I teach Nia which is a cardio-dance type workout and I say cardio-dance “type” because it is a cardio workout that we do to music. Yet, it also allows the opportunity for strengthening of the muscles, increasing flexibility, improving stability and agility, and boosting mobility. All of this could happen without you even realizing it because it is all done to music in a type of dance. Or you could actually try to improve your abilities in progression. In other fitness modalities they call it progressive overload. You can actually decide to increase your abilities and work towards that.
Progressive overload is increasing the challenge in increments so that the body keeps adjusting accordingly to the new stress. As long as the body perceives it as new the system will continue to adjust. The challenge in Nia could be a variety of things; you could put your arms up higher to give you greater mobility in your shoulders, you could move them faster to increase your agility, or you could do all of this continually to increase your cardio vascular health. There is always an occasion in a routine where you can bend deeper which could strengthen the lower body and again this is a way to raise your heart rate especially if you do it at a great speed.
If you are doing something other than Nia the changes could be another wide variety of things; actually changing the exercise you are doing, doing exercises longer, doing more during a workout session, or increasing the amount of workout sessions. If using resistance increasing the resistance would be considered an overload. Whatever you want to improve you would increase the challenge in increments giving the body something new to learn and overcome.