Saints Row IV features several different upgrades for the player's character. One very useful upgrade is "unlimited sprint". This skill allows players to sprint forever, without their sprint bar ever decreasing. It's incredibly useful for escaping the police or aliens, and it can keep you from dying in a hairy situation.
To unlock this skill, you'll need to complete certain missions. These missions are for Keith David, and they are part of the Executive Orders quest line. Read on to learn which missions lead to unlimited sprinting.
Go to the Henry Steel Mills location in Steelport. There will be 5 targets, four of which are decoys. You need to kill the real target. Try using the rooftops to get an aerial view of your target. The enemy will take a lot of damage, so use your strongest weapons.
In the Henry Steel Mills area of Steelport, you will need to kill several aliens that are located on a rooftop.
Go to the Rosen Oaks area of Steelport and complete this insurance fraud challenge.
Go to Loren Square in Steelport and shut down the Zin hotspot. You will need to turn off two generators and a controller.
In Loren Square in Steelport, find the Chrome VOID Aircraft. Steal it and bring it to the specified landing zone.
Go to the Henry Steel Mills area in Steelport and get in the Chrome VOID Aircraft. Now you can participate in the mayhem challenge. Cause as much destruction as possible.
After completing these missions, find Keith by using the portal at Brickston in Steelport. Go through and talk to Keith to be awarded the upgrade for unlimited sprinting!