Hi Jason,
I've run 3 marathons and used to be a personal trainer, so I think I can help

I'm assuming this will be the first endurance run you've ever done.
It IS possible to train for both, as long as you're okay with only really being good at one - and it sounds like your priority is rugby. And in fact, your plyo & interval runs WILL help you with running economy for the distance event.
I would do ONE long run per week, and have the other running day be mid-length. I would also add a 3rd running day for a short run. Consistency is just as important as distance. For all 3 of those runs, go SLOWER than the pace you plan to run the actual event. You're already training for speed - these days are for building endurance. If you go too fast and your heart rate is too high, you will actually hurt your endurance training.
I don't know how much time you have until the event, or how far your longest run has been up until now, so here's a general plan...
- When both cardio & strength occur on the same day, do cardio FIRST)
- Regarding runs, never do 2 hard days in a row. Hard = distance or speed. The plan below is hard-easy-hard-easy-hard-easy-off:
SATURDAY - LONG RUN
SUNDAY - Short & Easy recovery run + Strength [or make-up long run if Sat weather is bad, etc. If today ends up being your long run, skip tomorrow's intervals and do a short run instead, then continue with the rest of the week as planned. NEVER try to "make up" missed workouts.]
MONDAY - Intervals/plyo
TUESDAY - Mid-length run + Strength
WEDNESDAY - Intervals/plyo
THURSDAY - Short run + Strength
FRIDAY - OFF
For the long runs, you'll want to increase the distance by approximately 10%/week. For example:
Week 1 - 5 miles
2 - 6 miles
3 - 7 miles
4 - 8 miles
5 - 9 miles
6 - 10miles
7 - 6 miles
8 - 12 miles
9 - 10 miles
10 - 14 miles
11 - 10 miles
12 - 16 miles
13 - 10 miles
14 - 18 miles
15 - 10 miles
16 - 20 miles
17 - 10 miles
18 - 20 miles
19 - 10 miles
20 - 22 miles
21 - 10 miles
22 - 22 miles
23 - 10 miles
24 - 8 miles
25 - 6 miles
26 - 6 miles
This is the most conservative (read: injury-preventing) plan. If you have less time than that, it would look more like this:
Week 1 - 5 miles
2 - 6 miles
3 - 7 miles
4 - 8 miles
5 - 9 miles
6 - 10miles
7 - 12 miles
8 - 10 miles
9 - 14 miles
10 - 16 miles
11 - 18 miles
12 - 20 miles
13 - 10 miles
14 - 6 miles
If you have even LESS time than that, do not alter the schedule, but stop building distance sooner so you max out at 18 or 16 instead. It is safer to do one very long run on less training, than it is to train at too high a level and then run a significant distance.
In the last 2-4 weeks leading up to the event, drop back on distance, and cut out ALL strength and speed work. Preferably, the taper would be 4 weeks, but 2 weeks is the minimum. This is the time when your body not only heals from all the training, but actually continues to get stronger as it heals.
DO NOT SKIP THE TAPER PERIOD. YOU RISK INJURY IF YOU DO! Good luck, and feel free to ask me more questions as you go!
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