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In other words, post-prime brown bears (most likely all bears) can continue to gain muscle mass and maximum force without much muscle volume due to them being able to gain dense slow-twitch Ib fibers much easier, again, due to higher ERL levels. Prime brown bears are able to gain muscle volume, but not as a fast rate as muscle mass or maximum force, that's why they look so huge and bulk at lower weights. At equal sizes/dimensions, the post-prime brown bear would most likely be much MUCH heavier than the prime brown bear due to, again, denser Ib fibres. Fast-twitch fibers (IIa/x and IIb fibers) are larger in volume at the same mass than slow-twitch fibers (Ia and Ib fibers), and they produce the most change in force within the shortest time, not the absolute most force. IIa fibers contract forces very fast within the first second of activation, and IIb fibers, being even larger in volume within the same mass as IIa fibers, contact the same forces at an average speed 40% faster than IIa fibers. Slow-twitch fibers actually have two functions: one for endurance/stamina, and one for a gradual contraction of brute force. Ia fibers are the former and Ib fibers are the latter. Ia fibers contract at maximum force depending on how many of those fibers the person has (hence, why a great marathon runner's muscles ache after a 2-hour marathon, and why a sprinter's muscles ache after about 40 seconds, if accounting for the same cardiovascular/respiratory endurance levels and weight: they each have an individual percentage of these Ia fibers.) Usually, the maximum force of Ia endurance-type fibers is 20% of the force displayed in either IIa/x or IIb fibers.
On the other hand, Ib brute strength-type fibers, at the same mass as either of IIa/x or IIb fibers, produce approximately 80% more force than the two fibers at maximum contraction, albeit at a much much slower rate, at approx. 13 (have to look back at the article: I found new research on muscle fibers about two years ago, but sadly didn't save it under my Google Drive) seconds for max force.
People think that greater fast-twitch fiber levels (bigger muscles) will lead to an increased maximum amount of force output. No, it will only lead to an increased amount of force output within the shortest amount of time. That's how the "fast-twitch fibers are stronger than slow-twitch fibers" myth originated, because of the confusion between power (maximum force output within shortest amount of time) and strength (maximum force output overall at any time.) Really, at the same volume, a muscle composed of Ib fibers will be humongously stronger at maximum contraction than a muscle composed of either IIa/x or IIb fibers, however, the IIa/x muscle will contract more force than the Ib muscle for the first one second, and IIb muscle will contract more force than the IIa/x muscle before one second and much more force than the Ib muscle during that same time period. It's all about the rate/time of contraction. I will post more on real-life uses of fast-twitch IIa/x and IIb fibers and slow-twitch Ib fibers later. 
I haven't read the study yet but the sacrifice of fast twitch muscle fiber for slow twich isn't necessarily a good or bad thing. Fast twich allows quicker explosive movements and speed creates power.
An animal able to react quicker while being similar in strength (slightly weaker) may be the superior animal. Big cats are the perfect example of the advantages obtained from high volume fast twitch muscle fibers. I wonder which age is considered to be a Bears "prime?" I consider 6-8 to be a big cats "prime."  (01-22-2016, 11:03 PM)Pckts Wrote: I haven't read the study yet but the sacrifice of fast twitch muscle fiber for slow twich isn't necessarily a good or bad thing. Fast twich allows quicker explosive movements and speed creates power. In my opinion: the prime age for a male grizzly is likely from 10 to 12 years old but he will continue growing in size and strength up to somewhere between 15 and 20. (01-23-2016, 12:00 AM)brotherbear Wrote:(01-22-2016, 11:03 PM)Pckts Wrote: I haven't read the study yet but the sacrifice of fast twitch muscle fiber for slow twich isn't necessarily a good or bad thing. Fast twich allows quicker explosive movements and speed creates power. You mean size as in more fat volume? That's true, but no size increase in muscle volume because of denser muscles, as proven by the study. Muscles with more Ib fibers tend to produce denser bones (not thicker, but denser as in increased bone filament density over a cross-section area of bone.) Beside the points I made, I agree with your assessment that older brownies increase in maximum strength.
Both pckts and brotherbear, remember that the study focused in bear sizes regarding muscle volume, not counting bone widths/lengths or fat mass. In my opinion, I believe a post-prime bear can only be larger (in size) than a prime bear if:
1. He has a VERY significant amount of Ib fibers, enough to equal the muscle volume of the prime bear, thus the post prime one would be MUCH heavier. 2. He gains plenty of fat and fur to gain the same volume as the prime bear. (Which is more often the case.) (01-23-2016, 12:57 AM)Polar Wrote:No; after 10 or 12 years a grizzly will continue to gain in bone and muscle. Most dominate male grizzlies, those who dominate the best food resources and choice females are upwards to about 15 years old or better.(01-23-2016, 12:00 AM)brotherbear Wrote:(01-22-2016, 11:03 PM)Pckts Wrote: I haven't read the study yet but the sacrifice of fast twitch muscle fiber for slow twich isn't necessarily a good or bad thing. Fast twich allows quicker explosive movements and speed creates power.
Polar, after going back and rereading your post and rethinking the issue, perhaps I was too hasty. Denser muscle tissue would in fact bring about the same results.
A fully mature male grizzly - Ursus arctos - Brown bear, can range in weight from 300 to 1,300 pounds according to his clade, environment, and food availability.
 *This image is copyright of its original author
Scroll down to 'Brown Bear Directory' page #1 and look at some of those bears pictured by Roflcopters. Some of those wild bears are fatter than any I have seen in captivity. Bears such as Bart, Bart Jr, and Brutus are probably less muscular than their wild brothers, but they are certainly not obese on bear terms. Jimbo while not truly obese is probably fatter than he should be year-round.
The Great Bear Almanac by Gary Brown.
The Boone and Crockett system described in chapter 6 scores the bears accordingly. This is a tangible means of size comparison, but not totally indicative of total size, as individual variations occur. For example, a large, heavy bear may have a small, short, or narrow skull, providing it with a total skull size unrepresentative of its overall body size.
The Bear Almanac by Gary Brown - The Boone and Crockett Club.
The club, started by Theodore Rossevelt in 1887 as a "Big Game" conservation organization, ascribes to strong ethical hunting, such as fair chase and sportsmanship, and several North American states and provinces have adopted many of its standards. Roosevelt aptly named the club after frontiersmen Daniel Boone and Davy Crockett, who represent the hunting standards prescribed. In 1950 the club adopted a scoring system that provides "objective" measurements and scores of big-game animals, thus "Big Game Records" of North America. The club manages an official scoring meant to record skull size. Recorded skulls normally originate from a fair-chase hunt, though a few discovered and "picked up." The recorded score is the total ( in inches ) of the skull length and width. Records are maintained by species of bear.
Largest Boone and Crockett Skulls:
Alaskan Brown Bear: Length 19 and 13/16 ... Width 17 and 14/16 ... Total Score 30 and 12/16. Polar Bear: Length 18 and 8/16 ... Width 11 and 7/16 ... Total Score 29 and 15/16. From http://shaggygod.proboards.com/ the record total of the Kamchatka brown bear: 30 and 11/16. The record short-faced bear skull, from the biggest Arctodus simus specimen ever discovered, measures 20.51 inches. The record brown bear skull, that of a Kodiak, measures 19 and thirteen sixteeths inches long. The length difference is less than one inch.
California Grizzly by Tracy I. Storer and Lloyd P. Tevis, Jr.
The bodily framework of the grizzly is substantial, to support the weight of the animal; yet the bear has a greater degree of flexibility in its movements than is possible in many other sturdily built mammals. This freedom of motion is a correlated function of the bones, ligaments, and muscles. The skeleton of a bear - grizzly or other kind - is much like that of related carnivores, but there are many small differences. A noticeable massiveness is evident in all the bones. The neck vertebrae are large but are capable of much rotation movement, the spinous processes along the back on the dorsal vertebrae are heavy, and the shoulder blade is ample. The limbs are of nearly equal length. Both fore and hind feet are fully plantigrade: the entire surface of each foot comes in contact with the ground as the bear walks. The bones used in lifting or extending the feet ( the pisiform on the fore foot, the calcaneum on the hind ) are larger than in some other carnivores. All bones of the legs, both front and rear, are separate. In the front leg, the radius and ulna are of nearly equal size for easy and powerful rotation of that member; and in the hind leg, the fibula, which is involved in twisting movements, is free and larger in relation to the tibia than in mammals unable to make such movements. These skeletal features, together with the muscles attached to them, give the bears dexterity in using their limbs - more or less in the manner of human beings ( fig. 11 ). (01-28-2016, 04:30 PM)brotherbear Wrote: Scroll down to 'Brown Bear Directory' page #1 and look at some of those bears pictured by Roflcopters. Some of those wild bears are fatter than any I have seen in captivity. Bears such as Bart, Bart Jr, and Brutus are probably less muscular than their wild brothers, but they are certainly not obese on bear terms. Jimbo while not truly obese is probably fatter than he should be year-round. Those bears are the fattest bears I have ever seen, which leads me to believe they are dumpster diving bears. When you look at Wild bear documentary after documentary or image after image, Kodiak, Yellowstone etc. Camera trap images shown, the % of bears who look like that is less than 10% of what I have seen. Edit: I just looked through that directory again and some of those bears definitely put on serious weight leading up to sept. But those bears are all from the same location, correct? And all seem to be salmon eaters and I assume any bear who eats salmon swimming up stream will be a huge bear. They literally sit in one spot while the salmon swim to them. But even so, the directory is good cause it shows you the bear from summer leading to winter and the bears are in great shape but continue to add weight leading to hibernation. |
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