How rowing machines work

Rowing machines are a staple of the gym,
but how do they work and what does that
lever on the side actually do? The entire
system of indoor rowing works on the principle of
resistance. When you pull the chain back it spins a
flywheel inside the housing. As you return to the
starting position the chain winds back round, ready
for another tug on the flywheel.
The lever on the side is called the damper and this
affects how much air is allowed into the system.
When the setting is higher, more air is able to get in,
making the flywheel harder to rotate as it’s battling
against more air resistance. Even when you’re on
the return stroke, the air is still working against
you, slowing the flywheel down so it takes more
effort to pull it back again.