Does everyone need to warm up, or is that only for heavy lifting?

Everyone benefits, but the warm-up should match the session. Its jobs are raising tissue temperature, increasing blood flow, rehearsing the movement pattern, and letting the nervous system prepare. Five to ten minutes is enough for most people: some easy general movement, then progressively heavier or larger versions of what you are about to do. For heavy lifting, ramp-up sets serve as the warm-up. For a gentle walk, you barely need one. The people who need it most are those training early in the morning, in cold weather, or returning from injury.