“Don’t lift weights for more than 45 minutes,” warn the exercise police.
“If you do, testosterone levels will plummet, cortisol levels will rise and you’ll be sucked into a catabolic black hole from which you’ll never escape.”
The idea that you should stop training after 45 minutes because you reach some kind of hormonal “tipping point” is one of the most ridiculous things I’ve ever heard.
It’s a claim that fails on a couple of levels, most notably the fact that it’s not true.
In fact, some workouts lasting more than 90 minutes have been shown to raise testosterone above resting levels for at least two hours after the workout has finished .
The Hormone Hypothesis
The idea that the short-term hormonal response to training has a big impact on muscle growth is something that’s been called into question in recent years .
In one study on the subject, researchers analyzed data collected from 56 men who took part in a 12-week resistance training program .
If the post-exercise change in testosterone levels was important as far as building muscle is concerned, you’d expect to see two things.
Guys with the largest testosterone response after training build the most muscle. And those with the smallest response would build the least muscle.
But when they looked at the data, the researchers could find no significant link between the exercise-induced rise in testosterone levels and gains in muscular size or strength.
What about cortisol?
Cortisol is generally considered a “catabolic” hormone that you should take all possible steps to avoid. If the post-exercise rise in cortisol was putting the brakes on muscle growth, you’d expect to see men with the largest rise in post-exercise cortisol gaining the least amount of muscle.
Instead, the opposite was true.
There was a weak but significant link between the rise in cortisol and gains in lean body mass, as well as the growth of the type II muscle fibers.
In other words, subjects with the biggest rise in cortisol levels were also the ones who gained the most muscle.
Drilling further down into the results, subjects in the study were also divided into responders (men who built the most muscle) and non-responders (those who built the least muscle).
And the hormonal responses of those who made the fastest gains in size and strength were not significantly different to those who made the slowest gains.
Or to put it another way, the hormonal response of subjects in the top 16% in terms of muscular gains were no different from those in the bottom 16%.
So why are people saying that 45-60 minutes is as long as your workout should last?
Enter The Bulgarians
The idea seems to have originated with Bulgarian Olympic lifting coach Ivan Abadjiev. Over a 20-year period, Abadjiev turned a weightlifting team that struggled to win anything into one that won numerous European, World and Olympic titles.
Rather than train once a day for several hours at a time, the Bulgarians would train numerous times both in the morning and in the afternoon, with each training session lasting from 30 to 45 minutes.
The protocol was based on Abadjiev’s claim that elevated blood testosterone levels could only be maintained for between 30 and 60 minutes, with the average being 45 minutes.
Whether or not he actually believed this himself is hard to say. Nicknamed “the Butcher” for the extreme level of dedication and commitment he demanded from his athletes, rumor has it that Abadjiev’s need for control was vast.
He once had a rebellious pupil sent to the military to work from dawn to dusk in a stone quarry.
Keeping them in the gym all day may have had a lot less to do with testosterone than it did with imposing discipline and control on his athletes.
Big Beyond Belief
Many of the principles employed by the Bulgarians were popularized in a book published in the early 1990’s called The Bulgarian Power Burst System. Later editions had different titles, such as Big Beyond Belief.
The book sold thousands of copies via its famous “I’ve got to get this off my chest before I explode” advertisement, and became one of the most successful self-published bodybuilding guides of all time.
It went on to influence a number of writers, many of whom simply regurgitated the fictitious “testosterone levels drop after 45 minutes of lifting weights” advice before checking whether or not it was actually true.
That’s not to say you should be training for hours on end. Plenty of people are wasting much of their remaining time on this planet doing endless sets of pointless exercises.
But cutting your workout short simply because you’ve been in the gym for 60 minutes makes absolutely no sense at all.
To sum up, how long should a workout last if you want to build muscle as fast as humanly possible?
On average, it’s going to take somewhere between 60 and 90 minutes. With some programs, an effective workout might last around 45 minutes. With others, it might take you a couple of hours, especially if you’re taking a long rest between each set.
Both approaches can work, just as long as your training program is set up properly.
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ABOUT THE AUTHORChristian Finn is the nation’s leading authority on science-based, joint-friendly ways to build muscle. A former "trainer to the trainers," he holds a masters degree in exercise science, and has been featured in or contributed to major media on two continents, including the BBC and Sunday Times in the U.K. and Men’s Health and Men’s Fitness in the U.S.