** Thanks to Sir Beanalot who has indicated that the Sprint gadget is located on mission 2-1 and can be found at the bottom left of the map. **
As you progress through the missions you'll notice that you find approximately one blueprint per mission (if you find it). Blueprints can be found either hovering over the ground like the coin collectibles or via chariot crate. If the create breaks because your chariot flipped over, no need for worry as you can simply just walk back and recollect the create.
Now, within the first 5 levels you'll find a blueprint that unlocks a gadget called "Sprint". This gadget gives you the ability to greatly enhance your speed for a few seconds after initiation. If you have this gadget selected, simply press the ( Y ) button to activate its feature. Upon activation, you'll notice a gadget indicator on the bottom left of your screen. This is the recovery timer of your gadget, meaning you must wait a few seconds before reusing the gadget.
These gold medals aren't gracious to any mistakes, every second during the speed run is important. Familiarity with the map you're attempting to speed run is key to successfully completing this achievement. Also, the sprint gadget has unlimited use during the run, so don't feel the need to save it up.
Hope this helps, happy hunting
Also I found this video guide on youtube showing you how to successfully complete the very first level WITHOUT the need of any gadget, feel free to check it out!