The general recommendation for cardio for heart health is 30 minutes, 5 times per week. I would try to work up to this.

https://www.hopkinsmedicine.org/health/wellness-and-prevention/3-kinds-of-exercise-that-boost-heart-health#:~:text=How%20much%3A%20Ideally%2C%20at%20least,per%20week%20of%20moderate%20activity.

You should do body weight interval training to start and work up to weights. More bang for your workout investment for short period of time.

Thank you. Yes probably I should do slightly longer workouts less often. I will try that!

My objective is to maintain or improve my cardio fitness over time, with the minimal exercise time and frequency. Cycling suits me. It seems intense enough to be effective.

It’s a fine place to start, but that certainly shouldn’t be the goal.

OP, what are your goals? Are they to improve your fitness and cardiovascular health? You can't spot-lose weight, and your weight is completely fine. You should exercise for other reasons - mental and physical health, strength, endurance, etc. And yes for those things, you're better off doing 20-30 minutes 4 days a week than 10 mins daily.

I am 46, 5’7” and 136 lbs. I am slim, although I have some belly fat due to my pregnancies and age.

I am trying to get more fit after a long hiatus. I am doing 10 minutes Apple fitness cycling workouts almost daily. Is that enough cardio? My resting heart rate is around 53 and gets up to 150+ during the cycling workout.

I know I want to start doing some strength training and I don’t have much time so I would like to keep my exercise routine as short as possible, while still being effective. Maybe I could do one or two 20 minutes cycling workouts during the weekend.