Biomechanics of slow running and walking with a rocker shoe

Human-in-the-loop optimization of rocker shoes via different cost functions during walking

Personalised footwear could be used to enhance the function of the foot-ankle complex to a person's maximum. Human-in-the-loop optimization could be used as an effective and efficient way to find a personalised optimal rocker profile (i.e., apex position and angle). The outcome of this process likely depends on the selected optimization objective and its responsiveness to the rocker parameters being tuned. This study aims to explore whether and how human-in-the-loop optimization via different cost functions (i.e., metabolic cost, collision work as measure for external mechanical work, and step distance variability as measure for gait stability) affects the optimal apex position and angle of a rocker profile differently for individuals during walking. Ten healthy individuals walked on a treadmill with experimental rocker shoes in which apex position and angle were optimized using human-in-the-loop optimization using different cost functions. We compared the obtained optimal apex parameters for the different cost functions and how these affected the selected gait related objectives. Optimal apex parameters differed substantially between participants and optimal apex positions differed between cost functions. The responsiveness to changes in apex parameters differed between cost functions. Collision work was the only cost function that resulted in a significant improvement of its performance criteria. Improvements in metabolic cost or step distance variability were not found after optimization. This study showed that cost function selection is important when human-in-the-loop optimization is used to design personalised footwear to allow conversion to an optimum that suits the individual.

The rocker-soled shoes change the kinematics and muscle contractions of the lower extremity during various functional movement

While rocker-shaped soles have become popular for running shoes, whether or not this type of shoe benefits other functional movements has rarely been discussed. The purpose of this study was to investigate the effect of rocker-soled shoes on lower extremity biomechanics during different exercises. Seventeen healthy university students were recruited. A motion capture analysis system and surface electromyography were used to measure kinematics and muscle activation while walking (10 m), running (10 m), cutting, jumping, and ascending and descending stairs. The results showed that when wearing rocker-soled shoes, greater peak external ankle rotation was present during most exercises. Smaller peak joint angles were observed in hip extension and external rotation when walking, and in ankle dorsiflexion when ascending stairs and jumping. The vastus medialis and vastus lateralis contracted more in most exercises when rocker-soled shoes were worn. However, the biceps femoris and medial gastrocnemius showed less muscle contraction. Wearing rocker-soled shoes during testing movements change the kinematics and muscle contractions of the lower extremity. These findings may provide information for choosing shoes for different exercises or training purposes.

Lower Limb Kinematic Coordination during the Running Motion of Stroke Patient: A Single Case Study

The purpose of this study was to clarify the lower limb joint motor coordination of para-athletes during running motion from frequency characteristics and to propose this as a method for evaluating their performance. The subject used was a 43-year-old male para-athlete who had suffered a left cerebral infarction. Using a three-dimensional motion analysis system, the angles of the hip, knee, and ankle joints were measured during 1 min of running at a speed of 8 km/h on a treadmill. Nine inter- and intra-limb joint angle pairs were analyzed by coherence and phase analyses. The main characteristic of the stroke patient was that there were joint pairs with absent or increased coherence peaks in the high-frequency band above 4 Hz that were not found in healthy subjects. Interestingly, these features were also observed on the non-paralyzed side. Furthermore, a phase analysis showed different phase differences between the joint motions of the stroke patient and healthy subjects in some joint pairs. Thus, we concluded there was a widespread functional impairment of joint motion in the stroke patient that has not been revealed by conventional methods. The coherence analysis of joint motion may be useful for identifying joint motion problems in para-athletes.

Ground Reaction Force Differences between Bionic Shoes and Neutral Running Shoes in Recreational Male Runners before and after a 5 km Run

Running-related injuries are common among runners. Recent studies in footwear have shown that designs of shoes can potentially affect sports performance and risk of injury. Bionic shoes combine the functions of barefoot running and foot protection and incorporate traditional unstable structures based on bionic science. The purpose of this study was to investigate ground reaction force (GRF) differences for a 5 km run and how bionic shoes affect GRFs. Sixteen male recreational runners volunteered to participate in this study and finished two 5 km running sessions (a neutral shoe session and a bionic shoe session). Two-way repeated-measures ANOVAs were performed to determine the differences in GRFs. In the analysis of the footwear conditions of runners, bionic shoes showed significant decreases in vertical impulse, peak propulsive force, propulsive impulse, and contact time, while the braking impulse and vertical instantaneous loading rate (VILR) increased significantly compared to the neutral shoes. Main effects for a 5 km run were also observed at vertical GRFs and anterior–posterior GRFs. The increases of peak vertical impact force, vertical average loading rate (VALR), VILR, peak braking force and braking impulse were observed in post-5 km running trials and a reduction in peak propulsive force and propulsive impulse. The interaction effects existed in VILR and contact time. The results suggest that bionic shoes may benefit runners with decreasing injury risk during running. The findings of the present study may help to understand the effects of footwear design during prolonged running, thereby providing valuable information for reducing the risk of running injuries.

Prolonged Running Using Bionic Footwear Influences Lower Limb Biomechanics

The running biomechanics of unstable shoes have been well investigated, however, little is known about how traditional neutral shoes in combination with unstable design elements and scientifically (bionic) designed shoes influence prolonged running biomechanics. The purpose of this study was to investigate biomechanical changes for a typical 5 km run and how footwear technology may affect outcomes. Sixteen healthy male recreational heel strike runners participated in this study, and completed two prolonged running sessions (neutral shoe session and bionic shoe session), with 7 to 10 days interval between sessions. A two-way repeated-measures analysis of variance (ANOVA, shoe × time) was conducted to determine any differences in joint biomechanics. Main effects for shoe type were observed at the ankle, knee and hip joints during the stance phase. In particular, decreased range of motion (ROM) was observed using the bionic shoes for all three joints, and the joint moments also had significant changes except for the frontal plane of the hip. Main effects for time were also observed at the ankle, knee and hip joints. The ROM of the sagittal plane in the knee and hip decreased post-5 km running. The reduction of ankle dorsiflexion, hip flexion, hip adduction and hip internal rotation angles were observed post-5 km running, as well as the increase of ankle eversion and external rotation, knee adduction and internal rotation angles. The kinetics also exhibited significant differences between pre-5 km running and post-5 km running. The interaction effects only existed in the ROM of the hip sagittal plane, hip adduction angle and hip internal rotation angle. The results suggested that bionic shoes could be beneficial for strengthening muscle control, enhancing postural stability and proprioceptive ability. Footwear personalization could be a solution that benefits runners, reduces injury risk and improves running performance.

Core Strength Training Can Alter Neuromuscular and Biomechanical Risk Factors for Anterior Cruciate Ligament Injury

BACKGROUND

Core stability is influential in the incidence of lower extremity injuries, including anterior cruciate ligament (ACL) injuries, but the effects of core strength training on the risk for ACL injury remain unclear.

HYPOTHESIS

Core muscle strength training increases the knee flexion angle, hamstring to quadriceps (H:Q) coactivation ratio, and vastus medialis to vastus lateralis (VM:VL) muscle activation ratio, as well as decreases the hip adduction, knee valgus, and tibial internal rotation angles.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 48 male participants were recruited and randomly assigned to either the intervention group (n = 32) or the control group (n = 16). Three-dimensional trunk, hip, knee, and ankle kinematic data and muscle activations of selected trunk and lower extremity muscles were obtained while the participants performed side-step cutting. The core endurance scores were measured before and after training. Two-way analyses of variance were conducted for each dependent variable to determine the effects of 10 weeks of core strength training.

RESULTS

The trunk endurance scores in the intervention group significantly increased after training (P < .05 for all comparisons). The intervention group showed decreased knee valgus (P = .038) and hip adduction angles (P = .032) but increased trunk flexion angle (P = .018), rectus abdominis to erector spinae coactivation ratio (P = .047), H:Q coactivation ratio (P = .021), and VM:VL activation ratio (P = .016). In addition, the knee valgus angle at initial contact was negatively correlated with the VM:VL activation ratio in the precontact phase (R² = 0.188; P < .001) but was positively correlated with the hip adduction angle (R² = 0.120; P < .005). No statistically significant differences were observed in the trunk endurance scores, kinematics, and muscle activations for the control group.

CONCLUSION

Core strength training altered the motor control strategies and joint kinematics for the trunk and the lower extremity by increasing the trunk flexion angle, VM:VL activation ratio, and H:Q activation ratio and reducing the knee valgus and hip adduction angles.

CLINICAL RELEVANCE

Training core muscles can modify the biomechanics associated with ACL injuries in a side-step cutting task; thus, core strength training might be considered in ACL injury prevention programs to alter the lower extremity alignment in the frontal plane and muscle activations during sports-related tasks.

Knee Joint Biomechanics in Physiological Conditions and How Pathologies Can Affect It: A Systematic Review

The knee joint, as the main lower limb motor joint, is the most vulnerable and susceptible joint. The knee injuries considerably impact the normal living ability and mental health of patients. Understanding the biomechanics of a normal and diseased knee joint is in urgent need for designing knee assistive devices and optimizing a rehabilitation exercise program. In this paper, we systematically searched electronic databases (from 2000 to November 2019) including ScienceDirect, Web of Science, PubMed, Google Scholar, and IEEE/IET Electronic Library for potentially relevant articles. After duplicates were removed and inclusion criteria applied to the titles, abstracts, and full text, 138 articles remained for review. The selected articles were divided into two groups to be analyzed. Firstly, the real movement of a normal knee joint and the normal knee biomechanics of four kinds of daily motions in the sagittal and coronal planes, which include normal walking, running, stair climbing, and sit-to-stand, were discussed and analyzed. Secondly, an overview of the current knowledge on the movement biomechanical effects of common knee musculoskeletal disorders and knee neurological disorders were provided. Finally, a discussion of the existing problems in the current studies and some recommendation for future research were presented. In general, this review reveals that there is no clear assessment about the biomechanics of normal and diseased knee joints at the current state of the art. The biomechanics properties could be significantly affected by knee musculoskeletal or neurological disorders. Deeper understanding of the biomechanics of the normal and diseased knee joint will still be an urgent need in the future.

Kinematics and muscle activity when running in partial minimalist, traditional, and maximalist shoes

While several studies have examined kinematic and kinetic differences between maximalist (MAX), traditional (TRAD), or partial minimalist (PMIN) shoes, to date it is unknown how MAX shoes influence muscle activity. This study compared lower extremity kinematics and muscle activity when running in PMIN, TRAD, and MAX shoes. Thirteen participants ran in each shoe while whole body kinematics were recorded using motion capture and electromyography was recorded from seven leg muscles. Differences in kinematics and root mean square amplitudes (RMS) were compared between shoe conditions. There were small differences in sagittal and frontal plane ankle kinematics between shoe conditions, with the MAX shoes resulting in less dorsiflexion at foot strike (p = .002) and less peak dorsiflexion (p < .001), and the PMIN shoes resulting in greater peak eversion (p = .012). Gluteus medius (p.006) and peroneus longus (p = .007) RMS amplitudes were greater in the MAX shoe then the TRAD or PMIN shoes while tibialis anterior RMS amplitudes were higher in the PMIN shoes (p = .005) than either the TRAD or MAX shoes. Consistent with previous findings, these results suggest there are small differences in kinematics when running in these three shoe types. This may partly be explained by the changes in muscle activity, which may be a response in order to maintain a preferred or habitual movement path. Implications for these difference in muscle activity in terms of fatigue or injury remain to be determined.

A systematic review of the effect of footwear, foot orthoses and taping on lower limb muscle activity during walking and running

BACKGROUND

External devices are used to manage musculoskeletal pathologies by altering loading of the foot, which could result in altered muscle activity that could have therapeutic benefits.

OBJECTIVES

To establish if evidence exists that footwear, foot orthoses and taping alter lower limb muscle activity during walking and running.

STUDY DESIGN

Systematic literature review.

METHODS

CINAHL, MEDLINE, ScienceDirect, SPORTDiscus and Web of Science databases were searched. Quality assessment was performed using guidelines for assessing healthcare interventions and electromyography methodology.

RESULTS

Thirty-one studies were included: 22 related to footwear, eight foot orthoses and one taping. In walking, (1) rocker footwear apparently decreases tibialis anterior activity and increases triceps surae activity, (2) orthoses could decrease activity of tibialis posterior and increase activity of peroneus longus and (3) other footwear and taping effects are unclear.

CONCLUSION

Modifications in shoe or orthosis design in the sagittal or frontal plane can alter activation in walking of muscles acting primarily in these planes. Adequately powered research with kinematic and kinetic data is needed to explain the presence/absence of changes in muscle activation with external devices.

CLINICAL RELEVANCE

This review provides some evidence that foot orthoses can reduce tibialis posterior activity, potentially benefitting specific musculoskeletal pathologies.

Biomechanical effects of rocker shoes on plantar aponeurosis strain in patients with plantar fasciitis and healthy controls

Plantar fasciitis is a frequently occurring overuse injury of the foot. Shoes with a stiff rocker profile are a commonly prescribed treatment modality used to alleviate complaints associated with plantar fasciitis. In rocker shoes the apex position was moved proximally as compared to normal shoes, limiting the progression of the ground reaction forces (GRF) and peak plantarflexion moments during gait. A stiff sole minimizes dorsiflexion of the toes. The aim of this study was to investigate whether the biomechanical effects of rocker shoes lead to minimization of plantar aponeurosis (PA) strain during gait in patients with plantar fasciitis and in healthy young adults. 8 patients with plantar fasciitis (1 male, 7 females; mean age 55.0 ± 8.4 years) and 8 healthy young adults (8 females; mean age 24.1 ± 1.6 years) participated in the study. Each participant walked for 1 minute on an instrumented treadmill while wearing consecutively in random order shoes with a normal apex position (61.2 ± 2.8% apex) with flexible insole (FN), normal apex position with stiff insole (SN), proximal apex position (56.1 ± 2.6% apex) with flexible insole (FR) and proximal apex position with stiff insole (SR). Marker position data of the foot and lower leg and GRF were recorded. An OpenSim foot model was used to compute the change in PA length based on changes in foot segment positions during gait. The changes in PA length due to increases in Achilles tendon forces were computed based on previous data of a cadaver study. PA strain computed from both methods was not statistically different between shoe conditions. Peak Achilles tendon force, peak first metatarsophalangeal (MTP1) joint angle and peak plantarflexion moment were significantly lower when walking with the rocker shoe with a proximal apex position and a stiff insole for all subjects (p<.05). Changes in Achilles tendon forces during gait accounted for 65 ± 2% of the total PA strain. Rocker shoes with a stiff insole reduce peak dorsiflexion angles of the toes and plantar flexion moments, but not PA strain because the effects of a proximal apex position and stiff insole do not occur at the same time, but independently affect PA strain at 80-90% and 90-100% of the stance phase. Rocker shoes with an apex position of ~56% are insufficient to significantly reduce peak PA strain values in patients with plantar fasciitis and healthy young adults.

Tibiofemoral Cartilage Contact Differences Between Level Walking and Downhill Running

Background:

Some studies have suggested that altered tibiofemoral cartilage contact behavior (arthrokinematics) may contribute to long-term cartilage degeneration, potentially leading to tibiofemoral osteoarthritis. However, few studies have assessed normal tibiofemoral arthrokinematics during dynamic activities.

Purpose:

To characterize tibiofemoral arthrokinematics during the impact phase of level walking and downhill running.

Study Design:

Descriptive laboratory study.

Methods:

Arthrokinematic data were collected on uninjured knees of 44 participants (mean age, 20.7 ± 6.6 years). Using a dynamic stereoradiographic imaging system with superimposed 3-dimensional bone models from computed tomography and magnetic resonance imaging of participant-specific tibiofemoral joints, arthrokinematics were assessed during the first 15% of the gait cycle during level walking and the first 10% of the gait cycle during downhill running.

Results:

During level walking and downhill running, the medial compartment had a greater cartilage contact area versus the lateral compartment. Both compartments had a significantly less cartilage contact area during running versus walking (medial compartment gait cycle affected: 8%-10%; lateral compartment gait cycle affected: 5%-10%). Further, medial and lateral compartment tibiofemoral contact paths were significantly more posterior and longer during downhill running.

Conclusion:

There was a decreased tibiofemoral cartilage contact area during downhill running compared with level walking, suggesting that underlying bone morphology may play a key role in determining the size of cartilage contact regions.

Clinical Relevance:

This study provides the first data characterizing tibiofemoral cartilage contact patterns during level walking and downhill running. These results provide evidence in support of performing biomechanical assessments during both level walking and downhill running to obtain a comprehensive picture of tibiofemoral cartilage behavior after clinical interventions.

A 6-Week Transition to Maximal Running Shoes Does Not Change Running Biomechanics

BACKGROUND

A recent study suggested that maximal running shoes may increase the impact force and loading rate of the vertical ground-reaction force during running. It is currently unknown whether runners will adapt to decrease the impact force and loading rate over time.

PURPOSE

To compare the vertical ground-reaction force and ankle kinematics between maximal and traditional shoes before and after a 6-week acclimation period to the maximal shoe.

STUDY DESIGN

Controlled laboratory study.

METHODS

Participants ran in a traditional running shoe and a maximal running shoe during 2 testing sessions 6 weeks apart. During each session, 3-dimensional kinematics and kinetics were collected during overground running. Variables of interest included the loading rate, impact peak, and active peak of the vertical ground-reaction force, as well as eversion and dorsiflexion kinematics. Two-way repeated measures analyses of variance compared data within participants.

RESULTS

No significant differences were observed in any biomechanical variable between time points. The loading rate and impact peak were higher in the maximal shoe. Runners were still everted at toe-off and landed with less dorsiflexion, on average, in the maximal shoe.

CONCLUSION

Greater loading rates and impact forces were previously found in maximal running shoes, which may indicate an increased risk of injury. The eversion mechanics observed in the maximal shoes may also increase the risk of injury. A 6-week transition to maximal shoes did not significantly change any of these measures.

CLINICAL RELEVANCE

Maximal running shoes are becoming very popular and may be considered a treatment option for some injuries. The biomechanical results of this study do not support the use of maximal running shoes. However, the effect of these shoes on pain and injury rates is unknown.

Effects of Different Hardness in Bionic Soles on Lower Limb Biomechanics

The design of modern footwear seems to have an excessive protective effect on the function of the foot. The purpose of this study was to examine how bionic shoes designed would influence the biomechanical index of gait patterns. There were 10 male subjects underwent gait analysis. Normal sports shoes (NS) with flat-soles were selected as control shoes. The experimental shoes comprising of two elasticity levels were defined as soft-sole bionic shoes (SS) and hard-sole bionic shoes (HS). We examined ground reaction forces, plantar pressures and angles of the ankle, knee and hip during walking and jogging conditions. In comparison with standard shoes, wearing bionic shoes reduced the range of motion in some joints during movement and changed the peak angle in the sagittal, frontal and horizontal planes. Moreover, the vertical average loading rates were significantly larger than that of the standard shoes during jogging. The experimental groups showed larger PP or PTI in the foot regions examined except in the lateral forefoot. Also, increases the in the contact area of the midfoot with decreases in the contact area in heel were also observed. In some regions of the foot, the hard sole of the bionic shoes had a lower pressure than that of the soft sole. These findings indicate that the design of the bionic sole in this study can be used to increase toe scratching ability, increase neuromuscular strength and enhance stability and proprioceptive ability. However, the higher plantar pressures in some regions may increase the risk of overuse injuries. The findings from the study indicate preference for the hard bionic shoes during exercise compared to the soft sole.

Effect of rocker shoes and running speed on lower limb mechanics and soft tissue vibrations

Previous studies have shown a possible effect of running speed and the sole material of footwear on lower-limb mechanics and soft tissue vibrations, while little information has been offered concerning the influence of the shape of the footwear's sole. The purpose of this study is to assess the effect of running speed and rocker shoes on muscular activity, ground reaction force, and soft tissue vibrations. Twenty participants performed heel-toe running with two shoes, differentiated only by their sole shape (i.e. rocker and non-rocker), at four running speeds. Ground reaction force and electromyograms of the gastrocnemius medialis and vastus lateralis were measured, and soft tissue accelerations of the same muscles were recorded with tri-axial accelerometers. A continuous wavelet transform was applied to the accelerometer's signals to analyse them in the time-frequency domain. The rocker of the shoes did not change the muscular activations, ground reaction force, nor power of soft tissue vibrations. In opposite, increased running speed led to an augmentation of all of the measured parameters. Interestingly, running speed augmentation led to a greater increase in high frequencies component of soft tissue vibrations (25-50 Hz, 242%) than lower ones (8-25 Hz, 111%). Consequently, we indicated a 10% increase in the relative part of the high frequencies of the total power. In conclusion, although rocker shoes have shown an effect on lower-limb kinetics in some studies, no influence on soft tissue vibration is denoted. By contrast, soft tissue vibrations may be modulated by changing running speed.

Stiffness Effects in Rocker-Soled Shoes: Biomechanical Implications

Rocker-soled shoes provide a way to reduce the possible concentration of stress, as well as change movement patterns, during gait. This study attempts to examine how plantar force and spatio-temporal variables are affected by two rocker designs, one with softer and one with denser sole materials, by comparing them with the barefoot condition and with flat-soled shoes. Eleven subjects' gait parameters during walking and jogging were recorded. Our results showed that compared with barefoot walking, plantar forces were higher for flat shoes while lower for both types of rocker shoes, the softer-material rocker being the lowest. The plantar force of flat shoes is greater than the vertical ground reaction force, while that of both rocker shoes is much less, 13.87-30.55% body weight. However, as locomotion speed increased to jogging, for all shoe types, except at the second peak plantar force of the denser sole material rocker shoes, plantar forces were greater than for bare feet. More interestingly, because the transmission of force was faster while jogging, greater plantar force was seen in the rocker-soled shoes with softer material than with denser material; results for higher-speed shock absorption in rocker-soled shoes with softer material were thus not as good. In general, the rolling phenomena along the bottom surface of the rocker shoes, as well as an increase in the duration of simultaneous curve rolling and ankle rotation, could contribute to the reduction of plantar force for both rocker designs. The possible mechanism is the conversion of vertical kinetic energy into rotational kinetic energy. To conclude, since plantar force is related to foot-ground interface and deceleration methods, rocker-design shoes could achieve desired plantar force reduction through certain rolling phenomena, shoe-sole stiffness levels, and locomotion speeds.

The effect of different shoes on functional mobility and energy expenditure in post-stroke hemiplegic patients using ankle-foot orthosis

BACKGROUND

Ankle-foot orthoses could be utilized both with and without shoes. While several studies have shown that ankle-foot orthoses improve gait abilities in hemiplegic patients, it remains unclear whether they should be used with shoes or without.

OBJECTIVES

The study purpose was to compare the effect of standard shoes and rocker shoes on functional mobility in post-stroke hemiplegic patients utilizing ankle-foot orthosis.

STUDY DESIGN

Randomized clinical study.

METHODS

Thirty post-stroke hemiplegic patients participated in this study randomly assigned to two groups. Group I received standard shoes + ankle-foot orthosis and group II were provided with rocker shoes + ankle-foot orthosis. Their functional mobility and energy expenditure parameters including timed up and go, timed up stairs, timed down stairs, preferred walking speed, and oxygen (O2) cost (mL/kg/m) were measured.

RESULTS

In group I, no significant changes were seen in outcome measures after wearing standard shoes. While in group II, O2 cost and timed up and go time significantly decreased, and preferred walking speed increased when patients wore rocker shoes. Also, there was a significant difference between rocker shoes and standard shoes in improvement of timed up and go, preferred walking speed, and O2 cost.

CONCLUSION

When patients using ankle-foot orthosis wore rocker shoes, their functional mobility improved and oxygen cost diminished. Also, rocker shoes was significantly more effective than standard shoes in improving functional mobility parameters.

CLINICAL RELEVANCE

This study suggests that in post-stroke hemiplegic patients using ankle-foot orthosis, wearing rocker shoes can lead to much more improved functional mobility and decreased energy expenditure compared to ankle-foot orthosis only. Thus, in stroke patients, the combination of ankle-foot orthosis-rocker shoes is recommended for both rehabilitation programs and ankle-foot orthosis efficacy investigations.

Lower limb joint stiffness and muscle co-contraction adaptations to instability footwear during locomotion

Unstable shoes (US) continually perturb gait which can train the lower limb musculature, but muscle co-contraction and potential joint stiffness strategies are not well understood. A shoe with a randomly perturbing midsole (IM) may enhance these adaptations. This study compares ankle and knee joint stiffness, and ankle muscle co-contraction during walking and running in US, IM and a control shoe in 18 healthy females. Ground reaction forces, three-dimensional kinematics and electromyography of the gastrocnemius medialis and tibialis anterior were recorded. Stiffness was calculated during loading and propulsion, derived from the sagittal joint angle-moment curves. Ankle co-contraction was analysed during pre-activation and stiffness phases. Ankle stiffness reduced and knee stiffness increased during loading in IM and US whilst walking (ankle, knee: p=0.008, 0.005) and running (p<0.001; p=0.002). During propulsion, the opposite joint stiffness re-organisation was found in IM whilst walking (both joints p<0.001). Ankle co-contraction increased in IM during pre-activation (walking: p=0.001; running: p<0.001), and loading whilst walking (p=0.003), not relating to ankle stiffness. Results identified relative levels of joint stiffness change in unstable shoes, providing new evidence of how stability is maintained at the joint level.

A Randomized Comparison of the Biomechanical Effect of Two Commercially Available Rocker Bottom Shoes to a Conventional Athletic Shoe During Walking in Healthy Individuals

Rocker bottom shoes have recently gained considerable popularity, likely in part because of the many purported benefits, including reducing joint loading and toning muscles. Scientific inquiry about these benefits has not kept pace with the increased usage of this shoe type. A fundamental premise of rocker bottom shoes is that they transform hard, flat, level surfaces into more uneven ones. Published studies have described a variety of such shoes-all having a somewhat rounded bottom and a cut heel region or a cut forefoot region, or both (double rocker). Despite the fundamentally similar shoe geometries, the reported effects of rocker bottom shoes on gait biomechanics have varied considerably. Ten healthy subjects agreed to participate in the present study and were given appropriately sized Masai Barefoot Technology (St. Louis, MO), Skechers(™) (Manhattan Beach, CA), and New Balance (Boston, MA) conventional walking shoes. After a 12-day accommodation period, the subjects walked wearing each shoe while 3-dimensional motion and force data were collected in the gait laboratory. The key findings included (1) increased trunk flexion, decreased ankle plantarflexion range, and reduced plantarflexion moment in the early stance; (2) increased ankle dorsiflexion and knee flexor moment in the midstance; (3) decreased peak ankle plantarflexion in the late stance; and (4) decreased ankle plantarflexion and decreased hip flexor and knee extensor moments in the pre-swing and into swing phase. The walking speed was unconstrained and was maintained across all shoe types. A biomechanical explanation is suggested for the observed changes. Suggestions for cautions are provided for using rocker bottom shoes in patients with neuromuscular insufficiency.

Influence of unstable footwear on lower leg muscle activity, volume change and subjective discomfort during prolonged standing

PURPOSE

The present study was an attempt to investigate the effect of unstable footwear on lower leg muscle activity, volume change and subjective discomfort during prolonged standing.

METHODS

Ten healthy subjects were recruited to stand for 2 h in three footwear conditions: barefoot, flat-bottomed shoe and unstable shoe. During standing, lower leg discomfort and EMG activity of medial gastrocnemius (MG) and tibialis anterior (TA) muscles were continuously monitored. Changes in lower leg volume over standing time also were measured.

RESULTS

Lower leg discomfort rating reduced significantly while subjects standing on unstable shoe compared to the flat-bottomed shoe and barefoot condition. For lower leg volume, less changes also were observed with unstable shoe. The activity level and variation of right MG muscle was greater with unstable shoe compared to the other footwear conditions; however regarding the left MG muscle, significant difference was found between unstable shoe and flat-bottomed shoe only for activity level. Furthermore no significant differences were observed for the activity level and variation of TA muscles (right/left) among all footwear conditions.

CONCLUSIONS

The findings suggested that prolonged standing with unstable footwear produces changes in lower leg muscles activity and leads to less volume changes. Perceived discomfort also was lower for this type of footwear and this might mean that unstable footwear can be used as ergonomic solution for employees whose work requires prolonged standing.

Risk Factors and Protective Factors for Lower-Extremity Running Injuries A Systematic Review

A review of the scientific literature was performed 1) to identify studies describing the most common running injuries and their relation to the risk factors that produce them and 2) to search for potential and specific protective factors. Spanish and English biomedical search engines and databases (MEDLINE/PubMed, Database Enfermería Fisioterapia Podología [ENFISPO], Cochrane Library, and Cumulative Index to Nursing and Allied Health Literature) were queried (February 1 to November 30, 2013). A critical reading and assessment was then performed by the Critical Appraisal Skills Programme Spanish tool. In total, 276 abstracts that contained the selected key words were found. Of those, 25 identified and analyzed articles were included in the results. Injuries result from inadequate interaction between the runner's biomechanics and external factors. This leads to an excessive accumulation of impact peak forces in certain structures that tends to cause overuse injuries. The main reasons are inadequate muscle stabilization and pronation. These vary depending on the runner's foot strike pattern, foot arch morphology, and sex. Specific measures of modification and control through running footwear are proposed.

Effects of forefoot bending elasticity of running shoes on gait and running performance

The aim of this study was to investigate the effects of forefoot bending elasticity of running shoes on kinetics and kinematics during walking and running. Twelve healthy male participants wore normal and elastic shoes while walking at 1.5m/s, jogging at 2.5m/s, and running at 3.5m/s. The elastic shoes were designed by modifying the stiffness of flexible shoes with elastic bands added to the forefoot part of the shoe sole. A Kistler force platform and Vicon system were used to collect kinetic and kinematic data during push-off. Electromyography was used to record the muscle activity of the medial gastrocnemius and medial tibialis anterior. A paired dependent t-test was used to compare the various shoes and the level of significance was set at α=.05. The range of motion of the ankle joint and the maximal anterior-posterior propulsive force differed significantly between elastic and flexible shoes in walking and jogging. The contact time and medial gastrocnemius muscle activation in the push-off phase were significantly lower for the elastic shoes compared with the flexible shoes in walking and jogging. The elastic forefoot region of shoes can alter movement characteristics in walking and jogging. However, for running, the elasticity used in this study was not strong enough to exert a similar effect.

Effect of rocker shoes on plantar pressure pattern in healthy female runners

Rocker profile shoes (rocker shoes) are one of the treatment options of metatarsalgia and forefoot stress fractures. The efficacy of rocker shoes in unloading the forefoot pressure has been shown in walking. In running, however, the effect of rocker shoes on forefoot pressure is unknown. Eighteen healthy female runners participated in this study. In-shoe plantar pressures were recorded during running with the standard running shoes and rocker shoes. Shoe comfort was assessed after each shoe measurement. Peak pressure (PP), maximum mean pressure (MMP) and force-time integral (FTI) were determined for seven foot areas. The effects of shoes on the different outcome variables were statistically analyzed using a linear mixed model. Running with the rocker shoes caused a significant reduction (p<0.001) in all pressure parameters in the central and lateral forefoot. FTI and MMP were also reduced by 11% and 12% in the medial forefoot while running with rocker shoes. Running with rocker shoes resulted in a significant increase in all pressure parameters at the heel region (p<0.001). Running with rocker shoes received a significant (p<0.01) lower comfort rate than running with standard running shoes. Rocker shoes might be beneficial for runners who are recovering from metatarsalgia or stress fractures of the forefoot region, as it reduces plantar pressure in the forefoot region.