Half of primary teachers lack the confidence to teach children how to swim - and even after specialist training they are less sure about giving PE lessons than secondary colleagues.
And attempting a forward somersault or negotiating a new dance routine with a class of eight-year olds is enough to instil fear into even the bravest teachers, according to a survey of more than 1,000 staff from across Wales.
The survey, by the Sports Council for Wales, suggests many primary and secondary teachers need a confidence boost in the more creative areas of PE such as gymnastics and dancing.
Teachers' confidence in traditional sports such as rugby is realtively high, but 59 per cent said they needed more professional development in gymnastics and dance, while 46 per cent said they need more support to teach outdoor adventure activities.
The study concludes that major investment is needed to provide the specialist support that would ensure high-quality PE and sports teaching in all schools.
Menna Sweeney, a PE teacher at Plas Crug primary, Aberystwyth, said:
"Teachers tend to lack confidence in things like gymnastics - but it's not so frightening when you've got the basic moves."
Plas Crug, along with the other schools surveyed, is taking part in the national PE and School Sport (PESS) action plan for Wales, adopted in 2001 by the Assembly government to promote greater physical activity in schools.
The plan is being managed by the sports council, which has funded coaching, training courses and other support, including visits from dance companies.
The survey assessed teachers' experiences of PE to find which areas needed more attention.
Teachers in schools which first piloted PESS in 2002 became more confident about their PE skills, particularly in gymnastics, but still wanted more training, the survey found. But overall primary teachers were less confident than their secondary counterparts.
Jonathan Moody, co-ordinator of PESS in Torfaen, said primary teachers lacked confidence as few have specialist training.
"It's important that more training is targeted at primaries so that children have a higher ability when they reach secondary school," he said.
Almost all secondary teachers questioned said they were "quite confident" or "very confident" in teaching games such as hockey and cricket (99-100 per cent), swimming (94.5 per cent) and athletics (99 per cent). But in primaries, only 62 per cent expressed similar confidence in athletics.
Levels were even lower for games (60-65 per cent) and swimming (50 per cent). Teachers in both primary and secondary schools wanted more support to teach gymnastics, dance and outdoor activities.
Research published last week showed that time given to PE has increased in Welsh schools. Pupils in Years 5 and 6 get an average of 93 minutes per week - up from 88 minutes in the previous year for Y5, and 86 minutes for Y6. In secondaries, time for PE declines as pupils get older - from an average 140 minutes per week for Year 7 pupils to 97 minutes for Year 11.
Dr Huw Jones, chief executive of the sports council, said there is still a long way to go to meet the target of two hours of PE per week for all pupils.
"Obesity and inactivity are some of the most pressing health issues facing us today," he said.
"For a long time, physical education has been the Cinderella subject of the curriculum. That is beginning to change."