Running 100km a Week: What It Really Takes and Should You Do It?

Running 100km in a week had been sitting there in the back of my mind for a while. Not necessarily as a target, more as one of those numbers you start noticing as the training gets bigger. During my build towards the 2026 Berlin Marathon, my weekly mileage had moved from the 50-70km I would normally run into the 80s and 90s. Eventually, a three-figure week started looking less ridiculous.

Week 15 of my 21-week Berlin block was the one. By Sunday afternoon I had covered 100.5km, spent 9 hours and 32 minutes running and climbed 649m across six days. Seeing 100.5km on Strava was satisfying, but the interesting part wasn't really reaching the number. It was everything required to get to a point where running that much could sit inside a normal training week without completely wrecking the rest of the block.

I've been running consistently for more than 10 years, with a 3:11 marathon PB and 1:26 half marathon PB. I hadn't suddenly decided to double my mileage for a challenge. Several weeks around 85-95km had already gone into the legs, with lower-volume recovery weeks mixed in. The 100km week started on Monday, but the build towards it had started months earlier.

Is 100km a Week Actually a Lot?

Running social media can distort your idea of what normal marathon training looks like. Open Strava during peak marathon season and 80km, 100km and 120km weeks can start looking fairly standard. They aren't.

A 2025 study looking at 151,813 marathon performances found an average training volume of 45.1km per week across the 16 weeks before race day. Another analysis of 92 publicly available marathon plans found that lower-volume plans averaged 42.9km per week, medium-volume plans 58.5km and higher-volume plans 107.7km.

So yes, 100km is a big week for a recreational marathon runner, but it isn't some mythical amount of running reserved for elites either. Higher-volume marathon programmes can take runners beyond 100km. Whether that makes any sense for you depends far more on your own training history than the number itself. For me, it was simply where this particular Berlin build had taken me.

My 100.5km Training Week

There wasn't anything particularly clever about how I got to the total. I didn't run seven days straight or start adding pointless kilometres around the block on Sunday evening. It still had to look like a proper marathon training week.

Day	Session	Distance
Monday	Easy run	11.3km
Tuesday	Progression run	14.15km
Wednesday	Easy trail run	16.6km
Thursday	Rest day	0km
Friday	Broken Miles speed session	12.31km
Saturday	Easy running split across two runs	9.78km
Sunday	Long run with marathon pace efforts	36.26km
Total		100.5km

That meant six running days, one complete day off and enough variety through the week that it still felt like marathon training rather than chasing mileage for the sake of it. The rest day ended up being more important than I expected.

The Week Didn't Start Particularly Well

Tuesday was a 14.15km progression run, averaging 4:55/km overall and getting quicker as it went. On paper, perfectly fine. My actual note afterwards was: "Legs felt battered the entire time."

That was probably the first reminder that a high-mileage week doesn't exist in isolation. I wasn't starting Monday with completely fresh legs after doing nothing for seven days. The previous week's training was still there, and sometimes the first mile or two took a while before I felt properly warmed up. Other times the legs just felt heavy.

There is obviously a difference between normal training fatigue and something genuinely hurting, but during a bigger marathon block I don't expect to bounce into every session feeling brilliant. Tuesday's tired legs also didn't define the rest of the week, which became fairly obvious after the rest day.

I Still Took Thursday Completely Off

Thursday's contribution to the 100km total was 0km. When you're creeping towards a big weekly number, taking a full day off can feel slightly strange because you know the mileage still has to come from somewhere. Removing one day gives you less room to play with, but I kept it in anyway.

By Friday my legs felt considerably better. The session was Broken Miles, 12.31km in total with shorter, faster sections, and it ended up being one of my better runs of the week.

"The speed session went really well. My legs felt great and I could really push on the faster, shorter segments. Having the rest day was crucial for me to reset midweek."

I probably appreciated that rest day more because of how Tuesday had felt. With more mileage going through the legs, I didn't want recovery to be the first thing sacrificed just to hit a bigger total.

Most of the Running Wasn't Fast

This is one of the things that disappears when you only see somebody's weekly distance. 100km sounds like a lot of hard running, but most of mine wasn't.

The progression run, Friday's Broken Miles and sections of Sunday's long run carried the quicker work. The rest was deliberately relaxed. On easy days, I kept the effort genuinely comfortable rather than turning everything into steady running because I happened to feel good.

Research into marathon training generally shows the same broad pattern. Faster marathon runners tend to accumulate more total volume, but much of that additional mileage comes at lower intensities. That matched what I needed from the week. If I was asking my legs to cover more distance than usual, there wasn't much value in trying to prove my fitness every time I went outside.

The 36km Long Run Was the Bit I Wasn't Sure About

By Sunday morning I'd already run more than 64km and still had a 36.26km long run to do, including marathon pace work. This was the session I had doubts about.

"I wasn't sure if the long run was going to be possible, or how far I'd get before the legs would give up. I certainly didn't expect to go the whole way given the weekly mileage I'd already completed."

It ended up being one of my strongest runs of the week. Getting out early helped, but I think the bigger reason was simply that my body had been prepared for it. The jump to 100km hadn't come from nowhere. I'd already completed several weeks between 85km and 95km during the block, and there had been planned recovery weeks between the bigger periods of training.

That background mattered far more than anything I did differently during this particular seven-day stretch.

Building Up to 100km

I wouldn't take this week as a template and try to copy it kilometre for kilometre. If you're currently running 40 or 50km each week, suddenly trying to hit 100km because you've seen somebody else do it would be a completely different situation to mine.

The old idea that everybody should increase their mileage by exactly 10% each week is too simplistic. Running load doesn't work that neatly. Your training history, session intensity, recovery, previous injuries and the amount of time you've spent consistently running all affect what you can tolerate.

For me, 100km came after more than a decade of regular running and a gradual increase throughout this marathon block. The week immediately afterwards dropped back to around 65km, which was deliberate too. More training only works if you can recover from it and keep training.

Finding Nearly 10 Hours to Run

The physical side was only part of it. 100.5km took me 9 hours and 32 minutes of actual running, and then you've got everything around it: getting changed, showering, eating, washing kit, preparing bottles, sorting gels and working out where you're actually going to run.

Around 80-90% of my mileage that week happened before work, which meant plenty of 5:30am and 6:00am alarms. That was probably the biggest adjustment once the mileage started climbing. You can't keep adding running indefinitely and expect the rest of your life to magically move out of the way.

I started doing a lot more the night before. Kit laid out, session checked, route roughly planned, wake-up time sorted, food and drink ready if I needed them. It sounds boring, but boring preparation is useful when your alarm goes off before sunrise.

I was also fitting all of this around work and childcare, so the training had to fit the week rather than the week being built entirely around running.

"Everyone's personal, social and work circumstances are different. It's important you aren't just copying others, but building a formula that works for you."

That's one of the things Strava can't really show. Two people can be aiming at exactly the same marathon time while having completely different amounts of time available to train for it.

Eating Enough Became Part of the Training

More mileage meant more food. That sounds obvious, but I didn't always feel massively hungry immediately after running. Quite often it would catch up with me later in the day, so regular meals stayed fairly normal while more snacks started appearing between them.

Before shorter morning runs I kept things simple with carbohydrate-rich foods such as oats, cereal bars or puffed rice products. The long run needed more planning. The evening before, I'd have a carb-heavy meal. Before running I used Maurten Drink Mix 160, then during longer sessions I was practising the sort of fuelling strategy I expected to use on race day, usually taking a gel every 5-6km.

I did make one fairly basic mistake during the 36km run. I was away from home and hadn't brought enough gels with me to follow the fuelling plan properly. The run still went well, but "I felt good so I got away with it" isn't much of a marathon nutrition strategy. If I'm going to spend time planning the route and the session, the fuel needs the same attention.

What I Ran In

The shoe rotation got plenty of use. For easy runs I moved between the HOKA Clifton Pro, Mizuno Wave Rider 30 and New Balance 1080 v15. The progression run was in the adidas Adizero Adios Pro 4, Friday's speed work in the New Balance FuelCell SuperComp Elite and the Sunday long run in the New Balance FuelCell Rebel.

For the easy mileage, comfort mattered most. When you've already got plenty of kilometres in your legs, I find a comfortable daily trainer makes it easier to keep those runs where they should be. I don't want a shoe making an easy morning feel like an invitation to push the pace.

The less glamorous discovery was how much kit you get through. Six running days, with two separate runs on Saturday, means a lot of shorts, tops and socks disappearing into the washing basket. Having enough kit in rotation suddenly becomes surprisingly important.

Did Running 100km Make Me Faster?

There was no magic moment when I hit kilometre 100 and suddenly became a better runner. Higher training volumes are associated with faster marathon performances, but that doesn't mean more mileage automatically produces more speed.

Experienced runners may be able to handle more running because they've spent years building the fitness required to do it. Recovery, genetics, training quality and available time all sit alongside mileage. For me, the change was something I noticed a few weeks later.

"A few weeks afterwards I could tell I was running well. This, combined with the weeks of gradually increasing mileage and consistency, must have had a good impact overall."

That's how I look at it now. The 100km week wasn't responsible for everything. It was one part of a much longer marathon block, and the consistency around it mattered more.

Would I Recommend Running 100km a Week?

I don't think 100km is something you need to "achieve" as a runner. If you're already comfortably running 80-90km and a structured marathon build naturally takes you towards 100km, it might make complete sense. If you're running 40km and thinking about doubling it because somebody you follow has posted a three-figure week, that's very different.

One of the largest datasets we have puts average marathon training volume at around 45km per week. There are plenty of runners training successfully for marathons without getting anywhere near 100km.

It depends on what you're training for, what your body is used to and what you can realistically fit around the rest of your life. If you're making a significant change to your mileage and aren't sure how to approach it, working with an experienced running coach or appropriately qualified professional is far more useful than copying somebody else's Strava.

Was the 100km Week Worth It?

For me, yes. I liked seeing 100.5km on the weekly total and I'd be lying if I said the number meant absolutely nothing, but it wasn't the part I'm happiest with.

"It feels great to say you've done it, but it's more important that you work out what's right for your training and make sure you're doing it for the right reasons and at the right time within a training plan."

I'd recently been through a period where injury had stopped me running, which probably changed how I looked at the whole thing too. Being able to complete the week, recover from it and continue the build towards Berlin meant more than forcing 100km onto Strava.

A few years ago, 100km would have felt like an enormous week. During this block, it arrived after months of consistent training and then I moved on to the next one. That's probably the bit I'm most pleased with.