At the very heart of modern art is a preoccupation with energy: the attempt to create an aesthetic which, brought about by changes in manufacturing, technology and transportation, captured the new, fast pace of the times. While Picasso experimented with the breakdown of form in cubism, and Matisse brought colour to life in Fauvism, Auguste Rodin’s art drew inspiration from elsewhere: the movement of the human body through dance.

It was after his death in 1917 that a collection of small sculptures, each around 30cm in height, were first discovered in Rodin’s studio. Named the ‘Dance Movements’, the sculptures show figures that twist, leap and stretch in a variety of poses both elegant and supple. The fact that they were created for personal pleasure not intended for public exhibition in itself makes them interesting; they’re private artefacts, providing insight into the ideas that both stimulated and challenged Rodin and his art towards the end of his life.

Some critics might joke that these sculptures amount to an ageing man’s soft porn collection: as one sculpture showers the dancer balanced on leg with the other touching the back of her tilted-back head, no angle of the body is left to the imagination. That aside, the sculptures and accompanying sketches convey a very passionate attempt to convey the fleeting, spontaneous image of movement. ‘This is the revelation of the great mystery’, Rodin wrote: ‘how to express movement in something that is at rest.’

Whereas Edgar Degas’s dance paintings depicted classical ballet dancers, Rodin was drawn to freer, wilder forms. This is reflected in the organic, almost spontaneous appearance of his sculptures, which are less interested in anatomical specifics than communicating a sense of motion. And yet his assertion that it was ‘all mathematics’ suggest his strong attentiveness to proportion, placement and orientation. He requested his mould-maker to create a series of body parts – limbs, heads and torsos – which he could reassemble in his own way, taking pure delight in choreographing their shapes.

His principal muse – whose body becomes somewhat recognisable after a tour of the various sketches and sculptures that make up the exhibition – was Alda Moreno, a performer at the Opéra Comique. Upon seeing photos of her, Rodin scheduled a meeting and asked her to model for him, which she did for three years. Her sittings provided the inspiration for 56 line drawings, from which Rodin’s fascination with the possibilities of human form grew.

The models of his sketches also include the Royal Cambodian dancing troupe that toured France in 1906, performing the ceremonial ballet of King Sisowath. The delicacy of their poses, the movement of their hands and bodies, is caught on paper with a light-handed and yet evocative minimalism. Many of his rapid pencil sketches were composed by keeping his gaze fixed on the dancer, without looking down at the drawing.

The emergence of less decorative, more visceral ballet dancers such as Isadora Duncan and Vaslav Nijinsky also excited Rodin. His sculptural depiction of the latter, with his thigh bent up towards his hunched torso, is an image of radical physical potential. It’s a very striking suggestion of both the liberating impact and implications these new forms of dance were about to unleash on society.

As a sculptor famed for such bold, solid works as The Walking Man (1888-89), The Kiss (1889) and The Thinker (1902), these sculptures have a fragile sensuality about them. But while they might be smaller in scaler, they’re not so in vision. Erotic, provocative and highly experimental, they show us how Rodin’s imagination still burned with a creative, modern capacity at the end of his life. A hundred years after his death, and these works still dance.