Really simple answer with concrete evidence }
- Felines proportionately have a greater BMR which likely means a greater muscle mass } http://books.google.com/b...63&dq=bmr+muscle+mass
Bears usually eat more than 80% of vegetable matter } http://books.google.com/b...rcentage+vegetable+matter
Even if this source gives a slightly lower value... most of sources report something over 80%.
Felines have a more anaerobic metabolism than bears for obvious reasons } They are ambush hunters built for short activities.
We have to keep in mind that this source is based on domestic animals.
If cats have an equal number of type I, IIa, IIb fibers, then we have 100/3 = Only slightly more than 30% of slow-twitch fibers in their whole body.
More information on this field }
So we have a difference over 25% based on... domestic cats.
But this is not the main point }
http://doi.wiley.com/10.1002/jmor.10673 } "By mATPase histochemistry five fiber types, i.e., I, IIC, IIA, IIAX, IIX were distinguished."
Bears lack the IIb fibers... that's the most powerful and fastest muscle fibers.
The explanation usually given is such fibers cost too much energy for hibernating animals (even if Black bear doesn't make a true hibernation).
- Bears seem to have more fat than felines for the previous reason }
Thus we have a mean of 11,2%, still for domestic cats.
However this value is quite fluctuating for bears due to obvious reasons. But most of the time, they probably are over 12%.
- Cats have stronger forelimbs than their hindlimbs, like reported in any reliable source }
More widely, the front part is stronger.
Their forelimbs also are better built for strength }
However, the ratio is similar to that of the lion and cheetah. But most of felines have an advantage in this field.
Indeed, bears seem to have more weight concentrated in their hindlimbs. The rear always seems much stronger }
This is not to make a size comparison... don't get me wrong !
That's only to show their respective build.
- Felines have shorter limbs than bears }
About the last point of this source }
Based on a reasonable observation, felines certainly have better muscle attachements than bears } They need to be faster than bears, they need to have a far greater acceleration than bears.
Simply because cats are obligate carnivores and ambush hunters.
- Felines have a longer olecranon relative to the ulna length. This also provides a greater strength }
Credit to Ursus.
You can make the comparison with big cats on this link } http://tobias-lib.ub.uni-.../828/pdf/Diplomarbeit.pdf
- Big cats have a far stronger skull than almost any bear lbs for lbs } "Modelling that approximates the 3-D architecture of jaw adductors suggests that both the placental and marsupial lions could generate considerably greater bite forces than has been predicted using 2-D approaches, but with relatively greater forces in the marsupial. The distribution of cranial stress is in many respects similar in both species, but results from simulations of extrinsic forces suggest that the marsupial was particularly well adapted to resist the high stresses that would be expected in dealings with relatively large prey. On the other hand, relatively high stress recorded in the rostrum of T. carnifex under intrinsic loadings suggests that it may have deployed a very different modus operandi, wherein the carnassial teeth played an active role in effecting a kill."
That's like bones... heavy animals have stronger bones.
Animals with a strong bite have stronger skulls.
- Felines are able to kill preys much larger than themself, until 6 times their own weight. I don't know if bears can do the same... while they mainly hunt small animals } "and occasionally large animals such as horses, bison, and moose and other deer (usually young ones)."
Well, lbs for lbs cats appear stronger than bears with better adaptations for hunting and fighting } Their lifestyle is simply harder.
I can see few advantages for bears } Brown bears have a shoulder hump... but that's maybe all.
Any claim about chest girth, neck girth (etc.) is a pure speculation without any evidence.
Moreover, big cats don't have a shoulder hump, but their shoulders are very prominent }