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Three-dimensional ankle moments and nonlinear summation of rat triceps surae muscles.

Tijs C, van Dieën JH, Baan GC, Maas H - PLoS ONE (2014)

Bottom Line: The aims were (i) to assess effects of sagittal plane ankle angle (varied between 150° and 70°) on isometric ankle moments, in both magnitude and direction, exerted by active rat triceps surae muscles, (ii) to assess ankle moment summation between those muscles for a range of ankle angles and (iii) to assess effects of sagittal plane ankle angle and muscle activation on Achilles tendon length.SO moment direction in the frontal and sagittal planes were significantly different from that of GA.The limited degree of nonlinear summation may be explained by different mechanisms acting in opposite directions.

View Article: PubMed Central - PubMed

Affiliation: MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands.

ABSTRACT
The Achilles tendon and epimuscular connective tissues mechanically link the triceps surae muscles. These pathways may cause joint moments exerted by each muscle individually not to sum linearly, both in magnitude and direction. The aims were (i) to assess effects of sagittal plane ankle angle (varied between 150° and 70°) on isometric ankle moments, in both magnitude and direction, exerted by active rat triceps surae muscles, (ii) to assess ankle moment summation between those muscles for a range of ankle angles and (iii) to assess effects of sagittal plane ankle angle and muscle activation on Achilles tendon length. At each ankle angle, soleus (SO) and gastrocnemius (GA) muscles were first excited separately to assess ankle-angle moment characteristics and subsequently both muscles were excited simultaneously to investigate moment summation. The magnitude of ankle moment exerted by SO and GA, the SO direction in the transverse and sagittal planes, and the GA direction in the transverse plane were significantly affected by ankle angle. SO moment direction in the frontal and sagittal planes were significantly different from that of GA. Nonlinear magnitude summation varied between 0.6±2.9% and -3.6±2.9%, while the nonlinear direction summation varied between 0.3±0.4° and -0.4±0.7° in the transverse plane, between 0.5±0.4° and 0.1±0.4° in the frontal plane, and between 3.0±7.9° and 0.3±2.3° in the sagittal plane. Changes in tendon length caused by SO contraction were significantly lower than those during contraction of GA and GA+SO simultaneously. Thus, moments exerted by GA and SO sum nonlinearly both in the magnitude and direction. The limited degree of nonlinear summation may be explained by different mechanisms acting in opposite directions.

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Effect of muscle activation on the length changes of the shared distal portion of the Achilles tendon.Changes in Achilles tendon length (ΔLAT) in response to simultaneous contraction of GA+SO (Δ), and to individual contraction of SO (•) and GA (▪) are plotted as a function of sagittal plane ankle angle. Knee angle was kept constant at 90°. Effects of ankle angle were found for SO, GA and GA+SO (p<0.001). Length changes due to SO contraction were lower than length changes due to GA (p = 0.033) and GA+SO (p = 0.028) contraction. No differences were found between GA and GA+SO contractions (p = 1.000). Means ± s.d. are shown (n = 10).
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pone-0111595-g007: Effect of muscle activation on the length changes of the shared distal portion of the Achilles tendon.Changes in Achilles tendon length (ΔLAT) in response to simultaneous contraction of GA+SO (Δ), and to individual contraction of SO (•) and GA (▪) are plotted as a function of sagittal plane ankle angle. Knee angle was kept constant at 90°. Effects of ankle angle were found for SO, GA and GA+SO (p<0.001). Length changes due to SO contraction were lower than length changes due to GA (p = 0.033) and GA+SO (p = 0.028) contraction. No differences were found between GA and GA+SO contractions (p = 1.000). Means ± s.d. are shown (n = 10).

Mentions: We found that length changes in response to SO, GA, and GA+SO muscle contractions (Fig. 7) were significantly affected by ankle angle (p<0.001). Changes in length caused by SO contraction were significantly lower than those during contraction of GA (p = 0.033) and GA+SO (p = 0.028). However, no significant differences were found between GA and GA+SO contractions (p = 1.000). In addition, no significant interaction effects were found (p = 0.148). Achilles tendon length changes in response to muscle contraction were highest at the most plantar-flexed ankle angle (i.e., lowest triceps surae muscle length). Changes in Achilles tendon length were rather constant between 130° and 70°, being 0.17±0.14 mm and 0.15±0.13 mm in response to GA and GA+SO contraction, respectively, but negligible (0.01±0.16 mm) in response to SO contraction. These results indicate that the distal portion of Achilles tendon was lengthened more during simultaneous GA+SO contraction than during contraction of SO exclusively.


Three-dimensional ankle moments and nonlinear summation of rat triceps surae muscles.

Tijs C, van Dieën JH, Baan GC, Maas H - PLoS ONE (2014)

Effect of muscle activation on the length changes of the shared distal portion of the Achilles tendon.Changes in Achilles tendon length (ΔLAT) in response to simultaneous contraction of GA+SO (Δ), and to individual contraction of SO (•) and GA (▪) are plotted as a function of sagittal plane ankle angle. Knee angle was kept constant at 90°. Effects of ankle angle were found for SO, GA and GA+SO (p<0.001). Length changes due to SO contraction were lower than length changes due to GA (p = 0.033) and GA+SO (p = 0.028) contraction. No differences were found between GA and GA+SO contractions (p = 1.000). Means ± s.d. are shown (n = 10).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4216100&req=5

pone-0111595-g007: Effect of muscle activation on the length changes of the shared distal portion of the Achilles tendon.Changes in Achilles tendon length (ΔLAT) in response to simultaneous contraction of GA+SO (Δ), and to individual contraction of SO (•) and GA (▪) are plotted as a function of sagittal plane ankle angle. Knee angle was kept constant at 90°. Effects of ankle angle were found for SO, GA and GA+SO (p<0.001). Length changes due to SO contraction were lower than length changes due to GA (p = 0.033) and GA+SO (p = 0.028) contraction. No differences were found between GA and GA+SO contractions (p = 1.000). Means ± s.d. are shown (n = 10).
Mentions: We found that length changes in response to SO, GA, and GA+SO muscle contractions (Fig. 7) were significantly affected by ankle angle (p<0.001). Changes in length caused by SO contraction were significantly lower than those during contraction of GA (p = 0.033) and GA+SO (p = 0.028). However, no significant differences were found between GA and GA+SO contractions (p = 1.000). In addition, no significant interaction effects were found (p = 0.148). Achilles tendon length changes in response to muscle contraction were highest at the most plantar-flexed ankle angle (i.e., lowest triceps surae muscle length). Changes in Achilles tendon length were rather constant between 130° and 70°, being 0.17±0.14 mm and 0.15±0.13 mm in response to GA and GA+SO contraction, respectively, but negligible (0.01±0.16 mm) in response to SO contraction. These results indicate that the distal portion of Achilles tendon was lengthened more during simultaneous GA+SO contraction than during contraction of SO exclusively.

Bottom Line: The aims were (i) to assess effects of sagittal plane ankle angle (varied between 150° and 70°) on isometric ankle moments, in both magnitude and direction, exerted by active rat triceps surae muscles, (ii) to assess ankle moment summation between those muscles for a range of ankle angles and (iii) to assess effects of sagittal plane ankle angle and muscle activation on Achilles tendon length.SO moment direction in the frontal and sagittal planes were significantly different from that of GA.The limited degree of nonlinear summation may be explained by different mechanisms acting in opposite directions.

View Article: PubMed Central - PubMed

Affiliation: MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands.

ABSTRACT
The Achilles tendon and epimuscular connective tissues mechanically link the triceps surae muscles. These pathways may cause joint moments exerted by each muscle individually not to sum linearly, both in magnitude and direction. The aims were (i) to assess effects of sagittal plane ankle angle (varied between 150° and 70°) on isometric ankle moments, in both magnitude and direction, exerted by active rat triceps surae muscles, (ii) to assess ankle moment summation between those muscles for a range of ankle angles and (iii) to assess effects of sagittal plane ankle angle and muscle activation on Achilles tendon length. At each ankle angle, soleus (SO) and gastrocnemius (GA) muscles were first excited separately to assess ankle-angle moment characteristics and subsequently both muscles were excited simultaneously to investigate moment summation. The magnitude of ankle moment exerted by SO and GA, the SO direction in the transverse and sagittal planes, and the GA direction in the transverse plane were significantly affected by ankle angle. SO moment direction in the frontal and sagittal planes were significantly different from that of GA. Nonlinear magnitude summation varied between 0.6±2.9% and -3.6±2.9%, while the nonlinear direction summation varied between 0.3±0.4° and -0.4±0.7° in the transverse plane, between 0.5±0.4° and 0.1±0.4° in the frontal plane, and between 3.0±7.9° and 0.3±2.3° in the sagittal plane. Changes in tendon length caused by SO contraction were significantly lower than those during contraction of GA and GA+SO simultaneously. Thus, moments exerted by GA and SO sum nonlinearly both in the magnitude and direction. The limited degree of nonlinear summation may be explained by different mechanisms acting in opposite directions.

Show MeSH
Related in: MedlinePlus