Answer based on context:

Hoping to rebound from their loss against the Steelers, the Titans went home for their Week 2 home opener against their AFC South foe, the Houston Texans.  Tennessee would strike first in the opening quarter as running back Chris Johnson got a 57-yard touchdown run.  The Texans would answer with quarterback Matt Schaub completing a 19-yard touchdown pass to wide receiver Andre Johnson, yet the Titans would reply with quarterback Kerry Collins completing a 69-yard touchdown pass to Johnson.  Tennessee would add onto their lead in the second quarter as Collins completed an 8-yard touchdown pass to wide receiver Nate Washington.  However, Houston took the lead as Schaub completed a 72-yard touchdown pass to Johnson and a 29-yard touchdown pass to Jacoby Jones, followed by a 38-yard field goal from kicker Kris Brown.  The Titans would close out the half as kicker Rob Bironas made a 40-yard field goal. In the third quarter, Tennessee would regain the lead as Johnson got a 91-yard touchdown run.  The Texans would tie the game again as Schaub completed a 1-yard touchdown pass to tight end Owen Daniels.  In the fourth quarter, Houston took the lead as Brown nailed a 23-yard field goal.  Afterwards, the Texans' defense prevented any attempt at an offensive rally.

How many touchdown runs over 50 yards did Chris Johnson have?
2