scholarly journals Adjustments with running speed reveal neuromuscular adaptations during landing associated with high mileage running training

2017 ◽  
Vol 122 (3) ◽  
pp. 653-665 ◽  
Author(s):  
Jasper Verheul ◽  
Adam C. Clansey ◽  
Mark J. Lake
Keyword(s):  
Lower Limb ◽  
Muscle Activation ◽  
Joint Stiffness ◽  
Thigh Muscle ◽  
Running Speed ◽  
Running Training ◽  
Knee Stiffness ◽  
Peak Knee ◽  
The Impact ◽  
Weight Acceptance

It remains to be determined whether running training influences the amplitude of lower limb muscle activations before and during the first half of stance and whether such changes are associated with joint stiffness regulation and usage of stored energy from tendons. Therefore, the aim of this study was to investigate neuromuscular and movement adaptations before and during landing in response to running training across a range of speeds. Two groups of high mileage (HM; >45 km/wk, n = 13) and low mileage (LM; <15 km/wk, n = 13) runners ran at four speeds (2.5–5.5 m/s) while lower limb mechanics and electromyography of the thigh muscles were collected. There were few differences in prelanding activation levels, but HM runners displayed lower activations of the rectus femoris, vastus medialis, and semitendinosus muscles postlanding, and these differences increased with running speed. HM runners also demonstrated higher initial knee stiffness during the impact phase compared with LM runners, which was associated with an earlier peak knee flexion velocity, and both were relatively unchanged by running speed. In contrast, LM runners had higher knee stiffness during the slightly later weight acceptance phase and the disparity was amplified with increases in speed. It was concluded that initial knee joint stiffness might predominantly be governed by tendon stiffness rather than muscular activations before landing. Estimated elastic work about the ankle was found to be higher in the HM runners, which might play a role in reducing weight acceptance phase muscle activation levels and improve muscle activation efficiency with running training. NEW & NOTEWORTHY Although neuromuscular factors play a key role during running, the influence of high mileage training on neuromuscular function has been poorly studied, especially in relation to running speed. This study is the first to demonstrate changes in neuromuscular conditioning with high mileage training, mainly characterized by lower thigh muscle activation after touch down, higher initial knee stiffness, and greater estimates of energy return, with adaptations being increasingly evident at faster running speeds.

scholarly journals How Well Do Commonly Used Co-contraction Indices Approximate Lower Limb Joint Stiffness Trends During Gait for Individuals Post-stroke?

2021 ◽  
Vol 8 ◽  
Author(s):  
Geng Li ◽  
Mohammad S. Shourijeh ◽  
Di Ao ◽  
Carolynn Patten ◽  
Benjamin J. Fregly
Keyword(s):  
Lower Limb ◽  
Muscle Activation ◽  
Sagittal Plane ◽  
Joint Stiffness ◽  
Energetic Cost ◽  
Electromechanical Delay ◽  
Antagonist Muscle ◽  
Post Stroke ◽  
Methodological Choices ◽  
Model Based

Muscle co-contraction generates joint stiffness to improve stability and accuracy during limb movement but at the expense of higher energetic cost. However, quantification of joint stiffness is difficult using either experimental or computational means. In contrast, quantification of muscle co-contraction using an EMG-based Co-Contraction Index (CCI) is easier and may offer an alternative for estimating joint stiffness. This study investigated the feasibility of using two common CCIs to approximate lower limb joint stiffness trends during gait. Calibrated EMG-driven lower extremity musculoskeletal models constructed for two individuals post-stroke were used to generate the quantities required for CCI calculations and model-based estimation of joint stiffness. CCIs were calculated for various combinations of antagonist muscle pairs based on two common CCI formulations: Rudolph et al. (2000) (CCI1) and Falconer and Winter (1985) (CCI2). CCI1 measures antagonist muscle activation relative to not only total activation of agonist plus antagonist muscles but also agonist muscle activation, while CCI2 measures antagonist muscle activation relative to only total muscle activation. We computed the correlation between these two CCIs and model-based estimates of sagittal plane joint stiffness for the hip, knee, and ankle of both legs. Although we observed moderate to strong correlations between some CCI formulations and corresponding joint stiffness, these associations were highly dependent on the methodological choices made for CCI computation. Specifically, we found that: (1) CCI1 was generally more correlated with joint stiffness than was CCI2, (2) CCI calculation using EMG signals with calibrated electromechanical delay generally yielded the best correlations with joint stiffness, and (3) choice of antagonist muscle pairs significantly influenced CCI correlation with joint stiffness. By providing guidance on how methodological choices influence CCI correlation with joint stiffness trends, this study may facilitate a simpler alternate approach for studying joint stiffness during human movement.

Leg Joint Stiffness Affects Dynamics of Backward Falling From Standing Height: A Simulation Work

2020 ◽  
Author(s):  
Mu Qiao ◽  
Feng Yang
Keyword(s):  
Older Adults ◽  
Lower Limb ◽  
Joint Stiffness ◽  
Biomechanical Properties ◽  
Knee Joints ◽  
Human Model ◽  
Loss Of Consciousness ◽  
Rotational Stiffness ◽  
Ankle Stiffness ◽  
The Impact

Abstract Falling backward can lead to injuries including hip fracture, back injury, and traumatic brain impact among older adults. A loss of consciousness is associated with falling backward and accounts for about 13% of all falls among older adults. Little is known about the dynamics of backward falls, such as the falling duration, the impact severity, and how the fall dynamics are affected by the biomechanical properties of the lower limb joints, particularly the rotational stiffness. The purpose of this study was to investigate the influence of the stiffness of individual leg joints on the dynamics of backward falls after losing consciousness in terms of the falling duration and impact velocities. Based on a 15-segment human model, we simulated the process of falling backwards by sweeping the parameter space of ankle, knee, and hip's stiffness varying from 0 to 8.73 Nm/deg (or 500 Nm/rad). The results revealed that the falling duration and impact speeds of the head and hip ranged from 0.27 to 0.63 s, 2.65 to 7.88 m/s, and 0.35 to 3.36 m/s, respectively, when the stiffness of the leg joints changed within their limits. Overall, the influence of the joint stiffness on the falling dynamics (falling duration and impact speed) is comparable between hip and knee joints. Whereas, ankle stiffness showed little influence on the backward falling dynamics. Our findings could provide references for designing protective devices to prevent impact-induced injuries after a backward fall.

scholarly journals Characterization of speed adaptation while walking on an omnidirectional treadmill

2020 ◽  
Vol 17 (1) ◽  
Author(s):  
Smit Soni ◽  
Anouk Lamontagne
Keyword(s):  
Lower Limb ◽  
Muscle Activation ◽  
Low Cost ◽  
Weight Bearing ◽  
Step Length ◽  
Overground Walking ◽  
Walking Pattern ◽  
Spatiotemporal Parameters ◽  
Walking Speeds ◽  
The Impact

Abstract Background Conventional treadmills are widely used for gait retraining in rehabilitation setting. Their usefulness for training more complex locomotor tasks, however, remains limited given that they do not allow changing the speed nor the direction of walking which are essential walking adaptations for efficient and safe community ambulation. These drawbacks can be addressed by using a self-pace omnidirectional treadmill, as those recently developed by the gaming industry, which allows speed changes and locomotor movements in any direction. The extent to which these treadmills yield a walking pattern that is similar to overground walking, however, is yet to be determined. Methods The objective of this study was to compare spatiotemporal parameters, body kinematics and lower limb muscle activation of healthy young individuals walking at different speeds (slow, comfortable, fast) on a low-cost non-motorized omnidirectional treadmill with and without virtual reality (VR) vs. overground. Results Results obtained from 12 young healthy individuals (18–29 years) showed that participants achieved slower speed on the treadmill compared to overground. On the treadmill, faster walking speeds were achieved by a mere increase in cadence, as opposed to a combined increase in cadence and step length when walking overground. At matched speed, enhanced stance phase knee flexion, reduced late stance ankle plantarflexion, as well as enhanced activation amplitudes of hip extensors in late stance and hip extensors in early swing were observed. The addition of VR to treadmill walking had little or no effect of walking outcomes. Collectively, results show that the omnidirectional treadmill yields a different walking pattern and lead to different adaptations to speed compared to overground walking. We suggest that these alterations are mainly driven by the reduced shear forces between the weight bearing foot and supporting surface and a perceived threat to balance on the omnidirectional treadmill. Conclusion Since such treadmills are likely to be used for prolonged periods of time by gamers or patients undergoing physical rehabilitation, further research should aim at determining the impact of repeated exposure on gait biomechanics and lower limb musculoskeletal integrity.

The Effect of Abdominal Muscle Activation Techniques on Trunk and Lower Limb Mechanics During the Single-Leg Squat Task in Females

2018 ◽  
Vol 27 (5) ◽  
pp. 438-444
Author(s):  
Lukas D. Linde ◽  
Jessica Archibald ◽  
Eve C. Lampert ◽  
John Z. Srbely
Keyword(s):  
Lower Limb ◽  
Injury Risk ◽  
Muscle Activation ◽  
Acl Injury ◽  
Abdominal Muscle ◽  
Abduction Angle ◽  
Peak Knee ◽  
Knee Abduction ◽  
Acl Injury Risk ◽  
Healthy Females

Context: Females suffer 4 to 6 times more noncontact anterior cruciate ligament (ACL) injuries than males due to neuromuscular control deficits of the hip musculature leading to increases in hip adduction angle, knee abduction angle, and knee abduction moment during dynamic tasks such as single-leg squats. Lateral trunk displacement has been further related to ACL injury risk in females, leading to the incorporation of core strength/stability exercises in ACL preventative training programs. However, the direct mechanism relating lateral trunk displacement and lower limb ACL risk factors is not well established. Objective: To assess the relationship between lateral trunk displacement and lower limb measures of ACL injury risk by altering trunk control through abdominal activation techniques during single-leg squats in healthy females. Design: Interventional study setting: movement and posture laboratory. Participants: A total of 13 healthy females (21.3 [0.88] y, 1.68 [0.07] m, and 58.27 [5.46] kg). Intervention: Trunk position and lower limb kinematics were recorded using an optoelectric motion capture system during single-leg squats under differing conditions of abdominal muscle activation (abdominal hollowing, abdominal bracing, and control), confirmed using surface electromyography. Main Outcome Measures: Lateral trunk displacement, peak hip adduction angle, peak knee abduction angle/moment, and average muscle activity from bilateral internal oblique, external oblique, and erector spinae muscles. Results: No differences were observed for peak lateral trunk displacement, peak hip adduction angle, or peak knee abduction angle/moment. Abdominal hollowing and bracing elicited greater muscle activation than the control condition, and bracing was greater than hollowing in 4 of 6 muscles recorded. Conclusion: The lack of reduction in trunk, hip, and knee measures of ACL injury risk during abdominal hollowing and bracing suggests that these techniques alone may provide minimal benefit in ACL injury prevention training.

Changes in Muscle Activity in Response to Different Impact Forces Affect Soft Tissue Compartment Mechanical Properties

2006 ◽  
Vol 129 (4) ◽  
pp. 594-602 ◽  
Author(s):  
Katherine A. Boyer ◽  
Benno M. Nigg
Keyword(s):  
Mechanical Properties ◽  
Soft Tissue ◽  
Muscle Activity ◽  
Muscle Activation ◽  
Joint Stiffness ◽  
Heel Strike ◽  
Emg Activity ◽  
Tissue Compartment ◽  
Tissue Compartments ◽  
The Impact

Electromyographic (EMG) activity is associated with several tasks prior to landing in walking and running including positioning the leg, developing joint stiffness and possibly control of soft tissue compartment vibrations. The concept of muscle tuning suggests one reason for changes in muscle activity pattern in response to small changes in impact conditions, if the frequency content of the impact is close to the natural frequency of the soft tissue compartments, is to minimize the magnitude of soft tissue compartment vibrations. The mechanical properties of the soft tissue compartments depend in part on muscle activations and thus it was hypothesized that changes in the muscle activation pattern associated with different impact conditions would result in a change in the acceleration transmissibility to the soft tissue compartments. A pendulum apparatus was used to systematically administer impacts to the heel of shod male participants. Wall reaction forces, EMG of selected leg muscles, soft tissue compartment and shoe heel cup accelerations were quantified for two different impact conditions. The transmissibility of the impact acceleration to the soft tissue compartments was determined for each subject/soft tissue compartment/shoe combination. For this controlled impact situation it was shown that changes in the damping properties of the soft tissue compartments were related to changes in the EMG intensity and/or mean frequency of related muscles in response to a change in the impact interface conditions. These results provide support for the muscle tuning idea—that one reason for the changes in muscle activity in response to small changes in the impact conditions may be to minimize vibrations of the soft tissue compartments that are initiated at heel-strike.

scholarly journals Human muscle activity and lower limb biomechanics of overground walking at varying levels of simulated reduced gravity and gait speeds

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0253467
Author(s):  
Mhairi K. MacLean ◽  
Daniel P. Ferris
Keyword(s):  
Lower Limb ◽  
Muscle Activity ◽  
Muscle Activation ◽  
Stance Phase ◽  
Knee Extension ◽  
Medial Gastrocnemius ◽  
Gravity Level ◽  
Reduced Gravity ◽  
Overground Walking ◽  
Peak Knee

Reducing the mechanical load on the human body through simulated reduced gravity can reveal important insight into locomotion biomechanics. The purpose of this study was to quantify the effects of simulated reduced gravity on muscle activation levels and lower limb biomechanics across a range of overground walking speeds. Our overall hypothesis was that muscle activation amplitudes would not decrease proportionally to gravity level. We recruited 12 participants (6 female, 6 male) to walk overground at 1.0, 0.76, 0.55, and 0.31 G for four speeds: 0.4, 0.8, 1.2, and 1.6 ms-1. We found that peak ground reaction forces, peak knee extension moment in early stance, peak hip flexion moment, and peak ankle extension moment all decreased substantially with reduced gravity. The peak knee extension moment at late stance/early swing did not change with gravity. The effect of gravity on muscle activity amplitude varied considerably with muscle and speed, often varying nonlinearly with gravity level. Quadriceps (rectus femoris, vastus lateralis, & vastus medialis) and medial gastrocnemius activity decreased in stance phase with reduced gravity. Soleus and lateral gastrocnemius activity had no statistical differences with gravity level. Tibialis anterior and biceps femoris increased with simulated reduced gravity in swing and stance phase, respectively. The uncoupled relationship between simulated gravity level and muscle activity have important implications for understanding biomechanical muscle functions during human walking and for the use of bodyweight support for gait rehabilitation after injury.

scholarly journals The Impact of a Rotating Balance Platform on Leg Neuromuscular Activity in Healthy Young Adults

2021 ◽  
pp. 22
Author(s):  
Keyword(s):  
Muscle Contraction ◽  
Lower Limb ◽  
Repeated Measures ◽  
Muscle Activation ◽  
Time To Peak ◽  
Contraction Duration ◽  
Tracking Tasks ◽  
Balance Rehabilitation ◽  
The Impact ◽  
Balance Board

Balance is a functional activity that must be implemented in every type of rehabilitation for the back and lower extremities’ injury and pathology. With issues in these regions, balance is lessened, requiring exercises that enhance the patient’s stability. Purpose: To determine the impact of activities on a rotating balance platform with tracking tasks for lower limb muscle activation. Method: Twenty-five participants performed seven tasks on a balance board with a fixed middle fulcrum. For each trial, activation of the gastrocnemius and tibialis anterior muscles was recorded using surface electromyography. Upon examination of the EMG data, the following variables were quantified: time to peak muscle activation, time to decay of muscle contraction, and time of muscle contraction duration. Results: A repeated measures ANOVA revealed that TA exhibited significant modifications (P<0.001) with less time to peak, duration, and decay, whereas GA only notably compensated (P<0.001) with shorter duration and decay. Conclusion: For subjects with balance alterations due to slower nerve conduction or muscle weakness in the lower limb, we suggest incorporating activities with rotational movements on the balance board, where muscle activation is challenged due to surface and tracking activities. When endurance is prescribed, front-to-back tasks contribute to prolonged muscle activation. Balance rehabilitation should consider muscle activation timing with tracking tasks for more precise and targeted muscle execution.

scholarly journals Effects of active muscle forces on driver’s lower-limb injuries due to emergency brake in various frontal impacts

2019 ◽  
Vol 234 (7) ◽  
pp. 2014-2024
Author(s):  
Fan Li ◽  
Wei Huang ◽  
Xingsheng Wang ◽  
Xiaojiang Lv ◽  
Fuhao Mo
Keyword(s):  
Muscle Contraction ◽  
Lower Limb ◽  
Injury Risk ◽  
Muscle Activation ◽  
Bending Moment ◽  
Lower Limbs ◽  
Lower Limb Injuries ◽  
Lower Limb Injury ◽  
Limb Injuries ◽  
The Impact

Accident data shows that driver’s kinematics response in real accidents can be significantly different from that in dummy or cadaver tests because of driver’s muscle contraction. In this study, a finite element human-body model consisting of an upper body of a dummy model and a lower limb–pelvis biomechanical model with three-dimensional active muscles was developed to investigate in depth the lower-limb injuries. Driver’s emergency reaction during frontal impact was simulated by modelling muscle active contraction based on a series of volunteer experimental tests. Besides, a realistic impact environment with the response of the restraint system and the invasion of the driver’s compartment was established in this study. The results show that muscle contraction can cause extra loads on lower limbs during the impact, which can increase the injury risk of lower limbs. As for the femur injury, muscle contraction caused an additional 1 kN axial load on the femur, and the femur resultant bending moment of active models was also higher by about 10–40 N m. Besides, the tibial index of the model with muscle activation was about 0.1 higher. In addition, the results indicate that the femur injury is strongly related to the combined action of both axial force and bending moment. The variation of the injury tolerance along the tibia shaft should be considered when evaluating the tibia injury. Overall, the current lower-limb injury criteria can be still the lack of robustness.

Identification of the most effective muscles in landing impact forces

2021 ◽  
pp. 175433712110324
Author(s):  
Marzieh Mojaddarasil ◽  
Mohammad Jafar Sadigh ◽  
Sayed Jalal Zahabi
Keyword(s):  
Lower Limb ◽  
Muscle Activation ◽  
Impact Force ◽  
Experimental Tests ◽  
The Body ◽  
Promising Tool ◽  
Impact Forces ◽  
Drop Landing ◽  
The Impact

The aim of this study was to evaluate the role of the main lower limb muscles in increasing or decreasing each lower limb joint impact force during drop landing. To do so, the body was modeled by a four-link musculoskeletal model consisting of eight main Hill-type muscles. Different drop landing scenarios were modeled by changing the activation levels of the considered muscles. In each landing simulation, the impact GRF and impact joint forces were obtained. In order to compare and rank the muscles with respect to their effect on each impact force, a computationally feasible zero-one (off-on) muscle activation analysis was proposed. The proposed approach revealed important features regarding the relation between different impact forces and muscle activations. Specifically, the results can be interpreted in terms of the role that each muscle potentially plays in causing or preventing certain injuries. Moreover, the results obtained from the analysis were further used to classify the muscles into four categories, depending on the effect they have on each impact force. The proposed theoretical analysis is seen to be a promising tool in predicting the role of muscles and their order of importance in the generation of lower limb impact forces in landing, without the need for experimental tests.

scholarly journals Lower Limb Muscle Activity Adjustment and Lactate Variation in Response to Increased Speed with Proportional Resistance in Young Adults

2021 ◽  
pp. 18
Author(s):  
◽  
Keyword(s):  
Young Adults ◽  
Lower Limb ◽  
Repeated Measures ◽  
Muscle Activation ◽  
Lower Limb Muscle ◽  
Limb Muscle ◽  
Small Load ◽  
Lactate Levels ◽  
Therapy Interventions ◽  
The Impact

Background: Various pathologies require physiotherapists to adjust therapy interventions, some of which are to reducing joint loads while strengthening the lower extremity musculature. Tools such as a sled can be used to accomplish a small load with high-repetition-resistance exercises. Purpose: This study examined the impact of pushing a sled with regulated resistance on lower limb muscle activation and fatigue while walking and running. Methods: The neuromuscular activity of the tibialis anterior (TA) and gastrocnemius (GA) muscles of thirty-six young adults were recorded using surface electromyography (EMG) and lactate data from a Nova Biomedical Lactate Plus meter. The sled used was the XPO Trainer, which maintains a steady resistance proportional to the user regardless of the forces applied to accelerate the sled. Baseline lactate was collected and followed by one of three protocols: run, run-push (RP), or walk-push (WP). Each included three trials over a 40 ft distance, during which EMG data were collected per trial, whereas lactate was collected following the completion of the appointed task. Results: Repeated measures ANOVAs were performed, showing a considerable increase (P<0.05) in lactate levels between the WP and RP groups. Pushing the sled at both WP and RP speeds demonstrated substantial (P<0.05) neuromuscular modifications, primarily in the TA, followed by the GA, in comparison to running. Conclusion: Pushing a constant resistance sled provoked distinct modifications in the lower limb musculature associated with speed. Running while pushing the sled elicits a higher blood lactate response associated with a longer maximal amplitude and a shorter time for muscle recruitment in the GA and TA muscles, all indicative of endurance-oriented exercise.

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