For a second, I consider turning back and finishing the half marathon on the treadmill. It’s patiently waiting for me with its trusty conveyor belt 100 miles away in a warm gym. Instead I’m standing in a whorl of cold sunshine and pine needles somewhere near Dundee, shading my eyes from a stinging wind. I’m at the start line of my first post-injury race, and up until now, I’ve only been running indoors.

“On your marks.”

I panic that my legs won’t know how to run unless the earth starts to rotate backwards below them.

“Go!”

Three months ago I developed a gnarly knee injury due to overtraining and running on concrete. My physio prescribed total rest and, afterwards, to start rebuilding on the treadmill. “[Building up to] an hour a day should be a good start until you’re fully recovered.”

The thought of spending an hour a day on the treadmill, a machine designed originally as a form of physical and mental torture, does not thrill me. When Oscar Wilde was imprisoned for ‘gross indecency’, he was made to walk on a treadmill and wrote about it in The Ballad Of Reading Gaol: “We banged the tins, and bawled the hymns, And sweated on the mill.” 

Sweating on the mills might sound like hard work, but like every runner told to stop running, I tend to panic about losing fitness. After all, my 10km personal best on the treadmill is almost seven minutes faster than my outdoor PB, so surely it must be physically easier. Mentally though? My friend Natalya sees treadmill running as torture. “A 20-minute run is basically an hour when you do it indoors.”

And yet the treadmill is manna from heaven for people who can get used to its clicks and beeps – especially for women training during the winter. A study published by This Girl Can found that 72% of women change their exercise routines during the winter. A 2024 study conducted by Women In Sport found that 65% [of women] said they were too scared to be out alone in the dark. The treadmill, for many, is a solution to keep running fitness alive through the winter.

So I decided to put it to the test. I wanted to know if spending time on the ‘dreadmill’ can lead to a stronger, faster performance outside – and what other benefits I might reap from staying warm and dry indoors.  

My physiotherapist, Mark Watkins, has trained GB ultrarunners and says that V02 max gains are the same on the treadmill as outdoors. This is supported by a study confirming that they are indeed similar when the surface is flat. Watkins also adds that biomechanics don’t change on the treadmill. Unless a runner has a super-long stride and tries to shorten it, there is no difference, he says. And, of course, there’s the fact that you can simply stop the machine if you start to feel unwell after trying a new gel or feel pain without worrying about having to schlep 8km home.

But what about losing my fitness? I’m reassured that elites use treadmills all the time. Olympian Kara Goucher uses the treadmill during winter, saying: “Sometimes workouts go by quicker because the treadmill does the thinking for you.” North Face professional athlete Elsey Davies went viral when she posted one of her ‘favourite’ treadmill workouts: 4x10 minutes at threshold pace. Oh, and with a 15% incline. Urgh.  

Peloton instructor and ultrarunner Susie Chan has achieved remarkable things, including running the desert Marathon des Sables five times. She’s also a former record holder for the longest distance run on a treadmill. “It’s a good way to practice consistent pacing. There’s no worry about route planning or stopping to cross roads. You can be steady and consistent. Plus, you can use it for all types of runs and mimic hills with incline settings. Given the unpredictable British weather, you can maintain training regardless of outdoor conditions.”

If it’s good enough for Chan, it’s good enough for me. I booked a half marathon race in Scotland and downloaded a training plan, noting that the Runna app has paces adjusted for treadmill, too. Peloton also has a ‘Road to Half Marathon’ plan with four training days each week ranging in length from 20 to 120 minutes. I bookmark it, looking at the eight weeks of sprints and intervals ahead of me. Despite my initial reservations, I feel a jolt of excitement.  

Monday 7km easy. Tuesday intervals and then another easy 10k run on Wednesday. I turn up to the gym wearing a T-shirt, leggings and trainers confident I can smash an easy run in zone two. I press start, and then look at the incline button. I’ve heard that runners should increase the incline to 1% to ‘mimic the outdoors’, but do the experts agree? Researchers from the University of Brighton conducted a study that found to emulate the outdoors, treadmill users should set the incline to 1% – but this is only necessary when going faster than 7.3 mph (8.13 mins/mile or a 23-minute time over 5km). That’s quick, so initially, I ignored the advice.

Ten minutes in, I’m struggling. I have to stop and walk because I’m so hot. I’m drenched in sweat. I start getting cold sweats thinking about my 12km of intervals the next day. I make a mental note to wear shorts.

On the fifth day, it’s time for hill sprints. I’m clutching a water bottle filled with electrolytes. I’ve been getting headaches every day, and I think that’s to do with sweating so much; understandably, running outdoors in Scotland doesn’t generate as much sweat as three minutes on the treadmill. I feel a bit silly doing a warm-up drill when everyone around me is doing ‘proper’ workouts. A man next to me stares as I prod the incline button. I decide to throw a towel over the screen. 

By week two, it dawns on me that I’m far more self-conscious in the gym. When I’m running outside, the only time I modify my behavior is to smile at another runner. In the gym, even though I thought I didn’t care what anyone else thinks, I dial up the speed so even my easy runs are fast for me. I know that’s a recipe for injury, so over the next couple of days, I try my hardest to block everyone around me out.

Halfway into my training block, I put my finger on the biggest difference between training indoors and outdoors: I don’t feel fatigued after running. I don’t have any of that bow-legged stiffness that comes with completing a tough run outside. And while I try to block out thoughts that perhaps I’m not working hard enough, it’s a fact that this is the easiest training block I’ve ever done. At my normal pace indoors, 10km is cruisy-comfy, and the extreme sweating is due to the lack of AC rather than my effort level. I reluctantly decide to add 1% of incline to all future runs.

The final 18km long run (at 1% incline) two weeks out from my half marathon hurts. I take two gels to the gym, which makes me feel like a poser. I even take my carbon-plated race shoes with me, hoping to make the long run go faster, choosing a treadmill in the corner of the gym facing a wall. This is a mistake because other than my pounding music and dehydration headache, there’s nothing to distract me. I run for what feels like hours… before glancing at my watch and realising that only two minutes have passed. I take a gel. I really need a wee. Almost 5km down. Stars are reborn and universes collide in the time it takes me to reach 6km. I brazenly put my speed up to something fast and unpredictable to make the time pass. 

At Tentsmuir half marathon, in a forest that smells of sweet pine and rich salty sea-level air that I gulp in with delight, I pass the 6km marker in no time at all. The terrain is undulating and tricky, but I spring joyfully from path to sand dune, delighted not to be inside. I’d forgotten what it’s like to smell things on a run, to wave at people and to burst from a shaded path into sunshine. I had forgotten about all the things that make running easier outside too, like declines and tailwinds. I finish the trail half marathon in 1 hour 49 minutes. It’s not a PB, but it’s not that much slower – suggesting that I’ve not lost any fitness.

All in all, treadmill training has proved pretty successful. I didn’t love it, but the results speak for themselves. If it’s dark, icy or you feel unsafe running in your area, the treadmill really can be a trusty training partner. But if you want to enjoy your sport and run for joy rather than speed, then nothing can beat a jog outdoors.

Images: Eleanor Ross