Heart rate recovery impeded by screen viewing?

The authors surveyed 2,125 subjects without cardiovascular (CV) disease and with reliable measures of CV fitness from the National Health and Nutrition Examination Survey 1999-2002 (NHANES), which included a representative sample of the US population.

The speed of HRR one to two minutes after its peak during an eight minute exercise treadmill test was measured, with all participants being quizzed about their levels of physical activity and recreational screen viewing time over the past month.

 CV health factors including weight and height, tobacco and alcohol consumption, and an array of biological factors such as blood pressure and levels of an inflammatory marker, called C reactive protein, were also measured.

In both men and women, prolonged bouts of screen time were independently associated with longer HRR, even after accounting for other influential factors. Females with prolonged screen viewing time tended to have unfavourable metabolic patterns.

In participants with low and middle physical activity, the screen viewing time had a graded inverse association with HRR, while in the high physical activity group the associations were not significant. This suggests that regular exercise may counteract the potentially harmful effects of prolonged screen viewing, say the authors.

Sitting in front of a screen is associated with much less energy expenditure than other sedentary behaviours, such as reading, writing or driving, say the authors.

 They speculate that this, as well as the unhealthy eating patterns associated with excessive screen viewing, may explain the link with diminished HRR, calling for further prospective studies into the causal relationship.

References

1. Chen JJ, Lee HH, Lin LY, Lai LP, Hwang JJ, Lin JL, Tseng CD. Prolonged screen viewing is independently associated with impaired heart rate recovery. Heart Asia 2010; doi:10.1136/ha.2010.2782
   Available from: http://heartasia.bmj.com/site/misc/heartasia2782.pdf