Peripheral loading is a negative situation for the hoof, because it severely interferes with blood flow inside the hoof. Bowker conducted experiments in velocity of blood flow in the hoof using Doppler Ultrasound. What he discovered is that harder surfaces made the blood flow faster, and when it did that, it never “perfused” the tissues. It was just like a rainstorm in the desert (and I’ve seen plenty of those!)—water gushes down in a flood, but never sinks into the ground. The faster the blood flow, the less blood made it to the tissues!
On softer surfaces (pea rock, sand or foam pads) blood flow will slow down and trickle through small vessels—microvenous vessels. On hard surfaces (cement or wood blocks), tissue perfusion dramatically decreases, so blood moves faster through foot—it must stay in the large vessels. Different surfaces will change tissue perfusion, with softer, more forgiving surfaces having the greatest tissue perfusion.
He also documented the effects of more extreme peripheral loading. With a shod hoof, blood flow actually came to a halt for a split second with every heartbeat, at the level of the horse’s fetlock. In a computer model that he developed with some engineers, he measured stresses on the coffin bone, and discovered that a peripheral load encouraged bone to be removed. A solar load encouraged bone to be laid down, or at least not removed.
Many horse owners give barefoot a try, but it oftentimes does not work because the horse is given a pasture trim, which leads to tenderfootedness, flares, chips, and cracks. Of course, the shoes are then put back on, as the owner believes that the horse simply "doesn't have the hooves to go barefoot." It's a shame, because many (maybe not all) of those horses could most likely remain barefoot if they had been trimmed and transitioned properly.
(3rd NBT, still not at his "ideal" hoof, but getting there)
Note the rounded edge of the hoof wall,
Right front hoof, 4 weeks post-natural barefoot trim
Note the elimination of all chips, cracks, and flares, plus the tight connection all the way around the hoof. Candy, Salem's trimmer, noted that he had the healthiest hooves of any horse she trims. This was due to 24/7 turn-out, a low-NSC diet, daily spraying with apple cider vinegar/water to eliminate fungus etc., weekly rasping to maintain the mustang roll, and trimming every 4-5 weeks. Of course, the biggest change was the type of trim he received -- as soon as he was switched from a trim that loaded his hooves peripherally to one that distributed his weight properly, his hooves showed immediate improvement.
(ETA: I am not a proponent of the Strasser trim, as I feel it is far too aggressive and can do a great deal of damage to the horse. The Strasser method promotes carving concavity into the hoof, while the methods of The Oregon School of Natural Hoofcare, Pete Ramey, Jaime Jackson, etc. believe in allowing concavity to naturally develop.)