AIBU to ask the best way to quickly improve my cardio?

[Liveonyournerves]

I did a lot of classes with HITT and strength interspersed before lockdown. Since then, I've done online classes where the main focus is strength/weights etc. I feel my cardio has declined and want to get it back.

What's the quickest and most effective way/exercise to do this?

What kind strength/weights workouts are you doing? I do interval training with weights in the gym so there's cardio there without hours of purely cardio work and they advocate building a daily walk into your routine.

Intervals, speed-based ones. So if you run, hill sprints; or on the rower/skierg, 30 seconds as fast as possible then 1m rest, x 5. Or google met con workouts. Basically, working as hard as possible for a short period & getting your heart rate up; fully recovering & bringing heart rate back to normal; then going again...

Depends what sort of 'cardio' you mean. Anything where you are getting out of breath is cardio, but if you specifically want to improve cardio fitness then while any cardio will help, you need to pick what to focus on. HIIT is the most time efficient and has some added metabolic benefits. Superset/interval strength training won't get your heart rate up as much but has added muscle benefits. Steady state cardio such as running burns the most calories but takes longer. A combo of all three is the best way to achieve all-round health and balanced fitness.