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Function of a large biarticular hip and knee extensor during walking and running in guinea fowl (Numida meleagris)
- Source :
- The Journal of experimental biology. 214(Pt 20)
- Publication Year :
- 2011
-
Abstract
- SUMMARYPhysiological and anatomical evidence suggests that in birds the iliotibialis lateralis pars postacetabularis (ILPO) is functionally important for running. Incorporating regional information, we estimated the mean sarcomere strain trajectory and electromyographic (EMG) amplitude of the ILPO during level and incline walking and running. Using these data and data in the literature of muscle energy use, we examined three hypotheses: (1) active lengthening will occur on the ascending limb of the length–tension curve to avoid potential damage caused by stretch on the descending limb; (2) the active strain cycle will shift to favor active shortening when the birds run uphill and shortening will occur on the plateau and shallow ascending limb of the length–tension curve; and (3) measures of EMG intensity will correlate with energy use when the mechanical function of the muscle is similar. Supporting the first hypothesis, we found that the mean sarcomere lengths at the end of active lengthening during level locomotion were smaller than the predicted length at the start of the plateau of the length–tension curve. Supporting the second hypothesis, the magnitude of active lengthening decreased with increasing slope, whereas active shortening increased. In evaluating the relationship between EMG amplitude and energy use (hypothesis 3), we found that although increases in EMG intensity with speed, slope and loading were positively correlated with muscle energy use, the quantitative relationships between these variables differed greatly under different conditions. The relative changes in EMG intensity and energy use by the muscle probably varied because of changes in the mechanical function of the muscle that altered the ratio of muscle energy use to active muscle volume. Considering the overall function of the cycle of active lengthening and shortening of the fascicles of the ILPO, we conclude that the function of active lengthening is unlikely to be energy conservation and may instead be related to promoting stability at the knee. The work required to lengthen the ILPO during stance is provided by co-contracting knee flexors. We suggest that this potentially energetically expensive co-contraction serves to stabilize the knee in early stance by increasing the mechanical impedance of the joint.
- Subjects :
- Sarcomeres
medicine.medical_specialty
Physiology
Strain (injury)
Muscle Energy
Electromyography
Walking
Aquatic Science
Biology
Sarcomere
Models, Biological
Running
Physical medicine and rehabilitation
Physical Conditioning, Animal
medicine
Animals
Galliformes
Muscle, Skeletal
Molecular Biology
Ecology, Evolution, Behavior and Systematics
Research Articles
Analysis of Variance
Hip
medicine.diagnostic_test
Work (physics)
Biomechanics
Anatomy
medicine.disease
Intensity (physics)
Biomechanical Phenomena
Hindlimb
Regional Blood Flow
Insect Science
Animal Science and Zoology
Joints
medicine.symptom
Muscle contraction
Muscle Contraction
Subjects
Details
- ISSN :
- 14779145
- Volume :
- 214
- Issue :
- Pt 20
- Database :
- OpenAIRE
- Journal :
- The Journal of experimental biology
- Accession number :
- edsair.doi.dedup.....06d2c5d606ca7940588ed4f4327dc463