Only on letsrun...
Here are some wild observations:
The HR graph is crytically titled
"16 alternating 400m (in 52-54 seconds) and 200m (in 24-25 seconds) reps with 1.5-2min recovery jogs at 2341m"
and the curve matches exactly what we would expect...
I'll go out on a limb here and say the graph is from the workout in question.
As for intensity, heart rate rarely tops 160 for most of the workout and this is at the absolute peak of the curve for a very short period, so assuming max HR is indeed 178 we are rarely at even 90% MHR...
Heart rate drops like a stone between reps, getting back down to as low as 90 early, and eventually going out to 110 at end of recovery period towards the late reps, so based on the 178 MHR and 32 RHR we are dropping to:
40% heart rate reserve or 51 % Max in one early rep
53% heart rate reserve or 62% Max in late reps
is this hard? You tell me...
It's amazing that a coach/scientist went into the kind of micro analysis he did in that article about a workout which never even happened and I hope no-one is asking "How do we get there?" for their pros who depend on solid advice not on multiplying Bekele's workouts by 2 and speculating...