Surgical management of spasticity is a challenging problem. Part of the difficulty is the lack of information regarding the properties of the spastic muscles themselves. While clinical impression is that spastic muscle is somewhat stiffer than normal, there are no objective data regarding the mechanical properties of spastic muscle cells themselves. Thus, the mechanical properties of isolated single muscle cells were measured on muscle cells obtained from patients undergoing surgery for correction of spastic flexion contractures secondary to cerebral palsy. “Normal” muscle cells from patients with intact neuromuscular function were also mechanically tested. The most dramatic effect observed between cell types, was the consistent and relatively large resting sarcomere length difference between groups. While normal fibers had a resting sarcomere length of 2.20±0.04 µm (n=35), spastic fibers were about 20% shorter with an average resting sarcomere length of only 1.84±0.05 µm (n=15). Tangent modulus of the sarcomere length-stress relationship in spastic fibers (55.00±6.61 kPa) was almost double that measured in normal fibers (28.25±3.31 kPa). Myosin heavy chain composition in spastic muscle fibers did not show a shift toward the type 1 isoform which would be expected if spasticity represented an increased muscle use model such as that observed after chronic electrical stimulation. In addition, the fact that spastic muscle cells have a shorter resting sarcomere length and increased modulus suggests dramatic remodeling of muscle structural components