In Shadowrun 4th Edition, how much a person can lift or carry is based on the character's Strength, modified by the successes from a Strength + Body roll. Human Strength and Body attributes lie on a 1-6 scale, and the manual says that average humans have scores of 3. With the average person's STR + BOD = 6, it is possible to roll up to 6 successes to modify his base lifting amount (though very unlikely to get all 6 successes). Each success rolled adds 15 kg to the amount that can be lifted. Here is a graph of the average lifting abilities (after rolling) for characters of average Body and any given Strength:
Shadowrun's mechanics have the typical trend that average characters are stronger than average real-world people, but on average the difference is not as severe as other popular systems. What is quite deviant in the mechanics is the huge variance within a single person due to rolling so many dice to determine lifting ability during each attempt to lift something.
Here is a table of probabilities of successes based on die pool:
Here is the table of base lifting amounts and modifiers: