bushbabies

[the guy]

senegal bushbabies weigh around 250g and are around 16cm long (excluding the tail) but they can jump around 5m. :confused:does anyone know how they manage this or can provide a site showing the anatomy of their legs and describing how its done because that is pretty amazing.

also, if you know of any mammal which is a better jumper please say so:-)

[Mokele]

Actually, the highest reported vertical jump is 2.25m.

 

There's actually a whole paper on it, here, and this is actually my precise field of expertise.

 

Basically, what limits jumping performance is power - muscles can produce a maximum of ~350W/kg at optimal conditions, simply due to muscle physiology. In order to circumvent this limit, a variety of animals (frogs, bushbabies, locusts) use tendons as springs, allowing them to store energy in the tendon & release it in a sudden contraction with much higher power output.

 

Imagine how far you can throw a rock. Then put the rock in a slingshot, and it goes much farther. You're added the same amount of energy to the rock via your muscles, but a rubber of the slingshot stores that energy & releases it all at once.

[Paralith]

Mokele, if this is your field of expertise maybe you can help me out with a question people ask me a lot, which is why are chimpanzees and bonobos so much stronger than humans pound-for-pound? I have thought that part of it must be differences in muscle physiology but if I understand you correctly, all mammalian muscle has a specific power limit of ~350W/kg. Is that so? And if it is, how would you account for the strength difference?

[Mokele]

The strength of chimps is due to several things, first and foremost a lifestyle that doesn't involve TV and Whoppers. Theirs is a very rough-and-tumble life, so in comparing strength, it would be most apt to compare them to very athletic humans.

 

Basic muscle physiology counts for a lot, too. Muscles have limits on the amount of force they can produce, work (force x distance) they can do, and power they can produce.

 

Force is dependent upon cross-sectional area of the muscle, and as you can imagine, a slight change in perceptible muscle size (such as diameter), would have a large effect on maximal force. Double diameter means 4x the force. Chimps are very muscular animals, thus, lots of force.

 

Another issue is work, force x distance. Those long arms mean long muscles, so even if a chimp biceps was no bigger around than a human's, the extra length would mean extra energy is imparted to the distal limb segment. And that energy can go directly into injuring unwary keepers.

 

Both of these combine to explain why I expressed power in W/kg. If force is dependent on cross section, and work depends on force and length, therefore work depends on total muscle volume (and muscle has a fairly consistent density of about 1.1 g/cm^3). Power is just the rate of work done, thus also depends on muscle mass (it also depends on shortening velocity, but that's not really applicable to this question, though it is to jumping).

 

So basically, chimps are so strong because they have bigger muscles, and even slight differences in muscle mass can have effects on force and power an animal can produce.

[the guy]

thanks alot that was really helpful. i meant horizontally when i said 5m btw.

[Paralith]

A 135 lb captive female chimp registered over 900 lbs of force on a two handed pull, and a 155 lb male human college football player (who had spent all summer before doing hard labor on a farm, reportedly) registered at most 395 lbs of force on an equivalent pull. Do you think just small differences in muscle mass are enough to explain that difference?

 

I've also read this paper on vertical jumping in bonobos, who were able to reach jump heights above 0.7 m. The authors suggested that the bonobo muscle is simply able to output more force per cross sectional area than humans.

[iNow]

I've also read this paper on vertical jumping in bonobos, who were able to reach jump heights above 0.7 m. The authors suggested that the bonobo muscle is simply able to output more force per cross sectional area than humans.

 

I may be mistaken, but isn't that what Mokele was addressing when he referred to the difference in leverage due to length of muscle (that diameter was not as important as length)? As for the stark contrast btw what a female chimp and a male human athlete of similar size can do on the two handed pull, that is a curious question. I am inclined to think that it has something to do with the overall life of the chimp decades spent each day building muscles, and very well coordinated core strength (where the body is one big muscle), as opposed to just "big biceps" or "big shoulders." However, I too am interested to hear from Mokele as he's much more informed on this topic.

[Paralith]

The authors took overall muscle mass into account, if I understood the paper correctly - which I may not have. It was my impression that regardless of size they were finding a greater power output than expected according to human norms.

 

Keep in mind also that these are captive chimps, and these measures in particular were from a study in 1926, so not only do captive chimps in general have less to do but in the 1920's I'm sure their enclosures did not contain many opportunities for chimp-like exercise.

[Mokele]

A 135 lb captive female chimp registered over 900 lbs of force on a two handed pull, and a 155 lb male human college football player (who had spent all summer before doing hard labor on a farm, reportedly) registered at most 395 lbs of force on an equivalent pull. Do you think just small differences in muscle mass are enough to explain that difference?

 

The increase in muscle radius necessary to explain that difference is less than 50%, and that doesn't take into account postural differences, differences in muscle origin/insertions, which muscles were used when, etc. Leg use would be especially important in a task like that, as well as center of gravity. Our legs are runner's legs, not made for exerting great forces, and the in-lever/out-lever ratios suck compared to a chimp.

 

I've also read this paper on vertical jumping in bonobos, who were able to reach jump heights above 0.7 m. The authors suggested that the bonobo muscle is simply able to output more force per cross sectional area than humans.

 

Interesting, but considering that the fact that muscle properties are pretty well conserved from worms to insects to fish to humans, I'm very skeptical of any claims of different muscle properties, especially of that magnitude, without excised-muscle experiments.

 

Several problems are immediately apparent, most notably the lack of 3-D kinematics, and the poor quality of kinematics in general due to lack of even simple joint markers. The authors assume no 'rockbacks' or other pre-jump stretching, but without direct (and invasive) measurements, that's simply not possible to confirm.

 

Honestly, such poor data does not support such a gradiose conclusion.

 

I may be mistaken, but isn't that what Mokele was addressing when he referred to the difference in leverage due to length of muscle (that diameter was not as important as length)?

 

Diameter is actually the sole determinant of baseline force (though the muscle and have increased or decreased force from baseline due to loading conditions).

 

Leverage, however, is also very important, for the obvious physical reasons of in-lever/out-lever ratios. From what I understand, chimps generally have an advantage in leverage, particularly at the shoulder joint and hips.

 

Mokele

[Moontanman]

It would seem there is a real difference in the way chimp muscles and human muscles actually work.

 

So the figures quoted by primate experts are a little exaggerated. But it is a fact that chimpanzees and other apes are stronger than humans. How did we get to be the weaklings of the primate order? Our overall body architecture makes a difference: Even though chimpanzees weigh less than humans, more of their mass is concentrated in their powerful arms. But a more important factor seems to be the structure of the muscles themselves. A chimpanzee's skeletal muscle has longer fibers than the human equivalent and can generate twice the work output over a wider range of motion. In the past few years, geneticists have identified the loci for some of these anatomical differences. One gene, for example, called MYH16, contributes to the development of large jaw muscles in other apes. In humans, MYH16 has been deactivated. (Puny jaws have marked our lineage for as least 2 million years.) Many people have also lost another muscle-related gene called ACTN3. People with two working versions of this gene are overrepresented among elite sprinters while those with the nonworking version are overrepresented among endurance runners. Chimpanzees and all other nonhuman primates have only the working version; in other words, they're on the powerful, "sprinter" end of the spectrum.

 

http://www.slate.com/id/2212232/

[Mokele]

Interesting, I hadn't heard about the latter of those molecular findings. Fiber type is still an interesting area, in part because it's controversial whether it actually affects force output at the molecular level or force differences are a result of slow twich fibers having more extraneous 'stuff' around them, like blood vessels and mitochondria, thereby reducing the percentage of actual contractile machinery per unit cross-sectional area.

 

I think the best way to test it is to do single-fiber muscle experiments - wait until they have to put a chimp under for some unrelated surgery, then excise a single muscle fiber and do in-vitro tests to determine its properties. We already have such data for humans, IIRC. The chimp might have a sore arm for a day or two, but nothing serious.

[CDarwin]

senegal bushbabies weigh around 250g and are around 16cm long (excluding the tail) but they can jump around 5m. :confused:does anyone know how they manage this or can provide a site showing the anatomy of their legs and describing how its done because that is pretty amazing.

also, if you know of any mammal which is a better jumper please say so:-)

 

Without addressing the responses about muscle action, which are well above my education, there are some skeletal implications of how bush babies (also called galagos) move, too. Their fibula is reduced and wraps very close to the tibia, increasing the strength of the combined bone and its leveraging ability. There's a fossil group of prosimians called omomyoids that share lower leg adaptations very similar to those of galagos, and probably moved similarly. Tarsiers, who rely even more heavily on leaping from vertical supports, take this to an even greater extreme, with a completely fused tibio-fibula.

 

You can compare a the lower leg bones of the galago here:

 

To a tarsier here:

http://www.bohol.ph/pics/large/IMG_0577_Tarsier_Skeleton.jpg

 

Notice the extended ankle bones, or tarsa, of both animals as well. They also help increase the leverage of the legs.

Edited March 15, 2009 by CDarwin

[Mokele]

CDarwin is correct - jumpers often have very long legs, with elongated, fused leg bones. Compare the galago skeleton in his post with this frog skeleton - same elongated limb bones, long ankle bones, etc. It also holds true for kangaroos and locusts.

 

The main reason for this all comes back to muscles. If your muscles contract in conditions optimal for power generation (~30% of maximum shortening velocity), your final kinetic energy when you leave the ground will be Power x jump duration. Increasing the leg length means you exert that maximal power over a longer time, and thus achieve a higher final velocity.

[visceral]

So basically, chimps are so strong because they have bigger muscles, and even slight differences in muscle mass can have effects on force and power an animal can produce.

 

How come some humans can be really thin without much muscle and still be disproportionately strong?

[Mokele]

How come some humans can be really thin without much muscle and still be disproportionately strong?

 

How are you assessing muscle size, though? Some humans may have an illusion of more muscle due to having subcutaneous fat deposits, as well as fat deposits between and around muscles, while others with less fat may appear to have smaller muscles but actually have larger real muscle area.

 

There's also possible variations within a muscle in the percent of cross-sectional area used for non-contractile stuff like blood vessels, sarcoplasmic reticulum, and mitochondria.

[visceral]

How are you assessing muscle size, though? Some humans may have an illusion of more muscle due to having subcutaneous fat deposits, as well as fat deposits between and around muscles, while others with less fat may appear to have smaller muscles but actually have larger real muscle area.

 

There's also possible variations within a muscle in the percent of cross-sectional area used for non-contractile stuff like blood vessels, sarcoplasmic reticulum, and mitochondria.

 

I was thinking of 2 sisters who I go to kickboxing class with, they both have very little fat and not much visible muscle, and both are disproportionately powerful. Could such "wiry" people have most of the muscle taken up with the contractile stuff?

[Mokele]

Ahh, this probably relates to muscle fiber types. ~350W/kg is the maximum, the that's also for 'fast twitch' fiber types, the sort you often use in martial arts. 'Slow twitch' fibers, which are more commonly used in endurance sports like running (as well as for everyday activities like walking) have a lower peak power, though how much lower is dependent upon precise molecular differences.

 

Also, speaking from martial arts experience, a LOT of it is technique. Doing moves 'right' allows you to use muscles more optimally, allows you avoid wasting effort, and allows you to even recruit additional muscles that would otherwise not be used, to add power. Whenever they say 'put your hips into it', what they're actually saying is to use your large leg muscles to provide additional power.

[visceral]

Thanks for answering that Mokele