architectural correlates of locomotion in the hindlimb muscles of two guenon species

Architectural Correlates of Locomotion in the Hindlimb

Muscles of Two Guenon Species

Architectural Correlates of Locomotion in the Hindlimb

Muscles of Two Guenon Species

IntroductionIntroduction The investigation: can muscle architectural The investigation: can muscle architectural

differences be recognized as the correlates differences be recognized as the correlates of particular locomotor habits?of particular locomotor habits?

Muscle ArchitectureMuscle Architecture

The Species:The Species:

Cercopithecus aethiops C. ascanius

Muscles of the HindlimbMuscles of the Hindlimb

Gluteal groupGluteal group Gluteus superficialisGluteus superficialis Gluteus mediusGluteus medius Gluteus minimusGluteus minimus

HamstringsHamstrings Biceps femorisBiceps femoris Semi-membranosusSemi-membranosus Semi-tendinosusSemi-tendinosus

Morphometrics Morphometrics Length of the fasciculus between Length of the fasciculus between

the proximal myotendinous junction the proximal myotendinous junction and the distal myotendinous and the distal myotendinous junction (lf) junction (lf)

The perpendicular distance from the The perpendicular distance from the tendon of insertion to the proximal tendon of insertion to the proximal attachment of fasciculus (a) attachment of fasciculus (a)

Length of tendon from the proximal Length of tendon from the proximal attachment (tp )attachment (tp )

Length of the tendon of distal Length of the tendon of distal attachment (td)attachment (td)

Sarcomere LengthsSarcomere Lengths

Angles of Pinnation Angles of Pinnation

Variables Calculated to Estimate Output Potential of the MusclesVariables Calculated to Estimate Output Potential of the Muscles

Reduced physiological cross-sectional area Reduced physiological cross-sectional area RPCA (sq cms) = (mass x cos RPCA (sq cms) = (mass x cos / lf (cms) x specific density/ lf (cms) x specific density

Mass/predicted effective maximal tetanic tension Mass/predicted effective maximal tetanic tension m/po, where po m/po, where po 2.3 newtons x RPCA 2.3 newtons x RPCA

Estimated maximum excursion of distal tendon of Estimated maximum excursion of distal tendon of attachmentattachment h = lf (cos h = lf (cos - ( - (cos cos + n + n22 - 1) - 1)

Tendon length/fasciculus length+tendon length Tendon length/fasciculus length+tendon length lt/lf + ltlt/lf + lt

0

5

10

15

20

25

30

Gluteussuperficialis

anterior

Gluteussuperficialis

posterior

Gluteusmedius

Gluteusminimus

BicepsFemoris

Semimem-branosus

Semi-tendinosus

Vervets

Red-tails

Mass/poMass/po

Estimated ExcursionEstimated Excursion

0

5

10

15

20

25

30

Gluteussuperficialis

anterior

Gluteussuperficialis

posterior

Gluteusmedius

Gluteusminimus

BicepsFemoris

Semimem-branosus

Semi-tendinosus

Vervets

Red-tails

Tendon PercentageTendon Percentage

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Gluteussuperficialis

anterior

Gluteussuperficialis

posterior

Gluteusmedius

Gluteusminimus

BicepsFemoris

Semimem-branosus

Semi-tendinosus

Vervets

Red-tails

RpcaRpca

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Gluteussuperficialis

anterior

Gluteussuperficialis

posterior

Gluteusmedius

Gluteusminimus

BicepsFemoris

Semimem-branosus

Semi-tendinosus

Vervets

Red-tails

•Conclusions•Conclusions Between group differences:Between group differences: intermuscular variability intermuscular variability

greater among gluteal muscles than among hamstrings.greater among gluteal muscles than among hamstrings.

Interspecific differences:Interspecific differences: - Higher relative values for RPCA of gluteus medius than - Higher relative values for RPCA of gluteus medius than

g. Minimus in vervets related to demands of ground g. Minimus in vervets related to demands of ground quadrupedalism. quadrupedalism.

- In vervets muscles are designed for higher velocities, - In vervets muscles are designed for higher velocities, but greater force generation in red-tails.but greater force generation in red-tails.

- Vervet muscles designed more for isotonic contraction, - Vervet muscles designed more for isotonic contraction, by contrast to more isometric use in red-tails.by contrast to more isometric use in red-tails.