How to Train for a 100KM Ultramarathon Whilst Working Full Time

By a full-time solicitor who conquered a full Ironman, ran 570 km across Ireland, and completed 50 marathons in 50 days (yes, really!).

Completing my first Ironman 2 weeks after a blood clot, whilst working 60+ hour weeks in law.

Training for a 100KM ultramarathon is no small feat. Especially when you're juggling a full-time job, family responsibilities, and the endless to-do list of adult life. But it can be done. I've trained for and completed a full Ironman, ran 570 kilometres across Ireland in five days, and finished 50 marathons in 50 consecutive days. All whilst working a demanding legal job. I didn't have unlimited time or resources. What I had was structure, discipline, and an obsession with proving that we're capable of far more than we think.

In this guide, I'll break down how you can train smart for a 100KM ultramarathon without burning out or quitting your job. This isn't a cookie-cutter plan; it's a framework. You'll learn how to manage your time, build your mileage sustainably, strengthen your mindset, recover wisely, and gear up efficiently.

What Does 100KM Training Actually Involve?

A 100KM race (roughly 62 miles) demands endurance, resilience, and mental toughness, but not necessarily sky-high weekly mileage. Many aspiring ultrarunners think they need to train like professionals, logging 100-mile weeks. That's not true. Most full-time workers can get ultra-ready on 9-12 hours of training per week.

Here's what matters most:

• Consistency over volume: Running regularly (5-6x per week) matters more than high mileage binges. Trying to binge all your weekly mileage into one big run is not very fruitful. It's the accumulation over time that builds endurance.

• Long runs are your cornerstone: Weekly long runs build the physical and mental stamina you'll need on race day. Ideally, you'll build up to 4-6 hour efforts. For a 100KM race (especially your first one) I do not recommend having your long runs longer than 60km as going above that is not in line with the risk vs reward.

  
  

• Back-to-back runs: These simulate the fatigue of ultra distances. A long run on Saturday followed by another long run Sunday is gold.

  
  

• Specificity: If your race has hills or trails, train on them. Practise with the gear, nutrition, and terrain you'll encounter on race day. On race day nothing should be new to you. If possible, I highly advise doing a recce of the course. If it is a looped course e.g. 5 loops of 20km, I advise doing the loop at least once or twice if possible a few weeks before the race to familiarise yourself with the terrain and to devise a proper race strategy.

  
  

• Strength training: One to two sessions per week of core and lower-body strength work can prevent injuries and make you a more efficient runner. I put a high emphasis on core work for all of my athletes. In endurance races, especially ultras, the longer the race the more likely your running form is to break down, which causes you to use more energy in order to run as you become less efficient. Having strong core can help you delay the onset of your form breaking down, allowing you to run more efficiently for longer.

  
  

Time Management: Making It Work Around a Busy Life

When I was working in corporate law, I had to get creative to fit training around meetings, deadlines, and long hours. Training for an ultra while working full-time doesn't mean sacrificing your relationships or your sanity. It means building a routine that fits your life.

Strategies that worked for me:

• Early mornings: Pre-dawn runs became my secret weapon. Getting out the door before emails and meetings start gives you consistency and control. Watching the sunrise whilst others sleep is tough at first, but it's incredibly empowering once it becomes routine. Plus, nothing crazy from work can derail a run that's already done before 7 a.m.

  
  

• Lunch break "runches": If your office has a shower or you live near work, a 45-minute midday run can be a great use of time.

  
  

• Evening sessions: Some days, work will extend into the evening or exhaustion will hit. But if you missed a morning run, consider lacing up after work. I've logged many 9 p.m. runs around my neighbourhood. Not ideal for circadian rhythm, but sometimes necessary. On particularly high-volume weeks, I even split runs into two shorter sessions (morning and evening) when I couldn't afford one long window.

  
  

• Weekend long runs: These are key. Treat them like appointments you can't miss. If you've only got one free training window per week, this is where it should go.

  
  

• Stacking volume: If you can't get one long run, break it into two moderate-length runs across the weekend. The cumulative fatigue will still serve your goals.

The trick isn't finding huge blocks of time. It is being consistent in the small windows you do have. Training whilst tired after a workday? That's great mental prep for the late stages of an ultra.

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A Sample Training Week (Framework Only)

• Monday: Rest or 50-60 min recovery jog

• Tuesday: Quality session (e.g. hill reps, tempo, or intervals ~50-60 min) + strength training

• Wednesday: 60-90 min aerobic run (easy to moderate effort)

• Thursday: Easy 50-60 min run + strength training

• Friday: Easy run or cross-training 50-60 min

• Saturday: Long run (start at 2 hours, build to 5-6 hours over the block)

• Sunday: Medium run (90 min to 2 hours) or active recovery (e.g. bike)

This structure can flex depending on your job and life commitments. The key is getting your long run and one quality session in weekly (for trail/hilly ultra this will be hill work), then building consistency around that.

Recovery: The Secret Sauce

Recovery is not just rest. It is part of your training. Especially with a job in the mix, your body needs every opportunity to rebuild.

Key recovery tools:

• Sleep: Non-negotiable. Aim for 7-9 hours a night. Short on time? A 20-minute power nap can work wonders.

• Fuelling: Post-run nutrition should include both carbs and protein. Do not skip meals. Consider bringing recovery shakes to work. Aim to hit a minimum of 1g of protein per lb of bodyweight daily.

• Hydration: Drink water throughout the day. Add electrolytes if you are doing back-to-back runs or training in heat.

• Mobility and bodywork: Foam rolling, massage guns, or a simple yoga routine once a week helps with muscle maintenance.

• Sauna and cold therapy: Sauna, ice baths, or even just elevating your legs can aid recovery.

During my 50 marathons in 50 days, recovery became an art. It was not about fancy tools. It was about discipline and consistency. Eat, rest, hydrate, repeat.

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Mindset and Mental Strategies

If you're training for a 100KM, your body needs to be strong, but your mind needs to be stronger. With work stress, early alarms, and tired legs, there will be plenty of days where quitting feels easier than continuing.

What helped me:

• Have a why: Know why you are doing this. Write it down. Return to it when motivation dips.

• Break the big into small: Long run? Focus on the next 5K. Big week ahead? Just win the next session. These small wins all add up.

• Visualise success and struggle: Imagine the finish line, but also rehearse how you'll respond when things go wrong.

• Train the mind too: Do some runs without music or podcasts. Get comfortable with discomfort. Running in silence, with no music, can also be a type of meditation as it allows you to focus on your breathing and get in a rhythm. If the race itself is set to happen overnight, then do one of your long runs overnight as well. This can help you prepare mentally and logistically for any challenges that you may face at that time of the race.

• Don't let perfect be the enemy of good: Some training weeks will go off the rails. Don't spiral. One week doesn't define your entire block. Training, like many other things in life, follows the rule of thirds: a third of the training sessions will feel great, a third will feel mediocre, and a third will feel terrible. Focus on consistency rather than perfection.

Running 570km across Ireland, I learned that forward motion, even slow, even painful, always leads somewhere. Trust that.

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Gear You Actually Need

Ultrarunning gear can be overwhelming. Here's what you actually need to get started:

• Shoes: Trail shoes if you are running on trails. Prioritise comfort and fit. Size up by half. For the actual race I advise having an extra pair another size up that you can change into about 50-60km into the race (if there is an option to do so at an aid station).

• Socks: Anti-blister socks. Worth every penny.

• Hydration vest: These come in handy for long runs, especially on trails. Get one that fits snug and can hold soft flasks or a bladder as well as any food/fuel you want to consume during your run or race.

• Headtorch: If you will run in the dark.

• Anti-chafe: Apply generously. Better safe than sorry, trust me.

• Recovery tools: Foam roller, massage gun, or lacrosse ball. All are great extras on top of the essential sleep and nutrition. Get the basics right first.

• Watch: GPS watches like Coros Pace, Garmin Forerunner/Fenix for tracking long efforts. Although not essential, they are extremely useful especially for longer runs on trails. Many of these watches allow you to download maps to help you navigate as well as track your running progress.

Start simple. Upgrade slowly. Your legs, not your gear, get you to the finish line.

Nutrition Strategy: Fuelling for Success

Completing 50 marathons in 50 days in Dublin.

A comprehensive nutrition strategy is vital for ultramarathon success. During training and racing, aim to consume 60-90g of carbohydrates per hour, depending on your body weight and metabolism. Practise your nutrition strategy during long training runs to find what works for your stomach.

Variety is important. Alternate between gels, energy bars, real food, and liquid calories to prevent flavour fatigue. Long runs during your training block are perfect for figuring out what actually works for you. Personally for any event that is 6+ hours I cannot rely on gels alone for energy as I get taste fatigue from sweetness. Aleksandr Sorokin, 100KM and 24 hour world record holder, in our interview recommends having a mixture of sweet, savoury and salty fuel options to avoid taste fatigue. However, we are all different, so this is something you need to trial and find out for yourself to see what works for you.

Experiment with caffeine timing, especially if racing through the night. And remember that hydration and electrolyte balance are just as important as calorie intake. Aim for 500-750ml of fluid per hour, adjusting based on temperature and sweat rate.

Why a Coach Helps

This framework is a great starting point, but execution is where most people struggle. A coach can:

• Tailor training to your schedule and fitness

• Monitor load and recovery

• Hold you accountable

• Make adjustments when life inevitably intervenes

If you are serious about your 100KM and time is your biggest barrier, a coach helps you spend that time wisely.

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Final Thoughts

Balancing work and ultra training is not easy, but it is definitely possible. You'll have to wake up earlier than you'd like. Say no to some things. Learn to train when you're tired. But what you gain is so much bigger: confidence, resilience, and proof that you can do hard things.

You don't need a perfect schedule or elite fitness. You need a plan, consistency, and the belief that your goal is worth the work.

You've got this. Now go chase that finish line.

Run smart. Work hard. Recover well.