1 / 30 2 / 30 3 / 30 4 / 30 5 / 30 6 / 30 7 / 30 8 / 30 9 / 30 10 / 30 11 / 30 12 / 30 13 / 30 14 / 30 15 / 30 16 / 30 17 / 30 18 / 30 19 / 30 20 / 30 21 / 30 22 / 30 23 / 30 24 / 30 25 / 30 26 / 30 27 / 30 28 / 30 29 / 30 30 / 30 ❮ ❯ A bicycle crunch involves lying flat on.