Only 31 percent of schoolchildren in Korea were placed in the top two levels in the annual fitness test in the last five years, down from 41 percent in 2005. According to a report released by the Ministry of Education, Science and Technology on Wednesday, the number of students placed in the bottom two levels rose to 42 percent last year, up 11 points from eight years ago.

Among male high-school students, the older they were, the more unfit they became. Those born in 1990 recorded 8 minutes 16 seconds in the 1,600 m run when they were freshmen, worsening to 8 minutes and 40 seconds as they became juniors.

The deterioration seems to be due to diminishing exercise as the pressures of study increase. "Today's high-school students prefer to study in a classroom or do some relaxing indoor activities during their lunch break," a school principal in Seoul said. "It's not only due to increased college entrance competition but also changes in the way they relieve stress. Students now resort to playing computer and video games rather than outdoor activities."

In a survey of 4,946 students at 141 schools nationwide by the Ministry of Culture, Sports and Tourism last year, 60.6 percent of respondents said they took part in no physical activity other than physical education at school. Asked why, the majority of the students cited lack of time. "Students' body cycle has deteriorated. As they go to after-school crammers they are forced to live on fast food and stay up late," said Woo Ok-yeong from Health Education Forum.