Higher physical activity duration linked to better cardiorespiratory fitness in Asian adolescents

More than 60 minutes a day of moderate-to-vigorous physical activity (MVPA) may lead to better cardiorespiratory fitness (CRF) in Asian adolescents, according to the Asia-Fit* study.

“The main finding in our study indicates that higher durations of MVPA (≥60 minutes/day) can attenuate the detrimental effects of sedentary activities on CRF for Asian adolescents … [and also] showed that MVPA was more closely associated with CRF than television [(TV) viewing] time among Asian adolescents,” said the researchers.

This cross-sectional study involved 9,553 adolescents (5,094 boys and 4,459 girls, aged 12–15 years) who were recruited from eight Asian metropolitan cities (Tokyo, Hong Kong, Shanghai, Taipei, Bangkok, Kuala Lumpur, Seoul, and Singapore). IPAQ-SF** was used to assess self-reported MVPA and TV viewing time, and CRF was evaluated by using a 15-metre PACER*** test to measure aerobic fitness. [BMC Public Health 2019;19:1737]

The most active adolescents were observed in Tokyo, with MVPA of 73.5 minutes/day; while the least active adolescents were in Shanghai, with MVPA of 37.9 minutes/day.

Adolescents who logged the longest TV viewing time was reported in Kuala Lumpur at 2.88 hours/day, followed by Tokyo at 2.50 hours/day, and Bangkok at 1.81 hours/day.

A significantly better PACER z-score was observed among adolescents with higher MVPA (60 to <90 and ≥90 minutes/day) compared with those with lower MVPA durations (<30 minutes/day; ß=0.322; p<0.001 for boys and ß=0.256; p<0.001 for girls), after adjusting for age, city, and body mass index. Even with further adjustment for TV time, the results remained significant (ß=0.323; p<0.001 for boys and ß=0.253; p<0.001 for girls).

In a joint analysis of MVPA and TV viewing time, adolescent boys and girls with higher MVPA duration showed better PACER z-scores overall than those with lower duration of MVPA, regardless of TV time. 

Specifically, among the girls who had MVPA duration of 30 to <60 minutes/day, those who reported a longer TV viewing time (>2 hours/day) demonstrated a poor PACER z-score than those with a shorter TV viewing time (<1 hour/day). However, this trend was not seen in boys with MVPA duration of 30 to <60 minutes/day.

­“Although MVPA appears to be more important than time spent watching TV in relation to CRF among Asian adolescents, the present study … suggests that reducing daily TV time may still be beneficial for improving CRF, at least for physically inactive girls (MVPA <60 minutes/day),” noted the researchers.

“This has important implications because girls are usually less active than boys, and most girls do not meet physical activity recommendation,” they added.

“Our findings from the joint analysis demonstrated that if sufficient MVPA is accumulated[, especially in girls], the detrimental influences of TV time can be attenuated regardless of time spent watching TV. The level of MVPA required to attenuate the negative effects of TV viewing was ≥60 minutes/day of MVPA, which is congruent with the international youth physical activity guidelines,” the researchers said. “The present study [also] suggests that if prolonged sedentary behaviour is unavoidable, performing greater durations of MVPA is important for improving CRF.”

*Asia-Fit: Cross-cultural comparison on physical fitness, physical activity, and obesity on youth among major cities in Southeast Asia

**IPAQ-SF: International Physical Activity Questionnaire-Short Form