Numerous anthropological studies have been aimed at estimating jaw-adductor muscle forces, which, in turn, are used to estimate bite force. While primate jaw adductors show considerable intra- and intermuscular heterogeneity in fibre types, studies generally model jaw-muscle forces by treating the jaw adductors as either homogeneously slow or homogeneously fast muscles. Here, we provide a novel extension of such studies by integrating fibre architecture, fibre types and fibre-specific tensions to estimate maximum muscle forces in the masseter and temporalis of five anthropoid primates: Sapajus apella (N = 3), Cercocebus atys (N = 4), Macaca fascicularis (N = 3), Gorilla gorilla (N = 1) and Pan troglodytes (N = 2). We calculated maximum muscle forces by proportionally adjusting muscle physiological cross-sectional areas by their fibre types and associated specific tensions. Our results show that the jaw adductors of our sample ubiquitously express MHC α-cardiac, which has low specific tension, and hybrid fibres. We find that treating the jaw adductors as either homogeneously slow or fast muscles potentially overestimates average maximum muscle forces by as much as approximately 44%. Including fibre types and their specific tensions is thus likely to improve jaw-muscle and bite force estimates in primates.

许多人类学研究旨在估计下颌-内收肌的力量，而这反过来又被用来估计咬合力。虽然灵长类动物的下颌内收肌在纤维类型上表现出相当大的肌内和肌间异质性，但研究通常通过将下颌内收肌视为均匀缓慢或均匀快速的肌肉来模拟下颌肌肉力。在这里，我们通过整合纤维结构、纤维类型和纤维特异性张力来估计五种类人猿灵长类动物咬肌和颞肌的最大肌肉力，从而提供此类研究的新扩展：Sapajus apella ( N = 3)、Cercocebus atys ( N = 4)、食蟹猴( N = 3)、Gorilla 大猩猩( N = 1) 和Pan troglodytes ( N = 2)。我们通过根据纤维类型和相关的特定张力按比例调整肌肉生理横截面积来计算最大肌肉力。我们的结果表明，我们样本的下颌内收肌普遍表达 MHC α-cardiac，其具有低比张力和混合纤维。我们发现，将下颌内收肌视为均匀缓慢或快速的肌肉可能会高估平均最大肌肉力量约 44%。因此，包括纤维类型及其特定张力可能会改善灵长类动物的下颌肌肉和咬合力估计。