There are many strategies and the time commitment does not need to be large. Exercise snacks can build strength and they are just one set of an exercise to failure (such as a max set of pushups) 4 or 5 times throughout the entire day.

Here is a more comprehensive list of strategies to reduce exercise time:

https://medium.com/in-fitness-and-in-health/cant-find-time-to-exercise-here-are-some-ways-to-improve-exercise-efficiency-cfce8c8b2459