4 Pics 1 Word Level 31

Answer:
Hard
Hint
What is the answer to the 4 Pics 1 Word level with Steep hill, Rock hard abs, muscle, 6-pack, Pile of rocks, and Nut, hard shell?

Hint
What is the answer to the 4 Pics 1 Word level with Steep hill, Rock hard abs, muscle, 6-pack, Pile of rocks, and Nut, hard shell?