People who abandon meditation frequently do so because sitting is uncomfortable, and the discomfort is treated as something to overcome mentally when it is generally a positioning problem.
The pelvis
The critical element and the one most often wrong.
Sitting flat on the floor with the pelvis tilted backward forces the lower back to round, which requires muscular effort to maintain and becomes painful.
Raising the hips above the knees tilts the pelvis forward, which allows the spine to stack without effort.
Which is why cushions exist, and why the height needed varies enormously between people according to hip mobility.
Hip mobility
Cross-legged sitting requires external rotation at the hip.
Which varies substantially between individuals for anatomical reasons — hip socket depth and orientation differ, and these are structural rather than trainable.
Forcing a position the joint does not permit transfers stress to the knees, which is where most meditation injuries occur.
If knees are painful, the position is wrong for that body rather than the body being inadequate.
Alternatives
Kneeling, with a bench or cushion supporting the weight, removes the hip rotation requirement entirely.
Sitting on a chair, with feet flat and hips slightly above knees, is entirely legitimate and is used in many traditions.
Lying down works for some practices and encourages sleep, which is why it is generally avoided for concentration practice.
Standing and walking practices exist in most traditions and are underused.
The spine
The aim is a position that can be held without muscular effort, which means stacked rather than held upright.
Which is achieved by pelvic position rather than by pulling the shoulders back.
Deliberately straightening produces tension that becomes fatigue within minutes.
Legs going numb
Generally compression of nerves or reduced circulation from the position.
Which is uncomfortable and not dangerous over short periods, and it resolves on moving.
Persistent numbness, or numbness that does not resolve quickly, warrants changing position and, if it recurs, medical advice.
Duration
Starting with short periods and extending gradually allows tissues to adapt.
Which is the same principle as any physical practice, and attempting long sits immediately produces pain that discourages continuation.
Movement during practice
Traditions differ on whether adjusting position is permitted.
The practical position is that pain distinguishable from mere discomfort should be addressed by moving, since sitting through it risks injury and produces nothing useful.
Existing conditions
Anyone with knee, hip or back problems should adapt the position rather than attempting the conventional one.
Which is what any competent teacher will advise, and reluctance to accommodate it is a reason to find a different teacher.
A physiotherapist can advise on positioning for a specific condition.
The props that help
A firm cushion raising the hips, with height adjusted to what the individual needs.
Support under the knees where they do not reach the floor, which removes the strain of unsupported weight.
A wall behind, which is entirely legitimate for people who cannot yet sit unsupported.
Which are practical adjustments rather than compromises, and traditions that use them extensively exist.
Building tolerance
Sitting is a physical activity requiring adaptation, and tissues adapt to sustained positions over weeks.
Which means starting with five or ten minutes and extending gradually works better than attempting long sessions.
The adaptation is real — people who sit regularly can hold positions comfortably that were painful initially.
Movement practices
Walking meditation exists in most traditions and produces comparable attentional training without any of the seated problems.
Which is underused, particularly by people who find sitting difficult and conclude they cannot practise.
Slow deliberate walking with attention to the sensation of stepping is the general form.
Sleepiness
Common in seated practice, particularly in a warm room after eating.
Which is addressed by posture, by opening the eyes slightly, by a cooler room and by timing.
Persistent overwhelming sleepiness during the day warrants considering whether sleep is adequate.
Eyes open or closed
Traditions differ, and both are legitimate.
Closed eyes reduce visual distraction and increase sleepiness.
Eyes softly open, directed downward, maintains alertness and orientation, and it suits people who find closing their eyes uncomfortable.
Hands and shoulders
Hands resting on the thighs or in the lap, supported rather than held.
Which prevents the shoulder tension that develops when arms are unsupported over a long period.
Cold and warmth
Body temperature falls during still practice, and being cold is distracting.
Which is why a blanket or extra layer is standard in traditions with long sitting periods.
Timing in the day
Practising when alert rather than when exhausted removes a substantial obstacle.
Which for most people means morning or a deliberate break rather than the end of the day.
Retreats and intensive practice
Extended periods of sitting carry higher physical demands and higher rates of reported difficulty.
Which is worth preparing for, and reputable retreat centres provide alternative postures and permit movement.
Anyone with an existing physical condition should discuss it with organisers in advance.