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I'll admit it: I stifled a yawn while flipping through the American College of Sports Medicine's forecast for fitness trends for 2018. The top prediction? High-intensity interval training – the same trend that topped the list back in 2014 and has been in the top three ever since.

It's not that I'm a HIIT skeptic. In fact, my legs are quivering at my adjustable standing desk (see "Hot Health Trends of 2011") as I write this, thanks to a punishing but exhilarating series of 30- and 60-second sprints I ran this morning. But it's hard to resist the urge to seek novelty – to uncover the Zumba of 2018 before everyone else knows about it.

In reality, of course, new knowledge arrives at ultramarathon pace, not in a sprint. Fads come and go, but meaningful trends take time to catch on and they stick around for more than a few years. It's safe to place HIIT in the latter category now.

And it's also a safe bet that most of the big debates and hot topics in the science of fitness in 2018 will be about ideas that have already been percolating for a few years. Which ones will actually lead to meaningful changes in our habits? Here are my predictions.

Compression of morbidity

Back in 1980, Stanford University professor (and 3:09 marathoner) James Fries suggested that fitness research should shift its focus from simply prolonging life to prolonging years of healthy, independent, disease-free living. We will all eventually get sick and die, but ideally, we can compress this period of ill health, or "morbidity," into as short a period as possible.

Everyone thinks this is a great idea in theory. But in practice, it remains far more difficult to measure "healthspan" in long-term studies than it is to simply use death as a convenient outcome measure. That's starting to change, though. At physiology and sports-medicine conferences this fall, I heard more discussion about the importance of functional outcomes such as being able to get up from a chair without assistance as you age.

One of the consequences of this shift, I suspect, will be more emphasis on the benefits of resistance training, which may do more to prolong healthspan than lifespan. But I shouldn't prejudge the results – let's see what the newly focused research reveals.

Individual variation

The hottest topic at the Canadian Society for Exercise Physiology conference in October was individual variation. If 100 people follow an identical exercise program that boosts fitness by 10 per cent on average, the individual results will be all over the map. Some will gain more, some less and some may even lose fitness.

Most of the sometimes-acrimonious debate in recent years has focused on the extent to which this variation is genetic and unchangeable, so that non-responders will always fail to respond, rather than the results being simply random. Resolving this debate is much trickier than it seems, since exercise studies are inherently long, difficult to measure and impossible to repeat.

It's a safe bet that the answer is somewhere in the middle. But the more interesting question, which new research is beginning to tackle, is how to eliminate, or at least minimize, this variation. How do we alter exercise programs – in amount, intensity, or type of activity – to give each person the stimulus they need to achieve a certain threshold of improvement? The answers won't be easy to find, but they'll be worth waiting for.

Personal agency

It's a cliché to note that exercise is a miracle drug that few people are willing to take. What's less often acknowledged is that people have trouble sticking with real drugs, too. Fewer than half of patients who are prescribed statins are still taking them a year later; it's as low as a quarter after two years.

The point, according to Mayo Clinic physiologist Michael Joyner, is that health-promotion plans that rely on personal agency are doomed to mediocre results. If you want people to bike to work, build bike lanes and change traffic patterns rather than just telling them to bike; if you want pregnant women to take folic acid, add it to flour.

Such efforts are sometimes derided as "social engineering," and they certainly require robust debate and careful testing before implementation. But given the direction of current health trends, the time for that debate is now.

Case studies

A few months ago, exercise physiologist Trent Stellingwerff published nine years of data on his wife's weight and body-fat percentage. He's still married. His wife, Hilary, is a two-time Olympic 1,500-metre runner and the case study represented an extraordinary peek into the intimate practicalities of training for elite sport.

These days, studies that don't have hundreds of subjects are often dismissed as meaningless. But while Stellingwerff's paper isn't a "study" in the usual sense of the word, it offers insights that simply aren't available from the usual experiments on average college students. Similarly, another recent paper revealed detailed breakdowns of the training of 2016 Olympic champion rowers Hamish Bond and Eric Murray of New Zealand (quaintly referred to as Rower A and Rower B in the text).

In an age of big data and wearable "smart" technology, sports scientists around the world are accumulating mountains of data on remarkable individuals – and they're starting to share some of the insights, which will help all of us learn more about the capabilities of the human body.

Play-based fitness

Maybe this one is just wishful thinking on my part, since my eldest daughter will be starting kindergarten in 2018. I've read the pedagogical literature on "play-based learning" – and it just makes so much sense that I can't help applying the same principles to fitness, both for kids and for adults.

When I speak to other parents of young kids, we all have concerns about overscheduling and formalizing outdoor games – about year-round toddler soccer supplanting Calvinball. And I hear similar complaints about the purgatorial nature of much adult exercise.

So, whether it's a real trend or not, that's my resolution for 2018: to play more. To get outside, explore, try new things and tire myself – and my daughter – out. Even if I don't get fitter, at least I'll have fun doing it.

Alex Hutchinson's new book, Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance, will be published in February. Follow him on Twitter @sweatscience.