Same word as vigor:

ability, action, activity, agility, alertness, bang, birr, bounce, capability, capacity, dash, drive, dynamism, endurance, enterprise, exercise, fire, force, get-up-and-go, go, hardiness, healthiness, intensity, juice, kick, liveliness, lustiness, might, motion, moxie, muscle, nimbleness, pep, pith, potency, puissance, punch, push, quickness, snap, sock, soundness, starch, steam, strength, tuck, urgency, vehemence, vim, vitality, well-being, zing, zip