Gym-goers who want to pump the heaviest weights might figure that bulging thighs and bulky buttocks are the path to greater power. But a study involving one of the world’s strongest men found that a set of slender, rope-like muscles that typically get far less attention could be more important than previously thought.

Scientists at Loughborough University’s school of sport, exercise and health sciences examined the rippling sinews of Eddie Hall, a Staffordshire truck mechanic nicknamed “the Beast” who became the world’s strongest man in 2017.

They discovered that after his 15 years of continuous training, a set of long, thin muscles in his legs were up to three times the size of those in men who do no strength training.

To their surprise, they found that these muscles in Hall – linking from below the knee up to the pelvis – showed the greatest development compared with mere mortals who do not spend any time developing extreme strength.

They are known as “guy rope” muscles and they stabilise the pelvis and thigh bone. The scientific name of these less understood powerhouses are the sartorius, gracilis and semitendinosus, and they helped Hall achieve a world record 500kg deadlift in 2020 – equivalent to hoisting a camel over his head.

Relative to untrained men, these muscles demonstrated the largest differences in mass of any that were examined in laboratory conditions. Some of his other muscles and tendons – for example, the patella tendon in the knee and the hip flexors – were far less out of the ordinary.

“These muscles have had very little attention scientifically, so we don’t really know how important they are in different tasks,” said Jonathan Folland, a professor of neuromuscular performance. “But to find that they were really very well developed in someone who has spent decades lifting and carrying heavy loads – and is very good at that – was really interesting. These muscles clearly are more important for lifting and carrying very heavy loads than we previously thought.”

Dr Tom Balshaw, a lecturer in kinesiology, strength and conditioning at Loughborough, said it may be possible that targeted exercises, including hip rotations and knee flexing, could boost the “guy rope” muscles independently of squats and other, more common exercises that also appear to work.

Hall has bench-pressed 300kg and achieved a world record 216kg on the axle press, which requires a huge barbell to be lifted from the ground and held above the head. After that milestone, a pumped Hall declared: “Don’t ever, ever put a limit on what I can do, because I will prove you wrong every single time.”

Hall is available to hire for events and will appear in a 1960s British army tank painted with his “Beast” logo for £5,000 to £10,000 a time.

The study comes amid a boom in gym use among young men and women. It has sparked concerns about the effect of “gymfluencers” and fears that constant comparison with ideal bodies could can cause mental health problems. A report by PureGym said 42% of 16-24-year-olds increased their spending on exercise last year.

Just how different Hall is from the general population was made clear when the scientists at Loughborough measured his individual muscles. The quadriceps in his thighs were more than double the size of those of an untrained man and 18% larger than the next biggest the team had ever assessed, in an elite sprinter.

Hall’s hamstrings were twice the size of the untrained population’s and his biceps femoris, a large muscle in the back of the thigh, was two to three times larger.

In June, two slender TikTok influencers, Jamil and Jamel Neffati, had a closeup view of Hall’s extreme dimensions after they signed up to fight him simultaneously at a mixed martial art event in Blackburn called the “World Freak Fight League”. Since the Neffatis each weighed less than half as much as Hall, his victory was never in doubt.