How dangerous are treadmills?

Treadmills are the top selling piece of gym equipment in the US

It will surprise no-one familiar with the relentless whir of a treadmill to learn they were once used to a punish inmates in 19th century British workhouses.

Now, of course, no self-respecting gym is without one. They are comfortably the best-selling piece of gym equipment in the US.

They appeal to everyone from amateurs to Olympians, if nothing else, because it may seem a far more comfortable option than pounding the streets in the depth of winter.

But how safe are they?

The question has been raised by the sudden death of Silicon Valley entrepreneur, Dave Goldberg, who was found lying next to a machine at a Mexican resort.

The SurveyMonkey chief executive had slipped, banged his head and later died of his injuries.

Treadmills were used as a form of punishment in Britain during the 19th century

About 24,000 people were admitted to US hospitals last year with treadmill-related injuries, the Consumer Product Safety Commission (CPSC) estimates, with slips and strains the most common causes.

But deaths are rare, with 30 reported deaths over a 12-year period to 2012, according to the CPSC, and not all of these are caused by hazards specific to treadmills. Some people suffer heart attacks from the exercise, for example.

Indeed, you are more likely to be killed by lightning than by exercising on a treadmill. According to the National Oceanic and Atmospheric Administration, 261 people died in the US after being struck by lightning between 2006 and 2013.

Children, however, are at particular risk.

The daughter of US boxer Mike Tyson died after becoming entangled in the cable of a treadmill, and there are numerous cases of children suffering severe friction burns after trapping fingers and hands in the revolving belt.

Australia has even launched a public campaign on the dangers of treadmills to young children.

Regardless of risks, experts say exercise is better than inactivity

Few gym companies in the UK approached for information responded, but LA fitness said that the number of people injured on treadmills was "low - just 2% of all our accidents".

The company recommends being properly inducted on machines, knowing the safety features, having water at hand and not looking at your feet when you are running as among the best ways to stay safe.

And any inherent risks in with exercise need to be contrasted with the risks of inactivity.

Advice on exercising can appear confusing - one recent report suggested that intensive training may be as bad as not jogging at all.

But World Health Organization advice remains that adults should do at least 75 minutes of vigorous exercise a week.