Right, it's not mentioned what that is in the article.

On first search, something you do with your horse. I don't have a horse.

This site says

Combination Training is an integrated form of training that combines lower body, upper body, trunk musculature and balance training all into one exercise, accomplishing three times as much training in the same amount of time.

https://nwpersonaltraining.com/blog/combination-training/

I think something like those Billy Blanks Tae Bo videos would fit the bill.

BBC thinks it is "aerobic and weights"