You can pick out sinking hips in backstroke from the far end of the pool. The knees break the surface, the water line creeps toward the chest, and the swimmer ploughs along at an angle instead of lying flat. Coaches call it swimming in a chair: hips folded, thighs angled down, shins paddling under the body.
Backstroke was the second leg of every 200 individual medley I swam, including at two Olympic Games for Brazil, so I have spent a lot of time trying to stay flat on my back while tired. Sinking hips are almost never a strength problem. They are a position problem, and position changes fast.
Why do my hips sink in backstroke?
Because you are flexing at the hip, and three things make you do it: your head, your kick, and the way you rotate.
That is the whole mechanism: the angle between trunk and thighs closes, the thighs point down into the water, and from then on you are dragging a wall instead of a line.
What makes backstroke cruel is the lack of feedback. On your back you see a ceiling, so you can swim in a chair for years without knowing it.
Does body position matter more in backstroke than in freestyle?
On the evidence available, yes, because backstroke looks like the more resistive stroke before you add mistakes to it.
A systematic review of the determinants of backstroke performance summarises one included study of ten male swimmers swimming 50 m at four velocities in this shorthand: "Backstroke had 25% ↑ active drag at 1.2 m/s than front crawl". Ten swimmers is not a law of nature, but it matches what backstrokers feel: extra frontal area costs more here than on your front.
The front side version is why your legs sink when you swim, where the causes come in a different order.
Where should my head be, and where should I look?
Eyes up at the ceiling, the back of your head resting in the water, ears under the surface.
The fault I see most is the chin lifting toward the chest to look down the pool at your own feet. It feels like navigation. It is a pike: you fold at the neck, the chest rises, the hips drop behind it, and the chair appears. With the eye line up, the water crosses your head around the crown and the ears.
None of this was measured on backstroke, but the size of the effect is worth knowing. A study on the effect of the swimmer's head position on passive drag towed ten regional level swimmers face down at a constant depth of 60 cm and varied where they looked. Head down or aligned rather than head up cut average passive drag by 4 to 5.2% with the arms alongside the body, and by 10.4 to 10.9% with the arms extended overhead. It concludes that "The swimmer's head location seems to play an important role in reducing hydrodynamic resistance during gliding."
That was a towed glide on the front, so the numbers are not yours. What transfers is the mechanism behind head position in freestyle: the head is a heavy object on a long lever, and moving it moves everything behind it.
Is my kick pushing my hips down?
If you bend much at the knee, yes. A deep knee bend drives the thigh down, and the hip follows the thigh.
Swimmers resist this one, because the kick feels powerful when the knee works. From the side, the thigh is a paddle swinging down and forward, pushing your hip toward the bottom on every beat.
The review puts the comparison plainly: "Faster backstroke swimmers were characterized by a greater kicking frequency coupled with specific segmental differences related to a lower knee range of motion in the upkick and downkick positions". Faster swimmers kick more often and bend the knee less, which is the opposite of what a tired swimmer does.
So the kick starts at the hip, the knee stays soft but quiet, the toes just break the surface, and the water boils rather than splashes. A big white splash means the foot cleared the water, so the knee came up to put it there.
Should I roll, or does rolling drop my hips?
Roll. Rotation around the long axis and folding at the hip are different movements, and confusing them is why some swimmers swim backstroke flat as a board.
Body roll amplitude and timing in backstroke swimming measured ten male swimmers over four 50 m trials in both strokes, defining hip roll as "the angle between the projection of the line joining the left and right hip joint centres", which is rotation and not depth. It found that "Swimmers reduced the amplitude of rolls as the intensity increased in front crawl", while "they showed similar backstroke shoulder roll and hip roll amplitude at all trials".
The systematic review above states, without naming a stroke, that "when the velocity is increased there are corresponding decreases in body roll, shoulder roll, and hip roll". The two disagree, so how much roll a fast backstroker keeps is not settled. Neither suggests that rolling sinks you. Keep rotating so the shoulder can reach the catch, with the hips in the same horizontal line while they turn. That rotation also carries you into the backstroke flip turn, and makes backstroke a whole body skill, as in how to swim backstroke faster.
How does SwimRead read this part of your swimming?
It does not read backstroke, and I would rather tell you here than after you have filmed a length.
The SwimRead home page states that "The current beta supports freestyle filmed from the side of the pool", and that "Backstroke, breaststroke, butterfly, underwater footage, starts, and turns are not supported analysis modes in this beta." What it does cover is the same question on your front: "On-device pose detection estimates up to 33 body landmarks in sampled video frames", from a clip specified as "Aim for 10 seconds of continuous freestyle", filmed "in landscape from the side, with the whole body visible". You can set a training focus, and the page's own example is "Head position.", described as "Your choice, not a detected technique problem." The output is a measurement report and not a verdict: "These estimates are not validated technique grades."
For backstroke, do it yourself. Phone on the deck, landscape, from the side, looking at one line only: shoulder to hip to knee.
What should you drill this week?
- Eyes up, forehead dry. Four easy lengths with your eye line fixed straight up, someone on deck watching for your forehead breaking the surface.
- Kick with hands at your sides. Six by 25 m, toes just breaking the surface, counting beats to keep the rate up rather than the knee deep.
- Kickboard over the hips. Backstroke kick holding a board flat above your hip bones. If your knees hit it, the knee is doing the kicking.
- Six kicks and roll. Six beats on your side, six on your back, then the other side, hips staying at the same depth throughout.
- Film one length. From the side at the deep end, then watch the shoulder, hip and knee line.
My free swim pace calculator turns those 25s into a pace, so you can check whether the flatter position is faster.
SwimRead is free while in beta, and invitations go out as beta spots open, with paid plans coming later and beta testers told before anything changes. If you want a reading of your freestyle, join the beta and leave your email.