The use of speedsters in fiction requires
artistic license due to the laws of
physics that would prohibit such abilities. Moving at the
speed of sound, for example, would create
sonic booms that are usually not heard in such stories, and generate substantial heat. An enormous amount of energy would also be required to achieve such speeds, and speedsters would need to consume massive amounts of
calories to sustain their energy. The
Official Handbook of the Marvel Universe states that the character
Nova maintains speeds which can be considered "modest", especially when carrying a passenger. It also concedes that a solid object moving in the Earth's atmosphere at several times the speed of sound or faster would wreak havoc on the planet, and that moving at such speeds would prohibit
Northstar from breathing, while the generated wind/friction would ravage his body. On the other hand, it states that the character
Quicksilver was born with adaptations that make high speeds possible, such as enhanced
cardiovascular,
respiratory,
musculature, and
digestive systems, a more efficient
metabolism, better lubricated joints,
tendons with the
tensile strength of spring steel, unidentified bone composition that can withstand the dynamic shock of his feet touching the ground at speeds over 100 miles an hour, and a brain that can process information fast enough for him to react to his surroundings at high speed. Writer
John Byrne maintained modest abilities for the speedster character Danny Hilltop in his series
Next Men. Although Danny can keep pace with a race car, the friction generated by his speed melts any footwear he wears, burning his feet. As a result, Danny runs barefoot, having toughened the soles of his feet through a regimen of pounding increasingly harder materials.
Speed Force In
DC Comics, the
Flash family of speedsters derive their abilities from an
extradimensional energy source known as the Speed Force, which grants them superspeed and various other abilities required to use it, such as durability. The Speed Force is a cosmic force based around velocity and movement and is the in-universe representation of reality in motion, being the very cosmic force that pushes space and time forward. However, the Speed Force is not the source from which all DC characters with superspeed get their powers. For example,
Superman runs and flies quickly owing to his alien physiology, while
Captain Marvel/Shazam and
Wonder Woman are empowered by gods. Other writers choose not to offer any scientific explanations for the questions raised by the actual use of such abilities.
Peter David, whose run on the series
Young Justice included the junior speedster
Impulse, opined that speedsters are inherently difficult to write, stating, "Speedsters make me nervous, because if you play them accurately, they're impossible to beat... I could deal with Impulse because he was easily distracted." Additionally, there are alternative velocity-based power sources for speedsters: the Negative Speed Force was created by
Eobard Thawne to manipulate time as the Reverse-Flash and additionally corrupted
Fast Track as the Negative Flash, and the Forever Force has the power to manipulate time, which
Hunter Zolomon used to control the flow of time while appearing as the speedster Zoom. ==In other media==