Hi,
i've been following this program and am currently at week 5.
Things were going good these past few weeks, and i could see my stamina increase dramatically by following this routine. FYI I'm 24, male and weigh 74 KG.
However, now, at week 5, My legs hurt after 14-16 minutes and i start to get exhausted.
All the other weeks were good (initially hard, but manageable and unlike this week).
Is there any modification i could do to my food intake that would help ?
can somebody point me to some exercises (streching before or after) that would probably help in my situation here ?
Appreaciate you experienced folks' help 
P.S. i'm a vegetarian.