It also depends on how intensely you’re working out and for how long, explains Anthony Hackney, Ph.D., D.Sc., a professor of exercise physiology and nutrition at the University of North Carolina, who’s studied exercise and testosterone for decades.

Testosterone, the main male sex hormone that’s produced by the testicles, is anabolic and does help you build muscle, Hackney says. (That’s one of its functions, anyway; it has many others.) But other hormones also contribute to muscle building and endurance.

‘While testosterone is important, it’s not the only way the body decides to create an anabolic response,’ Hackney adds.

Exercise affects testosterone in other ways, too, Dr. McNeil adds. When you work out, you’ll improve your overall health and reduce your body fat, which he says can improve testosterone. Obesity is linked to low testosterone and other health problems.

‘All of these things put you in the best shape possible,’ he says. Here’s a closer look at how exercise affects your T levels.

Exercise does impact testosterone levels, but research suggests that the actual effect depends on several factors.

‘Certain types of exercise done at certain volumes and intensity can lead to an elevation in testosterone, but you can also have certain types of exercise, certain volumes of intensity that can reduce testosterone,’ Hackney says. ‘So, there isn’t a universal, ‘Oh, I’m exercising, and I’m always going to see this testosterone response.”

Many studies looking at different types of exercises—including cardio, cycling, running, swimming, and weightlifting—and their effects on T levels have found different outcomes, explains Ahmed El-Zawahry, M.D., a urologist at the University of Toledo Medical Center.

‘If we are going to summarise the results of these studies in one easy statement, exercises do not significantly change testosterone level,’ he says.

Still, some exercises, especially weightlifting, can temporarily boost testosterone. But, Dr. El-Zawahry says the surge doesn’t last long.

Body composition and fitness level factor into how exercise affects your testosterone, too. A small 2016 study found that obese and overweight men saw a boost in their T levels when they increased their physical activity, more so than when they solely restricted calories.

A 2018 study suggested that some male elite athletes had low testosterone concentrations, but the low T may be linked to higher cortisol levels in the blood from working out. The athletes studied are typically in good physical condition, with a lean body and no symptoms of low testosterone (which doctors say is often more important than your actual levels).

People with higher percentages of body fat and higher body weights are more likely to have low testosterone and experience symptoms, Dr. El-Zawahry adds.

‘You should exercise to keep your endurance, lean muscle, and low body fat, which will, in turn, keep you healthy,’ Dr. El-Zawahry says. This will reduce the risks of metabolic syndrome and reduce health issues associated with it—and those things keep testosterone at a healthy level, he adds.

Research suggests that strength exercises and high-intensity interval training (HIIT) can increase testosterone levels. Endurance-based exercises, like cardio, can potentially reduce testosterone.

Even within resistance training, the ‘greater intensity and greater volume of work’ are more likely to elevate testosterone, Hackney says. For instance, if you’re lifting heavy weights with lots of sets over a 45-minute time period, you’ll see a bigger impact.

‘If they’re a casual resistance trainer, they’re probably not going to see any substantial mark in testosterone changes,’ he adds.

A 2016 study showed that starting resistance training with large muscle groups, like your chest and glutes, and progressing to small muscle groups, such as triceps and shoulders, produced the largest testosterone response. But no exercise is going to drive your T levels through the roof, and it won’t be a prolonged increase.

Testosterone levels usually increase transiently after weights and intense physical activity about 15 minutes to an hour after the workout, Dr. Cherullo said.

Mixing endurance and resistance training likely leads to a “zero-sum game,” when it comes to its effect on testosterone, Hackney says.

Don’t worry so much about just focusing on resistance training because you think it raises your T. Dr. El-Zawahry says any exercise benefits your general health and helps you maintain a healthy body weight and T level.

While there’s research on the subject, Dr. McNeil says yoga and pilates, which incorporate aspects of strength training, likely have a positive impact on testosterone.

The elevated testosterone that you see from working out is usually temporary—maybe an hour or so, Hackney says. Then, your T levels will return to normal.

‘However, you may feel a good boost of energy with exercise because of a surge in cortisol level rather than testosterone,’ Dr. El-Zawahry says.

Remember, too, that your testosterone levels naturally fluctuate during the day. By exercising, you’ll likely maintain a healthy weight and improve your cardiovascular functioning, which has positive effects on your testosterone.

However, working out alone won’t cause a long-term increase in testosterone levels, Dr. El-Zawahry says.

Your testosterone levels tend to be the highest in the morning and then gradually drop throughout the day, Dr. Cherullo said. That’s why doctors typically test your T in the morning.

If you typically run in the morning or take 5 a.m. HIIT classes, it likely won’t affect your test results, Dr. McNeil says. So don’t skip your workout—it’s good for your T levels and your overall health.

Erica Sweeney is a writer who mostly covers health, wellness and careers. She has written for The New York Times, HuffPost, Teen Vogue, Parade, Money, Business Insider and many more.