Investigating the effect of custom‐made insoles and exercises on lower limb and back discomfort in assembly‐line workers in a rubber tire factory: A randomized controlled trial

Many occupations require standing for prolonged periods, which can be a major contributor to musculoskeletal problems and cause disturbances in different parts of the body, especially the lower back and lower extremities. The aim of this study was to investigate the effect of custom‐made insoles and exercise training on the lower limb and lower back discomfort in workers on a production line at a rubber tire factory. One hundred male workers (mean age 35.96 years, work experience of 10.62 years, standing time 6.58 hr) participated in this randomized controlled trial. The men were randomly assigned to one of four groups: (a) custom‐made insole plus lower limb exercises, (b) insoles only, (c) lower limb exercises only, and (d) no intervention. Discomfort level was recorded with a visual analog scale and a body map. The data were analyzed with analysis of covariance. The results showed a significant difference in discomfort levels between groups in the lower back (p = .001), thigh (p = .001), and knee (p = .001) areas. The combined insole and exercise group had less discomfort in the lower back, thigh, and knee. In the group that used the insole only without exercises, the discomfort level in the lower back area was reduced. The results indicate that the simultaneous use of insoles and exercises might be an effective intervention to reduce discomfort in the lower limbs and lower back in workers who remain standing for prolonged periods.     

The effects of military body armour on the lower back and knee mechanics during toe-touch and two-legged squat tasks

While effective in the prevention of otherwise lethal injuries, military body armour (BA) has been suggested to reduce warfighter's performance and increase injury-related musculoskeletal conditions. Providing the significant role of joint biomechanics in both performance and risk of injury, the immediate and prolonged effects of wearing BA on biomechanics of the lower back and knee during toe-touch (TT) and two-legged squat (TLS) tasks were investigated. The immediate effects of BA were an increase of >40 ms (p ≤ 0.02) in flexion duration of the dominant joint and an ～1 s (p ≤ 0.02) increase in overall task duration as well as an ～18% (p = 0.03) decrease in the lumbopelvic rhythm ratio near the mid-range of trunk flexion. In general the prolonged duration of wearing BA (i.e. 45 min of walking) was not found to cause more changes in our measures than walking without BA.     

Effects of shoe inserts and heel height on foot pressure, impact force, and perceived comfort during walking

Studying the impact of high-heeled shoes on kinetic changes and perceived discomfort provides a basis to advance the design and minimize the adverse effects on the human musculoskeletal system. Previous studies demonstrated the effects of inserts on kinetics and perceived comfort in flat or running shoes. No study attempted to investigate the effectiveness of inserts in high heel shoes. The purpose of this study was to determine whether increasing heel height and the use of shoe inserts change foot pressure distribution, impact force, and perceived comfort during walking. Ten healthy females volunteered for the study. The heel heights were 1.0cm (flat), 5.1cm (low), and 7.6cm (high). The heel height effects were examined across five shoe-insert conditions of shoe only; heel cup, arch support, metatarsal pad, and total contact insert (TCI). The results indicated that increasing heel height increases impact force (p<0.01), medial forefoot pressure (p<0.01), and perceived discomfort (p<0.01) during walking. A heel cup insert for high-heeled shoes effectively reduced the heel pressure and impact force (p<0.01), an arch support insert reduced the medial forefoot pressure, and both improved footwear comfort (p<0.01). In particular, a TCI reduced heel pressure by 25% and medial forefoot pressure by 24%, attenuate the impact force by 33.2%, and offered higher perceived comfort when compared to the non-insert condition.     

Use of pressure insoles to compare in-shoe loading for modern running shoes

The primary objective of this paper was to compare in-shoe loading for different models of running shoe using measurements of force distribution. It was hypothesised that a shoe designed with minimal focus on cushioning would demonstrate significantly higher peak forces and rates of loading than running shoes designed with cushioning midsoles. Loading was compared using in-shoe peak forces for six footwear conditions. It was found that peak rate of loading at the heel provided clear distinctions between shoes. In support of the study hypothesis, the shoe with minimal focus on cushioning had a significantly higher rate of loading than all but one of the other test shoes. Data collected for midfoot and forefoot areas of the foot highlighted the importance of considering loading across the foot surface. The results of the present study demonstrate that pressure insoles provide a useful tool for the assessment of loading across the foot plantar surface for different footwear conditions. There are numerous models of running shoe for individuals to select from, with limited information available regarding the performance of the shoes during running. The current study demonstrates differences in loads across the foot plantar surface during running, indicating differences in performance for different footwear models.     

Use of pressure insoles to compare in-shoe loading for modern running shoes

The primary objective of this paper was to compare in-shoe loading for different models of running shoe using measurements of force distribution. It was hypothesised that a shoe designed with minimal focus on cushioning would demonstrate significantly higher peak forces and rates of loading than running shoes designed with cushioning midsoles. Loading was compared using in-shoe peak forces for six footwear conditions. It was found that peak rate of loading at the heel provided clear distinctions between shoes. In support of the study hypothesis, the shoe with minimal focus on cushioning had a significantly higher rate of loading than all but one of the other test shoes. Data collected for midfoot and forefoot areas of the foot highlighted the importance of considering loading across the foot surface. The results of the present study demonstrate that pressure insoles provide a useful tool for the assessment of loading across the foot plantar surface for different footwear conditions. There are numerous models of running shoe for individuals to select from, with limited information available regarding the performance of the shoes during running. The current study demonstrates differences in loads across the foot plantar surface during running, indicating differences in performance for different footwear models.     

The reliability of the Extra Load Index as a measure of relative load carriage economy

Abstract

The aim of this study was to measure the reliability of the extra load index (ELI) as a method for assessing relative load carriage economy. Seventeen volunteers (12 males, 5 females) performed walking trials at 3 km·h^?1, 6 km·h^?1 and a self-selected speed. Trial conditions were repeated 7 days later to assess test–retest reliability. Trials involved four 4-minute periods of walking, each separated by 5 min of rest. The initial stage was performed unloaded followed in a randomised order by a second unloaded period and walking with backpacks of 7 and 20 kg. Results show ELI values did not differ significantly between trials for any of the speeds (p = 0.46) with either of the additional loads (p = 0.297). The systematic bias, limits of agreement and coefficients of variation were small in all trial conditions. We conclude the ELI appears to be a reliable measure of relative load carriage economy.

Practitioner Summary: This paper demonstrates that the ELI is a reliable measure of load carriage economy at a range of walking speeds with both a light and heavy load. The ELI, therefore, represents a useful tool for comparing the relative economy associated with different load carriage systems.     

Subjective evaluation of running footwear depends on country and assessment method: a bi-national study

This study examined (1) the perception of running shoes between China (Beijing) and Singapore and (2) whether running shoe preference depended on assessment methods. One hundred (n = 50 each country) Chinese males subjectively evaluated four shoe models during running by using two assessment procedures. Procedure 1 used a visual analogue scale (VAS) to assess five perception variables. Procedure 2 was a ‘head-to-head’ comparison of two shoes simultaneously (e.g. left foot: A and right foot: B) to decide which model was preferred. VAS scores were consistently higher in Beijing participants (p < .001), indicating a higher degree of liking. Singapore participants used the lower end but a wider range of the 15 cm scale for shoe discrimination. Moderate agreement was seen between the VAS and ‘head-to-head’ procedures, with only 14 out of 100 participants matched all 6 pairwise comparisons (median = 4 matches). Footwear companies and researchers should be aware that subjective shoe preference may vary with assessment methods.

Practitioner Summary: Footwear preference depends on country and assessment methods. Running shoe perception differed between Beijing and Singapore Chinese, suggesting that footwear recommendation should be country-specific. Individuals' shoe preference measured by visual analogue scale when wearing complete pairs may not reflect that when directly comparing different models in left and right feet.     

Integrating a hip belt with body armour reduces the magnitude and changes the location of shoulder pressure and perceived discomfort in soldiers*

Soldiers carry heavy loads that may cause general discomfort, shoulder pain and injury. This study assessed if new body armour designs that incorporated a hip belt reduced shoulder pressures and improved comfort. Twenty-one Australian soldiers completed treadmill walking trials wearing six different body armours with two different loads (15 and 30 kg). Contact pressures applied to the shoulders were measured using pressure pads, and qualitative assessment of comfort and usability were acquired from questionnaires administered after walking trials. Walking with hip belt compared to no hip belt armour resulted in decreased mean and maximum shoulder pressures (p < 0.005), and 30% fewer participants experiencing shoulder discomfort (p < 0.005) in best designs, although hip discomfort did increase. Laterally concentrated shoulder pressures were associated with 1.34-times greater likelihood of discomfort (p = 0.026). Results indicate body armour and backpack designs should integrate a hip belt and distribute load closer to shoulder midline to reduce load carriage discomfort and, potentially, injury risk.

Practitioner Summary: Soldiers carry heavy loads that increase their risk of discomfort and injury. New body armour designs are thought to ease this burden by transferring the load to the hips. This study demonstrated that designs incorporating a hip belt reduced shoulder pressure and shoulder discomfort compared to the current armour design.     

Immediate effects of using insoles with various wedges on center of pressure indices and comfort rating during load lifting

Orthotic devices like insoles are widely used to prevent or correct deformities and improve performance. The aim of present study was to investigate immediate effects of using insoles with various wedges on center of pressure (COP) indices and comfort rating during load lifting. Thirty able-bodied males participated in this quasi-experimental study. Repeated measures analysis of variance test with a Bonferroni correction (P < 0.0014) was used to compare dependent variables among nine insole wedge conditions. The results showed these significant differences: anterior-lateral wedge with anterior and medial wedges for standard deviation of COPx values; anterior-lateral wedge with non-wedge, posterior, lateral and posterior-medial wedges for standard deviation of COPy velocity values; anterior-lateral wedge with anterior and posterior-medial wedges for total mean velocity of COP values (P = 0.001). Also, the anterior-lateral wedge tended to increase in other COP indices and decrease in comfort rating compared to other wedges. Also, a significant negative relation between comfort rating and almost all COP indices was observed during load lifting (P < 0.05). These findings show that using anterior-lateral wedge for insole creates less stability and comfortability which may introduce as a non-optimal condition for insole designation. These results can be useful for designation of shoe or insole for work environments.     

Impact of ballistic body armour and load carriage on walking patterns and perceived comfort

This study investigated the impact of weight magnitude and distribution of body armour and carrying loads on military personnel's walking patterns and comfort perceptions. Spatio-temporal parameters of walking, plantar pressure and contact area were measured while seven healthy male right-handed military students wore seven different garments of varying weight (0.06, 9, 18 and 27 kg) and load distribution (balanced and unbalanced, on the front and back torso). Higher weight increased the foot contact time with the floor. In particular, weight placement on the non-dominant side of the front torso resulted in the greatest stance phase and double support. Increased plantar pressure and contact area observed during heavier loads entail increased impact forces, which can cause overuse injuries and foot blisters. Participants reported increasingly disagreeable pressure and strain in the shoulder, neck and lower back during heavier weight conditions and unnatural walking while wearing unbalanced weight distributed loads. This study shows the potentially synergistic impact of wearing body armour vest with differential loads on body movement and comfort perception.

Practitioner Summary: This study found that soldiers should balance loads, avoiding load placement on the non-dominant side front torso, thus minimising mobility restriction and potential injury risk. Implications for armour vest design modifications can also be found in the results.     

Influence of carrying heavy loads on soldiers' posture,movements and gait

Military personnel are required to carry heavy loads whilst marching; this load carriage represents a substantial component of training and combat. Studies in the literature mainly concentrate on physiological effects, with few biomechanical studies of military load carriage systems (LCS). This study examines changes in gait and posture caused by increasing load carriage in military LCS. The four conditions used during this study were control (including rifle, boots and helmet carriage, totalling 8 kg), webbing (weighing 8 kg), backpack (24 kg) and a light antitank weapon (LAW; 10 kg), resulting in an incremental increase in load carried from 8, 16, 40 to 50 kg. A total of 20 male soldiers were evaluated in the sagittal plane using a 3-D motion analysis system. Measurements of ankle, knee, femur, trunk and craniovertebral angles and spatiotemporal parameters were made during self-paced walking. Results showed spatiotemporal changes were unrelated to angular changes, perhaps a consequence of military training. Knee and femur ranges of motion (control, 21.1° ± 3.0 and 33.9° ± 7.1 respectively) increased (p < 0.05) with load (LAW, 25.5° ± 2.3 and 37.8° ± 1.5 respectively). The trunk flexed significantly further forward, confirming results from previous studies. In addition, the craniovertebral angle decreased (p < 0.001) indicating a more forward position of the head with load. It is concluded that the head functions in concert with the trunk to counterbalance load. The higher muscular tensions necessary to sustain these changes have been associated with injury, muscle strain and joint problems.     

A Review of :“Leu Accidents du Travail.” By JACQUES LEPLAT et XAVIER CUNY. (Paris: Presses Universities de France, 1974.( [Pp.128. £0·00.

Police officers spend large amounts of time performing duties within a police cruiser and report a high prevalence of musculoskeletal problems. This study evaluated the effects of driver seat and duty belt design on posture, pressure and discomfort. Ten male and 10 female university students attended two sessions involving simulated driving in a standard police seat (CV) and an active lumbar support (ALS) seat. Participants wore a full duty belt (FDB) or reduced duty belt (RDB) in each seat. Lumbar postures, driver-seat and driver-duty belt pressures and perceived discomfort were measured. Gender × Seat interactions were found for pelvic (p = 0.0001) and lumbar postures (p = 0.003). Females had more lumbar flexion than males and were more extended in the ALS seat (?9.8 ± 11.3°) than CV seat (?19.8 ± 9.6°). The FDB had greater seat pressure than the RDB (p < 0.0001), which corresponded to increased pelvis discomfort. This study supports the use of an ALS seat and RDB to reduce injury risk associated with prolonged sitting in police officers.

Practitioner Summary: Police officers report a high prevalence of musculoskeletal problems to the lower back, associated with prolonged driving and further investigation is needed to reduce injury risk. This simulated driving study investigated seat and duty belt configuration on biomechanical measures and discomfort. Seat design had the greatest impact, regardless of gender and males benefited more from a reduced belt configuration.     

Wheelchair pushing and turning: lumbar spine and shoulder loads and recommended limits

Abstract

The objective of this study was to determine how simulated manual wheelchair pushing influences biomechanical loading to the lumbar spine and shoulders. Sixty-two subjects performed simulated wheelchair pushing and turning in a laboratory. An electromyography-assisted biomechanical model was used to estimate spinal loads. Moments at the shoulder joint, external hand forces and net turning torque were also assessed. Multiple linear regression techniques were employed to develop biomechanically based wheelchair pushing guidelines relating resultant hand force or net torque to spinal load. Male subjects experienced significantly greater spinal loading (p < 0.01), and spine loads were also increased for wheelchair turning compared to straight wheelchair pushing (p < 0.001). Biomechanically determined maximum acceptable resultant hand forces were 17–18% lower than psychophysically determined limits. We conclude that manual wheelchair pushing and turning can pose biomechanical risk to the lumbar spine and shoulders. Psychophysically determined maximum acceptable push forces do not appear to be protective enough of this biomechanical risk.

Practitioner Summary: This laboratory study investigated biomechanical risk to the low back and shoulders during simulated wheelchair pushing. Manual wheelchair pushing posed biomechanical risk to the lumbar spine (in compression and A/P shear) and to the shoulders. Biomechanically determined wheelchair pushing thresholds are presented and are more protective than the closest psychophysically determined equivalents.     

Evaluation of book backpack load during walking

This investigation evaluated accumulated mean and peak impact forces per stride and per metre associated with two book backpack loads and two cadences during single and double support phases of walking. Thirty college participants randomly performed three trials while either walking a self-selected cadence or fixed cadence without (empty pack) or with a load (15% body mass) carried in a bookbag. The fixed cadence (55.5 steps/min) was regulated by a metronome. A computerized Kistler force platform system (phase-locked timing device) recorded (200 Hz) three-dimensional reaction forces, impulses, and time in single and double support phases. A Panasonic video camera AG-450 was set perpendicular to the plane of walking motion to film (60 Hz) the walking pattern from which stride length and selected kinematic data were determined. Repeated measure ANOVA (p ^< 0.05) determined differences of loads and cadences in walking. Accumulated force was evaluated as impulses per stride and impulses per metre (stress index). When carrying the 15% load, there was a decrease in speed, a decrease in single support time (SST), and an increase in double support time (DST). The impulses per stride significantly increased in DST, and significantly decrease in SST. When impulses were analysed per metre, the stress index signficantly increased in DST, but not during SST. These differences in SST may be important when load stress is applied to the single support leg/foot in any given distance of walking. While stride analysis identifies accumulative forces resulting from varying stride lengths, the stress index provides a standardized measure per metre of the accumulative forces that negate the variances of individual stride lengths, and the index measure can easily represent data for any given distance traversed.     

A methodology for the determination of foamed polymer contraction rates as a result of cryogenic CNC machining

The ability to produce products, suited to a particular individual is becoming more prevalent in today’s society. This requires more efficient and rapid methods for manufacturing of bespoke products. One such method being currently developed is the cryogenic CNC machining of soft materials for producing personalised shoe insoles and outsoles. A major element of cryogenic CNC machining is the freezing of the soft polymers, which subsequently contract. This paper describes a method for predicting and compensating for the effect of cryogenic material contraction for the commonly used shoe midsole foamed polymer, ethylene vinyl acetate (EVA). Using the linear coefficient of thermal expansion a scaling factor for EVA has been developed to enable it to be accurately cryogenically CNC machined. This factor is then applied to the X, Y and Z scaling within the Delcam CAM software to shrink the model. The process is tested for a series of EVA cube test pieces and the results provide a scaling factor, which shows that the linear scaled dimension are within 1% of the measured contracted X, Y and Z dimensions. The scaling factor is subsequently used on an example low density EVA orthotic insole, which is cryogenically machined and then compared dimensionally with the original CAD model. It was found that using the cryogenic contraction factor the cryogenically machined insole had a dimensional X, Y, Z error of less than 1% when compared and analysed with the original CAD model.     

Inter-joint sharing of total support moments in the lower extremities during gait in narrow-heeled shoes of different heights

The study aimed to investigate the influence of the base and height of shoe heels on the total support moment (Ms) and individual joint contributions during gait. Fifteen healthy females walked barefoot and with narrow-heeled shoes (heel heights: 3.9, 6.3 and 7.3 cm) while kinematic and kinetic data were measured. Compared with the barefoot condition, the subjects maintained unaltered Ms in the sagittal plane in shod conditions. This was achieved by increasing the knee extensor moment to compensate for the diminished ankle plantarflexor moments in medium and high heel conditions. In the frontal plane, subjects in shod conditions had to sustain an increased Ms for balance control during late single-leg stance with increased knee abductor and ankle pronator moments as a result of the reduced base of the heels. The results will be helpful for future shoe designs to reduce fall risks and prevent relevant musculoskeletal problems     

The effects of a simulated occupational kneeling exposure on squat mechanics and knee joint load during gait

Occupational kneeling is associated with an increased risk for tibiofemoral knee osteoarthritis. Forces on the knee in the kneeling posture, as well as the greater incidence of meniscus tears among workers, likely contribute to the increased risk. We hypothesise that an additional mechanism may contribute – altered neuromuscular control due to prolonged high knee flexion. Forty participants (20 male, 20 female) completed an evaluation of gait and squatting before, immediately following, and 30 min following a 30 min simulated occupational kneeling exposure. An increase in the peak external knee adduction moment and a delay in vastus medialis activation onset during walking were observed post-kneeling, as well as increased frontal plane knee motion during squatting. This was the first investigation to find changes in high flexion transitions as a result of kneeling. Greater frontal plane knee motion may increase the risk for meniscal tears, and subsequently, knee osteoarthritis.

Practitioner Summary: A 30 min simulated occupational kneeling exposure resulted in small but significant gait changes. The greatest effect was on frontal plane knee movement during squatting, which is especially relevant to occupations requiring frequent kneeling/squatting. This increased motion may indicate an increased risk of injury, which supports a link to knee osteoarthritis.     

Perceived musculoskeletal symptoms among dental students in the clinic work environment

Musculoskeletal symptoms are a major concern among dental practitioners. Dental students perform the same clinical tasks as dentists in private practice, yet only recently has scientific evidence suggested a relationship between the tasks and musculoskeletal symptoms. This study investigates the clinical tasks that place students at physical risk and the relationship between the tasks and musculoskeletal symptoms. Student perceptions of physical symptoms were established with a questionnaire identifying variables on general health, tasks, physical demands, workload and environment. A total of 61% (358/590) reported that during the past year they experienced musculoskeletal symptoms related to work at dental school (second year (n = 212), third year (n = 201) and fourth year (n = 177)). Of those students, the neck represented 48%, shoulder 31%, back 44% and hands 20% (p < 0.001). Third year students reported the highest occurrence of symptoms in every body area (p < 0.001). Third and fourth year students reported significant relationships between the occurrence of symptoms and equipment utilisation, work efficiency and general health. Further studies are recommended to evaluate types and levels of potential risk factors. A total of 75% of dental practitioners are at risk for developing work-related musculoskeletal disorders. Results from this study have found that dental students were no exception. Third year dental students reported the highest level of musculoskeletal symptoms with the prevalence of pain in the neck, shoulder and lower back.     

基于薄膜压力传感器的矫形鞋垫个性化定制方法

矫形鞋垫对治疗足部疾病和足部引起的生物力疾病有显著的疗效。借助3D打印技术,矫形鞋垫能够高效、便捷地被制造出来。鞋垫加厚厚度的变化对患者足底疼痛点位置、足底局部集中力影响很大,严重影响矫正效果,鉴于适合患者行走的3D打印矫形鞋垫的设计模型需要有其足底的几何模型和受力数据,但是现有的模型参数设定大多依赖于医生的经验来量化其大小,为此本文提出了通过穿戴足底压力检测装置获取患者的足底压力数据,依据压力中心轨迹的位置与大小计算矫形鞋垫局部加厚厚度,经过个性化定制流程,可以较科学地实现矫正目标。     

Reducing whole-body vibration and musculoskeletal injury with a new car seat design

A new car seat design, which allows the back part of the seat (BPS) to lower down while a protruded cushion supports the lumbar spine, was quantitatively tested to determine its effectiveness and potentials in reducing whole-body vibration (WBV) and musculoskeletal disorders in automobile drivers. Nine subjects were tested to drive with the seat in: 1) the conventional seating arrangement (Normal posture); and 2) the new seating design (without BPS (WO-BPS) posture). By reducing contact between the seat and the ischial tuberosities (ITs), the new seating design reduced both contact pressure and amplitude of vibrations transmitted through the body. Root-mean-squared values for acceleration along the z-axis at the lumbar spine and ITs significantly decreased 31.6% (p < 0.01) and 19.8% (p < 0.05), respectively, by using the WO-BPS posture. At the same time, vibration dose values significantly decreased along the z-axis of the lumbar spine and ITs by 43.0% (p < 0.05) and 34.5% (p < 0.01). This reduction in WBV allows more sustained driving than permitted by conventional seating devices, by several hours, before sustaining unacceptable WBV levels. Such seating devices, implemented in large trucks and other high-vibration vehicles, may reduce the risk of WBV-related musculoskeletal disorders among drivers.