A heavy bag isn’t a normal fixture in an aikido dojo. Some dojos have makiwaras, which are also excellent practice, but you just about have to go to a karate school to find a bag. My teaching career, such as it’s been, has mostly been in various karate schools. So, I’ve used the heavy bag, but had not really become attached to it. This is largely because I hadn’t incorporated it as part of my aikido classes. Why not? I am mostly a Saito student, and that is a pretty comprehensive system. If Saito sensei was humble enough to preserve and promulgate it, who am I to change it?
But most of my practice is individual (what!? individual aikido?? is that even possible?? briefly, yes…). The biggest problem of individual practice is variety. Another problem is resistance. So, the heavy bag addresses both problems and more. First, one of my individual practices is running through a variety of attacks, strikes and kicks. We do it with jo and bokken. Why not? It takes a few minutes to run through several repeats of each. The advantage here is that you get striking practice, and without resistance, few wear and tear injuries. I know a karate master who just quit at about 40, because the impacts were wearing down his body. But striking air has its own problem. You really don’t know how much of a hit you’re delivering. That’s where the bag comes in. Yes, if you’re striking a makiwara you get resistance, but I would argue it’s too much resistance. The heavy bag is softer. Its mass is realistic for a body and its movement gives you an idea of what you’re doing. It also allows for more combinations and kicks. My Chinese students have some fun striking drills which I hadn’t seen before.
The important thing for me, though, is to recognize and practice the “striking aspect” of aikido techniques. MANY aikido techniques open with atemi. We can’t punch out our dojo partners. The bag doesn’t mind at all, and obligingly also stands and takes the hit. Many aikido techniques incorporate atemi. Many kokyu hos are almost exclusively atemi. If you ever use ’em in an applied situation, your “partner” won’t fall out of it, so your atemi better be good. There is also a technique that I refer to as “daito ryu double punch”, which is striking simultaneously high and low by inclining your torso and punching more or less perpendicularly upward from the shoulders. It shows up in several places, notably, if in passing, in irimi nage, but also in some blends applicable to ushiro attacks. It’s worth practicing on its own, both to improve those elements and as a stand-alone technique.
It is certainly possible to overdo it. I recommend MMA gloves, especially if you haven’t ever hardened your hands. Even if you have, take it a bit easy on yourself. Who needs the injuries and arthritis?
Bottom line: I actually got this darn thing for my son, who has a mighty punch (but luckily for me is a bit slow and still telegraphs). Now I find myself using it more.