| strenuous(adjective, action, strong, tough, smart) |
| potent(adjective, strong, direct, sound, tough) |
| vital(adjective, good, clear, strong, tough) |
| fresh(adjective, person, tough, energy, keen) |
| enterprising(adjective, action, strong, tough, keen) |
| indefatigable(adjective, determined, active, full, forceful) |
| quick(adjective, pleasant, keen, sharp, intense) |
| tireless(adjective, determined, active, vigorous, full) |
| intense(adjective, strong, tough, severe, keen) |
| robust(adjective, strong, sound, tough, fit) |
| earnest(adjective, person, strong, enthusiastic, powerful) |
| keen(adjective, good, clear, strong, pleasant) |
| zippy(adjective, action, strong, moving, tough) |
| hearty(adjective, person, strong, sound, tough) |
| ambitious(adjective, work, ability, determined, success) |
| diligent(adjective, work, strong, keen, intense) |
| fervent(adjective, strong, powerful, lively, active) |
| passionate(adjective, strong, open, keen, intense) |
| snappy(adjective, action, strong, moving, tough) |
| unflagging(adjective, determined, active, vigorous, full) |