Hi Rogelio, Sorry for the late reply. The grip sheets actually ware off after a while but works longer and gives more holding on grip. Here's a link for where I bought mine.Â
https://www.motosport.com/search?textsearch=factory%20effex%20grip%20tape%20sheet&tracksearch=1
Replied on Ask questions about off the MX Bike Training.
Dec 21 at 04:50 PM
Hi Dave, I’m not a big fan of rowing machines. They’re good to use a little bit, but they only work the pulling muscles and none of the pushing muscles, a little bit for your legs, but not much at all. Some riders, including McGrath would not use them because they caused arm pump for them. But I do have some videos about using  bike trainers. And a lot of cardio and strength vids for motocross, of course. You can find them all in this supplement training category.
https://www.semicsmotocrossvideos.com/categories/motocross-supplement-training-videos