Use of a carbon dioxide-supplying means for muscle strengthening makes it possible conveniently to strengthen a target muscle within a short period of time merely by allowing the target site to absorb carbon dioxide without loading any mechanical burden on the target muscle. By loading a mechanical burden on the target muscle, the muscle strengthening effect can be further enhanced and an additional effect of promoting the recovery from muscle fatigue can be achieved owing to the mechanical burden. By using the carbon dioxide-supplying means for muscle strengthening as described above, it is also possible to increase cattle meat.
