Flat back posture: a flatter lower back, flatback syndrome and what exercise can change

A common shape

Flat-back posture means a flatter lower-back curve, with the pelvis level or tipped back. Healthy curves vary widely, and a flatter one is one of the normal shapes.

Sources 1, 2, 3

Only a weak link with back pain

On X-rays, people with back pain have slightly flatter curves on average, and a flatter curve went with a modestly higher chance of later back pain in 3 studies. Neither shows the shape causes pain, and a review of 54 studies found no strong link between spinal curves and health.

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A scan report describes the image

'Loss of lumbar lordosis' means the curve looked flatter than average on that image, often taken lying down. On its own it doesn't tell you the cause or mean damage.

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Flatback syndrome is different

It's a fixed, stooped posture from a flattened lower spine, usually after spinal surgery or with wear, and it needs a spinal specialist.

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Exercise builds strength; the curve may change a little

In one small trial of 36 women, allocated by order of enrolment rather than at random and not followed up, exercise deepened the curve by about 4 to 7 degrees over 12 weeks. Stretching doesn't change spinal posture. Back, hip and core work builds strength and comfort whatever the angle.

Sources 11, 12

Flat-back posture

A flatter lower-back curve, often with a flatter upper back too, and the pelvis level or tipped back. It's one of the classic posture types, alongside a deep curve (lordotic posture) and sway-back. The medical word for a flatter curve is hypolordosis.

Source 1

The muscle charts are theoryEmerging evidence

Posture charts list which muscles are 'short' or 'weak' in flat-back posture, for example 'shortened yet hyperactive' hamstrings, but these come from clinical experience. When muscles were measured, hamstring length was only weakly linked with the lower-back curve, and men with short hamstrings stood like men with long ones.

Sources 1, 13, 14

Flat back or sway-back?

In flat-back posture the body is stacked fairly straight. In sway-back posture the hips sit forward of the ankles and the upper body leans back, with a long rounded upper back and a short, often flatter lower curve. The swayback guide covers that posture.

Source 1

A wide normal rangeStrong evidence

On standing X-rays of 468 adults aged 18 to 80 without back problems, the lower-back curve averaged 57 degrees, give or take 11. In 300 adults it averaged 60, give or take 10, so most healthy people fall somewhere between about 40 and 80 degrees.

Sources 2, 15

The pelvis sets part of itEmerging evidence

The shape of the pelvis, a fixed bone angle called pelvic incidence, partly sets the size of the curve (a correlation of 0.53 in the 468 adults). In 160 volunteers, the lower back took four common normal shapes, set largely by the slope of the top of the sacrum.

Sources 2, 3

Age and sexMixed evidence

A meta-analysis of 35,913 volunteers found the curve flatter in older age groups and the pelvis tipped back further after 60, while the 468-person study found no change in the curve with age. Women tend to have larger curves than men.

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SittingStrong evidence

Sitting flattens everyone's lower back while they sit: by about half in 50 healthy adults, and from 49 to 34 degrees in 109 people with back pain.

Sources 17, 18

ChildrenEmerging evidence

Spinal curves change as children grow, and growth spurts change them differently in girls and boys. In 656 children and teenagers, pelvic incidence, which helps set the curve, averaged about 34 degrees in younger children and 43 in teenagers. In 639 boys around 12, 42% stood in a neutral way, 31% in sway-back and 27% leaning forward. A flat-looking back in a child without pain or stiffness needs nothing.

Sources 19, 20, 21

What the phrase means

Reports say 'loss' or 'straightening' of the lumbar lordosis when the lower-back curve looks flatter than average on that image. Flatter curves are a little more common in people with back pain, but the phrase on its own doesn't tell you the cause or mean damage. Ask your GP what it means for you.

Sources 4, 7

Lying down and standingEmerging evidence

Magnetic resonance imaging (MRI) scans are usually done lying down. In 63 people, the whole lower-back curve on MRI was within about 3 degrees of a standing X-ray on average, though single levels differed more, and lying with straight legs reproduced the standing curve to within a median of 3 degrees in 22 people.

In 38 people with back pain, the curve was about 6 degrees flatter than in 38 people without, both lying and standing, and it changed by the same amount between the two positions.

Sources 8, 22, 7

Flat curves and back painMixed evidence

Across 13 X-ray studies (796 people with back pain and 927 without), people with back pain had slightly flatter curves, with a bigger difference in those with disc problems, though the studies varied a lot. In 3 studies that followed 1,657 mostly young people, a flatter curve went with about 37% higher odds of later back pain, but the result was close to no effect and each study measured differently. A review of more than 120 studies called the evidence on lordosis and back pain inconclusive.

Sources 4, 5, 23

Spinal curves and healthStrong evidence

A review of 54 studies, mostly of low quality, found no strong evidence linking the spine's front-to-back curves with spinal pain or any other health outcome. An umbrella review of 41 reviews found no agreement that spinal posture causes back pain.

Sources 6, 24

Back-muscle enduranceEmerging evidence

In 600 adults, the size of the lower-back curve wasn't linked to back pain, while the endurance of the back muscles was the factor most linked to it. The study looked at one point in time, so it can't show cause.

Source 25

Exercise and a flat curve: one small trialEmerging evidence

36 women with flexible flat back and back pain that hadn't improved for 3 months were allocated by the order they enrolled, not at random, to 12 weeks of exercise (60 minutes, 3 times a week) or to physiotherapy with heat, ultrasound and electrical current treatments. Corrective exercise based on Schroth methods deepened the curve from about 33 to 40 degrees and lowered disability scores from 25 to 15 out of 100. Resistance training deepened it from about 33.5 to 37 degrees and lowered disability from 24 to 21. Physiotherapy alone changed neither.

The curve was measured from the first to the fifth lumbar vertebra, so these numbers can't be compared with the normal values above, and nobody was followed up after the 12 weeks.

Source 11

Exercise moved curves towards the middleEmerging evidence

In 12 women with flat or deep lower-back curves, a 12-week exercise programme moved both groups towards the middle of the range. The authors noted that exercise can raise strain on the tissues of the back as well as lower it.

Source 26

Stretching and postureStrong evidence

Across 23 studies in healthy people, stretching didn't change spinal or pelvic posture, and strengthening didn't significantly change the lower back and pelvis.

Source 12

What it is

The Scoliosis Research Society defines it as 'forward posture usually due to a flattened lumbar spine from postoperative or degenerative changes', in which the head may be several centimetres in front of the hips. To stand upright, a person 'must contract the back muscles, and possibly flex at the hips and knees', which can lead to severe pain over time.

Sources 9, 27

CausesStrong evidence

Disc degeneration, compression fractures, ankylosing spondylitis, and a laminectomy or spinal fusion that doesn't keep the lower back's curve. After a fusion, the spine at first makes up for it with more curve at the neighbouring levels and less rounding of the upper back; as the back muscles tire, the pelvis tips back and the hips extend to keep the body balanced.

Sources 27, 10

TreatmentEmerging evidence

Many people are treated without surgery at first, with physiotherapy including walking and posture training, exercise and pain medicines. A review says non-surgical care 'is frequently unsuccessful' once the imbalance is large (the spine more than 5 cm in front of the pelvis), and that surgery to restore the curve can improve quality of life despite significant complication rates.

Use the exercises on this page for flatback syndrome only if your surgical team agrees (our editorial advice).

Sources 27, 10

A starting programme

Two or three sessions a week of the 20-minute routine below (our editorial starting point). The flat back trial used 60-minute sessions 3 times a week for 12 weeks, and the NHS asks adults to do muscle-strengthening activity on at least 2 days a week.

Sources 11, 28

Back extension

Our editorial starting points, matching the swayback guide: sphinx, 30 to 60 seconds, 3 times; low cobra, 8 slow lifts with 3 breaths at the top; locust, 3 to 5 holds of 10 to 20 seconds. The prone back raise has a move page dose: 2 to 3 sets of 10 to 15 slow reps, stopping with 2 or 3 reps in reserve. The prone press-up's page dose (10 slow repetitions, 3 to 5 times a day, while it helps) is for people whose back is comfortable arching.

Source 25

Hinge, glutes and trunk

Hip hinges, 2 sets of 8 to 10, then kettlebell deadlifts, 2 to 3 sets of 8 to 10; bridges, 2 to 3 sets of 10 to 12; bird dogs, 2 to 3 sets of 6 to 8 each side (our editorial starting points).

Sitting

Sitting flattens everyone's lower back, and a review of 24 studies found strong evidence that sitting at work isn't linked to back pain. The authors of the 109-patient X-ray study suggested that a lumbar support that increases the curve may help when you sit; that's their discussion, not a trial, so treat it as a comfort choice.

Sources 18, 17, 29

Hamstrings

Stretch your hamstrings for comfort or to bend further, not to change your curve: standing posture didn't differ with hamstring length, and stretching doesn't change posture.

Sources 14, 12

Call 999 or go to A&E

Posture exercises are not where to start if you have back pain with any of these. In the US, call 911.

• Pain, tingling, weakness or numbness in both legs.
• Loss of feeling around your genitals or anus.
• Changes in your bladder or bowels, such as difficulty peeing, or peeing or pooing yourself.
• Changes in how your penis or vagina feels during sex, not being able to get or keep an erection, or not being able to orgasm.
• Chest pain.
• Back pain that started after a serious accident, such as a car crash.

Source 30

Get an urgent GP appointment or call 111

If you have back pain and:

• You feel hot, cold, shivery or generally unwell.
• The pain is severe, started suddenly or is getting worse quickly.

Source 30

See a GP

If back pain:

• Doesn't improve after a few weeks of looking after it at home, stops you doing day-to-day activities, or worries you.
• Comes with weight loss you can't explain, a lump or swelling in your back, or a change in the shape of your back.
• Doesn't improve with rest, is worse at night, or is worse when you sneeze, cough or poo.
• Is coming from the top of your back (between your shoulders), rather than your lower back.

Source 30

Trouble standing upright

Needing to bend your knees to stand upright, leaning further forward as the day goes on, or a stoop that is new or getting worse can be flatback syndrome, above all after spinal surgery. See a GP, who can refer you to a spinal specialist.

Sources 9, 27

Stiffness that's worse in the morning

Back pain and stiffness that get better with exercise but not with rest, are worse in the morning and at night, or come with pain around your buttocks, especially if they started in your teens or as a young adult, can be ankylosing spondylitis. See a GP, who can refer you to a rheumatologist.

Sources 31, 32

Children

A child's flat-looking back needs nothing on its own. See a GP for back pain that keeps going, or stiffness that's getting worse (our editorial advice).

"A flat back is always bad for you."Mixed evidence

Healthy curves vary widely, and a flatter one is one of the normal shapes. Flatter curves go with back pain a little more often, but that doesn't show the shape causes it, and reviews find no strong link between spinal curves and health.

Sources 2, 3, 4, 6

"Stretch your hamstrings to get your curve back."Strong evidence

Standing posture didn't differ with hamstring length, hamstring length was only weakly linked with the curve, and stretching doesn't change spinal posture.

Sources 14, 13, 12

"'Loss of lordosis' on my scan means damage."Emerging evidence

It describes the curve on that image, often taken lying down. People with back pain were only about 6 degrees flatter than people without, so the phrase isn't specific.

Sources 7, 8

"Posture exercises fix flatback syndrome."Emerging evidence

Physiotherapy is often tried first, but a review says non-surgical care is frequently unsuccessful once the imbalance is large. It needs a spinal specialist.

Sources 10, 27