If you think that running marathons will help you live a long and healthy life, new research may come as a shock. According to a recent scientific study, people who do a very strenuous workout are as likely to die as people who do no exercise at all.

Scientists in Denmark have been studying over 1,000 joggers (慢跑者)and non - joggers for 12 years. The death rates from the sample group indicate that people who jog at a proper pace two or three times a week for less than two and a half hours in total are least likely to die. The best speed to jog at was found to be about 5 miles per hour. The research suggests that people who jog more than three times a week or at higher speeds of over 7 mph die at the same rate as non - joggers. The scientists think that this is because strenuous exercise causes structural changes to the heart and arteries(动脉). Over time, this can cause serious injuries.

Peter Schnohr, a researcher in Copenhagen, said, “If your goal is to decrease risk of death and improve life expectancy(寿命)，jogging a few times a week at a proper pace is a good strategy. Anything more is not just unnecessary, and it may be harmful. “

The implications (暗示 ) of this are that moderate forms of exercise such as tai chi, yoga and walking may be better for us than “iron man events, triathlons and long - distance running and cycling. According to Jacob Louis Marott, another researcher involved in the study, “You don't actually have to do that much to have a good impact on your health. And perhaps you shouldn’t actually do too much”.

Researchers out of Australia’s Flinders University recently studied various physical reactions during sleep when exposed to noise. They found that certain levels of noise while sleeping, even those below recommended safe levels, may affect a person’s cardiovascular (心血管的) response. When slowly activated during sleep, these responses “could potentially have adverse effects on the cardiovascular system,” said researchers.

Researchers exposed 20 adult participants to various decibels (分贝) of wind farm and road noise while asleep, and then monitored physical responses including blood flow and heart rates as well as sleep awakenings. Although asleep, participants reacted to these noises, as found by the researchers.

For example, a 48-decibel (dB) noise, which is quieter than the 50-dB hum of a refrigerator, was 3. 4 times more likely to cause a change in participants’ pulse wave amplitude (脉搏波振幅), which is a measurement that relates to blood flow. Participants’ heart rates responded to the noise as well. After being exposed to a noise of over 40 dB, they experienced an increase followed by a decrease in their heart rates. The study noted that these sound levels are under the recommended 70 dB limit by the World Health Organization.

Physiological reactions that the study monitored, such as heart rates and blood flow, may root in the proper responses that may be “potentially needed to defend against threats during sleep,” researchers said.

Sleep is typically a time for the body to rest and recover, and noise-caused activation of these cardiovascular responses during sleep may prevent a person from getting the proper amount of healthy sleep they need.

Researchers noted that being exposed to noise pollution during sleep may increase the risk of cardiovascular disease, such as hypertension, heart disease, and other harmful health effects. To help reduce the potential increased health risks caused by frequent noise-caused sleep disturbances, researchers note that their findings help create public policies around noise levels during sleep.

Keeping a busy social life among lots of friends may keep people thinner than spending hours doing some exercises, according to scientists. They say that socialising and meeting with friends help increase levels of brown fat in the body which burns calories(卡路里)to produce heat.

However, scientists from Ohio State University now think that having a busy social life is an even more effective way of changing white fat into brown. The team came up with their theory by studying the effects of various living environments on mice. Those, who lived alongside a greater number of mice, had more space and toys to excite themselves and then lost far more weight over the course of the study than their “couch potato" fellows.