What is the story?
Last week's newspapers reported good news for those who never quite make it out of bed for their morning run - psychologists have discovered that running alone is bad for you.
Exercising alone causes stress and reduces the production of brain cells, at least in rats, the newspapers stated.
Researchers found that rats exercising on their own generated fewer brain cells than those doing so in the company of other rats. Solo exercise also reduced their ability to cope with shocks.
What was the research?
Researchers divided a group of rats so that half lived alone and half in groups. Half of each group were then given a wheel to run on for 12 days, while the other half had no exercise.
The researchers found that rats exercising in groups grew more brain cells in the hippocampus than rats living in groups that did not exercise.
Rats living alone but not exercising had fewer new brain cells than those living in groups, and rats exercising alone had fewer still.
The study concluded that in a group setting, running stimulates neurogenesis, but in social isolation, the positive effects of exercise are suppressed.
In addition, rats exercising alone had higher levels of the stress hormone corticosterone than control isolated rats, or those living in groups, indicating that these animals dealt less well with the stress of being handled by the researchers.
To test the effect of social environment and exercise on the rats' response to stress, the experiment was repeated, with the addition of a daily cold swim. This had no effect on the growth of new brain cells in rats exercising in a group setting, but it further reduced the growth of new cells in the brains of rats running alone, compared with isolated rats that did not exercise.
What did researchers say?
Lead researcher Dr Elizabeth Gould, professor of psychology at Princeton University in the US, said that it was important to note that this work was not directly related to humans: 'Rats have a strong drive to run. All rats run, given access to a wheel. This is not the case for humans. If it were, there would hardly be an obesity epidemic.'
Dr Gould added that the conditions in the study were extreme and would not apply to most people: 'The rats living alone were isolated, as if in solitary confinement. People living alone have a lot of social contact.
'I don't think there is any concern that physical activity will harm the brain.
'While I don't think this work is directly relevant to humans, it adds to the literature suggesting that positive social support can alter body and brain response to stress,' she said.
What do other experts say?
Dr Anne Haase, an expert on exercise nutrition and health at the University of Bristol, said there was no evidence for similar effects in people.
'Jogging is not bad for you. All of the research that has been carried out shows that any kind of exercise is mood-enhancing. It relieves stress and is just all round good for you.'
But Dr Haase added that making exercise a social activity was a good idea.
'Exercising with others is known to aid the development of social groups. Social support has health benefits of its own, as well as making exercise more enjoyable and helping people stick to an exercise programme if they find it difficult.'
Professor Angela Clow, leader of the Psychophysiology and Stress Research Group at the University of Westminster, agreed that exercising in groups might have added benefits. 'It seems unlikely that exercising alone would have any noticeable effect on humans. But this research underlines the link between stress and social interactions.
'It is well known that social support buffers glucocorticoid levels in humans as well as animals. For example, research on women with breast cancer shows that the more social support they receive to help them deal with it, the lower their levels of the stress hormone cortisol.
'This research is a superb example of the effects our social circumstances can have on our stress response. But it is important to remember that evidence from human studies shows exercise is a good way of dealing with stress, and this applies whether alone or with others,' she said.
- This is the first finding of a negative effect in animals exercising alone; it is unlikely to apply to humans.
- Exercise has proven benefits for mental and physical health.
- Social support is known to reduce stress levels and make exercising easier.
WHAT THE PAPERS SAID
"Running on your own may not be good for you" - The Times
"Jogging on your own 'is bad for you" - Daily Mail
"Solo running offers few benefits" - BBC