Heavy Lifting Meaning

(idiomatic) The most demanding part of an endeavour; work requiring the most effort, resources, or consideration.

Example: 2000 June 5, Cache as cache can (continued under the title WorkFire), InfoWorld, Volume 22, Issue 23, page 60F:
  That's what I call the heavy-lifting part of the problem, and that's really where the term genetic caching comes into play.
2003 March 18, John Howard, speech to the Australian Parliament:
  Alliances are two-way processes and, where we are in agreement, we should not leave it to the United States to do all of the heavy lifting just because they are the world’s superpower.
2010, The 9 Month Investment: A Passive Investors Guide to Achieving 10 Years Worth of Wealth Accumulation in Only 9 Months, page 23:
  We want our experts to spend their time on this and do the heavy lifting for us.