Sitting furniture (100;200;300) comprising a seat (110;210;310;510), a lower leg support (120;220;320) and a chest support (130;230;330), wherein the seat (110;210;310;510) is arranged to support the posterior thigh and/or buttocks of a seated user such that the femur bone of the seated user is downwards inclined in the anterior direction at an angle of at least 40° downwards in relation to the horizontal, wherein the lower leg support (120;220;320) is arranged to support the anterior side of the lower legs of the seated user, and wherein the chest support (130;230;330) is arranged to support the chest of the seated user in a forward leaning position of the seated user, wherein the sitting furniture (100;200;300) does not include a head support, and the lower leg support (120,220,320) is arranged in such a way so that the lower legs of the seated user are oriented so that the tibia of the seated user is inclined between 0° and 10° upwards from the knee of the seated user, in relation to the horizontal, and in said forward leaning position, the third lumbar vertebrae body of the seated user is arranged in a support plane (150;250;350), which support plane (150;250;350) is perpendicular to the sagittal plane of the user and inclined between 65° and 85° in relation to the horizontal, wherein due to a combination of the position and angle of the seated user's femur bone and a location of a chest support (130,230,330) point the respective pivot point of the seated user's hip joints and the respective pivot point of the seated user's shoulder joints are also arranged in said support plane (150;250;350) when the posture of the seated user is symmetric about the seated user's sagittal plane. the seat (110;210;310;510) is arranged to support the posterior thigh and/or buttocks of a seated user such that the femur bone of the seated user is downwards inclined in the anterior direction at an angle of at least 40° downwards in relation to the horizontal, wherein the lower leg support (120;220;320) is arranged to support the anterior side of the lower legs of the seated user, and wherein the chest support (130;230;330) is arranged to support the chest of the seated user in a forward leaning position of the seated user, wherein the sitting furniture (100;200;300) does not include a head support, and the lower leg support (120,220,320) is arranged in such a way so that the lower legs of the seated user are oriented so that the tibia of the seated user is inclined between 0° and 10° upwards from the knee of the seated user, in relation to the horizontal, and in said forward leaning position, the third lumbar vertebrae body of the seated user is arranged in a support plane (150;250;350), which support plane (150;250;350) is perpendicular to the sagittal plane of the user and inclined between 65° and 85° in relation to the horizontal, wherein due to a combination of the position and angle of the seated user's femur bone and a location of a chest support (130,230,330) point the respective pivot point of the seated user's hip joints and the respective pivot point of the seated user's shoulder joints are also arranged in said support plane (150;250;350) when the posture of the seated user is symmetric about the seated user's sagittal plane.