【推荐1】Since you're stuck at home and spring is approaching, now's the time to get busy with gardening and other household projects.    1    

Whatever you do, aim for a minimum of 150 minutes of exercise (such as walking, biking and swimming) each week.    2    

At home or anywhere else,you have the basics for building muscle (肌肉）：gravity and your body weight. From push-ups to planks, squats to sit-ups, and leg extensions to lunges, you can target all the major muscles of your arms, legs, chest, shoulders and the muscles of your belly, back, and pelvis (盆骨）using nothing more than your weight as resistance.

But, to increase the intensity (强度）of your strength training, add some resistance.    3     For example, you might purchase a set of dumbbells, barbells, or kettlebells in varying weights for home use. Or, as a more affordable and (literally) flexible option, you can buy a set of flexible resistance bands with varying tension levels for about$25.     4     And they allow you to modify (修改）your workout simply by changing your movements and/or increasing the resistance by shortening or lengthening the band.

    5     Do at least two to three sets of 12 to 15 repetitions of each resistance exercise on two to three days a week. Wait two to three minutes between sets, and give each muscle group 48 hours between training periods to recover.

【推荐2】Sports offer kids the ability to exercise while having fun, the chance to learn how to play as a team, and a good way to develop athletic skills. Despite these benefits, 70% of kids quit sports by the age of 13.     1    .

◆    2    .

Have you ever watched kindergarteners play soccer against another team of kindergarteners? It is both enjoyable and amusing. No matter what the score, all the kids have a good time and are happy.

    3    . The focus changes from having fun to practicing skills. Only the pre-teens with the best skills can get the most time in the game. What was a fun activity at age 5 becomes a source of stress and pressure for a pre-teen. Those who are not among the most talented players tend to quit and find something else they might be good at.

◆ It costs more.

    4    . Parents of a pre-teen are going to need to purchase a uniform, gear, and equipment. Teams need to travel to compete against teams from other schools or districts. Parents who want to watch the games now have extra gas costs to deal with.

Therefore, when an activity becomes expensive, parents start pushing their pre-teen to do well in it. Perhaps the parents complain that if their pre-teen is sitting on the bench, or isn’t the star player, the money wasn’t worth it. This adds extra pressure on a pre-teen who might quit the team.

◆ It’s the age.

Parents need to remember that pre-teens are going through a lot of changes. Their bodies are changing. School has become more challenging (and requires them to manage a lot of homework).     5     If your pre-teen’s friends quit playing soccer, your pre-teen might quit as well.

【推荐1】What you do after studying could have a big effect（影响）on how well you learn and remember. Today on Education Tips, we will explore two no-cost ways that can help you improve your learning: wakeful rest and sleep.

When many students finish studying, they often go straight to another activity. Perhaps they look at their phone or computer. They might even play a video game or watch television. But research suggests that resting after your study may help you remember what you have studied.

The basic idea is this: by stopping your activity after the study, your brain gets a chance to rest. Resting is difficult when you are playing computer games.

While this might sound unusual to you, many studies have explored the benefits（好处）of resting after learning —what is called “wakeful rest”.

A 2019 study found that both young and older adults were able to better remember information they learned after doing wakeful rest.

If you want to give “wakeful rest” a try, here are a few simple things to do. Rest quietly for five to ten minutes. Do not look at your phone, read stories or play games. It is really that easy!

Besides wakeful rest, sleep is also important for learning. The Division of Sleep Medicine at Harvard Medical School（HMS） notes that sleep helps people to learn in two ways. A report on the school’s website explains that “a sleep-deprived（剥夺）person cannot focus attention well and therefore cannot learn well”. It also says, “Sleep itself helps us to memorize and that memorizing is very important for learning new information.”

The National Sleep Foundation（NSF） suggests that adults between the ages of 20 and 64 get between 7 and 9 hours of sleep per day. Teenagers may need a little bit more, and people over the age of 65 may need a little less.

Try to get some “wakeful rest” after a study. Then try to get a good night’s sleep. That’s it —a simple, no-cost way to help you remember what you learn.

【推荐2】The elements other than hydrogen and helium(氦气) exist in such small quantities that it is accurate to say that the universe is composed of somewhat more than 25 percent helium by weight and somewhat less than 25 percent hydrogen.

Astronomers have measured the amount of helium throughout our galaxy(星系) and in other galaxies as well. Helium has been found in old stars, in relatively young ones, and in the distant objects known as quasars(类星体). Helium nuclei have also been found in cosmic rays that fall on the earth. Cosmic “rays” are not really a form of radiation; they consist of rapidly moving particles(颗粒) of numerous different kinds. It doesn’t seem to make very much difference where the helium is found. Its amount never seems to vary much. In some places, there may be slightly more of it; in others, slightly less, but the proportion of helium to hydrogen nuclei always remains about the same.

Helium is created in stars. In fact, nuclear reactions that turn hydrogen to helium are responsible for most of the energy that stars produce. However, the amount of helium that could have been produced in this manner can be calculated, and it turns out to be no more than a few percent. The universe has not existed long enough for this figure to be significantly greater. Consequently, if the universe is somewhat more than 25 percent helium now, then it must have been about 25 percent helium at a time near the beginning.

However, when the universe was less than one minute old, no helium could have existed. Calculations indicate that before this time temperatures were too high and particles of matter were moving around much too rapidly. It was only after the one- minute point that helium could exist. By this time, the universe bad cooled sufficiently. But the nuclear reactions that led to the formation of helium went on for only a relatively short time. By the time the universe was a few minutes old, helium production bad effectively ceased.

【推荐3】Born in 1823 in Wales, Alfred Russel Wallace was a man of modest means, but he had a passion for nature and he chose to follow it. He started out collecting insects as a hobby, but eventually his longing for adventure led him to explore the world.

Luckily for Wallace, Victorian Britain was discovering an interest in weird and wonderful insects, so the demand from museums and private collections for these beasts was growing. Wallace was able to make a living doing what he loved: collecting beetles and other insects.

But his first trip of exploring the world ended in disaster. Wallace proceeded to the Amazon in South America. Its giant forests promised a wealth of new species, sure to put him on the scientific map. The trip took 6 weeks and involved every mode of transport in existence at the time. After four years Wallace set off for home, but his boat caught fire in the middle of the Atlantic. Everyone survived, but Wallace had to watch in despair as his samples went up in flames — including live animals he was bringing home that were trying to jump free of the flames. But he did not let it stop him.

In 1854, Wallace set off on another adventure, this time to the Malay Archipelago. Wallace found himself humbled by the new and exciting things he saw. He later recalled: “As I lie listening to these interesting sounds, I think how many besides myself have longed to see with their own eyes the many wonderful and beautiful things which I am daily encountering.”

In 1858, Wallace wrote what became known as the “Ternate essay”: a piece of writing that was to change our understanding of life forever. In his essay, Wallace argued that a species would only turn into another species if it was struggling for existence. Henry W. Bates was one of many scientists delighted by the idea of evolution by natural selection. In a letter to Wallace, he wrote: “The idea is like truth itself, so simple and obvious that those who read and understand it will be struck by its simplicity; and yet it is perfectly original.”