When I started TFC a few years ago, I knew I'd have to figure out how to hangboard with one hand. Every time I tried, though, I'd just spin until I popped off. Finally I hung my left arm in a sling to keep from spinning, but that REALLY hurt my left arm and I was so wildly out of balance that after a few sessions I was getting wild neck pain and weird shoulder spasms. Suckage: achieved.
Someone who knows way more about TFC than I do suggested I check out a new device called the Grippul. It simulates the same motion of stretching and working the tendons by 'suspending' weight from the fingertips, except instead of being pulled down by gravity, you're pulling up a weight. Simple, right?!
It's hard to say what effect grippuling has had on my performance, I started using it around the same time that I increased other TFC activities. It is easier to measure progress with this than a hangboard (you just add weight), and I've definitely been able to increase both weight and the difficulty of the holds over the last several months. I am happy with how I've been climbing fingery routes and problems, so this is an easy and simple exercise I can do while watching TV and eating cupcakes.
Negatives? Your toes are at risk of being crushed. Watch out. If you have butter fingers, you can also attach it to most cable machines. Much like a hang board, it's very possible to over do it and injure yourself, so take it easy and talk to someone smarter than you before starting a training routine like this.
I was thinking about saving this review for Vol. 3, but this belay device has so radically changed my life, it couldn't wait. I'll skip the usual review, as with all devices it's been reviewed within an inch of it's life - so for a technical review, check out this great one from Splitter Choss.
What I really want to focus on is why this is the most incredible belay device that I've ever used because of how fluid and efficient it is to belay a leader with my stump. I can't use a gri gri, there's simply no way for me to correctly and safely control the camming mechanism, and the drag on the rope through the device is too great for me to pull out with the nook of my elbow. Instead, I use an ATC so I can have a somewhat free hand that's not busy disengaging a cam. Still, while I'm convinced the method is safe, it is not at all comfortable and it really sucks for my partner to get short roped with every clip - I'm only able to pay out slack in increments of a foot or so, and the rope often falls out of my elbow crook which leaves me scrambling. For years, I've top rope belayed with a gri gri and lead belayed with an ATC.