Vicky Hallett is a freelance writer living in Florence.

At 5 a.m. every morning, Daniel Kunitz wakes up to exercise. He hits the gym again most nights. He shuns gluten and grains — not because he’s intolerant but because he doesn’t want to interfere with his training. He is prone to lying in pools of his own sweat while reveling in the kind of post-workout pain that makes other people want to vomit.

It’s a regimen that might make sense for an Olympian. But what could possibly possess the 47-year-old former editor of Modern Painters magazine to live this way? Kunitz explains it all in his book, “Lift: Fitness Culture, From Naked Greeks and Acrobats to Jazzercise and Ninja Warriors.”

The title conspicuously leaves out CrossFit, the fitness methodology responsible for Kunitz’s recent health kick. He was drawn in by its smorgasbord approach that encourages adherents to bounce between lifting, hauling, sprinting, jumping, climbing and practically anything else the human body can do. What enchanted Kunitz even more was the mind-set of “practicing for life” and constantly striving for improvement.

For Kunitz, a once-skinny dude incapable of climbing a flight of stairs without gasping for breath, CrossFit was an invitation to examine not just his fitness past but also that of humankind. He wondered, “Had we been working out the wrong way for thousands of years and only just, in my lifetime, stumbled onto a better path?”

"Lift: Fitness Culture, from Naked Greeks and Acrobats to Jazzercise and Ninja Warriors" by Daniel Kunitz (Harper Wave)

In “Lift,” Kunitz searches for answers by leaping back those thousands of years and then returns from antiquity to the present day, highlighting the trends and views that have paved the way for what he dubs “New Frontier Fitness,” or NFF. The “exemplar” of NFF is, of course, CrossFit. But Kunitz allows that some other contemporary physical practices make the cut, including parkour, obstacle racing and acroyoga (posing midair while balancing on a partner’s hands and feet).

[You’re thinking about fitness all wrong]

To qualify as NFF, according to Kunitz, an exercise routine must focus on functional movements. (In other words, actions useful outside the gym.) Another defining trait of NFF is that it goes beyond building muscles into something more “holistic” that addresses a person’s other needs, including nutrition, brain health, meditation and breathing.

And the thing that really separates NFF, he explains, is that it’s “not something you do for an hour three days a week but rather something that structures your life.” Anything less than complete devotion doesn’t count. “You don’t train aerobics or SoulCycle — these are essentially leisure activities, albeit beneficial, like a weekend soccer league,” he writes.

Kunitz’s insightful premise isn’t well-served by flecks of a fitter-than-thou attitude that can be off-putting. Throughout the book, he belittles low-to-moder­ate-intensity workouts. He chronicles his internal struggle over whether yoga counts as exercise. (“It provides almost nothing in the way of cardiovascular and strength adaptations,” he writes before reluctantly deeming it worthy.) At one point, he questions whether spin classes are “cosmetic products we’ve devised, akin to liposuction, bee venom, Botox, and butt implants.”

But even Kunitz admits that NFF-ers sometimes spend time just sitting on their squat-sculpted rear ends to gorge on “workout porn.” Online exercise videos “do pack a certain erotic charge,” he tells us. But the people glued to them are driven less by sexual prurience than by a search for “inspiration and the beauty of the accomplishments of the athletes in them.”

With that in mind, Kunitz introduces us to those naked Greeks from his subtitle. They always stripped before getting down to business at the “gymnasion,” but otherwise, their workout plans wouldn’t look so unusual in 2016, he suggests. They engaged in a mash-up of boxing and wresting “not unlike today’s mixed martial arts.” They ran. They jumped. They used weights. They lifted large things.

As time marched on, however, different ideas about fitness took hold, explains Kunitz, who puts us through an exercise history boot camp.

[Five myths about women’s sports]

We get the lowdown on the military training tactics that dominated the fitness world for the next several centuries. We learn why the German gymnastics movement developed out of a sense of patriotism. We find out the origins of the word “dumbbell”: It looked like a church bell without a clapper.

We meet a fascinating cast of characters, including Hippolyte-Antoine Triat, who spent his childhood performing a wire-walking act dressed as a girl. He grew up to be a strongman who would hang from a revolving column while lifting horses and men, and eventually, he settled in Paris and opened the world’s first commercial gym in 1850. He paved the way for Eugen Sandow, a “theatrical athlete” who fought a lion, posed in skimpy clothes and flexed for Thomas Edison’s kinetoscope in 1894. “These images constitute the first commercial film footage ever produced,” Kunitz writes.

The 20th century brought the establishment of bodybuilding, Muscle Beach, the President’s Council on Physical Fitness, the jogging craze — all of which, eventually, led to NFF.

Kunitz’s book is not the most traditional or thorough accounting of workout history. For instance, you won’t find the word “Pilates,” although there are several pages devoted to the Bartendaz, a Harlem crew that created awesome pull-up bar routines.

Kunitz explains that his goal was not “to rewrite the history of exercise” but to “synthesize that history into a series of arguments.”

One of his final points, and probably his boldest, is that NFF has shifted standards of acceptable behavior for women to the point of altering what society considers attractive — or at least, what Kunitz considers attractive: “It was only after being around high-performance women that their muscles came to stand for vitality, vibrancy, health, and therefore beauty. Now what passes for conventional female beauty strikes my eye as vitiated, and the soft flesh so many women display seems weak.”

Whether anyone is attracted to Kunitz when he is collapsed on the floor in his own sweat is left unaddressed.