Hi Ryan, purely my opinion, but its not necessary to do anything but running if you don't want to / have time to (real world training). You'll still do ok if your blend of sessions is right and you don't overdo either the distance build up or the intensity of sessions. I just find any other activity takes up my training time I could be running in.
But if I had more time I'd consider exchanging some sessions for mountain biking / cycling undulating-hilly routes so you can get up on the pedals to do some strength training on legs without impact. I've heard this has worked well for some. Or maybe use a bike to get out in the days after a tough long run at weekend to sort the legs out without further impact damage.
I'm not sure of the real benefits of swimming to the ultra-runner. I guess its a different stress and works different muscle groups.... but I'm sure somebody else will come along and answer that.
Maybe some gym routines would also work well for some training ultra-runners too (single leg strengthening moves?). But the major concentration really needs to be on the running. Do as you would do for a marathon, you need do little more for a 50k, maybe just make your longest runs a bit longer.
First 26.2m in my road shoes for a year-and-a-half yesterday. Yorkshire marathon. Reasonably big (3000+) entry marathon starting and finishing in York. But with wide enough roads early so you can get straight into your running. In its 2nd year, but well organised and really well supported. Its tough running that far on a road at a pace that's a minute/mile under any marathon+ off-roader I've done. But unlike in the remote trail runs where you feast in the serenity and quiet of your surroundings I found the support, cheering, music, comedy banners all helped to push me along. Also happy to have run a good race, speeding up each ten miles and having a real kick in my last 6 where I was running almost like a 10k-race.
As much fun as that was though, my two remaining running challenges this year will be back off-piste
Often overlooked an worth checking out long distance walker challenges as quite a few every year all over the uk, many are runner friendly and most are over 20m with a decent number of 50's and some 100's. Always offer good foodpoints and usually cheaper than many runner specific events. I used to do many 20-30m events every year to keep my miles up in prep for bigger, tougher ultra's. But some of the challenges are tough and long to be the 'annual challenge' in themselves...
Probably not in the area many of you are looking for, but I'd say my local Woldsman 50 is a good runnable off-road ultra in East/North Yorkshire in early April. Lots of runnable tracks, path, some road, early and later miles are mildly undulating whilst middle section throws a few climbs in so nobody runs every step. Also benefits from hot meal option indoors at halfway and generally generously varied food CP. Might tick the box of somebody who is after a trail ultra where there isn't loads of walking, yet a sufficiently interesting, challenging and pretty route to entertain you for the extra hours. I'd consider it a halfway house between say a 50m road ultra and the mostly offroad and hilly Lakeland 50. And although not the stunning peaks of the lakes the Wolds are quite special and a bit unique and through their sparse population offer a serenity equal to many more mountainous areas.
The short ripped huge holes in my feet (lacing issue?) and I lost most of my time on the technical ascent and descent bits, being fine on the runnable bits. So why do I fancy having a go at the long net year
....I'd go to the extreme, but suspect I don't have the creds for it of late and experience teaches me that sometimes I go for the hardest course option available when I should hold back a bit and be patient and build up.
I didn't read that properly at first and was going to say, what about the arctic/Yukon races?" (I'd forgive anyone for not wanting to do a race with 'arctic' in its name). Not that I think the spine sounds easy - I'm yet to succumb to the charms of that one as not heard enough evidence that this would contain enough pleasure/sense of achievement to balance out the pain and suffering(thinking snow, rain storms, deep snow/mud/water).
I've never done the trail26 races, locations for sound interesting though. I probably would have done some, but for fact hardmoors trail marathon series appeared about the same time and is a bit closer to me.
I'm yet to settle on a single event for next year. I'm waiting for the right challenging event to "find me". Not even sure what my November, December events are going to be this year Maybe Hardmoors 26.2 events from Goathland (27m), Roseberry topping (28.5m). Maybe new Frostbite 30 route (nidderdale) but not on event day and also considering the Tour de Helvellyn (after wanting to do for a few years).