Abstract: An object of the present invention is to provide a muscle fatigue recovery-promoting agent that can effectively promote the recovery of muscle fatigue, a method for producing a muscle fatigue recovery-promoting liquid, comprising the step of contacting the muscle fatigue recovery-promoting agent with a liquid, etc. In the present invention, ice (preferably CO2 hydrate) having a CO2-content rate of 3% by weight or more is used. The ice (preferably CO2 hydrate) having a CO2-content rate of 3% by weight or more or melted water thereof can be applied to the skin at the site of a targeted muscle to thereby promote the recovery of fatigue of the muscle.

Abstract: An object of the present invention is to provide an ultrafine bubble generating agent capable of easily generating ultrafine bubbles in a liquid without requiring an ultrafine-bubble generator, a method for producing an ultrafine bubble-containing liquid, an ultrafine bubble-containing liquid produced by the same production method, and the like. The method for producing an ultrafine bubble-containing liquid of the present invention comprises melting ice having a CO2-content rate of 3 wt % or more (preferably a CO2 hydrate).