How much weight should be in a weighted vest for someone who weighs 119 pounds?

For burning off fat, Kate Ashford for Health.com on CNN's website says to use up to 10 percent of a person's body weight in a weighted vest while walking. Stack suggests using no more than 10 percent while sprinting and performing body weight exercises.

However, a study published in the Journal of Strength and Conditioning Research compared training while wearing a weight vest with 18.5 percent of body weight, training while pulling a sled carrying 10 percent of body weight and training without weights. After seven weeks, the no-weighted training group had greater improvement in sprinting speed than the two weighted groups.