What is Range extension?

The Market Profile reasoning goes like this. Day-timeframe traders tend to rotate within the IB. For price to leave the IB with conviction, larger or longer-horizon participants (the OTF) usually have to get involved. So range extension can be seen as a possible footprint of the OTF. That is why the CBOT's Market Profile study material and Dalton's books note that the absence of range extension usually means short-term traders are in control.