You’ve Been Re-Logged In to PPX You've Been Re-Logged In to PPX By PopSci Staff | Published Feb 9, 2008 3:41 AM Uncategorized SHARE You’ve been re-logged in to PPX. Click here to return to the PPX Homepage. Additional Links: [Your Portfolio[All Stocks popular science MORE TO READ RELATED How much exercise do I need to stay healthy? Reaping the health benefits of staying active might be simpler than you think. READ NOW RELATED Did food taste better 50 years ago? We can't go back in time, but some things have definitely changed. RELATED This protein may hold one of the secrets to predicting muscle growth There's surprisingly little research on how our bodies actually build muscle.