Hindlimb function in the alligator: integrating movements, motor patterns, ground reaction forces and bone strain of terrestrial locomotion

SUMMARY The function of the lateral hypaxial muscles during locomotion in tetrapods is controversial. Currently, there are two hypotheses of lateral hypaxial muscle function. The first, supported by electromyographic (EMG) data from a lizard (Iguana iguana) and a salamander (Dicamptodon ensatus), suggests that hypaxial muscles function to bend the body during swimming and to resist long-axis torsion during walking. The second, supported by EMG data from lizards during relatively high-speed locomotion, suggests that these muscles function primarily to bend the body during locomotion, not to resist torsional forces. To determine whether the results from D. ensatus hold for another salamander, we recorded lateral hypaxial muscle EMGs synchronized with body and limb kinematics in the tiger salamander Ambystoma tigrinum. In agreement with results from aquatic locomotion in D. ensatus, all four layers of lateral hypaxial musculature were found to show synchronous EMG activity during swimming in A. tigrinum. Our findings for terrestrial locomotion also agree with previous results from D. ensatus and support the torsion resistance hypothesis for terrestrial locomotion. We observed asynchronous EMG bursts of relatively high intensity in the lateral and medial pairs of hypaxial muscles during walking in tiger salamanders (we call these ‘α-bursts’). We infer from this pattern that the more lateral two layers of oblique hypaxial musculature, Mm. obliquus externus superficialis (OES) and obliquus externus profundus (OEP), are active on the side towards which the trunk is bending, while the more medial two layers, Mm. obliquus internus (OI) and transversus abdominis (TA), are active on the opposite side. This result is consistent with the hypothesis proposed for D. ensatus that the OES and OEP generate torsional moments to counteract ground reaction forces generated by forelimb support, while the OI and TA generate torsional moments to counteract ground reaction forces from hindlimb support. However, unlike the EMG pattern reported for D. ensatus, a second, lower-intensity burst of EMG activity (‘β-burst’) was sometimes recorded from the lateral hypaxial muscles in A. tigrinum. As seen in other muscle systems, these β-bursts of hypaxial muscle coactivation may function to provide fine motor control during locomotion. The presence of asynchronous, relatively high-intensity α-bursts indicates that the lateral hypaxial muscles generate torsional moments during terrestrial locomotion, but it is possible that the balance of forces from both α- and β-bursts may allow the lateral hypaxial muscles to contribute to lateral bending of the body as well.

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Interactions Between Posture and Locomotion: Motor Patterns in Humans Walking With Bent Posture Versus Erect Posture

Journal of Neurophysiology ◽

10.1152/jn.2000.83.1.288 ◽

2000 ◽

Vol 83 (1) ◽

pp. 288-300 ◽

Cited By ~ 117

Author(s):

R. Grasso ◽

M. Zago ◽

F. Lacquaniti

Keyword(s):

Gait Cycle ◽

Emg Activity ◽

Muscle Synergies ◽

Ground Reaction Forces ◽

Motor Patterns ◽

Erect Posture ◽

Body Segments ◽

Plane Orientation ◽

Temporal Coupling ◽

Reaction Forces

Human erect locomotion is unique among living primates. Evolution selected specific biomechanical features that make human locomotion mechanically efficient. These features are matched by the motor patterns generated in the CNS. What happens when humans walk with bent postures? Are normal motor patterns of erect locomotion maintained or completely reorganized? Five healthy volunteers walked straight and forward at different speeds in three different postures (regular, knee-flexed, and knee- and trunk-flexed) while their motion, ground reaction forces, and electromyographic (EMG) activity were recorded. The three postures imply large differences in the position of the center of body mass relative to the body segments. The elevation angles of the trunk, pelvis, and lower limb segments relative to the vertical in the sagittal plane, the ground reaction forces and the rectified EMGs were analyzed over the gait cycle. The waveforms of the elevation angles along the gait cycle remained essentially unchanged irrespective of the adopted postures. The first two harmonics of these kinematic waveforms explain >95% of their variance. The phase shift but not the amplitude ratio between the first harmonic of the elevation angle waveforms of adjacent pairs was affected systematically by changes in posture. Thigh, shank, and foot angles covaried close to a plane in all conditions, but the plane orientation was systematically different in bent versus erect locomotion. This was explained by the changes in the temporal coupling among the three segments. For walking speeds >1 m s−1, the plane orientation of bent locomotion indicates a much lower mechanical efficiency relative to erect locomotion. Ground reaction forces differed prominently in bent versus erect posture displaying characteristics intermediate between those typical of walking and those of running. Mean EMG activity was greater in bent postures for all recorded muscles independent of the functional role. The waveforms of the muscle activities and muscle synergies also were affected by the adopted posture. We conclude that maintaining bent postures does not interfere either with the generation of segmental kinematic waveforms or with the planar constraint of intersegmental covariation. These characteristics are maintained at the expense of adjustments in kinetic parameters, muscle synergies and the temporal coupling among the oscillating body segments. We argue that an integrated control of gait and posture is made possible because these two motor functions share some common principles of spatial organization.

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The scaling of ground reaction forces and duty factor in monitor lizards: implications for locomotion in sprawling tetrapods

Biology Letters ◽

10.1098/rsbl.2020.0612 ◽

2021 ◽

Vol 17 (2) ◽

pp. 20200612 ◽

Cited By ~ 1

Author(s):

Robert L. Cieri ◽

Taylor J. M. Dick ◽

Robert Irwin ◽

Daniel Rumsey ◽

Christofer J. Clemente

Keyword(s):

Body Size ◽

Duty Factor ◽

Ground Reaction Forces ◽

Cross Sectional ◽

Terrestrial Locomotion ◽

Reaction Forces ◽

Generation Capacity ◽

Monitor Lizards ◽

Force Time ◽

Muscle Cross Sectional Area

Geometric scaling predicts a major challenge for legged, terrestrial locomotion. Locomotor support requirements scale identically with body mass ( α M 1 ), while force-generation capacity should scale α M 2/3 as it depends on muscle cross-sectional area. Mammals compensate with more upright limb postures at larger sizes, but it remains unknown how sprawling tetrapods deal with this challenge. Varanid lizards are an ideal group to address this question because they cover an enormous body size range while maintaining a similar bent-limb posture and body proportions. This study reports the scaling of ground reaction forces and duty factor for varanid lizards ranging from 7 g to 37 kg. Impulses (force×time) ( α M 0.99−1.34 ) and peak forces ( α M 0.73−1.00 ) scaled higher than expected. Duty factor scaled α M 0.04 and was higher for the hindlimb than the forelimb. The proportion of vertical impulse to total impulse increased with body size, and impulses decreased while peak forces increased with speed.

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Motor Patterns for Human Gait: Backward Versus Forward Locomotion

Journal of Neurophysiology ◽

10.1152/jn.1998.80.4.1868 ◽

1998 ◽

Vol 80 (4) ◽

pp. 1868-1885 ◽

Cited By ~ 207

Author(s):

R. Grasso ◽

L. Bianchi ◽

F. Lacquaniti

Keyword(s):

Time Course ◽

Cross Correlation ◽

Gait Cycle ◽

Human Gait ◽

Emg Activity ◽

Ground Reaction Forces ◽

Motor Patterns ◽

Cross Correlation Analysis ◽

Reaction Forces ◽

Forward Locomotion

Grasso, R., L. Bianchi, and F. Lacquaniti. Motor patterns for human gait: backward versus forward locomotion. J. Neurophysiol. 80: 1868–1885, 1998. Seven healthy subjects walked forward (FW) and backward (BW) at different freely chosen speeds, while their motion, ground reaction forces, and electromyographic (EMG) activity from lower limb muscles were recorded. We considered the time course of the elevation angles of the thigh, shank, and foot segments in the sagittal plane, the anatomic angles of the hip, knee, and ankle joints, the vertical and longitudinal ground reaction forces, and the rectified EMGs. The elevation angles were the most reproducible variables across trials in each walking direction. After normalizing the time course of each variable over the gait cycle duration, the waveforms of all elevation angles in BW gait were essentially time reversed relative to the corresponding waveforms in FW gait. Moreover, the changes of the thigh, shank, and foot elevation covaried along a plane during the whole gait cycle in both FW and BW directions. Cross-correlation analysis revealed that the phase coupling among these elevation angles is maintained with a simple reversal of the delay on the reversal of walking direction. The extent of FW–BW correspondence also was good for the hip angle, but it was smaller for the knee and ankle angles and for the ground reaction forces. The EMG patterns were drastically different in the two movement directions as was the organization of the muscular synergies measured by cross-correlation analysis. Moreover, at any given speed, the mean EMG activity over the gait cycle was generally higher in BW than in FW gait, suggesting a greater level of energy expenditure in the former task. We argue that conservation of kinematic templates across gait reversal at the expense of a complete reorganization of muscle synergies does not arise from biomechanical constraints but may reflect a behavioral goal achieved by the central networks involved in the control of locomotion.

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Running ground reaction forces across footwear conditions are predicted from the motion of two body mass components

Journal of Applied Physiology ◽

10.1152/japplphysiol.00925.2018 ◽

2019 ◽

Vol 126 (5) ◽

pp. 1315-1325 ◽

Cited By ~ 3

Author(s):

Andrew B. Udofa ◽

Kenneth P. Clark ◽

Laurence J. Ryan ◽

Peter G. Weyand

Keyword(s):

Ground Reaction Force ◽

Lower Limb ◽

Reaction Force ◽

Ground Reaction Forces ◽

Vertical Ground Reaction Force ◽

Time Patterns ◽

Foot Strike ◽

Reaction Forces ◽

Vertical Ground ◽

Force Time

Although running shoes alter foot-ground reaction forces, particularly during impact, how they do so is incompletely understood. Here, we hypothesized that footwear effects on running ground reaction force-time patterns can be accurately predicted from the motion of two components of the body’s mass (mb): the contacting lower-limb (m1 = 0.08mb) and the remainder (m2 = 0.92mb). Simultaneous motion and vertical ground reaction force-time data were acquired at 1,000 Hz from eight uninstructed subjects running on a force-instrumented treadmill at 4.0 and 7.0 m/s under four footwear conditions: barefoot, minimal sole, thin sole, and thick sole. Vertical ground reaction force-time patterns were generated from the two-mass model using body mass and footfall-specific measures of contact time, aerial time, and lower-limb impact deceleration. Model force-time patterns generated using the empirical inputs acquired for each footfall matched the measured patterns closely across the four footwear conditions at both protocol speeds ( r2 = 0.96 ± 0.004; root mean squared error = 0.17 ± 0.01 body-weight units; n = 275 total footfalls). Foot landing angles (θF) were inversely related to footwear thickness; more positive or plantar-flexed landing angles coincided with longer-impact durations and force-time patterns lacking distinct rising-edge force peaks. Our results support three conclusions: 1) running ground reaction force-time patterns across footwear conditions can be accurately predicted using our two-mass, two-impulse model, 2) impact forces, regardless of foot strike mechanics, can be accurately quantified from lower-limb motion and a fixed anatomical mass (0.08mb), and 3) runners maintain similar loading rates (ΔFvertical/Δtime) across footwear conditions by altering foot strike angle to regulate the duration of impact. NEW & NOTEWORTHY Here, we validate a two-mass, two-impulse model of running vertical ground reaction forces across four footwear thickness conditions (barefoot, minimal, thin, thick). Our model allows the impact portion of the impulse to be extracted from measured total ground reaction force-time patterns using motion data from the ankle. The gait adjustments observed across footwear conditions revealed that runners maintained similar loading rates across footwear conditions by altering foot strike angles to regulate the duration of impact.

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Estimation of Ground Reaction Forces Based on Knee Joint Acceleration of Lower-Limb Exoskeletons

2020 International Automatic Control Conference (CACS) ◽

10.1109/cacs50047.2020.9289732 ◽

2020 ◽

Author(s):

Tesheng Hsiao ◽

Kinglam Yip ◽

Yun-Jen Chiu

Keyword(s):

Knee Joint ◽

Lower Limb ◽

Ground Reaction Forces ◽

Reaction Forces ◽

Joint Acceleration

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Ground Reaction Forces of Dressage Horses Performing the Piaffe

Animals ◽

10.3390/ani11020436 ◽

2021 ◽

Vol 11 (2) ◽

pp. 436 ◽

Cited By ~ 1

Author(s):

Hilary Mary Clayton ◽

Sarah Jane Hobbs

Keyword(s):

Coefficient Of Variation ◽

Three Dimensional ◽

Individual Variability ◽

The Other ◽

Ground Reaction Forces ◽

High Coefficient ◽

Reaction Forces

The piaffe is an artificial, diagonally coordinated movement performed in the highest levels of dressage competition. The ground reaction forces (GRFs) of horses performing the piaffe do not appear to have been reported. Therefore, the objective of this study was to describe three-dimensional GRFs in ridden dressage horses performing the piaffe. In-ground force plates were used to capture fore and hindlimb GRF data from seven well-trained dressage horses. Peak vertical GRF was significantly higher in forelimbs than in the hindlimbs (7.39 ± 0.99 N/kg vs. 6.41 ± 0.64 N/kg; p < 0.001) with vertical impulse showing a trend toward higher forelimb values. Peak longitudinal forces were small with no difference in the magnitude of braking or propulsive forces between fore and hindlimbs. Peak transverse forces were similar in magnitude to longitudinal forces and were mostly directed medially in the hindlimbs. Both the intra- and inter-individual variability of longitudinal and transverse GRFs were high (coefficient of variation 25–68%). Compared with the other diagonal gaits of dressage horses, the vertical GRF somewhat shifted toward the hindlimbs. The high step-to-step variability of the horizontal GRF components is thought to reflect the challenge of balancing on one diagonal pair of limbs with no forward momentum.

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Peripheral arterial disease affects ground reaction forces during walking

Journal of Vascular Surgery ◽

10.1016/j.jvs.2007.05.029 ◽

2007 ◽

Vol 46 (3) ◽

pp. 491-499 ◽

Cited By ~ 32

Author(s):

Melissa M. Scott-Pandorf ◽

Nicholas Stergiou ◽

Jason M. Johanning ◽

Leon Robinson ◽

Thomas G. Lynch ◽

...

Keyword(s):

Peripheral Arterial Disease ◽

Arterial Disease ◽

Ground Reaction Forces ◽

Reaction Forces ◽

Peripheral Arterial

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Acute response of biochemical bone turnover markers and the associated ground reaction forces to high-impact exercise in postmenopausal women

Biology of Sport ◽

10.5114/biolsport.2020.91497 ◽

2020 ◽

Vol 37 (1) ◽

pp. 41-48 ◽

Cited By ~ 3

Author(s):

Rizky Prawiradilaga ◽

Anders Madsen ◽

Niklas Jørgensen ◽

Eva Helge

Keyword(s):

Bone Turnover ◽

Postmenopausal Women ◽

Bone Turnover Markers ◽

High Impact ◽

Ground Reaction Forces ◽

Acute Response ◽

Reaction Forces ◽

Impact Exercise ◽

Turnover Markers

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Ground Reaction Forces and Kinematics of Ski Jump Landing Using Wearable Sensors

Sensors ◽

10.3390/s19092011 ◽

2019 ◽

Vol 19 (9) ◽

pp. 2011 ◽

Cited By ~ 5

Author(s):

Bessone ◽

Petrat ◽

Schwirtz

Keyword(s):

Wearable Sensors ◽

Reaction Force ◽

Ground Reaction Forces ◽

Inertial Motion ◽

Jump Landing ◽

The Past ◽

Landing Biomechanics ◽

Reaction Forces ◽

The Hill ◽

Kinematics And Kinetics

In the past, technological issues limited research focused on ski jump landing. Today, thanks to the development of wearable sensors, it is possible to analyze the biomechanics of athletes without interfering with their movements. The aims of this study were twofold. Firstly, the quantification of the kinetic magnitude during landing is performed using wireless force insoles while 22 athletes jumped during summer training on the hill. In the second part, the insoles were combined with inertial motion units (IMUs) to determine the possible correlation between kinematics and kinetics during landing. The maximal normal ground reaction force (GRFmax) ranged between 1.1 and 5.3 body weight per foot independently when landing using the telemark or parallel leg technique. The GRFmax and impulse were correlated with flying time (p < 0.001). The hip flexions/extensions and the knee and hip rotations of the telemark front leg correlated with GRFmax (r = 0.689, p = 0.040; r = −0.670, p = 0.048; r = 0.820, p = 0.007; respectively). The force insoles and their combination with IMUs resulted in promising setups to analyze landing biomechanics and to provide in-field feedback to the athletes, being quick to place and light, without limiting movement.

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