Walking, if you do it vigorously enough, is the overall best exercise for regular physical activity. It requires no equipment, everyone knows how to do it and it carries the     1     risk of injury. The human body is designed to walk. You can walk in parks or along a river or in your neighborhood. To get     2     benefit from walking, aim for 45 minutes a day, an average of five days a week.

Strength training is another important     3     of physical activity. Its purpose is to build and     4     bone and muscle mass, both of which shrink with age. In general, you will want to do strength training two or three days a week,     5     recovery days between sessions.

Finally, flexibility and balance training are     6     important as the body ages. Aches and pains are high on the list of complaints in old age. The result of constant muscle tension and stiffness of joints is     7     and simple flexibility training can     8     these by making muscles stronger and keeping joints lubricated. Some of this you can do whenever you stretch. If you watch dogs and cats, you’ll get an idea of how natural it is. The general     9     is simple: whenever the body has been in one position for a while, it is good to     10     stretch it in an opposite position.

Most people are aware of the need to keep their bodies healthy but what about their minds? Your brain is an     1     organ /order of the body, just like your heart, so it needs to be exercised! I retired last year and I found that after     2     nearly /merely a few months, I was getting forgetful and often couldn’t     3     locate /violate items such as my keys. I realised that I needed to make some changes to my lifestyle.

Now I do     4     crossroads /crosswords in the newspaper and other word     5     puzzles /puddles I find online. It helps keep me alert and my mind feels clear. I also realised that my diet was really poor and full of     6     junk /joint food. Now I’ve increased my     7     uptake /intake of fruit and vegetables. They     8     contain /complain lots of vitamins and minerals that are so good for my brain.

Finally, and probably the most difficult for me was joining some new clubs. It’s important at my age to get out of my     9     comfort /conflate zone. Making new friends and learning new skills keep the brain active. I joined a chess club in my local area and I enjoy it so much.

Low-salt diets are actually harmful to our bodies, a recent study found. These diets may actually increase the risk of developing heart disease, or even cause death. These findings, says WebMD, a public health website, are     1     to the popular wisdom that has long said low-salt diets are healthy.

The scientists, led by Andrew Mente of McMaster University, wanted to find out if the relationship between salt, strokes and heart disease is different for those who have high blood pressure. They found that whether one has high blood pressure or not, low sodium     2     increased the risk of stroke, heart attack and death.

The study goes on to suggest that only certain people should be     3     about reducing sodium in their diets. “The findings emphasize the importance of reducing salt intake among people with hypertension and who eat food with high levels of sodium,” Mente said. McMaster University’s Martin O’Donnell said, “This study adds to our understanding of the relationship between salt intake and health. The study also     4     the correctness of present guidelines that recommend low salt intake for everyone.”

He noted, “An approach that recommends salt in     5    , particularly focused on those with hypertension, appears more in-line with current evidence.” Mente added that the current general recommendations relating to the maximum healthy salt intake seems too low, especially since they do not consider an individual’s blood pressure.

Low sodium intake reduces blood pressure modestly, compared to average intake, but low sodium intake also has other effects. “One of those effects includes harmful elevation of particular hormones — and this     6     many benefits. The main issue is not whether very low sodium intake lowers blood pressure, but whether it results in improved health,” Mente said. In general, health experts consider a high level of sodium consumption to be over 6 grams daily. Mente pointed out that this indicates that many people around the world are taking in healthy amounts of salt. He also said that efforts should be    7     at reducing salt intake among the people who are most likely to get hypertension and who take in high amounts of salt. Mente does not agree with the current strategy of reducing sodium intake in almost all countries. However, he would accept efforts to reduce salt intake in some areas, such as China or Central Asia, where the average salt consumption is     8     high.

In Kenya, the Ministry of Public Health and Sanitation recommends general reduction of salt intake to levels below 5 grams as     9     by the World Health Organization. Less than 5% of people in the world consume such low levels of sodium. The WebMD report says Elliott Antman, past president of the American Heart Association (AHA) criticized Mente’s study. Antman says the study does not     10     measure sodium intake, and it should not make Americans stop worrying about salt. The American Heart Association continues to recommend less than 1.5 grams of sodium per day from all sources, he said.

Using dragonflies as contamination(污染) detectors

Mercury(汞)pollution from power plants and mining operations can end up in our air and water.

But it’s     1     to predict just how much of that environmental mercury will make its way into our food—and our bodies.

“We were working on developing a bioindicator, a biosentinel, that could inform us of the levels of mercury contamination across the US.”

Ecologist Collin Eagles-Smith of the United States Geological Survey and his colleagues came up with a practical way to     2     the scope of mercury contamination in an ecosystem by measuring mercury levels in a single species. Their bioindicator: juvenile dragonflies, or larvae(幼虫). Dragonfly larvae stay underwater, don’t move much, are easy to collect and live long enough to accumulate     3     amounts of mercury.

“If you have enough locations     4     with dragonflies, you can develop an index of the relative amount of mercury in the biological community. ”

The team measured mercury     5     in thousands of dragonfly larvae collected from waterways in 100 national parks during a 10-year period. And to amass the large sample number, they recruited volunteers through the Dragonfly Mercury Project.

The volunteers used dip nets to collect dragonfly larvae from their aquatic abodes(住所). National park staff then sent the larvae to laboratories for processing. For     6     the researchers also measured mercury concentrations(浓度)in other aquatic organisms.

“Using the relationships between dragonfly concentrations and fish concentrations, we were able to develop what we call an impairment     7     . ”

That index allowed the researchers to make health risk    8     at each sample site.

“About 12% of the locations posed what we consider to be high or severe risk of health impairments to fish, wildlife or humans if they    9     organisms from those locations. You can begin to build models that are predictive of how much mercury might be in a system and then apply that model to locations where you haven’t sampled dragonflies.”

“And that can inform future management actions to     10     the factors that are promoting the mercury production or simply inform agencies that may want to evaluate whether or not fish consumption advisories(警告)are necessary. ”

The study is in the journal of Environmental Science & Technology.

Studies have shown that the love children have for sugar may be innate. The preference for sweet foods is found to be already     1     in newborns, who prefer sweeter formulas (配方奶). There's further evidence that kids' taste buds are more sensitive to bitter-tasting foods, further pushing them to     2     for the sweets.

One study showed that adults tend to max out their sugar preference at about the level of sugar in a can of soda, but older children still liked drinks that were twice as sweet. The scientists couldn't find a limit to the     3     of sugar younger children preferred. It turns out that the kids still liked the sugary drink even past the point where there was too much sugar to be     4     in water anymore.

In the times of early humans, those who ate the most calories had a better shot at survival and thus at passing on their genes. Fruit, the most     5     natural source of sugar, could provide more energy than other sources of food, like vegetables, but was     6     scarce. So some scientists suggest that those early humans that ate the most fruit lived longer and had more babies. Those future generations may have then     7     to crave that sugary fruit as an important part of their survival.

Now, of course, sugar is no longer scarce and we     8     it in much larger quantities than the occasional rare fruit. So, in the evolutionary game of survival of the fittest, the fittest isn't     9     the one with the most sweets anymore.

Will we start to adapt to our new, easy     10     to refined sugars and eventually stop craving them? Perhaps, but that kind of evolution takes time.

When did the voice inside your head start talking? I became       1     of mine at about the age of 15. At night, I sometimes found it difficult to get to sleep because there was so much “mind chatter” inside my head.

In fact, mind chatter is quite common for human beings. Usually, whenever our       2     isn’t occupied, a stream of mental associations flows through our muds— thoughts about the future or the past, daydreams about alternative realities, or friends or celebrities. We often call this mental activity “thinking”, but this isn’t really accurate.

Real thinking suggests something active over which we have conscious(有意识的)     3    . It happens when we consciously use powers of reason and logic to make decisions and plans, organize our lives, solve problems and so on. But mind chatter isn’t like this. It’s random(随机的)and     4    , running through our head regardless of our desires and distracting us.

For example, imagine you’re thinking about what elective course to take for the next school year. As you are considering them, thoughts about your favorite subjects flood in,     5     you of a project that you really like. This makes you remember chatting with friends about some documentaries that       6     to young people. Suddenly, you remember the upcoming science fair and you worry about       7     your time. All these thoughts leave you struggling to       8    , and you end up seeking advice from classmates.

However, it’s       9     to expect to silence our mind chatter altogether. It’s such a natural part of our minds that it won’t disappear. We should accept it and treat I t as a kind of physiological process that takes place inside us but is not part of our identity. We don’t get our sense of identity from our digestion or blood circulation, so why should we       10     with the voice inside our head?