Stamina is a different skill from speed

Most hillwalkers who struggle on big days do not struggle because they are slow. They struggle because they run out of endurance somewhere after the fifth or sixth hour, and everything beyond that point becomes a grind. Speed helps you finish earlier, but stamina is what keeps your legs and lungs working when a day in the hills stretches past eight hours. The good news is that stamina responds very predictably to training. It simply needs patience and a bit of structure.

Extend your time on foot first

Before worrying about pace, get used to being out for longer. If your usual walk is four hours and 12km, don't jump straight to a 25km epic in Eryri. Add roughly 10–15 per cent to your longest outing each week or fortnight, or simply add an hour to the clock. Time on feet matters more than distance on the map, because rough ground in the Lake District or the Scottish Highlands is far slower than the numbers suggest.

Useful markers along the way:

• A comfortable five-hour day with 600–800m of ascent
• A six- to seven-hour day with 1,000m, ideally on mixed terrain
• Back-to-back days of five hours each, which teach you what genuinely tired legs feel like

Back-to-back days are the closest thing to a long hill day you can train for without actually doing one. They also reveal how well you recover overnight, which matters enormously on multi-day routes.

Seek out steep ground

Distance alone won't prepare you for a long ascent. Steep ground uses your muscles differently, raises your heart rate quickly, and forces you to manage your breathing. Make a point of including genuine gradient in your training, whether that's a fellside path, a long series of stone steps, or a steady forestry track climbing for 300m without a break.

Hill reps are the classic tool. Find a slope offering 100–200m of ascent and walk up briskly, then descend at an easy pace to recover. Start with three or four repetitions and build to six or eight over a few weeks. On longer outings, aim to accumulate 800–1,200m of ascent in a day, which is roughly what a demanding UK hill day will ask of you. If your local hills are modest, loop a short steep climb repeatedly rather than settling for flat miles.

Don't neglect the descents

Tired quads undo more walkers than tired lungs. Downhill walking loads the legs eccentrically, and it is the part of a long day that leaves you stiff for days afterwards. Include descents in your training, especially on rough ground where you must place your feet carefully and think about every step. If you can, finish a walk with a long, steady descent rather than a gentle stroll back to the car park.

Light strength work helps too:

• Step-downs from a low wall or step, keeping the movement slow and controlled
• Single-leg squats to a chair, which build the stability you need on loose ground
• Calf raises, especially if you walk in stiffer boots or carry a heavier pack

Build a weekly rhythm you can actually keep

Consistency beats heroics every time. A realistic week might look like one long walk of four to seven hours, one shorter session with real climbing, and two or three easy walks or cycles on gentler days. If you can only manage two outings a week, make one of them long and one of them steep, and accept that progress will be slower but still steady.

Recovery is part of the plan, not a break from it. Long days create fatigue that takes a couple of days to clear, and training hard on tired legs without any easy days leads to niggles rather than fitness. Sleep, proper meals and a genuinely gentle day now and then will do more for your stamina than squeezing in an extra session you are not ready for.

Pace yourself and keep fuelling

On the day itself, the biggest gains come from pacing and eating. Start slower than feels natural, particularly on the first climb of the morning. Aim to hold a pace where you can speak in short sentences; if you are gasping on the first ascent, you will pay for it by mid-afternoon. Walk uphill steadily, take short and frequent breaks rather than long ones, and resist the urge to race the early descents.

Eat little and often, beginning within the first hour. Something in the region of 50–60g of carbohydrate an hour suits many walkers on a long day, alongside regular sips of water. Keep your pack as light as you reasonably can, carry poles if your knees complain on descents, and layer up before you get cold rather than after. A long hill day tests patience as much as fitness, and the walkers who finish comfortably are usually the ones who started conservatively and kept nibbling all the way round.