A ski machine is a training tool for cross-country skiers, but the general fitness community has also embraced it. You do not have to be a skier to reap the benefits of SkiErg's total-body exercise.

The real fun — and frustration — was when I turned on live coaching in the app, which gives you real-time feedback as you schuss down the mountain. The feedback can come in the form of pings — a ...