THE growing trend of ''cult fitness regimes and over-zealous personal trainers'' has led to a four-fold increase in the number of patients aged under 30 suffering hip, knee and back problems, according to a leading orthopaedic surgeon.

Gorav Datta, who is based at Southampton General Hospital, said the adoption of high-intensity workout regimes had contributed to bone and joint damage not normally seen until people reach their late 50s and 60s.

He said busy lifestyles had led to an increase in popularity of ''explosive'' exercise programmes and indoor cycling among people of all levels of fitness and ability.

He said: ''Over the past few years there has been a real expansion in the fitness market designed to meet the needs of young people with many conflicting priorities to contend with,'' explained Mr Datta.

''Cult fitness regimes and the use of over-zealous personal trainers, all of which emphasise high-intensity, high-impact work, appeal to those who want to cram exercise into their hectic daily lives.

''The problem, however, is that these short and intense bursts and repetitions can wreak havoc with joints and, longer-term, lead to the need for surgery.''

Some of the popular training regimes, which can be performed at gyms or at home, can consist of a range of repetitive aerobic exercises, body weight exercises, weightlifting and gymnastics which are performed in 30-minute to hour-long workouts.

Mr Datta said he now sees 200 patients a year who are under 30 and suffering from hip and knee injuries, as well as back problems, compared to around 50 three years ago.

He said: ''I now see patients under 30 who have the types of bone and joint injuries we would previously have expected to see in people in their late 50s and 60s, with around a quarter requiring surgical intervention.

''The message for young people to avoid this predicament is to be careful not to over-train and to avoid some of the exercises and training regimes that can trash the joints.

''That can be achieved by adopting more moderate workouts with adequate rest days and periods in between, while those with established joint problems could look to non-impact options such as swimming and cycling.''