So in my example in which I am not talking about sport the word ''heavy'' is unnecessary, isn't it? ''I never do (heavy) weight lifting.''
Well RA, that depends on whether the statement is verbal or written.
After re-reading several of the responses including mine, I think I should expand the subject or use of the subject. First, we should consider use of the term as verbal or written.
Verbal/Written
weightlifting (the sport or exercise) vs. weight lifting
an occasional, unplanned activity) Use and interpretation based on
context.
(A) I visit the gym 5 times a week.
(B) What do you do?
(A) Treadmill and
weightlifting.
&
(A) Haven't seen you in the gym lately.
(B) Yeah, I broke my wrist and I can't do any
weight lifting (or
heavy weight lifting). (Any activity involving lifting).
OR
(B) .......and I can't do any
weightlifting.(the exercise)