Watching fitness DVDs at home harms you

"The findings showed that imagery in fitness videos may be perpetuating and reinforcing hyper-sexualised and unrealistic body images," said Brad Cardinal, a Kinesiology professor at the Oregon State University.

De-motivating statements that could reduce the effectiveness of the workout -- diminishing the user's hope and potentially causing psychological harm -- were also found in the fitness DVDs.

For the study, the researchers reviewed 10 popular, instructor-led fitness DVDs, evaluating both the imagery used in the videos as well as the motivational language used by the instructors.

The goal was to better understand the visual and auditory messaging and how it might affect users.

According to Cardinal, fitness DVDs are a $250 million industry but there is no scientific evidence about their safety, thereby raising concerns and effectiveness or the accuracy of the information contained in them.

The findings urge fitness DVDs consumers to be mindful of the potential pitfalls of the product when selecting and using exercise videos.

The findings are forthcoming in the Sociology of Sport Journal.

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The findings showed that women who gave birth to more number of children, exhibited longer telomeres -- protective tips found at the end of each DNA strand and indicative of cellular ageing.

Longer telomeres are integral to cell replication and are associated with longevity.

The study assessed the number of children born to 75 women from two neighbouring indigenous rural Guatemalan communities and their telomere lengths.

The participants' telomere lengths were measured twice -- at 13 years apart -- through salivary specimens and buccal swabs.

“The findings contradict life history theory which predicts that producing a higher number of offspring accelerates the pace of biological aging,” said Pablo Nepomnaschy, health sciences professor from Simon Fraser University, in a statement.

“The slower pace of telomere shortening found in the participants who have more children, however, may be attributed to the dramatic increase in estrogen -- a hormone produced during pregnancy,” Nepomnaschy added.

Estrogen functions as a potent antioxidant that protects cells against telomere shortening.

The social environment that the study participants live in may also influence the relationship between their reproductive efforts and the pace of ageing, added the team.