August 5, 2026, 6:29 pm | Read time: 4 minutes
Summer, sun, heatwave–and yet the training plan shouldn’t falter. But anyone lifting weights or doing intense workouts in current temperatures around 86 degrees Fahrenheit and above quickly notices: The training feels significantly more strenuous than usual. Does this automatically mean that muscle building suffers in the heat? Not necessarily. Personal trainer Markus Bremen explains why high temperatures do challenge the body, but muscle building is still possible–if some important rules are followed.
The Body Sets Different Priorities in the Heat
It’s no coincidence that a workout feels significantly more strenuous at 95 degrees Fahrenheit. The body initially focuses on protecting itself from overheating. “In the heat, the body switches to priority mode: Thermoregulation takes precedence over muscle work,” explains Markus Bremen. As a result, more blood is directed to the skin to release heat. “At the same time, this means less blood volume is available for the working muscles.” The result: heart rate and perceived exertion increase even with the same load, while core body temperature rises more quickly. Additionally, heavy sweating can lead to fluid and electrolyte losses.
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The nervous system also plays an important role. “The central nervous system also reduces maximum force output as a protective mechanism,” says the fitness expert. Therefore, the body tires not only on a muscular level but overall more quickly. The result: The same training weight suddenly feels significantly heavier. Many manage fewer repetitions or need to take longer breaks. However, this does not automatically mean that muscle building becomes impossible in the heat.
Muscle Growth Despite Heat?
Outdoor temperature alone does not determine whether muscles grow or not. Heat does not necessarily impair muscle building. “Directly seen, no–muscle growth is triggered by mechanical tension, metabolic stress, and sufficient training volume, not by the ambient temperature itself,” emphasizes Markus Bremen. “The problem is indirect, as at 95 degrees Fahrenheit, performance usually decreases, so fewer repetitions, less weight, or fewer sets with proper technique are possible. The effective training volume–the main driver for hypertrophy–therefore decreases if you don’t counteract it. Additionally, the necessary recovery time between sessions usually extends,” says the personal trainer.
In other words: It’s not the heat itself that prevents muscle growth, but rather the fact that under these conditions, training often can’t be as high quality. Unless you adjust your training.
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How Training Should Be Adjusted at 95 Degrees Fahrenheit
Those who want to train effectively despite summer heat should not stubbornly stick to their usual training plan, according to Markus Bremen. “Moving training to cooler times of the day–early morning or late evening–or to an air-conditioned gym is often the simplest measure,” he recommends. It’s also important to actively manage fluid intake: “Drink before, during, and after training, and pay attention to electrolytes, especially sodium, if sweating heavily.”
Flexibility is also required in terms of intensity and training volume. “It’s better to train a bit lighter or with more breaks than to stubbornly stick to the plan and push through with poor technique–the risk of injury increases in the heat. Additionally, heart rate and core body temperature take longer to cool down between sets.”
Take Warning Signs Seriously
Despite all motivation, personal health should always take precedence. “Dizziness, headache, nausea, or feeling cold despite the heat are clear signals to stop,” emphasizes Markus Bremen. These symptoms can indicate the onset of heat exhaustion and should not be ignored.
However, those who regularly train in high temperatures benefit over time from an acclimatization effect. “The body adapts to regular heat exposure over one to two weeks–including increased plasma volume and more efficient sweating. Those who persevere can increasingly tolerate training in the heat better,” says Markus Bremen.
His conclusion is therefore nuanced: “Muscle building is fundamentally possible at 95 degrees Fahrenheit, but usually not with the same efficiency as at moderate temperatures. Those who smartly adjust training time, intensity, and fluid intake can largely offset the heat disadvantage–no ego shooting!”