I think in Middle-Earth there wear different "breeds" of orc. Some were stronger than others. I wish I had my MERP books here so I could look it up. Saruman created the "Uruk-Hai" which were a hybrid of troll and Human(?) so that they could be effective in daylight and have high stamina.
From the
Encyclopedia of Arda
Orcs:
Little is known for certain of the beginnings of the Orcs, the footsoldiers of the Enemy. It is said that they were in origin corrupted Elves captured by Melkor before the beginning of the First Age. In appearance, Orcs were squat, swarthy creatures. Most of them preferred the darkness, being blinded by the light of the Sun, but the kinds bred later in the Third Age such as the Uruk-hai could endure the daylight.
Uruk-Hai:
The great soldier-Orcs that first appeared in the late Third Age; they were larger and stronger than their forebears, and could withstand the light of the Sun.
Half-Orcs:
Creatures bred from Orcs and Men by the Wizard Saruman in his stronghold at Isengard. Like Sauron's Uruk-hai, they could withstand sunlight. The more Man-like of them, of perhaps a slightly different breed, were known as Goblin-men.
Goblin/Hobgoblin:
A name almost synonymous with Orcs. There is some debate about how closely the the two terms are related to one another, and indeed it could be argued that they both effectively relate to the same thing.
The following quote from the foreword to The Hobbit sheds some light on this: "[The word 'Orc'] occurs in one or two places but is usually translated goblin (or hobgoblin for the larger kinds.)' The fact that the larger kinds are given their own special word might suggest that goblins tend to be smaller Orcs, but the evidence on this point is inconclusive.
The word 'goblin' is also used occasionally and indiscriminately in The Lord of the Rings; it never occurs in the The Silmarillion.
Olog-Hai:
A race of trolls bred by Sauron in the later years of the Third Age, seen among the trees of southern Mirkwood, and the mountain borders of Mordor. They were superior to other trolls in almost every way: stronger and more powerful, but also showing greater intelligence and skill. Many of their abilities they owed to being under the direct will of their master, Sauron, and while under his control they could exist in direct sunlight, unlike others of their kind.
In the battle before the Gates of Mordor, Aragorn and the Captains of the West encountered a company of large trolls, identified as 'hill-trolls out of Gorgoroth'1. That battle took place in sunlight, and so it seems to follow that the hill-trolls must have been Olog-hai. They are described as being taller than a man, and covered in horny scales, carrying hammers and bucklers in their claws, though there is no way of knowing whether this description applies to all of the Olog-hai, or just to those in the battle.