Table 5.

Estimated hindlimb extensor mass (kg), summed over left and right hindlimbs, in a 34-kg bonobo, a 61.5-kg human and a 37-kg chimpanzee.

muscle group	function (sagittal plane)	34-kg bonobo	61.5-kg human	37-kg chimpanzee (Thorpe et al. 1999)
gluteals (m. gluteus maximus, m. gluteus medius, m. gluteus minimus, m. scansorius)	hip extension	0.95	3.08	1.28
hamstrings (m. biceps femoris, m. semitendinosus, m. semimembranosus)	hip extension, knee flexion	0.50	1.69	0.60
quadriceps (m. rectus femoris, mm. vasti)	knee extension, hip flexion (m. rectus femoris)	0.97	3.23	1.10
triceps surae (m. gastrocnemius, m. soleus, m. plantaris)	ankle extension, knee flexion	0.54	1.54	0.57
adductors (m. adductor magnus, m. adductor longus, m. adductor brevis)	hip extension (only in apes)	0.83		1.06
total		3.79	9.54	4.61