Low effective mechanical advantage of giraffes' limbs during walking reveals trade-off between limb length and locomotor performance.
Low effective mechanical advantage of giraffes' limbs during walking reveals trade-off between limb length and locomotor performance.
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DOI：
10.1073/pnas.2108471119
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发表时间：
2022-07-12
影响因子：
11.1
通讯作者：
中科院分区：
文献类型：
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长颈鹿是现存最高的动物，利用它们的高度来获取竞争对手无法获得的食物。目前尚不清楚他们的特殊解剖结构如何影响他们的运动能力。我们制作了长颈鹿和两个近亲的前肢肌肉骨骼模型，并使用动作捕捉和力数据来测量它们在直线行走时的效率。例如，一匹马仅使用 1 个单位的肌肉力量来对抗地面上的 1 个单位的力。长颈鹿的四肢相对处于劣势——它们的肌肉必须产生3个单位的力才能抵抗地面上1个单位的力。这解释了为什么长颈鹿行走和奔跑的速度适中。长颈鹿（Giraffacamelopardalis）具有特殊的运动形态，即细长且纤细的远端肢体。虽然这有助于提高它们的整体高度并增强摄食行为，但我们认为，与其他粗略哺乳动物相比，长肢节和适度的肌肉杠杆臂的组合导致有效机械优势（EMA，内杠杆与外杠杆力臂的比率）较低。为了测试这一点，我们结合了实验测量的运动学和地面反作用力 (GRF)、肌肉骨骼建模和逆动力学来计算长颈鹿行走期间的前肢 EMA。长颈鹿行走时的 EMA 为 0.34 (±0.05 SD)，与行走步态的速度没有明显关联。长颈鹿的 EMA 比其他哺乳动物推断的预期值低约四倍，范围为 0.03 至 297 公斤，这进一步证明，在体型超过马的哺乳动物中，EMA 趋于稳定甚至减少。我们通过对已灭绝长颈鹿 Sivatherium giganteum 和另一种现存长颈鹿 Okapia johnstoni 的 GRF 和肌肉力臂进行建模，进一步验证了肢节长度是决定 EMA 的一个因素的观点。长颈鹿和霍卡皮亚的 EMA 相似，尽管体重相差四到六倍（霍卡皮亚 EMA = 0.38）。相比之下，Sivatherium 与长颈鹿体重相似，具有更大的 EMA (0.59)，我们认为这反映了行为差异，例如运动表现能力有所增强。我们的建模方法表明，肢体长度是 GRF 力臂大小的决定因素，除非肌肉力臂与肢体长度等距缩放，否则高大的哺乳动物容易出现低 EMA。
Giraffes are the tallest living animals, using their height to access food unavailable to their competitors. It is not clear how their specialized anatomy impacts their athletic ability. We made musculoskeletal models of the forelimbs from a giraffe and two close relatives and used motion-capture and force data to measure how efficient they are when walking in a straight line. A horse, for example, uses just 1 unit of muscle force to oppose 1 unit of force on the ground. Giraffe limbs are comparatively disadvantaged—their muscles must develop 3 units of force to oppose 1 unit of force on the ground. This explains why giraffes walk and run at modest speeds. Giraffes (Giraffa camelopardalis) possess specialized locomotor morphology, namely elongate and gracile distal limbs. While this contributes to their overall height and enhances feeding behavior, we propose that the combination of long limb segments and modest muscle lever arms results in low effective mechanical advantage (EMA, the ratio of in-lever to out-lever moment arms), when compared with other cursorial mammals. To test this, we used a combination of experimentally measured kinematics and ground reaction forces (GRFs), musculoskeletal modeling, and inverse dynamics to calculate giraffe forelimb EMA during walking. Giraffes walk with an EMA of 0.34 (±0.05 SD), with no evident association with speed within their walking gait. Giraffe EMA was about four times lower than expectations extrapolated from other mammals, ranging from 0.03 to 297 kg, and this provides further evidence that EMA plateaus or even diminishes in mammals exceeding horse size. We further tested the idea that limb segment length is a factor which determines EMA, by modeling the GRF and muscle moment arms in the extinct giraffid Sivatherium giganteum and the other extant giraffid, Okapia johnstoni. Giraffa and Okapia shared similar EMA, despite a four to sixfold difference in body mass (Okapia EMA = 0.38). In contrast, Sivatherium, sharing a similar body mass with Giraffa, had greater EMA (0.59), which we propose reflects behavioral differences, such as a somewhat increased capability for athletic performance. Our modeling approach suggests that limb length is a determinant of GRF moment arm magnitude and that unless muscle moment arms scale isometrically with limb length, tall mammals are prone to low EMA.
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影响因子：
2.7
作者：
Bishop PJ;Wright MA;Pierce SE
通讯作者：
Pierce SE
影响因子：
2.4
作者：
Charles JP;Cappellari O;Spence AJ;Wells DJ;Hutchinson JR
通讯作者：
Hutchinson JR
影响因子：
--
作者：
CAVAGNA, GA;HEGLUND, NC;TAYLOR, CR
通讯作者：
TAYLOR, CR
DOI：
10.1111/j.1096-3642.2008.00458.x
发表时间：
2009-03-01
影响因子：
2.8
作者：
Badlangana, N. Ludo;Adams, Justin W.;Manger, Paul R.
通讯作者：
Manger, Paul R.
影响因子：
56.9
作者：
BIEWENER, AA
通讯作者：
BIEWENER, AA