To get the same results of a Speedflex session you’d have to pant breathlessly around a park for two hours, walk across the moors for five hours imagining you’re in a Bronte novel or do seven hours of another kind of heavy breathing (nudge nudge, wink wink).
There’s much less risk of injury and you’re toning up not building bulk, so don’t worry about waking up looking like Arnie.
Plus, it’s cheaper than a personal trainer. And it just so happens to be serious fun. You’ll even carry on burning those calories long after your session. Bonus.