Basic biomechanics of the lower extremity

This article describes common principles of biomechanics for running, jumping, and kicking. These activities form the basis for much of sports activity. Understanding human movement allows the physician to prescribe appropriate prevention, treatment, and rehabilitation to patients.     

The effect of equalizing landing task demands on sex differences in lower extremity energy absorption

Background

Less lean mass and strength may result in greater relative task demands on females compared to males when landing from a standardized height and could explain sex differences in energy absorption strategies. We compared the magnitude of sex differences in energy absorption when task demands were equalized relative to the amount of lower extremity lean mass available to dissipate kinetic energy upon landing.

Methods

Male–female pairs (n = 35) were assessed for lower extremity lean mass with dual-energy X-ray absorptiometry. Relative task demands were calculated when landing from a standardized height. Based on the difference in lower extremity lean mass within each pair, task demands were equalized by increasing the drop height for males. Joint energetics were measured while landing from the two heights. Multivariate repeated measures ANOVAs compared the magnitude of sex differences in joint energetics between conditions.

Findings

The multivariate test for absolute energy absorption was significant (P < 0.01). The magnitude of sex difference in energy absorption was greater at the hip and knee (both P < 0.01), but not the ankle (P = 0.43) during the equalized condition compared to the standardized and exaggerated conditions (all P < 0.01). There was no difference in the magnitude of sex differences between equalized, standardized and exaggerated conditions for relative energy absorption (P = 0.18).

Interpretation

Equalizing task demands increased the difference in absolute hip and knee energy absorption between sexes, but had no effect on relative joint contributions to total energy absorption. Sex differences in energy absorption are likely influenced by factors other than differences in relative task demands.     

Lower extremity joint coupling during running: a current update

Background. The relationship between lower extremity mechanics and injury is not well understood. However, joint coupling studies are beginning to emerge, which may lend further insight into running biomechanics.

Purpose. To provide a current review of the research examining lower extremity joint coupling in running.

Summary. There are various techniques utilized to measure joint coupling, including joint timing, rearfoot eversion/tibial internal rotation ratios, continuous relative phase calculations, and vector coding. The study of joint coupling is of particular interest as it may pertain to running injuries. There is some evidence that joint coupling may be altered with orthotics and/or with footwear. Most studies have included a relatively small sample size and larger scale studies are needed to quantify normal ranges for many of the coupling measures. In addition, prospective studies are needed to clarify the relationship to injury.

Relevance It is hoped that this update will serve as a review of the current state of thought regarding lower extremity joint coupling during running. As greater insight into the role of joint coupling in injuries is gained, more optimal intervention and prevention strategies can be developed to minimize injury risk.     

The effect of an inclined landing surface on biomechanical variables during a jumping task

BACKGROUND: Professional dancers sustain a high number of injuries. Epidemiological studies have suggested that performing on inclined "raked" stages increases the likelihood of injury. However, no studies have examined if biomechanical differences exist between inclined and flat surfaces during functional tasks, such as landing from a jump. Such differences may provide a biomechanical rationale for differences in injury risk for raked stages. METHODS: Eight professional dancers performed drop jumps from a 40cm platform on flat and inclined surfaces while forces, lower extremity kinematics, and electromyographic activity were collected in a controlled laboratory environment. FINDINGS: Dancers landed on the laterally inclined surface with significantly higher knee valgus (4 degrees ), peak knee flexion (9 degrees ), and medial-lateral ground reaction force (GRF) (13.4% body weight) compared to the flat condition. The posterior GRF was higher in the anterior inclined condition compared to the flat condition. In the anterior inclined condition, subjects landed with 1.4 degrees higher knee valgus, 4 degrees more plantarflexion at initial contact, and 3 degrees less dorsiflexion at the end of landing. INTERPRETATION: Biomechanical variables that have been suggested to contribute to injury in previous studies are increased in the inclined floor conditions. These findings provide a preliminary biomechanical rationale for differences in injury rates found in observational studies of raked stages.     

The effect of lower extremity fatigue on shock attenuation during single-leg landing

BACKGROUND: The forces that are imposed on the body due to landings must be attenuated primarily in the lower extremity. Muscles assist in the absorption of these forces, and it has been shown that a fatigued muscle decreases the body's ability to attenuate shock from running. The purpose of the study was to determine the effect of lower extremity fatigue on shock attenuation and joint mechanics during a single-leg drop landing. METHODS: Ten active male participants were recruited (eight used for analysis). Each participant took part in a fatigue landing protocol. This protocol included cycles of a drop landing, a maximal countermovement jump, and five squats, repeated until exhaustion. Accelerometers attached to the skin measured tibia and head accelerations. Lower extremity kinematics were collected using an electromagnetic tracking system and kinetics were collected using a forceplate. A repeated-measures ANOVA (P<0.05) was performed on each of the dependent variables across the cycles of the fatigue protocol. FINDINGS: Fatigue was induced, however there was no significant change in shock attenuation throughout the body. Hip and knee flexion increased and ankle plantarflexion decreased at touchdown with fatigue. Hip joint work increased and ankle work decreased. INTERPRETATION: This change in work distribution is thought to be a compensatory response to utilize the larger hip extensors that are better suited to absorb the mechanical energy of the impact. The results suggested that the lower extremity is able to adapt to fatigue though altering kinematics at impact and redistributing work to larger proximal muscles.     

Gender differences in lower extremity kinematics,kinetics and energy absorption during landing

OBJECTIVE: To determine whether gender differences exist in lower extremity joint motions and energy absorption landing strategies between age and skill matched recreational athletes. DESIGN: Mixed factor, repeated measures design. BACKGROUND: Compared to males, females execute high demand activities in a more erect posture potentially predisposing the anterior cruciate ligament to greater loads and injury. The preferred energy absorption strategy may provide insight for this performance difference. METHODS: Inverse dynamic solutions estimated lower extremity joint kinematics, kinetics and energetic profiles for twelve males and nine females performing a 60 cm drop landing. RESULTS: Females demonstrated a more erect landing posture and utilized greater hip and ankle joint range of motions and maximum joint angular velocities compared to males. Females also exhibited greater energy absorption and peak powers from the knee extensors and ankle plantar-flexors compared to the males. Examinations of the energy absorption contributions revealed that the knee was the primary shock absorber for both genders, whereas the ankle plantar-flexors muscles was the second largest contributor to energy absorption for the females and the hip extensors muscles for the males. CONCLUSIONS: Females may choose to land in a more erect posture to maximize the energy absorption from the joints most proximal to ground contact. RELEVANCE: Females may be at a greater risk to anterior cruciate ligament injury during landing due to their energy absorption strategy.     

Gender differences in lower extremity gait biomechanics during walking using an unstable shoe

Background

In recent years several unstable shoe designs that cause increased instability at the ankle joint have been developed with the aims of training static and dynamic posture and postural control. However, earlier research found significant gender differences in the generation of ankle torque and in the reaction times after a perturbation. Therefore it is possible that men and women are affected differently by the instability that unstable shoes create. The purpose of this study was to investigate if gender differences exist a) during bilateral quiet stance or b) in lower extremity gait kinematics and kinetics when using unstable shoes.

Methods

Seventeen females and seventeen males were included in this study. Masai Barefoot Technology® shoes were used as test shoes. Center of pressure excursion was recorded during 30 s bilateral quiet stance trials using a force plate. Joint angles, resultant joint moments and joint moment impulses during walking were determined using standard gait analysis methods.

Findings

In bipedal stance, female subjects had significantly greater anterior–posterior center of pressure excursion than male subjects. In the stance phase of the gait cycle gender differences were found in the ankle joint moments which had not been reported in earlier studies using barefoot or normal shoe conditions.

Interpretation

The results suggest that women and men use different strategies to control the ankle joint when standing or walking in unstable shoes. Gender effects should therefore be taken into consideration if functional or therapeutic effects of unstable shoes are assessed.     

Trunk and lower extremity biomechanics during sit-to-stand after stroke: A systematic review

ObjectivesThis systematic review aimed to pool available evidence of differences in trunk and lower extremity biomechanics during the different phases of a sit-to-stand (STS) task between persons with stroke and to healthy controls.MethodsFour electronic databases (Medline, Web of Science, EMBASE, and Cochrane Library) were systematically searched up to, and including, December 2021. Studies were included if they investigated kinematic, kinetic and/or electromyographic outcome measures of adults with stroke during STS and compared results with healthy controls. Data from eligible studies were categorized according to STS subphases if reported (Phase I: Movement onset to seat-off; Seat-off; Phase II: Seat-off to movement termination; Whole task [if no subtasks reported]). The Newcastle-Ottawa Scale was used to assess risk of bias.ResultsTwenty-one studies were included in this systematic review. Methodological quality ranged from 13% to 75%; mean score was 55%. The findings of this systematic review suggest that after stroke, people rise to stand (phase I) with increased lateral trunk flexion and displacement of the center of pressure (COP) towards the non-paretic side, decreased anterior pelvic tilt, decreased hip flexion and altered timing of lower limb muscle activation. In addition, during phase II, lateral pelvic translation and weight distribution asymmetry was increased, knee extension velocity was decreased and delayed, stabilization was decreased and COP velocity was increased compared with healthy subjects.ConclusionsThis systematic review clearly showed changes in kinematics, kinetics and muscle recruitment after stroke, with differences between the different phases of STS. Therapeutic interventions should focus on subphases of this functional task to optimize performance in daily living.     

Effects of toning shoes on lower extremity gait biomechanics

Background

The Reebok Easy Tone shoe concept was developed to induce instability during walking and standing with the primary purpose of increasing muscle activity of the lower extremity muscles. To the authors' knowledge, no scientific work has been published, which analyzed neuromuscular and biomechanical effects when walking and standing with Reebok Easy Tone shoes. Therefore, the purpose of this study was to investigate the immediate effects of using such footwear on gait biomechanics for the lower extremity in healthy participants.

Methods

Five healthy female and seven healthy male participants volunteered to participate in this study. During quiet standing, centre of pressure excursion was determined. 3D gait analyses were performed with simultaneously collecting surface electromyography data of the leg muscles when walking with regular shoes and with Reebok Easy Tone shoes.

Findings

Centre of pressure excursion did not show any significant differences. For walking, only slight differences were found in kinematics and kinetics. When walking with Reebok Easy Tone shoes, the first vertical peak of the ground reaction force was significantly increased as well as the maximum plantarflexion moment during initial contact and loading response. Mean muscle activation for vastus medialis and lateralis showed an increase during the second half of stance, but failed to reach significance.

Interpretation

Results of this study did not show any increased instability during standing and only a slight increase of vastii activity during stance. Thus, the marketing claims that “toning shoes” could serve as a sort of training devices for lower limb muscles during walking, cannot be supported.     

Lower extremity mechanics of females with and without patellofemoral pain across activities with progressively greater task demands

BACKGROUND: Patellofemoral pain is commonly associated with lower extremity joint rotations that decrease retropatellar contact area and subsequently increase retropatellar stress during weightbearing activities. People with patellofemoral pain are thought to be capable of avoiding such harmful mechanics during activities with low external demands. However, this may not be possible during more demanding activities. The purpose of this study was to analyze lower extremity mechanics in females with and without patellofemoral pain during three different activities. Specifically, we sought to determine if differences between groups increase with increasingly demanding activities. METHODS: 20 females with patellofemoral pain and 20 healthy female controls performed single leg squats, running, and repetitive single leg jumps as their three-dimensional lower extremity mechanics were recorded. Transverse and frontal plane hip and knee kinematics were compared between groups for all activities. FINDINGS: Differences in the variables of interest between groups did not generally depend on the nature of the activity. The patellofemoral pain group performed all three activities with 4.3 degrees greater knee external rotation (P=0.06), 3.5 degrees greater hip adduction (P=0.012), and 3.9 degrees decreased hip internal rotation with respect to the control group (P=0.01). INTERPRETATION: These results suggest that females with patellofemoral pain do not employ different mechanics as demand of the activity increases. Rather, females with patellofemoral pain seem to demonstrate similar abnormal lower extremity mechanics across a variety of activities.     

Lower extremity venous imaging for the echocardiologist

Cardiologists who are familiar with the techniques and the performance of echocardiography can easily learn how to study the lower extremity veins in their patients by using ultrasound imaging combined with pulsed-wave Doppler echocardiography (duplex scanning). In particular, duplex scanning is useful for diagnosing deep or superficial venous thrombosis, for assessing venous incompetence, and for mapping the superficial veins before surgical harvesting for bypass operations. Because questions about the veins arise frequently in the treatment of cardiovascular patients, the cardiologist who is knowledgeable about veins and venous disease can play a central role in the diagnostic workup and treatment of these patients.     

三维步态分析对下肢生物力学变化的重测信度研究

目的:观察健康人在步行过程中下肢运动学、动力学、地面反作用力以及表面肌电信号的重测信度。方法:采用VICON (NEXUS 1.8.5)三维步态分析系统及NORAXON无线表面肌电图测试13名健康人步行过程中下肢运动学、动力学、地面反作用力以及表面肌电信号的重测信度。采用组内相关系数(ICC)及测量标准误(SEM)比较两次测试结果的相对信度与绝对信度。结果:步行过程中步速、下肢运动学、动力学、地面反作用力以及表面肌电信号均具有良好的重测信度ICC 0.78～0.96,运动学参数测量标准误SEM%为4.18～15.6,动力学参数SEM%为3.31～21.82,地面反作用力SEM%为1.70～16.67,表面肌电信号SEM%为8.00～11.11。结论:三维步态分析系统结合表面肌电图可用于评估步行时下肢运动学、动力学、地面反作用力以及表面肌电信号,且具有良好的重测信度。     

Lower extremity general muscle moment patterns in healthy individuals during recumbent cycling

OBJECTIVE: The purpose of this study was to compare lower extremity generalized muscle moments across two workloads during recumbent bicycling in younger and older healthy adults. DESIGN: The study design was a comparative investigation of cycling patterns. BACKGROUND: Biomechanical data regarding muscle activation, kinematic, and kinetic patterns have been presented for upright cycling, but only a few studies have evaluated biomechanical patterns during the alternative configuration of recumbent cycling. METHODS: Twenty-four healthy adults, classified by age into two different groups, under 35 and over 50 years of age, rode a recumbent bicycle at a constant cadence (60-65 rpm) and at two different resistances (0.5 and 1.0 kg m) while kinematic and kinetic data were recorded. General muscle moments were calculated using joint kinematic and kinetic data via inverse dynamic equations. RESULTS: The ankle general muscle moment remained plantar flexor throughout the pedaling cycle; the knee general muscle moment remained flexor throughout the cycle, except during the power phase of the higher workload where an extensor general muscle moment was observed; and the hip general muscle moment was extensor with a transient flexor general muscle moment period during the recovery phase. Increased workload led to increases in ankle plantar flexor and knee extensor general muscle moment magnitudes, but no changes at the hip. Age had no effect on general muscle moment magnitudes or patterns. CONCLUSIONS: Configurational differences between the upright and recumbent bicycle do not affect patterns, but the total output requirements do affect the magnitudes of the general muscle moments. RELEVANCE: Based on previous studies, the recumbent bicycle appears to be a safe rehabilitation tool for post-cerebrovascular accident and cardiorespiratory patients, but in order to more properly and efficiently use the recumbent bicycle as a rehabilitation tool, normative biomechanical data are necessary. The current study is the first such investigation to report normative data of lower extremity general muscle moment patterns during recumbent cycling. Effects of age and workload were also demonstrated.     

Effects of decision making on landing mechanics as a function of task and sex

Background

Factors that contribute to sex-differences in the incidence of anterior cruciate ligament injuries among athletes are not well understood. Of interest is whether decision making during landing influences biomechanical factors associated with anterior cruciate ligament injury. This study examined the effects of decision making on the mechanics of two-footed landing tasks in women and men.

Methods

Twenty-nine healthy young adults (13 women, 16 men) completed drop landings and drop-jumps under preplanned and decision-making conditions. Biomechanical data were collected and effects of decision making on lower extremity kinematics and kinetics were examined as a function of task and sex.

Findings

Landing mechanics were influenced by decision-making condition, task, and sex. During drop-jumps, participants exhibited lesser hip flexion (− 3.3°), lesser knee flexion (− 5.1°), and greater knee abduction (+ 1.0°) at initial contact under decision-making conditions. Under decision-making conditions, no differences were observed in these variables between tasks or with respect to preplanned drop landings. Across tasks and sexes, participants exhibited greater ankle plantarflexion at initial contact (+ 1.6°), greater peak knee external rotation (+ 1.5°), lesser peak knee internal rotation (− 1.0°), and smaller hip adduction moments (− 0.2% body weight × height) under decision-making conditions. Women but not men exhibited smaller ankle inversion moments (− 0.1% body weight × height) under decision-making conditions.

Interpretation

Modifications in landing mechanics suggest a default towards the preplanned drop landing strategy under decision-making conditions. Across sexes, drop landings and drop-jumps may be no more dangerous under decision-making conditions, with respect to anterior cruciate ligament loading, than preplanned drop landings.     

Resistance training is accompanied by increases in hip strength and changes in lower extremity biomechanics during running

Background

Movement and muscle activity of the hip have been shown to affect movement of the lower extremity, and been related to injury. The purpose of this study was to determine if increased hip strength affects lower extremity mechanics during running.

Methods

Within subject, repeated measures design. Fifteen healthy women volunteered. Hip abduction and external rotation strength were measured using a hand-held dynamometer. Three-dimensional biomechanical data of the lower extremity were collected during running using a high-speed motion capture system. Measurements were made before, at the mid-point, and after a 6-week strengthening program using closed-chain hip rotation exercises. Joint range of motion (rearfoot eversion, knee abduction, hip adduction, and internal rotation), eversion velocity, eversion angle at heel strike, and peak joint moments (rearfoot inversion, knee abduction, hip abduction, and external rotation) were analyzed using repeated measures analysis of variance (P ? 0.05). The independent variable was time (pre-, week 3, and week 6). A separate analysis of variance was conducted with the dependent variables of peak hip abduction and external rotation strength.

Findings

Hip abduction (P = 0.009) and external rotation strength (P < 0.0005) increased by 13% and 23%, respectively. Eversion range of motion decreased (P = 0.05), hip adduction range of motion increased (P = 0.05), and a trend of decreased hip internal rotation range of motion (P = 0.08) were found. Rearfoot inversion moment (P = 0.02) and knee abduction moment (P = 0.05) decreased by 57% and 10%, respectively.

Interpretation

The hip abductors and external rotators were strengthened, leading to an alteration of lower extremity joint loading which may reduce injury risk. These exercises could be used in the rehabilitation, or prevention, of lower extremity injuries.