Technique, rate, and power; was Re: rowers shadow


Neil Wallace wrote:
paul_v_smith@xxxxxxxxxxx wrote:
I didn't recall a rate that high and just relooked at it, R43 tops
according to my stroke watch.

I am happy to accept your figure.
Doesn't change the point I was trying to make though.

not one bit.

I'd be interested to know if anyone has done any actual boat velocity
analyses in the last ~500m of major races like these... where rowers
inevitably take the rate up, and many people retrospectively claim it
was for naught, simply because other boats then moved on them.

I think most of us would agree that the recovery takes less muscular
effort/energy than the drive portion of a stroke.

As rowers fatigue in the final portion of a race, they must somehow
either maintain or increase boat speed. If you're fatiguing, it's very
difficult to do this by "pulling harder". You could however,
supplement your weaker pull (due to fatigue) with a quicker recovery
(which is still plausible) and maintain, or come close to maintaining
overall speed.

Boats like the 2004 USA 8+ who, like Paul pointed out, took their rate
up in the final portion of the race, AND almost lost the race to
charging/advancing competitors, IMO probably WOULD have lost the race
had they NOT taken the rate up. Since their power (force and/or
velocity) on the drive was diminishing, the only way to maintain boat
speed then would be to take more strokes in the same amount of time
(assuming they weren't slowing themselves down with poorer technique at
the higher rate, which is not always a good assumption, but also not
the point I'm trying to make).

I mentioned to Carl in a recent discussion, that human muscle must
follow a certain force-velocity relationship for contraction. The more
force a muscle produces, the slower its maximum contraction velocity.
The faster the contraction, the smaller the force that can be produced.
This inverse relationship may be intuitive to some, but if not, you
can show this to yourself fairly easily with a biceps curl: With no
weight in your hand, you can do a curl (bring your hand to your
shoulder) very quickly. Put some weight in your hand, and you may
still do it quickly, but not quite as fast as with no weight. Keep
adding weight, and the speed with which you can do one curl continues
to diminish, until you get to the max weight you can support, but you
can not move, which is your max isometric (zero velocity of
contraction) weight. Any more weight, and you would be forced to
slowly extend your elbow, unable to resist gravity's pull (this is
called an "eccentric" or "lengthening" contraction of the muscle.)

So, at every velocity of muscle contraction (how fast you can perform
the arm curl) there is a max force you can apply at that speed, and for
every force/resistance there is a max velocity you can apply. These
two relationships (really one relationship) define a max force-velocity
curve for muscular contraction. A depiction of this curve can be seen
here:

http://www.sportsci.com/SPORTSCI/JANUARY/F-V%20CURVE.htm

So, there is somewhere on this max force-velocity curve, where the
product of force and velocity (muscular power = f * v) is maximized.
(This curve can be seen on the same page linked to above, slightly
further down that page). Studies have shown that this maximum power
point varies slightly from person to person, and across muscle types,
and is between 30% and 40% of maximum contraction velocity, or around
half of the muscle's maximum isometric force.

In the final minute of a 2000m race, we can safely assume that
motivated, elite athletes will be exerting maximum effort, therefore
they will be somewhere "on the curve" of the force-velocity
relationship (i.e. not below the curve which would be less than max
effort, and it is impossible to be above the curve). If they've
trained well, the part of the curve they are on will be somewhere near
their peak power capability.

To maintain rowing speed, power must be maintained. If we assume that
the rowers are already at their max power output, then muscular power
can not be increased. The only way then to increase boat speed is to
take the rate up. And, if muscular power is falling due to fatigue,
the only way to maintain boat speed is to take the rate up.

We all know that boat speed fluctuates during the rowing cycle. But on
a gross scale, the speed of the boat is difficult to change. So, at
any point in the drive, the speed with which the rowers' muscles
contract is determined by the speed of the boat at that instant. This
is unlike a bicyclist, who can significantly change the speed of
muscular contraction for a given bicycle velocity quite easily, simply
by changing gears. A rower can, within some small range, row "longer"
or "shorter" voluntarily at a given rate. However, an increase in
stroke length comes with an increase in time (of the drive) and thus
the velocity of muscle contraction remains roughly constant.

So, a rower is really bound to a very small range of adjustment on the
physiological force-velocity curve for their muscles, assuming they are
rowing with maximal effort at a given boat speed. (At 800m into a
race, you might have something extra for a power 10, at 1800m into a
close race, you very likely do not, i.e. you are at max output). So,
as you fatigue, the ONLY way you can maintain your boat speed is to
increase the rate. In fact, even if you are not fatiguing, and can
maintain optimum force & velocity of muscle contractions, the only way
to increase boat speed is to take the rate up.

So, as I see it, the question then is, how to take the rate up without
ruining technique such that you go slower anyway. If what I've said
above is correct, then at max output, the only way to take the rate up
is via a faster recovery.

Thoughts?

-Kieran
"up two on this one..."
:^)

.

Relevant Pages

  • Re: Technique, rate, and power; was Re: rowers shadow
    ... Since their power (force and/or ... the slower its maximum contraction velocity. ... A depiction of this curve can be seen ...
    (rec.sport.rowing)
  • Re: Technique, rate, and power; was Re: rowers shadow
    ... velocity) on the drive was diminishing, the only way to maintain boat ... I mentioned to Carl in a recent discussion, that human muscle must ... follow a certain force-velocity relationship for contraction. ... force-velocity curve for muscular contraction. ...
    (rec.sport.rowing)
  • Re: Technique, rate, and power; was Re: rowers shadow
    ... velocity analyses in the last ~500m of major races like these... ... I mentioned to Carl in a recent discussion, that human muscle must ... follow a certain force-velocity relationship for contraction. ... force-velocity curve for muscular contraction. ...
    (rec.sport.rowing)
  • Re: Technique, rate, and power; was Re: rowers shadow
    ... I'd be interested to know if anyone has done any actual boat velocity ... follow a certain force-velocity relationship for contraction. ... force-velocity curve for muscular contraction. ...
    (rec.sport.rowing)
  • Re: Technique, rate, and power; was Re: rowers shadow
    ... I'd be interested to know if anyone has done any actual boat velocity ... follow a certain force-velocity relationship for contraction. ... force-velocity curve for muscular contraction. ...
    (rec.sport.rowing)