Originally Posted by rushbikes

I'm gonna have to disagree. Short answer: yes.

Remove from the equation the distracting variables - heartrate and cadence - and just focus on the variables at play. The primary forces that work against you are gravity (in the event you're riding at an incline; assuming you're flat, this is zero), various forms of friction within components and rolling resistance (these are usually taken as pretty nominal, especially if you're comparing the difference in forces between these at 20 and 60 kmh), and relative wind resistance, relative being the key word.

If you're pedaling at 20kmh into a 40kmh headwind, relatively speaking, this exerts the same force as a 60kmh wind if you were stationary. The flaw is that, as I said, you would be stationary. Considering wind resistance is the primary force operating against a cyclist, especially at relative speeds of 60kmh (since force from wind resistance increases exponentially with speed), I'm inclined to say yes, they are effectively the same thing.