筋 (Kanji for muscle)

Onyomi

KIN

My KINfolk like to eat bamboo for strong, muscular organs.

すじ	tendon ☆☆☆☆☆

筋肉(きんにく)	muscle ★★★☆☆ 筋 (muscle) + 肉 (meat) = 筋肉 (muscle)
一筋(ひとすじ) に	single-mindedly, intently ★☆☆☆☆ KUNKUN 一 (one) + 筋 (muscle) = 一筋 (single-mindedly, intently)

Boxes are made of WOOD.

For crops, seasons are GOOD

PEOPLE buy tickets for seats,

to see the ORGANS of muscular athletes.