The Age of Fitness by Jürgen Martschukat review – why we are obsessed | Health, mind and body books

When did “fitness” become a pastime in itself, an interest separated from any particular physical activity? When people employ a “personal trainer”, what are they training for? What is the thing for which they must sweat to attain a state of perpetual readiness? And when did “fitness” become not just a physical but a moral good, the obligatory aim of every citizen? Luckily this book enables one to approach such mysteries from the comfort of one’s armchair.

The word “fit” appeared in English (as “fyt”) in the 15th century, meaning appropriate or well suited. In Shakespeare and Fletcher’s Henry VIII, when the king sends for his new secretary, Gardiner, saying “I find him a fit fellow”, he doesn’t mean that the man has admirable cardiovascular capacity. And so something may be fit for a king, or not fit to be repeated, down the ages. Early on, too, “fitness” acquired a moral patina, as it could mean a person’s worthiness rather than simply suitability, and “the eternal fitness of things” was an 18th-century catchphrase about humans’ correct (“fitting”) relationship with a divinely ordered universe.

Only in the 19th century does “fit” acquire the modern sense of having some athletic capacity, apparently influenced by Darwin’s employment of the term “fitness” in On the Origin of Species, where it describes the likelihood of an organism’s leaving offspring in a particular environment. According to the OED, the first animals to be described as “fit” in the modern athletic sense were racehorses in the 1870s, followed a decade later by “men and camels”. The word became fashionable: by 1891 a dictionary of English idioms notes that if asked how one is one may reply “Very fit, thank you; never felt better”.

Fitness as we now understand it became fashionable then too, as Jürgen Martschukat’s fascinating history shows. By 1915 the expression “keep fit” was in widespread use, a US sports magazine reported. Especially in America, Martschukat argues (in Alex Skinner’s translation), “the activation of the body, and especially the white male body”, was the necessary response to the threat to white supremacy represented by increasing immigration to the US. This equation of physical exercise with national purity, of course, reached its apex in Nazi Germany, as the author describes. But that does not mean our modern concept of fitness is ideologically neutral, or indeed freely chosen.

Darwin did not originally write of the “survival of the fittest” under the pressures of natural selection, but he approved of the phrase after it was first used by Huxley, and social Darwinism embraced the idea fully. Our own hyper-individualist age, too, portrays the world as a merciless battle of all against all, and so “fitness” as we understand it today becomes another obligation of the precarious worker and a way to disaggregate the social spreading of risk: hence, for example, employee health programmes and insurance discounts offered to people who go regularly to a gym.

This development, too, has long roots, as Martschukat shows: already in the early 20th century, “the enfeebled body of the neurasthenic, male white-collar employee became a symbol of the threats and crises besetting modern societies”, and subsequent fitness crazes, from the invention of jogging in the 1970s to the discovery of Viagra (which the author interestingly analyses as another pharmacological invention in “fitness” writ large: a fusion of health and “performance”) were all marketed first to middle-aged men.

These days, as the author reminds us, there is almost nothing that doesn’t impinge on “fitness”. Everyone should be taking “supplements”, and even sleep has been app-ified so that the obedient worker in the age of the quantified self might maximise her productivity during the next workday. “In neoliberal times,” Martschukat writes, “preventive self-care is the task of each and every one of us.” But the combative or militarised tone of many modern fitness regimes (boxercise, boot camps, Tough Mudder) encourages their customers to think of them as actually heroic. “If the fitness aficionado strives for a higher good, as befits a true hero, then this good is their own success, raised to the status of social principle.”

One irony in all this is that the success of hypermuscular actors Sylvester Stallone and Arnold Schwarzenegger in the 80s helped create modern gym culture, and yet the torsos of Rocky or Conan the Barbarian are not exactly models of what we now desire as “fitness”: they are too extreme. Martschukat views them as ugly, even monstrous, but one might agree more with Arnie, who in the era of his pomp described himself as a sculptor: his body was a countercultural work of art, beautiful yet in some profound sense useless. In these times, just to slump back and eat crisps while watching Predator might, too, be a precious form of resistance.

• The Age of Fitness by Jürgen Martschukat, translated by Alex Skinner, is published by Polity (£20). To order a copy go to guardianbookshop.com. Delivery charges may apply.