Short of time to train?
Try Tabata workouts....
They are High Intensity Interval workouts that last 4 minutes.
Work hard for 20 seconds and rest for 10 seconds until you complete eight sets.
You can use resistance exercises or cardio with this approach.
An exercise that works your large muscle groups is good.
After your 8 work periods, rest for 1 minute before beginning the next.
Sprints: Remember 20 secs hard, 10 secs rest and repeat x 8.
Hold the correct posture, with eyes up, chest tall, shoulders relaxed, and arms moving like pistons (with the elbows at 45-degree angles).
Press-ups: Get into a fully extended arm plank position with hands positioned a little bit wider than shoulder width apart. Keep the elbows as close as you can to the body throughout the movement. Stabilise yourself by pushing the toes into the floor and engage the core muscles so the body is neutral. Lower the body in one straight line until the chest touches the floor. Keeping your core muscles engaged, exhale, and push back to the start position. 20 secs on, 10 secs off x 8
Have a go -it's tough but it's a time efficient way to train and can improve your endurance over time...