What condition is caused by the excessive curvature of the lumbar spine?

The condition caused by excessive curvature of the lumbar spine is hyperlordosis. This condition is characterized by an exaggerated inward curve of the lower back, which can lead to discomfort and postural issues. In hyperlordosis, the alignment of the spine is affected, causing an imbalance that can result in strain on the muscles and ligaments surrounding the spine.

When examining the other options: kyphosis refers to an excessive curvature of the thoracic spine (the upper back), while scoliosis is characterized by a lateral curvature of the spine. Flat back syndrome is a condition where the natural curve of the lumbar spine is lost, leading to a more flattened spine. Each of these conditions represents a different spinal deformity that impacts the body's posture and alignment, but hyperlordosis specifically refers to the excessive curvature of the lumbar region, making it the correct answer in this context.