Stephen Graham makes a formidable entrance in A Thousand Blows, the new TV series set in the bare-knuckle boxing world of Victorian London. Tracking him from behind as he slowly prowls towards the ring, the camera lingers over the brawny width of his V-shaped back, his meaty deltoids and thick, powerful arms. Unrecognisable from his previous roles, the 51-year-old looks like a wrecking ball made of flesh.

As a middle-aged man, Graham worked hard for his transformation. For six months he committed to five sessions a week to create the hulking physique suitable to play the muscle-bound brawler Henry “Sugar” Goodson. Yet the results of Graham’s efforts transcend Hollywood aesthetics. A growing body of research shows that building muscle isn’t just handy for unscrewing stubborn jars of pickles. As Dr Adam Brown puts it: “Muscle should be seen as your organ of longevity.”