جستجوی مقالات مرتبط با کلیدواژه « نرخ بارگذاری » در نشریات گروه « پزشکی »

Background & Aim:

Low back pain refers to a pain felt in the lumbar and sacrum regions of the spine. The aim of this study was to investigate the effect of movement pattern exercises on plantar pressure variables in people with chronic low back pain during walking.

Materials & Methods:

The present study was a quasi-experimental study with a pre-test and post-test design along with a control group. The study subjects, who were selected from the clients of the health and wellness center of Mohaghegh Ardabili University, Ardabil, Iran, were randomly divided into 10 people with chronic back pain (experimental group) and 10 people with back pain (control group). The subjects of the experimental group performed movement pattern exercises for 6 weeks, but the control group did not perform any exercises during this period of 6 weeks. Plantar pressure values were recorded during pre-test and post-test by foot scan device (sampling rate: 300 Hz). Two-way analysis of variance was used for statistical analysis of data. All analysis was done at significant level of 0.05 with SPSS 22 software.

Results showed that the peak of the vertical component at the heel contact (p = 0.009) and the vertical loading rate (p = 0.013) in the experimental group during post-test was lower compared to the pre-test. Pairwise comparison showed that the peak force in the second metatarsal bone in the experimental group was lower in the post-test compared to the pre-test (p=0.018).

The link between “Delayed Onset of Muscle Soreness” (DOMS) and force components and loading rate during landing is not well understood. Therefore, the aim of this study was to determine the effect of “Delayed Onset of Muscle Soreness” on ground reaction forces and loading rate during landing in Healthy non-athlete subjects.

This research was a semi-experimental (DOMS-induced exercises by Harvard step test) with a pretest and post-test design. The present study’s statistical population of the consisted of non-athlete students were volunteered to participate in this study. A total of 15 healthy male non-athlete students were selected following a simple random sampling by Lottery procedure. In this study, the demographic questionnaire and “General Health Questionnaire” were used to assess the general health conditions and enter the subjects into the study. The weight and height of the subjects were measured using the tools and devices of the Sika 206 dynamometer and gauge screen, respectively. The validity and reliability of these instruments have been confirmed in previous studies. To control the landing height, Vicon motion analysis system including 4 high-speed infrared cameras was used. The Ground Reaction Force(GRFs) during cross-landing was measured using a force plate and then the kinetic indices including the peak and depth of the Ground Reaction Force and the time of reaching the peak and bottom and the loading rate were extracted by Vicon Nexus software. Data were analyzed using SPSS. 23.

“Delayed Onset of Muscle Soreness” has no effect on the Ground Reaction Force when heel contact (P <0.05). “Delayed Onset of Muscle Soreness” reduces the maximum vertical reaction force (FZ1) in toe contact with the ground (P = 0.038) and the minimum vertical reaction force (FZ2) in toe contact with the ground (P = 0.006) after It was 48 hours. People with “Delayed Onset of Muscle Soreness” have a faster time to reach the 1.2 FZ characteristic (P = 0.001 and P = 0.010). 

“Delayed Onset of Muscle Soreness” reduces the vertical force of the reaction when the toe comes in contact with the ground when landing, as well as the faster arrival time of the reaction forces when in contact with the toe. Therefore, it is suggested that therapists, physiotherapists and other groups be trained about the treatment and prevention strategies of these risk factors in activity and rehabilitation with feedback from the changes of these biomechanical parameters.

Since changes in body alignment cause an impairment of motor skills, the purpose of this study was to investigate the effect of genu varum on the kinetics of running in anticipated and unanticipated conditions.30 elite male soccer players (two groups of genu varum and normal) were recruited in this semi-experimental study. The data of ground reaction force was collected by two force plates during running.The results showed that vertical ground reaction force and loading rate were significantly greater in genu varum group compared with normal group in both anticipated and unanticipated conditions (p≤0.05). Also, time to peak of vertical ground reaction force in unanticipated condition was longer than anticipated condition (p≤0.05). There was no significant different between groups and conditions in anterior-posterior and medial-lateral GRF, time to peak of anterior-posterior GRF, vertical and propulsive impulse and contact time (p>0.05).According to the results, it seems that kinetics of running of soccer players can be affected by genu varum and anticipation.

More than 60 % of runners suffer from overuse injuries each year. Exercise and Running surfaces can prevent injuries and/or improve performance. The present study aims to investigate the effect of three types of running surfaces (Polyvinyl Chloride (PVC), artificial turf, and sand) on the Ground Reaction Force (GRF) components in the stance phase of running.

Impact force, loading rate, and free moment of 15 men were recorded while running barefoot on three PVC, artificial turf, and sand surfaces at a speed of 3±0.2 m/s (Average of 5 correct attempts). Comparison between different conditions was performed using repeated measures ANOVA and Bonferroni’s Post-Hoc Test.

The sand surface significantly reduced the impact force compared to the PVC and artificial turf. Both sand and artificial turf caused a significant reduction in the force loading rate compared to the PVC surface. The second peak of vertical GRF (propulsive force) increased at sand (P=0.001) and artificial turf (P=0.005) surfaces compared to the PVC surface. Moreover, the sand surface reduced adductor torque compared to the PVC (p < 0.001) and artificial turf (P=0.003) surfaces, while the artificial turf reduced abductor torque compared to the PVC surface (P=0.011).

Sand is a safer surface for preventing running injuries due to eliminating impact force, reducing loading rate, and having high shock absorption. Training on a sand surface may improve performance on harder surfaces.

Investigating the risk factors during single crossover landing in people with flat foot complication is unknown. Therefore, the aim of the present study is to compare the ground reaction forces and the amount of load introduced during crossover landing in people with flat foot and healthy individuals.
  

The study method is descriptive-comparative. Twelve male subjects with low longitudinal arch (age = 24.67 ± 4.45; height= 176.12 ± 5.64; Weight= 765.62 ±11.2) and twenty-two matched healthy control subjects (age=23.47 ±5.63; height= 178.66 ± 3.87; Weight= 714.31 ±13.61) participated in this study. Based on the Arch Height Index (AHI), was divided into two healthy and healthy groups with flat feet. The ground reaction force was measured using a force plate (1000 Hz) during crossover-landing. Then, the kinetic indicators, including the peak of the ground reaction force and the time to reach them and the loading rate, were extracted by Vicon Nexus 1.8.5, Polygon 4.1.2 software. Data were analyzed with SPSS. 23.

People with flat feet have fewer vertical ground reaction force (FZ1,2,3) when crossover landing compared to healthy individuals (P <0.05). The time to reach the minimum vertical force of the action photo (valley) at the moment of contact of the toe with the ground (TFZ2) is faster in people with flat foot complication (P = 0.022).

People with flat feet had less vertical force, less vertical reaction time, and faster reaction time than healthy people, and these factors were considered as a risk factor for increasing fracture of 1-3 metatarsal and ankle sprain. Therefore, it is recommended to teach strategies to prevent these risk factors in activity and rehabilitation.

Functional ankle sprain is a common injury in different sports. Study of Ground Reaction Forces in different physical activity is associated with the risk of lower extremity injury and has a clinical importance. The objectives of this study were to analyze the GRF, and loading rate during running in ankle sprain compared with healthy subjects.

In this study, 10 healthy men and 10 soccer player with ankle sprain participated. Using two adjacent Kistler force plates (1000Hz) GRF during stance phase of running was measured. Then, maximum GRF, impulse, and loading rate, were obtained. MANOVA was used to analyze the data (α=0.05).

The results showed that there is a significant difference between two groups in ground reaction force of Fz1and Fz2 (p=0.01, p=0.01). On the other hand, there was a significant difference between the two groups in time to peak of components in Fz3 and Fx2 directions (p=0.02, p=0.004). Also, there was a significant difference between the two groups in time to peak of components in Fy1 and Fy2 directions (p=0.04, p=0.04).  The experimental group showed a higher loading rate than the control group (p=0.01).

The results showed that the values of initial reaction force and loading rate in the experimental group were higher than the control group. It seem less foot adaptability increases the loading rate in the experimental group. Since these forces are exacerbating the types of structural damage, therefore, therapists should pay particular attention to reducing these forces by modifying the motor strategy, strengthening the muscles and, even in some cases, prescribing a medical insole.

The Frequency Domain analysis of Ground reaction forces is one of the mechanical parameters that play a significant role in the vulnerability of people while walking and running. The purpose of the present study was to compare the frequency domain analysis of ground reaction forces in deaf and healthy control people during running.

A quasi-experimental study was carried out on 30 males who were equally divided into a healthy group and a group with hearing loss problems (Deaf group). Peak plantar pressure variables in deaf individuals and healthy controls were recorded using a foot scan system (sample rate: 300 Hz).

The results showed that the frequency content with the number of essential harmonies in the Toe foot (p= 0.012) and foot finger 2 to 5 (p=0/035) in deaf were smaller than those of the healthy controls. Also, the frequency content with power 99.5% in the fourth metatarsal (P=0.038) and fifth metatarsal (P=0.019) in deaf were greater than those of the healthy controls. Moreover, stance time during running in deaf group was more than that of the healthy control group (p=0.032).

Stance time during running in deaf group was more than that of the healthy control group, which has the potential for injury in these people.

Genu varum is one of the lower limb malalignments that is associated with changes in the lower limb biomechanics during walking and running. The selected corrective program has the least complications for children. Therefore the purpose of the present study was to investigate the effects of a period of corrective exercise training program on the running ground reaction forces in children with genu varum. In this clinical trial, 17 children with genu varum from Hamadan city were volunteered to participate in 2016. Tests were done in the form of pre and post-tests. Corrective exercises were performed on subjects over a 16-week period. Paired sample t-test was used for statistical analysis of data. In the dominant limb, the peak vertical ground reaction force during push-off phase demonstrated a significant increase during the post-test compared to the pre-test (p=0.012). In the non-dominant limb, the findings showed that impulse decreased significantly in the anterior-posterior direction during the post-test compared to the pre-test (p=0.039). Also, at the non-dominant limb in the free moment, the negative peak showed a significant increase after the training period (p= 0.015). Other components such as vertical loading rate, impulse and free moment at the positive and negative peak showed no significant difference between the pre and post-test (p> 0.05). The findings indicated that the corrective exercises used in the present study improved peak ground reaction forces, impulse and free moment values, but did not have any significant effect on the loading rate.

The amount and distribution of ground reaction force during landing are linked with risk factor of the injuries related to lower limb joints. Insole may alter the amount of these forces. The objectives of this study were to analyze the effects of insole on GRF and their time-to peak of each reaction force, impulse, and loading rate during landing in normal individuals.
Thirteen healthy male subjects with mean age, mass and height of (21.9±1.6 years), (67.1±12.6 kg), and (175.3±4.9 cm), respectively, participated in this study. Using a Kistler force plates (1000Hz), GRF during landing with and without shoe insole were measured. Then, maximum GRF and their related time-to-peak, impulse and loading rate were obtained. Repeated measure ANOVA was used to analyze the data (α=0.05).
Wearing insole decreased the peak vertical GRF on heel contact of body weight (P=0.006), the loading rate (P=0.01), and the vertical impulse (P=0.0032).
Reduction of the vertical GRF and loading rate by means of insole may reduce the risk of lower extremity injuries due to impulse during landing.

Aims and The purpose of this study was to compare the parameters of ground reaction force during landing in patients with chronic low back pain. Material and 21 healthy men and 21 men with chronic low back pain participated in this study. Using a Kistler force plate )1000Hz) GRF during landing was measured. Then, maximum GRF and their related time-to-peak, impulse and loading rate were obtained. Independent t student was used to analyze the data (α=0.05). Findings: People with chronic low back pain have lower internal-external GRF and have a lower vertical GRF to touching the ground )FZ2) when landing compared to healthy people. Patients with chronic low back pain have a lower loading rate(Y)(P=.049). People with low back pain have a higher vertical ground reaction force than healthy people, and these factors are considered as a risk factor for increasing compressive forces to the spine.

In deformed spine of adolescent patients with idiopathic scoliosis, the interaction between the deformity and kinetic aspects during gait has not been well understood. The aim of this study was to analyze the ground reaction force (GRF) during gait in adolescent idiopathic scoliosis (AIS) and healthy control group.
Nineteen adolescent female patients with right thoracic idiopathic scoliosis of between 11-16 years of ages as well as 18 healthy females with similar age-matched, height and mass were studied.
Using two Kistler force plates (1000 Hz) and a Vicon system with 4 T series cameras (100 Hz), the GRF and kinematic aspects of subjects’ gait were simultaneously recorded. GRF forces in x (Fx), y (Fy), and z axes (Fz), together with impulse, loading rate, and the asymmetry index (AI) for all variables were evaluated. AI index was calculated with [(Right X – Left X)/ ((Right X Left X)*0.5)]*100. MANOVA was used to assess the between group differences, Also, repeated measure analysis of variance was used for within group comparisons. Significance level was set at at p In the right foot, all parameters of GRF were similar in AIS and control groups (p>0.05). In the left foot also, Fy and Fx components of GRF were similar between groups (P>0.05). However, the Fz1 parameter of the left foot in scoliosis group was significantly smaller than that of in control group (p=0.03). In the right and left feet, the impulses, loading rate and time related GRF variables were not different between two groups (p>0.05). The AI for all variables were similar in both groups (p AIS patients demonstrated reduced vertical GRF in left heel contact phase with respect to the control group. Unilateral alteration of the muscle function in the lower limb might be a possible explanation to this abnormality. Further more complex studies are needed to evaluate the origin and consequence of this observation.

Evaluation of ground reaction forces (GRF) and other kinetic factors have clinical importance. There is interaction between shoe type and insole with these factors. The objectives of this study were to assess the acuteeffects of arch support insole on GRF and their time-to peak of each reaction force, impulse, loading rate, and free moment during stance phase of gait in normal individuals.
Sixteen healthy male subjects with mean age, mass and height of 29.4±4.8 years, 77.9±12.6 kg, and 176.5±5.8 cm, respectively, participated on this study. Using two adjacent Kistler force plates (1000Hz) GRF during stance phase of walking with and without shoe insole were measured. Then, maximum GRF and their related time-to-peak, impulse, loading rate, and free moment were obtained. Repeated measure ANOVA was used to analyze the data (α=0.05).
Wearing insole caused reduction of the peak vertical GRF on heel contact by 6.9% of body weight (BW) (p=0.001) and the loading rate (8.4%, p=0.02), while it increased the propulsive force (7% N/BW, p=0.001), anterior-posterior impulse by 1.2% BW.s (p=0.003) and normal impulse by 2% of BW.s (p=0.032).
Reduction of the vertical GRF and loading rate by means of insole may reduce the risk of lower extremity injuries due to impulse during walking. Arch supportinsole application can prevent sport injuries by reducing the reaction forces.

There are relations between rate of loading, osteoarthritis and genu varum result in osteoarthritis. This study was done to compare the peak vertical ground reaction forces and the rate of loading during single leg drop landing between men with genu varum deformity and normal knee from three heights. This quasi-experimental studywas carried out on 20 male students with genu varum deformity and 20 male students with normal knee. Genu varum deformity was measured and recorded by collis and goniometer. Subjects performed single-leg landing dropping from three heights (20, 40, 60 Centimeter) on a force platform. The peak vertical ground reaction force in calcaneus contact and the rate of loading between groups significantly were different (P<0.05). No significant difference was found in the peak vertical ground reaction during toe contact. Frontal knee angle affect on loading rate. Maybe one of the reasons for higher injury risk and knee arthritis in genu varum population might be due to higher ground reaction forces and the rate of high loading.

There is relation between the rate of loading and arthrosis. Genu varum results in osteoarthritis. Knowing the changes of the affected biomechanical variables during landing result in fundamental understanding to prevent arthrosis in people with genu varum deformity. Hence, the purpose of this study was to compare the plantar flexor muscles activity with the rate of loading during single leg drop landing between men with genu varum deformity and normal knee from three heights.

40 healthy male students participated in this semi-experimental research. Subjects were 20 people with genu varum deformity and the rest half with normal knee. Genu varum deformity was measured by a caliper and goniometer. Subjects performed single-leg landing dropping from three different heights)20, 40 and 60 cm) onto a force platform. Landing movement was divided into two phases: 100 ms precontact and postcontact of foot onto the ground. Data analysis was performed using Mixed ANOVA.

It has been observed no significant difference during pre-landing between the activities of the medial gastrocnemius and soleus muscles (p> 0.05). Although, there was a significant difference between two groups in the rate of loading with the activity of the medial gastrocnemius muscle during post-landing (p<0.05) and eventually there was no significant difference between soleus muscle activity in post-landing (p>0.05).

The higher rate of injury and arthrosis risk in people with genu varum in respect of normal ones might be due to the rate of high loading inserted to the extremities during landing. To diminish these risks, corrective exercises and corrected biomechanical activity are recommended.

Stress fracture occur following bone exposure to cyclic sub-threshold loadings before repairing previous micro-fractures. The aims of this study were: 1) to assess and compare the ground reaction force and loading rate responses of the fixed-cadence marching at the fourth step and single-leg landing; and 2) the effect of over striding in the fourth step of fixed-cadence marching on the ground reaction forces and loading rates. a total of ten male students of Police (NAJA) University were enrolled. Five experiments including two single leg landing، two fixed-cadences marching، and regular running experiments were applied. The experiments data were collected with 200 Hertz using a force plate device. The results showed a high correlation between the fixed-cadence marching at the fourth step and single leg landing with both studied step lengths for the peak vertical and posterior components of ground reaction force and loading rate (r = 0. 863، r = 0. 781، r = 0. 847، and r = 0. 798 for step length of 25 centimeter، and r=0. 865، r=0. 74، r=0. 831، and r=0. 716 for step length of 50 centimeter; p <0. 05). By increasing the step length، all variables increased significantly (p <0. 05). The increase in the amount and rate of ground reaction forces can increase the risk of stress fracture on the lower extremities of soldiers and officers. As a mechanism to prevent over striding and consequently stress fractures in the fixed-cadence marching، it is suggested that recruits with the same height can be arranged to a group during marching، so that their step length maintain around their preferred one.

High rate of loading is related to osteoarthritis and genu varum result in osteoarthritis. Knowing the rate of affected biomechanical variables during landing which is the cause of this deformity result in fundamental understanding to prevent osteoarthritis in people with genu varum deformity. Hence the purpose of this study is to compare the peak vertical ground reaction forces and the rate of loading during single leg drop landing between men with genu varum deformity and normal knee.

Fourthy male students in physical education and sport science participated in this research; subjects were 21 people with genu varum deformity and 19 with normal knee. Genu varum deformity was measured and recorded by a caliper. Subjects performed single-leg landing dropping from a 0. 3 m height onto a force platform. Statistical analysis of data was performed between two groups via MANOVA test.

No significant difference was found in the peak vertical ground reaction during metatarsal contact (P = 0. 486). However the peak vertical ground reaction force in calcaneus contact (P = 0. 002) and the rate of loading (P = 0. 048) between groups were significantly different.

Subtle variations in frontal plane of tibiofemoral joint angulation and standing foot angle، influence knee and ankle joint forces، moments، and muscle activation characteristics. The higher rate of injury and osteoarthritis risk in people with genu varum in respect to normal ones might be due to higher ground reaction forces and the rate of high loading inserted to the extremity during landing. To diminish the risk of injury and osteoarthritis، corrective exercises and corrected biomechanical activity are recommended.