I've been strengthening you've been strengthening he's been strengthening we've been strengthening you've been strengthening they've been strengthening
I'll be strengthening you'll be strengthening he'll be strengthening we'll be strengthening you'll be strengthening they'll be strengthening
Futur antérieur
I'll have strengthened you'll have strengthened he'll have strengthened we'll have strengthened you'll have strengthened they'll have strengthened
Futur antérieur continu
I'll have been strengthening you'll have been strengthening he'll have been strengthening we'll have been strengthening you'll have been strengthening they'll have been strengthening
I'd be strengthening you'd be strengthening he'd be strengthening we'd be strengthening you'd be strengthening they'd be strengthening
Passé
I'd have strengthened you'd have strengthened he'd have strengthened we'd have strengthened you'd have strengthened they'd have strengthened
Passé continu
I'd have been strengthening you'd have been strengthening he'd have been strengthening we'd have been strengthening you'd have been strengthening they'd have been strengthening