What Is an Erg?

Spend five minutes in a rowing conversation and somebody will say “erg.” They will not say rowing machine. Understanding why tells you something useful about which machine they mean.

The word

“Erg” is short for ergometer — from the Greek ergon, work, and metron, measure. An ergometer is any device that measures work done. Cycling has them, and so does exercise physiology generally.

The distinction matters. A rowing machine is a machine you row on. An ergometer is a machine that measures the work you do while rowing on it. Every erg is a rowing machine; not every rowing machine is much of an ergometer.

A budget machine that reports “count” and an estimated calorie figure is not measuring work in any meaningful sense. A Concept2 PM5 is: it calculates power output in watts from flywheel deceleration and derives everything else from that.

What an erg actually measures

Power, in watts. Everything else on the display is derived from it.

On an air rower, the monitor watches how fast the flywheel slows down between strokes. That deceleration rate is a direct function of how much air the fan is moving, which is a direct function of how much work you did. From the resulting wattage the monitor computes:

• Split (time per 500m)— the sport’s standard unit of pace. “A 2:00 split” means holding a pace that would cover 500m in two minutes.
• Distance — a calculation from power over time, not a measurement of anything physically traveling.
• Stroke rate — strokes per minute, counted directly.
• Calories — an estimate derived from watts. Treat with the usual suspicion.

Why splits are the number that matters

Because they are comparable. A 1:45 split on a Concept2 in Boston means the same thing as a 1:45 split on a Concept2 in Manchester. That is the entire reason Concept2 dominates competitive indoor rowing, and it is not really about the machine being better built — it is about everyone agreeing on the same measurement.

Budget monitors report distance and calories using their own arithmetic, which is fine for tracking your own progress and useless for comparing against anyone else. If that matters to you, it narrows the field considerably.

“Erg test” and “2k”

An erg test is a maximal effort over a set distance, used to measure fitness or select crews.

A 2k is the standard one: 2,000 meters, all out, taking most people somewhere between six and nine minutes. It is genuinely unpleasant, which is why rowers talk about it the way they do.

If you hear someone give a time without a unit — “I went 6:52” — they mean a 2k.

Does the word tell you which machine?

Usually, yes. Someone who says “erg” almost always means a Concept2, or at minimum an air rower with a proper power-measuring monitor. Someone who says “rowing machine” might mean anything.

That is not snobbery so much as vocabulary following function. The word comes from measurement, and it stuck to the machines that measure.

Do you need one?

Only if you care about comparable numbers. If you want low-impact full-body cardio in a small room, a magnetic machine with a basic monitor does that job perfectly well and does it more quietly and more cheaply.

If you want to do a 2k and know what your time means, you need an erg — and in practice that means a Concept2.