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First published online June 29, 2007
Journal of Experimental Biology 210, 2510-2517 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.003913
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Muscle strain is modulated more with running slope than speed in wild turkey knee and hip extensors

Thomas J. Roberts1,*, Brian K. Higginson2, Frank E. Nelson3 and Annette M. Gabaldón4

1 Brown University, Ecology and Evolutionary Biology Department, Box GB205, Providence, RI 02912, USA
2 Oregon State University, Department of Exercise and Sport Science, 15 Womens Building, Corvallis, OR 97331, USA
3 Institute of Integrative and Comparative Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
4 Colorado State University-Pueblo, Biology Department, Pueblo, CO 81001, USA


Figure 1
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  		Fig. 1. Lateral views of the iliotibialis lateralis postacetabularis (A) and, with the iliolotibialis reflected (B), the femorotibilialis. The iliotibialis lateralis postacetabularis acts as a knee and hip extensor. The femorotibialis has a broad origin on the femur and is a knee extensor. Approximate location of sonomicrometer crystals are indicated.

 

Figure 2
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  		Fig. 2. Representative fascicle length and EMG for the ILPO (A) and the FT (B) for one individual running at 2 m s–1 on the level. Shaded areas represent stance. Muscle lengths are presented as a fraction of Lo, calculated as the average muscle length over a stride. Broken lines on the third stride indicate the period of stance lengthening (L) and shortening (S) for which all measurements in this study were taken.

 

Figure 3
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  		Fig. 3. Representative fascicle lengths and EMG for the ILPO during 12° uphill (A), level (B) and 12° downhill (C) running at 2 m s–1. Shaded areas indicate stance phase. The trend towards increased shortening and decreased lengthening as slope increases is apparent in these sample strides. Data shown are for a different individual than depicted in Fig. 2.

 

Figure 4
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  		Fig. 4. Representative fascicle lengths and EMG for the FT during 12° uphill (A), level (B) and 12° downhill (C) running at 2 m s–1. Shaded areas indicate stance phase. Data shown are for a different individual than depicted in Fig. 2.

 

Figure 5
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  		Fig. 5. Strain during shortening (grey) and lengthening (black) for the ILPO (A) and the FT (B). With increases in slope, shortening strain increased and lengthening strain decreased. There was a significant effect of slope on shortening and lengthening strain for both muscles.

 

Figure 6
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  		Fig. 6. Average fascicle velocity during shortening (grey) and lengthening (black) for the ILPO (A) and the FT (B). With increases in slope, shortening velocity increased and lengthening velocity decreased.

 

Figure 7
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  		Fig. 7. Timing of EMG activity, measured as the fraction of the stance phase taken to develop one-half of the rectified integrated EMG signal (t50%EMG) for the ILPO (A) and the FT (B).

 

Figure 8
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  		Fig. 8. Relative time spent shortening (grey) and lengthening (black), expressed as a proportion of the total time of the lengthen–shorten cycle of the ILPO (A) and the FT (B). Relatively more time was spent shortening as the demand for mechanical work increased with increasing slope.

 

Figure 9
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  		Fig. 9. Shortening (grey) and lengthening (black) strains for the ILPO (A) and the FT (B). There was no significant relationship between shortening strain and running speed. Lengthening strain for the FT was the only variable significantly affected by running speed.

 

Figure 10
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  		Fig. 10. Velocities of shortening (grey) and lengthening (black) were significantly correlated with running speed for both the ILPO (A) and the FT (B).

 

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© The Company of Biologists Ltd 2007