NEW YORK • If we want to walk easily and well as we age, we may need to do more than just stroll now, according to an eye-opening new study of older walkers and cyclists. The study finds that people who often cycle for exercise can walk more efficiently than people whose primary exercise is placid walking, even if everyone works out for the same amount of time.
The results, which build on earlier work involving walkers and runners, raise important questions about whether gentle exercise, by itself, is enough for our well-being or if we might need, at least sometimes, to add oomph to our workouts.
In general, exercise science shows that doing something - anything - physical is much better for our health and longevity than doing nothing. A raft of epidemiological studies indicate that if men and women start moving just enough to lift themselves out of the group of people who are the most sedentary, they get greater reductions in their risks for chronic diseases and premature death than if a marathon runner crams in a few additional, weekly kilometres.
But most of us are not completely inactive or in constant motion and, for us, many questions remain about the ideal mix of duration, intensity or type of exercise to elevate our fitness and health. Can we get away with an occasional amble around the block? Or should we keep going for a longer period? And is it important to intentionally get out of breath on occasion?
Intrigued by those concerns, a group of exercise scientists at Humboldt State University in California and the University of Colorado at Boulder began to wonder recently about walking and whether it might tell us something about workouts and ideal intensities.
In general, most of us can walk from the time we are toddlers and probably expect to continue to be able to walk for most of our lives.
But past biomechanics studies show that people tend to become physiologically inefficient walkers with age, using more oxygen to walk at the same pace as younger people. In practical terms, this rising inefficiency would make walking feel harder and more tiring, perhaps prompting older people to walk less, sit more and potentially become frail.
The researchers speculated that exercise might maintain walking efficiency in older people, although what type of exercise was not clear. So, for a study published in 2014 in PLoS One - an open access peer-reviewed scientific journal published by the Public Library of Science (PLoS) - they invited healthy walkers and runners who were 65 or older to the lab and asked them to walk on a treadmill at various speeds while wearing headgear to measure their oxygen consumption.
They then compared the runners' and walkers' efficiency and crosschecked those results against similar data from earlier experiments with sedentary college students and retirees. It turned out that older runners were quite efficient walkers, using about the same amount of oxygen to walk as young people. But the older walkers had lost a step, physiologically, requiring about 7 to 10 per cent more oxygen to walk at the same pace as the runners or the students. Their efficiency matched that of the older men and women who rarely exercised.
For the new study, which was published in July in the Journal of Ageing and Physical Activity, the researchers set out to see if a different exercise, in this case cycling, might likewise affect the ease of walking.
They recruited older riders and walkers and asked them how strenuously they felt they worked out, on a scale of one to three, from easy to tiring. The walkers' reported intensity hovered at just under two, while the cyclists', as a group, neared three. The researchers also brought in a group of healthy young people as a control.
Everyone then walked on a treadmill at paces ranging up to over 6kmh while the researchers tracked their oxygen consumption. As with the runners, the older cyclists walked well, their efficiency matching that of the young people. But the older walkers' efficiency was as much as 17 per cent lower.
Higher oxygen consumption up to this level by older walkers compared with older cyclists in a treadmill test.
In effect, walking for exercise seemed not to have "supplied sufficient physical stimulus" to maintain people's ability to walk easily as they aged, says Justus Ortega, a professor at Humboldt who co-authored both studies. Running and cycling were associated with more efficient walking than regular walking was.
The studies did not delve into how cycling or running might have affected people's walking efficiency. But Dr Ortega says he and colleagues suspect that the more demanding exertions boosted the health and function of mitochondria inside muscle cells in ways that gentler walking did not. Mitochondria affect how cells make and utilise energy. Healthier mitochondria should contribute to more efficient movement.
These studies were single snapshots of people's lives, and do not show that running or cycling directly caused people to be efficient walkers, only that the activities were related. They also did not look at middle-aged people and whether different types of exercise might affect how well people walk later.
But Dr Ortega believes the studies' findings can be both cautionary and encouraging, suggesting that, while any physical activity is worthwhile, pushing yourself a bit now might yield lasting benefits for health and mobility.
So, if you currently stroll for exercise, he says, perhaps consider cycling or jogging sometimes, too, if possible. Or add hills to your usual walking route, or, at least for a block or three, pick up the pace.