PULLUP

Pullup, commonly written as pull-up, is a term used in fitness and electronics to describe a method of lifting or biasing a signal. In fitness, the pull-up is a bodyweight exercise performed on a fixed bar in which the practitioner grips the bar and pulls the torso upward until the chin clears the bar. It is a compound movement that targets the upper back, shoulders, and arms, notably the latissimus dorsi, biceps, trapezius, and rhomboids. Variations include grip type (pronated, supinated, or neutral) and width, which influence muscle emphasis. Common training progressions start with assisted or negative repetitions and gradually increase volume or switch to easier leverage to build the necessary strength and control. Proper form emphasizes a controlled ascent and descent and minimal kipping unless training for specific athletic goals.

In electronics, pull-up refers to a pull-up resistor that ties a signal line to a positive supply voltage to ensure a known high logic level when no active driver is pulling the line low. This is essential for open-collector or open-drain outputs, microcontroller inputs, and some bus interfaces. The resistor value is selected to balance power consumption with reliable logic level, typically ranging from about 1 kΩ to 100 kΩ depending on supply, leakage currents, and desired speed. Pull-ups are often contrasted with pull-down resistors, which bias lines toward low when undriven.

Some other uses of the term exist in computing and electronics, including biasing schemes in interfaces and historic references to lifting or resetting signals, but the main meanings are the exercise and the electronic resistor.