A sophont who chooses to incorporate Ultimate Muscles into eir body may significantly change in appearance
Ultimate muscle is nanostructured electromechanical motor material, made primarily of carbon, boron, and nitrogen. In appearance, it is a dull black, and typically formed into threads, cables, sheets, or cylinders. Upon application of a voltage, the ultimate muscle will either contract or expand, depending on the variety (some ultimate muscle types only contract under voltage, some expand, and some can do either). The pressure or tension of ultimate muscle is near the limit of the strength of chemical bonds, commonly exceeding 20 GPa. Since ultimate muscle can exceed the yield strength of many common structural materials, machines made from ultimate muscle can push or rip through steel, rock, concrete, and sapphiroid. High strength carbon and carbon/nitrogen/boron materials can typically resist direct pressure from ultimate muscle, but suitable concentration of force often allows these materials to be defeated.
Ultimate muscle was first invented by the transapient known as Abreps the Engineer (then at S3). The simplicity of the design has been remarked on by many transapients, and once the trick is known, ultimate muscle can be built and designed by transapients as low as S1. Modosophonts can produce ultimate muscle given blueprints for its nanofacture, but fail to understand its method of operation.
Several advanced forms of cyborg have varying amounts of Ultimate Muscle incorporated into their structure; in particular the cyborgs known as Supersophonts include quite significant a Ultimate Muscle content in their design.
Ultimate muscle machines of S2 and above often have a dynamic structure, being made of linked microscale ultimate muscle fibers that can quickly reconfigure themselves to any desired shape. The muscle material of these dynamic machines can often reconfigure itself to take on load-bearing properties instead of force generating properties, allowing on-the-fly creation of ultra-strong "bones". The resulting vecs often appear as amorphous blobs, but many varieties can rapidly take on any shape consistent with their mass and a density of no more than 2.7 g/cm^3.
Comparison with biological muscle
Biological muscle can exert a maximum of about 0.4 MPa under optimal conditions. Compared to the 20 GPa of Ultimate Muscle, an Ultimate Muscle user might be expected to be 50,000 times stronger than an equivalently shaped human. However, this is somewhat misleading - Ultimate Muscle can exert pressures close to the yield strength of the strongest materials (about 40 to 50 GPa). Compare this to the pressure of muscle (less than 0.4 MPa) and the tensile strength of tendon (about 50 MPa), and it can be shown that the ultimate muscle user would need disproportionately thicker tendons and bones in proportion to its muscles, even though those bones and tendons consist of the strongest physical materials (in most cases some form of diamondoid or hardened Ultimate Muscle material).
In practice a vec or cyborg using Ultimate Muscles would be 10,000 times stronger than a similarly shaped biont. If a human in good shape can lift 100 kg over his head in one earth standard gravity, an equivalent sized U-muscle vec would be able to lift 1,000 tons. However this would exceed the structural strength of most 1,000 ton objects, and the weight would crack. Also, this requires proper positioning and leverage, or the U-muscle user would just lift a corner.
When jumping, the legs to work on the body equal to the force exerted times the distance over which the force is exerted. Since the U-muscle user would be exerting about 10,000 times the force over about the same distance, it would do 10,000 times the work. The work done by the muscles becomes kinetic energy. As the jumper's body rises, the kinetic energy becomes potential energy. Potential energy increases linearly with height, so since the U-muscle user can do 10,000 times as much work, it can jump 10,000 times as high. Similarly, it can also jump 10,000 times as far. This analysis neglects aerodynamic drag, which would significantly reduce this distance. Since very athletic bionts can jump several meters high, a U-muscle user would be able to reach altitudes of tens of kilometres in vacuum under one standard earth gravity.
If a sophont attempts to run very fast, the limitations of gravity start to become apparent. The runner's legs may move very fast, but gravity is too slow to pull the feet back into contact with the ground. As anyone who has attempted to run on a low gravity world can attest, the fastest method of locomotion where the acceleration due to gravity is weak is a series of lopes or bunny hops; this also applies to a fast moving sophont using Ultimate Muscles, and this form of locomotion can be considered as a series of low jumps.
The kinetic energy of a body is proportional to the square of its velocity, so the running speed will be proportional to the square root of the work per leg stroke. Thus, a U-muscle user should be able to run at about 100 times faster than an equivalent biont. Top human athletes can run at 10 m/s. The U-muscle user might be expected to be able to run at about 1 km/s. Again, this neglects aerodynamic drag, the mass of the sophont's body and damage to the ground surface, but it can be seen that a fairly light-weight U-muscle user could run at several hundred metres per second, about as fast as a high power bullet.
Because Ultimate Muscles use so much power, they create a lot of waste heat; without very efficient cooling systems, an Ultimate Muscle user can only operate at full power for about 6 seconds.