the cost of a hard start

the cost of a hard start

Post by Steve Norm » Wed, 18 Jun 2003 05:43:57

[I orginally posted this as a followup to the thread discussing pacing in
the recent World Cup 2- race.  Unfortunately the news server where I work
didn't seem to feel like sending it to the wider world, so I'm trying to
post it through Google.  Apologies if anyone has already seen this.]

Quote:

> I completely agree that after the start, the ideal race from a
> physiological point of view would be even-paced.  However, I was
> interested in whether there are physiological benefits in going off
> harder before settling into your race pace.  My original thinking was
> that a hard start might get your aerobic system up to maximal output
> more quickly.  For example I find that on a 2k ergo test my pulse climbs
> quite sharply for a minute or more before plateauing - presumably during
> this minute my oxygen uptake is below its maximum and hence reducing
> this time by going off harder might be a good idea. [...]

I have nowhere near enough knowledge of physiology to comment
scientifically on whether the hard start is a good idea, but my own
experience in races and 2k erg tests suggests that it is.  In an erg test
I feel much more comfortable at my "race pace" after a 20-30 stroke hard
start than I do if I simply aim at my target pace after 4 or 5 strokes
to "spin up the wheel".

For the erg it's possible to make a quantitative argument that the hard
start is not horribly expensive, as long as you make the (possibly dodgy)
assumption that the Concept 2 erg accurately measures energy input at the
handle.  Let's consider rowers A and B aiming at finishing 2k in 6:00.

A is an even-splitter.  Concept 2 ergs compute speed working backwards
from

      power at handle in W = 2.8 * (speed in m/s) ** 3

(I used to be able to find this formula somewhere on the C2 Website.  ** means
exponentiation here.)  So the work applied to the handle in A's 360 seconds
of fun is

    360 * 2.8 * (2000/360.0) ** 3 = 172.8 kilojoules

B, like me, prefers a hard start (but, unlike me, can actually finish a 2k
test in 6:00).  His pace is 1:20/500m for the first 250m, so he finishes
that in 40s.  Then he slows to a even pace that will let him do the last
1750m in 320s.  His work at the handle is

    40 * 2.8 * (250/40.0) ** 3 + 320 * 2.8 * (1750/320.0) ** 3
      = 173.9 kilojoules

So B puts in more work, but only 0.6% more.  That's not much, so the
hypothesized physiological benefit of the hard start wouldn't have
to be very big to make B more efficient than A.

Steve Norman