History and origin
Zen is a Buddhist way of sitting, zazen, not a system of postures. The word names a school of attention that came through China from Indian Buddhist meditation and took a particular shape in Japan: sit, keep a simple posture, and return when thinking carries you off. Zen yoga and Zenyasa are modern joins made for people who also want a mat. One version is a short, plain movement class and then a real sit. Another is a vinyasa taught with fewer cues and less decoration. Aaron Star's Zenyasa is one named example of that second idea. The root remains the cushion.
Asana, when it appears, is preparation for sitting or a separate modern class that has borrowed the word. A studio can be precise about which it is offering. A long arm-balance sequence with a bell at the end is not zazen, and a silent sit with no poses is not a yoga fitness hour. Both can be honest. This page describes the join: a little movement, then the sit that the tradition actually cares about. It does not promise insight, a rank, or a change of character.
Philosophy
Sit, and when thinking carries you off, return. That sentence is the method. There is nothing to collect and no mood you must produce. Boredom is not a problem to fix, and a pleasant hour is not proof that the sitting worked. Movement, if the class includes it, is plain: enough to let the legs and the back tolerate the cushion. The bell starts the sit and ends it. Between the bells you do not improve the posture into a display.
How a class proceeds
A class may begin with a few slow stretches or a short, undecorated sequence, then a sit of ten to forty minutes. You face a wall or the room, the eyes are lowered, and the back is upright without being rigid. A bell often marks the start and the end. Walking meditation, slow steps in a line, sometimes replaces or breaks the sit so the legs survive. Instruction is spare. You will not be told what you should see.
It can be boring, and the boredom is left alone. If silence feels like a product you must enjoy, this hour will annoy you, which is useful information. Wear plain clothes. A chair is a real seat if the knees or the back refuse the floor. Leave if a teacher asks you to ignore pain in order to look composed. Zen economy is not an excuse for a numb leg.
Intensity
The movement, when there is any, is light. The sit is the harder part, and the difficulty is stillness and time, not load. Knees, hips and a tired back set the real limit. A chair lowers that cost without changing the practice. People returning from injury can sit. People who want a sweat will be under-served. Intensity on this scale is low to moderate only because a long sit asks for patience, not because the muscles are trained.
Benefits
A regular sit gives the day a plain edge: you stop, and then you start again, without a story about what the stop achieved. The short movement before it can make the sitting physically possible. Students often notice that they fidget less in other rooms, which is a modest and useful change. The practice does not treat anxiety, depression or pain, and a bell is not clinical care. If sitting brings up more than you can hold, shorten it and speak to someone qualified. Nothing in the method requires you to endure distress.
Who it suits
The hour suits people who want to sit, including those who need a little movement first so the body will agree. It suits anyone who can leave a result alone. It is the wrong room if you came for a sweaty sequence, a guided visualisation, or a teacher who will explain your inner life.
It is also the wrong room if silence itself is frightening and nobody has offered a shorter sit, open eyes, or a chair. A Zen title does not oblige you to be still past what you can bear. Temples and studios differ in formality. Ask how long the sit is before you book, and treat the answer as the class.
Beside similar forms
A yoga nidra lies down and follows a spoken tour of the body. Restorative yoga changes supported shapes. Mindfulness courses often talk more and sit less, and they may not be Buddhist. A vinyasa class with one minute of silence at the end has not become Zen. Zazen is upright, usually silent, and the return from thought is the whole instruction. Zen yoga adds only enough movement to make that sit possible. If the movement is the point, you are in a different class, and it should be sold as one.
Best positions
Zazen
Sit on a cushion high enough that the knees can drop, or use a chair if they cannot. The spine is long, the chin is slightly in, and the eyes are soft and lowered. The hands rest in the lap. You sit. When a thought takes you, you notice and return, without a commentary. The effect is ordinary stability, not a vision. Pain that is sharp is a reason to change the seat. Dull restlessness is not.
Walking
Walk slowly in a short line or a small circuit, the eyes down, the hands still. Feel the foot meet the floor and leave it. The pace is slow enough that balance stays easy. Walking is used between sits so the legs do not go numb, and it is a practice of its own, not a break you fill with talk. If the room is crowded, shorten the step rather than weave.
Plain stand
Stand with the feet together or hip-width, the arms at the sides, and take three uncounted breaths. This is a pause before sitting, not a pose to refine. It lets the blood settle and gives late arrivals a way into the room. Do not lift the chest into a shape. The effect is simply that you are here, upright, and finished with the walk to the cushion.
Easy fold
If the class uses movement at all, fold forward from standing only as far as the back stays long, knees soft, hands on the thighs or the shins. Stay for two or three breaths and rise. The fold eases the back of the legs enough that sitting is less of a fight. It is not a hamstring project. Come up if the head pounds or the low back rounds into a pinch.
Seated side reach
Sit and walk one hand to the floor beside the hip, the other arm reaching overhead only if the ribs still breathe. Stay for two breaths and change sides. The reach gives the side body a little room before a long sit. Keep it small. A deep side bend is a different class. Skip it if the shoulder complains.
Plain rest
Lie down only if the class includes a rest, and do not decorate it. Arms by the sides, eyes soft, one minute. The rest lets a stiff sitter leave without carrying the cushion into the street. It is not yoga nidra and it needs no script. If lying down is the part you came for, book a restorative hour instead.