Each stage here buys the adaptation the next one needs: walking thickens the structures that running loads, the continuous kilometre teaches pacing before distance, and five and ten kilometres build the weekly rhythm a half marathon demands. The order is deliberately slower than most plans because tendons and bone adapt weeks behind heart and lungs, and that gap is where beginners get hurt. Skip a stage and you pay for it further down.
Step 1: Twenty minutes of walking, on purpose
Twenty minutes of walking sounds like a placeholder, and that is exactly why it comes first. Bone, tendon and cartilage adapt far slower than your heart and lungs, so within two weeks you will feel capable of running long before your legs can absorb it - this step buys that adaptation cheaply. Do it at the same time each day, on a route you can repeat without thinking, and walk at a pace where you could hold a conversation but would rather not. Time it, do not measure distance; twenty minutes is the unit. Where this gets abandoned: people treat walking as a formality and jump to jogging in week one, then spend a month nursing shin pain on the sofa. If you have not walked twenty consecutive minutes for a fortnight, you are not ready for step two.
Step 2: One kilometre, no walking breaks
By this point you have two weeks of walking under you, so the engine is warm; the task now is converting walking minutes into running minutes without changing how often you go out. The lever is not adding more running - it is shortening the walk breaks. Start with four minutes of walking, one minute of running, repeated four times; each week take a minute off the walking and add it to the running. The pace should feel almost embarrassingly easy, slow enough to speak a full sentence out loud. Someone chasing a good 1K time here is the classic error: they arrive at the continuous kilometre exhausted, decide running is awful, and quit. Once you can run ten minutes, cover the kilometre continuously on a flat loop you already know, and only then move to step three.
Step 3: Five kilometres, mostly by feel
Five kilometres is where running stops being a novelty and starts being a schedule. Three runs a week beats one long heroic run - two short ones of twenty to twenty-five minutes and one longer one that grows by about a kilometre each week until it reaches five. That weekly long run is also where you learn to pace: the first two kilometres should feel slower than your legs want, because the last kilometre is decided there, not at the end. What people get wrong at this stage is chasing a personal best on every outing; the easy runs have to stay genuinely easy, or the long run suffers and injuries start. Pick two fixed slots that survive a bad week - a weekday morning and a weekend morning work for most people - and treat the third run as optional. When five kilometres feels unremarkable, you have earned step four.
Step 4: Ten kilometres without friction
Getting to ten kilometres is less about fitness than about friction. By now your legs can handle the time; what stops people around the seven-kilometre mark is usually not lungs but seams, wet cotton, a shoe that rubs at kilometre eight, and starting the run at a pace you have not earned. Before adding distance, fix the boring stuff: technical fabric, a sock with no ridges, a route with water or a fountain. Build the long run from five to ten over about six weeks, and keep the other runs short so the week stays survivable. One insight worth holding: the ten-kilometre wall is often a fuelling problem wearing a fitness costume - a small snack an hour before, and water every twenty minutes on longer efforts, changes more than any extra training. If a run falls apart late, check your intake before your training plan.
Step 5: Twenty-one kilometres, decided early
Twenty-one kilometres is decided in the middle weeks, not on the day. The long run needs to reach roughly sixteen to eighteen kilometres three weeks out, then drop sharply - the taper is part of the training, and skipping it is how good preparation turns into a miserable final ten kilometres. Keep the other days easy and include one faster session a week so the pace you want over the last five kilometres has been rehearsed. On the day, start slower than your goal pace for the first three kilometres; nearly everyone who fades at kilometre seventeen spent that time early. Practise your race breakfast and your kit on the longest training runs, because nothing new belongs on race day. Walking through a water station is not failure. The step before this one built the legs; this one is mostly about restraint.
A reminder in a phone gets dismissed and leaves nothing behind; a strip of paper taped by the door gets visibly shorter, and the last line stays there until you finish it. The list is short on purpose, so the missing lines are obvious. Print it, tape it where you put your shoes, and cut one off at a time.