Does Cardio Lose Effectiveness Over Time?
Cardio is sometimes said to “lose effectiveness — you burn fewer calories the more you do it.” It is true that you become more efficient the more cardio you do, and that is a good thing.
If your cardio regimen is “2 miles on the treadmill in 25 minutes,” and you do that every day, your body will become more efficient at doing that (your heart rate will drop, and you will burn fewer calories, as your body gets better at doing 2 miles in 25 minutes). That’s why we set new goals every once in a while — when you can easily do 2 miles in 25 minutes, you see if you can do 2.2 miles in 25 minutes, or you go for 3 miles in 35 minutes. Or some other modification.
This is adaptation, and it’s the sign of a good exercise program: as you develop your cardio conditioning, you become able to go longer and faster, and to do a wider variety of workouts. Regular exercise has many health benefits, too, including regulating sleep and mood — it’s not all about performance and calories. (And even sprinters also continue to do some slow and easy workouts; a good exercise program has variety.)
Same thing with lifting weights: you’d never just choose a weight and a number of reps and sets and do the same thing every single time you went to the gym. You’d start with a comfortable weight, do some number of reps and sets for a while, adds reps (or sets), and then you’d add weight, shifting back to fewer reps while you adapted to the new weight. And then, when you could do more reps at the higher weight, add weight again. Same with cardio — you progress by adding time (or distance) or “intensity” (a term that can refer to the heaviness of the weights you’re lifting or the speed at which you’re moving).
As you progress with your cardio, there are all kinds of ways to keep improving — and just keep it interesting: work on speed or distance, mix in different kinds of workouts (some longer and slower; some shorter and faster; some mixing different paces), or try different forms for variety (runner? Try some cycling or swimming, or hop on the rowing machine). You can also try different kinds of activities or classes, like snorkeling (or diving) or obstacle races — one of the great pleasures of improving your cardio conditioning is being able to do more things outside with friends and family. And have some fun!