Article

A comparison of external plantar loading and in vivo local metatarsal deformation wearing two different military boots

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Abstract

The introduction of the M90 boot with a more flexible outer sole to military recruits in Sweden was accompanied by an increase in second metatarsal stress fractures. This study compared the new boot with the previous, stiffer model. A combination of external plantar pressure measurement (two subjects) and an in vivo measurement of dorsal metatarsal strain (six subjects) using strain gauge instrumented staples was implemented. Walking in both boot models resulted in increased plantar pressure under the heads of the lesser metatarsals and generally decreased loading under the remainder of the foot. Dorsal metatarsal tension increased for subjects wearing the new boot throughout a walking protocol.

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... : limitation des mouvements du pied par la chaussure militaire [485] 6.6.3. Effets de la semelle de la chaussure : La rigidité de la semelle dans la région de l'avant-pied des bottes militaires joue un rôle significatif au niveau de l'articulation métatarsophalangienne (468)(485)(488)(491) et l'articulation de la cheville le long de la phase d'appui (487). ...
... Effets de la semelle de la chaussure : La rigidité de la semelle dans la région de l'avant-pied des bottes militaires joue un rôle significatif au niveau de l'articulation métatarsophalangienne (468)(485)(488)(491) et l'articulation de la cheville le long de la phase d'appui (487). Pour souligner ce fait, lorsque l'armée suédoise a changé d'une botte de combat M59 à une botte de combat M90 avec une semelle plus flexible sous l'articulation MTP, il y a eu une augmentation ultérieure des fractures de stress du deuxième métatarsien (485). Il a été constaté que la cause de la blessure était une augmentation des contraintes métatarsiennes lors de la marche dans la chaussure M90, potentiellement due à un soutien inadéquat dans la région de l'avant-pied en raison de la flexibilité accrue (485). ...
... Pour souligner ce fait, lorsque l'armée suédoise a changé d'une botte de combat M59 à une botte de combat M90 avec une semelle plus flexible sous l'articulation MTP, il y a eu une augmentation ultérieure des fractures de stress du deuxième métatarsien (485). Il a été constaté que la cause de la blessure était une augmentation des contraintes métatarsiennes lors de la marche dans la chaussure M90, potentiellement due à un soutien inadéquat dans la région de l'avant-pied en raison de la flexibilité accrue (485). En ce qui concerne le coût énergétique, il a été montré que la rigidité optimale de l'avant-pied peut être donnée par une courbe en forme de U (490). ...
Thesis
INTRODUCTION : In the military environment, the function of the foot is constrained by the daily wearing of combat boots, a veritable orthopedic brace. A significant segment of the military population reports shoe-related foot disorders and pain, but there is little research evaluating the effects of military footwear on the development of these disorders, both internationally and in the Algerian context. The main objective of this work was to evaluate the effects of regular wearing of Rangers type military footwear on the soldier's foot, by studying the incidence of musculoskeletal and skin disorders affecting the ankle-foot complex during a 12-month follow-up period, and by comparing foot health status before and after wearing military footwear. SUBJECTS AND METHODS : This is a prospective study of the longitudinal type on a population of young male adults following their training in a military school in the south-east of Algeria. These new recruits were observed for a period of twelve months with regular wearing of Rangers type military footwear. This follow-up period extends from T0 to T12 knowing that T0 corresponds to the date of incorporation, and T12 corresponds to twelve months after the start of military training. During this period, we recorded all the cases consulting for a problem of the foot or the ankle, on a register created especially for this purpose. Foot status was analyzed at T0 and at T12 using three evaluation methods : clinical, podoscopic and functional. The footprint taken by the electronic podoscope was analyzed by calculating the Chippaux Smirak Index (CSI) and measuring the Alpha angle (α) of hallux valgus and the Beta angle (ß) of quintus varus of the two feet. To assess the functional impact, we opted for the use of the scale "Lower Extremity Functional Scale" in its Arabic version (LEFS-Ar). Furthermore, a comparative analysis before after wearing the shoe was carried out for the different parameters studied. RESULTS : 426 soldiers are participating in this study, of which 384 have completed all stages of the protocol. In this young adult population (mean age = 19.5 ± 0.89 years), the cumulative incidence of all foot and ankle disorders was estimated at 80.5%. The incidence of musculoskeletal disorders is higher than that of dermatological disorders (64.6% versus 38.5%). The main risk factors retained are footwear mismatch, obesity, lower limb misalignments, lower limb previous injuries, and anatomical shape of the foot. Abstract The comparison of foot statue before and after wearing combat boots (T0/T12) showed a significant upward trend in the prevalence of the majority of foot disorders. This difference concerns the musculoskeletal disorders such as hallux valgus, quintus varus, claw toes and overlapping toes, and the dermatological disorders such as corns, calluses, blisters, wounds, and onychodystrophies. Comparative analysis of the T0/T12 footprint indicates a significant increase in the CSI (p < 0.001), the Alpha angle (α) of hallux valgus on the left foot (p < 0.005), and the Beta angle (ß) quintus varus on both feet (p < 0.001). Regarding the evolution of the functional state from T0 to T12, we observe a very significant regression (p < 0.005) in the LEFS-Ar score. DISCUSSION & CONCLUSION: These results confirm that podiatric disorders remain fairly common among military personnel. Its frequency seems to worsen with the wearing of Rangers type military footwear. These epidemiological data, obtained in a completely original way, can help in the planning of future prevention interventions. Keywords: Military footwear, foot deformities, musculoskeletal disorders, footprint, Chippaux Smirak Index, Lower Extremity Functional Scale, Algeria
... Previous research examining military, hiking and casual boots highlight that differences in boot design alter foot movement and, in turn, lead to changes in plantar pressures that have been associated with lower limb injuries (Arndt, Westblad, Ekenman, & Lundberg, 2003, Hamill & Bensel, 1996, Nunns, Stiles, & Dixon, 2012, Sinclair & Taylor, 2014. For example, an army boot with a more flexible sole led to an increase in dorsal tension under the second metatarsal when two participants (Participant 1: mass ¼ 90 kg; Participant 2: mass ¼ 70 kg) walked on a treadmill (Arndt et al. 2003). ...
... Previous research examining military, hiking and casual boots highlight that differences in boot design alter foot movement and, in turn, lead to changes in plantar pressures that have been associated with lower limb injuries (Arndt, Westblad, Ekenman, & Lundberg, 2003, Hamill & Bensel, 1996, Nunns, Stiles, & Dixon, 2012, Sinclair & Taylor, 2014. For example, an army boot with a more flexible sole led to an increase in dorsal tension under the second metatarsal when two participants (Participant 1: mass ¼ 90 kg; Participant 2: mass ¼ 70 kg) walked on a treadmill (Arndt et al. 2003). Further testing confirmed the flexibility in the army boot's sole was most notable under the metatarsophalangeal joint, explaining the increased dorsal tension under the second metatarsal because the foot was able to flex more in this region of the foot (Arndt et al., 2003). ...
... For example, an army boot with a more flexible sole led to an increase in dorsal tension under the second metatarsal when two participants (Participant 1: mass ¼ 90 kg; Participant 2: mass ¼ 70 kg) walked on a treadmill (Arndt et al. 2003). Further testing confirmed the flexibility in the army boot's sole was most notable under the metatarsophalangeal joint, explaining the increased dorsal tension under the second metatarsal because the foot was able to flex more in this region of the foot (Arndt et al., 2003). Sole cushioning appears to also influence plantar pressures by influencing how the foot adapts to the ground reaction forces generated during running. ...
Article
Full-text available
This study investigated the effects of wearing two standard underground coal mining work boots (a gumboot and a leather lace-up boot) on plantar pressures when participants walked across a simulated underground coal mine surface. In-shoe plantar pressures were recorded as 20 male participants walked at a self-selected pace across a hard dirt surface while wearing each boot type. Walking in a gumboot, compared to a leather lace-up boot, resulted in increased plantar pressures and forces, particularly under the heel and forefoot areas. Increased plantar pressures and forces over a long time period is not only a risk factor for painful foot conditions, such as ulcers but also overuse injuries such as stress fractures. The leather lace-up boot might be a better safety footwear option for underground coal miners working under these conditions.
... Flat feet, fallen arches, and plantar fasciitis are overuse injuries that are prevalent in the general population 1 and are even more common within the athletic 2 and military populations (Accident Compensation Corporation [ACC] data). 3,4 Findings from research undertaken by various groups support the theory that these injuries are caused, at least in part, by inadequate support from footwear, 5 and in particular, by insuffi cient support to the medial longitudinal arch of the foot and inadequate shock absorption. 5,6 This fi nding has important implications as it means that such injuries are preventable in most cases by wearing adequate support. ...
... 3,4 Findings from research undertaken by various groups support the theory that these injuries are caused, at least in part, by inadequate support from footwear, 5 and in particular, by insuffi cient support to the medial longitudinal arch of the foot and inadequate shock absorption. 5,6 This fi nding has important implications as it means that such injuries are preventable in most cases by wearing adequate support. [7][8][9] The biomechanical complications associated with the injuries indicated may lead to more serious conditions. ...
... A range of studies have investigated the practical implications of orthotic use as a preventative measure, 17 many of which have involved military personnel. 5,6,12,18 Not all results were positive; some studies suggested that orthotic use was ineffective or the resulting injury prevention capabilities were minimal. 17 Many reasons for such differences in outcome have been suggested, small sample sizes being the most frequent. ...
Article
Full-text available
At any one time, 10% of personnel within the New Zealand Army are affected by injuries caused by inadequate footwear. The purpose of this study was to assess the feasibility of addressing this problem by orthotic issue on the basis of a novel screening protocol. A total of 909 military personnel were included in this study. Data were collected over 3 months, and injuries of interest included stress fractures of the lower limb, foot, or back; chronic pain or discomfort in the hip, knee, or lower back; overuse injury in the ankle, knee, or hip; and plantar fasciitis. A novel screening protocol was used to prescribe orthotics (n = 47/102) as a preventative measure in a cohort of recruits. All injuries were significantly reduced (p = 0.000) in the intervention group compared to control, with the exception of stress fracture of the femur and overuse lower limb injury (p = 0.106 and p = 0.108, respectively).
... Footwear can also have a significant influence on gait by restricting motion of the foot [37,46,[48][49][50][51][52][53]. This restriction can result in increased loading at the ankle, knee and hip as well as decreased energy absorption during certain parts of the stance phase [48,49]. ...
... Footwear can also have a significant influence on gait by restricting motion of the foot [37,46,[48][49][50][51][52][53]. This restriction can result in increased loading at the ankle, knee and hip as well as decreased energy absorption during certain parts of the stance phase [48,49]. This can in turn result in compensatory gait changes [49]. ...
... A study examining boot stiffness throughout the stance phase concluded that the primary effects of boot stiffness are limited to the ankle [50]. This is however in contrast to other work suggesting sole stiffness plays a significant role at the metatarsophalangeal (MTP) joint [45,48,51]. To highlight this fact, when the Swedish Army changed from a M59 combat boot to a M90 combat boot with a more flexible sole under the MTP joint, there was a subsequent increase in stress fractures of the second metatarsal [48]. ...
Article
Full-text available
Injuries are common within military populations, with high incidence rates well established in the literature. Injuries cause a substantial number of working days lost, a significant cost through compensation claims and an increased risk of attrition. In an effort to address this, a considerable amount of research has gone into identifying the most prevalent types of injury and their associated risk factors. Collective evidence suggests that training and equipment contribute to a large proportion of the injuries sustained. In particular, the large loads borne by soldiers, the high intensity training programs and the influence of footwear have been identified as significant causative factors of lower limb injury in military populations. A number of preventative strategies have been developed within military bodies around the world to address these issues. The relative success of these strategies is highly variable; however, with advancements in technology, new approaches will become available and existing strategies may become more effective.
... rubber is more flexible (less stiff) than leather), the amount of reinforcing built into the shaft, the addition of a thick liner and the shaft height (see Fig. 1). Load-deformation curves obtained with equipment such as strain gauges (Arndt et al., 2003), robot manipulators (Cikajlo and Matjaci c, 2007) and load cells (B€ ohm and H€ osl, 2010) are used to quantify boot shaft stiffness. ...
... The remaining studies that have investigated effects of variations in boot sole flexibility on gait have focused on loading properties and implications for lower limb shock absorption. An example is a study conducted by Arndt et al. (2003) who investigated the introduction of a military boot (see Fig. 4) with a more flexible sole for Swedish military recruits. The study authors hypothesised that a military boot with a more flexible sole would increase comfort by not restricting natural foot motion while walking. ...
... The study authors hypothesised that a military boot with a more flexible sole would increase comfort by not restricting natural foot motion while walking. Introducing a military boot with a more flexible sole, however, was correlated with an increased incidence of second metatarsal stress fractures (Arndt et al., 2003). Upon further testing, involving the study participants walking on a treadmill, the effects of the increase in sole flexibility were most notable underneath the metatarsophalangeal joint. ...
Article
Safety boots are compulsory in many occupations to protect the feet of workers from undesirable external stimuli, particularly in harsh work environments. The unique environmental conditions and varying tasks performed in different occupations necessitate a variety of boot designs to match each worker's occupational safety and functional requirements. Unfortunately, safety boots are often designed more for occupational safety at the expense of functionality and comfort. In fact, there is a paucity of published research investigating the influence that specific variations in work boot design have on fundamental tasks common to many occupations, such as walking. This literature review aimed to collate and examine what is currently known about the influence of boot design on walking in order to identify gaps in the literature and develop evidence-based recommendations upon which to design future research studies investigating work boot design.
... In all over-theankle footwear the ankle joint movement is hindered, therefore footwear stiffness may be an even more important feature. Various studies have analysed the influence of outer sole flexibility (heel and bending stiffness) on the power of impact or impact absorption (Arndt et al. 2003, Dixon et al. 2003 and suggested that the decreased mechanical stiffness of the sole results in an enhanced ability to decrease the power of the heel impact and therefore prevent potential injuries. Indeed, the footwear sole stiffness has to preserve a certain level of hardiness to prevent potential foot or ankle injuries. ...
... The protocol comprised four consecutive experimental conditions: 1. gait wearing footwear 1; 2. gait wearing footwear 2; 3. gait wearing footwear 1 and carrying a 20 kg backpack; 4. gait wearing footwear 2 and carrying a 20 kg backpack. The weight of the backpack was based on the middle-sized military backpack (Arndt et al. 2003, Stevenson et al. 2004. Within each of the experimental conditions several walking trials were undertaken. ...
... These findings were possible only with entire functional boot stiffness analysis and are based on a comparison of two functionally and purposely similar boots. Shoe and boot stiffness or bending is usually tested by inserting strain gauges (Arndt et al. 2003) and/or deformation measurement by an optical system. In our study, the boot stiffness analysis was made possible by a custom-made robot (Nemec et al. 1998) and a foot model with an ankle joint and a metatarsal joint inserted into the boot. ...
Article
Full-text available
In the study, the influence of different boot prototype stiffness on gait kinematics and kinetics was investigated. The boot stiffness was determined by force-deformation measurement while pressing the foot model inserted into the boot by a custom-made robot. Gait analysis was carried out in nine neurologically intact subjects during walking while wearing two different boots with and without carrying a backpack, and differences were statistically tested using ANOVA. The results indicated distinctions in the boot shaft and vamp stiffness. The boot with a softer boot shaft enabled a wider range of motion in the ankle joint leading to more power generation in the ankle joint during the push-off, increased step length and gait velocity. The backpack mostly influenced the pelvis and trunk kinematics. The study has demonstrated the influence of boot shaft stiffness on biomechanical gait parameters and its importance for push-off that manufacturers should take into consideration when optimizing the footwear performance.
... These types of injuries resulted from completing military tasks are common and extremely costly in terms of medical treatment and rehabilitation [2]. In the literature, the most common injuries in military recruits were found in the ankle and foot areas [3], especially stress fractures of different foot regions [4,5]. Reports showed that 35% of the females and 41% of the males of military recruits have at least one stress fracture in the foot, with the most occurrence in the metatarsals regions [4]. ...
... In the literature, the most common injuries in military recruits were found in the ankle and foot areas [3], especially stress fractures of different foot regions [4,5]. Reports showed that 35% of the females and 41% of the males of military recruits have at least one stress fracture in the foot, with the most occurrence in the metatarsals regions [4]. If the pressure under the metatarsal head region increases, the risk of metatarsal stress fracture will be higher [6]. ...
... Also, Weist et al. (2004) [8] stated that the fatigue can alter lower limb loading and increase the risk of overuse injuries. Hence, the assessment of plantar pressure measurements can be considered as a new method to recognize the risk of injuries [6,7] and identify the effectiveness of using various modalities (like shoe and insole) [4,[9][10][11]. ...
Preprint
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Background: Orthotic devices like insoles are widely used to improve performance. This study investigated whether immediate effects of using insoles with various wedges influence on plantar pressure measurements and comfort level during marching. Methods: Twenty five able-bodied males participated in this study voluntarily. Repeated measures analysis of variance test with a Bonferroni correction (P<0.0014) was used to compare dependent variables among nine insole wedge conditions. Results: The result of present study showed that the comfort level was non-significantly higher in the anterior and medial wedges compared to the posterior-lateral and anterior-lateral wedges during marching (P>0.0014). The peak of plantar pressure and impulse in the first to third metatarsal regions decreased in the anterior, medial and anterior-medial wedges compared to the lateral and posterior-lateral wedges (P<0.0014). In addition, a significant negative relation between the comfort level and plantar pressure measurements was observed in the second and third metatarsals and midfoot regions during marching (P<0.05). Conclusion: It seems that using anterior, medial and anterior-medial wedge for insole may have some advantage through increasing comfort sense and decreasing the risk of stress fracture injuries in the second and third metatarsal regions. These findings should be considered during designation of shoes or insoles for military environments.
... Of those miners who listed foot and/or ankle pain, 62.3% associated this pain with their mining work boots (Dobson et al., 2018a). High plantar pressures generated during walking have been associated with the development of lower limb pain (Aliberti et al., 2011;Willems et al., 2006) and linked to a greater risk of developing uncomfortable pressure sores, such as ulcers, and overuse injuries such as stress fractures (Arndt et al., 2003;Mohamed et al., 2005). Therefore, it is likely that this foot discomfort and pain reported by underground coal miners is at least partially associated with high plantar pressures being generated when the miners walk in their work boots. ...
... Previous research examining mining, military, hiking and casual boots has shown that altered foot mechanics due to different boot designs can lead to changes in loading of the plantar surface of the foot during walking (Hamill and Bensel, 1996;Nunns et al., 2012;Arndt et al., 2003;Sinclair and Taylor, 2014;Dobson et al., 2018c). Shaft stiffness and sole flexibility appear to be key boot design features that affect foot motion and, in turn, the plantar pressures generated during gait (Dobson et al., 2017b). ...
... The researchers of this study speculated that the participants' ankles and feet moved more inside the less structured gumboot, requiring the miners to push off more from the forefoot when walking in the gumboot compared to the structured leather boot, causing these higher gumboot-related plantar pressures (Dobson et al., 2018c). Similarly, an army boot with a more flexible sole increased dorsal tension under the second metatarsal when two participants walked on a treadmill (Arndt et al., 2003). Increased plantar pressures under the forefoot, particularly around the second metatarsal, are concerning as they are a risk factor for stress fractures (Arndt et al., 2003;Nunns et al., 2012). ...
Article
The structural features of work boots worn by underground coal miners affect comfort, foot motion and, in turn, loading of the plantar surface of miners' feet. Although shaft stiffness and sole flexibility appear to be boot design features that could influence perceived comfort and plantar pressures, no study has systematically altered these boot design features to truly understand how they affect these parameters. This study aimed to systematically investigate the effect of changes to shaft stiffness and sole flexibility on perceived comfort and plantar pressures when 20 males walked on a simulated gravel coal mining surface under four different work boot conditions. There were no significant effects of shaft stiffness or sole flexibility on perceived comfort. However, shaft stiffness and sole flexibility each significantly affected the plantar pressures generated under the medial midfoot, heel, middle metatarsals and hallux and, in combination, affected plantar pressures generated beneath the lateral midfoot, medial and lateral metatarsals and lesser toes. Participants preferred a boot with a flexible shaft combined with a stiff sole, citing properties such as fit, moveability, walking effort and support to explain why they perceived one boot as more comfortable than another. We therefore recommend that underground coal mining work boots should be designed to incorporate different flexibility and stiffness between the shaft and sole of the boot to optimise foot movement and, in turn, walking efficiency.
... These types of injuries resulted from completing military tasks are common and extremely costly in terms of medical treatment and rehabilitation [2]. In the literature, the most common injuries in military recruits were found in the ankle and foot areas [3], especially stress fractures of different foot regions [4,5]. Reports showed that 35% of the females and 41% of the males of military recruits have at least one stress fracture in the foot, with the most occurance in the metatarsals regions [4]. ...
... In the literature, the most common injuries in military recruits were found in the ankle and foot areas [3], especially stress fractures of different foot regions [4,5]. Reports showed that 35% of the females and 41% of the males of military recruits have at least one stress fracture in the foot, with the most occurance in the metatarsals regions [4]. If the pressure under the metatarsal head region increases, the risk of metatarsal stress fracture will be higher [6]. ...
... Also, Weist et al. (2004) [8] stated that the fatigue can alter lower limb loading and increase the risk of overuse injuries. Hence, the assessment of plantar pressure measurements can be considered as a new method to recognize the risk of injuries [6,7] and identify the effectiveness of using various modalities (like shoe and insole) [4,[9][10][11]. ...
Preprint
Full-text available
Background: Orthotic devices like insoles are widely used to improve performance. This study investigated whether immediate effects of using insoles with various wedges influence on plantar pressure measurements and comfort level during marching. Methods: Twenty-five (n=25) able-bodied males participated in this study voluntarily. Repeated measures analysis of variance test with a Bonferroni correction (P<0.0014) was used to compare dependent variables among nine insole wedge conditions. Results: The result of present study showed that the comfort level was non-significantly higher in the anterior and medial wedges compared to the posterior-lateral and anterior-lateral wedges during marching (P>0.0014). The peak of plantar pressure and impulse in the first to third metatarsal regions decreased in the anterior, medial and anterior-medial wedges compared to the lateral and posterior-lateral wedges (P<0.0014). In addition, a significant negative relation between the comfort level and plantar pressure measurements was observed in the second and third metatarsals and midfoot regions during marching (P<0.05). Conclusion: It seems that using anterior, medial and anterior-medial wedge for insole may have some advantage through increasing comfort sense and decreasing the risk of stress fracture injuries in the second and third metatarsal regions. These findings should be considered during designation of shoes or insoles for military environments.
... Recently, not only has increased forefoot bending stiffness been proposed as a method for the treatment of these types of MTP joint injuries, but also as a preventive method of reducing the risk of athletes suffering these injuries, specifically in the National Football League (Crandall, Frederick, Kent, Lessley, & Sherwood, 2015). Aside from turf-toe, alterations in forefoot bending stiffness of footwear may be utilized for treatment and prevention of other foot related injuries such as metatarsal stress fractures by altering the loading acting on the foot during locomotion (Arndt, Westblad, Ekenman, & Lundberg, 2003). In terms of performance, research investigating forefoot bending stiffness has shown that altering the stiffness can influence performance of running (Roy & Stefanyshyn, 2006), sprinting (Stefanyshyn & Fusco, 2004), jumping (Stefanyshyn & Nigg, 1998) and multidirectional movements (Tinoco, Bourgit, & Morin, 2010). ...
... Directly, a study by Arndt et al. (2003) investigated the influence of bending stiffness on the in vivo loading experienced by the metatarsals during walking. First, the study examined both the external plantar pressure during treadmill walking to fatigue in a flexible and stiff military boot of two participants. ...
Article
Forefoot bending stiffness is a footwear property that has recently been gaining interest despite previously receiving limited attention compared to other footwear characteristics. This review focuses on relevant research studies examining the influence of forefoot bending stiffness on reducing injury and optimizing performance. Discussion of the current limitations and need for future research within the realm of forefoot bending stiffness is also highlighted. By reducing the amount of metatarsophalangeal extension, increased bending stiffness could not only reduce injury risk (e.g. turf-toe), but also serve as a treatment for metatarsal stress fractures by offloading the metatarsals. However, there are surprisingly limited in-depth studies examining how altered forefoot bending stiffness influences injury. Many unknown factors still need to be studied including the appropriate magnitude of bending stiffness and the influence that altering forefoot bending stiffness may have on the injury risk of other joints such as the ankle and knee. Forefoot bending stiffness can influence performance; however, the exact mechanism remains unclear. Early studies focused on foot energetics, while recent studies have shown the importance of altering the movement of the centre of pressure under the foot and the gearing ratio at the ankle joint. There appears to be a specific amount of forefoot bending stiffness for optimal performance. Future research should focus on identifying the exact mechanism of performance improvement with modified bending stiffness to help determine how this optimal stiffness can be identified.
... Therefore, it is necessary to understand the way boot comfort is perceived and how it can be increased to develop military boots. Furthermore, the risk of sustaining a stress fracture is increased in military recruit populations [MILGROM ET AL, 1985], but relationship between the bending stiffness of military boots, increased peak pressures and resulting metatarsal strain has only been partially assessed up to date [ARNDT ET AL, 2003]. ...
... Peak pressures underneath MH2|3 as well as relative loads in the heel region appear to be closely related to comfort in military boots. Adjusting boot characteristics to plantar pressure variables may be a promising approach in order to increase comfort and reduce the risk for metatarsal strain injuries [ARNDT ET AL, 2003]. ...
... Stress fractures are common injuries in dancers, 1-8 athletes [8][9][10][11][12][13][14] and military personnel, 15 especially to the lower extremities. Stress fractures are a manifestation of repeated bone stress in occurrence with defined risk factors. ...
... 9 16 They are largely thought to be over use injuries. 9 In the general population, the shaft of the second metatarsal is the site most at risk of developing a stress fracture. 17 18 However, it has been shown in ballet dancers that the base of the second metatarsal is the most common location for a stress fracture, 17 18 with this site being a high-risk location. ...
Article
A 15-year-old female Highland dancer presented to the accident and emergency department with an ankle inversion injury on a background of several weeks of pain in the right foot. A radiograph of the right foot demonstrated a stress fracture at the base of the second metatarsal. She was treated conservatively with a below knee removable supportive walking boot with a rocker bottom sole. She re-presented to the accident and emergency department 3 weeks later with pins and needles in the right foot; she was given crutches to use along side the supportive walking boot. Radiographs 12 weeks after the first presentation showed healing of the stress fracture. The patient was now asymptomatic of the injury. She was unable to fully train for 12 weeks due to the injury. Conservative management was successful in this patient.
... Rosenbaum et al. 1994, Weist et al. 2004, Bisiaux and Moretti 2008 or grouped with the fourth and fifth metatarsals (e.g. Perry et al. 1995, Arndt et al. 2002, 2003, Nagel et al. 2008. These approaches may be justified for the purposes of the individual studies, but to further the understanding of individual metatarsal stress fracture aetiology, study of specific metatarsal loading seems more appropriate. ...
... This may be due to differences in the boots tested (German army boot in Hinz et al.), or differences in pressure distribution between walking and running. Arndt et al. (2003) demonstrated that impulse in the MT2-MT5 region during a fatiguing walk was lower in a more flexible-soled Swedish military boot compared to a stiffer one, although this was not evaluated statistically, and Chuckpaiwong et al. (2008) demonstrated in barefoot locomotion that the order of magnitudes of pressure and impulse changed between running and walking. The higher MT3 head region loading in the CAB suggests higher loading on this bone for this boot condition compared with the GT. ...
Article
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Purpose: The relatively high incidence rate of third metatarsal (MT3) stress fractures in Royal Marine (RM) recruits may be linked to the footwear worn during training. The present study investigated the effect of standard issue RM recruit footwear on biomechanical variables linked with MT3 stress fracture risk.Methods: Seven male volunteers (age 18.3 ± 0.4 years, mass 81.1 ± 8.2 kg) ran at 3.6 m s in a laboratory while wearing a combat assault boot (CAB) and a neutral gym trainer (GT). In-shoe plantar pressure was assessed using pressure insoles (RSScan, 500 Hz). Two-dimensional ankle kinematics and kinetics were assessed at 120 Hz (Peak Motus). Horizontal ground reaction force characteristics were investigated using an AMTI force plate (960 Hz).Results: Peak plantar pressure, impulse and loading rate were significantly greater at the MT3 head in the CAB (P
... [9][10][11] In comparison to commercial footwear (i.e., running shoes), standard issue military boots have a low energy return, higher weight, and are less flexible in the upper as well as the sole. [11][12][13] Although the military boot is durable, stabilizes the ankle, and offers protection from direct trauma, it lacks the shock-absorbing qualities and flexibility of the running shoe. 14 These factors can accelerate energy loss and lead to the onset of muscle fatigue and additional stress on the plantar aspects of the foot. ...
... 14 These factors can accelerate energy loss and lead to the onset of muscle fatigue and additional stress on the plantar aspects of the foot. [11][12][13] It has also been suggested that military boots have lower shock attenuation compared to commercial footwear, which is an important biomechanical risk factor for musculoskeletal injury. 9,11,[15][16][17] In addition, not all types of military boots are the same (i.e., combat boot and jungle boot). ...
Article
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Injuries acquired during Reserve Officer Training Corps (ROTC) participation can potentially affect a cadet's future and career in the armed forces. The purpose of this study was to identify risk factors associated with lower extremity injuries in an Army ROTC cadet population. There were 195 (165M, 30F) cadets enrolled in an Army ROTC program, 18 to 33 years old, with an average body mass index (BMI) of 23.5 ± 2.85. Injury data were retrospectively obtained from the electronic medical records maintained by a Certified Athletic Trainer. Descriptive statistics, frequencies, and incidence rate for physical training (PT) were calculated. Survival analysis determined association between injury and several variables (Military Science [MS] year, army physical fitness test scores, BMI, sex, previous lower extremity injury, PT exposures, most frequent boot worn, current and prior physical activity, and collision sport participation). Kaplan-Meier curves were used for the categorical variables. Incidence rate was 60 lower extremity injuries/100 person-years during PT. The survival analysis revealed MS year (p < 0.001) and PT exposures (p < 0.001) were significant in predicting risk of injury. All other variables were not significant. On the basis of this preliminary data, footwear and activity have no implications on risk of lower extremity injury. Preventative measures should be focused toward younger cadets because of their increased risk for injury. Reprint & Copyright © 2015 Association of Military Surgeons of the U.S.
... No attention has previously been given to the potential implications of a MS, FS or TR style on loading at the metatarsal heads, which are likely to be subjected to greater load for these footstrike modalities. This is despite evidence suggesting that increased metatarsal loading may increase the risk of metatarsal stress fractures (Arndt et al., 2003;Nagel et al., 2008;Nunns et al., 2012). Measurement of plantar pressure during barefoot running in the current study allows a comparison of the magnitude and timing of peak pressures and impulse at specific regions of the foot. ...
... As hypothesised, plantar pressure data indicated that forefoot loading was greater in the TR group than other groups, specifically in the medial regions of M1, M2 and HX. Increased magnitude or duration of metatarsal loading has been suggested to increase the risk of injury, specifically metatarsal stress fractures (Hughes, 1985;Arndt et al., 2003;Nunns et al., 2012). Case study reports have recently been published detailing metatarsal fractures following the onset of barefoot training with a FS (Giuliani et al., 2011), although Diebal et al. (2012) suggest potential reductions in lower limb pain when adopting this style. ...
... Um estudo com 3758 recrutas do gênero feminino nos Estados Unidos reportaram ocorrência de 8,5% de fratura por estresse após oito semanas de treinamento militar 5 . Tais lesões são associadas ao excesso de treinamento em curto prazo e à utilização de calçado inadequado para as atividades de marcha e corrida 6 . H et al. 7 observaram redução no pico de pressão plantar em coturno militares que utilizaram palmilhas de neoprene, as quais podem ser utilizadas na redução da incidência de fraturas durante marchas militares. ...
... Estudos têm sugerido que a siopatologia da fratura por estresse em militares pode decorrer da fadiga associada à grande carga de pressão plantar 6,8 . As ondas de choque durante a fase de impacto da marcha são relacionadas às lesões de efeito cumulativo, causando desgastes e lacerações dos tecidos ósseo e articular, principalmente se associado à fadiga muscular 9 . ...
Article
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O objetivo do presente estudo foi comparar a absorção de impacto durante a marcha descalço e com tênis e coturno fornecidos pelo Exército Brasileiro. A amostra foi composta por 20 soldados saudáveis recém-incorporados sem sintomas ou lesões musculoesqueléticas ou neurológicas que interferissem na marcha. Os sujeitos foram instruídos a caminhar em uma plataforma de madeira de 10 metros de comprimento por um metro de largura, com duas plataformas de força (Bertec, EUA) embutidas no centro. O componente vertical da força de reação do solo foi avaliado durante a marcha nas situações tênis, coturno e descalço. O sistema de cinemetria (Qualysis, Suécia) foi utilizado para medir a velocidade da marcha em cada situação de teste. O primeiro pico de força (PPF), o tempo para atingir o PPF (T_PPF), pico transiente de impacto (IPF) e a taxa de aceitação do peso (TAP) entre 10% e 30%, 30% e 50%, 50% e 70%, 70% e 90% e 10% e 90% do PPF foram avaliadas. O T_PPF foi em média 1s menor (p < 0,0001), o IPF e a TAP entre 10% e 30% do PPF foram maiores (p < 0,0001, ambos) descalço comparados a marcha com tênis e coturno. Não foi observado diferença estatística nas outras variáveis estudadas nas três condições de teste, bem como em nenhuma variável na comparação entre tênis e coturno. Os calçados avaliados são eficientes em reduzir o impacto durante a marcha por atrasar em média 1 s o tempo em que o PPF foi atingido, reduzir o IPF e a TAP nos primeiros 30% do PPF.
... However, the studies of Stefanyshyn and Nigg [4] proved that the MTP is a large energy absorber during running and sprinting. The importance of the MTP has been also underlined by the studies of Arndt et al. [5], in which they correlated the increased second metatarsal stress fracture with the adoption by military recruits in Sweden of a new type of boot with a more flexible sole. Furthermore Roy and Stefanyshyn [6] investigated the running metabolic economy of a group of subjects wearing shoes with soles of different stiffness values. ...
Article
Full-text available
Understanding the action of the metatarsophalangeal joint (MTP) is fundamental to improving the design process of a new outdoor shoe. Coming from the stated consideration, the aim of this research is to study the influence of shoe sole stiffness and terrain slope on the MTP joint angle of subjects walking in different conditions. To pursue this intent, different data collection sessions have been carried out in-vitro and in-vivo, indoor and outdoor. Two different approaches have been used to collect gait kinematics: an IMU (Inertial Measurement Unit) based system for the first campaign of tests, and a 2D video analysis for the second. Major findings showed a linear correlation between shoe sole stiffness and peak MTP joint angle during gait, as well as consistency in the value of the slope of the linear regression curves corresponding to the different conditions examined.
... The exact reason why nonproximal fractures are more prevalent than proximal fractures is unclear, despite comprehensive biomechanical analysis. [15][16][17] Proximal stress fractures of the second metatarsal are much less common than non-proximal second metatarsal stress fractures. In addition, the recovery time of a proximal fracture is usually prolonged, and delayed and non-union is often seen. ...
Article
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Stress fractures of the second metatarsal are common injuries in athletes and military recruits. There are two distinct areas in the second metatarsal where stress fractures develop: one proximal (at the base) and the other non-proximal (distal). Diagnosis can be difficult, and there is a difference in prognosis and treatment of the two types of stress fracture. Therefore differentiation of fracture location is warranted. Differences in risk factors and clinical outcomes between proximal and non-proximal stress fractures have not been studied. To determine whether different risk factors and/or clinical outcomes associated with proximal and non-proximal stress fractures of the second metatarsal exist. Patients diagnosed with proximal stress fractures of the second metatarsal were included in the study. Retrospectively, an age-matched control group with a non-proximal stress fracture was selected for comparison. Statistical analysis involved bivariate comparisons of demographic variables and clinical measurement between the two groups. Patients with proximal stress fractures were more likely to be chronically affected, usually exhibited an Achilles contracture, showed differences in length of first compared with second metatarsal, were more likely to experience multiple stress fractures, and exhibited low bone mass. In addition, a high degree of training slightly increased the risk of a non-proximal fracture, whereas low training volume was associated with a proximal stress fracture. The signs, symptoms and clinical findings associated with proximal metatarsal stress fractures are different from those of non-proximal stress fractures.
... Invasive in-vivo foot kinematics research has a long history [17][18][19][20][21][22][23][24][25][26] and it has been some of the most cited work in the field (Additional file 2). The key value of this data is its validity in describing how the bones of the foot move, but the key difficulty is how generalisable this data is to the wider population. ...
Article
Full-text available
This paper provides a summary of a Keynote lecture delivered at the 2009 Australasian Podiatry Conference. The aim of the paper is to review recent research that has adopted dynamic cadaver and invasive kinematics research approaches to better understand foot and ankle kinematics during gait. It is not intended to systematically cover all literature related to foot and ankle kinematics (such as research using surface mounted markers). Since the paper is based on a keynote presentation its focuses on the authors own experiences and work in the main, drawing on the work of others where appropriate Two approaches to the problem of accessing and measuring the kinematics of individual anatomical structures in the foot have been taken, (i) static and dynamic cadaver models, and (ii) invasive in-vivo research. Cadaver models offer the advantage that there is complete access to all the tissues of the foot, but the cadaver must be manipulated and loaded in a manner which replicates how the foot would have performed when in-vivo. The key value of invasive in-vivo foot kinematics research is the validity of the description of foot kinematics, but the key difficulty is how generalisable this data is to the wider population. Through these techniques a great deal has been learnt. We better understand the valuable contribution mid and forefoot joints make to foot biomechanics, and how the ankle and subtalar joints can have almost comparable roles. Variation between people in foot kinematics is high and normal. This includes variation in how specific joints move and how combinations of joints move. The foot continues to demonstrate its flexibility in enabling us to get from A to B via a large number of different kinematic solutions. Rather than continue to apply a poorly founded model of foot type whose basis is to make all feet meet criteria for the mechanical 'ideal' or 'normal' foot, we should embrace variation between feet and identify it as an opportunity to develop patient-specific clinical models of foot function.
... A pain-free gait may be achieved via partial weight bearing, using assistive gait devices (ie, double or single crutch, cane, etc) coupled with cushioned shoes and/or insoles to dissipate impact forces in athletes with a tibial BSI 19,41 or with stiff or rocker-soled shoes to reduce metatarsal bending forces in athletes with a metatarsal BSI. 5,56 If a pain-free normal gait pattern cannot be achieved via partial weight bearing, non-weight bearing with crutches or a walking boot may be considered. Use walking boots judiciously, as they alter gait mechanics and contribute to secondary issues proximally and contralaterally, irrespective of whether a heel lift is used to correct any boot-introduced limb-length discrepancy. ...
Article
Background: Low-risk bone stress injuries (BSIs) of the tibia and metatarsal diaphysis account for >50% of BSIs in runners. They interrupt training and are managed using non-invasive approaches. The desire by all involved is for a speedy, but safe return to running. Clinical question: What is the optimal load to manage low-risk tibial and metatarsal BSIs and safely return to running? Key results: Optimal load can be guided by knowledge of the BSI healing process and is symptom driven. At all stages, the optimal load does not produce symptoms during, after, or the day following loading. Clinical application: A period of initial load reduction, via partial- or non-weightbearing, is typically needed to alleviate presenting symptoms. Analgesics or NSAIDs may be used short-term (<7 days), but only in the presence of resting and/or night pain. Healing supplements (e.g. low-intensity pulsed ultrasound and/or recombinant parathyroid hormone therapy) may be attempted to influence tissue healing. Athletes can maintain cardiopulmonary fitness via cross-training, while simultaneously addressing musculoskeletal fitness. A return-to-run program can be initiated once an athlete is pain-free with daily activities for 5 consecutive days. Progress is directed by symptom provocation and initially focuses on increasing running volume before speed. Continue optimal loading following return to running and consider including jump training and/or gait retraining to reduce subsequent BSI risk. The optimal loading approach to managing low-risk tibial and metatarsal BSIs is clinically successful, but requires further scientific validation. J Orthop Sports Phys Ther, Epub 7 May 2021. doi:10.2519/jospt.2021.9982.
... It has been suggested that strain magnitude stimulates the adaptation of the bone ( Milgrom et al., 2000b;Rubin and Lanyon, 1985) if a particular strain threshold is exceeded ( Hsieh et al., 2001). Strain has been measured directly from the tibia ( Burr et al., 1996;Milgrom et al., 2000aMilgrom et al., , b, 2001), radius (Foïdhazy et al., 2005) and second metatarsal (Arndt et al., 2002(Arndt et al., , 2003 of human subjects during different activities. However, the use of invasive measurements is not possible in long-term population-based intervention studies. ...
Article
High acceleration levels (>4g) seen during impact exercises have been shown to increase bone mineral density (BMD) in premenopausal women. The aim of this study was to examine how the other acceleration signal characteristics, i.e. the slope, area and energy of the signal are related to changes in bone density, using long-term quantification of physical activity. Daily physical activity was continuously assessed with a waist-worn accelerometer-based body movement monitor in 64 premenopausal women participating in a 12-month population-based exercise trial. The daily number of exercise-induced impacts at different slope, area and energy levels of the acceleration signal was analyzed. Physical activity inducing slopes 1000 m/s(3), acceleration peak areas 2m/s or signal energies 75 m(2)/s(3) was associated with BMD change in the hip (p<0.05). Impacts with the smallest slopes (<1000 m/s(3)) were positively associated with changes in calcaneal speed of ultrasound, while impacts with slopes 1500 m/s(3) or areas 4m/s were positively correlated with broadband ultrasound attenuation changes (p<0.05). We conclude that the acceleration slope of exercise-induced impacts is an important determinant of bone density. The slope threshold for improving BMD at the hip is 1000 m/s(3), which can be achieved during normal exercise including fast movements such as running and jumping.
... They found that normal compression strain increased significantly in the fatigue state during walking with and without load compared to non-fatigue state, while on the other hand normal tensile strain decreased in the fatigue state. In a follow up study (Arndt et al., 2003), they investigated the effect of two types of military footwear on second metatarsal strains during fatiguing protocol to determine the optimal one for reducing the risk of stress fractures of the second metatarsal. None of the in vivo studies conducted at second metatarsal used three strain gages, and therefore, they were unable to provide principal strains and their directions. ...
Article
Bone strain is the governing stimuli for the remodeling process necessary in the maintenance of bone's structure and mechanical strength. Strain gages are the gold standard and workhorses of human bone experimental strain analysis in vivo. The objective of this systematic literature review is to provide an overview for direct in vivo human bone strain measurement studies and place the strain results within context of current theories of bone remodeling (i.e. mechanostat theory). We employed a standardized search strategy without imposing any time restriction to find English language studies indexed in PubMed and Web of Science databases that measured human bone strain in vivo. Twenty-four studies met our final inclusion criteria. Seven human bones were subjected to strain measurements in vivo including medial tibia, second metatarsal, calcaneus, proximal femur, distal radius, lamina of vertebra and dental alveolar. Peak strain magnitude recorded was 9096 με on the medial tibia during basketball rebounding and the peak strain rate magnitude was -85,500 με/s recorded at the distal radius during forward fall from standing, landing on extended hands. The tibia was the most exposed site for in vivo strain measurements due to accessibility and being a common pathologic site of stress fracture in the lower extremity. This systematic review revealed that most of the strains measured in vivo in different bones were generally within the physiological loading zone defined by the mechanostat theory, which implies stimulation of functional adaptation necessary to maintain bone mechanical integrity. Erratum in: J Biomech. 2012 Feb 2;45(3):623.
... Resistance Strain gauge is widely used for stress and strain measurement in industry, and also in the field of biomechanics recently [11]. In foot-ankle biomechanics, strain gauge is often used to measure strain of joints, muscles, ligaments, and plantar soft tissues [12][13][14][15][16]. Strain gauge force plate system is also used to measure plantar pressure for lowcost [17]. ...
Conference Paper
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It has been well studied that foot-ankle biomechanics plays an important role in body locomotion but still be far from well understanding, to some extent for lack of various biomechanical response information under physiological conditions. In this paper, seven unembalmed cadaver feet were loaded under controlled conditions simulating body weight, and biomechanical responses in multi-fields, such as displacement, strain and plantar pressure, were measured with material test machine, digital speckle correlation method (DSCM) measurement system, resistance strain gauge and F-Scan plantar pressure analysis system. Data gained from such multifields experimental measurement were precise and results were interpreted well. This research is aimed at fostering foot-ankle biomechanics well understanding and promoting further research with reasonable and comprehensive analysis.
... Further, stiff midsoles may act as a supporting structure for the TFM and may prevent them from fatiguing as quickly as in shoes with flexible midsoles. In turn, flexible midsoles indicate greater muscular loading and therefore potentially increase TFM strength (Arndt et al. 2002, Arndt et al. 2003. Additionally, the results of the study showed that training with minimal shoes led to notable increases in strength (up to 10%) of TFM. ...
Article
Full-text available
During the propulsive phase of human locomotion, long and short toe flexor muscles (TFM) are exposed to mechanical stimuli caused by ground reaction forces. Further, flexible footwear seems to facilitate increased loading on foot structures. The purpose of the study was to evaluate the effects of high intensity athletic training with minimal footwear on TFM strength. Forty-seven female sport students participated and were randomly divided in three groups: the experimental group (EG; n = 18; 25 ± 5 yrs, 59 ± 6 kg) and the training control group (TG; n = 18; 23 ± 2 yrs, 64 ± 6 kg) performed high intensity athletic training (3 weeks, 5 times per week, 30 min per session) on the forefoot. The EG wore a minimal shoe, the TG performed the exercises with traditional training shoes. The basic control group (CG; n = 11; 27 ± 5 yrs, 63 ± 7 kg) participated in no training programme. To evaluate the training effects on TFM strength, maximum metatarsal phalangeal joint (MPJ) plantar flexion moments during maximal voluntary isometric contractions (MVIC) at 0° and 25° MPJ dorsal flexion were measured in a custom made dynamometer before and after the training intervention. The results showed that (1) in 0° MPJ dorsal flexion, MPJ moments were significantly increased in the EG (p < 0.01) and TG (p < 0.05) and differed significantly to the CG (p < 0.05); (2) in 25° MPJ dorsal flexion, TFM strength was significantly increased in the EG (p < 0.01), but not in the TG and CG (p > 0.05). In this joint angle position the EG significantly differed from the TG and CG (p < 0.05). The results of the study show that athletic exercises with minimal footwear strengthen TFM after three weeks intensive training.
... The present study is the first to measure simultaneously the effect of wearing shoe orthotics on in vivo axial tibial and 2nd metatarsal strains and strains rates. The effect of shoe gear on 2nd metatarsal strains (Arndt et al. 2002) and the effect of subject fatigue on 2nd metatarsal strains while walking barefoot (Arndt et al. 2003), has previously been reported. One of the orthotics evaluated in this study was found in a prior perspective Israeli Army clinical study to lower the incidence of stress fractures during 14 weeks of infantry training (Finestone et al. 1999). ...
Article
Background: In a previous military study a custom-made tri-layer polyurethane shoe orthotic was shown to be effective in lowering the incidence of stress fractures in infantry recruits. Stress fractures are caused by repetitive high strains. Objective: To compare the effect of tri-layer polyurethane orthotics with other types of orthotics on in vivo strains at sites where stress fractures are common. Design: Subjects underwent surgical implantation of strain gauged staples to the dorsal surface of the midshaft 2nd metatarsal and to the medial surface of the midshaft tibia. Setting: University Hospital. Patients: Two male members of the research staff aged 40 and 54. Measurements: In vivo simultaneous peak-to-peak axial compression-tension strains during treadmill walking at 5 km/h while wearing standard army boots and Nike Air Max running shoes with and without either a non custom pre-fabricated orthotic with a three-quarter length thermocork module, a semirigid custom-made orthotic, with a three-quarter length polypropylene module made from nonweightbearing neutral subtalar position casts, a soft full length custom-made orthotic fabricated from 60 durometer plastazote, and a soft full length custom-made orthotic with a neutral heel post molded from three layers of polyurethane of different density (grade 80 upper layer, grade 60 middle layer and grade 80 lower layer). Results: Only the custom polyurethane composite orthotic was affective in lowering both peak-to-peak compression-tension 2nd metatarsal and tibia strains for both subjects when worn with army boots. When worn with Nike Air Max shoes the polyurethane composite orthotic lowered the peak-to-peak compression-tension 2nd metatarsal but not tibia strains. Limitations: Small subject number, each with a different foot type.Conclusions: The lower peak-to-peak compression-tension tibial and 2nd metatarsal strains while wearing army boots with custom polyurethane composite orthotics can explain the observed lower incidence of stress fractures among military recruits who used these orthotics.
... 15 However, design constraints result in increased stiffness and reduced shock absorption capacity which make these boots not suitable to support correct foot biomechanics. 16 Moreover, these critical features have been shown to reduce comfort and to increase fatigue, injury risk and energy cost, and may also result in higher incidence of dermatological disease and cutaneous lesions. 17,18 A way to reduce the incidence of overuse injuries of the foot is fitting footwear with plantar orthoses. ...
Article
Objective Soldiers’ lower limbs and feet are frequently affected by overload- and overuse-related injuries. In order to prevent or limit the incidence of these injuries, the use of foot orthoses is often recommended. The aim of this study is to assess the effects of shock-absorbing insoles on in-shoe plantar pressure magnitude and distribution in a group of professional infantry soldiers wearing military boots during standard indoor military training. Methods Twenty male professional soldiers of the Italian Army (age 35.1 ± 6.1 years; BMI 25.2 ± 2.3 kg/m2) were recruited for this study. Each subject underwent clinical examination to assess possible overuse-related diseases of the lower limb and trunk. Subjects with altered foot morphology according to the Foot Posture Index (FPI) were excluded from this study. Twelve subjects were considered eligible and therefore underwent an indoor training routine comprised of marching, running, jumping inside parallel bars and jumping from different heights. Soldiers repeated the training session twice wearing standard military boots along with two types of insoles: the standard prefabricated insole within the boots (STI), and a special shock-absorbing insole (SAI) featuring an elastic medial arch support. A 99-capacitive sensor insole system was used to record plantar pressure distribution in both feet. Analysis of in-shoe pressure parameters at rearfoot, midfoot and forefoot and in the total foot was performed via a custom-software application developed in MATLAB. Perceived foot comfort (VAS 0–15) was also assessed. Results Pressure parameters recorded during walking and running were considered suitable for statistical analysis. In the whole foot region, pressure parameters were 18–22% lower in military boots fitted with the SAI during walking and 14–18% lower during running. SAI resulted in better comfort (+25%) with respect to the prefabricated boot orthotics (median comfort: SAI = 15/15; STI = 12/15; p = 0.0039) both during walking and running. Conclusions Shock-absorbing insoles can be an effective solution when fitted inside military boots. The present functional evaluation shows that wearing a prefabricated shock-absorbing insole can provide a significant amelioration of perceived foot comfort and plantar pressure parameters. Further studies are now needed with a larger population and more demanding exercises.
... With respect to injury prevention, many physicians and non-medical practitioners indicate inflexible footwear as a possible reason for overuse injuries, like muscular inflammations [3][4][5]. Furthermore, it was shown that giving military recruits a new combat boot with a more flexible outer sole also lead to an increase in metatarsal stress fractures [6]. Therefore, Cikajlo and Matjačić [7] suggested that footwear sole stiffness has to preserve a certain level of hardness to prevent potential foot or ankle injuries. ...
Article
Full-text available
Since footwear flexibility impacts functional design factors, numerous studies have investigated footwear bending stiffness. However, the various methods used to measure footwear bending stiffness have some limitations. Hence, the scope of this study was to develop and quantify the reliability of a novel test set-up for measuring footwear bending stiffness. A test set-up consisting of a hydraulic testing machine, a bending apparatus and a fixation unit was created that fulfilled the requirements specified in the initial phase of the study. The test set-up was evaluated by testing 15 different boots in three series of measurements. Bending stiffness of the boots ranged from 0.61 ± 0.03 to 2.38 ± 0.08 Nm/°. Two-way analysis of variance test yielded that the test set-up enabled the reliable measurement of footwear bending stiffness. Relative measurement uncertainty ranged from 1.3 to 6.1 %.
... Stress calculation is a fundamental requirement when considering structural systems, not least in bone simulation, where the stresses within a sample provide vital information regarding fracture risk, injury rehabilitation and potential interaction with implants. Unfortunately, the heterogeneity of bone means stress cannot be accurately measured in vivo without invasive testing of the local material parameters [1]. Consequently, biomechanical simulation has been proposed to define the behaviour of bone. ...
Article
Full-text available
The accuracy of biomechanical simulation has been improved by using high-resolution computed tomography (CT) to define the geometry and material parameters. This technique has been used to assess numerous systems, including the mechanical properties of bone, fixation techniques post-fracture and the performance of bone microarchitecture. In this study, a semi-automated process for converting CT data into finite element (FE) models was used to model the mid-shaft (diaphysis) of porcine femoral samples under sub-maximal torsional and compressive load. Physical validation was undertaken to investigate if the all-important geometry and material property mapping functioned correctly. Porcine femoral specimens were imaged using contiguous helical CT, which was converted to FE models using ScanIP from Simpleware, Exeter, UK. The heterogeneous material properties were estimated using density–elasticity relationships proposed in literature for human bone samples. Laboratory testing performed favourably, with a linear strain response validating the use of the array of linear material models used in simulation. The simulation procedure also performed well. Linear regression and mean error calculation demonstrated accurate correlation between predicted (from simulation) and observed (measured within the laboratory) results that offered improvement over the accuracy within comparative testing for human samples. Using FE modelling on a patient-specific basis offers potential in a number of scenarios, including the determination of injury risk and design of protective equipment. The increased accessibility of animal samples allows large-scale fracture testing of complex loading mechanisms and the potential to consider younger animal samples (to investigate the behaviour of developing bone). Spiral fractures of long bones have been demonstrated to be an indicator of non-accidental injury in children. Combining the increased accuracy in torsional simulation in this study with younger sample testing may be employed to attempt to determine the causes of fracture from post fracture scans, aiding in the diagnosis of non-accidental injury.
... Frågeformuläret utformades efter genomgång av olika studier som påvisat att dessa faktorer kunde spela roll (8,9). Alla fick träffa en läkare på försvarshälsan för att genomgå en strukturerad intervju, där läkaren fyllde i frågeformuläret och vid behov ställde kompletterande frågor. ...
... [5][6][7][8] Stress fractures of the metatarsal bones are frequently reported overload injuries in long distance runners and are considered to be a result of a multi-factorial process. 9 Most studies are focused on the second and the fifth metatarsal bones because they are prone to both fracture and stress fracture in active sportsmen. 10,11 Furthermore all these studies were performed either in dry bones or cadavers. ...
Article
Full-text available
Objectives: Measurement of bone mineral density (BMD) is used frequently for assessment of bone strength and prediction of fracture risk in clinical settings. Among the bones in feet, fractures are seen often in second and third metatarsal of active sportsmen. This study was carried out to evaluate the reasons of increased risk of stress fractures in feet of active sportsmen by determining the BMD in overused regions. Methods: Two groups were examined in the present study. First group included males who were not sportsmen while the second and third groups were formed by professional male soccer and basketball players respectively. Areal bone density was measured by dual energy x-ray absorptiometry and the BMD values were calculated by using the rectangular region of interest in metatarsals. Results: The first metatarsal had the highest BMD in all groups (P<0.05). The fifth metatarsal had the second highest BMD value. Similarly subchondral measurement of the BMD revealed that the first tarsometatarsal joint were significantly denser than the first metatarsophalangeal joint (P<0.05). BMDs of all metatarsals in non-sportsmen group were significantly lower than BMDs of sportsmen groups and there were no noticable differences of BMD between soccer and basketball players. Conclusion: Because the degree of activity–induced enhancement of bone mineralization were similar in all metatarsals of active sportsmen, increased incidence of fractures in second and third metatarsals must be partly due to anatomical positioning of these bones. Hence appropriate shoe designs which have support for second and third metatarsals may decrease fracture incidence.
... The plantar pressure is a measurement accomplished in the patients' sole and its study has been used by several researchers as method of evaluation of treatments, as parameters for the development of products and of special inner soles [Cavanagh et al., 1994, Chang et al., 2002, Santos et al., 2001, Arndt et al., 2003. ...
Article
Full-text available
The measurement of the plantar pressure has been used in evaluations, treatments and products development. There are two basic techniques, the in-shoe and off-shoe (inside and outside of the shoe), and the measurement can be made through mechanical or optical sensors. The objective of this work was the development of a software to be used with the off-shoe technique, with images captured from to scanner (sensor optical). The images were digitalized with resolution of 100 dpi and with the scale of colors set to "grayscale." Afterwards they were processed, altering their colors and calculating to plantar pressure values. The post-processed images revealed the areas with high plantar pressure, providing aid to physician, physiotherapists and other professionals to evaluate, diagnosis and treat diseases and deformities of the feet.
... Cushioned shoes and/or insoles may provide assistance in dissipating impact forces during ADLs in athletes with a rearfoot or leg BSI, 41,81 whereas stiff-soled shoes may be considered to reduce bending forces and symptoms in athletes with a BSI in the midfoot or forefoot. 5 Walking should be minimized to that essential to perform ADLs and limited to a normal gait pattern. If a normal gait pattern cannot be used or symptoms are produced either during or after walking, partial weight bearing using assistive gait devices (eg, double or single crutch, cane) should be considered. ...
Article
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Synopsis: Bone stress injury (BSI) represents the inability of bone to withstand repetitive loading, which results in structural fatigue and localized bone pain and tenderness. A BSI occurs along a pathology continuum that begins with a stress reaction, which can progress to a stress fracture and, ultimately, a complete bone fracture. Bone stress injuries are a source of concern in long-distance runners, not only because of their frequency and the morbidity they cause but also because of their tendency to recur. While most BSIs readily heal following a period of modified loading and a progressive return to running activities, the high recurrence rate of BSIs signals a need to address their underlying causative factors. A BSI results from disruption of the homeostasis between microdamage formation and its removal. Microdamage accumulation and subsequent risk for development of a BSI are related both to the load applied to a bone and to the ability of the bone to resist load. The former is more amenable to intervention and may be modified by interventions aimed at training-program design, reducing impact-related forces (eg, instructing an athlete to run "softer" or with a higher stride rate), and increasing the strength and/or endurance of local musculature (eg, strengthening the calf for tibial BSIs and the foot intrinsics for BSIs of the metatarsals). Similarly, malalignments and abnormal movement patterns should be explored and addressed. The current commentary discusses management and prevention of BSIs in runners. In doing so, information is provided on the pathophysiology, epidemiology, risk factors, clinical diagnosis, and classification of BSIs. Level of evidence: Therapy, level 5.
... 82 Worn running shoes may increase the risk for stress fracture because of decreased shock absorption, 56 similar to combat boots. 5 A meta-analysis of randomized controlled trials on insoles suggests a reduction in stress fractures in the military population. 111 ...
Article
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Context: Stress fractures are common injuries in athletes, often difficult to diagnose. A stress fracture is a fatigue-induced fracture of bone caused by repeated applications of stress over time. Evidence Acquisition: PubMed articles published from 1974 to January 2012. Results: Intrinsic and extrinsic factors may predict the risk of stress fractures in athletes, including bone health, training, nutrition, and biomechanical factors. Based on their location, stress fractures may be categorized as low- or high-risk, depending on the likelihood of the injury developing into a complete fracture. Treatment for these injuries varies substantially and must account for the risk level of the fractured bone, the stage of fracture development, and the needs of the patient. High-risk fractures include the anterior tibia, lateral femoral neck, patella, medial malleolus, and femoral head. Low-risk fractures include the posteromedial tibia, fibula, medial femoral shaft, and pelvis. Magnetic resonance is the imaging test of choice for diagnosis. Conclusions: These injuries can lead to substantial lost time from participation. Treatment will vary by fracture location, but most stress fractures will heal with rest and modified weightbearing. Some may require more aggressive intervention, such as prolonged nonweightbearing movement or surgery. Contributing factors should also be addressed prior to return to sports.
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For many years, U.S. Army soldiers performed physical training (PT) in a modified duty uniform and combat boots. The belief that PT in combat boots was associated with injuries lead to the introduction of running shoes for PT in 1982. A historical comparison was conducted examining injuries before and after the change to running shoes in Basic Combat Training (BCT). Searches in literature databases and other sources identified 16 studies with quantitative data on injury incidence during 8-week BCT cycles. Employing studies with similar injury definitions (n = 12), injury incidence was compared in the boot and running shoe periods using meta-analyses, χ(2) statistics, and risk ratios (RRs) with 95% confidence intervals (95% CIs). The boot and shoe periods demonstrated little difference in overall injury incidence (men: RR[boot/shoes] = 1.04, 95% CI = 0.91-1.18, p = 0.50; women: RR = 0.94, 95% CI = 0.85-1.05, p = 0.27) or in lower extremity injury incidence (men: RR[boot/shoes] = 0.91, 95% CI = 0.64-1.30, p = 0.66; women: RR = 1.06, 95% CI = 0.89-1.27, p = 0.51). These analyses provided little support for a reduction in injury risk after the switch from boots to running shoes for PT in BCT. A large randomized, prospective cohort study should be conducted to determine if injury rates are different when PT is conducted in running shoes versus boots. Reprint & Copyright © 2015 Association of Military Surgeons of the U.S.
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Background: Third metatarsal stress fractures are relatively common during Royal Marines recruit training; however, their aetiology is poorly understood. Mathematical modelling of the third metatarsal may aid in understanding risk factors for stress fracture, particularly if the influence of footwear on peak bending stresses can be determined. This study built on previous models of metatarsal bending stress by integrating individual metatarsal geometry and gait data. Methods: Data from five males with size 11 (UK) feet were acquired. MRI images were digitised to determine cross-sectional bone parameters. Gait variables included vertical ground reaction forces, plantar pressure and foot orientation. The magnitude and location of peak bending stresses were calculated for barefoot running, before standard issue combat boots and trainers were compared. Findings: Estimated peak compressive, tensile and torsional stresses were greater in combat assault boots than in trainers (p < 0.05) with medium effect sizes but wide confidence intervals. However, differences in bone geometry between individuals had a much greater influence on estimated peak stresses. Interpretation: Results suggest that bone geometry has a greater influence on third metatarsal stress fracture risk than footwear. Future bone stress simulations should account for bone geometry. Further development of the model in a variety of participants should proceed to verify these suggestions.
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This descriptive diagnosis study had the objective to evaluate the functional characteristics and the use of the boots worn by the police officers while they are on duty patrol walking on Florianópolis streets, as well as the influency of the boots in this activity. Selected by not-probabilistic sampling in a casual-systematic way, 234 police officers volunteered to take part in this study. The instrument used was a questionnaire assorted with clarity level of 0.93, validity of 0.85 and reliability of 0.95. According to the results, most police officers have only a pair of boots, which were worn on average 11 hours daily. To the boot usage was attributed the incidence of foot injuries such as callosity, chilblain, embedded nails and blisters. For these police officers the discomforts (overheating, pain and humidity on the feet as well as pain in the body) caused by the boot interfered in their work routine taking them to classified their shoes as inappropriate, following the criteria of comfort, safety and durability. Therefore, it was concluded that the boots seemed not to be the ideal shoes in terms of comfort and job performance, because they interfered in their daily routine, causing functional and structural adaptations in the human body during the performance of motor tasks.
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Stress fractures of the lower extremity are common in military and running populations. Research on the effectiveness of orthotics in modifying bone strain is limited. Our hypothesis was that custom and semi-custom foot orthotics would equally decrease bone strain of the second metatarsal. Eight cadaver specimens were cast for two types of orthotics, a custom and semi-custom device, using neutral plaster casts. Cadaver specimens, mounted to a dynamic gait simulator, walked over a force platform while force and bone strain data were collected. Peak bone strains, strain rates and tendon forces during the stance phase for each condition were analyzed using repeated measures analysis of variance and effect sizes. Condition effects were present for tension strain, shear strain, compression rate and shear rate. Specifically, custom orthotics significantly decreased the aforementioned bone strains and strain rates (< or = 0.01 for all) and the semi-custom orthotic decreased tension strains and shear strain rates (p = 0.05 and 0.03, respectively). The effect of custom and semi-custom devices only differed significantly for compression and shear strain (p= 0.04 and 0.02, respectively) with custom orthotics having a greater effect. Both custom and semi-custom orthotics modified the second metatarsal bone strain and strain rate. The use of custom orthotics during simulated walking decreased second metatarsal bone strains and strain rates more effectively than semi-custom orthotics. Orthotics may minimize the strain magnitudes and rates of the second metatarsal in walking and therefore are a feasible treatment option for the treatment and prevention of stress injury to the second metatarsal.
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Multisegment foot models provide researchers more-detailed information regarding foot mechanics compared with single rigid body foot models. Previous work has shown that walking speed significantly affects sagittal plane ankle motion. It is important to distinguish changes in intersegment foot mechanics following treatment that are due to clinical intervention versus those due to walking speed alone. Foot and ankle kinematics were collected on 24 adults walking at 5 speeds. Significant differences were seen at the ankle using a single rigid body foot model, as well as at the hindfoot and forefoot using a multisegment foot model, with all motions exhibiting a shift toward plantar flexion and decreased stance time with increasing speed. When evaluating foot mechanics using a multisegment foot model across groups or conducting intrasubject comparison over time/treatments, it is imperative that walking speed be accounted for or controlled.
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Metatarsal stress fracture is a common injury observed in athletes and military personnel. Mechanical fatigue is believed to play an important role in the etiology of stress fracture, which is highly dependent on the resulting bone strain from the applied load. The purpose of this study was to validate a subject-specific finite element (FE) modeling routine for bone strain prediction in the human metatarsal. Strain gauge measurements were performed on 33 metatarsals from seven human cadaveric feet subject to cantilever bending, and subject-specific FE models were generated from computed tomography images. Material properties for the FE models were assigned using a published density-modulus relationship as well as density-modulus relationships developed from optimization techniques. The optimized relationships were developed with a ‘training set’ of metatarsals (n=17) and cross-validated with a ‘test set’ (n=16). The published and optimized density elasticity equations provided FE-predicted strains that were highly correlated with experimental measurements for both the training (r²≥0.95) and test (r²≥0.94) sets; however, the optimized equations reduced the maximum error by 10% to 20% relative to the published equation, and resulted in an X=Y type of relationship between experimental measurements and FE predictions. Using a separate optimized density-modulus equation for trabecular and cortical bone did not improve strain predictions when compared to a single equation that spanned the entire bone density range. We believe that the FE models with optimized material property assignment have a level of accuracy necessary to investigate potential interventions to minimize metatarsal strain in an effort to prevent the occurrence of stress fracture.
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Long-distance road marching including load carriage results in substantial biomechanical loading of the lower extremity of soldiers and is considered a risk factor for the development of lower extremity injury in military personnel. The aim of our study was to quantify changes in biomechanical loading and foot shape occuring after a typical marching task, to compare these data to similar effects already known from endurance running tasks, and to derive recommendations for the design of military footwear. Gait and foot shape of 59 soldiers were assessed using plantar pressure distribution and 3 D foot scan measurements pre and post a 25 km road march carrying an 18 kg backpack. Plantar pressure variables indicated a load shift from toes to metatarsal heads II–V after the march, however, none of the foot measures showed any relevant changes. Results are partially consistent with existing findings and point to the need for military footwear design to address the load increase in the area of the lateral metatarsal heads to contribute to injury prevention.
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Firefighters have reported their protective boots to be bulky and ill-fitting, which they believe restrict the lower body movement on the unpredictable fireground. This study used 3D foot scanning to compare the shape of firefighters' feet to the general population, the shape of female firefighters’ feet to males, and the impact of the heavy fire gear on foot shape. The results found the foot breadth of firefighters was larger than the general population and the feet of female firefighters were slimmer than males. Furthermore, it revealed that the feet of firefighters became longer, wider, and flatter when bearing the weight of fire gear. Protective boots should be designed based on the foot shape and dimensions of the actual population, with consideration of sex differences and the impact of weight-bearing for their safety.
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A bone stress injury (BSI) means that the bones cannot tolerate repeated mechanical loads, resulting in structural fatigue and local bone pain. A delay in BSI diagnosis can lead to more serious injuries, such as stress fractures that require longer treatment periods. Therefore, early detection of BSI is an essential part of management. Risk factors for BSI development include biological and biomechanical factors. Medical history and physical examination are the basics for a BSI diagnosis, and magnetic resonance imaging is helpful for confirming and grading. In this paper, the authors review the overall content of BSI and stress fractures which are common in runners. Through this review, we hope that interest in stress fractures will be raised in Korea and that active researches will be conducted.
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Insulin-like growth factor 1 (IGF-I) is a robust metabolic and anabolic biomarker that has been demonstrated to be reflective of military training-induced body composition changes and influenced by initial aerobic fitness level. Greater mechanistic insight into the IGF-I response to physical training can potentially be gleaned by also examining other regulatory factors that influence IGF-I biological activity (i.e., insulin-like growth factor-binding proteins [IGFBPs] and inflammatory cytokine responses). The purpose of this study was to assess the influence of sex and initial fitness level on the IGF-I and inflammatory cytokine response to gender-integrated Israeli Defense Forces (IDF) basic combat training (BCT). Recruits (29 men, 19.1 ± 1.3 years; 93 women, 18.8 ± 0.6 years) were recruited from a 4-month gender-integrated BCT of the IDF. Blood was drawn and assayed for total IGF-I, free IGF-I, IGFBPs 1-6, tumor necrosis factor alpha (TNF-α), interleukin 6, and interleukin 1 beta. Body composition was determined via a 4-site skinfold (biceps, triceps, suprailiac, and subscapular) equation. Physical performance was assessed via a maximum volume of oxygen consumption (V[Combining Dot Above]O₂max) test using a treadmill protocol. All measures were obtained pre- and posttraining. A 2-way (sex × time) analysis of variance was used to test for statistical differences (p ≤ 0.05). Additionally, subjects were further partitioned (men and women separately) by tertiles of initial V[Combining Dot Above]O₂max to assess the influence of initial fitness level on the IGF-I system and inflammatory cytokine responses to physical training. Pearson product moment correlational analysis was also used to examine relationships between percent changes in blood measures and physical performance and body composition changes. All data are presented as mean ± SE. Time effects were observed only for total IGF-I, IGFBP-2, TNF-α, V[Combining Dot Above]O₂max, fat-free mass, and fat mass. The only significant (p ≤ 0.05) correlations observed for percent changes were in men between total IGF-I and V[Combining Dot Above]O₂max (r = 0.49) and body mass (r = -0.42) During gender-integrated Israeli Army BCT, men and women generally respond in a similar fashion with regard to blood measures (IGF-I system and inflammatory cytokines) and V[Combining Dot Above]O₂max. Initial fitness level only influenced the IGF-I response to training in women. Although the training-induced changes in total IGF-I (increase), IGFBP-2 (decrease), and TNF-α (decrease) are all indicative of an enhanced circulating anabolic milieu, only total IGF-I for the men was correlated with body composition and fitness improvements.
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Abstract The metatarsal phalangeal joint (MPJ) and its crossing toe flexor muscles (TFM) represent the link between the large energy generating leg extensor muscles and the ground. The purpose of this study was to examine the functional adaptability of TFM to increased mechanical stimuli and the effects on walking, running and jumping performance. Fifteen men performed a heavy resistance TFM strength training with 90% of the maximal voluntary isometric contraction (MVIC) for 7 weeks (560 contractions) for the left and right foot. Maximal MPJ and ankle plantar flexion moments during MVICs were measured in dynamometers before and after the intervention. Motion analyses (inverse dynamics) were performed during barefoot walking, running, and vertical and horizontal jumping. Athletic performance was determined by measuring jump height and distance. Left (0.21 to 0.38 Nm · kg(-1); P < 0.001) and right (0.24 to 0.40 Nm · kg(-1); P < 0.001) MPJ plantar flexion moments in the dynamometer, external MPJ dorsiflexion moments (0.69 to 0.75 Nm · kg(-1); P = 0.012) and jump distance (2.25 to 2.31 m; P = 0.006) in horizontal jumping increased significantly. TFM responded highly to increased loading within a few weeks. The increased force potential made a contribution to an athlete's performance enhancement.
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Lower limb injuries are a continual and serious issue for military personnel. Such injuries have been associated with the requirement to train in military boots (MBs) and might be offset with commercial insoles. In this study, ground reaction forces were measured in seven male participants wearing running shoes (RS), MBs commonly used by Cypriot and Greek Army personnel, and the MBs with two types of shock-absorbing insole. The participants performed 4-min trials at walking pace (5 km·h-1) and running pace (10 km·h-1) at a 5% gradient on a treadmill under all four shod conditions. The treadmill incorporated two force plates under its belt, which provided measurements of key kinetic variables. During walking, RS showed significantly lower values for impact peak force (p < 0.01), maximum force (p < 0.05), and push-off rate (p < 0.05) compared with other conditions, although no significant differences were found during running. Although the RS were rated significantly more comfortable than any other condition, neither insole made the MBs more comfortable to wear. With little evidence to support wholesale adoption of insoles in MBs, their use by military personnel can only be recommended on a case-by-case basis.
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In a prospective study of 295 male Israeli military recruits a 31% incidence of stress fractures was found. Eighty per cent of the fractures were in the tibial or femoral shaft, while only 8% occurred in the tarsus and metatarsus. Sixty-nine per cent of the femoral stress fractures were asymptomatic, but only 8% of those in the tibia. Even asymptomatic stress fractures do, however, need to be treated. Possible explanations for the unusually high incidence of stress fractures in this study are discussed.
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Uniaxial fatigue tests were conducted of devitalized cortical bone specimens machined from human femora. Specimens were tested at strain ranges from 0.005 to 0.010 under physiologic loading rates. The influence of compressive, zero, and tensile mean strains on fatigue life and on the stress/strain histories during fatigue were examined. Results showed that bone fatigue is a gradual damage process accompanied by a progressive increase in hysteresis and a loss of bone stiffness. The total number of cycles to fatigue failure was influenced only by the total strain range and was not affected by mean strain. Bone was shown to have extremely poor fatigue resistance. Fully reversed cyclic loading to one half of the yield strain caused fatigue fracture in 1000 cycles. Biological implications. The bone regions which experience the highest strain ranges in vivo generally have a compressive mean strain. The results of this study indicate that mechanical fatigue damage accumulates more rapidly in these "compressive" areas than in "tensile" areas of bone.
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A total of 693 female U.S. Marine Corps recruits were studied with anthropometry and dual-energy X-ray absorptiometry (DXA) scans of the midthigh and distal third of the lower leg prior to a 12 week physical training program. In this group, 37 incident stress fracture cases were radiologically confirmed. Female data were compared with male data from an earlier study of 626 Marine recruits extended with additional cases for a total of 38 stress fracture cases. Using DXA data, bone structural geometry and cortical dimensions were derived at scan locations and muscle cross-sectional area was computed at the midthigh. Measurements were compared within gender between pooled fracture cases and controls after excluding subjects diagnosed with shin splints. In both genders, fracture cases were less physically fit, and had smaller thigh muscles compared with controls. After correction for height and weight, section moduli (Z) and bone strength indices (Z/bone length) of the femur and tibia were significantly smaller in fracture cases of both genders, but patterns differed. Female cases had thinner cortices and lower areal bone mineral density (BMD), whereas male cases had externally narrower bones but similar cortical thicknesses and areal BMDs compared with controls. In both genders, differences in fitness, muscle, and bone parameters suggest poor skeletal adaptation in fracture cases due to inadequate physical conditioning prior to training. To determine whether bone and muscle strength parameters differed between genders, all data were pooled and adjusted for height and weight. In both the tibia and femur, men had significantly larger section moduli and bone strength indices than women, although women had higher tibia but lower femur areal BMDs. Female bones, on average, were narrower and had thinner cortices (not significant in the femur, p = 0.07). Unlike the bone geometry differences, thigh muscle cross-sectional areas were virtually identical to those of the men, suggesting that the muscles of the women were not relatively weaker.
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OBJECTIVE: A study was conducted to investigate the effects of fatigue on the ability of human musculoskeletal system to deal with the onslaught of the heel strike initiated shock waves. DESIGN: Running on a treadmill at the anaerobic threshold level for 30 min was used to acquire the experimental data on the foot strike initiated shock waves. BACKGROUND: Muscles act to lower the bending stress on bone and to attenuate the dynamic load on human musculoskeletal system. Fatigue may diminish their ability to dissipate and attenuate loading on the system. Knowledge of the effects of fatigue on the ability of the human musculoskeletal system to attenuate the shock waves may help in design of the training procedures and exercises. METHODS: Twenty-two young healthy males participated in this study. Each one was running on the treadmill at the speed corresponding to his anaerobic threshold for 30 min. The heel strike induced shock waves were recorded every 5 min on the tibial tuberosity and sacrum. The data obtained were analyzed in both temporal and frequency domains. RESULTS: The results reveal significant increase in the dynamic loading experienced by the human musculoskeletal system with fatigue. This may be attributed to the inability of the fatigued system to provide an efficient way to attenuate shock waves. CONCLUSIONS: The analysis of the recorded signals suggests that fatigue contributes to the reduction of the human musculoskeletal system's capacity to attenuate and dissipate those shock waves. This capacity appears to be a function not only of the fatigue level, but also of the vertical location along the skeleton. RELEVANCE: Fatigue during running may affect the ability of the human musculoskeletal system to attenuate and dissipate the heel strike induced shock waves. The study of the fatigue effect on shock wave attenuation provides information that may benefit the runner.
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Since stress fractures occur universally and render the patient at risk for serious injury if they are undertreated, observation of good treatment principles is essential. If these principles are adhered to, the physician can usually treat stress fractures without major interruption of the recreational or competitive athlete’s sport style.
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In-shoe plantar pressure measurement has the potential to play a crucial role in the screening, treatment and behavior modification of patients who are at risk of, or are experiencing a variety of foot problems. In this article we review the instrumentation, methodology, applications, and rationale for in-shoe plantar pressure measurement. Possible new applications in the future are also discussed. In-shoe techniques are advantageous compared to the more traditional platform devices because they permit the most important interface, that between the foot and shoe, to be monitored and they allow for increased versatility of measurement for the calculation of more robust statistical estimates. Both discrete transducers and matrix systems have been developed; each approach has its advantages and disadvantages but, in general, matrix systems are preferable. Although there are still device limitations which must be overcome the technique of in-shoe measurement has opened the door to a whole new realm of pressure studies both in research and clinical practice.
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The purpose of this investigation was to identify changes in loading characteristics of the foot associated with fatigue during running. Nineteen healthy subjects ranging from 20 to 30 yr (mean = 22.3, SD = 2.4) were equipped with the Pedar in-shoe measurement system (Novel GmbH) for the assessment of plantar loading. After acclimation to the treadmill, subjects were progressed through the Ohio State protocol for exercise testing until fatigue was reported using Borg's RPE scale. Six right footsteps were recorded at 150 Hz for each subject's comfortable running pace under normal and fatigued conditions. A series of repeated measures multiple analysis of variance was performed for all dependent variables analyzed in this study including peak force (PF), force-time integral (FTI), peak pressure (PP), and pressure-time integral (PTI) for all regions of the plantar surface. Decreased step time, significantly smaller values under the heel for PP, PF, FTI, CT, and PTI, and trends toward increased medial forefoot loading were identified while subjects were running under fatigued conditions (alpha < 0.05). These results suggest that subjects change running technique and plantar surface loading characteristics in response to fatigued conditions through increased cadence, decreased loading of the heel, and increased medial forefoot loading.
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(1) Around 40% of body weight is imposed on the toes in the final stages of forefoot contact. Most of this is imposed on the great toe. Toe loads are counteracted by tension in the toe flexor tendons and tendon sheaths. These forces react against the m.t.p. joints to produce a joint force around 600 N in the first joint, and around 100 N in the fifth. There was considerable variability in the distribution of load on the forefoot between individuals, resulting in a spread of these calculated forces. (2) The metatarsals carry a load which is due primarily to the ground reaction during the first half of forefoot contact time, and due primarily to the m.t.p. joint force in the second half of this contact time. The ground reaction force is near to vertical (only the vertical component was considered here) but the joint force has a large horizontal component. These forces together produce a large axial force in the metatarsals in walking, but also sufficient non-axial load to give a bending moment in the dorsiflexion direction. This moment has to be resisted by the short plantar ligaments which tie the metatarsal to the tarsus. (3) In most of the normal feet studied, the forces in the rays of the forefoot were ranked in sequences so that the first ray carried the highest loads and the fifth carried the smallest loads. (4) The foot can be considered partly as an arch structure (loaded through the talus, the heel and Achilles tendon, and through the forefoot) and partly as a beam or lever. There are 'arch supporting' structures (toe flexor tendons and the plantar aponeurosis) which reduce the bending moment in the arch by about 10% compared with what it would be in the absence of the function. These also increase the axial loads in the metatarsals and the joint reactions. The remaining bending moment at the base of the metatarsal is resisted by closely applied ligaments. (5) Disorders of the foot which reduce the load-bearing function of the toes result in less load in the m.t.p. joints. However, they also give greater bending moments in the metatarsal bones, and produce greater stresses at the attachments of the metatarsals to the tarsus. This may be a common reason for pain and march fractures in the metatarsals, and for progressive changes and deformities in the midfoot joints.
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A model of metatarsal mechanics has been proposed as a link between the high incidence of second and third metatarsal stress fractures and the large stresses measured beneath the second and third metatarsal heads during distance running. Eight discrete piezoelectric vertical stress transducers were used to record the forefoot stresses of 21 male distance runners. Based upon load bearing area estimates derived from footprints, plantar forces were estimated. Highest force was estimated beneath the second and first metatarsal head (341.1 N and 279.1 N, respectively). Considering the toe as a hinged cantilever and the metatarsal as a proximally attached rigid cantilever allowed estimation of metatarsal midshaft bending strain, shear, and axial forces. Bending strain was estimated to be greatest in the second metatarsal (6662 mu epsilon), a value 6.9 times greater than estimated first metatarsal strain. Predicted third, fourth, and fifth metatarsal strains ranged between 4832 and 5241 mu epsilon. Shear force estimates were also greatest in the second metatarsal (203.0 N). Axial forces were highest in the first metatarsal (593.2 N) due to large hallux forces in relationship to the remaining toes. Although a first order model, these data highlight the structural demands placed upon the second metatarsal, a location of high metatarsal stress fracture incidence during distance running.
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We analyzed cases of 320 athletes with bone scan-positive stress fractures (M = 145, F = 175) seen over 3.5 years and assessed the results of conservative management. The most common bone injured was the tibia (49.1%), followed by the tarsals (25.3%), metatarsals (8.8%), femur (7.2%), fibula (6.6%), pelvis (1.6%), sesamoids (0.9%), and spine (0.6%). Stress fractures were bilateral in 16.6% of cases. A significant age difference among the sites was found, with femoral and tarsal stress fractures occurring in the oldest, and fibular and tibial stress fractures in the youngest. Running was the most common sport at the time of injury but there was no significant difference in weekly running mileage and affected sites. A history of trauma was significantly more common in the tarsal bones. The average time to diagnosis was 13.4 weeks (range, 1 to 78) and the average time to recovery was 12.8 weeks (range, 2 to 96). Tarsal stress fractures took the longest time to diagnose and recover. Varus alignment was found frequently, but there was no significant difference among the fracture sites, and varus alignment did not affect time to diagnosis or recovery. Radiographs were taken in 43.4% of cases at the time of presentation but were abnormal in only 9.8%. A group of bone scan-positive stress fractures of the tibia, fibula, and metatarsals (N = 206) was compared to a group of clinically diagnosed stress fractures of the same bone groups (N = 180), and no significant differences were found. Patterns of stress fractures in athletes are different from those found in military recruits. Using bone scan for diagnosis indicates that tarsal stress fractures are much more common than previously realized. Time to diagnosis and recovery is site-dependent. Technetium99 bone scan is the single most useful diagnostic aid. Conservative treatment of stress fractures in athletes is satisfactory in the majority of cases.
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As the running community as well as the primary care medical community become more sophisticated in their knowledge of and treatment of repetitive stress injuries, only the more difficult problems will arrive at the orthopedist's office. As a result, injuries such as stress fracture will constitute a larger percentage of running and other repetitive stress injuries. The universal occurrence of stress fracture and its possible at-risk nature for serious injury if undertreated underscores the need to observe good treatment principles. With these principles in mind, the physician can usually treat stress fracture without major interruption of the recreational or competitive athlete's sport style.
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Metatarsal stress fractures occur in military recruits after long marches and in athletes after episodes of overtraining involving running or jumping. It has been demonstrated that contraction of the plantar flexors of the toes helps to counteract the moments placed on the metatarsals by body weight. It is possible that physiological fatigue due to strenuous or repetitive exercise reduces the rate and force of contraction of the plantar flexors, thereby increasing metatarsal strain per cycle, and that this mechanism is the primary cause of stress fractures of these bones. To test the hypothesis that fatigue of the plantar flexors causes increased metatarsal loading, thereby predisposing these bones to stress fracture, we measured metatarsal strains in nine fresh cadaveric feet with use of an apparatus that simulated physiological loading due to body weight as well as contraction of the plantar flexors. Each foot was loaded to 750 newtons of ground-reaction force by simulated contraction of the triceps surae, and strains were recorded in the mid-part of the shaft of the second metatarsal. Tests were repeated with use of simulated activity of different combinations of the flexor digitorum longus, flexor hallucis longus, peroneus brevis, peroneus longus, and tibialis posterior muscles. In situ bending moments and axial loads subsequently were derived for each configuration. Dorsal strain was significantly reduced by simulated contraction of the flexor hallucis longus. Plantar-dorsal bending was significantly reduced by simulated contraction of the flexor digitorum longus.
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Fatigue damage accumulation has been demonstrated in living bone and postulated as a stimulus to the bone modeling and remodeling response. Mechanical property degradation is one manifestation of fatigue damage accumulation. This study examines changes in secant modulus and cyclic energy dissipation behavior during axial load-controlled fatigue loading of cortical bone specimens. The findings suggest that secant modulus degradation and cyclic energy dissipation are greatly increased at loading levels above critical damage strain thresholds of 2500 and 4000 mu epsilon in tensile and compressive fatigue, respectively. Tensile and compressive fatigue loading also caused different forms of modulus degradation at loading levels above these thresholds. Bone behaves as a linear viscoelastic material below these thresholds, even after prior property degradation at higher loading levels. Cyclic energy dissipation was proportional to the 2.1 power of the applied effective strain range for all loadings below 2500 mu epsilon. Above 2500 mu epsilon, tensile fatigue loading caused cyclic energy dissipation proportional to the 5.8 power of the applied effective strain range. Compressive fatigue loading dissipated cyclic energy proportional to the 4.9 power of applied effective strain range over 4000 mu epsilon. Lifetime energy dissipation over all fatigue tests to fracture at a single loading level was well fitted by the same power law in the number of cycles to failure raised to the 0.6 power. Loading levels of 2500 mu epsilon in tension and 4000 mu epsilon in compression are within the ranges observed in living animals, and thus these phenomena may play a role in initiating the remodeling response in live bone tissue.
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Despite the fact that a number of studies have investigated lower extremity energy generation during locomotion, the influence of the metatarsophalangeal (MP) joint remained unknown. The purpose of this study was to determine the relative contribution of the MP joint to the total mechanical energy in running and sprinting. A sagittal plane analysis was performed on data collected from 10 trained male athletes (five runners and five sprinters). The MP moment was assumed to be negligible until the ground reaction force acted distal to the joint. During running, once the ground reaction force crossed the MP joint, the MP moment was plantarflexor for the remainder of ground contact with average peak values of 59.9 Nm. The MP joint moment was plantarflexor throughout the stance phase for sprinting with average peak values of 112.4 Nm. Since the MP joint was dorsiflexing throughout the majority of the stance phase the joint absorbed large amounts of energy, on average 20.9 J during running and 47.8 J during sprinting. A lack of plantarflexion of the MP joint resulted in a lack of energy generation during take-off. Thus, the energy that was absorbed at the joint was dissipated in the shoe and foot structures.
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In a prospective study of stress fractures the hypothesis that training with custom made biomechanical shoe orthoses could lessen the incidence of stress fractures in infantry recruits was tested. Recruits were assigned randomly to groups and given soft biomechanical orthoses or semirigid biomechanical orthoses and compared with a control group that did not train in biomechanical orthoses. All recruits wore infantry boots with soles designed like those of basketball shoes. Recruits were examined biweekly during 14 weeks of basic training. The incidence of stress fractures was 15.7% for the recruits with the semirigid biomechanical orthoses, 10.7% for the recruits with the soft biomechanical orthoses, and 27% for the control group. The soft biomechanical orthoses were tolerated better by the recruits than were the semirigid devices. Among trainees at high risk for stress fractures, prophylactic use of custom made biomechanical orthoses may be warranted.
Article
Stress fractures of the metatarsals are common overuse injuries in athletes and military cadets, yet their etiology remains unclear. In vitro, high bone strains have been associated with the accumulation of microdamage and shortened fatigue life. It is therefore postulated that stress fractures in vivo are caused by elevated strains, which lead to the accumulation of excessive damage. We used a cadaver model to test the hypothesis that strains in the metatarsals increase with simulated muscle fatigue and plantar fasciotomy. A dynamic gait simulator was used to load fifteen cadaveric feet during the entire stance phase of gait under conditions simulating normal walking, walking with fatigue of the auxiliary plantar flexors, and walking after a plantar fasciotomy. Strains were measured, with use of axial strain-gauges, in the dorsal, medial, and lateral aspects of the diaphysis of the second and fifth metatarsals as well as in the proximal metaphysis of the fifth metatarsal. When the feet were loaded under normal walking conditions, the mean peak strain in the dorsal aspect of the second metatarsal (-1897 microstrain) was more than twice that in the medial aspect of the fifth metatarsal (-908 microstrain). Simulated muscle fatigue significantly increased peak strain in the second metatarsal and decreased peak strain in the fifth metatarsal. Release of the plantar fascia caused significant alterations in strain in both metatarsal bones; these alterations were greater than those caused by muscle fatigue. After the plantar fasciotomy, the mean peak strain in the dorsal aspect of the second metatarsal (-3797 microstrain) was twice that under normal walking conditions. The peak axial strain in the diaphysis of the second metatarsal is significantly (p < 0.0001) higher than that in the diaphysis of the fifth metatarsal during normal gait. The plantar fascia and the auxiliary plantar flexors are important for maintaining normal strains in the metatarsals during gait.
Article
Chicken tibiae were chosen as a model for human second metatarsals. Local surface bone deformation in a 4-point bending configuration was measured in vitro by both strain gauge instrumented staples and strain gauges bonded to the bone's cortical surface. A series of staple bridge dimensions (0.5, 0.6, 0.8 and 1.0 mm) was compared to test for staple influence on bone characteristics and greatest measurement validity and reliability. Thicker staple inhibition of bone deformation was the greatest but differences to thinner staples were not statistically significant (p > 0.05). All staples except 0.5 mm had maximum deviations from linearity less than 1%. The 1.0 mm staple had an R2 value of 0.992 +/- 0.006 plotted against the 4-point bending input force and 0.994 +/- 0.002 plotted against the surface strain gauge signal. The mean intraclass correlation coefficients (ICC) calculated with four input forces (30, 60, 90 and 120 N) and for loading and unloading conditions for the 0.5, 0.6, 0.8 and 1.0 mm staples were 0.75, 0.83, 0.87 and 0.92, respectively. Finally, the differences in slope of the staple strain gauge signal plotted against surface strain gauge signal between input force loading and unloading conditions (0.32), and between input compression and tension conditions (0.79) was least for the 1.0 mm staple which also resulted in the lowest standard deviations. These results suggested the appropriateness of the 1.0 mm staple for in vivo application.
Article
A study was undertaken to determine if placing shock absorbing insoles in the boots of Royal Marine recruits would attenuate the peak pressure at the foot-boot interface, when marching at 4.8 kph carrying a 32 kg (70 lb) Bergen and running at 12.8 kph in loose order plus webbing weighing 10 kg (22 lb). Four types of insoles were assessed: viscoelastic polymetric insole (Cambion(R)) polymetric foam insole (PPT(R)) Saran insole (military issue) and Sorbothane(R). There was a fifth control condition in which no insoles were used. Pressure measurements during heel strike and forefoot loading were taken using Paratec equipment with pressure measuring insoles placed in the boots. Data were obtained from eleven subjects and indicated that all the insoles significantly (P<0.05) attenuated the peak pressures generated during heel strike and forefoot loading. The performance of the four insoles in terms of peak pressure attenuation ranked in order with the best first were: Sorbothane Cambion PPT Saran. The Sorbothane insole was substantially and significantly (P<0.05) better than the other insoles in terms of attenuating peak pressures during heel strike. During running, mean peak pressure at heel strike was 494 kPa in the control condition, this was reduced to 377 kPa when wearing Sorbothane insoles (a reduction of 27%). When marching the Sorbothane insoles reduced the mean peak pressure at heel strike from 395 kPa (control) to 303 kPa (23% reduction). During forefoot loading the peak pressure attenuation of all four insoles was similar, although on average the Sorbothane insole performed slightly better than the others and was significantly different (P<0. 05) to the Cambion insole. Mean peak forefoot loading pressure in the control condition when running was 413 kPa, with the Sorbothane insole it was 367 kPa, during marching the respective mean peak pressures were 397 and 323 kPa. It is concluded that of the four types of insoles assessed the Sorbothane insoles attenuated the greatest amounts of the peak pressure generated at heel strike and during forefoot loading when running and marching wearing military boots.
Article
Stress reaction in bone, which may proceed to a fracture, is a significant problem in military recruits and in athletes, particularly long distance runners. To evaluate the evidence from controlled trials of treatments and programmes for prevention or management of lower limb stress fractures and stress reactions of bone in active young adults. We searched the Cochrane Musculoskeletal Injuries Group Trials Register, The Cochrane Library, MEDLINE, EMBASE, Current Contents, Dissertation Abstracts, Index to UK Theses and the bibliographies of identified articles. Date of last search: December 1997 Any randomised or quasi-randomised trial evaluating a programme or treatment to prevent or treat lower limb stress reactions of bone or stress fractures in active young adults. Searching, a decision on inclusion or exclusion, methodological assessment, and data extraction were carried out according to a predetermined protocol included in the body of the review. Analysis using Review Manager software allowed pooling of data and calculation of Peto odds ratios and absolute risk reductions, each with 95% confidence intervals. The use of "shock absorbing" insoles, evaluated in four trials, appears to reduce the incidence of stress fractures and stress reactions of bone (Peto odds ratio 0.47, 95% confidence interval 0. 30 to 0.76). Incomplete data from one trial indicated that reduction of running and jumping intensity may also be effective. The use of pneumatic braces in the rehabilitation of tibial stress fractures significantly reduces the time to recommencing training (weighted mean difference -42.6 days, 95% confidence interval -55.8 to -29.4 days). The use of shock absorbing insoles in footwear reduces the incidence of stress fractures in athletes and military personnel. Rehabilitation after tibial stress fracture is aided by the use of pneumatic bracing.
Article
Microcracks in bone have been implicated in the development of stress fractures. The goal of this study was to evaluate bone strain and microcracks at locations where stress fractures are common (second metatarsal diaphysis) and rare (fifth metatarsal diaphysis) in an attempt to increase our understanding of the pathogenesis of stress fractures. A dynamic gait simulator was used to simulate normal walking with cadaver feet. The feet were loaded over the entire stance phase of gait and diaphyseal strains were recorded in second and fifth metatarsals. Microcrack density (Cr.Dn) and surface density (Cr.S.Dn) were determined in metatarsal cross sections from the contralateral feet. Bone strain was significantly higher in second metatarsals (-1897 +/- 613 microstrain) than in fifth metatarsals (-908 +/- 503 microstrain). However, second metatarsal Cr.Dn (0.23 +/- 0.15 #/mm(2)) was not significantly different from fifth metatarsal Cr.Dn (0.35 +/- 0.19 #/mm(2)). There was also no significant difference between Cr.S.Dn in second (17.64 +/- 10.99 microm/mm(2)) and fifth (26.70 +/- 15.53 microm/mm(2)) metatarsals. There were no significant relationships between the microcrack parameters and peak strain in either metatarsal. Cracks that occurred in trabecular struts (92 +/- 33 microm) were significantly longer than those found ending at cement lines (71 +/- 15 microm) and within osteons (57 +/- 16 microm). There were no significant relationships between the microcrack parameters and age in either metatarsal. Peak strain was more than twofold greater in second metatarsals than in fifth metatarsals for simulations of normal walking; however, microcrack parameters were unable to explain the greater incidence of second metatarsal stress fractures.
Article
Estimates are that stress fractures during basic training (BT) occur in as many as 14% of US female military recruits. Injuries of this type lead to morbidity ranging from minor pain to serious lifetime disability. Since women are assuming an increasing role in the military, this high risk of stress fracture is of concern. The purpose of this prospective study was to determine factors that predict stress fracture during BT in US Army female recruits. The analysis was part of an investigation using quantitative ultrasound (QUS) to determine risk of stress fracture during BT. Prior to the start of BT, we obtained QUS measurements and asked each subject to complete a risk factor questionnaire. We completed assessments for 3758 recruits who then proceeded to 8 weeks of BT, during which time any diagnosed stress fractures were reported to us by Army clinicians. Stress fractures were confirmed with radiographs. The incidence of stress fracture was 8.5% per 8 weeks. Factors associated with stress fracture include: QUS, age, race, alcohol and tobacco use, weight-bearing exercise, lowest adult weight, corticosteroid use, and, in white women only, use of depo-medroxyprogesterone acetate (DMPA). Women who fractured were older than women who remained fracture-free, and black women were less likely to sustain a fracture than whites and other races. Compared with their non-stress-fracture counterparts, recruits who developed stress fractures were more likely to report current or past smoking, alcoholic drinking of > 10 drinks/week, corticosteroid use and lower adult weight. A history of regular exercise was protective against stress fracture, and a longer history of exercise further decreased the relative risk of fracture. Although current weight was not associated with stress fracture, lowest adult weight was inversely related to the risk of fracture. We conclude that prevention of stress fractures in female military recruits should include a thorough assessment of lifestyle factors such as exercise patterns, alcohol and tobacco habits, and corticosteroid and DMPA use. Assessment of risk factors may be helpful in pinpointing female recruits who should have further evaluation of their bone health or additional preparation, such as gradual increases in physical activity, prior to being exposed to the rigor of BT.
Article
This in vivo study presents information to assist in the understanding of metatarsal stress fracture etiology. The aims were (a) to provide a fundamental description of loading patterns of the second metatarsal (MTII) during barefoot walking, and (b) to investigate the hypothesis that MTII dorsal strain increases with fatigue and external carrying load. Dorsal MTII strain was measured in vivo under local anaesthetic with an instrumented staple in eight subjects. Experimental conditions were external loading with a 20 kg backpack and pre- and post-fatigue. M. flexor digitorum longus electromyography tentatively indicated fatigue after an extended walking treatment. A reproducible, cyclic temporal pattern of dorsal MTII surface deformation was described. Mean peak compression and tension strains in unloaded barefoot walking were -1534 +/- 636 and 363 +/- 359 muepsilon, respectively. Mean peak compression strain rate (SR) was -4165 +/- 1233 muepsilon/s. Compression strain increased significantly (alpha=0.05) both with the addition of the backpack and post-fatigue while maximum tension decreased significantly post-fatigue. SR increased significantly with the addition of the backpack. The highest plantar force time integrals were recorded underneath the heads of metatarsals II-V for all conditions (1561Ns pre-fatigue, without backpack; 2123Ns post, with). EMG and plantar pressure data presented a comprehensive description of biomechanical parameters influencing dorsal MTII deformation and alterations in strain following two experimental conditions were suggested as contributing factors in the pathogenesis of metatarsal stress fractures.
Stress fractures in athletes. Doctoral Dissertation
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Computerised Gait Evaluation
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High strain rates are associated with stress fractures
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Förändringar i trykk-fördelningen under förfoten ved långvarig marsj
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