How Fast Can You Get Fit for a Big Challenge?

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An opportunity can present itself at any time. But if a physical challenge comes up at the last minute – someone drops out of a marathon and you get offered their place, for instance – you have to ask yourself: can you get ready in time?

Or maybe you’re considering signing up for a place on the Fitbit Fifty, which challenges you to run and cycle the length of the country (and back) with a team of like-minded people, but the prospect seems a bit daunting.

The good news: you can still get it done – depending on how hard you’re prepared to train in the time you’ve got left. We talked to Chris Brisley – an endurance specialist who’s run, swim and cycled more than 6,000 miles of challenges and races – about how well you can expect to fare on your next challenge if you’ve left it a bit late.

The Fitbit Fifty

If you’re a beginner: This would take a while to prepare for. “It’s not just the muscles that need to adapt, it’s your tendons and surrounding musculature, which haven’t been exposed to those gentle stresses they need to get used to to cover this distance,” says Brisley. “That’s why people tend to be in so much pain post-ultra.” The rests you get as your team-mates tackle the distance would help, but you’d still need a minimum of 12 weeks’ training to give it your best.

If you’re an intermediate athlete: Good news! Sort of. “In a lot of ways, those extended bike sections are going to be a lot easier than the running,” says Brisley. If you’re prepared to train pretty aggressively – think one training session every weekday, plus a long running and cycling session on Saturday or Sunday to get your legs used to doing both on the same day – you could probably prep in ten weeks.

If you’re already advanced: You could get the preparation done in six weeks, if you’re already putting in more than 50 miles a week on the bike with three or four lunchtime runs. One caveat: you need to get your fuelling strategy right. “The most important thing for any ultra-endurance or multi-day event is going to be food and water,” says Brisley. “The moment you get that wrong, your mind is going to start going all over the place, and that’s when you’ll cave. Your brain goes haywire. It’s almost self-induced, because our ‘second’ mind is in our gut. The longer the event, the more important this is and that’s where experience really helps. In my experience, I don’t do well on energy bars or sports drinks, – they really screw up my stomach. There’s a lot of sugar in them.” Schedule in a couple of long-distance easy-pace efforts to gauge your body’s response to fuel sources and you’ll be ready to hit the road.

RECOMMENDED: Be the First to Conquer The Fitbit Fifty Endurance Challenge – Apply Now!


If you’re a beginner: “It depends how fast you want to go and how important being able to walk afterwards is,” says Brisley. “Someone who’s never raced or goes out for the occasional jog would be able to finish a marathon without doing any training at all. You’d have to do some sort of walk-run-walk-run thing once you started to cramp up, but you could get through it. It’s just that it might take five or six hours, or longer, and you might not be able to walk for a couple of weeks. If you’re overweight and unfit, of course, you shouldn’t try it without training: it’s too much stress, not just on your body but psychologically. Also bear in mind that people have died from trying that sort of thing.” Unsure? Consult a doctor before you try it.

If you’re an intermediate athlete: It starts to depend on your training philosophy. “I did the Chicago marathon with less than nine weeks’ training and ran sub-four hours,” says Brisley. “I’d done very little before that – apart from a competitive 10K, I’d been recovering from a back injury. If you want a decent time, then on the right programme you need 12 weeks.”

If you’re already advanced: At this point, it comes down to how much you’re going to taper, something ultramarathon runners love to debate. “There are different schools of thought about resting in the weeks before a big run and I’ve practised a few of them,” says Brisley. If you take that element out, you could cut down the typical 12-week marathon plan to ten weeks.

“Most marathon plans increase the weekly mileage by 10% each week, but if you’re prepared to risk upping your distances faster than that, which wouldn’t be very pleasant, you could cut a couple of weeks – though you’d need to devote some time to making sure you were eating and resting properly to maximise recovery. You could get your training down to four to six weeks and finish in a reasonable time, which means under five hours. For a good time, you’ll need at least nine weeks.”

RECOMMENDED: How to Train for a Marathon in Six Weeks

A 100-mile Cycle Sportive

If you’re a beginner: This is a slightly easier option than a long-distance run. “Unless you’re racing, then even a relatively long-distance bike ride is going to be a lot easier than a marathon as long as you’ve put in some time and you’ve got a basic level of confidence on a bike,” says Brisley. If you’re a complete beginner, British Cycling has a 25-week training plan with your name on it, but assuming that you can ride a bike and know the rules of the road, you can get away with much, much less: ten weeks will make sure you can at least finish the course.

RECOMMENDED: 10 Tips for Your First Cycling Sportive

If you’re an intermediate athlete: This comes down to whether you’re going with a group and if they’re going to expect you to take a turn at the front. “If you’re cycling within a group, you’ll be able to draft [ride behind other riders to take advantage of their slipstream] on tough sections and hills, but then you’re expected to keep up and help each other and if you haven’t done any training, then that’s a problem.” There aren’t usually hard and fast rules about drafting at sportives, but doing the whole course on a stranger’s back wheel might be frowned upon. If you’ve got minimal time left, this seven-week Panic Plan will get you to the finish line – though not as fast as you might like.

RECOMMENDED: How to Cycle in a Group

If you’re already advanced: Already putting in upwards of 60 miles on the bike a week? Jump in and give it a shot – no extra training required. Your muscles won’t need to adapt to impact in the same way they do for running and there’s very little eccentric movement on the bike (ie movement requiring muscle contraction) so you might not even get crippling DOMS.

Olympic Triathlon (1,500m swim, 40km bike, 10km run)

If you’re a beginner: It’s really all about the swimming. If you’re confident enough at front crawl to get through 1,500 metres, you’ll be able to get through the bike and run with minimal prep. If not, “you can do other strokes than front crawl, it’s not against the rules,” says Brisley. “I’ve seen guys in Ironman races doing breaststroke and some of them can go pretty fast. It’s not something I’d recommend, though. If you’re not confident in open water give yourself at least six weeks to improve your stroke, which should also be enough time to get in some distance running and cycling, too.”

RECOMMENDED: 12-Week Olympic Triathlon Training Plan

If you’re an intermediate athlete: “If you’re a competent swimmer, you could do an Olympic triathlon in a month,” says Brisley. “But then you’re looking at a 2hr 30min sort of time.” In an ideal world, you’d give yourself at least eight weeks to bring your 10K time down and get in some “brick” sessions – going straight from a bike ride into a run – so your quads don’t start screaming when you try it in the race.

If you’re already advanced: If you’re comfortable in all the disciplines, an Olympic triathlon is probably the easiest race to tackle with zero notice – something to remember when your boss suddenly mentions he’s got a spare place in one with some picturesque scenery. Got a week to scrounge together a wetsuit and bike and practise your transitions a couple of times? Go for it.

Joel Snape

From 2008 to 2018, Joel worked for Men's Fitness, which predated, and then shared a website with, Coach. Though he spent years running the hills of Bath, he’s since ditched his trainers for a succession of Converse high-tops, since they’re better suited to his love of pulling vans, lifting cars, and hefting logs in a succession of strongman competitions.