Also of note are the Kaebade (i.e. Iron Bows) at their feet. That unique training tool is swung from one shoulder to the other, building upper-body strength.
It should be noted though that Reg et al, performed bodybuilding movements with kettlebells, (usually shoulder and arm work) and did not train with them in the kettlebell methods that are widely promoted today.
Charles Phelan was a protege of Warren Lincoln Travis and eventually taught much of what he knew to Vic Boff.
Phelan told jokes between feats of strength, also billing himself (quite uniquely, I might add) as “The World’s Most Entertaining Strongman.” Phelan only weighed 140 lbs, but could backlift 2500 lbs.
Pullum used to perform this “double-bodyweight” feat twelve times per week but in all his years, his “challenge” was never accepted.