I've fallen onto sand before that was fine, my other fall we were on grass but I landed onto cement on my hip. No bruising. The arena yesterday was pretty hard, and I hurt way more today then I ever did when I got hit by a car last year. But it is interesting, getting stupid bruises over small things but over bigger things? Nope.
I was just wondering if there was a scientific reasoning for this lol I've had this question in my head for years.
Hey TT89, when you fall, a relatively large area of your body makes contact with the ground, and this results in lower force per unit area body surface than when you get poked with something, or bang your shin, or walk into furniture. The force of the impact is spread across relatively more surface.
The higher the place from which you fall, the greater the force of the fall, so as the height increases, eventually it does become a bruising, internal-vessel-rupturing, dangerous thing, especially on a hard unyielding surface.
The things that bruise us usually involve a forceful impact on a small area.
Also, proximity to bone is a factor - your shins will bruise more easily than your calves, for example, because muscle is more elastic than bone and this absorbs some of the force of the impact and spreads it out more harmlessly than a direct knock to skin over relatively unyielding bone (where the impact is also more likely to be "pointy"). This is similar to the concept of crumple zones for absorbing impacts in vehicle crashes, or a helmet with a crushable shell lining compared to a hard hat only, or jogging in canvas shoes compared to joggers with thick soft soles.
A fall hurts usually more than a bruising knock because it activates more pain receptors (because more surface). The individual pain receptors don't trigger as much as they would in a sharper blow, but there are more of them. It's like 1000 people shouting out compared to 20 screaming hysterically - who makes more noise?