Detailed Instructions: In this task, you are given a text of many news articles seperated by special token "|||||". Your task is to summarize them.
Problem:A new research from the University of Manchester has found as to why athletes are more likely to have abnormal heart rhythms.Elderly athletes with a lifelong history of training and competing in endurance events like marathons, triathlons and iron man challenges can have heart rhythm disturbances, known as arrhythmias.The Manchester research in rodents, funded by the British Heart Foundation, shows molecular changes in the heart's pacemaker occur in response to exercise training.The finding overturns the commonly held belief that an increased activity of the autonomic nervous system causes this specific reaction to endurance training.While normal adults have resting heart rates between 60-100 beats per minute, hearts of endurance athletes can beat only 30 times per minute or even lower at night time when there can be long pauses between heart beats."The heart rate is set by the heart's pacemaker, but this is controlled by the nervous system. The 'vagal' nerves lower the heart rate and therefore it was assumed the low heart rate of athletes is the result of over activity of the vagal nerves," Dr Alicia D'Souza, from The University of Manchester and first author on the paper, said."But our research shows this is not the case. Actually the heart's pacemaker changes in response to training and in particular there is a decrease in an important pacemaker protein, known as HCN4, and this is responsible for the low heart rate," she added.The researchers say these molecular changes in the sinus node - the cardiac structure responsible for generating heart rhythm - may help us to understand the more frequent occurrence of heart rhythm disturbances or even loss of consciousness in athletes.The findings are published in the journal Nature Communications. ||||| Image copyright SPL 
  
 Athletes beware - endurance training may make it more likely that you will need a pacemaker, scientists believe. 
  
 A British Heart Foundation team found exercise in mice triggers molecular changes in the part of the heart that generates its natural beating rhythm. 
  
 This may explain why elite athletes have low resting heart rates and more risk of heart rhythm disturbances, they told Nature Communications. 
  
 However, the benefits of exercising still outweigh any risks, experts say. 
  
 If the findings are reproduced in humans they could have implications for heart health in older athletes -but much more research is needed before we could draw that conclusion Prof Jeremy Pearson, British Heart Foundation 
  
 Super-fit 
  
 Endurance athletes are generally very fit. 
  
 Yet, paradoxically, they are more likely to have heart rhythm disturbances, known as arrhythmias, especially as they get older - although the risk is still small. 
  
 Experts have suspected that this is because long-term training for extreme endurance events such as marathons and triathlons slows the heartbeat down. 
  
 While normal adults have resting heart rates between 60-100 beats per minute, hearts of endurance athletes can beat only 30 times per minute or even less at night time when there can be long pauses between heart beats. 
  
 Cyclists Sir Chris Hoy and Miguel Indurain reportedly had resting heart rates of 30 and 28 beats per minute. 
  
 The heart rate is set by the heart's pacemaker, which is controlled by the nervous system. 
  
 And so it was assumed that the low heart rate of athletes was a result of the autonomic nervous system going into overdrive. 
  
 How to exercise 
  
 Image copyright Romilly Lockyer 
  
 Adults should do 150 minutes (2 hours and 30 minutes) of moderate-intensity aerobic activity a week 
  
 moderate-intensity aerobic activity a week You don't need to get this target in one or two long sessions - you can spread it out across the week into smaller chunks 
  
 It's important to rest when you do vigorous-intensity aerobic activity, such as running. The body repairs and strengthens itself between workouts, and over-training can weaken even the strongest athletes 
  
 Make sure you warm up before exercise and cool down after by doing some stretches and gentle movements to help avoid injuries 
  
 But Prof Mark Boyett and colleagues, from the University of Manchester, say their new research suggests this is not the case. 
  
 Instead, the heart's in-built pacemaker changes in response to training. 
  
 By studying mice, they found that endurance exercise led to a decrease in an important pacemaker protein, known as HCN4, and that this was responsible for the low heart rate. 
  
 Prof Boyett said: "This is important because although normally a low resting heart rate of an athlete does not cause problems, elderly athletes with a lifelong training history are more likely to need an artificial electronic pacemaker fitted." 
  
 But he added: "Although endurance exercise training can have harmful effects on the heart, it is more than outweighed by the beneficial effects." 
  
 Prof Jeremy Pearson, Associate Medical Director at the British Heart Foundation, said: "This study shows the heart's electrical wiring changes in mice that exercise for long periods, and these changes in heart rhythm are sustained afterwards. 
  
 "If the findings are reproduced in humans they could have implications for heart health in older athletes. But much more research is needed before we could draw that conclusion." |||||
Solution:
Could exercise be—gasp!—bad for you? Well, not exactly, but there is a downside to too much of it, a new study from the British Heart Foundation has found. In mice, endurance-based exercises were linked with a drop in production for a key heart-regulating protein, resulting in lowered heart rates of the subjects, the BBC reports. The finding may explain why human fitness devotees often have lower resting heart rates—sometimes with dangerous lapses between beats—making them more likely to require a pacemaker as they age. In the past, people have believed that it's the nervous system's increased activity that tricks athlete's hearts into slowing down. "But our research shows this is not the case," says the lead author, according to the Times of India. "Actually the heart's pacemaker changes in response to training." But sorry, couch potatoes: The researchers said that overall, the benefits of working out exceed the drawbacks. (Click to read about a previous study suggesting that moderate runners live longer than those who log mega-miles.)