1
|
Holt NC, Mayfield DL. Muscle-tendon unit design and tuning for power enhancement, power attenuation, and reduction of metabolic cost. J Biomech 2023; 153:111585. [PMID: 37126884 PMCID: PMC10949972 DOI: 10.1016/j.jbiomech.2023.111585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 04/06/2023] [Indexed: 05/03/2023]
Abstract
The contractile elements in skeletal muscle fibers operate in series with elastic elements, tendons and potentially aponeuroses, in muscle-tendon units (MTUs). Elastic strain energy (ESE), arising from either work done by muscle fibers or the energy of the body, can be stored in these series elastic elements (SEEs). MTUs vary considerably in their design in terms of the relative lengths and stiffnesses of the muscle fibers and SEEs, and the force and work generating capacities of the muscle fibers. However, within an MTU it is thought that contractile and series elastic elements can be matched or tuned to maximize ESE storage. The use of ESE is thought to improve locomotor performance by enhancing contractile element power during activities such as jumping, attenuating contractile element power during activities such as landing, and reducing the metabolic cost of movement during steady-state activities such as walking and running. The effectiveness of MTUs in these potential roles is contingent on factors such as the source of mechanical energy, the control of the flow of energy, and characteristics of SEE recoil. Hence, we suggest that MTUs specialized for ESE storage may vary considerably in the structural, mechanical, and physiological properties of their components depending on their functional role and required versatility.
Collapse
Affiliation(s)
- N C Holt
- Department of Evolution, Ecology and Organismal Biology, University of California Riverside, 900 University Avenue, Riverside, CA 92521, USA.
| | - D L Mayfield
- Department of Evolution, Ecology and Organismal Biology, University of California Riverside, 900 University Avenue, Riverside, CA 92521, USA
| |
Collapse
|
2
|
Thornton LH, Dick TJM, Bennett MB, Clemente CJ. Understanding Australia’s unique hopping species: a comparative review of the musculoskeletal system and locomotor biomechanics in Macropodoidea. AUST J ZOOL 2022. [DOI: 10.1071/zo21048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Kangaroos and other macropodoids stand out among mammals for their unusual hopping locomotion and body shape. This review examines the scaling of hind- and forelimb bones, and the primary ankle extensor muscles and tendons. We find that the scaling of the musculoskeletal system is sensitive to the phylogenetic context. Tibia length increases with positive allometry among most macropodoids, but negative allometry in eastern grey kangaroos and isometry in red kangaroos. Femur length decreases with stronger negative allometry in eastern grey and red kangaroos than among other macropodoids. Muscle masses scale with negative allometry in western grey kangaroos and with isometry in red kangaroos, compared to positive allometry in other macropodoids. We further summarise the work on the hopping gait, energetics in macropodoids, and stresses in the musculoskeletal system in an evolutionary context, to determine what trade-offs may limit locomotor performance in macropodoids. When large kangaroos hop, they do not increase oxygen consumption with speed, unlike most mammals, including small hopping species. We conclude that there is not enough information to isolate the biomechanical factors that make large kangaroos so energy efficient. We identify key areas for further research to fill these gaps.
Collapse
|
3
|
Cetik RM, Yabanoglu Ciftci S, Arica B, Baysal I, Akarca Dizakar SO, Erbay Elibol FK, Gencer A, Demir T, Ayvaz M. Evaluation of the Effects of Transforming Growth Factor-Beta 3 (TGF-β3) Loaded Nanoparticles on Healing in a Rat Achilles Tendon Injury Model. Am J Sports Med 2022; 50:1066-1077. [PMID: 35188807 DOI: 10.1177/03635465211073148] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND Achilles tendon (AT) midsubstance injuries may heal suboptimally, especially in athletes. Transforming growth factor-beta 3 (TGF-β3) shows promise because of its recently discovered tendinogenic effects. Using poly(lactic-co-glycolic acid)-b-poly(ethylene glycol) (PLGA-b-PEG) nanoparticles (NPs) may enhance the results by a sustained-release effect. HYPOTHESIS The application of TGF-β3 will enhance AT midsubstance healing, and the NP form will achieve better outcomes. STUDY DESIGN Controlled laboratory study. METHODS A total of 80 rats underwent unilateral AT transection and were divided into 4 groups: (1) control (C); (2) empty chitosan film (Ch); (3) chitosan film containing free TGF-β3 (ChT); and (4) chitosan film containing TGF-β3-loaded NPs (ChN). The animals were sacrificed at 3 and 6 weeks. Tendons were evaluated for morphology (length and cross-sectional area [CSA]), biomechanics (maximum load, stress, stiffness, and elastic modulus), histology, immunohistochemical quantification (types I and III collagen [COL1 and COL3]), and gene expression (COL1A1, COL3A1, scleraxis, and tenomodulin). RESULTS Morphologically, at 3 weeks, ChT (15 ± 2.7 mm) and ChN (15.6 ± 1.6 mm) were shorter than C (17.6 ± 1.8 mm) (P = .019 and = .004, respectively). At 6 weeks, the mean CSA of ChN (10.4 ± 1.9 mm2) was similar to that of intact tendons (6.4 ± 1.1 mm2) (P = .230), while the other groups were larger. Biomechanically, at 3 weeks, ChT (42.8 ± 4.9 N) had a higher maximum load than C (27 ± 9.1 N; P = .004) and Ch (29.2 ± 5.7 N; P = .005). At 6 weeks, ChN (26.9 ± 3.9 MPa) had similar maximum stress when compared with intact tendons (34.1 ± 7.8 MPa) (P = .121); the other groups were significantly lower. Histologically, at 6 weeks, the mean Movin score of ChN (4.5 ± 1.5) was lower than that of ChT (6.3 ± 1.8). Immunohistochemically, ChN had higher COL3 (1.469 ± 0.514) at 3 weeks and lower COL1 (1.129 ± 0.368) at 6 weeks. COL1A1 gene expression was higher in ChT and ChN at 3 weeks, but COL3A1 gene expression was higher in ChN. CONCLUSION The application of TGF-β3 had a positive effect on AT midsubstance healing, and the sustained-release NP form improved the outcomes, more specifically accelerating the remodeling process. CLINICAL RELEVANCE This study demonstrated the effectiveness of TGF-β3 on tendon healing on a rat model, which is an important step toward clinical use. The novel method of using PLGA-b-PEG NPs as a drug-delivery system with sustained-release properties had promising results.
Collapse
Affiliation(s)
- Riza Mert Cetik
- Hacettepe University Faculty of Medicine, Department of Orthopedics and Traumatology, Ankara, Turkey
| | | | - Betul Arica
- Hacettepe University Faculty of Pharmacy, Department of Pharmaceutical Technology, Ankara, Turkey
| | - Ipek Baysal
- Hacettepe University Vocational School of Health Services, Ankara, Turkey
| | | | - Fatma Kubra Erbay Elibol
- TOBB ETÜ University of Economics and Technology, Department of Biomedical Engineering, Ankara, Turkey
| | - Ayse Gencer
- Hacettepe University Faculty of Pharmacy, Department of Pharmaceutical Technology, Ankara, Turkey
| | - Teyfik Demir
- TOBB ETÜ University of Economics and Technology, Department of Mechanical Engineering, Ankara, Turkey
| | - Mehmet Ayvaz
- Hacettepe University Faculty of Medicine, Department of Orthopedics and Traumatology, Ankara, Turkey
| |
Collapse
|
4
|
Freymiller GA, Whitford MD, Schwaner MJ, McGowan CP, Higham TE, Clark RW. Comparative analysis of Dipodomys species indicates that kangaroo rat hindlimb anatomy is adapted for rapid evasive leaping. J Anat 2022; 240:466-474. [PMID: 34648184 PMCID: PMC8819043 DOI: 10.1111/joa.13567] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 10/02/2021] [Accepted: 10/04/2021] [Indexed: 11/27/2022] Open
Abstract
Body size is a key factor that influences antipredator behavior. For animals that rely on jumping to escape from predators, there is a theoretical trade-off between jump distance and acceleration as body size changes at both the inter- and intraspecific levels. Assuming geometric similarity, acceleration will decrease with increasing body size due to a smaller increase in muscle cross-sectional area than body mass. Smaller animals will likely have a similar jump distance as larger animals due to their shorter limbs and faster accelerations. Therefore, in order to maintain acceleration in a jump across different body sizes, hind limbs must be disproportionately bigger for larger animals. We explored this prediction using four species of kangaroo rats (Dipodomys spp.), a genus of bipedal rodent with similar morphology across a range of body sizes (40-150 g). Kangaroo rat jump performance was measured by simulating snake strikes to free-ranging individuals. Additionally, morphological measurements of hind limb muscles and segment lengths were obtained from thawed frozen specimens. Overall, jump acceleration was constant across body sizes and jump distance increased with increasing size. Additionally, kangaroo rat hind limb muscle mass and cross-sectional area scaled with positive allometry. Ankle extensor tendon cross-sectional area also scaled with positive allometry. Hind limb segment length scaled isometrically, with the exception of the metatarsals, which scaled with negative allometry. Overall, these findings support the hypothesis that kangaroo rat hind limbs are built to maintain jump acceleration rather than jump distance. Selective pressure from single-strike predators, such as snakes and owls, likely drives this relationship.
Collapse
Affiliation(s)
- Grace A. Freymiller
- Department of BiologySan Diego State UniversitySan DiegoCaliforniaUSA
- Department of Evolution, Ecology, and Organismal BiologyUniversity of CaliforniaRiversideCaliforniaUSA
| | - Malachi D. Whitford
- Department of BiologySan Diego State UniversitySan DiegoCaliforniaUSA
- Graduate Group in EcologyUniversity of CaliforniaDavisCaliforniaUSA
| | - M. Janneke Schwaner
- Department of Ecology and Evolutionary BiologyUniversity of CaliforniaIrvineCaliforniaUSA
| | - Craig P. McGowan
- Keck School of MedicineUniversity of Southern CaliforniaLos AngelesCaliforniaUSA
| | - Timothy E. Higham
- Department of Evolution, Ecology, and Organismal BiologyUniversity of CaliforniaRiversideCaliforniaUSA
| | - Rulon W. Clark
- Department of BiologySan Diego State UniversitySan DiegoCaliforniaUSA
- Chiricahua Desert MuseumRodeoNew MexicoUSA
| |
Collapse
|
5
|
Christensen BA, Lin DC, Schwaner MJ, McGowan CP. Elastic energy storage across speeds during steady-state hopping of desert kangaroo rats (Dipodomys deserti). J Exp Biol 2022; 225:273978. [PMID: 35019972 DOI: 10.1242/jeb.242954] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 12/30/2021] [Indexed: 11/20/2022]
Abstract
Small bipedal hoppers, including kangaroo rats, are thought to not benefit from substantial elastic energy storage and return during hopping. However, recent species-specific material properties research suggests that, despite relative thickness, the ankle extensor tendons of these small hoppers are considerably more compliant than had been assumed. With faster locomotor speeds demanding higher forces, a lower tendon stiffness suggests greater tendon deformation and thus a greater potential for elastic energy storage and return with increasing speed. Using the elastic modulus values specific to kangaroo rat tendons, we sought to determine how much elastic energy is stored and returned during hopping across a range of speeds. In vivo techniques were used to record tendon force in the ankle extensors during steady-speed hopping. Our data support the hypothesis that the ankle extensor tendons of kangaroo rats store and return elastic energy in relation to hopping speed, storing more at faster speeds. Despite storing comparatively less elastic energy than larger hoppers, this relationship between speed and energy storage offer novel evidence of a functionally similar energy storage mechanism, operating irrespective of body size or tendon thickness, across the distal muscle-tendon units of both small and large bipedal hoppers.
Collapse
Affiliation(s)
- Brooke A Christensen
- Department of Biological Sciences, University of Idaho, Moscow ID, USA.,Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine CA, USA
| | - David C Lin
- Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman WA, USA.,Department of Integrative Physiology and Neuroscience, Washington State University, Pullman WA, USA.,Washington Center for Muscle Biology, Washington State University, Pullman WA, USA
| | - M Janneke Schwaner
- Department of Biological Sciences, University of Idaho, Moscow ID, USA.,Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine CA, USA
| | - Craig P McGowan
- Department of Biological Sciences, University of Idaho, Moscow ID, USA.,Washington Center for Muscle Biology, Washington State University, Pullman WA, USA.,Keck School of Medicine of the University of Southern California, Los Angeles CA, USA
| |
Collapse
|
6
|
Schwaner MJ, Lin DC, McGowan CP. Plantar flexor muscles of kangaroo rats (Dipodomys deserti) shorten at a velocity to produce optimal power during jumping. J Exp Biol 2021; 224:273832. [PMID: 34870703 DOI: 10.1242/jeb.242630] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 11/24/2021] [Indexed: 11/20/2022]
Abstract
The musculotendon work contributions across all joints during jumping by kangaroo rats are not well understood. Namely, measures of external joint work do not provide information on the contributions from individual muscles or in-series elastic structures. In this study, we examined the functional roles of a major ankle extensor muscle, the lateral gastrocnemius (LG), and a major knee extensor muscle, the vastus lateralis (VL), through in vivo sonomicrometry and electromyography techniques, during vertical jumping by kangaroo rats. Our data showed that both muscles increased shortening and activity with higher jumps. We found that knee angular velocity and VL muscle shortening velocity were coupled in time. In contrast, the ankle angular velocity and LG muscle shortening velocity were decoupled, and rapid joint extension near the end of the jump produced high power outputs at the ankle joint. Further, the decoupling of muscle and joint kinematics allowed the LG muscle to prolong the period of shortening velocity near optimal velocity, which likely enabled the muscle to sustain maximal power generation. These observations were consistent with an LG tendon that is much more compliant than that of the VL.
Collapse
Affiliation(s)
- M Janneke Schwaner
- Department of Biological Sciences, University of Idaho, Moscow, ID 83844, USA
| | - David C Lin
- Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA.,Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA 99164, USA.,Washington Center for Muscle Biology, Washington State University, Pullman, WA 99164, USA
| | - Craig P McGowan
- Department of Biological Sciences, University of Idaho, Moscow, ID 83844, USA.,Washington Center for Muscle Biology, Washington State University, Pullman, WA 99164, USA.,WWAMI Medical Education Program, Moscow, ID 83844, USA
| |
Collapse
|
7
|
Ross CD, Meyers RA. Immunohistochemistry of kangaroo rat hindlimb muscles. Anat Rec (Hoboken) 2021; 305:1435-1447. [PMID: 34605198 DOI: 10.1002/ar.24791] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 08/19/2021] [Accepted: 09/08/2021] [Indexed: 12/20/2022]
Abstract
Kangaroo rats (Dipodomys spp.) use specialized bipedal hopping like that of kangaroos. In contrast to kangaroos that have elastic tendons capable of storing energy, kangaroo rats have inelastic tendons that are unable to store large amounts of energy. Thus, the musculature of the ankle joint provides the greatest power contribution to kangaroo rat hopping. Skeletal muscle can be characterized by several fiber types, including slow twitch (Type I) and fast twitch (Type II) fibers. Fast fibers are found in higher concentration in muscles that perform quick, dynamic movements, whereas slow fibers are found in higher proportion in muscles that perform slow, endurant movements. Using fiber type specific antibodies, we identified four pure (Types I, IIA, IIB, and IIX) and two hybrid (Types I/IIA and IIA/IIX) fiber types in six hindlimb muscles from three kangaroo rats (Dipodomys merriami) to investigate the relationship between fiber composition and hindlimb muscle function. Hindlimb muscles (except soleus) were dominated by Type IIB fibers, which were largest in cross-sectional area, and are known to be best suited for rapid and explosive movements. Oxidative Type IIA and Type IIX fibers were found at moderate concentrations and likely function in maintaining continual saltatory locomotion. Thus, kangaroo rats can use these two fiber type populations as "gears" for both endurant and explosive behaviors.
Collapse
Affiliation(s)
- Chanel D Ross
- Department of Zoology, Weber State University, Ogden, Utah, USA
| | - Ron A Meyers
- Department of Zoology, Weber State University, Ogden, Utah, USA
| |
Collapse
|
8
|
Theodossiou SK, Pancheri NM, Martes AC, Bozeman AL, Brumley MR, Raveling AR, Courtright JM, Schiele NR. Neonatal Spinal Cord Transection Decreases Hindlimb Weight-Bearing and Affects Formation of Achilles and Tail Tendons. J Biomech Eng 2021; 143:061012. [PMID: 33537729 PMCID: PMC8114905 DOI: 10.1115/1.4050031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 01/06/2021] [Indexed: 01/08/2023]
Abstract
Mechanical loading may be required for proper tendon formation. However, it is not well understood how tendon formation is impacted by the development of weight-bearing locomotor activity in the neonate. This study assessed tendon mechanical properties, and concomitant changes in weight-bearing locomotion, in neonatal rats subjected to a low thoracic spinal cord transection or a sham surgery at postnatal day (P)1. On P10, spontaneous locomotion was evaluated in spinal cord transected and sham controls to determine impacts on weight-bearing hindlimb movement. The mechanical properties of P10 Achilles tendons (ATs), as representative energy-storing, weight-bearing tendons, and tail tendons (TTs), as representative positional, non-weight-bearing tendons were evaluated. Non- and partial weight-bearing hindlimb activity decreased in spinal cord transected rats compared to sham controls. No spinal cord transected rats showed full weight-bearing locomotion. ATs from spinal cord transected rats had increased elastic modulus, while cross-sectional area trended lower compared to sham rats. TTs from spinal cord transected rats had higher stiffness and cross-sectional area. Collagen structure of ATs and TTs did not appear impacted by surgery condition, and no significant differences were detected in the collagen crimp pattern. Our findings suggest that mechanical loading from weight-bearing locomotor activity during development regulates neonatal AT lateral expansion and maintains tendon compliance, and that TTs may be differentially regulated. The onset and gradual increase of weight-bearing movement in the neonate may provide the mechanical loading needed to direct functional postnatal tendon formation.
Collapse
Affiliation(s)
- Sophia K. Theodossiou
- Biological Engineering, University of Idaho, 875 Perimeter Drive, MS 0904, Moscow, ID 83844
| | - Nicholas M. Pancheri
- Biological Engineering, University of Idaho, 875 Perimeter Drive, MS 0904, Moscow, ID 83844
| | - Alleyna C. Martes
- Psychology, Idaho State University, 921 South 8th Avenue Stop 8112, Pocatello, ID 83209
| | - Aimee L. Bozeman
- Psychology, Idaho State University, 921 South 8th Avenue Stop 8112, Pocatello, ID 83209
| | - Michele R. Brumley
- Psychology, Idaho State University, 921 South 8th Avenue Stop 8087, Pocatello, ID 83209
| | - Abigail R. Raveling
- Biological Engineering, University of Idaho, 875 Perimeter Drive, MS 0904, Moscow, ID 83844
| | - Jeffrey M. Courtright
- Biological Engineering, University of Idaho, 875 Perimeter Drive, MS 0904, Moscow, ID 83844
| | - Nathan R. Schiele
- Biological Engineering, University of Idaho, 875 Perimeter Drive, MS 0904, Moscow, ID 83844
| |
Collapse
|
9
|
Mossor AM, Austin BL, Avey-Arroyo JA, Butcher MT. A Horse of a Different Color?: Tensile Strength and Elasticity of Sloth Flexor Tendons. Integr Org Biol 2021; 2:obaa032. [PMID: 33796818 DOI: 10.1093/iob/obaa032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Tendons must be able to withstand the tensile forces generated by muscles to provide support while avoiding failure. The properties of tendons in mammal limbs must therefore be appropriate to accommodate a range of locomotor habits and posture. Tendon collagen composition provides resistance to loading that contributes to tissue strength which could, however, be modified to not exclusively confer large strength and stiffness for elastic energy storage/recovery. For example, sloths are nearly obligate suspenders and cannot run, and due to their combined low metabolic rate, body temperature, and rate of digestion, they have an extreme need to conserve energy. It is possible that sloths have a tendon "suspensory apparatus" functionally analogous to that in upright ungulates, thus allowing for largely passive support of their body weight below-branch, while concurrently minimizing muscle contractile energy expenditure. The digital flexor tendons from the fore- and hindlimbs of two-toed (Choloepus hoffmanni) and three-toed (Bradypus variegatus) sloths were loaded in tension until failure to test this hypothesis. Overall, tensile strength and elastic (Young's) modulus of sloth tendons were low, and these material properties were remarkably similar to those of equine suspensory "ligaments." The results also help explain previous findings in sloths showing relatively low levels of muscle activation in the digital flexors during postural suspension and suspensory walking.
Collapse
Affiliation(s)
- A M Mossor
- Department of Biological Sciences, Youngstown State University, Youngstown, OH USA
| | - B L Austin
- Department of Biological Sciences, Youngstown State University, Youngstown, OH USA
| | | | - M T Butcher
- Department of Biological Sciences, Youngstown State University, Youngstown, OH USA
| |
Collapse
|
10
|
Javidi M, McGowan CP, Lin DC. Estimation of the force-velocity properties of individual muscles from measurement of the combined plantarflexor properties. J Exp Biol 2020; 223:jeb219980. [PMID: 32680898 DOI: 10.1242/jeb.219980] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 07/13/2020] [Indexed: 11/20/2022]
Abstract
The force-velocity (F-V) properties of isolated muscles or muscle fibers have been well studied in humans and other animals. However, determining properties of individual muscles in vivo remains a challenge because muscles usually function within a synergistic group. Modeling has been used to estimate the properties of an individual muscle from the experimental measurement of the muscle group properties. While this approach can be valuable, the models and the associated predictions are difficult to validate. In this study, we measured the in situ F-V properties of the maximally activated kangaroo rat plantarflexor group and used two different assumptions and associated models to estimate the properties of the individual plantarflexors. The first model (Mdl1) assumed that the percent contributions of individual muscles to group force and power were based upon the muscles' cross-sectional area and were constant across the different isotonic loads applied to the muscle group. The second model (Mdl2) assumed that the F-V properties of the fibers within each muscle were identical, but because of differences in muscle architecture, the muscles' contributions to the group properties changed with isotonic load. We compared the two model predictions with independent estimates of the muscles' contributions based upon sonomicrometry measurements of muscle length. We found that predictions from Mdl2 were not significantly different from sonomicrometry-based estimates while those from Mdl1 were significantly different. The results of this study show that incorporating appropriate fiber properties and muscle architecture is necessary to parse the individual muscles' contributions to the group F-V properties.
Collapse
Affiliation(s)
- Mehrdad Javidi
- Voiland School of Chemical Engineering and Bioengineering, Washington State University, PO Box 646515, Pullman, WA 99164, USA
| | - Craig P McGowan
- Department of Biological Sciences, University of Idaho, 875 Perimeter Drive, MS 3051, Moscow, ID 83844, USA
- WWAMI Medical Education Program, University of Idaho, 875 Perimeter Drive, MS 4207, Moscow, ID 83844, USA
- Washington Center for Muscle Biology, Washington State University, PO Box 646515, Pullman, WA 99164, USA
| | - David C Lin
- Voiland School of Chemical Engineering and Bioengineering, Washington State University, PO Box 646515, Pullman, WA 99164, USA
- Washington Center for Muscle Biology, Washington State University, PO Box 646515, Pullman, WA 99164, USA
- Department of Integrative Physiology and Neuroscience, Washington State University, PO Box 647620, Pullman, WA 99164, USA
| |
Collapse
|
11
|
Konow N, Collias A, Biewener AA. Skeletal Muscle Shape Change in Relation to Varying Force Requirements Across Locomotor Conditions. Front Physiol 2020; 11:143. [PMID: 32265722 PMCID: PMC7100385 DOI: 10.3389/fphys.2020.00143] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2019] [Accepted: 02/11/2020] [Indexed: 12/11/2022] Open
Abstract
Contractions of skeletal muscles to generate in vivo movement involve dynamic changes in contractile and elastic tissue strains that likely interact to influence the force and work of a muscle. However, studies of the in vivo dynamics of skeletal muscle and tendon strains remain largely limited to bipedal animals, and rarely cover the broad spectra of movement requirements met by muscles that operate as motors, struts, or brakes across the various gaits that animals commonly use and conditions they encounter. Using high-speed bi-planar fluoromicrometry, we analyze in vivo strains within the rat medial gastrocnemius (MG) across a range of gait and slope conditions. These conditions require changes in muscle force ranging from decline walk (low) to incline gallop (high). Measurements are made from implanted (0.5–0.8 mm) tantalum spheres marking MG mid-belly width, mid-belly thickness, as well as strains of distal fascicles, the muscle belly, and the Achilles tendon. During stance, as the muscle contracts, muscle force increases linearly with respect to gait–slope combinations, and both shortening and lengthening fiber strains increase from approximately 5 to 15% resting length. Contractile change in muscle thickness (thickness strain) decreases (r2 = 0.86; p = 0.001); whereas, the change in muscle width (width strain) increases (r2 = 0.88; p = 0.001) and tendon strain increases (r2 = 0.77; p = 0.015). Our results demonstrate force-dependency of contractile and tendinous tissue strains with compensatory changes in shape for a key locomotor muscle in the hind limb of a small quadruped. These dynamic changes are linked to the ability of a muscle to tune its force and work output as requirements change with locomotor speed and environmental conditions.
Collapse
Affiliation(s)
- Nicolai Konow
- Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA, United States.,Concord Field Station, Department of Organismic and Evolutionary Biology, Harvard University, Bedford, MA, United States
| | - Alexandra Collias
- Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA, United States
| | - Andrew A Biewener
- Concord Field Station, Department of Organismic and Evolutionary Biology, Harvard University, Bedford, MA, United States
| |
Collapse
|