It is exercise alone that supports the spirits, and keeps the mind in vigor.

Cicero’s line links bodily activity with mental resilience: “spirits” (mood, morale, vitality) are sustained not by passive comfort but by exertion, and the mind remains “in vigor” when it is regularly stirred and strengthened. Read broadly, the remark reflects a classical ideal of balance—health of body and health of intellect as mutually reinforcing—while also carrying a practical, almost therapeutic claim: movement combats languor, melancholy, and mental dullness. The emphasis on “alone” heightens the point into a maxim, suggesting that without habitual exercise, both emotional steadiness and intellectual sharpness tend to decline.