Modified running wheel system: towards improvement of measurements of voluntary running performance in mice

In this study, we present a modified running wheel system for assessing voluntary running in mice. The system employs a standard 14 cm running wheel mounted on the shaft of an incremental photoelectric rotary encoder, which generates 400 pulses per revolution and supports speeds exceeding 83 revolutions per second, well above the requirements of experiments involving voluntary wheel running in mice. Unlike commonly used devices, the proposed system enables, for the first time, a comprehensive set of measurements: quantification of the period and depth of running speed pulsations; identification of the true instantaneous maximum running speed; detection of short rest periods (∼1 s); detection of minor interactions with the wheel, such as entering or leaving without running; and determination of the dominant running direction (right/left). This approach allows more precise characterization of running behavior, including maximum and average speed, and captures additional features such as preferred running direction.