Here's Laura's schedule:
Weeks 1-4: Start doing 8 mile loop in 1.5 hours. Each Sunday cut the time down until by the 4th week I'm near 1 hour.
Weeks 5-6: Add 4 miles. Now up to 12 each Sunday. Do it in 2 hours or so.
Weeks 7-8: Up it by another 4. Now at 16 miles. Have a VC (vet check) break in between the 8 mile loops. Begin checking recovery HR (heart rate) time (magic number is 60 for me) adjust pace accordingly. Faster if they come in at 60, slower if it takes them over 10 minutes to hit 60. This is prior to any cool down.
Weeks 9-11: If all if going well - I add a third 8 mile loop. So for these three weeks, I'm doing a practice LD (Limited Distance) every Sunday. I'm checking recovery times at the two trailer breaks, making sure they eat/drink well, and adjusting pace/electrolytes accordingly. Also finding out what snacks and clothes work for me as well.
Week 12-on: I back off. Do 20+ mile training ride 2-3 times each month, with a short one thrown in - or skip one. At this point, if you just do a 20+ mile ride every other week - they'll stay in shape.
My own personal adaptations of this would probably be to do less of the longer rides (24 miles) but add more difficulty (sand, hills) or a faster pace to the ~16 mile rides. I find I'm happiest conditioning around 15-20 miles. To me, that distance just feels like "enough" where the horse was stressed enough to either gain or maintain current fitness. Once you have reached Weeks 9-11, I would give the horse an easy weekend, and then they should be in shape to easily accomplish a back-of-the-pack LD ride. Then do 1-2 rides of that distance a month (either in competition, or another ~20 mile training ride). Once you've been able to stick to that for 3 months or so, you both should be ready for a slow 50. With an already legged up horse coming back from the off season - I'll pretty much follow the schedule above for weeks 1-8, maybe mix in a longer ride around 20 miles once or twice, and then go do a slow 50.
