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Objective A practical and highly accurate algorithm for dynamic monitoring of plantar pressure was proposed, the magnitude of vertical ground reaction force (vGRF) during walking was measured by a capacitive insole sensor, and reliability of the prediction accuracy was verified. Methods Four healthy male subjects were require to wear capacitive insole sensors, and their fast walking and slow walking data were collected by Kistler three-dimensional (3D) force platform. The data collected by the capacitive insole sensors were pixelated, and then the processed data were fed into a residual neural network, ResNet18, to obtain high-precision vGRF. Results Compared with analysis of the data collected from Kister force platform, the normalized root mean square error (NRMSE) for fast walking and slow walking were 8.40% and 6.54%, respectively, and the Pearman correlation coefficient was larger than 0.96. Conclusions This study provides a novel algorithm for dynamic measurement of GRF in mobile scenarios, which can be used for estimation of complete GRF outside the laboratory without being constrained by the number and location of force plates. Potential application areas include gait analysis and efficient capture of pathological gaits.
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ObjectiveAiming at the need of control strategy switching of intelligent above-knee prosthetic, taking the plantar pressure of human walking as the research object, and based on fuzzy logic algorithm, a gait phase division method based on plantar pressure of prosthetic is proposed. MethodsThree flexible force sensors installed on the soles of the false feet were used to collect the plantar pressure information of the test object under three different walking modes (walking on the flat road, walking downhill and walking down the stairs). After data fusion processing, it was sent to the fuzzy logic controller, and the recognition results were output according to the IF-THEN rule, the scale and sensitivity factor. ResultsThrough the testing of five healthy people as substitute, the results showed that the accuracy of gait phase recognition for walking on the flat road, walking down the stairs and walking downhill were (95.3±2.4)%, (81.5±6.3)% and (90.7±3.5)%, respectively. ConclusionThe accuracy of recognition basically meets the requirements in this project. This method can be applied in the gait phase recognition of intelligent above-knee prosthetic.
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Objective To establish the method of predicting the vertical ground reaction force (vGRF) during treadmill running based on principal component analysis and wavelet neural network (PCA-WNN). Methods Nine rearfoot strikers were selected and participated in running experiment on an instrumented treadmill at the speed of 12, 14 and 16 km/h. The kinematics data and vGRF were collected using infrared motion capture system and dynamometer treadmill. A three-layer neural network framework was constructed, in which the activation function of the hidden layers was the Morlet function. Velocities of mass center of the thigh, shank and foot as well as joint angles of the hip, knee and ankle were input into the WNN model. The prediction accuracy of the model was evaluated by the coefficient of multiple correlation (CMC) and error. The consistencies between predicted and measured peak GRF were analyzed by Bland-Altman method. Results The CMC between the predicted and measured GRF at different speeds were all greater than 0.99; the root mean square error (RMSE) between the predicted and measured vGRF was 0.18-0.28 BW; and the normalized root mean square error (NRMSE) was 6.20%-8.42%; the NRMSE between the predicted and measured impact forces and propulsive forces were all smaller than 15%. Bland-Altman results showed that the predicted peak errors of propulsive force at 12 km/h and that of impact force and propulsive force at 14 km/h were within the 95% agreement interval. Conclusions The PCA-WNN model constructed in this study can accurately predict the vGRF during treadmill running. The results provide a new method to obtain kinetic data and perform real-time monitoring on a treadmill, which is of great significance for studying running injuries and rehabilitation treatment.
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SUMMARY: As it is currently played, volleyball is a game in which success depends in large measure on the athleticism of the participants. The aim of this research was to point out the importance of the cycle of stretching and shortening in different jumps for elite volleyball players. Thus, it is common for volleyball athletes to place considerable emphasis on jump training. Not surprisingly, overload injuries of the knee and ankle joints, both acute and chronic, occur frequently among volleyball players and are related to the volume of jump training and skill repetition. Understanding the biomechanics of jumping is therefore a prerequisite for designing effective training programs which minimize the risk of overuse injuries that may result from excessive jumping, and the repetitive mechanical loading of muscles and joints that are involved in jump training Muscles acting about a joint function naturally through a combination of eccentric (lengthening) and concentric (shortening) activations. In the lower limb, the stretch-shortening cycle is a reflex arc in which the tendomuscular system acting about the knee or ankle is eccentrically preloaded (stretched) in the loading or impact phase of the jump before concentrically shortening in the push-off or take-off phase.
RESUMEN: Actualmente, el voleibol es un juego en el que el éxito depende en gran medida del atletismo de los participantes. El objetivo de esta investigación fue señalar la importancia del ciclo de estiramiento y acortamiento en diferentes saltos para jugadores de voleibol de élite. Es común que los atletas de voleibol pongan un énfasis considerable en el entrenamiento de salto. No es sorprendente que las lesiones por sobrecarga de las articulaciones de la rodilla y el tobillo, tanto agudas como crónicas, ocurran con frecuencia entre los jugadores de voleibol y estén relacionadas con el volumen de entrenamiento de saltos y la repetición de destrezas. Comprender la biomecánica del salto es, por lo tanto, un requisito previo para diseñar programas de entrenamiento efectivos que minimicen el riesgo de lesiones por uso excesivo que pueden resultar de un salto excesivo y la carga mecánica repetitiva de los músculos y las articulaciones que están involucrados en el entrenamiento del salto. Los músculos que actúan sobre una articulación funcionan de forma natural a través de una combinación de activaciones excéntricas (alargamiento) y concéntricas (acortamiento). En el miembro inferior, el ciclo de estiramiento-acortamiento es un arco reflejo en el que el sistema tendomuscular que actúa sobre la rodilla o el tobillo se precarga (estira) excéntricamente en la fase de carga o impacto del salto antes de acortarse concéntricamente en el despegue o toma. -fase de apagado.
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Humans , Muscle, Skeletal/physiology , Volleyball , Reflex , Biomechanical Phenomena , Muscle Strength , Muscle ContractionABSTRACT
Objective:To explore any changes with age in the center of plantar pressure among normal people after walking.Methods:Fifty healthy subjects were divided into a young group and an elderly group, each of 25. Gait descriptors were collected for each subject using a model AL-600 gait and balance training and evaluation apparatus. The gait descriptors were the center of pressure displacement (COPD), and the COPD in the medial-lateral (COPD-X) and anterior-posterior (COPD-Y) directions before and after 10 and 15 minutes of walking.Results:The average COPD, COPD-X and COPD-Y of the elderly group increased after both 10 and 15 minutes of walking, but among the young group increases were observed only after 15 minutes. The average COPD, COPD-X and COPD-Y of the elderly group were always significantly larger than the young group′s averages.Conclusions:Gait stability among the elderly decreases after as little as 10 minutes of walking, but among the young decreases are observed only after 15 minutes.
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OBJECTIVES: To evaluate the clinical characteristics, ground reaction force (GRF), and function of the plantar muscles and dorsiflexors of the ankle in runners with and without Achilles tendinopathy (AT) and in non-runners. METHODS: Seventy-two participants (42 men, 30 women; mean age: 37.3±9.9 years) were enrolled in this cross-sectional study and divided into three groups: AT group (ATG, n=24), healthy runners' group (HRG, n=24), and non-runners' group (NRG, n=24). Both ankles were evaluated in each group. The American Orthopedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Scale was used for clinical and functional evaluation. GRF was evaluated using force plates and muscle strength was evaluated using an isokinetic dynamometer. RESULTS: The AOFAS scores were lower in the ATG. The strike impulse was higher in the ATG than in the HRG and NRG. However, GRF was similar among the groups. The ATG exhibited lower total work at 120°/s speed than the HRG. The peak torque in concentric dorsiflexion was lower in the NRG than in the ATG and HRG. The peak torque and total work in concentric plantar flexion were lower in the NRG than in the ATG. The peak torque and total work in eccentric plantar flexion were lower in the NRG than in the ATG and HRG. CONCLUSION: Runners with AT showed higher strike impulse, lower muscle strength of the plantar flexors, and higher clinical and functional damage.
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Humans , Male , Female , Adult , Middle Aged , Achilles Tendon , Tendinopathy , Biomechanical Phenomena , Cross-Sectional Studies , Muscle, Skeletal , Torque , Muscle Strength , Ankle , Ankle JointABSTRACT
Objective:To observe the effects of pain relief after acupuncture on walking speed, step length and ground reaction force (GRF) of patients with chronic nonspecific low back pain (CNLBP) during walking. Methods:From May to December, 2019, 28 CNLBP patients were randomly divided into waiting list group (n = 14) and acupuncture group (n = 14). The acupuncture group received acupuncture, 30 minutes a time, three times a week, for four weeks. The waiting list group only received health education after enrollment until four weeks later. Gait analysis was performed with three-dimensional motion system for both groups after enrollment and one month later. The walking speed, step length and GRF characteristic values were recorded and compared, as well as Visual Analogue Score (VAS) for pain. Results:After intervention, The VAS decreased in both groups (t > 2.956, P < 0.05), and was lower in the acupuncture group than in the waiting list group (t = -2.844, P = 0.004). No significant difference in walking speed, step length and GRF characteristic values was found after intervention in both groups (P > 0.05). Conclusion:One month-acupuncture could relief the pain of CNLBP patients, however, it could not improve the performance during walking.
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Objective To explore the influence of biomechanical characteristics of badminton players on sports risk at the moment of foot and ankle landing, so as to provide references basis for avoiding the sports risk of high-frequency and high-intensity landing of ankle joint of beginners. Methods Using three-dimensional force measuring platform and motion capture system, the kinematic and dynamic data of 30 badminton beginners (experimental group) and 30 high-level athletes (control group) at the kick-off (1 step) moment during ankle landing were collected. Results The angles of metatarsal flexion and dorsiflexion in experimental group were significantly smaller than those in control group, and the angles of varus and internal rotation in experimental group were significantly larger than those in control group. The left-right forces in experimental group were significantly larger than those in control group, and there was no significant difference in anterior-posterior force and vertical force between experimental group and control group. The valgus and external rotation torque of experimental group were significantly higher than those of control group, and the internal rotation torque of control group was significantly higher than that of experimental group. Conclusions Compared with beginners, the ankle movement of professional athletes has good dynamic stability and flexibility, the cushioning task can be completed with a smaller range of movement and force in left-right direction, and the angle of metatarsal flexion and dorsiflexion of professional athletes is relatively increased. It is also the embodiment of good training effect, so that the buffer time is slightly longer to prevent the impact of sudden landing of the ankle.
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Objective To analyze the difference in ground reaction force (GRF) between male and female runners and between left and right limbs using the one-dimensional statistical parametric mapping (SPM). Methods Thirty male and female runners participated the running test on force treadmill at the speed of 12 km/h. GRF of consecutive five steps were recorded. The independent-sample t test and paired-sample t test in the SPM package were used to check the male vs female and right limb vs left limb differences. Results Male and female runners showed inter-limb asymmetry in vertical average loading rate (VALR), and the VALR of male runners was significantly higher than that of female runners in the left limb, while no significant differences were found in the right limb. Male and female runners showed significant differences in the right vertical GRF during push-off and medial-lateral GRF during landing, while left medial-lateral GRF presented significant differences during landing and mid stance. Male runners showed right limb vs left limb significance in the anterior-posterior GRF during push-off, vertical GRF during landing and push-off and medial-lateral GRF during landing, while female runners exhibited right limb vs left limb significance in vertical GRF during landing and push-off. Conclusions This study introduced the application of SPM in statistical analysis of GRF, elaborated the procedures and theory, compared the test of time-series data in SPM and discrete value with traditional statistics, and discussed the difference and features in SPM and SnPM, thus providing references for the application in data analysis of sports biomechanics. Comparison in the male vs female and right limb vs left limb revealed the genders and inter-limb symmetrical differences in the landing, mid-stance and push-off phases during stance. The research findings laid the foundation for future investigation of mechanism in running related injuries and strategy of prevention and treatment.
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Objective To observe the effects of electro-acupuncture on loading of lower limb joints in patients with knee osteoarthritis (KOA) during stair climbing and explore the related biomechanical mechanism. Methods Forty patients with KOA were randomly assigned, with 20 patients in observation group (electro-acupuncture group, EA group) and 20 patients in control group (superficial acupuncture group, SA group). Finally 18 patients in each group completed the study. In observation group, seven knee acupuncture points were chosen and patients were connected with electro-acupuncture instrument; while in control group, the electro-acupuncture instrument was connected but not electrified after superficial acupuncture at non-acupoint points. The three-dimensional gait analysis system was used to assess the biomechanical characteristics during stair climbing before and after treatment, including peak vertical force (PFz), vertical impulse (IFz) and symmetry index (SI%). Results After 3 weeks of treatment in EA group, PFz of the right foot during stair ascent and PFz of the left foot during stair descent increased (P＜0.05); IFz of both feet during stair ascent and IFz of the right foot during stairs descent significantly decreased (P＜0.05); no significant differences were found in SI% of peak and impulse (P＞0.05). In SA group, only SI of impulse during stairs ascent increased (P＜0.05). There was no significant difference between two groups before and after treatment (P＞0.05). Conclusions Electro-acupuncture can effectively improve the joint load capacity and reduce the dynamic cumulative load of patients w
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Objective To establish the musculoskeletal multi-body dynamic foot-ground contact model and explore its applicability at different speed. Methods The gait data of the subjects at different speed were collected, and the foot-ground contact model was established based on the full body model from the musculoskeletal multibody dynamic software AnyBody. Then the calculated ground reaction forces (GRFs) and ground reaction moments (GRMs) at different speed (slow walking, normal walking, fast walking and jogging) were compared with the measurements from the force plates. Results The predicted GRFs and GRMs correlated well with the experimental measurements at slow, normal and fast speed (stride speed ranged from 0.69 to 1.68 m/s). The correlation coefficients between predicted and measured GRFs were greater than 0.875 and the correlation coefficients for GRMs were greater than 0.9. Conclusions The developed foot-ground contact model could simultaneously predict GRFs and GRMs with good accuracy, thus eliminating the dependency on force plates. The model could be applied to low-speed gait conditions, such as the elderly and pathological gait.
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In this study, we investigated the relationship of an osteoarthritis of the knee (OA) and a knee pain of single-leg on the bilateral difference of ground reaction force in stepping. The subjects were 29 middle-aged women (mean age 63.7±6.7 years). We categorized them into groups based on the following conditions: osteoarthritis of the knee (OA groups; n = 9), knee pain (KP groups; n = 7), and no pain (NP groups; n = 13). We measured the ground reaction force in a vertical direction when stepping on a platform. The evaluation variables were as follows: peak of ground reaction force at the early stance phase (F1), middle phase (F2), and late phase (F3). We calculated the bilateral difference of ground reaction force of the left and right leg and the affected side and the unaffected side ratio. The result of two way ANOVA, there was a significant difference between the leg in F1 and F3 and the group at F2. The result of comparison between the OA groups and the KP groups, there was no significant difference in the unaffected side and the affected side ratio, those in the OA groups tended to have a load on the unaffected side, while those in the KP groups had a load on the affected side. Therefore, it was suggested that there was the relationship of the OA and a knee pain of single-leg on the bilateral difference of ground reaction force in stepping.
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Objective To study the effect of age on the trajectory of the center of plantar pressure.Methods Twenty-five healthy young people constituted a youth group,while another 25 elderly counterparts formed an aged group.Descriptors of everyone's gait were collected using an AL-600 gait and balance training and evaluation apparatus.The length of the total trajectory of the center of plantar pressure (COPD) was recorded along with the average left and right deviation of the center of plantar pressure (COPD-X) and its average anterior-posterior deviation (COPD-Y) in the heel strike (LR),single plantar stance (SPS) and push-off (PS) phases of striding.Results The average COPD of the aged group was significantly longer than that of the youths.For both groups,the average COPD-X and COPD-Y deviations in SPS were significantly less than those in the LR and PS phases,with no significant difference between them.Compared with the youth group,the average COPD-X in the LR and PS phases and the average COPD-Y in the PS were significantly greater among the aged,but there was no significant difference between the two groups in the average COPD-X in SPS or in the average COPD-Y in the LR and SPS phases.Conclusions The average COPD,COPD-X and COPD-Y increase with age,indicating the higher risk of falling.The changes in each sub-phase of gait are different,but those in the LR and PS phases more reliably reflect stability.
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AbstractIntroduction: The maintenance of balance and body orientation during standing is essential to perform different activities. One of the devices used to measure balance them is the force platform. This device measures the ground reaction force (GRF) and displacement of the center of pressure (COP), both biomechanical parameters involved in human motion. This article proposes a new design for non-commercial low-cost force platforms for scientific research purposes. Methods for calibration and validation are also described. Methods A force platform, developed according to International Standards of Measurement and dedicated to measuring feet contact forces was built for approximately one tenth of the cost of commercial platforms. Calibration was performed by loading known masses, centralized or distributed, on the platform. An experimental study was conducted with four volunteers in different conditions to validate and verify the practical applicability of the device. Results The platform calibration showed an adequate connectivity, linearity and reliable measurement of the variables proposed in this research, being suitable for studies of human postural behavior. Conclusion Based on the validation results, we believe the low-cost platform can be used as stabilometric device to measure postural control and balance in clinical or sports experiments. However future studies will be required to provide a final validation and compare its performance with other force platforms.
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Objective To compare the influence of two fatigue protocols on kinematics of lower extremities as well as time/frequency-domain characteristics of impact force during human landing. Methods A total of 15 trained male athletes (sprint/jumping events) were selected and their kinematics in sagittal/frontal plane and time/frequency-domain characteristics of ground reaction force (GRF) under pre- and post-fatigue conditions with two fatigue protocols (constant speed running, shuttle running + vertical jumping) were collected by the Vicon motion capture system and Kistler 3D force plates. Results (1) Both fatigue protocols showed a significant decrease in the angle of hip and knee joints on the sagittal plane, and an increase in the flexion range of motion (ROM). The running + jumping fatigue protocol showed a significant increase in the flexion ROM of ankle joint, the maximum flexion angular velocity of knee joint (P<0.05), the abduction ROM of hip joint and the maximum abduction angular velocity of hip and knee joints (P<0.05). (2) No significant differences were found in time/frequency-domain characteristics of impact force between pre- and post-tests for both fatigue protocols. The running and running + jumping fatigue protocols showed lower amplitude spectra of the GRF in the frequency domain at 3.51, 8.20 Hz and 1.17, 3.51, 7.03 Hz, respectively (P<0.05). Conclusions Both fatigue protocols can induce a more flexed landing posture of lower extremities under the impact of landing, and the running + jumping fatigue protocol shows a better effect with shorter intervention time, which indicates such fatigue protocol has more advantages from the perspective of experimental methodology. The research findings can provide further references for studying force characteristics after fatigue.
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Objective To compare the influence of two fatigue protocols on kinematics of lower extremities as well as time/frequency-domain characteristics of impact force during human landing.Methods A total of 15 trained male athletes (sprint/jumping events) were selected and their kinematics in sagittal/frontal plane and time/frequency-domain characteristics of ground reaction force (GRF) under pre-and post-fatigue conditions with two fatigue protocols (constant speed running,shuttle running + vertical jumping) were collected by the Vicon motion capture system and Kistler 3 D force plates.Results (1) Both fatigue protocols showed a significant decrease in the angle of hip and knee joints on the sagittal plane,and an increase in the flexion range of motion (ROM).The running + jumping fatigue protocol showed a significant increase in the flexion ROM of ankle joint,the maximum flexion angular velocity of knee joint (P＜0.05),the abduction ROM of hip joint and the maximum abduction an gular velocity of hip and knee joints (P ＜ 0.05).(2) No significant differences were found in time/frequency-domain characteristics of impact force between pre-and post-tests for both fatigue protocols.The running and running + jumping fatigue protocols showed lower amplitude spectra of the GRF in the frequency domain at 3.51,8.20 Hz and 1.17,3.51,7.03 Hz,respectively (P＜0.05).Conclusions Both fatigue protocols can induce a more flexed landing posture of lower extremities under the impact of landing,and the running + jumping fatigue protocol shows a better effect with shorter intervention time,which indicates such fatigue protocol has more ad vantages from the perspective of experimental methodology.The research findings can provide further references for studying force characteristics after fatigue.
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The purpose of this study was to investigate the characteristics of running on self-driven treadmill equipped with curve-shaped bed (TM) from kinematics and kinetics variables by comparing with those obtained on overground running (OG). Eight healthy male subjects run on TM and OG under constant speed condition of 3m/s. Thirty five reflective anatomical landmarkers were attached on the subject according to Plug-in-gait model. Kinematics and kinetics data were recorded during stance phase using VICON MX (200fps) motion capture system and Kistler force plate (1kHz). Running spatio-temporal parameters such as stride length /stride frequency, lower limb joint kinematics and ground reaction force were compared between TM and OG conditions. Significant high stride frequency on TM running was indicated compare with OG condition (P<0.05). Contact time were almost same between TM and OG, whereas in vertical ground reaction force, non-first impact force as well as lower average loading rate were indicated in TM compared to OG (P<0.05). Lower joint kinematics were significantly different between TM and OG running during first 20% stance phase of normalized stance time. Hip and knee flexion angular velocities were larger in OG than TM (P<0.05). These results suggest that TM running causes lowed intensity for lower limb joints during stance phase, which might be applicable for prevention of running injury.
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The purpose of the present study was to examine the importance of the agonist muscle activity of the post-impact 30 ms phase during drop jump (DJ) for effective rebound performance by comparing those of sprint runners and swimmers. The eight sprint runners (SPRINT) and twelve swimmers (SWIM) were participated in this study. They performed DJ from a 0.3-m height box with maximal rebound efforts. Electromyograms (EMG) of the lower leg muscles (medial gastrocnemius [MG], soleus [SOL] and tibialis anterior [TA]), and vertical ground reaction force together with kinematic data were measured simultaneously during DJ. In addition, the onsets of fascicle stretching of the MG and SOL muscles were measured by using high-speed ultrasonography (521Hz) during DJ. The onsets of the fascicle stretching of SOL during DJ were not significantly different between SPRINT and SWIM (15 ± 7 ms and 16 ± 6 ms, respectively). During DJ, SPRINT showed onset of the SOL EMG before the ground contact (-26 ± 19 ms). Meanwhile, SWIM showed the onset of the SOL EMG after the ground contact of DJ (16 ± 19 ms). These results suggest that the SOL muscles for SWIM cannot be fully-activated during the braking phase. Consequently, the rate of force development during the braking phase of DJ and subsequently rebound height could be reduced in SWIM.
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Patellofemoral pain syndrome (PFPS) is a prevalent clinical condition and it affects gait behavior. Braking and propulsive impulses are important biomechanical parameters obtained from ground reaction forces (GRF), which combine the amount of force applied over a period of time. The aim of this study was to evaluate these impulses while walking up and down stairs in healthy controls and PFPS individuals. The results did not reveal significant differences in braking and propulsive impulses between groups during these activities. Thus, the painful condition on a simple functional activity was insufficient to change the motor strategy to walking up or down the stairs...
"Análise dos impulsos de frenagem e de propulsão em indivíduos com síndrome da dor femoropatelar durante subida e descida de degraus." A síndrome da dor femoropatelar (SDFP) é uma condição clínica prevalente e que afeta o comportamento da marcha. Impulsos de frenagem e propulsão são importantes parâmetros biomecânicos obtidos a partir da força de reação do solo que combinam a quantidade de força aplicada sobre um período de tempo. O objetivo deste estudo foi avaliar esses impulsos durante a subida e descida de degraus em indivíduos controle saudáveis e com SDFP. Os resultados não revelaram diferenças significativas nos impulsos de frenagem e propulsão entre os grupos durante essas atividades. Assim, a condição dolorosa em uma atividade funcional simples foi insuficiente para modificar a estratégia motora de descer ou subir degraus...
"Análisis de los impulsos de frenado y propulsión en la personas con síndrome de dolor patelofemoral durante la actividad de subir y bajar un escalón." El Síndrome de dolor patelofemoral (SDPF) es una condición médica prevalente que afecta al comportamiento de la marcha. Impulso de propulsión y de frenado son parámetros biomecánicos importantes obtenidos a partir de la fuerza de reacción del suelo que combinan la cantidad de fuerza aplicada durante un período de tiempo. El objetivo del estudio fue evaluar estos impulsos durante las actividades de subir y bajar un escalón en sujetos sanos y con SDP. Los resultados no mostraron diferencias significativas en los impulsos de frenado y propulsion entre los grupos durante las actividades. Por lo tanto, Por lo tanto, la condición dolorosa en una actividad funcional simple, no fue suficiente para cambiar la estratégia de subir y bajar un escalón...
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Humans , Female , Adult , Patellofemoral Pain Syndrome/physiopathology , Exercise Test/methodsABSTRACT
O objetivo do presente estudo foi comparar a absorção de impacto durante a marcha descalço e com tênis e coturno fornecidos pelo Exército Brasileiro. A amostra foi composta por 20 soldados saudáveis recém-incorporados sem sintomas ou lesões musculoesqueléticas ou neurológicas que interferissem na marcha. Os sujeitos foram instruídos a caminhar em uma plataforma de madeira de 10 metros de comprimento por um metro de largura, com duas plataformas de força (Bertec, EUA) embutidas no centro. O componente vertical da força de reação do solo foi avaliado durante a marcha nas situações tênis, coturno e descalço. O sistema de cinemetria (Qualysis, Suécia) foi utilizado para medir a velocidade da marcha em cada situação de teste. O primeiro pico de força (PPF), o tempo para atingir o PPF (T_PPF), pico transiente de impacto (IPF) e a taxa de aceitação do peso (TAP) entre 10% e 30%, 30% e 50%, 50% e 70%, 70% e 90% e 10% e 90% do PPF foram avaliadas. O T_PPF foi em média 1s menor (p < 0,0001), o IPF e a TAP entre 10% e 30% do PPF foram maiores (p < 0,0001, ambos) descalço comparados a marcha com tênis e coturno. Não foi observado diferença estatística nas outras variáveis estudadas nas três condições de teste, bem como em nenhuma variável na comparação entre tênis e coturno. Os calçados avaliados são eficientes em reduzir o impacto durante a marcha por atrasar em média 1 s o tempo em que o PPF foi atingido, reduzir o IPF e a TAP nos primeiros 30% do PPF
This study aimed at comparing shock absorption during gait while walking barefoot, tennis shoes and military boots. Twenty healthy soldiers without neurologic or musculoskeletal disorders were evaluated. Subjects walked 10 meters along a straight and level walkway at a comfortable speed in barefoot condition and using tennis shoes and military boots. Two force platforms (Bertec, EUA) were placed in serial at the middle of the walkway used to measure the ground reaction forces (GRF). The kinematic system (Qualysis, Sweden) was used to measure gait speed in each test condition. The first peak of force (FPF) of the vertical component of the GRF, time to reach to FPF (T_FPF), transient impact peak force (IPF) were evaluated and the weight acceptance rate at 10% to 30%, 30% to 50%, 50% to 70%, 70% to 90% and 10% to 90% of FPF. T_FPF was 1 s shorter (p < 0.0001), as well as IPF and weight acceptance rate at 10% to 30% in barefoot was higher (p < 0.0001, both) than tennis shoes and military boots gait patterns. None statistical difference was found in the others analyzed variables, even as in the tennis shoes and military boots comparisons. The analyzed footwear delayed the FPF impact during gait, reduce the IPF and the weight acceptance phase during 10% to 30% of FPF, being efficient in reduce impact forces during gait