Quick Answer: Indoor stairwells have shorter, more uniform steps, a landing turn every flight, worse air, and a descent that has to be done on the same stairs. That makes the same duration easier per step and harder overall. Cut the total flights, add the descent into the work rather than treating it as rest, and manage the air.

The outdoor stair sessions were going well and then it got dark at five and icy at seven, so you moved into the building stairwell.

Same legs, same watch, same intended session. It is both easier and worse.

Four things are genuinely different and each of them changes the workout in a different direction.

What is actually different about a stairwell?

The step dimensions. Indoor stairs are built to a building code and are typically shorter than stadium steps - commonly around 7 inches versus 12 to 18 inches for outdoor stadium risers. A shorter step means less hip and knee flexion per step and less force required, which makes each step substantially easier. To match your outdoor session you need many more steps.

The uniformity. Every indoor step is identical, which is comfortable and which removes the varied loading that outdoor stairs provide. Repeating an identical movement several hundred times concentrates load on exactly the same tissue in exactly the same way, and repetitive-strain complaints are more common indoors for this reason.

The turn. A stairwell has a landing every flight, which means a deceleration, a 180-degree turn, and a reacceleration. That is genuinely demanding and it changes the exercise - there is a lateral and rotational component that a straight outdoor run of steps does not have.

The air. Stairwells are enclosed, often poorly ventilated, and warm. Carbon dioxide and humidity build up as you work, and both make the same effort feel considerably harder. This is a real effect, not a perception, and it is the most common reason an indoor session feels disproportionately unpleasant.

And the descent. Outdoors you may have a ramp or a path down. In a stairwell you go down the same stairs, which means the eccentric loading is now part of every session rather than optional.

Why is the descent the biggest change?

Because going down stairs is where the muscle damage happens, and indoors you cannot avoid it.

Climbing is concentric work - muscles shorten under load. It is metabolically demanding and produces relatively little muscle damage. Descending is eccentric - muscles lengthen under load while resisting - and eccentric work is where delayed-onset soreness comes from.

Outdoors, many people descend a ramp, a path, or a different route entirely, so a session is almost purely concentric. Indoors, every flight up is matched by a flight down, and the total eccentric load over a session is large.

The practical consequence is that an indoor stair session produces more soreness than an outdoor one of the same duration, and people who move indoors in November often assume they have lost fitness when they are actually just sore in a new way.

There is an upside worth taking. Eccentric loading is a strong stimulus for tendon and muscle adaptation, and controlled descent training genuinely builds resilience for hill running and for the knees. It is not a cost to be minimised - it is a different training effect that should be planned for.

What it should not be is unplanned. Descending fast, heavily, and unfocused at the end of a hard session is where the injury risk sits, and the last flight of a tired descent is the single highest-risk moment in the whole workout.

What Nobody Tells You About Stairwell Sessions

The air genuinely gets worse as you work. In a sealed stairwell with a group, CO2 levels rise noticeably within twenty minutes, and the effort feels harder for reasons that have nothing to do with your legs. Propping a door at the top and bottom, or choosing a stairwell with external ventilation, makes a measurable difference to how the session feels.

Handrails are a real decision, not a weakness. Using a rail on the ascent unloads the legs meaningfully and changes the exercise. On the descent, a hand hovering near the rail is sensible safety practice and does not reduce the training effect. Decide which you are doing rather than drifting into it when tired.

Two steps at a time is a different exercise, not a harder version. It increases hip and glute involvement substantially and reduces step turnover. On short indoor steps it is often the better option, because it restores some of the range of motion that indoor step height removes.

The lighting affects your descent more than you think. Poor or flickering stairwell lighting slows people down on the way down, and that is your body being sensible. If a stairwell is badly lit, that is a genuine reason to find a different one rather than to push through.

And check you are allowed to be there. Fire stairs in commercial and residential buildings are often not intended for training, doors may lock behind you, and some open only from one side. Walk the whole route once before you train in it, and know how you get out at every level.

How should you actually restructure the session?

Rebuild it around flights and descent rather than transplanting the outdoor version.

Count flights, not minutes, and expect the number to be high. With shorter steps you need substantially more of them for equivalent work. Establish a baseline in the first session rather than assuming your outdoor numbers apply.

Build the descent into the interval structure. Rather than treating the way down as rest, define the interval as up-and-down and control the descent pace. A common structure is a hard ascent, a controlled descent at a fixed cadence, and a short pause at the bottom.

Start with fewer total flights than you think. The eccentric load is new, and the soreness from a first indoor session catches people out. Half your outdoor volume for the first two sessions is sensible.

Alternate single and double steps. Doubles restore range of motion and recruit glutes; singles train turnover. Alternating flights within a session gets both and reduces the repetitive loading that uniform indoor steps encourage.

Add a lateral or turn-focused element deliberately. Since you are turning every flight anyway, make the turn tight and quick rather than wandering through it. It is free agility work.

Manage the air. Doors open where permitted, avoid the busiest hour if the stairwell is shared, and take the session outdoors on the days the weather allows rather than defaulting indoors all winter.

And descend with attention when tired - most stair injuries happen on the way down in the last third of a session. If your legs feel unreliable on a descent, that is the session finishing, not a rep to push through. This is general information, not medical advice.

FAQ: Indoor Stair Training Questions, Answered

Is a stairmaster equivalent to a stairwell?

Not really. A stairmaster removes the descent entirely, which removes the eccentric component and the injury risk with it. It is a good concentric session and a poor substitute if the descent was part of what you wanted.

How many flights is a reasonable session?

It depends far more on the building than on you, since flight heights vary widely. Set a baseline by climbing continuously for ten minutes at a sustainable pace, count the flights, and build from that number.

Should I take the lift back down?

If your goal is purely metabolic and you want to avoid soreness, yes, and it makes for a very different and quite effective session. If you want the tendon and knee resilience benefit, walk down. Just do not alternate randomly and then wonder why sessions feel inconsistent.

TL;DR:

• Indoor steps are shorter and uniform, so each step is easier and you need many more of them.
• The descent is unavoidable indoors, which adds substantial eccentric load and more soreness than an outdoor session.
• Enclosed stairwell air genuinely makes the same effort feel harder - ventilate where you can.
• Rebuild the session around flights and controlled descents, start at half your outdoor volume, and alternate single and double steps.

Moving indoors is not a downgrade. It is a different exercise with a different loading pattern, and the sessions that work in a stairwell look nothing like the ones that worked on a stadium.