A barbell seems like such a simple thing: you just put the weights on it and lift it... right? The truth is, barbells are designed with lots of different purposes in mind. There are a few terms that can help you understand what bar is optimal for the type of lifting you're trying to do.
Tensile strength refers to the bar's resistance to bending to the point of breaking, generally under dynamic pressure ('yield strength' refers to a static test that determines the maximum amount of pressure it will take to permanently bend the bar). Average commercial Olympic barbells have a tensile strength of around 130,000 PSI; higher-end bars, especially those used in competitive Olympic lifting and powerlifting, often have tensile strength exceeding 200,000 PSI — but anything over 180,000 PSI is a very strong and quality bar for most users.
A little bend and flex of a barbell is a good thing; 'whip', though, is the tendency of the bar to bounce under dynamic load. The easiest example of this is to watch Olympic lifters, especially in the clean and jerk — the whip of the bar is actually used to assist in the lift.
Powerlifting bars tend to have very pronounced knurling to assist with grip. If you were doing Olympic lifts — which require the bar to rotate in the palms — they'd tear your hands up. Bars designed for Olympic lifts tend to have more moderate knurling. You may also notice that some bars have center knurling, or different grooves along the knurling. The former is to help keep the bar stable during squats, and the latter is to provide visual guides for optimal hand position in power lifts.
Bushings and Bearings
The 'sleeve', which is the outer section of the barbell where the plates are loaded, can be made with either bushings or bearings. Bushings are more rigid but allow less spin, which is less ideal for Olympic lifting but nonetheless suitable for most lifters and extends the life of the bar. Advanced Olympic lifters will want barbells made with bearings, which allow the sleeve to spin considerably more quickly and smoothly.
Styrka has you covered
One of the quality barbells we'll be featuring at Styrka is Rogue's Westside Power Bar 2.0, which is designed as a powerlifting bar especially ideal for squats and bench presses. It has 205,000 PSI of tensile strength; it's designed not to whip; it uses bushings, not bearings, because it's designed for maximum life and stability; and it uses an aggressive knurl to ensure reliable grip under heavy loads. We'll have this barbell and many others designed to accommodate a wide variety of training styles.