Being able to put the power down on the timed sections, combined with technical skill, will mean the difference between being first and being at the back.

Sprint drills are great for this. Pick a section of track that isn’t too technical, such as flat single track or a fireroad climb, and go flat out as hard as you can for 30 seconds. Then rest for one minute, and repeat a further two to four times. This can be a little awkward on some MTB rides, so you might want to do this on your road bike too. 

There are also various dynamic routines and exercises you can do in gym that will help, like the dreaded burpees, and kettlebell workouts.