grueling

Medical school, internship, and residency had been physically and emotionally grueling.

There's a grueling uphill stretch of road at mile 23 of the marathon.

Belinda tried strict diets, grueling exercise routines, and some sort of esoteric New Age detox, all amounting to nothing--she had curves, and that was that.

Nadal won a grueling tennis match. It lasted five sets.

That was grueling.

The team's schedule is grueling.