TY - JOUR
AU - PhD, Sharon J. Dixon,
AB - ABSTRACT The objective of this study was to investigate the influence of a commercially available orthotic device on rearfoot movement and peak impact force variables during running in combat assault boots. Eight military trainees performed running trials under two running conditions: boot with standard-issue insole and boot with the test orthotic. For each trial, vertical ground reaction force and frontal plane rearfoot angle data were collected. It was found that peak eversion angle was not significantly influenced by the orthotic device (p>0.05), but that this peak occurred later in stance (p < 0.05). Peak impact force, average rate of loading, and peak rate of loading of impact force were all lower when the orthotic device was used (p < 0.05). The findings of this study highlight the potential of a commercially available orthotic to provide benefits more typically associated with molded prescription orthoses, providing a cost-effective option to the routine use of prescription orthotic devices. Introduction Military recruits are typically required to wear boots for marching and running activities. These boots are constructed with a relatively stiff heel consisting of a rubber sole and cork midsole material, suggesting a lower cushioning ability than found in sports shoes. In support of this suggestion, tests of the mechanical impact-absorbing ability of the combat assault boot have provided peak deceleration values in the region of 28 g compared with between 9 and 15 g for running shoes tested under the same impact conditions.1,2 It has also been suggested that military boots limit the range of movement at the ankle and subtalar joints.3 These features of limited cushioning ability and restrictions on joint motion have been associated with increases in overuse injury susceptibility.4,5 Although dramatic changes in boot design are not feasible due to the requirements of the military boot to protect the foot from direct impacts, unpredictable ground conditions, and some extreme environmental conditions, it may be possible to manipulate the cushioning and support provided by the boot by the addition of inserts. These may be in the form of a cushioning insole1,6 or a supportive orthotic device.7,8 The biomechanical effect of cushioning insoles placed in military boots has recently been assessed for a range of commercially available insoles.1,6,9 These insoles are designed with the aim of adding material cushioning, without attempting to provide additional support to the foot. The use of these insoles in military boots has been shown to reduce peak heel and forefoot pressures in running and marching compared with boots alone.6,9 It has also been reported that some models of cushioning insole can reduce the peak rate of loading of ground reaction force during heel impact in running, as quantified using a force platform.1 As well as placing cushioning insoles in military footwear in an attempt to reduce the incidence of injury, the use of orthotic devices has been suggested. Orthotic devices are generally aimed at encouraging the subtalar joint to operate around a neutral orientation during the midstance phase of walking or running.10 They are designed to change the orientation of the foot and leg with respect to each other or the ground during the stance phase of running,11 typically aiming to resist “excessive” eversion of the foot and restore “normal” alignment to the entire lower limb.12 Studies of the effect of orthotics in running shoes have shown that they can be effective in reducing the maximum amount of eversion, maximum eversion velocity, and total rearfoot movement during ground contact.13,–16 It has also been suggested that orthotics can enhance the cushioning provided by eversion motion during the initial heel contact phase,16,–18 thus reducing the peak impact loading at heel strike. These movement and loading changes have been claimed to reduce the likelihood of overuse injuries such as Achilles tendinitis and tibial stress fractures.19,–21 Although it has previously been demonstrated that the incidence of stress fractures may be reduced by the use of a molded orthotic device in military boots,7,8 the mechanism by which these devices have been successful is not clear. Thus, further study of the biomechanical influence of orthotic devices in military footwear is required. Orthotic devices are generally obtained by prescription and are specific to each individual. However, it is not likely to be financially viable for all military recruits to be prescribed with individualized devices. An alternative is to use an “off-the-shelf,” mass-produced device at a fraction of the cost. Of the many such devices available on the market, one was selected for the present study. The manufacturers of this specific device claim that it provides both guidance and improved cushioning to the foot. It is claimed that the device “controls overpronation,” thus reducing the peak loads experienced by structures of the lower extremity. The purpose of the present study was therefore to assess the influence of a commercially available orthotic device on rearfoot movement and heel cushioning during running in military boots. Following the claims of the manufacturer and the available literature evidence, it was hypothesized that the device would reduce peak eversion angle, slow the rate of rearfoot eversion, and reduce the peak magnitude and rate of loading of impact force. Methods Eight military personnel (all members of the British Army or Territorial Army) volunteered as subjects (mean body weight, 793.6 ± 94.6 N). All individuals were free from injury at the time of the study and signed an informed consent form before the start of data collection. Subjects all wore their own standard issue combat assault boots. Each subject wore a new pair of standard issue socks for the study and wore shorts to allow attachment of markers directly to the skin. Reflective spherical markers were placed at selected anatomical landmarks to allow the monitoring of lower extremity joint movement. Markers were placed on the rear of the lower leg and boot to monitor rearfoot movement in the frontal plane. The leg markers were placed to represent the longitudinal axis of the lower leg, with the distal marker on the midline of the Achilles tendon at a height as close to the heel as possible, determined by the height of the boot, and the proximal marker below the belly of the gastrocnemius on a line joining the distal marker to the midpoint between the medial and lateral condyles of the knee. The heel markers were placed on the midline of the heel counter of the boot to represent the orientation of the calcaneus. Since boot markers are unlikely to accurately represent the bisection of the calcaneus, all rearfoot angle data are presented as relative angles, referenced to a defined standing position. Without direct measurement of calcaneal orientation, confidence in the clinical relevance of absolute values is limited. The decision to use relative angles is further supported by the main purpose of the study being to compare angle values with and without a shoe insert, thus negating the need for absolute values for rearfoot orientation. Each subject performed 10 successful running trials at 3.83 ms−1 (±5%) under each of two conditions: boots with standard-issue insole and boots with the orthotic device. The standard-issue insole is constructed from a weave material and is not designed to provide additional cushioning or support, but rather to provide a removable insole for hygiene purposes. The orthotic used is a semi-rigid device constructed from a full-length Trocellen foam footbed with a polypropylene stabilizer heel cup (Fig. 1). The device claims to “control overpronation” and to have a “natural shock absorption system.” The orthotic has a contoured upper surface and claims to follow the shape of the foot plantar surface. This includes a “support bridge” in the area of the longitudinal arch. The amount of cushioning provided by the insole material was assessed using a standard impact test procedure, with peak deceleration during impact presented as multiples of gravity (“peak g”).22 This revealed a value of 14 g with the orthotic placed in a military boot compared with 20 g for the boot with standard-issue insole. Reference standing angles were determined for a relaxed standing position with the standard-issue insole. These standing angles were used to determine relative rearfoot angles during running, as described by Edington et al.23 and Nawoczenski et al.#24 Fig. 1 View largeDownload slide Sample insoles illustrating rear view (a) and medial view (b). Fig. 1 View largeDownload slide Sample insoles illustrating rear view (a) and medial view (b). Subjects ran along a 15-m concrete runway, making a right foot contact with a force platform (AMTI OR6-5; AMTI Watertown, Massachusetts) situated flush with the runway surface. For each trial, kinematic data were collected at 120 Hz for the force plate contacting step and data were filtered using a Butterworth low-pass filter, cutoff frequency 8 Hz. Rearfoot angle was defined as indicated in Figure 2 and the rearfoot angle time history was characterized using angle immediately before ground contact (initial angle), peak eversion angle, range of rearfoot angle, and time to peak eversion (Fig. 3). Relative rearfoot angles were determined by calculation of the difference between the reference standing angles and the angles determined during running. Fig. 2 View largeDownload slide Marker placement and rearfoot angle definitions. Fig. 2 View largeDownload slide Marker placement and rearfoot angle definitions. Fig. 3 View largeDownload slide Sample rearfoot movement time history illustrating the test variables of initial inversion, peak eversion, and time to peak eversion. Fig. 3 View largeDownload slide Sample rearfoot movement time history illustrating the test variables of initial inversion, peak eversion, and time to peak eversion. Synchronized force data were sampled at 600 Hz for each running trial. Magnitude and time of occurrence of peak impact force, average loading rate, and peak rate of loading during heel impact were determined. Mean values were determined for all variables over the 10 successful running trials and were used to represent the values for each individual subject. Comparisons of group means for the two conditions were performed using a paired t test (p < 0.05). Results Group mean values (SD) for absolute standing angle, peak eversion angle relative to the reference standing, total rearfoot movement, time taken from ground contact to peak rearfoot angle, and peak eversion velocity are presented in Table I. Placement of the orthotic device in the subjects' boots resulted in a smaller amount of rearfoot eversion during standing (-0.6 degrees), but the difference between conditions was not significant (p>0.05). In contrast to this reduced angle, during running the use of the orthotic device caused a slightly greater peak rearfoot angle (+1.1 degrees), but this change was not significant (p > 0.05). A greater amount of total rearfoot movement over the period from ground contact to peak eversion was also observed for the orthotic condition. Although this difference was not statistically significant (p>0.05), it was found that seven of the eight subjects demonstrated a greater total rearfoot movement when using the orthotic device compared with the control condition (Fig. 4). When running with the orthotic in the boot, there was a significantly greater time taken from initial ground contact to peak eversion (p < 0.05). This later occurrence of peak eversion angle was consistent across all eight subjects (Fig. 5). Despite this greater time over which eversion occurred with the orthotic, eversion velocity was not significantly reduced (p>0.05). TABLE I MEAN VALUES (SD) FOR STANDING ANGLE, PEAK REARFOOT ANGLE (ABSOLUTE), PEAK REARFOOT ANGLE (RELATIVE), TOTAL REARFOOT ANGLE, AND TIME OF PEAK REARFOOT ANGLEa   Absolute Standing Angle (degrees)  Peak Relative Rearfoot Angle (degrees)  Total Rearfoot Movement (degrees)  Time of Peak Rearfoot Angle (m/s)  Peak Rearfoot Eversion Velocity (degrees.s−1)  Control  −2.5 (2.2)  −9.0 (1.8)  −9.5 (5.2)  91 (11)  231 (78)  Orthotic  −1.9 (2.2)  −10.1 (2.4)  −11.2 (6.2)  108 (9)a  240 (82)    Absolute Standing Angle (degrees)  Peak Relative Rearfoot Angle (degrees)  Total Rearfoot Movement (degrees)  Time of Peak Rearfoot Angle (m/s)  Peak Rearfoot Eversion Velocity (degrees.s−1)  Control  −2.5 (2.2)  −9.0 (1.8)  −9.5 (5.2)  91 (11)  231 (78)  Orthotic  −1.9 (2.2)  −10.1 (2.4)  −11.2 (6.2)  108 (9)a  240 (82)  a Significant difference between conditions, p < 0.05. View Large TABLE I MEAN VALUES (SD) FOR STANDING ANGLE, PEAK REARFOOT ANGLE (ABSOLUTE), PEAK REARFOOT ANGLE (RELATIVE), TOTAL REARFOOT ANGLE, AND TIME OF PEAK REARFOOT ANGLEa   Absolute Standing Angle (degrees)  Peak Relative Rearfoot Angle (degrees)  Total Rearfoot Movement (degrees)  Time of Peak Rearfoot Angle (m/s)  Peak Rearfoot Eversion Velocity (degrees.s−1)  Control  −2.5 (2.2)  −9.0 (1.8)  −9.5 (5.2)  91 (11)  231 (78)  Orthotic  −1.9 (2.2)  −10.1 (2.4)  −11.2 (6.2)  108 (9)a  240 (82)    Absolute Standing Angle (degrees)  Peak Relative Rearfoot Angle (degrees)  Total Rearfoot Movement (degrees)  Time of Peak Rearfoot Angle (m/s)  Peak Rearfoot Eversion Velocity (degrees.s−1)  Control  −2.5 (2.2)  −9.0 (1.8)  −9.5 (5.2)  91 (11)  231 (78)  Orthotic  −1.9 (2.2)  −10.1 (2.4)  −11.2 (6.2)  108 (9)a  240 (82)  a Significant difference between conditions, p < 0.05. View Large Fig. 4 View largeDownload slide Single subject changes in total rearfoot movement with and without the orthotic device. Fig. 4 View largeDownload slide Single subject changes in total rearfoot movement with and without the orthotic device. Fig. 5 View largeDownload slide Single subject changes in time to peak rearfoot eversion with and without the orthotic device. Fig. 5 View largeDownload slide Single subject changes in time to peak rearfoot eversion with and without the orthotic device. Group mean values (SD) for peak magnitude and time of occurrence of peak impact force, peak rate of loading, and average rate of loading are presented in Table II. It was found that peak impact force, peak rate of loading, and average rate of loading were significantly reduced when the orthotic device was placed in the boot (p < 0.05). There was also a significantly longer time taken from initial ground contact to occurrence of peak impact force for the orthotic condition compared with when running in the boot only (p < 0.05). TABLE II MEAN VALUES (SD) FOR PEAK IMPACT FORCE, OCCURRENCE TIME OF PEAK IMPACT FORCE, AVERAGE RATE OF LOADING, AND PEAK LOADING RATE OF IMPACT FORCE   Peak Impact Force (N)  Time of Peak Impact Force (m/s)  Average Loading Rate (N/s)  Peak Loading Rate (N/s)  Control  1,552.6 (211.0)  24.9 (3.5)  63,974 (11,851)  120,980 (25,747)  Orthotic  1,431.9 (264.7)a  27.9 (3.8)a  52,397 (11,280)a  93,412 (22,740)a    Peak Impact Force (N)  Time of Peak Impact Force (m/s)  Average Loading Rate (N/s)  Peak Loading Rate (N/s)  Control  1,552.6 (211.0)  24.9 (3.5)  63,974 (11,851)  120,980 (25,747)  Orthotic  1,431.9 (264.7)a  27.9 (3.8)a  52,397 (11,280)a  93,412 (22,740)a  a Significant difference between conditions, p < 0.05. View Large TABLE II MEAN VALUES (SD) FOR PEAK IMPACT FORCE, OCCURRENCE TIME OF PEAK IMPACT FORCE, AVERAGE RATE OF LOADING, AND PEAK LOADING RATE OF IMPACT FORCE   Peak Impact Force (N)  Time of Peak Impact Force (m/s)  Average Loading Rate (N/s)  Peak Loading Rate (N/s)  Control  1,552.6 (211.0)  24.9 (3.5)  63,974 (11,851)  120,980 (25,747)  Orthotic  1,431.9 (264.7)a  27.9 (3.8)a  52,397 (11,280)a  93,412 (22,740)a    Peak Impact Force (N)  Time of Peak Impact Force (m/s)  Average Loading Rate (N/s)  Peak Loading Rate (N/s)  Control  1,552.6 (211.0)  24.9 (3.5)  63,974 (11,851)  120,980 (25,747)  Orthotic  1,431.9 (264.7)a  27.9 (3.8)a  52,397 (11,280)a  93,412 (22,740)a  a Significant difference between conditions, p < 0.05. View Large Discussion The hypothesis that the orthotic insert would reduce peak rearfoot eversion and eversion velocity has not been supported by the results of the present study, with no significant differences detected between conditions in either of these variables. In fact, despite no significant difference, an increase in total rearfoot movement has been observed for seven of the eight subjects when running with the orthotic in their boots. The absence of a significant effect of a shoe insert on peak rearfoot eversion observed in the present study is consistent with several previous studies of the influence of orthotic devices placed in everyday shoes, sandals, and in running shoes.14,17,23 However, other studies have reported significant reductions in peak rearfoot eversion with an orthotic intervention.13,15,16,18 The conflicting results of studies regarding the influence of orthotics on rearfoot eversion is likely to be contributed to substantially by the construction of the orthotic devices with differing materials, different casting (molding) methods, and different amounts of posting. The device used in the present study did not have a medial posting. Thus, the construction of the tested orthotic does not appear to be directed at limiting rearfoot motion. This likely explains the absence of a reduction in this variable. Consistent with suggestions that orthotic devices control eversion, the time taken to reach peak eversion has been significantly delayed. This delay has failed to reduce the velocity of eversion because of the tendency for greater total rearfoot movement with the orthotic. Although factors such as subject foot type were not controlled for, this effect was consistent across all eight subjects (Fig. 4). It may be argued that the foot-shaped design of the device has contributed to a greater eversion movement, occurring in a more controlled way than that occurring for the boots with standard-issue insole. The observation of an increased time to peak eversion has been reported by other authors studying shoe insert effects.18,25 In addition, the tendency for increased total rearfoot movement supports recent suggestions that a foot-shaped orthotic allows for necessary foot eversion movement.16 The hypotheses relating to vertical ground reaction force presented in this study have all been supported by the study results. These results indicate that the placement of the test or-thotic in military boots provides an increased cushioning of impact force compared with the control condition. In a previous study of a range of cushioning inserts placed in military boots, it was found that there were no reductions in peak impact force.1 Thus, while not being specifically designed using a cushioning material, the orthotic device tested in the present study appears to perform better than cushioning inserts in terms of a reduction in peak impact force. It has previously been suggested that a reduction in peak impact force is associated with an increased amount of rearfoot movement and/or velocity of eversion.26,27 The reductions in peak impact force in the present study may be contributed to by the greater total rearfoot movement tending to occur with the orthotic device, with seven of the eight subjects showing this response (Fig. 4). The observed reduction in impact force with a shaped orthotic device is consistent with findings of Mündermann et al.16 who reported a reduction in impact force when using a subject-specific molded orthotic. The results of Mündermann et al.16 highlight the importance of providing a foot-shaped insert if a reduction in impact force is desirable. Since military boots provide minimal cushioning of impact force, an insert that has this effect is likely to be beneficial. However, the prescription of orthotic devices by taking a mold of the individual foot is costly and often not practical for all military personnel. The present study insert has a shaped profile that appears to have a similar affect to a molded insert, despite not being tailored to be specific to the subject. This suggests that the shape of this insert provides some of the benefits of a prescription orthotic without the associated cost. Although it is likely to be appropriate to have an individualized orthotic for certain cases, the results of the present study demonstrate the possible benefits of adopting an off-the-shelf insert for routine use by military personnel. A limitation of the present study methodology is the use of two-dimensional frontal plane angle to indicate the amount of rearfoot eversion. Comparisons of two-dimensional versus three-dimensional rearfoot eversion data have indicated that peak eversion values are comparable for the two methodologies, due to the foot and lower leg being aligned approximately in the frontal plane at the time of peak eversion.28 This supports the use of two-dimensional data for the quantification of peak eversion magnitude and time of occurrence in the present study. However, as a result of the foot and lower leg being inclined out of the frontal plane at ground strike, caution is advised when considering initial inversion angle, and hence total rearfoot movement. In additional support of the present study methodology, the described methods were used to compare values between conditions, rather than to determine absolute rearfoot angle values. It is proposed that the limitation of using two-dimensional data does not influence the conclusions of the present study. However, it is recommended that, where possible, three-dimensional angles would be preferred for monitoring of rearfoot movement during running. In conclusion, it has been demonstrated in the present study that a mass-produced orthotic insert can reduce peak impact force magnitude and rate of loading and delay peak rearfoot eversion when placed in a military boot. Since most studies of footwear manipulations have failed to cause detectable changes in peak impact force,29,30 the observed significant effect is of note. No attempt has been made in the present study to control for subject characteristics such as foot type and yet the majority of subjects have responded similarly. Although high-impact force variables have been associated with injury susceptibility,26 the observation in the present study that these variables can be influenced positively by the test orthotic is not sufficient to conclude that injury can be reduced by using this orthotic device. A prospective study of the influence of the test orthotic on injury frequency in military personnel is required to test this suggestion. Acknowledgments We thank Mr. Samuel Warren for data collection. References 1. Dixon SJ, Waterworth C, Smith CV, House CM Biomechanical analysis of running in military boots with new and degraded insoles. Med Sci Sports Exerc  2003; 35: 472– 9. Google Scholar CrossRef Search ADS PubMed  2. SATRA Bulletin Performance requirements of sports footwear.  1990: Northants, U.K., Satra, 1990. 3. Riddell DI Changes in the incidence of medical conditions at the Commando Training Centre, Royal Marines. J R Nav Med Serv  1990; 76: 105– 8. Google Scholar PubMed  4. Milgrom C, Finestone Shlamkovitch N, et al.   Prevention of overuse injuries of the foot by improved shoe shock attenuation, a randomised prospective study. Clin Orthop  1992; 281: 189– 92. 5. Rosenblad-Wallin EFS Design and evaluation of military footwear based on the concept of healthy feet. Ergonomics  1988; 31: 1245– 56. Google Scholar CrossRef Search ADS   6. Windle CM, Gregory SM, Dixon SJ The shock attenuation characteristics of four different insoles when worn in a military boot during running and marching. Gait Posture  1999; 9: 31– 7. Google Scholar CrossRef Search ADS PubMed  7. Milgrom C, Giladi M, Kashtan H, et al.   A prospective study of the effect of a shock absorbing orthotic device on the incidence of stress fractures in military recruits. Foot Ankle Int  1985; 6: 101– 4. Google Scholar CrossRef Search ADS   8. Simkin A, Leichter I, Giladi M, Stein M, Milgrom C Combined effect of foot arch structure and an orthotic device on stress fractures. Foot Ankle Int  1989; 10: 25– 9. Google Scholar CrossRef Search ADS   9. House CM, Waterworth C, Allsopp AJ, Dixon SJ The influence of simulated wear upon the ability of insoles to reduce peak pressures during running when wearing military boots. Gait Posture  2002; 16: 297– 303. Google Scholar CrossRef Search ADS PubMed  10. Whittle MW Generation and attenuation of transient impulsive forces beneath the foot: a review. Gait Posture  1999; 10: 264– 75. Google Scholar CrossRef Search ADS PubMed  11. Barnes RA, Smith PD The role of footwear in minimizing lower limb injury. J Sports Sci  1994; 12: 341– 53. Google Scholar CrossRef Search ADS PubMed  12. Kilmartin TE, Wallace WA The scientific basis for the use of biomechanical foot orthoses in the treatment of lower limb sports injuries-a review of the literature. Br J Sports Med  1994; 28: 180– 4. Google Scholar CrossRef Search ADS PubMed  13. Smith LS, Clarke TE, Hamill CL, Santopietro F The effects of soft and semi-rigid orthoses upon rearfoot movement in running. J Am Podiatr Med Assoc  1986; 76: 227– 32. Google Scholar CrossRef Search ADS PubMed  14. Nigg BM, Khan A, Fisher V, Stephanyshyn D Effect of shoe insert construction on foot and leg movement. Med Sci Sports Exerc  1998; 30: 550– 5. Google Scholar CrossRef Search ADS PubMed  15. Rodgers M, Leveau B Effectiveness of orthotic devices used to modify pronation in runners. J Orthop Sports Phys Ther  1982; 4: 86– 90. Google Scholar CrossRef Search ADS PubMed  16. Mündermann A, Nigg BM, Humble RN, Stephanyshyn DJ (2003). Foot orthotics affect lower extremity kinematics and kinetics during running. Clin Biomech  2003; 18: 254– 62. Google Scholar CrossRef Search ADS   17. Blake RL, Ferguson H Extrinsic rearfoot posts. J Am Podiatr Med Assoc  1992; 82: 202– 7. Google Scholar CrossRef Search ADS PubMed  18. Novick A, Kelly D Position and movement changes of the foot with orthotic intervention during the loading response of gait. J Orthop Sports Phys Ther  1990; 11: 301– 12. Google Scholar CrossRef Search ADS PubMed  19. Donatelli R, Hurlbert C, Conaway D, et al.   Biomechanical foot orthotics: a retrospective study. J Orthop Sports Phys Ther  1988; 10: 205– 12. Google Scholar CrossRef Search ADS PubMed  20. Gross ML, Davlin LB, Evanski PM Effectiveness of orthotic shoe inserts in the long-distance runner. Am J Sports Med  1991; 19: 409– 12. Google Scholar CrossRef Search ADS PubMed  21. Sperryn PN, Reestan L Podiatry and sports physician: an evaluation of orthoses. Br J Sports Med  1983; 7: 129– 34. Google Scholar CrossRef Search ADS   22. ASTM F1614–99 Standard Test Method for Shock Attenuating Properties of Materials Systems for Athletic Footwear , West Conshohacken, PA, ASTM International, 2003. 23. Edington CJ, Frederick EC, Cavanagh PR Rearfoot motion in distance running. In: Biomechanics of Distance Running, Ch 5 , pp 137– 64. Edited by Cavanagh PR Champaign, IL, Human Kinetics, 1990. 24. Nawoczenski DA, Cook TM, Saltzman CL The effect of foot orthotics on three-dimensional kinematics of the leg and rearfoot during running. J Orthop Sports Phys Ther  1995; 21: 317– 27. Google Scholar CrossRef Search ADS PubMed  25. Bates BT, Osternig LR, Mason B, et al.   Foot orthotic devices to modify selected aspects of lower extremity mechanics. Am J Sports Med  1979; 7: 338– 42. Google Scholar CrossRef Search ADS PubMed  26. Hrejac A, Marshall RN, Hume PA Evaluation of lower extremity overuse injury potential in runners. Med Sci Sports Exerc  2000; 32: 1635– 41. Google Scholar CrossRef Search ADS PubMed  27. Perry SD, Lafortune MR Influences of inversion/eversion of the foot upon impact loading during locomotion. Clin Biomech  1995; 10: 253– 7. Google Scholar CrossRef Search ADS   28. Souttas-Little RW, Beavis GC, Verstaraete MC, Marcus TL Analysis of foot motion during running using a joint coordinate system. Med Sci Sports Exerc  1987; 19: 285– 93. Google Scholar CrossRef Search ADS PubMed  29. Nigg BM, Bahlsen HA The influence of heel flare and midsole construction on pronation, supination and impact forces for heel-toe running. Int J Sports Biomech  1988; 4: 205– 19. Google Scholar CrossRef Search ADS   30. Nigg BM, Bahlsen HA, Luethi SM, Stokes S The influence of running velocity and midsole hardness on external impact forces in heel-toe running. J Biomech  1987; 20: 951– 9. Google Scholar CrossRef Search ADS PubMed  Reprint & Copyright © Association of Military Surgeons of the U.S.
TI - Influence of a Commercially Available Orthotic Device on Rearfoot Eversion and Vertical Ground Reaction Force When Running in Military Footwear
JF - Military Medicine
DO - 10.7205/MILMED.172.4.446
DA - 2007-04-01
UR - https://www.deepdyve.com/lp/oxford-university-press/influence-of-a-commercially-available-orthotic-device-on-rearfoot-5UzLrNlMEF
SP - 446
EP - 450
VL - 172
IS - 4
DP - DeepDyve
ER -