As a runner, your body can only handle so much mileage. Some runners can pile over 100 miles a week. Some runners can’t run more than 3-4 days a week.
A better more emcompassing way to put it is that you can only handle so much time on your feet. Sure, some runners are faster than others and that’s why they can rack up 100+ miles at an easy pace, whereas if most of us ran the same amount of time we’d probably max out at around 60-65.
Back to the main point: While it’d be ideal to have you log 50+ miles while training for a marathon, many can’t quite hit that number within their reasonable best efforts, or their plan doesn’t ask that much. Even if your plan does, maybe you struggle for understandable reasons to do it: Hal Higdon might ask for 20 milers and 7-10 mile midweek runs, and maybe you don’t have the time to put them in… or your body simply gives out after 15 miles. Maybe the Hansons want you to run 6-8 miles six times a week, but there’s no way you can run six times a week.
However, as Jonathan Savage says, everyone running a marathon has to run the same 26.22 mile distance. Whether your longest run was 15 miles or 18 miles or 22 miles, everyone’s got to run 26.22 on race day. It doesn’t matter if you can’t handle the distance, the pounding that volume requires, in training. You’ll have to handle it eventually just like everyone else.
This doesn’t mean you need to do 20-26 milers in training to be ready. Some runners certainly can do that, sure, and they’ll usually be ready on race day. But while I do think it’s important to develop the aerobic endurance to go no less than 2.5-3.0 hours without stopping… what you do on the other days of the week can be far more flexible.
With one key caveat.
Your body not only has to be aerobically prepared to run long, but it physically must be prepared to take the pounding of that much continuous running. No matter how much you run or how you run, you must develop the physical strength to handle the 3-6 hour pounding. And that simply will not happen on a lighter running schedule by itself.
I also don’t think speed and tempo work is anywhere close to enough by itself. You’ll develop solid ability to run a 10K or something, but that won’t fully prepare you to handle hours of pounding and aerobic demand.
The successful marathoners I know and see all tend to have one other common denominator aside from just running a lot, running regularly and eating/sleeping/recovering well.
They strength train.
It’s possible to marathon well without actual strength training. But you have to run a ton of mileage and run it well: Consistent, no injuries, solid efforts on all your miles. No junk miles.
And not only do you need to do speed and tempo work every week, but probably some hill work: Brad Hudson for example likes to emphasize hill running, and actually considers it his form of strength training (he doesn’t recommend specific strength training in his plans).
Most of us however aren’t going to put in midweek 7-10 milers, weekly 12-22 milers on the weekend, and massive sets of repeats or hour long tempo runs, the sort of demanding volume that could make strength training superfluous. We probably should strength train aside from our running.
In fact, herein lies the rub: The less mileage and time on your feet you plan to spend running during marathon training, the more important doing whole body strength training becomes.
If you can’t run everyday, or your weekday runs aren’t long, or your weekly mileage is well below 50-60 miles per week… and there’s practical reasons why training needs to be that way… then to ensure your body is physically ready for the pounding, you’ve got to build up your body’s overall strength so you don’t fall apart as you get deeper into the longest run and your stamina begins to fade.
And I don’t think simple exercises like doing a few squats and lunges or an ab routine (as most runners do) is enough in this case. You’ve got to do a whole full-body routine that actually tests your muscles. You’ve got to build muscle and anaerobically challenge yourself during these exercises. Whether you do a bodyweight routine like the Runners 360, or you hit the gym and actually push some metal, you need to seriously strength train.
First of all, it’s important to note that you should not strength train after a hard running workout like a speedwork session, a tempo run, or a long run. Those workouts are demanding enough. Strength train after an easy run, or on an off day from running.
If you strength train on easy run days, strength train after a run, not before, because the wear and tear of a strength training session compromises your ability to maintain stability in your runs.
Also, you typically will get the best results strength training 1-3 times a week, with at least one day between strength training sessions.
Though you don’t want to max out the weights and reps, you’ve got to train with the intensity of LeBron James at the gym in midseason: Like your goal with every rep is to get swole, even though you technically are doing it as maintenance and supplemental training.
If you decide to lift weights, don’t do the powerlifter stuff like deadlifts or Olympic barbell compound lifts with heavy weight. It’s not healthy or safe long term to train at a level that demanding while training in something else. You’ll either want to do more typical, smaller scale lifts like a basic bench press, curls, etc. or do bodyweight exercises. Train as if bodybuilding was the goal, a goal as important as the miles you’re running… even though obviously that’s at best a secondary concern.
As for what exactly to do, there’s no specific plan you need to follow as long as it doesn’t demand max weight or max effort. A bodyweight plan where exercises are done by time rather than demanding a number of reps (e.g. you have 60 seconds to do push ups, however many you can) is probably fine. If you just went to different strength machines at the gym and did one set of 10-15 reps at a challenging but easily do-able weight, that would be fine too. A place like Planet Fitness may be derided by passionate lifters or bodybuilders, but the scale of strength training options there is probably perfect for your scope.
(Of course, if lifting weights, you want to do one exercise for each set of muscles. A typical, healthy order of body parts to work out would be: Chest, shoulders, back muscles, legs, core/abs, triceps, biceps. You don’t need to worry if you’re doing bodyweight exercises, since these usually require most of your muscles to work.)
Then, after you’re done exercising, it becomes more important than ever to fuel as soon after training as possible. As soon as you can, drink some milk or eat some clean protein and carbs. Eat a good meal a couple hours after. Get to bed earlier rather than later and get some decent sleep to maximize recovery. In fact, you’ll want to err on the side of overeating a bit on strength training days, just as you likely would on long run days.
Your body needs to recover and rebuild, and now that you’re adding the extra stress of strength training, hitting the nutrition hard within your peak absoption window of 30 minutes following the workout becomes an important step. Recover hard so you can keep training hard.
If you were running 50+ miles a week for marathon training, and doing speed or tempo work, I’d call strength training less vital. I’d say it’s up to you how much of it you want to do.
But if you aren’t able to put in that much running volume, then serious strength training becomes as mandatory as the long run.