I'm about to start training for a 15km trail run and am wondering if the crossfit endurance program is effective. Is it worth getting a gym membership so I can do the heavy squats and deadlifts involved?
As a long-distance runner who does CrossFit, I have looked into this a good bit and experimented with myself over the last two years.
While CF doctrine says (at least at two gyms in DC) that endurance is a degraded mode of power, I have come to the conclusion that practice makes perfect. If you want to do your best at the marathon, you need to do a lot of long runs. If you want to crank out 100 pullups unbroken, you need to do a lot of high rep pullups. This is pretty basic, and it makes sense to me. There are no shortcuts.
I don't know the science behind how our muscles work, but I believe that we perform better after repeated experience. After two years of CrossFit, I am a much more fit person, able to do much more with my body than run long distances, but my long distance running times have suffered.
Simply put, CrossFit makes you better at doing CrossFit, which is a a pretty darn good proxy for functional capability in life. However, if you want to win the 15K, go to runners world and find a good training program.
I do CrossFit and several guys in my box are crazy endurance athletes. A few of them recently did ultra marathons. Other than a lot of running, they follow the HQ WOD. CF is just a conditioning program. If you follow it, it'll help you train for your 15km. But we're generalist, so you probably won't be the fastest even if you complete it comfortably.
If you want to complete it and do your best, you should find out what people with fast 15km times do.
That sounds exciting. If I were training I would be running different small trails extending into length and difficulty. Re-producing the environment you will be running in can prepare your mindset and all the muscles required to complete your goal. On your small trail you could make it interesting by adding in little circuits like 15 press ups here, jumping jacks there, the fun you could have.....
Joining a gym can encourage routine. Classes like circuits or spinning, and equipment like the treadmill or cross trainer will help but outside real environment wins hands down. Another side to this is the possibility of meeting other people who have the same goals that could lead to team training.
Good luck and have fun :)