Sore/Bruised/Cracked ribs
Stiff neck
Bruised knees
Forearm pump
You can take measures to mitigate these of course…
A seat that fits and hugs you in the right places (A lot of people swear by ribtect, let’s just say I don’t)
Rib protector that does same but more padding will mean less feel.
Heel stops (helps support your body under the forces)
Overall fitness and weight.
That said, sometimes you catch a bump the wrong way at the wrong time and……pop. OW!