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Sports fatigue of the lower limbs is one of the important factors affecting sports performance. How to improve the anti-fatigue ability of the lower limbs during endurance exercise is the focus of the research field of human sports biomechanics. This study systematically reviewed the relevant literature on transcranial direct current stimulation (tDCS) intervention on lower limb endurance performance, summarized the effect of tDCS on lower limb endurance performance, and analyzed the influencing factors and potential mechanisms. The results showed that: tDCS intervention has a significant effect on the endurance performance of the whole lower limbs, but there is no unified conclusion on the effect on the endurance performance of the knee joint. The researchers deem that tDCS can increase the excitability of the primary motor cortex and reduce the activation of the supplementary motor area and the premotor area to producing a lower rating of perceived exertion, but cannot affect the perception of exercise-induced pain, and stimulation protocols varied across studies, which may be partly responsible. This study can provide a theoretical basis for exploring the central mechanism of tDCS to improve endurance performance, formulating rehabilitation and sports training programsfor different groups of people, and developing new stimulation equipment to enhance the human body’s anti fatigue ability.
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Objective To investigate the mechanical properties of Achilles tendon (AT) during running under different shoe conditions (minimalist vs conventional shoes). MethodsSixteen healthy male runners with habitual rearfoot strike patterns were recruited to complete the running trials at the speed of 3.16~3.50 m/s under two shoe conditions. The cross-sectional area of the AT was obtained by ultrasound imaging. Sagittal plane ankle kinematics and ground reaction forces were recorded by motion capture system and three-dimensional force platform simultaneously. Mechanical properties of the ankle and AT were calculated. Paired t test was used to compare the effects of two shoe conditions on various parameters (ankle angle, strike angle, AT force, stress, strain, etc). ResultsCompared with conventional shoes, foot inclination angle was significantly reduced by 39.9% with minimalist shoes. Obvious increase in ankle moment, peak AT force, peak AT loading rate, average loading rate, and obvious decrease in time to peak AT force were observed with minimalist shoes. Peak AT stress, peak AT strain and corresponding stress rate, peak strain rate also increased significantly with minimalist shoes. ConclusionsGreater AT loading was observed when runners with habitual rearfoot strike pattern in conventional shoes begin to wear minimalist shoes. Therefore, a gradual transition to minimalist shoes was recommended for them so as to improve the ability to load adaptively.
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Objective To explore the correlation between foot morphology and toe/metatarsophalangeal joint muscle strength. Methods Twenty-six male recreational runners were recruited. Foot length, truncated foot length, foot width, navicular height, dorsum height at 50% of the foot length, metatarsophalangeal joint strength, tensile force of the first and remaining four toes were measured by using digital caliper, metatarsophalangeal joint strength tester and dynameter, respectively. Partial correlations were used to analyze the correlation between foot morphology and foot muscle strength. ResultsWith adjusted age and body mass index (BMI), the foot width in standing position and truncated foot length in sitting and standing position were positively correlated to tensile force of the first toe; the foot length, foot width and truncated foot length were positively correlated to tensile force of the remaining four toes in both positions, and the arch height index in sitting position was negatively associated with tensile force of the remaining four toes; the foot width was positively correlated to metatarsophalangeal joint strength in both positions. Conclusions The longer foot length, foot width, truncated foot length, and the lower arch height in normal range might be related to the larger foot muscle strength. The consideration of the differences in foot morphological characteristics in different positions during the measurement of foot morphology can provide references for predicting foot muscle strength and preventing foot injury.
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The technical deficiencies in traditional medical imagining methods limit the study of
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Ankle , Ankle Joint , Biomechanical Phenomena , Range of Motion, Articular , TechnologyABSTRACT
The research progress in fatigue protocols and biomechanics of lower extremity and its relationship with injury induced by exercise-induced fatigue was reviewed in this paper. At present, fatigue protocols can be divided into the traditional fatigue-induced protocol and the functional fatigue-induced protocol under laboratory condition. The former mainly includes power-cycling model, treadmill run model and step-ups model, while the latter is closer to what is experienced during competition, which is usually shown as multidirectional movements. In addition, the biomechanical measures of exercise-induced fatigue mainly include kinematics, ground reaction force, joint mechanics and electromyography. Different fatigue protocols do not uniformly produce alterations in lower limb biomechanical factors. The refinement of fatigue protocols and specific indicators should be considered in future studies, in order to compare the induced effects of fatigue protocols and provide references for the selection of fatigue protocols in laboratory tests. Meanwhile, the relationship between the response of brain-nerve system and the activation of musculoskeletal system for specific athletic task should be focused, so as to understand the difference of biomechanical mechanisms between fatigue protocols and further explore the effect of exercise-induced fatigue on sports injuries.
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Objective To examine the effects of shoe cushioning on impact characteristics, kinematics and dynamics of lower extremities before and after neuromuscular fatigue during drop landing. Methods Fifteen trained male athletes were required to execute three successful trials of drop landing from a 60-cm platform before and after fatigue protocol. The impact force, loading rate, lower extremity kinematics, joint moment, joint stiffness were compared. Results Before fatigue, highly-cushioned shoes reduced the loading rate at heel before fatigue, and the time to peak loading rate of heel was significantly shorter than that of control shoes. After fatigue, highly-cushioned shoes significantly reduced the peak impact force and loading rate at heel, loading rate at forefoot. Meanwhile the time to peak impact force and peak loading rate at heel were significantly longer, and the contact and minimum angle of ankle were significantly greater. No significant changes were found in lower extremity stiffness, peak moment and joint stiffness of ankle. Conclusions In the situation where neuromuscular activity is reduced, highly-cushioned shoes can effectively attenuate the impact, thereby helping to avoid or reduce the potential impact damage after fatigue.
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Objective By establishing the intervention mode of 12-week gait retraining (GR) (with the specific aim of changing the habitual running gait), to determine the changes of vertical ground reaction force (vGRF), kinematics and dynamics of hip, knee, ankle joints, as well as stiffness of lower limbs in running before and after GR, and to explore the influence of running posture transformation on impact force and lower limb biomechanics. Methods Vicon motion capture system and Kistler 3D force measurement platform were used to collect the GRF and marker track of 30 runners (15 in experimental group and 15 in control group) before and after GR with the minimalist shoes at a speed of 12 km/h±5%. Results A total of 17 subjects (9 in experimental group and 8 in control group) completed the GR. After GR, the maximum loading rate of both groups decreased significantly, and the maximum loading rate of experimental group was lower than that of control group. The foot strike angle in experimental group decreased significantly after GR, and the plantarflexion angle and hip joint angular extension velocity increased in both groups. The force moment of ankle joint increased in experimental group, and the stiffness of lower limbs was significantly improved in both groups. Conclusions A 12-week GR exercise intervention model was successfully established, with 78% conversion rate (from rearfoot strike to forefoot strike). GR can effectively avoid the peak of impact force, reduce the maximum loading rate, increase the lower limb stiffness, and thus reduce or even avoid the risk of running injury caused by impact force and may provide a possibility for the improvement of running economy.
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In recent years, the effects of the neuro-biomechanical ergogenic technology on improving and enhancing human function and physical movement performance have widely attracted certain attentions. This review summarized the recent achievements in the effects of non-invasive brain stimulation (NIBS) and biomechanical ergogenic technology based on sports equipment on human physical performance, and further explored the possible mechanisms for improving and promoting human physical performance. The obtained preliminary evidence based on animal experiments and biomechanical researches on neuromotor control under multi-joint movement were also summarized, so as to explain the coordinated development of human function enhancement at cerebral cortex regulation and neuromuscular coordinated control levels, and interpret its integration with sports equipment. This review ultimately provided certain references for the future frontier development and research position of neuro-biomechanics and human sports biomechanics.
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Achilles tendon is the key structure to connect the heel and foot plantar flexors and transmit the force from the leg triceps muscle, which is the key to storing and releasing energy storage during running and jumping. At present, the primary causes of Achilles tendon injury are non-homologous loading during stance phase and deficient recovery after overload. However, the relevant measures to prevent Achilles tendon injury cannot achieve full recovery. This paper reviewed the research progress of Achilles tendon’s motor function and its application in biomechanics domestically and internationally, reconsidering the role of Achilles tendon in human running and jumping which included anatomical structure of the Achilles tendon, the relationship between internal force and external force, and the effective training program. The key for future research on motor function of Achilles tendon is to improve its mechanical properties, keep the increased load in a better range and ultimately improve motion performance and reduce sports injury from the source.
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Objective To explore the relationship between shoe comfort and foot loading characteristics in two types of basketball shoe during different basketball footwork. Methods Two Kistler 3D force platforms and Medilogic insole plantar pressure system were used to collect the kinetic data of 12 healthy male basketball players wearing two types of basketball shoe (shoe L and shoe N) during three varieties of basketball footwork (side-step cutting, 90° varied-direction running, lay-up), including peak impact force, peak loading rate, and peak plantar pressure. The perception test scale was used to evaluate comfort for two types of basketball shoe during three kinds of basketball footwork. Results For the two types of basketball shoes, there was no significantly difference in the impact force during the three kinds of basketball footwork, but the plantar pressure of shoe L was significantly greater than that of shoe N during side-step cutting and lay-up. Shoe N was significantly more comfortable than shoe L, with a significant difference in preference (heel stability, heel responsiveness, forefoot cushioning, heel cushioning, and overall liking) and intensity (forefoot and heel cushioning) on a dynamic scale. Conclusions The plantar pressure and comfort show significant differences in the two types of shoes; however, none of the shoes appeared definitively superior in the two evaluations. It is suggested that the biomechanical characteristics of the shoes and the subjective evaluation of the athletes should be considered in the overall design and evaluation of specialized shoes.
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Objectives To explore the effect of fatigue intervention on biomechanics of lower extremity and performance during the stretch-shortening cycle(SSC) movement-drop jumps(DJ).Methods The Vicon motion capture system and 3D Kistler force plates were used to collect sagittal plane kinematics and ground reaction force data synchronously of a total of fifteen trained male athletes under pre-and post-fatigue conditions with shuttle running + vertical jumping fatigue protocol.The joint angle,joint moment,power,work,and leg/joint stiffness were compared before and after fatigue.Results After fatigue,the maximum height of DJ decreased(P＜0.05),while the touchdown angle and the range of motion(△θ) of knee and ankle joints,as well as the occurrence time for the eccentric,concentric and total phase increased(P＜0.05).However,the maximum push-off moment and power of knee reduced(P＜ 0.05).The stiffness of knee and ankle joints during the eccentric phase reduced,resulting in the reduction of the leg stiffness(P＜0.05).Moreover,the energy absorption and net energy of the ankle joint decreased;meanwhile,the energy contribution of the knee joint decreased during the eccentric phase of a DJ task.Conclusion Fatigue changes the movement pattern,decreasing the control ability of the lower extremity especially in the knee and ankle joint,and results in decreased performance.Moreover,the decrease of leg,ankle and knee stiffness and the corresponding energy can be used as sensitive indexes to evaluate the performance of drop jumps in a fatigued condition.
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Objective To investigate the influence of barefoot running and shod running with different foot-strike patterns on characteristics of plantar pressures and ground reaction force (GRF).Methods Kistler force plates and Medilogic insole plantar pressure system were used to collect the kinetic data from a total of 12 healthy male volunteers under shod and barefoot conditions with heel strike and forefoot strike at the speed of 3 m/s,including the GRF,the peak impact force,the maximum loading rate,the peak plantar pressure and impulse.Results (1) Shod running with heel strike significantly reduced the maximum loading rate and extended the time to reach the peak impact force.Under forefoot strike pattern,shod running significantly increased the maximum push-off force than barefoot running.(2) More plantar pressure parameters were influenced by the foot-strike patterns as compared to those under the shod conditions,and there was a significant difference in the peak pressure and the time to reach the peak pressure in the mid-foot and heel region between two foot-strike patterns.Conclusions The foot-strike pattern shows a more obvious influence on plantar pressure during jogging than the shod conditions.Shod running with heel strike can reduce the impact load,while barefoot running with forefoot strike can cause an excessive concentration of plantar pressure on the forefoot region,indicating that a suitable pair of sports shoes is needed for both foot-strike patterns to reduce the plantar pressure during jogging.
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BACKGROUND:The classification and treatment of subtrochanteric fracture experienced a long process of development. Surgical treatment was currently used popularly, including extramedulary and intramedulary fixation. It should be selected according to the type of fracture and clinical practice, and it is inconclusive in the clinic. OBJECTIVE:To summarize the study and present application of intramedulary and extramedulary fixation in the subtrochanteric fracture in recent years. METHODS:The first author researched two books, and retrieved PubMed, Wanfang Database, and Chinese Journal Ful-text Database for articles about clinical trials on fixation for subtrochanteric fractures, and the safety and efficacy of fixation for subtrochanteric fractures published until March 2014. A total of 42 clinical studies on type, intramedulary and extramedulary fixations were selected. RESULTS AND CONCLUSION:With the progress of fixation methods of subtrochanteric fracture, there was a great progress in improving the rate of fracture healing and reducing hip malunion, and limited mobility. Whether extramedulary fixation, intramedulary fixation or arthroplasty, clinical reports have achieved satisfactory results at present. The intramedulary fixation was stil dominated among various therapeutic methods. However, the type of fracture, age and osteoporosis fractures were different in patients. There was no uniform standard of the specific choice of surgical approach, which stil should be further studied. Authors believed that when fracture line was below the lesser trochanter, interlocking intramedulary nail could be used. High subtrochanteric fracture could utilize proximal femoral nail anti-rotation. However, if the medulary cavity was narrow, the fracture was involved in the greater trochanter or piriformis fossa area, locking proximal femoral plate or less invasive stabilization system could be employed. No matter intramedulary or extramedulary fixation, minimal invasion and biological fixation were the present trend of development. The new minimaly invasive techniques and internal fixation are stil the goal. Although intramedulary fixation has advantages, but cannot completely replace the current extramedulary fixation. It is important to have a perfect surgery plan, standardized surgical approach and long-term postoperative folow-up, in order to achieve better clinical outcomes.
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<p><b>OBJECTIVE</b>To analyze and discuss the source and epidemic disposition of human infection with avian influenza A (H10N8) virus.</p><p><b>METHODS</b>Epidemiological surveys were used to collect related data and RT-PCR was applied to detect the specimens collected from cases, close contacts related exposure to live poultry markets. Data were analyzed descriptively.</p><p><b>RESULTS</b>Three cases were discovered by surveillance on patients with severe pneumonia, two of the three died, but one in the hospital with the course over 6 months. All the three cases had histories of exposure to live poultry or related markets. Lower respiratory tract gargle aspirate samples of 3 patients were detected by Nanchang Municipal Center for Disease Control and Prevention (CDC) and Jiangxi Provincial CDC, and the results showed the influenza 2009pdmH1, H3, H5, H7, H9 subtypes negative. Specimen of patient 1 and 2 was positive for influenza A universal primers. Specimen of patient 3 was positive for H10N8 detected by Chinese National Influenza Center. All 33 close contacts of the patients were negative for H10N8 virus. Positive rate of the total poultry environmental specimens collected from the cases exposure markets was 5.19%. No new cases were found, after the prevention and control messages were implemented.</p><p><b>CONCLUSION</b>Three cases of H10N8 avian influenza virus infection province might be associated with exposure to live poultry market in Jiangxi.</p>
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Animals , Humans , China , Epidemiology , Commerce , Epidemics , Influenza A Virus, H10N8 Subtype , Influenza in Birds , Epidemiology , Influenza, Human , Epidemiology , Virology , Pneumonia , Virology , Poultry , Virology , Retrospective Studies , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
Objective To analyze and discuss the source and epidemic disposition of human infection with avian influenza A(H10N8)virus. Methods Epidemiological surveys were used to collect related data and RT-PCR was applied to detect the specimens collected from cases,close contacts related exposure to live poultry markets. Data were analyzed descriptively. Results Three cases were discovered by surveillance on patients with severe pneumonia,two of the three died,but one in the hospital with the course over 6 months. All the three cases had histories of exposure to live poultry or related markets. Lower respiratory tract gargle aspirate samples of 3 patients were detected by Nanchang Municipal Center for Disease Control and Prevention (CDC) and Jiangxi Provincial CDC,and the results showed the influenza 2009pdmH1,H3,H5,H7,H9 subtypes negative. Specimen of patient 1 and 2 was positive for influenza A universal primers. Specimen of patient 3 was positive for H10N8 detected by Chinese National Influenza Center. All 33 close contacts of the patients were negative for H10N8 virus. Positive rate of the total poultry environmental specimens collected from the cases exposure markets was 5.19%. No new cases were found,after the prevention and control messages were implemented. Conclusion Three cases of H10N8 avian influenza virus infection province might be associated with exposure to live poultry market in Jiangxi.
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Objective To analyze and discuss the source and epidemic disposition of human infection with avian influenza A(H10N8)virus. Methods Epidemiological surveys were used to collect related data and RT-PCR was applied to detect the specimens collected from cases,close contacts related exposure to live poultry markets. Data were analyzed descriptively. Results Three cases were discovered by surveillance on patients with severe pneumonia,two of the three died,but one in the hospital with the course over 6 months. All the three cases had histories of exposure to live poultry or related markets. Lower respiratory tract gargle aspirate samples of 3 patients were detected by Nanchang Municipal Center for Disease Control and Prevention (CDC) and Jiangxi Provincial CDC,and the results showed the influenza 2009pdmH1,H3,H5,H7,H9 subtypes negative. Specimen of patient 1 and 2 was positive for influenza A universal primers. Specimen of patient 3 was positive for H10N8 detected by Chinese National Influenza Center. All 33 close contacts of the patients were negative for H10N8 virus. Positive rate of the total poultry environmental specimens collected from the cases exposure markets was 5.19%. No new cases were found,after the prevention and control messages were implemented. Conclusion Three cases of H10N8 avian influenza virus infection province might be associated with exposure to live poultry market in Jiangxi.