First, they only refer to the volume for the whole market. But you need to remember, the information does not represents the whole market due to speculative play such as KNM that inflates the volume. Sometimes you can see that penny shares that are hotly traded that command the top-10 trading spots.
For me, observation of volume is better done for individual stocks and not on the general market. What you consider a healthy uptrend is when:
- Higher volume when moving up
- Lower (decreasing) volume when moving down
The last point is, we don't want too high volume. A big spike in volume, especially when the stock is already on a long uptrend, usually indicates the end of the trend. Very high volume indicates that ah-pek, ah-mah and everyone is in. That is when you want to stay out (or get out).
Best time to get in is during low volume (of course after your trading setup issue a buy). If you can do that, then consider yourself not one of them (ah-pek & ah-mah) anymore.