"With enough rubberbands anyone can do gymnastics." Our often-repeated claim that CrossFit is "designed for universal scalability making it the perfect application for any committed individual regardless of experience" finds its greatest challenge with bodyweight exercises - the stuff we call "gymnastics." By contrast, weight training and weightlifting exercises scale readily, if not obviously, by simply reducing loads.
With training bars and training plates we've been able to introduce the major lifts like squats, deadlifts, presses and jerks, cleans, and the snatch to all comers, including seniors, regardless of ability. This approach is not novel; many of the most successful and sophisticated weightlifting programs start everyone out with PVC pipe or wooden dowel systems of negligible weight and only increase loads in tiny increments when execution is good.
But bodyweight exercises create a special dilemma. Most women, seniors, and larger men are typically challenged to complete a single rep of even the most rudimentary bodyweight movements. This is most true of basic upper body exercises like the pull-up, push-up, or dip.
For years assisted pull-up and dip machines like the Stairmaster Gravitron have been our staple for introducing, training, and developing bodyweight exercises.