Resistance training is good for kids, but needs to be supervised and tailored for them by a qualified professional, according to a consensus statement by 20 doctors and fitness experts.

The statement appears in the British Journal of Sports Medicine and is endorsed by the American Academy of Pediatrics, the International Federation of Sports Medicine and the U.S. National Collegiate Athletic Association (NCAA).

Resistance training - which can include light free weights, resistance bands or medicine balls, as well as push-ups and other body-weight-bearing exercises - can benefit young bodies and prepare them for active lives, the authors point out.

"You can look at the data from the Centers for Disease Control, kids are becoming less and less fit all the time," said Dr. Tim Hewett, director of the Sports Medicine Biodynamics Center at the University of Cincinnati, who was not involved in the statement. "There are lots of problems related to our current lifestyles."

Lack of strength and overall fitness, cardiovascular and musculoskeletal strength all contribute to poor health for kids, and resistance training can be a great option to help, but moderation is key, he said.

Though many parents fear their children will be injured during exercise or will damage their growing skeletons, childhood is actually the best time to use weight-bearing activity to build bone mass and kids are less likely to suffer sprains than adults, according to the statement.

Programs designed to promote conditioning and correct form for specific sports can also reduce the risk of injuries by 50 percent in kids and teens, the authors write.

"Clearly, participation in physical activity should not begin with competitive sport but should evolve out of preparatory fitness conditioning that is sensibly progressed over time," they write.

But these activities need to be supervised by "qualified professionals," like trainers or coaches, with strength and conditioning certifications.

These leaders need to know how to effectively communicate with kids and teens, as well as what exercises are best for kids and teens, and "how much is too much."

Position statements in support of resistance training like this one make it easier to inform parents and coaches who may still be hesitant, said Jeff Martin, who co-founded CrossFit Kids, a branch of the popular and sometimes controversial training program geared to kids from preschool age and up.

"With respect to resistance training, parents and coaches should always keep in mind that children are not simply miniature adults," Martin said.

Children, especially the youngest ones, benefit most from doing many reps of little or no weight, he said.

Hewett, a former power lifter, agreed with that premise, but expressed concern that CrossFit in particular may be too intense for kids.

"We have to get our kids more active but we can't overdo it," he said.

Kids need to have fun to be engaged, and can vary widely in their ability to pay attention and focus during sets of many reps of the same movement. When they drop weights, he said, they could injure themselves.

Martin recommends that preschool kids never use weights, and should focus instead on fundamental movements like squats.

The American Academy of Pediatrics recommends that eight year olds can start using light weights, but children mature at vastly different rates, Martin says, and some five year olds in his program start using very light objects or dumbbells.

"The key points are moderation, supervision and qualified professionals," Hewett said.

He and Martin agree that "qualified professionals" need more than just certifications, they need experience working with kids so they can assess a child's developmental and emotional maturity, since that can often be an important factor in how much is too much for each child.

"Parents should watch their children's trainers and see how the children react to them. Do they relate well and vice versa?" said Martin. "All the qualifications in the world will not help someone who cannot speak the language of the children or teens in their care."

Many people have long believed that eye contact is an effective tool in the art of persuasion. Yet, new research indicates that eye contact may actually create a bigger division among people who already have different viewpoints, Medical News Today reported.

In a study published in Psychological Science, researchers used an eye-tracking system to monitor how people responded to eye contact. In a range of situations, speakers attempted to persuade viewers of their opinion on a variety of controversial political and social issues. Overall, it appeared that the more time viewers looked at the speaker's eyes, the less likely they were to embrace their views.

Furthermore, eye contact only appeared to be linked to increased persuasiveness when viewers already shared the same outlook as the speaker, according to Medical News Today.

Researchers suspect that while eye contact can convey trust in friendly situations, it may imply hostility or aggression when people disagree with one another.

"Whether you're a politician or a parent, it might be helpful to keep in mind that trying to maintain eye contact may backfire if you're trying to convince someone who has a different set of beliefs than you," said co-study author Julia Minson, assistant professor of the Public Policy Center for Public Leadership at Harvard Kennedy School of Government.

More people survived cardiac arrests in Denmark after the country encouraged bystanders to step in and perform CPR, a new study shows.

Researchers found the proportion of cardiac arrest patients who got to the hospital alive and survived over the next year increased between 2001 and 2010 as the initiatives were introduced.

"The main message from this study is that national initiatives to improve cardiac arrest management seem to have an impact with an increase in bystander CPR rates and survival rates," Dr. Mads Wissenberg, the study's lead author from Copenhagen University Hospital Gentofte, said in an email.

Approximately 300,000 people in the U.S. go into cardiac arrest every year and about 90 percent of those die, according to the Centers for Disease Control and Prevention.

The American Heart Association says immediately starting CPR when a person goes into cardiac arrest - when the heart stops beating - can double or triple that person's chances of survival.

CPR, or cardiopulmonary resuscitation, involves pushing down onto a person's chest to keep oxygen-rich blood flowing to the body's vital organs until medical help arrives. For cardiac arrest, that help typically involves using an automatic external defibrillator (AED) to shock the heart.

According to the researchers, who published their study in the Journal of the American Medical Association, Denmark noticed about 10 years ago that few people stepped in to perform CPR and a minority of cardiac arrest victims survived more than 30 days.

The country took several steps to increase the number of people performing CPR. Those included introducing mandatory training for elementary school students and people getting driver's licenses, distributing instructional training kits, offering telephone guidance to bystanders and placing AEDs in public places.

To see whether those and other initiatives were linked to improved outcomes, the researchers analyzed data from 19,468 people who went into cardiac arrest someplace other than a hospital between June 2001 and December 2010.

At the beginning of the study, Wissenberg and his colleagues found that only about 21 percent of patients had a bystander step in to perform CPR during their cardiac arrest. By the end of the study in 2010, that number had more than doubled to 45 percent.

There was only a small increase in the use of AEDs, but that was expected because most weren't placed in public places until the end of the study.

Still, the researchers found the chance of people surviving cardiac arrest until they got to the hospital increased from about 8 percent to 22 percent. Their chance of survival after 30 days also increased from about 4 percent in 2001 to about 11 percent in 2010.

And the proportion of people who were still alive one year after cardiac arrest rose from about 3 percent in 2001 to about 10 percent in 2010.

But the credit for better outcomes doesn't belong to CPR alone, according to Wissenberg. He said increases in survival are likely linked to many factors, including events that happen before and after a cardiac arrest patient gets to the hospital.

The researchers also can't say the national initiatives directly caused the increase in participation or survival.

"Nevertheless, the results of this study indicate that the increased rate of bystander CPR was an important factor in improving survival," Wissenberg wrote.

Dr. Graham Nichol, professor of medicine at the University of Washington in Seattle, said implementing a national program like Denmark's is novel, compared with implementing smaller regional programs. He said it's something needed in the U.S.

"It's important that people know that this is an easy thing to do and everyone should learn it and learn how to respond to a medical emergency," Nichol, who wasn't involved in the new study, said.

"I'm optimistic that we can do that. It's going to take an ongoing effort from a lot of people to achieve that," he said.

Human brain can quickly understand words for big things, like whale, than 'small' words like plum, a new study has found.

Researchers at the University of Glasgow had previously found that big concrete words - ocean, dinosaur, cathedral were read more quickly than small ones such as apple, parasite and cigarette.

Now they have discovered that abstract words which are thought of as big ? greed, genius, paradise are also processed faster than concepts considered to be small such as haste, polite and intimate.

"It seems that size matters, even when it's abstract and you can't see it," Dr Sara Sereno, a Reader in the Institute of Neuroscience and Psychology, who led the study said.

Participants were presented with a series of real words referring to objects and concepts both big and small, as well as nonsense, made-up words, totalling nearly 500 items. The different word types were matched for length and frequency of use.

The 60 participants were asked to press one of two buttons to indicate whether each item was a real word or not. This decision took just over 500 milliseconds or around a half second per item.

Results showed that words referring to larger objects or concepts were processed around 20 milliseconds faster than words referring to smaller objects or concepts.

"This might seem like a very short period of time, but it's significant and the effect size is typical for this task," said Sereno.

"It turned out that our big concrete and abstract words, like 'shark' and 'panic', tended to be more emotionally arousing than our small concrete and abstract words, like 'acorn' and 'tight'. Our analysis showed that these emotional links played a greater role in the identification of abstract compared to concrete words," Lead author Dr Bo Yao said.

"Even though abstract words don't refer to physical objects in the real world, we found that it's actually quite easy to think of certain concepts in terms of their size," said co-author Professor Paddy O'Donnell.

"Everyone thinks that 'devotion' is something big and that 'mischief' is something small," O'Donnell said.

Bigger things it seems, whether real or imagined, grab our attention more easily and our brains process them faster even when they are represented by written words.

The study was published in the journal PLoS ONE.