The Minnesota Vikings have been plagued by pectoral muscle injuries since last season, the latest victim being offensive tackle Carter Bykowski. Head coach Mike Zimmer doesn't know if Bykowski will be out for the entire season, according to ESPN's Ben Goessling, nor does he know the exact root of this recurring problem.

"It's a combination of things, really," Zimmer said, per ESPN. "It's dehydrated muscles, it's getting in the position, sometimes it's over-strengthening, sometimes it's fatigue. Still, we're calling around to every expert that we can find and keep digging."

Bykowski is the fifth Vikings player to suffer a pectoral injury since last year, according to ESPN. First, guard Brandon Fusco tore his and missed 13 games during the 2014 season. Phil Loadholt, who has since torn his Achilles tendon, missed the last five games with the same injury.

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During offseason workouts, defensive end Brian Robison and cornerback Josh Robinson both sustained pectoral injuries.

Perhaps the influx of this injury has something to do with the Vikings' weightlifting program. ESPN notes that the team has emphasized free weights and power lifts over weight machines under Zimmer and strength coach Evan Marcus. However, only Robison's pectoral injury happened while working out -- the other four occurred on the field.

(h/t ESPN)