One of the best ways to get more out of your training is to do intervals. This means short bursts out of your comfort zone followed by active rest periods. Here is the good news. It doesn’t have to be sprints. It simply can be any cardio activity that pushes your comfort zone.
A study from McMaster University showed that even 1min of vigorous training can increase fitness.
In the study, one group of people rode 45min at a moderate pace three times per week. The other group did an interval protocol of 2min warming up followed by three cycles of 20s sprints and 2min moderate paddling on a stationary bike.
After 12 weeks both groups increased their exercise capacity (they got fitter) by 19%. But with the difference of three times 10min vs three times 45min of training.
So mixing moderate cardio training with interval training is a great idea to get all the benefits for your fitness. you can do moderate cardio 30-40min a day and mix it up with intervals 2-3 times per week.