A-40 Free Communication/Poster - Foot and Ankle

Medicine & Science in Sports & Exercise:
doi: 10.1249/01.mss.0000433615.66674.76

    May 29, 2013, 7:30 AM - 12:30 PM

    Room: Hall C

    260 Board #112 May 29, 11:00 AM - 12:30 PM

    Muscle Synergies during Side-Cutting in People with Chronic Ankle Instability

    Kristof Kipp1, Camilla Malowanski1, Riann M. Palmieri-Smith2. 1Marquette University, Milwaukee, WI. 2University of Michigan, Ann Arbor, MI. (Sponsor: Paula Papanek, FACSM)

    (No relationships reported)

    People with chronic ankle instability (CAI) display different muscle activations during movement than healthy people. The neural control that underlies these differences, however, has not been studied. Muscle synergies have been used previously to investigate neural control patterns during movement.

    PURPOSE: To determine differences in muscle synergies during side-cutting between people with CAI and healthy controls.

    METHODS: Eleven people with CAI and 11 healthy matched controls (CON) performed and side-cutting task. Five trials were collected for each person. EMG data were collected from the Tibialis Anterior, Soleus, Peroneus Longus, Medial Gastrocnemius, and Lateral Gastrocnemius muscles during the stance phase of the cutting task. EMG data were band-pass filtered, rectified, smoothed, time-normalized to 100% of stance, and ensemble averaged. The ensemble averaged data from all five muscles were then pooled into a single 5 × 101 (muscles x % stance) matrix. A factor analysis was run on the correlation matrix. After a varimax-rotation, the eigenvectors and eigenvalues were subsequently extracted. The eigenvalue magnitudes associated with each eigenvector were used to calculate the percent variance explained by each muscle synergy, which in turn was used to calculate the cumulative variance. Group comparisons were made with a two-tailed t-test.

    RESULTS: The cumulative variances explained by the muscle synergies did not differ between groups (see Table).

    CONCLUSIONS: The similarity in muscle synergies suggests that people with CAI and healthy people use similar neural control strategies to regulate ankle muscle activations during side-cutting.

    261 Board #113 May 29, 11:00 AM - 12:30 PM

    Neuromuscular Exercises With Different Devices: Progression of Ankle Muscle Activation

    Joaquin Calatayud1, Juan Carlos Colado1, Sebastien Borreani1, Fernando Martin1, Victor Tella1, Michael E. Rogers, FACSM2. 1University of Valencia, Valencia, Spain. 2Wichita State University, Wichita, KS.

    (No relationships reported)

    The ankle is the second most commonly injured body part in sports and ankle sprains are the most common type of ankle injury. Female athletes have a high rate of ankle injury in some team sports. Rehabilitation must include neuromuscular training to improve postural and neuromuscular control and prevent recurrent sprains. The methods of optimal progression are not known in the neuromuscular training despite the frequent use of these kinds of exercises and devices.

    PURPOSE: To compare ankle muscular activity performing 4 exercises in stable and unstable conditions.

    METHODS: 20 physically fit and healthy female subjects took part in a randomized, within-subject design assessment. The maximum isometric voluntary contraction (MIVC) was evaluated for the normalization. Peroneus longus (PL), tibialis anterior (TA) and soleus (S) muscular activities were recorded and the average root mean square values were calculated. Surface electromyography activity was analyzed during the central 16 seconds of 20 in 4 isometric unipodal postures: Sitting on a Thera-Band exercise ball with the foot over the floor (SF), standing up on the floor (UF), standing up on a Thera-Band Rocker Board (UR) and standing up on a soft Thera-Band Stability Trainer (US). All values, expressed as the mean of the 5 muscles %MIVC, were compared using a mixed-model MANOVA with a Bonferroni post-hoc analysis. Significance level was set at p≤0.05.

    RESULTS: Significant differences were found between conditions for PL (p<0.001), TA (p=0.011), S (p<0.001) and global muscles (p<0.001) (See Table 1).

    CONCLUSION: Specialists that use these devices for balance training, injury prevention or rehabilitation may use this information to develop an optimal exercise progression.

    262 Board #114 May 29, 11:00 AM - 12:30 PM

    The Validity and Reliability of Navicular Angle Method in Measuring Foot Arch

    Zhang J. Yuan, Hui-Mei Lin, Yu-Hua Tseng, Szu-Kai Fu. Taipei physical education college, Taipei, Taiwan.

    (No relationships reported)

    Ideally the foot arch is a balanced biomechanical structure consisting of bones, joints, muscles, tendons and ligaments. When the posture of the feet or balance is not correct, it could result in feet problems, which may in turn cause related problems in the ankles, knees, hips and lower back.

    PURPOSE: The purpose of this study was to develop easy method of Navicular Angle Method (NA) to evaluate foot arch, and investigate the relations between NA, Navicular Drop Index (NDI) and X-ray to approve the efficacy of NA.

    METHODS: 60 children participated in this study (8.42±0.53 yrs, 25.6±3.5 kg, 129.1±3.5 cm). The bilateral NDI, NA and X-ray were measured in non-weight bearing and even-weight bearing by physical therapists. The 2nd measurement was performed in the 7th days.

    RESULTS: The intra-rater reliability of NA (intra-rater reliability=0.981, p<0.01) was higher than NDI (intra-rater reliability=0.974, p<0.01) and X-ray (intra-rater reliability=0.574, p=0.28). The inter-rater reliability of NA was higher (inter-rater reliability=0.982, p<0.05).The correlation coefficient between NA and NDI (r=0.942, p<0.05) was higher than NA and X-ray(r=0.714, p=0.21).

    CONCLUSION: The intra-rater reliability and inter-rater reliability of Navicular Angle method were high. Findings suggest that Navicular Angle Method (NA) may be an effective tool for physical therapists and common teachers to measuring foot arch, because it requires less equipment and is more easily

    Keyword : foot arch , navicular drop index , arch measurement.

    263 Board #115 May 29, 11:00 AM - 12:30 PM

    Does Ankle Joint Laxity Correlate with Anterior Talofibular Ligament Thickness?

    Kathy Liu1, Geoff Gustavsen2, Thomas W. Kaminski, FACSM2. 1University of Evansville, Evansville, IN. 2University of Delaware, Newark, DE.

    (No relationships reported)

    The anterior talofibular ligament (ATFL) limiting plantar flexion and inversion, is most susceptible to damage during a lateral ankle sprain. An injury to the ATFL can result in morphological changes that have been reported to decrease load capacity and increase ligamentous laxity. What is not known is whether or not a relationship exists between ankle joint laxity and ATFL thickness.

    PURPOSE: To determine if there is a relationship between ankle joint laxity as measured by joint arthrometry and ligament thickness as measured by musculoskeletal ultrasound (MSUS) in a cohort of intercollegiate athletes.

    METHODS: One hundred seventy one Division-I collegiate athletes (76 females, 95 males, age = 18.7 ± 0.9 yrs., height = 178.1 ± 11.3 cm, mass = 79.2 ± 19.2 kg) participated in this study. Measurements for anterior displacement and inversion rotation of the ankle were obtained using an instrumented ankle arthrometer. Measurements for ATFL thickness were obtained using MSUS. Thickness was measured at the midpoint of the ligament between the attachments on the lateral malleolus and talus then normalized to body mass. Measurements were taken from a randomly selected ankle of each participant. Data were analyzed using linear regression techniques correlating laxity measures with thickness values.

    RESULTS: Laxity in the anterior direction positively correlated with normalized ligament thickness (p ≤ 0.001, r2 = 0.10). In addition, inversion rotation laxity also positively correlated with normalized ligament thickness (p=0.004, r2 = 0.04).

    CONCLUSION: This is the first study of its kind examining the relationship between ankle joint laxity and ATFL thickness. Since the ATFL undergoes the daily stresses exerted from body mass and gravity, ligament thickness was normalized to body mass. These results indicate that both anterior and inversion ankle joint laxity positively correlate with morphological characteristics of the ATFL, signifying that as laxity increases, ligament thickness also increases. Since previous literature has reported that morphological changes in a ligament can decrease its load capacity, we contend that a thicker ligament, possibly due to scar tissue formation after injury, can increase the laxity of the ligament. Further studies involving injured versus uninjured cohorts are warranted.

    264 Board #116 May 29, 11:00 AM - 12:30 PM

    Changes of Balancing Ability After Foot Orthotics Application and Rehabilitation Exercise in Athletes with Chronic Ankle Instability

    Hongjae Lee1, Kil-Byung Lim1, Dug-Young Kim2, Yong-Kyun Kim3, Ho-Jun Lee4. 1Ilsanpaik Hosp., Inje Univ College of Medicine, Goyang, Republic of Korea. 2CHA University College of Medicine, Seoul, Republic of Korea. 3Myongji Hospital Kwandong University College of Medicine, Goyang, Republic of Korea. 4Ilsan Hospital Dongguk University College of Medicine, Goyang, Republic of Korea.

    (No relationships reported)

    PURPOSE: To compare the effect of foot orthotics application and rehabilitation

    exercise treatment by using measurement of balancing ability and joint proprioception in the athletes who had chronic ankle instability

    METHODS: 41 athletes who visited hospitals due to chronic ankle instability were randomly assigned into two groups. One group had ankle rehabilitation exercise while the other group had an application with foot orthotics(semirigid semi-customized orthotics) and the same rehabilitation exercise for 4 weeks. Joint position sense of the ankle joint was examined by using isokinetic exercise machine. Balancing abilities categorized into static, dynamic and functional balance abilities were evaluated by using computerized posturography (Balance Master system). We tested the subjects before and after four-week rehabilitation program.

    RESULTS:Regarding the joint reposition sense evaluation, when the ankle eversion 75% angle evaluation was given, foot orthotics group showed the improvement of 1.07±1.64 degree on average (angle of reposition error) after 4 weeks and the ankle exercise group did 0.23±2.05 degree improvement. However, there was no statistically significant difference between two groups in terms of the amounts of improvement (p>0.05). Static, dynamic and functional balancing ability test revealed that the foot orthotics groups improved in some items after 4 weeks such as two leg standing on firm plate, one leg standing, front/backward weight shifting speed, maximal excursion to backward direction and injured leg side, and step-up speed, but there was no statistically significant difference between two groups in terms of the amounts of improvement (p>0.05).

    CONCLUSIONS: This study revealed that when a four-week foot orthotics application and ankle rehab exercise was given to athletes with chronic ankle instability, there were some improvements in their proprioception and balancing ability but there was no statistically additional effects compared with rehabilitation exercise.

    265 Board #117 May 29, 11:00 AM - 12:30 PM

    Pre-operative Gait Speed As An Indicator Of Subjective And Functional Recovery Following Total Ankle Replacement

    Robin M. Queen, Tawnee L. Sparling, Mark E. Easley, James K. DeOrio, James A. Nunley, Robert J. Butler. Duke University, Durham, NC. (Sponsor: Donald T. Kirkendall, FACSM)

    (No relationships reported)

    End-stage ankle arthritis is as functionally debilitating as congestive heart failure and end-stage kidney disease and is often treated with total ankle replacement surgery (TAR). However, following TAR patients have persistent functional deficits.

    PURPOSE:To understand the effect of preoperative (PRE) gait speed on 1 and 2 year post-operative (POST) function and patient reported outcomes.

    METHODS:Patients with end-stage ankle arthritis (N=123) were enrolled in this study. Subject’s average age and weight were 64.1yrs and 83.8kg, respectively. PRE data were collected prior to TAR; patients were examined using the same methods 1 and 2 years POST. A series of questionnaires (AOFAS Hindfoot Scale, SF-36, FADI), functional tests (Timed Up and Go (TUG), Sit to Stand (STS), and the Four Square Step Test (4SST)), and walking speed were collected. Patients received no formal rehabilitation. Subjects were divided into 4 cohorts based on mean PRE walking speed (Mean+/-1SD, Mean +/- 2SD). A series of 3 X 4 (time X walking speed group) mixed model, repeated measures ANOVAs were completed.

    RESULTS:Significant interactions existed for TUG, STS, and walking speed. The largest gains were observed for all groups between PRE and 1 year (p < 0.01) with no differences between 1 and 2 years (p = 0.40). The groups with lower gait speed PRE exhibited the largest improvements over the course of the study. During the 4SST, the groups below the mean walking speed exhibited 37-50% improvements between PRE and 1 year. The fastest walking speed group had no change in 4SST performance between PRE and 1 year, yet this group did show a 34% increase in performance between 1 and 2 years. Visual analog pain, FADI, SF36, and AOFAS were all improved following surgery (p < 0.01); however, no differences existed between 1 and 2 years POST and no differences existed across walking speed groups.

    CONCLUSIONS:PRE gait speed appears to be associated with patient outcomes following TAR. It is interesting to note that over the course of the study, only the high PRE walking speed group achieved community ambulation walking speed (1.3m/s). This suggests that other factors may be influential in returning patients to “normal” and that rehabilitation may be appropriate and relevant in patients with lower PRE walking speed in order to maximize POST functional recovery.

    266 Board #118 May 29, 11:00 AM - 12:30 PM

    The Effects of Two Ankle Destabilization Devices on Electromyography Measures During Walking

    Luke Donovan, Joe M. Hart, Jay Hertel, FACSM. University of Virginia, Charlottesville, VA.

    (No relationships reported)

    Ankle destabilization devices may improve neuromuscular control by increasing lower extremity muscle activation. The effects of these devices are unclear and should be tested in healthy individuals before being implemented in rehabilitation programs for patients with ankle pathology.

    PURPOSE: To compare EMG activation of lower extremity muscles during walking gait while wearing 2 different ankle destabilization devices.

    METHODS: Fifteen healthy young adults walked on a treadmill while we recorded surface EMG from the anterior tibialis (AT), peroneus longus (PL), and lateral gastrocnemius (LG) muscles. Subjects walked shod, with an ankle destabilization device (ADD), or ankle destabilization sandal (ADS) in random order. Normalized amplitudes 100ms pre- and 200ms post initial heel contact, time of onset activation relative to initial contact, and percent of activation time across the stride cycle were calculated for each muscle. Each dependent variable was compared using a repeated measures ANOVA and post-hoc t-tests if appropriate, alpha was set at P≤0.05.

    RESULTS: The pre-contact amplitudes of the PL and LG were significantly greater in the ADD (PL 0.34±0.35, p=0.05; LG 0.36±0.32 p=0.001) and ADS (PL 0.26±0.19, p=0.003; LG: 0.30±0.27, p=0.001) conditions when compared to shod (PL 0.15±0.16; LG 0.11±0.14mV). The post-contact amplitude of the LG was significantly greater in the ADD (LG 0.71±0.89, p=0.033) and the ADS (0.54±0.47, p=0.025) conditions when compared to shod (LG 0.29±0.32mV). The PL and LG were activated significantly earlier in the ADD (PL -0.006±0.07, p<0.001; LG 0.03±0.14, p<0.001) and the ADS (PL 0.02±0.08, p<0.001 LG 0.11±0.15, p=0.001) conditions when compared to shod (PL 0.156±0.16ms; LG 0.25±0.13ms). The AT, PL and LG were activated significantly longer across the stride cycle in the ADD (AT 72±22.9, p<0.001; PL 36.4±14.4, p=.032 LG 33.7±17.4, p<0.001) condition, but only the AT and LG were higher in the ADS (AT 64.5±29.9, p<0.001; LG 30.4±18.6, p=0.002) condition when compared to shod (AT 52.7±25; PL 23.3±22.2; LG 18.6±11.6%).

    CONCLUSION: Both ankle destabilization devices caused an alteration in muscle activity during walking. The increase in amplitude and earlier onset of the peroneus longus at initial contact may enhance ankle stability when wearing unstable footwear.

    267 Board #119 May 29, 11:00 AM - 12:30 PM

    Ankle Joint Coupling During Walking With Chronic Ankle Instability

    C. Colin Herb1, Lisa Chinn1, Jay Dicharry1, Patrick Mckeon2, Joe Hart1, Jay Hertel, FACSM1. 1University of Virginia, Charlottesville, VA. 2University of Kentucky, Lexington, KY.

    (No relationships reported)

    PURPOSE: To identify differences in the joint coupling patterns between tibial internal/external rotation and rearfoot inversion/eversion of chronic ankle instability (CAI) and healthy control subjects throughout the gait cycle while walking in both barefoot and shod conditions.

    METHODS: Twenty-eight active adults volunteered for the study. (CAI, n=15, Foot and Ankle Activity Measure-Sport (FAAMS) = 92.1±5.8, previous sprains = 4.9±2.5; Control, n=13, FAAMS = 100±0.0) Kinematic data was collected by a 12 camera motion analysis system while walking (4.83 km/hr) on an instrumented treadmill in both barefoot and shod conditions. Data was analyzed using a vector coding method, extracting the magnitude (m) and direction (theta) of the joint coupling motions from generated angle-angle plots. Means and associated 90% confidence intervals (CI) were compared across the entire gait cycle. Means and standard deviations were found during these periods where CIs did not overlap.

    RESULTS: Shod theta differences were found during late-stance (45-52%, control 42.6°±6.7°, CAI 30.0°±9.21°) and late-swing (82-92%, control 66.2°±6.6°, CAI 56.4°±9.2°) between CAI and controls. Differences for m were found in the shod condition during late-stance (49-51%, control 0.7°±0.1°, CAI 1.0°±0.1°) and late-swing (81-91%, control 2.7°±0.1°, CAI 2.5°±0.2°). Barefoot theta differences were found during early-stance (4-14%, control 76.4°±3.3°, CAI 68.6°±5.8°), late-stance (52-60%, control 60.3°±15.6°, CAI 72.3°±11.2°), and mid-swing (69-75%, control 66.1°±5.7°, CAI 73.8°±5.6°) . Differences in the barefoot condition for m were found during early stance (6-15%, control 0.3°±0.2°, CAI 0.5°±0.3°), late-stance (52-60%, control 0.5°±0.3°, CAI 0.3°±0.2°), early-swing (70-78%, control 1.23±0.59, CAI 0.66±0.51) and mid-swing (82-85%, control 3.1°±0.0°, CAI 2.9°±0.1°).

    CONCLUSION: Coupled motion between tibial rotation and rearfoot motion is different in CAI subjects compared to controls during shod and barefoot walking gait. This may be related to internal constraints associated with the condition of CAI. These differences suggest altered movement coordination patterns which may predispose this population to continued issues of ankle instability and further joint changes over their lifetime.

    268 Board #120 May 29, 11:00 AM - 12:30 PM

    Ankle Cryotherapy does Not affect Postural Control in Patients with Chronic Ankle Instability

    Kyung-Min Kim1, Joseph M. Hart2, Susan A. Saliba2, Arthur L. Weltman, FACSM2, Jay Hertel, FACSM2. 1Texas State University, San Marcos, TX. 2University of Virginia, Charlottesville, VA.

    (No relationships reported)

    Application of cryotherapy over a joint has been shown to improve muscle function, yet it is unknown how ankle cryotherapy affects postural control.

    PURPOSE: To determine the effects of a 20-minute focal ankle joint cooling on postural control of unipedal stance in in±dividuals with and without chronic ankle instability (CAI).

    METHODS: Fifteen young subjects with CAI (9 males, 6 females) and 15 healthy gender-matched controls participated. All subjects underwent two intervention sessions on different days in which they had a 1.5L plastic bag filled with either crushed ice (active treatment) or candy corn (sham) applied to the ankle. Postural tasks of quiet unipedal stance with eyes closed for 10 seconds were assessed with a forceplate before and after each intervention. Main outcomes were center of pressure (COP) excursion data used to compute 10 specific postural control measures including: velocity, area, standard deviation (SD), and percent range of COP excursions, and mean and SD of time-to-boundary (TTB) minima in the anterior-posterior (AP) and mediolateral directions. Separate three-way (Group x Intervention x Time) ANOVAs with repeated measures and post hoc simple contrasts were performed for each measure.

    RESULTS: There were no significant interactions or main effects involving intervention (all Ps>0.05). There were group main effects found for mean velocity (F(1,28)=6.46, P=.017), area (F(1,28)=12.83, P=.001), and mean of TTB minima in the AP direction (F(1,28)=5.19, P=.031) indicating that the CAI group demonstrated greater postural instability compared to the healthy group.

    CONCLUSION: Postural control of unipedal stance was not significantly altered following focal ankle joint cooling in groups both with and without CAI. Ankle joint cryotherapy was neither beneficial nor harmful to single leg balance.

    Supported by National Athletic Trainers’ Association Research and Education Foundation Doctoral Grant Program

    269 Board #121 May 29, 11:00 AM - 12:30 PM

    The Effects Of Prophylactic Ankle Supports On Ankle ROM And Isokinetic Torque, Work And Power

    Jamie Garrell, Jacque Jones, Michael R. Torry. Illinois State University, Normal, IL. (Sponsor: Steve Mccaw, FACSM)

    Supported by J. Garrell: Contracted Research - Including Principle Investigator; Research sponsored inpart by a grant from Topical Gear, Michael R Torry = PI.

    PURPOSE: Prophylactic ankle supports are applied to decrease probability of an ankle injury. A common criticism of these supports is that they may possibly decrease the range of motion and (ROM) and plantarflexion-dorsiflexion strength thereby hindering performance. The purpose of this study was to compare isokinetic ankle joint strength (plantarflexion and dorsiflexion torques), total work, and ROM values across two different types of ankle joint protective devices: a) Active Ankle (AA), b) ProTaco (PT) against a no support-control condition.

    METHODS: The subjects were 22 (8 male; 14 female) volunteers (mean age: 20.5 ± 2.3 yrs). The Biodex isokinetic dynamometer system was utilized to measure peak ankle plantarflexion and dorsiflexion isokinetic torque/body weight, total work/body weight, and ROM at 60°/second. Separate RMANOVA with Bonferroni post hoc analyses was applied to each variable to detect differences between conditions (alpha = 0.05).

    RESULTS: Both ankle supports caused a decrease in ROM compared to control (both p < .001); and, the AA produced a greater reduction in ROM compared to PT (p <.004). There was an average 15% decrease in peak plantarflexor torque/BW due to the supports but these reductions were not significant (p = .69). There were no differences in peak dorsiflexor torque/BW (p =.39), dorsiflexor work/BW (p = .09) or average power (p = .64) between conditions.

    CONCLUSIONS: The results of this study suggest that ankle joint prophylactic guards do limit ROM but have little effect on peak plantarflexor or dorsiflexor peak torque, work or power.

    270 Board #122 May 29, 11:00 AM - 12:30 PM

    Differences in Tibiotalar Joint Alignment During Non-loaded and Axial Loaded Condition in Intact Male Feet

    Shuhei Nozaki1, Keigo Taniguchi1, Hiroyuki Takashima2, Kota Watanabe1, Masamitsu Hatakenaka1, Masaki Katayose1. 1Sapporo Medical University, Sapporo, Japan. 2Sapporo Medical University Hospital, Sapporo, Japan.

    (No relationships reported)

    The talus rotates during axial loading relative to the tibia. However, the individual v±ariability in rotation of the talus relative to the tibia at the tibiotalar joint (TTJ) during axial loading hasn’t been evaluated.

    PURPOSE: To evaluate individual variability in degrees and direction of differences in three-dimensional (3D) orientation of talus relative to the tibia at the TTJ in intact feet during an un-loaded and an axial loaded condition using reconstructive 3D MRI data.

    METHODS: Twenty-seven intact feet in either one leg in 27 male subjects with a mean age of 23.1 years were enrolled in this study. 3D orientation of talus relative to the tibia at the TTJ in the un-loaded and the axial loaded condition was calculated analyzing bone models of the TTJ in the two conditions which reconstructed from MRI data. MRI was taken in the un-loaded and 60% body weight axial loaded condition using a loading device. In each condition, subjects kept their ankles in a neutral position. The difference in 3D orientation of the talus relative to the tibia in the un-loaded and the axial loaded condition was calculated using average with the coefficient variation for the analysis of the individual variability in degrees of rotations at the TTJ during axial loading. In addition, according to the direction of the rotation of the talus relative to the tibia, 3D rotational patterns at the TTJ during axial loading were determined for the analysis of individual variability in direction of rotations at the TTJ.

    RESULTS: From the unloaded position to the axial loaded position, the talus rotated 0.9±2.1 degrees in plantarflexion(PF), 0.2±0.9 degrees in inversion(IV), and 1.1±0.7 degrees in adduction(ADD) relative to the tibia. The coefficient of variation of these rotations was 2.±3, 5.7, and 0.6, respectively. Six rotational patterns at the TTJ during loading were identified, including patterns of PF/IV/ADD (n=7, 26%), PF/eversion(EV)/ADD (n=6, 22%), PF/unchanged/ADD (n=4, 15%), dorsiflexion(DF)/IV/ADD (n=4, 15%), DF/EV/ADD (n=5, 19%), and unchanged/IV/ADD (n=1, 4%).

    CONCLUSION: Even in the intact feet, there is the individual variability in rotational orientation of the talus relative to the tibia at the TTJ during axial loading. Demonstrating this individual variability would contribute to the basic information for the kinematics of the TTJ.

    271 Board #123 May 29, 11:00 AM - 12:30 PM

    Biomechanical Orthotics Effect on Lower Leg EMG Activity in Sumptomatic Individuals

    Ryan Wedge1, Juan C. Garbalosa2, Donald Kowalsky2. 1University of Pittsburgh, Pittsburgh, PA. 2Quinnipiac University, Hamden, CT.

    (No relationships reported)

    PURPOSE: To determine the effect of orthotics on lower leg muscle EMG during running.

    METHODS: Subjects (n=31) with pain complaints of a nontraumatic, mechanical origin were randomly assigned to receive one of two orthotics, instructed in the use their orthotics and asked to wear them for 5 weeks. After 5 weeks, the subjects’ lower extremity motion and EMG of the posterior (PT) and anterior tibialis (AT), peroneus longus (PL), and gastrocnemius (G) muscles were recorded while running on a treadmill at 5.9 kmh in 3 footwear conditions: barefoot (B), sandal (S), and sandal orthotic (SO). PT and PL and AT and G EMG data were recorded at 4800 Hz using a pair of fine wire and surface electrodes and band pass filtered with a 4th order Butterworth filter with 10 and 1000 and 10 and 350 Hz cutoff frequencies, respectively. The root mean square (RMS) was obtained, the stance phase extracted using the motion data, and time normalized. The S and SO RMS stance data were amplitude normalized using the peak RMS value of the B trials. The integrated EMG (IEMG) during 4 subphases of stance (0-17, 18-50, 51-83, and 84-100%) were obtained. A non parametric ANOVA assessed the effect of footwear and phase on the IEMG. The difference between the SO and S conditions within an orthotic group and phase and between the 2 orthotic groups within a phase for the SO condition was determined by post hoc multiple comparison testing.

    RESULTS: Although a significant effect of footwear and phase (p < .001) was noted, none of the comparisons of interest were significant (p > .05).

    CONCLUSIONS: Orthotics do not appear to affect the IEMG of the TA, PT, PL, or G during the stance phase of running.

    272 Board #124 May 29, 11:00 AM - 12:30 PM

    Longitudinal Foot Arch Characteristics In Underweight, Normal Weight And Obese Children Aged 1-13 Years

    Steffen Mueller, Juliane Mueller, Anja Carlsohn, Uta Pakusch, Frank Mayer. University Outpatient Clinic, Potsdam, Germany.

    (No relationships reported)

    Overweight is often associated with reduced musculoskeletal function. Whether the relative body weight affects the characteristics of the

    longitudinal foot arch during gait in children is unknown.

    PURPOSE: To examine the effect of underweight, normal weight, overweight and obesity on longitudinal foot arch characteristics in gait for children aged 1-13yrs.

    METHODS: 7787 children (m/f: n=3734/4053; 1.23±0.20m; 27.2±11.2kg; BMI: 17.1±2.4kg/m2) were included into the study. Anthropometrics were assessed and based on body mass index (BMI), children were categorized according to BMI percentiles (for age and gender) in underweight (<3rd percentile; n=37), normal weight (≥3rd and <90th percentile; n=6602), overweight (≥90rd and <97th percentile; n=768) and obese (>97th percentile; n=380) children. Plantar pressure data was assessed on an instrumented walkway during gait with self selected walking velocity [m/s]. For main outcome measure arch index (AI; ratio of: midfoot contact area / ∑rear-, mid-, forefoot contact area [a.u.]) was calculated from plantar pressure data. Data was analyzed descriptively (mean ± SD) followed by ANOVA for group differences according to BMI categorization (underweight, normal weight, overweight, obesity) and for age group 1 to 13yrs (post hoc Tukey Kramer; α=0.05). According to the small number of underweight children, no group differences were analyzed in single age groups.

    RESULTS: Mean walking velocity was 0.95±0.25m/s. For all children smallest AI was seen for underweight (0.18±0.08) followed by normal weight (0.21±0.07), overweight (0.24±0.06) and highest AI for obese children (0.26±0.05; p<0.05). In single age groups (1-13yrs) normal weight children always presented smaller AI than overweight and obese children. This differences (normal weight/overweight) were statistically significant for age groups 5 to 13yrs (p<0.05), but not for children aged 1 to 4yrs (p>0.05).

    CONCLUSION: The results show reduced longitudinal foot arch in overweight and obese children. Therefore, overweight children do not compensate the weight by passive and active foot structures in gait. Additionally, these findings suggest age dependent differences to be discussed in the context of foot development in children.

    273 Board #125 May 29, 11:00 AM - 12:30 PM

    Quantification of the Returned Force in the Arch During Barefoot Running

    Emily L. Martin, Michael J. Maxwell, John E. Davis. Alma College, Alma, MI.

    (No relationships reported)

    Several recent studies have raised the question of how much force can be returned into the stride as the arch stores energy by acting as a spring. It has been suggested that in order to quantify a large portion of this force that is contributed by the arch, the quantification of the restoring force for the deflection of the plantar aponeurosis would be important.

    PURPOSE: The purpose of this study was to determine a way to quantify the returned force in the arch during barefoot running.

    METHODS: Eighteen subjects (20.6±1.3yrs, 73.1±8.6kg and 69.3±3.2in) were videotaped running over a flat surface wearing reflective markers placed at key locations along the medial arch. A motion analysis system was used to record the deflection of the arch (Innovision Sytems Inc.). The force contributed to the stride due to stretching within the plantar aponeurosis is equal to the restoring force. Where Y is the Young’s Modulus, w is the width of the plantar aponeurosis, t is the thickness of the plantar aponeurosis, L is the length of the plantar aponeurosis, and d is the deflection in the arch as measured at mid-stance. The reference value of 1.7 mm was held constant for the plantar aponeurosis thickness. A reference value of 350 MPa was used as the Young’s Modulus. The length and width of the plantar aponeurosis was determined by anthropometric measurements of the foot.

    RESULTS: The deflection of the arch, though small, could be quantified by use of the motion analysis system. An average of 0.028764 + 0.010477 N (kg. m/s2) was quantified as the restoring force in the plantar aponeurosis which may represent the majority of the force contributed into the stride due to the deflection of the arch.

    CONCLUSIONS: The technique proposed in this study provides a way to calculate the returned force. A greater restoring force of the plantar aponeurosis suggests that there might be a greater efficiency due to less musculoskeletal force needed to generate the equivalent total force output. The plantar aponeurosis might be the major contributing source of force from the arch into the stride, but other sources of restoring force such as surrounding bones and musculature might also contribute to the force.

    274 Board #126 May 29, 11:00 AM - 12:30 PM

    Arch Height Changes After 10-week Transition to Minimalist Running Shoes

    Sarah Ridge, Iain Hunter, Ulrike Mitchell, Wayne Johnson. Brigham Young University, Provo, UT. (Sponsor: Gary Mack, FACSM)

    (No relationships reported)

    PURPOSE: Conflicting reports have been presented regarding the relationship of arch height to injury rate in runners. It is theorized that running barefoot causes an increase in activity of the foot muscles and may result in an increase in arch height and, therefore, a decrease in the rate of knee, soft tissue, and/or medial injuries. The purpose of this study was to determine if transitioning to minimalist running shoes has an effect on arch height in experienced recreational runners.

    METHODS: Thirty nine experienced recreational runners, ages 18-45, participated in this study. All runners had been running 15-30 miles per week for the past 6 months and were free from lower extremity injury. Arch height (AH) was measured from both feet of each runner in both standing and neutral positions (foot in subtalar neutral with the knee at a 90 degree angle) using the VariFit Pin-Casting Matrix and Accu-Pin scanner before and after 10 weeks of running. Runners were randomly assigned to the Minimalist (M) or Control (C) group (M n=19, C n=20). The control group was instructed to maintain their typical running regimen for 10 weeks. The minimalist group transitioned from traditional running shoes to minimalist shoes by gradually replacing mileage in traditional shoes with mileage in the minimalist shoes. A mixed model ANOVA was used to analyze differences between groups from pre- to post-tests.

    RESULTS: No significant differences were found between the groups in either foot or position, during both pre- and post-tests - Left Neutral AH (Mpre = 15.5 ± 3.4, Mpost = 14.9 ± 4.1, Cpre = 16.1 ± 2.9, Cpost = 15.8 ± 3.5; p=.77); Left Standing AH (Mpre = 10.6 ± 4.7, Mpost = 10.6 ± 4.5, Cpre = 10.9 ± 2.8, Cpost = 11.3 ± 3.2; p=.73); Right Neutral AH (Mpre = 14.3 ± 3.8, Mpost = 14.7 ± 3.5, Cpre = 15.8 ± 3.8, Cpost = 15.6 ± 2.6; p=.43); Right Standing AH (Mpre = 9.63 ± 3.2, Mpost = 10.0 ± 3.7, Cpre = 9.8 ± 3.2, Cpost = 10.7 ± 3.3; p=.47).

    CONCLUSIONS: Ten weeks of transitioning to minimalist running shoes did not cause a significant change in neutral or standing arch height. The effect of minimalist running on arch height and/or injury rates is either negligible or requires a longer exposure time for significant effects. Further research should be conducted using a population of runners with low arches to see if running in minimalist running shoes is effective in increasing their arch heights.

    275 Board #127 May 29, 11:00 AM - 12:30 PM

    Shod versus Unshod Matched Pair Foot Anthropometry

    Heidi A. Orloff, Paul M. Nakamoto, Justin Y. Higa, Suzanne Gwizdala Schuster, Bryson K. Nakamura, Abby Goss. University of Puget Sound, Tacoma, WA.

    (No relationships reported)

    Footwear are traditionally designed from a single last (sole) that attempts to fit the typical adult male foot. Several studies have shown variations in foot shape between individuals of different races and shod conditions. However racial differences in foot morphology and function have not been recorded on a Samoan population.

    PURPOSE: To determine the differences in foot morphology when a shod (Caucasian) population is matched by gender, age and foot length to an unshod (Samoan) population.

    METHODS: 38 subjects were matched for gender, age (+5 years), and foot length (+2 mm). The mean age of the Caucasian (shod) subjects was 33.3 (12.7) years, while the Samoan (unshod) population had a mean age of 34.1 (14.4) years (p =.512). The mean foot length was 263.8 (15.7) mm for the Caucasians, and 264.0 (15.4) mm for the Samoans (p =.464). After determining that the pairs were matched well, a matched pair t-test (α < .05) was completed for each of 15 variables.

    RESULTS: The Samoan foot was significantly broader, had increased circumferences and a larger toe spread than the Caucasian foot (See Table).

    CONCLUSION: When designing footwear for an unshod population it would be helpful to have ratios specific to the population for a proper fit.

    276 Board #128 May 29, 11:00 AM - 12:30 PM

    Comparison of Anthropometric Foot Characteristics of Samoan and Caucasian Populations

    Justin Y. Higa, Heidi A. Orloff, Paul M. Nakamoto, Suzanne G. Schuster, Bryson K. Nakamura, Abby Goss. University of Puget Sound, Tacoma, WA.

    (No relationships reported)

    Current research has shown gender differences in foot anthropometry. However, it has recently been documented that other factors, such as ethnicity, age, and habitual use of footwear, can also affect foot characteristics.

    PURPOSE: To document foot anthropometry of a Samoan population to assess differences between normative values and a traditionally unshod population.

    METHODS: The subjects in this study consisted of 57 Caucasian women, 39 Samoan women, 49 Caucasian men and 73 Samoan men. A 3-D foot scanner was used to produce 16 anthropometric measurements of the right foot in a half body weight condition. Gender by ethnicity (2×2) ANOVA (α<.05) were completed on the data.

    RESULTS: Female showed a more pronounced difference between ethnicities than their male counterparts in ball of foot height, heel-ankle circumference and ankle circumference (See Table).

    CONCLUSION: Males had significantly larger feet than females, while Samoans had significantly larger feet than Caucasians.

    277 Board #129 May 29, 11:00 AM - 12:30 PM

    Foot Morphology of Samoan Feet Standardized to Foot Length

    Paul M. Nakamoto, Heidi A. Orloff, Justin Y. Higa, Suzanne Gwizdala Schuster, Bryson K. Nakamura, Abby Goss. University of Puget Sound, Tacoma, WA.

    (No relationships reported)

    Samoan populations have unique foot geometry, including flat arches and greater forefoot widths. These characteristics of Samoan foot morphology may have implications on the functionality and performance of the Samoan foot, as foot shape significantly affects foot function.

    PURPOSE: To determine differences between Caucasian foot geometry and Samoan foot geometry.

    METHODS: The subjects in this study consisted of 57 Caucasian women, 39 Samoan women, 49 Caucasian men and 73 Samoan men. A 3-D foot scanner was used to produce 16 anthropometric measurements of the right foot in a half body weight condition. The data was standardized to foot length for comparison across ethnicities and genders (2×2 ANOVA (α < .05)).

    RESULTS: When standardized to foot length, it was evident that the Samoan foot had significantly greater circumference and width ratios than the Caucasian foot (See Table).

    CONCLUSION: The Samoan foot was larger than the Caucasian foot, but not proportionally larger; thus the morphology was different between the ethnicities.

    © 2013 American College of Sports Medicine