High volume or high activity shows there is in fact selling [supply] on the mark down.This process is known as testing. You can have successful tests on low volume and tests on high volume, usually on 'bad news'. This not only catches stops but shakes the market out as well. This process allow for higher prices. Testing is a sign of strength [as long as you have strength in the background]. Low volume or successful test tells you the market is ready to rise immediately, higher volume test usually tells you "yes I want to go up but buyers be very cautious, I may not be quite ready yet" and I may want
to re-test this price area again at a later time.