Hitting a support surface at unexpected height during walking induces loading transients (original) (raw)
Related papers
Sudden drop in ground support produces force-related unload response in human overground walking
Journal of neurophysiology, 2009
af Klint R, Nielsen JB, Sinkjaer T, Grey MJ. Sudden drop in ground support produces force-related unload response in human overground walking. . Humans maneuver easily over uneven terrain. To maintain smooth and efficient gait the motor system needs to adapt the locomotor output to the walking environment. In the present study we investigate the role of sensory feedback in adjusting the soleus muscle activity during overground walking in 19 healthy volunteers. Subjects walked unrestrained over a hydraulically actuated platform. On random trials the platform was accelerated downward at 0.8 g, unloading the plantar flexor muscles in midstance or late stance. The drop of the platform resulted in a significant depression of the soleus muscle activity of Ϫ17.9% (SD 2) and Ϫ21.4% (SD 2), with an onset latency of 49 ms (SD 1) and 45 ms (SD 1) in midstance and late stance, respectively. Input to the vestibular apparatus (i.e., the head acceleration) occurred at a latency 10.0 ms (SD 2.4) following the drop and ankle dorsiflexion velocity was decreased starting 22 ms (SD 15) after the drop. To investigate the role of length-and velocity-sensitive afferents on the depression in soleus muscle activity, the ankle rotation was arrested by using an ankle foot orthotic as the platform was dropped. Preventing the ankle movement did not significantly change the soleus depression in late stance [Ϫ18.2% (SD 15)], whereas the depression in midstance was removed [ϩ4.9% (SD 13)]. It is concluded that force feedback from ankle extensors increases the locomotor output through positive feedback in late stance. In midstance the effect of force feedback was not observed, suggesting that spindle afferents may have a more significant effect on the output during this phase of the step cycle.
Universal Journal of Public Health
The intra-subject variability is evaluated by a deterministic acceleration model in the frequency content between walking and running activities. The usefulness of this research is to explore the dependence of peak acceleration of foot on different pedestrian's velocity. Method: The mathematical model can be represented in time domain as a sum of Fourier harmonic components. The mathematical approach is applied to fit the accelerations of the foot, acquired during the impact shock of the human body on treadmill during walking and running activities at different speeds. Spectral analysis evaluates the frequency field of impact shock during walking and running activities. Results: The fitting of experimental data, by a mathematical approach, offers the analysis of the peak force of the foot on the ground, the dynamic acceleration factor (DAF) and the activity rate harmonics during walking and running activities. Conclusion: Marked differences in vertical accelerations are illustrated between walking and running activities. Recommendations could be deducted with regard to the dose of impacts that can be beneficial or detrimental to human health.
Low-frequency accelerations over-estimate impact-related shock during walking
Journal of Electromyography and Kinesiology, 2014
During gait, a failure to acknowledge the low-frequency component of a segmental acceleration signal will result in an overestimation of impact-related shock and may lead to inappropriately drawn conclusions. The present study was undertaken to investigate the significance of this low-frequency component in two distinctly different modalities of gait: barefoot (BF) and shod (SHOD) walking. Twenty seven participants performed five walking trials at self-selected speed in each condition. Peak positive accelerations (PPA) at the shank and spine were first derived from the time-domain signal. The raw acceleration signals were then resolved in the frequency-domain and the active (lowfrequency)and impact-related components of the power spectrum density (PSD) were quantified. PPA was significantly higher at the shank (P<0.0001) and spine (P=0.0007) in the BF condition. In contrast, no significant differences were apparent between conditions for shank (P=0.979) or spine(P=0.178) impact-related PSD when the low-frequency component was considered. This disparity between approaches was due to a significantly higher active PSD in both signals in the BF condition (P<0.0001; P=0.008,respectively), due to kinematic differences between conditions (P<0.05). These results indicate that the amplitude of the low-frequency component of an acceleration signal during gait is dependent on knee and ankle joint coordination behaviour, and highlight that impact-related shock is more accurately quantified in the frequency-domain following subtraction of this component.
The Journal of Physiology, 2003
In the lower leg, landing after a jump induces reflexes, the role of which is not well understood. This is even more so for reflexes following landing on inverting surfaces. The latter condition is of special interest since ankle inversion traumata are one of the most common injuries during sport. Most studies have investigated ankle inversions during a static standing condition. However, ankle injuries occur during more dynamic activities such as jumping. Therefore, the present study aimed at reproducing these situations but in a completely safe setting. EMG responses were recorded after landing on an inverting surface, which caused a mild ankle inversion of 25 deg of rotation (in a range sufficient to elicit reflexes but safe enough to exclude sprains). The results are compared with data from landing on a non‐inverting surface to understand the effect of the inversion. In general, landing on the platform resulted in short and long latency responses (SLR and LLR) in triceps surae (...
Ground Reaction Force Comparison Between Barefoot and Shod Single Leg Landing at Varied Heights
Australian International Academic Centre, 2021
Background: Landing is a common movement that occurs in many sports. Barefoot research has gained popularity in examining how shoes alter natural movements. However, it is unknown how a single leg landing under barefoot conditions, as well as landing height, affects ground reaction forces (GRF). Objective: The purpose of this research was to examine the differences in GRF during a single leg landing under barefoot and shod conditions from various heights. Methods: Sixteen female Division II collegiate athletes, 8 basketball (age: 19.88 ± 0.64 yrs; height: 1.77 ± 0.09 m; mass: 75.76 ± 12.97 kg) and 8 volleyball (age: 20.00 ± 1.07 yrs; height: 1.74 ± 0.08 m; mass: 72.41 ± 5.41 kg), performed single leg landings from 12, 18, 24, and 30 inches barefoot and shod. An AMTI AccuGait force plate was used to record GRF. A 2 (condition) x 4 (box height) x 2 (sport) repeated measures ANOVA was performed to determine any GRF differences. Results: There were no significant three way or two-way interactions (p > 0.05). There was also no main effect for sport (p > 0.05). There were main effects for footwear and box height (p = 0.000) where shod (2295.121 ± 66.025 N) had greater impact than barefoot (2090.233 ± 62.684 N). Conclusions: Single leg barefoot landings resulted in less vertical GRF than shod landings. This could be due to increased flexion at the joints which aids in force absorption.
Effects of surface instability on neuromuscular performance during drop jumps and landings
European Journal of Applied Physiology, 2013
Purpose The purpose of this study was to investigate the effects of surface instability on measures of performance and activity of leg and trunk muscles during drop jumps and landings. Methods Drop jumps and landings were assessed on a force plate under stable and unstable (balance pad on top of the force plate) conditions. Performance measures (contact time, jump height, peak ground reaction force) and electromyographic (EMG) activity of leg and trunk muscles were tested in 27 subjects (age 23 ± 3 years) during different time intervals (preactivation phase, braking phase, push-off phase). Results The performance of drop jumps under unstable compared to stable conditions produced a decrease in jump height (9 %, p \ 0.001, f = 0.92) and an increase in peak ground reaction force (5 %, p = 0.022, f = 0.72), and time for braking phase (12 %, p \ 0.001, f = 1.25). When performing drop jumps on unstable compared to stable surfaces, muscle activity was reduced in the lower extremities during the preactivation, braking and push-off phases (11-25 %, p \ 0.05, 0.48 B f B 1.23). Additionally, when landing on unstable compared to stable conditions, reduced lower limb muscle activities were observed during the preactivation phase (7-60 %, p \ 0.05, 0.50 B f B 3.62). Trunk muscle activity did not significantly differ between the test conditions for both jumping and landing tasks. Conclusion The present findings indicate that modified feedforward mechanisms in terms of lower leg muscle activities during the preactivation phase and/or possible alterations in leg muscle activity shortly after ground contact (i.e., braking phase) are responsible for performance decrements during jumping on unstable surfaces.
Ground Reaction Forces Attenuation in Supinated and Pronated Foot During Single Leg Drop Landing
The aim of this study was to compare the peak Vertical Ground Reaction Forces (VGRF) and Rate of Loading (ROL) between supinated, pronated, and normal feet during single leg droplanding. Thirty healthy male students from physical education & sport sciences department participated in this study and assigned to one of three groups by navicular drop test (10 per groups) [pronated (≥10mm), neutral (5-9mm), or supinated ]. Participants performed single leg drop-landing on the force plate from the box with height of 0.30 m. Peak VGRF and ROL were calculated using GRF data. There were significant differences in ROL between three groups (F 2, 22 =15.553, Wilks' Lambda = 0.370, P≤0.05) but differences in Peak VGRF were not significant between them (F 2, 22 = 2.632, P >0.05). These results suggest that supinated foot is associated with specific lower extremity kinetics. Differences in these parameters may subsequently lead to differences in injury patterns in supinated and pronated foot in athletes.
Impact shock frequency components and attenuation in rearfoot and forefoot running
Journal of Sport and Health Science, 2014
Background: The forefoot running footfall pattern has been suggested to reduce the risk of developing running related overuse injuries due to a reduction of impact related variables compared with the rearfoot running footfall pattern. However, only time-domain impact variables have been compared between footfall patterns. The frequency content of the impact shock and the degree to which it is attenuated may be of greater importance for injury risk and prevention than time-domain variables. Therefore, the purpose of this study was to determine the differences in head and tibial acceleration signal power and shock attenuation between rearfoot and forefoot running. Methods: Nineteen habitual rearfoot runners and 19 habitual forefoot runners ran on a treadmill at 3.5 m/s using their preferred footfall patterns while tibial and head acceleration data were collected. The magnitude of the first and second head acceleration peaks, and peak positive tibial acceleration were calculated. The power spectral density of each signal was calculated to transform the head and tibial accelerations in the frequency domain. Shock attenuation was calculated by a transfer function of the head signal relative to the tibia. Results: Peak positive tibial acceleration and signal power in the lower and higher ranges were significantly greater during rearfoot than forefoot running (p < 0.05). The first and second head acceleration peaks and head signal power were not statistically different between patterns (p > 0.05). Rearfoot running resulted in significantly greater shock attenuation for the lower and higher frequency ranges as a result of greater tibial acceleration (p < 0.05). Conclusion: The difference in impact shock frequency content between footfall patterns suggests that the primary mechanisms for attenuation may differ. The relationship between shock attenuation mechanisms and injury is not clear but given the differences in impact frequency content, neither footfall pattern may be more beneficial for injury, rather the type of injury sustained may vary with footfall pattern preference.
Journal of Bodywork and Movement Therapies, 2018
Background: Pronated foot is one of the most important factors that may lead to musculoskeletal injuries of the lower extremities. It is known that in a pronated foot, excessive mechanical loads are applied to the lower limb structures, which result in the altered foot biomechanics, including vertical ground reaction forces (VGRFs) and rate of loading (ROL). Therefore, the aim of this study was to determine the changes in foot kinetic parameters in the pronated compared to the normal foot structures. Methods: In this cross-sectional study, 15 individuals (mean age of 23.27 ± 3.28 years) with asymptomatic pronated feet and 15 normal subjects (mean age of 23.40 ± 3.11 years) were recruited from both genders by using a simple non-random sampling method. VGRF, ROL, and the resultant vector of time to stabilization (RVTTS) were evaluated during the forward jump landing task by using a force plate. Results: The findings showed that the following parameters were significantly higher in the group of pronated feet than in the normal subjects: VGRF (3.30 ± 0.17 vs. 2.81 ± 0.15, p ¼ .042), ROL (0.10 ± 0.01 vs. 0.07 ± 0.006, p ¼ .020), and RVTTS (2592.80 ± 141.24 vs. 2114.00 ± 154.77, p ¼ .030). Conclusion: All the measured foot kinetic parameters were higher in the pronated foot subjects than in the normal participants. An impaired movement control and greater forces imposed on the foot region of the pronated foot, compared to the normal foot individuals, were discovered indicating the former group's possible increase of susceptibility to various musculoskeletal injuries.
Archives of Physical Medicine and Rehabilitation, 1996
To test the hypotheses that the incidence of protective stepping in response to sudden translations of the support would (1) increase as a function of both the magnitude of surface displacement and velocity of platform movement, and (2) decrease in association with an increase in external loading applied to the body. A log-linear approach was used to analyze the incidence of stepping by testing several models incorporating different platform stimulus parameters (direction, displacement, velocity) and external loading (0% and 20% body weight). Institutional-based research laboratory. Eight healthy younger adult (21 to 28 years) volunteers. The incidence and number of protective steps served as the primary planned outcome variables. Steps occurred more frequently for anterior (83 steps) versus posterior (45 steps) translations. Step occurrence was generally proportional to platform velocity, and increased with displacements up to 15cm, but then plateaued. External loading was associated with a reduction in the number of steps for lower magnitudes of platform motion but had little effect at higher magnitudes. The tendency to step in response to externally applied disturbances to stance appears to be a complex function of direction, velocity, displacement, and inertial load.