Muscles have a certain motion-speed “sweet spot” at which they produce power most efficiently.
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BY VOLKER NOLTE
PHOTO BY PETER SPURRIER
In a previous column, we discussed the stroke rates in international racing and stated that stroke rate is connected to rowing speed. Obviously, you row at a higher stroke rate in a race than in long-distance training. While you can row at your long-distance rowing speed with different stroke rates, you have less variability at your disposal if you want to maintain a high pace in a race.
If you row on an ergometer at a pace of two minutes per 500 meters, the monitor will show power output of about 200 watts. For a 185-pound single sculler, the same power output in a single generates a split of about 2:10/500m. Well-trained rowers can produce these kinds of speeds on the ergometer and in the boat with a stroke rate between 15 to 30 spm, but if you measure an athlete’s energy expenditure via heart-rate or oxygen consumption, you’ll find that it varies for different stroke rates. In fact, there’s an interesting relationship between stroke rate and total energy consumption at a fixed power output.
Rowers have to produce the energy to move their body parts and support the functions of their organs, such as the heart and lungs, while also generating the power to propel the oar. Muscles have a certain motion-speed “sweet spot” at which they produce power most efficiently. In 1938, the eminent physiologist Archibald Hill found that the maximal force of muscles varies with speed of motion. At slow motion, muscles can generate maximal force. If we move fast, muscle force declines. A muscle produces its maximal power output at a speed midway between slow speed/high force and high speed/low force, since power is the product of force and velocity–an axiom proven in tests in the physiology lab.
In a typical test, an athlete on a bicycle ergometer is asked to produce a fixed power output at different pedaling rates while total energy consumption is measured. Plotting energy consumption over pedaling rate produces a parabolic curve whose low point indicates the most efficient cadence. Performing the same test on a rowing ergometer yields results such as those in the chart, for power outputs of 200, 250, and 300 watts.
For each power output, there’s a stroke rate at which total energy consumption is minimal, which means an athlete needs the least fuel. For a given power output, this is the most efficient stroke rate. Translated to rowing on the water, this means there’s a most efficient stroke rate for a certain rowing speed, and it goes up with the required power output and rowing speed.
The relationship between energy consumption and moving speed is not the same for every rower, and it’s affected by other factors–body weight, fatigue, technique, conditioning, etc., as well as rigging, water, and temperature. The shape of the curve can be influenced also by training, since properly conditioned muscles get stronger and more efficient.
In some situations, rowing at the most efficient stroke rate doesn’t matter. For example, when training to improve strength or technique, it’s appropriate to row at a lower stroke rate. If, however, you’re trying to train at a specific power output, reach the best rowing speed, or race, it’s advisable to aim for the most efficient stroke rate, which means figuring out which stroke rate works best at a given power output. This is more important for a crew boat with athletes of different training levels. Since not every rower has the same most-efficient movement speed, the crew has to exercise at the intended race intensity and then adjust for individual efficiencies.
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