This is exactly how long you need to hold a plank to flatten your belly

[ahlam1399]

http://static-global-s-msn-com.akamaized.net/img-resizer/tenant/amp/entityid/AAtLXoj.img?h=100&w=100&m=6&q=60&o=f&l=f&x=2814&y=760Finally! The six-pack you?ve always dreamed of is only a plank (or two!) away.

أكثر... (http://www.msn.com/en-in/health/fitness/this-is-exactly-how-long-you-need-to-hold-a-plank-to-flatten-your-belly/ar-AAtN1wO?li=AAgg4jn&srcref=rss)