The fact is there IS some truth to what he's saying, but to find that truth you have to change what he actually said, so ultimately I'd have to say that I disagree with his statement as it stands.
However, it's probably important to first discuss the inferences of the statement which I DO agree with.
First off, it's probably true to say that it's not possible to get AS big and AS strong using exclusively
kettlebells as it is using exclusively barbells.
There's a number of reasons why this is the case. The most obvious one is that barbells have an unlimited (at least as that term pertains to the limits needed to train humans) loading potential for ALL exercises/movement patterns/muscle groups that it's possible to use them for.
Whereas, even if you could find them, the morphic shape of giant KB's become innately untenable for most exercises beyond a certain load. In other words there comes a point, on most if not all KB exercises, where continuing to use bigger and bigger KB's becomes increasingly unwieldy and potentially injurious.
The barbell doesn't have this problem, and that's an enormous advantage when attempting to maximize the ultimate size and strength potential of your muscles.
Barbells are also more adjustable, as the standard load-jumps are smaller. Which increases your ability to be more incremental with them and thus it’s just easier to program and progress with Barbells.
This is also a huge deal.
It should be noted that you CAN negate this disadvantage somewhat by either purchasing small magnetic weight plates to stick to your KB's, or by duct taping small plates to them.
But, the higher loading potential of the classic big barbell exercises also mean that every load increment automatically represents a lower percentage of 1RM and thus is more incremental relative to the barbell exercises themselves.
So what's the deal, am I contradicting myself here?
No, because the statement that was made was not "barbells are better than KB's for maximizing your strength and hypertrophy potential".
It was, and I'm paraphrasing, "You categorically CAN'T get really strong using KB's"
This is where we disagree. Well, I suppose it all depends on how you define the word 'Really' within this context.
Are you going to win Mr. Olympia using only KB's? Probably not.
Are you going to out Deadlift Eddie Hall using only KB's? Probably not.
Can you become, for all intents and purposes, what most people, including world class athletes and coaches, would consider REALLY strong using only KB's?
I would argue yes, and it's more than possible, in fact with optimally programming, it's probable.
No, the realistic loading potential of KB exercises aren't unlimited like the Barbell's are...but do they need to be in order to provide the opportunity/potential to make you 'Really' Strong?
I would say no.
Yes, KB exercises have loading limitations, but let's look at what those loading limitations are relative to the exercises available to use at those loading limits, to see what kind of physique/abilities they may be capable of producing.
So let's conservatively say that most grown men of medium limb length, could safely handle 2x48kg (2x106lbs) on most KB exercises (understand I not talking about typical strength performance levels, I mean if they were strong enough to use this load, the size of the ball of KB relative to the skeletal length of their arms, would mean that it would be safe to do so).
For tall men, with large, thick frames and long arms, if strong enough to do so, they'd probably be structurally safe to up that limit to 2x60kg (2x132lbs).
Now, picture for me if you will, what kind of physique and performance capacity would exist on an individual who was capable of the following workouts:
1: KB Double Half Snatch: 2x48kg/2x60kg 5x10
2: KB Racked Pistols: 2x48kg/2x60kg 5x10/10
3: KB Double Strict Press: 2x48kg/2x60kg 5x10
4: KB Bench Chest Flyes: 2x48kg/2x60kg 5x10
5: KB Kroc Rows: (one exercise where the size of the ball of the KB is largely irrelevant from a safety perspective, so monster KB's, which can be found over 200lbs, can be safely used by all strong enough to do so): 1x90-100kg 5x20-30!
There exist a ton of other KB exercises which could be used to produce very robust growth/strength stimulus when programmed optimally, but I think you get the point.
You may say:
"But, there's no one in the world right now who's EVER been capable of those numbers on any, never mind all, of those exercises"?
Correct, which is precisely the point. The Strength and physique building potential possible with just KB exercises, is actually insane!
Furthermore, although these figures may represent the 'safe to use' upper end loading limits for those KB Exercises, thanks to the unique shape of the implements and the techniques available to use with them...there is NO upper volume limit with these load limits!
In fact, this is one area where the KB has a HUGE hypertrophy and strength actualizing advantage over barbells! Training which stimulates hypertrophy has been proven to have a very wide rep range.
And, all other things being equal, if you have a guy who can press Double Beasts for 10 reps, who subsequently becomes capable of pressing them for 20 reps (or anything higher than 10) they WILL have bigger delts and triceps! Guess what, they'll also have a higher 1RM (and every RM) to boot.
Because, as I've said many times in the past. It's a mathematical impossibility to significantly improve performance in any rep range without simultaneously improving performance in EVERY rep range.
So in conclusion, is it possible to subjectively, and by anyone's definition, objectively become 'Really Strong' using exclusively
KB's?
Yes.
Stay Strong.