As we age, even if we're healthy, the heart just isn't as efficient in processing oxygen as it used to be. In most people the first signs show up in their 50s or early 60s. And among people who don't exercise, the changes can start even sooner.

"Think of a rubber band. In the beginning, it is flexible, but put it in a drawer for 20 years and it will become dry and easily broken," says Dr. Ben Levine, a heart specialist at the University of Texas. That's what happens to the heart. Fortunately for those in midlife, Levine is finding that even if you haven't been an enthusiastic exerciser, getting in shape now may help improve your aging heart.

Levine and his research team selected volunteers aged between 45 and 64 who did not exercise much but were otherwise healthy. Participants were randomly divided into two groups. The first group participated in a program of nonaerobic (无氧) exercise—balance training and weight training—three times a week. The second group did high-intensity aerobic exercise under the guidance of a trainer for four or more days a week. After two years, the second group saw remarkable improvements in heart health.

"We took these 50-year-old hearts and turned the clock back to 30-or 35-year-old hearts," says Levine. "And the reason they got so much stronger and fitter was that their hearts could now fill a lot better and pump (泵送) a lot more blood during exercise." But the hearts of those who participated in less intense exercise didn't change, he says.

"The sweet spot in life to start exercising, if you haven't already, is in late middle age when the heart still has flexibility," Levine says. "We put healthy 70-year-olds through a yearlong exercise training program, and nothing happened to them at all."

Dr. Nieca Goldberg, a spokeswoman for the American Heart Association, says Levine's findings are a great start. But the study was small and needs to be repeated with far larger groups of people to determine exactly which aspects of an exercise routine make the biggest difference.

When almost everyone has a mobile phone, why are more than half of Australian homes still paying for a landline (座机)

These days you'd be hard pressed to find anyone in Australia over the age of 15 who doesn't own a mobile phone. In fact plenty of younger kids have one in their pocket. Practically everyone can make and receive calls anywhere, anytime.

Still, 55 percent of Australians have a landline phone at home and only just over a quarter （29%） rely only on their smartphones, according to a survey （调查）.Of those Australians who still have a landline, a third concede that it's not really necessary and they're keeping it as a security blanket —19 percent say they never use it while a further 13 percent keep it in case of emergencies. I think my home falls into that category.

More than half of Australian homes are still choosing to stick with their home phone. Age is naturally a factor （因素）-only 58 percent of Generation Ys still use landlines now and then, compared to 84 percent of Baby Boomers who've perhaps had the same home number for 50 years. Age isn't the only factor; I'd say it's also to do with the makeup of your household.

Generation Xers with young families, like my wife and I, can still find it convenient to have a home phone rather than providing a mobile phone for every family member. That said, to be honest the only people who ever ring our home phone are our Baby Boomers parents, to the point where we play a game and guess who is calling before we pick up the phone （using Caller ID would take the fun out of it）.

How attached are you to your landline? How long until they go the way of gas street lamps and morning milk deliveries?

We live in a town with three beaches. There are two parks less than 10 minutes' walk from home where neighbourhood children gather to play. However, what my children want to do after school is pick up a screen — any screen — and stare at it for hours. They are not alone. Today's children spend an average of four and a half hours a day looking at screens, split between watching television and using the Internet.

In the past few years, an increasing number of people and organisations have begun coming up with plans to counter this trend. A couple of years ago, film-maker David Bond realised that his children, then aged five and three, were attached to screens to the point where he was able to say "chocolate" into his three-year-old son's ear without getting a response. He realised that something needed to change, and, being a London media type, appointed himself "marketing director for Nature". He documented his journey as he set about treating nature as a brand to be marketed to young people. The result was Project Wild Thing, a film which charts the birth of the Wild Network a group of organisations with the common goal of getting children out into nature.

"Just five more minutes outdoors can make a difference," David Bond says. "There is a lot of really interesting evidence which seems to be suggesting that if children are inspired up to the age of seven, then being outdoors will be a habit for life." His own children have got into the habit of playing outside now: "We just send them out into the garden and tell them not to come back in for a while."

Summer is upon us. There is an amazing world out there, and it needs our children as much as they need it. Let us get them out and let them play.