Relient K’s Matt Thiessen is rock music’s perennial underdog, so one tends to pull for him, almost instinctively. However, his band’s latest effort, Collapsible Lung, makes it difficult to be entirely on Thiessen’s side. Although it’s a bright, commercial, pop effort, it doesn’t include nearly as much wit and wisdom as we’ve come to expect from this usually reliable band (and its fine leader). For starters, there are areas where Relient K’s Christian fan base is surely going to nitpick a bit. (For instance, “If I Could Take You Home” sure sounds like an invitation for a one night stand and “PTL” stands for “part time lover.”) Musically, Collapsible Lung is just a little too pretty; it’s not nearly tough enough. Instead of charging guitars, Relient K’s multiple producers have filled these grooves with the sort of polite pop-rock that sometimes sneaks onto the pop charts alongside the usual floozy divas. Collapsible Lung may mark one step forward in Relient K’s quest for radio success, but it’s also two giant steps back in the credibility column. Yep – it just may knock the wind out of you.