An outdoor walker in Glasgow can expect rain on roughly one hundred and seventy days a year. A walker in Manchester, slightly fewer. A walker in any UK town in November has perhaps forty-five minutes of daylight after they finish work. These are not edge cases. They are the conditions in which most UK walkers spend most of their walking year. The treadmill question is not whether indoor walking counts. It is whether the research that supports outdoor walking also supports the indoor version — and if so, how to set the machine.
The short answer is that treadmill walking, when paced and structured the same way as outdoor interval walking, produces the same physiological response. The slightly longer answer is that almost no treadmill programme sold to UK households is designed for walkers. They are designed for runners. The speed bands, the incline defaults, and the on-screen coaching are all calibrated for someone trying to break six-minute miles. The walker setting their treadmill to four kilometres per hour and a flat zero per cent incline is following a protocol that does not exist, and getting steady-pace results — which, as the Shinshu group showed in 2007, is to say barely any biological response at all [1].
The treadmill is, for walking, an ideal piece of equipment
This is not the conventional view. The conventional view holds that outdoor walking is better — more varied terrain, sunlight, fresh air, mental break. All true. But for interval walking specifically, the treadmill has an unusual set of advantages. It enforces a constant pace, which is exactly what intervals require. It eliminates the temptation to slow down on the brisk blocks because the floor is slowing for you. It removes weather as an excuse. And it gives you a digit on the console that maps directly to "brisk" or "easy" once you have calibrated what those mean for your stride.
The trade-off is that the treadmill removes the by-feel pacing the Japanese Walking Method relies on. Outdoor walkers regulate by breath and conversation: brisk = talk in short sentences, easy = recovery. On a treadmill, the regulator is the number. This means that before any treadmill programme works, the walker has to identify their brisk number and their easy number. Most consumer-treadmill owners have never done this calibration in their life. They use the default speed the machine starts at and adjust upward by trial and error. A two-walk calibration session — one to find the brisk pace by feel, one to translate that into a km/h reading — is what unlocks the indoor protocol.
What the research actually shows about indoor vs outdoor
A small body of comparative work has tested treadmill walking against outdoor walking at matched intensities. A 1996 paper in the Journal of Sports Sciences found that treadmill walking elicited the same VO₂ response as outdoor walking when the incline was set to one per cent — a setting designed to compensate for the absence of wind resistance and surface variation [2]. A more recent 2014 study looked specifically at energy expenditure during interval-style treadmill walking and confirmed that, with appropriate incline, the cardiovascular load is equivalent to outdoor [3]. The "one per cent incline" finding is now standard advice in sports-science textbooks and is the default for any serious treadmill-walking programme.
What this means in practice is small but important. The walker following the Japanese Walking Method on a treadmill at one per cent incline, with their brisk and easy speeds correctly calibrated, gets the same blood pressure response, the same aerobic-capacity response, and the same fat-loss response as the walker doing the same protocol outdoors. The science does not penalise the indoor version. It penalises the under-paced version, indoor or outdoor.
Why treadmills come into their own for walkers over thirty-five
The audience that benefits most from indoor walking is the demographic PaceReset writes for. Adults thirty-five and over are more likely to have a treadmill at home (children, work-from-home, the lock-down purchase that never went back to the gym). They are more likely to walk after dark in winter, which is uncomfortable or unsafe in many parts of the country. They are more likely to have a knee or a hip that responds to a controlled surface better than to wet pavement. They are also — and this matters — more likely to track outcomes, and a treadmill produces three perfectly-tracked numbers every walk: distance, average speed, calories. The interval walker who logs those three numbers over twelve weeks gets a compliance graph the outdoor walker has to build by hand.
The science does not penalise the indoor version. It penalises the under-paced version, indoor or outdoor.
The walking-pad version of the same conversation
A category note: under-desk walking pads have exploded in the UK market in the past three years, driven by work-from-home and the Tiktok wellness cycle. They are not the same machine as a treadmill. Pads typically max out at around six kilometres per hour and do not incline. For steady walking during meetings, they are excellent. For the brisk-pace blocks of the Japanese Walking Method, they are usually just capable — brisk-by-feel for most over-thirty-five walkers lands around five point five km/h, which sits in the upper third of pad capability. The walker who wants to do the proper protocol on a pad gets a thinner margin for error, but it can be done. The walker who has a real treadmill has more room.
The console card
The single most useful artifact for treadmill interval walking, and the thing most absent from existing programmes, is a card sized to sit on the speed bar with the brisk speed, easy speed, incline, and minute-by-minute timing visible at pace. Walkers cannot read a phone at brisk pace, will not read a tablet at brisk pace, and forget speeds within three rounds. A card that lives on the speed bar removes the cognitive overhead and lets the walker focus on what the protocol actually asks: walk briskly, then walk easily, repeat, finish. PaceReset's Treadmill Edition ships one. So does any treadmill-walking programme that takes its own subject matter seriously.
For the UK walker who finds themselves staring at a dark Tuesday evening in November — or a wet Saturday morning, or a heatwave week in July — the treadmill is no longer a substitute for the real walk. With the protocol on the bar, it is the real walk. The science is the same. The numbers move the same. The only thing that changes is the weather report.
