AtaXia, Sadler's Wells London

The choreographer Wayne McGregor goes in for the illegible. His titles are typographical nightmares, strewn with brackets and random capital letters. The dancing is just as hard to read, steps thrown together in a frantic clutter.

The choreographer Wayne McGregor goes in for the illegible. His titles are typographical nightmares, strewn with brackets and random capital letters. The dancing is just as hard to read, steps thrown together in a frantic clutter.

This time, he uses the neurological disease ataxia as a starting-point. There's something queasy about watching dancers, with their trained bodies, imitate an illness in which physical control is lost. But their twitches aren't a departure for McGregor. His choreography depends on exhausted fidgets.

McGregor's dances do have an aggressive speed. He's in demand as a choreographer, with commissions from Rambert and the Royal and English National Ballets. Most recently, he was appointed research fellow in the department of neuroscience at Cambridge. AtaXia is the result of his work on neurological breakdown.

Back on stage with McGregor's company, Random Dance, AtaXia is deliberately disorienting. McGregor and his lighting designer, Lucy Carter, surround the dancers with dim light and faint reflections. There are flickers from film sequences and strobe lights. Movement is reflected in Perspex panels and the dark, shiny backdrop. Ursula Bombshell's costumes, shorts and shift tops, have luminous patches. When the lights go out, we can see glowing shapes that don't quite resolve themselves into bodies.

The music, shriekingly amplified, is played live by the group Icebreaker. Michael Gordon's score is a minimalist thrash of shrill flutes and wheezing saxophones. When Gordon adds a thumping beat, it becomes a random layer of extra noise. The dancers pay no attention to any of it.

The unreadable quality of McGregor's choreography comes from his limited rhythm. His steps are shapeless, because there's nothing to weight one movement over another. The dancers wallop themselves from one extreme to another, or slip back into fast twitches, but we don't see the difference.

McGregor likes extreme positions, but they're extremes without drama. His dancers will grab an ankle - their own, or someone else's - and yank the leg skyward. You notice the strain more than the position, because the pose is never given space to register.

I'd guess that the repeated falls are references to neurological disorder. The shaking limbs, too, but it's hard to tell. Fussy dislocations are part of McGregor's style. It's all the same slurred, chattering flow.

The Random dancers are admirably fast and strong, but they can't avoid a sense of strain. The dancers do everything at wrenching speed, but they have no time to make sense of it. Or for us to make sense of them. The central duet is danced by Laila Diallo and Khamlane Halsackda. They're both fine dancers, and Diallo's line could be lyrically beautiful. She hardly gets to show it. Even the slow movements are airless with lack of contrast.