They had the subjects perform an isocaloric (400 kcal) cycle ergometer exercise

For anyone who needs that unwound a bit, 'isocaloric' means equal quantities of carbs, fats, and proteins. A 'cycle ergometer' is an instrumented exercise bicycle. (I missed the 'cycle', thought maybe it was a rower as those are commonly called ergometers or ‘ergs’). Here’s an image of the model they seem to have used