Before anyone gets any ideas from the blog post title, I am not AT ALL hating on the kettlebell swings. I have probably done over 125,000 of them, and still do about 600 per week. I just wanted to make a distinction between the kettlebell swing and other exercises.
If you look at the kettlebell military press or front squat, there is a definite minimum starting and ending point. Whether you are lifting 16kg or 64kg, these points are the same. The same cannot be said for the swing. In the swing, the completion of the swing is simply to extend the hips and knees. The bell goes as high as it goes, you don't lift it. I may go up to shoulder level, it may only go to waist level, who cares! The swing is a back-to-front 'projection' of force. The bell goes up, not because we are "lifting" it, but because it is connected to our torsos through our arms. For this reason, treat the swing as a MOVEMENT, and not a LIFT.
What are we training in the swing. Primarily, we are training the hips and glutes, and to a lesser extent the quads. Other muscle are activated to stabilize in the lift, like the abs, obliques, rhomboids, lats, and rotator cuff. If we are primarily training the legs, why would anyone care how high the arms lift the bell? Why would anyone make that the criteria for the swing?
So, you might ask, what is the purpose of the kettlebell in the kettlebell swings. Simply, it gives us an object to exert force against, kind of like the purpose of the floor in a pushup. Pushing against air is not going to generate any tension.
In a military press, if you press a 32kg vs. a 24kg, are you using 33% more force/tension? I would argue that you are indeed. Can the same thing be said about the swing? No. Because the kettlebell swing does not have a fixed end point. If I swing one 24kg bell, the bell will go up to about shoulder height. If I swing two of them, they simply don't go as high. I am exerted similar forces, but with heavier swings the object that I am exerting the force has twice as much mass, so it won't be accelerated as much. I am most certainly not doubling power production or calories burned.
On day I was working with a petite female, and had her swing a 16kg (35lb) bell instead of the 24kg (53lb) bell she said she normally used. She actually said that the 16kg was harder. Here is why that would be:
* In a heavier swing, she is limited by grip strength. Grip strength is not a bad thing to train, but there are a lot of other ways to train it. She may even hold back on the swings (i.e., less force) to take pressure off of the grip.
* She is also limited by her ability to counterbalance or "anchor" the bell. It is a significant percentage of her body weight. The harder she swings the bell, the harder this become. This means is that she may subconsciously mute swings to keep her balance. Not what we are looking for, unless you are training for ego, pounds lifted, or impressing your Facebook friends.
* In this lighter swing, she is limited by her cardiovascular system and her glutes and hamstrings, and not the relative size of the bell or her grip stength. The lighter swings, at least in this case, give me more of the training effect I'm after since now she can really go ALL OUT.
I have done swings with a Beast in one hand and a Bulldog in the other. This is well over my body weight. My normal swing weight is 32kg (sorry, this bell doesn't have a cool name). Am I swinging with 2.75 times the force? Well, if I am truly doing Hardstyle swings, the answer is an obvious no, as I use full effort on all my swings. In my workshops, I demonstrate swings with and 8kg, 24kg, and a 48kg in succession and point out that the MOVEMENT should look the same and done with full intent. This is also the reason that swing MOVEMENT, no matter how heavy, all take about the same time, about 1.5s/swing. If you doubled the weight of a squat, the LIFT will definitely take longer. Pavel has registers forces over 500lbs swinging a 24kg bell. Would they be over a half ton if he swung a Beast? No.
In summary, the purpose of the kettlebell in the swing is to give you something to exert force against. Because it is an open movement and not a lift, added weight DOES NOT proportionately increase force generated, and in fact, may even decrease the force output. Are heavy swings bad? Not at all. In fact, they can be very helpful in dialing in the movement. Just keep in mind that the kettlebell swing is a movement and not a lift. Keep in mind that added weight in the swing doesn't mean the same as if you add weight to your military presses, squats, snatches, cleans and jerks -- these are lifts.