Stuart McGill et al 2009 analyzed muscle activation during strong man exercises with an EMG. This was a rather unique study because EMG use in exercise has generally been applied to either single muscles to see which exercise is the most effective or to single exercises (eg: the squat).
Dr. McGill hooked the EMG all over the body and had different strong men perform the exercises. Outside of the strongman world, these exercises are rarely performed however their applications to real world strength are generally accepted without question. This study is another building block in that argument. Apparently it really does require strength to move huge awkward objects through space.
The lifts studied included the log lift (cleaning and pressing a loaded log overhead), the tire flip (flipping a tire that generally weighs over 500lb end over end), the keg walk (walking with a keg on a shoulder or in a bear hug for distance), the suitcase carry (carrying two heavy blocks for distance or time), Atlas stone lifting (lifting a spherical stone on to a platform), the super yoke (carrying a loaded bar across the back for distance) and the farmer’s walk (carrying to wide logs similar to a suitcase carry but away from the body).
The EMG findings were astounding and relatively uniform. Rectus abdominis was activated primarily by the tire flip and stone lifting. External and internal obliques were activated by stone lifts and tire flips. Latissimus dorsi showed greatest activation with tire flips and log presses. Upper erectors were activated by stone lifts and log presses. Lower erectors were activated by tire flips and stone lifts. Gluteus medius and maximus were activated by stone lifts and tire flips. Biceps femoris were activated by tire flips and stone lifts and lastly, rectus femoris was activated by stone lifts and tire flips.
Other interesting notes from the study include: the very large moments of hip abduction while walking with a super yoke, that the quadratus lumborum provides a strong front plane torque to support the torso during stone lifting, that Atlas stone lifting requires hip extension and back extension and that the super yoke provided the greatest mechanical load on the spine.
This data supports the integration (where possible) of some strong man lifting. We would caution that you should already have several years of strength training under your belt and qualified coaching and equipment before trying any of these movements. Given the benefits tire flips, stone lifts and log presses seem to provide, their general inclusion in a strength program would be of tremendous benefit.