The most persistent theme in exercise science in 2015 was that to live long, age well and maintain a nimble mind and shapely brain, we must be physically active - but not for as much time as many of us might fear, or in the ways that many of us might guess.
Certainly the most encouraging research this year focused on the links between regular exercise and improvements in our thinking and the structure of our brains. I've often written in past years about how exercise - usually running, especially in animal studies - increases the number of new neurons in the brain and sharpens thinking skills and mood, especially as we age.
But this year, interest among scientists in exercise and brain health seemed to reach a critical mass. Many of the new studies highlighted previously unexplored ways in which exercise changes our brains and minds. One of my favourites was a brain-scan study in which Japanese scientists found that the brains of fit older men were almost as efficient as the brains of young people.
This finding meant, in practice, that the aerobically fit older men's brains used fewer resources during thinking than the brains of out-of-shape men of the same age, much as a fit body can use less energy to perform the same physical task as one that is less fit. This study introduced me to a cautionary scientific acronym, HAROLD, for hemispheric asymmetry reduction in older adults - a weakening of the function of ageing brains that I now fervently hope to avoid or lessen by regularly working out.
I may, though, add more gym visits to my usual routine because several studies this year looked for the first time at whether and how weight training and sturdy muscles affect the brain. In one of those studies, healthy older women who completed a yearlong, twice-weekly program of light resistance training showed fewer and smaller lesions in their brain's white matter afterward than women of the same age who had completed a stretching and balance-training program or gone to the gym only once a week. White matter connects and passes messages among different portions of the brain, so it is critical for memory and thinking.
Another study of muscular health and brain effects reached a similar conclusion. I found this study particularly intriguing because it looked at twins, of which I am one (although not identical). Twins are useful for exercise studies; they share so many of the same genes and usually early home environments, allowing scientists to better control for those factors.
In this study, British researchers used a large database of information about the health and habits of sets of fraternal and identical female twins, comparing the muscular power of each twin's legs - a good measure of overall muscle health - to her cognitive abilities 10 years later. And the more powerful a twin's legs had been, the better, in general, she performed on cognitive tests now.
Even more interesting, when the scientists scanned the brains of a few of the sets of identical twins in the study, they found that if one twin had had more powerful legs than her genetically identical sister a decade ago, she now tended to have significantly more brain volume and less "empty space in her brain" than her punier sister, according to the study's lead author. My twin sister and I are competing now to see who can visit the gym more frequently.
Of course, not all of the important exercise science this year involved the brain. One of those studies concluded that physical activity of any type and in almost any amount seemed to keep people physiologically young by reducing the fraying and shortening of their telomeres, which are tiny organic caps on the ends of our chromosomes.
Telomeres generally decline in length with age, just as the functions of the cell that contain them slow and degrade. Short telomeres indicate, in effect, that a cell is biologically old, no matter what its chronological age.
Scientists once thought that little could be done naturally to slow the shortening of telomeres and the aging of cells. But in this study, researchers found that people who reported participating in any physical activity, like walking, weight lifting and even gardening, generally had longer telomeres than those who reported being wholly sedentary, and the more types of activities that people reported trying, the longer their telomeres tended to be.
The most popular column I wrote this year, however, concerned new studies that examined the question of precisely how much exercise we probably need to live a long and healthy life. The answer, in a nutshell, is that any amount of exercise, no matter how slight, will probably decrease someone's risk for premature death, but the ideal exercise dose seems to be about an hour a day of moderate exercise, such as walking, and less if we ramp up the intensity of a workout and make ourselves really sweat.
If it helps to inspire you, other new science this year found that on days when we work out, we are also much more likely than not to have a beer. Happy New Year.
New York Times