[Scott Johnston]

You’ve just shown that the advertising slogan “Red Bull Gives Wings” is true.  The sugar boosted the glycolytic (carbs) contribution to the energy needed for these test.  The caffeine jacked your HR.  As test you can put on your HR chest strap and drink a Red Bull.  You will see your resting HR 5-10bpm higher if not more.  Rising from 155 to low 160s over the test (3-4%) indicates that you were very close to your aerobic threshold when you started at 155.  My recommendation would be to use that for the upper end of Z2 and retest, without the Red Bull,  in a 4-6 weeks.

I hope this helps,
Scott