ALARMING - that's how medics and educators describe the fact that Irish children and adolescents are spending large chunks of their free time in sedentary pastimes.

The fact that many children now obtain little or no exercise means that, as a nation, we are storing up trouble for ourselves and condemning our children to a future of sickness and ill health, they argue.

Time was when most kids walked or cycled to school and almost everywhere else. Out of school, children spent their days kicking or juggling balls, running, jumping, skipping, playing hopscotch and generally being involved in physical activity.

Nowadays, most children are bussed or driven to school, and they spend much of their leisure time listening to music, watching TV, playing computer games or simply hanging about.

A survey of second level schools conducted by the Public Health Department of the South Eastern Health Board in 1992, shows that fewer than half of 14 year old boys and just under one fifth of girls take vigorous daily exercise. By the time they are 16, only 14 per cent of boys and 8 per cent of girls are taking such exercise.

Once they turn 16, even fewer girls - 2 per cent - continue to take regular vigorous exercise. Almost half of 15 year old girls exercise only once or even less often each week, compared with 13 per cent of boys in the same age group, according to a survey of second level students in the North Western Health Board region undertaken by UCG's Centre for Health Promotion Studies during 1993-94.

In order to be aerobically fit, children, teenagers and adults all need to take vigorous exercise for 20 minutes at least three times a week, medical experts say.

"Lack of exercise contributes to cardiovascular disease later in life," notes Dr Mai Mannix, a South Eastern Health Board area medical officer. "It's important to get children into the habit of exercise from an early age." Exercise too has psychological benefits and is a great means of relieving stress, she says.

It also plays a significant role in the prevention of osteoporosis (brittle bone disease) among women. "Exercise - particularly weight bearing exercise (running, jumping and skipping) - is the best and simplest way of maintaining bone mass and avoiding osteoporosis," Mannix advises. The fact that so many girls are avoiding regular exercise is of particular concern.

According to Dr Moira O'Brien, professor of anatomy at TCD, the incidence of 17 and 18 year olds with very low bone density is on the increase.

Primary school children, too, are less active than they ought to be. A survey of over 1,100 national school children conducted in 1991 by Dr Tony Watson, director of the Growth and Development Research Centre at UL, shows that almost half of boys and nearly three quarters of girls fail to attain minimum levels of aerobic exercise - while similar numbers of 11 and 12 year olds spend more than 90 minutes on their homework each evening.

The study, which was published in the Irish Journal of Medical Science, also shows that Irish children are overweight and score poorly in aerobic fitness tests. The study reveals poor flexibility and posture defects among seven to 13 year olds.

"These could contribute to back pain and joint problems in later life," Watson says. In terms of European norms, Irish children also exhibit poor upper body strength. "They should be using their arms and shoulders more than they do climbing up ropes and wall bars and doing hand stands," he says.

It's all too easy to blame children and young people for their inactive lifestyles, but much of their physical activity has been curtailed in recent years because parents - with considerable justification - fear that city streets and country roads are no longer safe for them.

Similarly, pupils now enjoy fewer opportunities to play spontaneous physical games in the schoolyard, because many schools fear being sued if anything goes wrong. The fact that relatively few parents are involved in regular exercise also lessens the likelihood of children taking exercise.

"When I came to Ireland two years ago from Australia, I was shocked to discover so many teenagers hanging around city and town centres at weekends - when most young Australians would be involved in sport," says Paul Kestel of Champion Sports. But Irish youngsters have relatively little opportunity to participate in sport because of a general lack of facilities and inadequate sports and PE programmes in many schools, he says.

PE is compulsory in our national schools. However, the Limerick study shows that only a minority of schools have satisfactory physical education programmes; in the vast majority of schools only one hour of physical education is offered each week and in a significant number of schools no PE is undertaken at all. Some teachers are reluctant to take PE classes because they feel unqualified or they fear accidents leading to personal injury claims.

Many national schools also lack the physical space in which to hold PE classes.

At second level, PE is a non compulsory part of the curriculum, but it is recommended that a minimum of two hours per week is allocated to PE. However, "while many schools offer PE, the number of hours drop off as students go up through the school," says Grainne O'Donovan, chief administrator of the Physical Education Association of Ireland. Almost one quarter of second level schools offer no PE in first year - by final year over 40 per cent of schools fail to offer PE, she says. Fewer than three quarters of all second level schools employ PE specialists.

It is estimated that only half of all post primary schools have access to fully equipped sports halls. Field games dominate the physical activity programme in Ireland. "Seventy per cent of the time is spent on field games - rugby, soccer, hockey," she says. "There is a tendency for children who only associate activity with major games, which are overly competitive and highly structured, to discontinue physical activity once they leave school. They may have no opportunity to discover other activities, including walking, swimming, cycling, squash or tennis," she says.

"You can end up with a small elite who continue and a huge majority who are totally turned off sport.

One of the by products of the fact that schools are now much larger than in the past is that fewer children may get the chance to participate in sport in schools, where success on the playing field is all important.

"In the old days, when schools were smaller, everyone had to turn out to make up a team," explains Pat O'Connor, headmaster of St Enda's Community School, Limerick. "Nowadays, in times of increased competition, the emphasis is often on the first 15 only, and many competent young players are consigned to the sidelines and never get a game."

The message that these children receive is that they are "also rans", he says.

Although it is widely accepted that team games instill the virtues of team spirit and co operation into young people, many educators argue that individual sports also have an important role to play.

"Individual sports give young people the chance to achieve personal bests. They learn to manage their own bodies and to understand that they can make a difference through their own efforts," O'Connor says.

"This is an important concept for young people to gain and which they can apply to other areas of their lives - study, drinking and finance for example."