginger, which are potentially beneficial for improving physical performance.
'Some vitamins and teas commonly used in nutrition also combine compounds with ergogenic potential. However, the effect varies from person to person, and excessive use can be risky, particularly because of possible liver toxicity,' Ritt noted. 'Natural does not mean harmless. Each factor must be carefully considered.'
He also emphasized the importance of hydration in this regard. 'If physical exercise is intense, in conditions of high heat and humidity, and there is no adequate hydration, disorders may arise that lead to changes in sodium levels and hypernatremia. An excessive increase in body temperature can also lead to sudden illness, resulting from the combination of all these factors.'