Table 6.

Mass, volume, rest length, cross-sectional area stress, strain and length change of selected pelvic limb tendons

Muscle tendon unit	Mass (g)	Volume (cm3)	Rest length (mm)	CSA (cm2)	Stress (MPa)	Strain (%)	Length change (mm)
Psoas major	7.4	6.6	90	0.73	22.9	1.53	1.37
Glutaeus superficialis	14.0	12.5	90	1.39	13.0	0.87	0.78
Tensor fascia lata	34.2	30.5	227	1.35	31.2	2.08	4.72
Biceps femoris	106.8	95.4	100	9.54	9.2	0.61	0.61
Semimembranosus	11.9	10.6	105	1.01	31.5	2.10	2.21
Gracilis	15.4	13.8	114	1.21	33.5	2.23	2.55
Sartorius	5.3	4.7	104	0.46	7.9	0.53	0.55
Gastrocnemius	90.7	81.0	244	3.32	27.0	1.80	4.39
Flexor digitorum superficialis	188.9	168.7	748	2.25	55.5	3.70	27.68
Flexor digitorum medialis	56.7	50.6	409	1.24	5.3	0.35	1.45
Flexor digitorum lateralis	127.0	113.4	574	1.98	97.8	6.52	37.42
Tibialis caudalis	6.1	5.4	131	0.42	26.7	1.78	2.33
Extensor digitorum lateralis	21.0	18.8	308	0.61	12.8	0.85	2.63
Extensor digitorum longus	59.6	53.2	472	1.13	14.4	0.96	4.53
Tibialis cranialis	26.9	24.0	92	2.61	8.4	0.56	0.52
Peroneus tertius	64.3	57.4	362	1.59	–	–	–
Suspensory ligament	44.8	40.0	328	1.22	–	–	–

The density of tendon was assumed to be 1220 kg m⁻³ (Ker, 1981) and volume was estimated from mass using this value. Tendon rest length was measured from the muscle–tendon junction to the point of insertion and then tendon cross-sectional area (CSA) was estimated by dividing tendon volume by tendon length. Tendon strain was estimated by dividing tendon stress (muscle F_max/tendon CSA) by the Young's Modulus of tendon (1500 MPa; Bennet et al. 1986; Ker et al. 1988). Tendon length change was estimated from the product of tendon rest length and tendon strain, and normalised by mean muscle fascicle length (Table 4) to provide an estimate of MTU stiffness.