Child obesity and the shock of encountering hard physical labour is preventing today's teenagers from becoming the next generation of jockeys and stable lads, research suggests.

They are unable or unwilling to withstand the rigours of mucking out and riding for hours each day.

A university academic found a worrying decline in young people considering a career in horse racing. While many such recruits would not have succeeded as professional jockeys, they are essential for forming the backbone of the industry as stable lads or racecourse managers.

Deborah Butler, a college tutor and stable lad, found that fewer teenagers were light enough or eager to tackle the relentless manual work of looking after horses. She will say in her PhD on the industry: “This once ready supply of potential staff has been gradually contracting due to low levels of unemployment, the urbanisation of society, the trend for young people to stay on in further education, the younger generation's increasing body size and their unfamiliarity with the very physical nature of stable and stud work.”

Her findings were welcomed by industry experts. Rupert Arnold, chief executive of the National Trainers Federation, said: “There is a problem with body size, urbanisation and career expectations. The number of horses each employee is expected to look after has risen in the last 15 years.

“It's a long day, hard work and in all types of weather. That contributes to the difficulty. Many young people now have expectations of a different sort of lifestyle. We're employing quite a lot of migrant workers.” He said it was possible that the economic downturn would encourage more young people to enter the industry.

Of the thousand young people joining the industry each year, only 20 will succeed in becoming jockeys. Many of those who failed to make the grade would traditionally have worked for racehorse trainers by grooming and warming up the horses.

Ms Butler, 49, combines her PhD and part-time tutoring role at the University of Warwick with rising at 4.45am four days a week to work at a stables, mucking out and washing off the horses, and riding them for three hours a day.

She said that stable lads needed to be fit and used to physical labour, adding: “I think that's partly why we are not getting young people in so much. They're almost divorced from that type of work these days.”

She added that levels of pay posed problems for recruitment. Teenagers start on about £10,000 a year and an experienced stable lad earns between £16,000 and £18,000. Body size was also an issue. Jump racing jockeys were normally about 9st (57kg), while flat racing jockeys would be about 8st.

“We all know about growing obesity levels among young kids - that's having a detrimental effect,” Ms Butler said.

Warwick university said that Ms Butler's research had uncovered a significant wastage of talent in the industry. It has created a foundation degree in the horseracing industry (business, management and practice), which is being tested with a pilot programme that began last month.