Background: Bone fatigue resistance and more generally the ability to dissipate the stress sustained in dynamic tasks are partly affected by tissue properties. Men and women demonstrate substantial differences in body composition. Research question: To assess whether gender, as a function of body composition, affects impact-related parameters in running. Methods: A qualitative study has been conducted. Twelve females and eighteen males performed four 2-min running trials at 2.8 m.s (-1), 3.3 m.s(-1), 3.9 m.s(-1), and 4.4 m.s(-1) while recording axial and transverse tibial acceleration. Peak acceleration and power spectral density within the impact-related frequency range (vibration content) were measured. Bone mineral content, fat mass, lean mass, and muscle mass were assessed using an impedance meter. Two-way (gender x speed) ANOVAs were computed. Multiple linear regressions were then used to assess the magnitude of the effect of body composition indicators on impact-related parameters. Results: Significant gender and speed effects were observed. Females and high running speeds were associated with greater peak acceleration and vibration content at the tibia. Small interactions were observed between muscle mass and axial peak acceleration and vibration content, and between bone mineral content and transverse peak acceleration and vibration content, and axial vibration content. Significance: Women demonstrated greater mechanical stress than men during running. High mechanical stress was associated with low bone mineral content and muscle mass. These findings may have implications in the prevention and management of bone overuse injuries in runners.

Background Orthotic heel lifts are thought to lower tension in the Achilles tendon, but the evidence supporting this is equivocal. Objective To investigate the effect of a 12 mm in-shoe orthotic heel lift on Achilles tendon loading using transmission mode ultrasonography. Design Controlled study. Setting Laboratory. Patients (or Participants) 12 active males. Interventions (or Assessment of Risk Factors) The propagation speed of ultrasound, which is governed by the elastic modulus and density of tendon and proportional to the tensile load to which it is exposed, was measured in 12 recreationally active men, during shod treadmill walking at matched speeds (3.4 +/− 0.7 km/h), with and without the addition of a heel lift. Vertical ground reaction forces and spatiotemporal gait parameters were simultaneously recorded. Data were acquired at 100 Hz during 10 seconds of steady state walking. Main Outcome Measurements Ultrasound transmission speed maxima (P1, P2) and minima (M1,M2) in the Achilles tendon, vertical ground reaction force peaks, step length, and cadence. Results Ultrasound transmission speed in the Achilles tendon was characterised by 2 maxima (P1,P2) and minima (M1,M2) during walking. Addition of a heel lift to footwear resulted in a 2% increase and a 2% decrease in the first vertical ground reaction force peak and the local minimum respectively (P< 0.05). Ultrasonic velocity in the Achilles tendon (P1, P2, M2) was significantly lower with the addition of an orthotic heel lift (P<0.5). Conclusions Peak ultrasound transmission speed in the Achilles tendon was lower with the addition of a 12 mm orthotic heel lift, indicating that the heel lift reduced tensile load in the Achilles tendon, thereby counteracting the effect of footwear observed in previous studies. These findings support the addition of orthotic heel lifts to footwear in the rehabilitation of Achilles tendon disorders where management aims to lower tension within the tendon.

Muscle activity is tuned in response to ground reaction force to dampen soft-tissue vibrations (Wakeling, Von Tscharner, Nigg, & Stergiou, 2001) during whole-body vibrations (Wakeling, Nigg, & Rozi...

- Study Design Controlled laboratory study - Objective To investigate the effect of a 12–mm in–shoe orthotic heel lift on Achilles tendon loading during shod walking using transmission–mode ultrasonography. - Background Orthotic heel lifts are thought to lower tension in the Achilles tendon but evidence for this effect is equivocal. - Methods The propagation speed of ultrasound, which is governed by the elastic modulus and density of tendon and is proportional to the tensile load to which it is exposed, was measured in the right Achilles tendon of twelve recreationally–active males during shod treadmill walking at matched speeds (3.4±0.7 km/h), with and without addition of a heel lift. Vertical ground reaction force and spatiotemporal gait parameters were simultaneously recorded. Data were acquired at 100Hz during 10s of steady–state walking. Statistical comparisons were made using paired t–tests (α=.05). - Results Ultrasound transmission speed in the Achilles tendon was characterized by two maxima (P1, P2) and minima (M1, M2) during walking. Addition of a heel lift to footwear resulted in a 2% increase and 2% decrease in the first vertical ground reaction force peak and the local minimum, respectively (P<.05). Peak ultrasonic velocity in the Achilles tendon (P1, P2, M2) was significantly lower with addition of an orthotic heel lift (P<.05). - Conclusions Peak ultrasound transmission speed in the Achilles tendon was lower with the addition of a 12–mm orthotic heel lift, indicating the heel lift reduced tensile load in the Achilles tendon, thereby counteracting the effect of footwear. These findings support the addition of orthotic heel lifts to footwear in the rehabilitation of Achilles tendon disorders where management aims to lower tension within the tendon. - Level of Evidence Therapy, level 2a

STUDY DESIGNControlled laboratory study.BACKGROUNDOrthotic heel lifts are thought to lower tension in the Achilles tendon, but evidence for this effect is equivocal.OBJECTIVETo investigate the effect of a 12-mm, in-shoe orthotic heel lift on Achilles tendon loading during shod walking using transmission-mode ultrasonography.METHODSThe propagation speed of ultrasound, which is governed by the elastic modulus and density of tendon and proportional to the tensile load to which it is exposed, was measured in the right Achilles tendon of 12 recreationally active men during shod treadmill walking at matched speeds (3.4 ± 0.7 km/h), with and without addition of a heel lift. Vertical ground reaction force and spatiotemporal gait parameters were simultaneously recorded. Data were acquired at 100 Hz during 10 seconds of steady-state walking. Statistical comparisons were made using paired t tests (α = .05).RESULTSUltrasound transmission speed in the Achilles tendon was characterized by 2 maxima (P1, P2) and minima (M1, M2) during walking. Addition of a heel lift to footwear resulted in a 2% increase and 2% decrease in the first vertical ground reaction force peak and the local minimum, respectively (P<.05). Ultrasonic velocity in the Achilles tendon (P1, P2, M2) was significantly lower with the addition of an orthotic heel lift (P<.05).CONCLUSIONPeak ultrasound transmission speed in the Achilles tendon was lower with the addition of a 12-mm orthotic heel lift, indicating that the heel lift reduced tensile load in the Achilles tendon, thereby counteracting the effect of footwear observed in previous studies. These findings support the addition of orthotic heel lifts to footwear in the rehabilitation of Achilles tendon disorders where management aims to lower tension within the tendon.

Introduction Footwear remains a prime candidate for the prevention and rehabilitation of Achilles tendinopathy. Elevation of the heel with footwear has been suggested to decrease tensile load in the Achilles tendon, however evidence for this effect is equivocal (Reinschmidt et al. 1995). Studies on the internal loading of the Achilles tendon are typically invasive or not suitable for field settings (Komi, 1990). Acoustic transmission, however, has the potential to provide non-invasive estimates of tendon loading and has been widely used to evaluate the mechanical properties of human bone in vivo (Langton et al. 1999). Animal studies have also confirmed that acoustic transmission is governed by the density and bulk modulus of tendon and is proportional to the tensile load to which it is exposed (Pourcelot et al. 2005).

BACKGROUNDFootwear remains a prime candidate for the prevention and rehabilitation of Achilles tendinopathy because it is thought to decrease tension in the tendon through elevation of the heel. However, evidence for this effect is equivocal.PURPOSEThis study used an acoustic transmission technique to investigate the effect of running shoes on Achilles tendon loading during barefoot and shod walking.METHODSAcoustic velocity was measured in the Achilles tendon of 12 recreationally active males (age, 31 ± 9 yr; height, 1.78 ± 0.06 m; weight, 81.0 ± 16.9 kg) during barefoot and shod walking at matched self-selected speed (3.4 ± 0.7 km·h). Standard running shoes incorporating a 10-mm heel offset were used. Vertical ground reaction force and spatiotemporal parameters were determined with an instrumented treadmill. Axial acoustic velocity in the Achilles tendon was measured using a custom-built ultrasonic device. All data were acquired at a rate of 100 Hz during 10 s of steady-state walking. Statistical comparisons between barefoot and shod conditions were made using paired t-tests and repeated-measure ANOVA.RESULTSAcoustic velocity in the Achilles tendon was highly reproducible and was typified by two maxima (P1, P2) and minima (M1, M2) during walking. Footwear resulted in a significant increase in step length, stance duration, and peak vertical ground reaction force compared with barefoot walking. Peak acoustic velocity in the Achilles tendon (P1, P2) was significantly higher with running shoes.CONCLUSIONSPeak acoustic velocity in the Achilles tendon was higher with footwear, suggesting that standard running shoes with a 10-mm heel offset increase tensile load in the Achilles tendon. Although further research is required, these findings question the therapeutic role of standard running shoes in Achilles tendinopathy.

Introduction: Prospective studies using the Foot Posture Index (FPI) in athletic and military populations have demonstrated that abnormal foot posture increases the risk of lower extremity injury. However, other research has shown that the FPI has reduced validity and inter-rater reliability. With recent studies demonstrating that the Microsoft Kinect can obtain some biomechanical data with similar accuracy to 3D motion analysis (3DMA) and scanning systems, the Kinect has the potential to evaluate static foot posture with more accuracy than subjective tools such as the FPI. Therefore, the aim of this study was to evaluate whether the Kinect is able to accurately and reliably evaluate static foot posture, compared to visual and 3DMA assessments of the FPI.Methods: The static foot posture of 30 males was assessed over two sessions using three methods; a traditional visual assessment, a 3DMA system and the Kinect. Spearman's rho was used to assess the intra-rater reliability of the three methods and to evaluate the concurrent validity of each. Linear regression was used to examine the Kinect's ability to predict total visual FPI score.Results: Four Kinect FPI items demonstrated moderate to good intra-rater reliability (rho = 0.62–0.78) whereas all visual FPI items demonstrated poor to moderate intra-rater reliability (rho = 0.17–0.63). Comparison to FPI items obtained using the 3DMA system revealed four Kinect FPI items possessed moderate to good validity (rho = 0.51–0.85) whereas all visual FPI items showed poor correlations with both the 3DMA and Kinect (absolute rho = 0.01–0.44). The Kinect items that demonstrated moderate to good reliability were able to predict 61% of the variance in the total visual FPI score.Discussion: This study found that the majority of the FPI items derived using the Kinect were reliable and valid when compared to a 3DMA system. In contrast, poor reliability and validity was shown for the visual inspection of FPI. Kinect FPI items were also able to predict a moderate degree of variance in the total visual FPI score. The increased reliability and validity demonstrated by the Kinect may be credited to the instrument's continuous data which, when compared with the limited ordinal scale of the FPI, could allow for improved accuracy in foot posture evaluation. These results suggest that the inexpensive and portable Kinect system has the potential to accurately evaluate static foot posture in a clinical setting. Introduction: Prospective studies using the Foot Posture Index (FPI) in athletic and military populations have demonstrated that abnormal foot posture increases the risk of lower extremity injury. However, other research has shown that the FPI has reduced validity and inter-rater reliability. With recent studies demonstrating that the Microsoft Kinect can obtain some biomechanical data with similar accuracy to 3D motion analysis (3DMA) and scanning systems, the Kinect has the potential to evaluate static foot posture with more accuracy than subjective tools such as the FPI. Therefore, the aim of this study was to evaluate whether the Kinect is able to accurately and reliably evaluate static foot posture, compared to visual and 3DMA assessments of the FPI. Methods: The static foot posture of 30 males was assessed over two sessions using three methods; a traditional visual assessment, a 3DMA system and the Kinect. Spearman's rho was used to assess the intra-rater reliability of the three methods and to evaluate the concurrent validity of each. Linear regression was used to examine the Kinect's ability to predict total visual FPI score. Results: Four Kinect FPI items demonstrated moderate to good intra-rater reliability (rho = 0.62–0.78) whereas all visual FPI items demonstrated poor to moderate intra-rater reliability (rho = 0.17–0.63). Comparison to FPI items obtained using the 3DMA system revealed four Kinect FPI items possessed moderate to good validity (rho = 0.51–0.85) whereas all visual FPI items showed poor correlations with both the 3DMA and Kinect (absolute rho = 0.01–0.44). The Kinect items that demonstrated moderate to good reliability were able to predict 61% of the variance in the total visual FPI score. Discussion: This study found that the majority of the FPI items derived using the Kinect were reliable and valid when compared to a 3DMA system. In contrast, poor reliability and validity was shown for the visual inspection of FPI. Kinect FPI items were also able to predict a moderate degree of variance in the total visual FPI score. The increased reliability and validity demonstrated by the Kinect may be credited to the instrument's continuous data which, when compared with the limited ordinal scale of the FPI, could allow for improved accuracy in foot posture evaluation. These results suggest that the inexpensive and portable Kinect system has the potential to accurately evaluate static foot posture in a clinical setting.

The evaluation of foot posture in a clinical setting is useful to screen for potential injury, however disagreement remains as to which method has the greatest clinical utility. An inexpensive and widely available imaging system, the Microsoft Kinect™, may possess the characteristics to objectively evaluate static foot posture in a clinical setting with high accuracy. The aim of this study was to assess the intra-rater reliability and validity of this system for assessing static foot posture.

Introduction: Recent debate surrounding the use of athletic footwear with elevated cushioned heels highlights the lack of knowledge regarding the effect of small changes in midsole heel height (MHH) on lower extremity biomechanical data. Consequently, the aim of this study was to examine the effect of walking in two identical shoes with different MHHs (10 mm and 13 mm), and compare these to walking in a racing flat (4 mm).

This case study reports the kinematic effect of 2 different cricket shoes on a fast bowler who reports a history of posterior ankle joint impingement. The participant bowled 6 trials in 2 pairs of cricket shoes. The 3-dimensional kinematics of the joints of the front leg was quantified during stance phase of the delivery stride. Wearing the high-cut shoe resulted in the ankle being 7.7-degree angle more plantarflexed at initial contact compared with the low-cut shoe. Again, when wearing the high-cut shoe compared with the low-cut shoe, the ankle joint was 15.5-degree angle more adducted and the knee was 4.1-degree angle less externally rotated at initial contact. This case study identifies the bowler's preferred shoe (high-cut shoe) as a potential contributing factor to the symptoms he was experiencing.

Methods The midfoot kinematics of 21 males were recorded whilst walking in a neutral shoe, a neutral shoe with a foot orthotic and a neutral shoe with nodules located on the plantar medial aspect of the foot (experimental shoe). Electromyography of the peroneus longus, tibialis anterior and medial gastrocnemius was also recorded and analysed. A Friedman’s ANOVA was used to evaluate differences between shoe conditions, and a Wilcoxon signed ranks test was conducted to establish where the differences occurred.

Background: The relationship between the phases of the menstrual cycle and injury risk remains unclear. Neuromuscular function may be compromised during menstruation, which could result in reduced cyclicality of movement patterns. We hypothesize that mediolateral (varus/valgus) knee acceleration during running gait will possess increased variability during menstruation when compared to approximate to ovulation in women who do not take the monophasic oral contraceptive pill (MOCP).Methods: Thirty-six women (18 MOCP users: MOCP group and 18 non-pill users: NP group) performed six-minute treadmill running trials at 10 km h(-1) with an accelerometer fixed to the proximal tibia. Trials were performed at menstruation and ovulation (for the MOCP group at a similar stage of the cycle) in a randomized order. The cyclicality of gross mediolateral tibial acceleration during 15 consecutive strides was assessed using combined wavelet and autocorrelation analysis. Longitudinal and anteroposterior accelerations were also examined. Repeated measures analysis of variance (ANOVA) tests were performed to assess differences at each stage of the menstrual cycle (alpha = 0.05).Findings: Gross mediolateral acceleration in the NP group had significantly (P=0.022) increased variability at the time of menstruation compared to ovulation, and was also significantly (P=0.011) more variable than the MOCP group at the corresponding time point. No significant difference was observed for any measure in the MOCP group.Interpretation: Increased variability in the NP users at menstruation may be a result of compromised motor control strategies. This provides further evidence of variability in performance and motor control during menstruation, and may have implications for a female athlete's risk of injury. (C) 2010 Elsevier Ltd. All rights reserved.

Excessive foot pronation has been associated with injuries of the lower extremity. No research has investigated the effect of enhancing plantar sensory feedback on foot pronation. The aim of this study was to determine whether a shoe with enhanced plantar sensory feedback reduces midfoot pronation. Midfoot kinematics and electromyography of the peroneus longus, tibialis anterior and medial gastrocnemius of 21 males (age: 21.0 ± 4.0 years, height: 176.8 ± 5.0 cm, mass: 73.3 ± 6.5 kg) were recorded whilst walking in a neutral shoe, a neutral shoe with a prefabricated foot orthotic and a neutral shoe with nodules located on the plantar-medial insole (experimental shoe). Friedman's ANOVA and Wilcoxon tests were used to evaluate differences between shoe conditions. Mean midfoot-tibia angles during ground contact were significantly more supinated when wearing the experimental shoe (+7.14°, p = 0.023) or orthotic (+3.83°, p = 0.006) compared to the neutral shoe. During the loading phase, midfoot angles were significantly more supinated when wearing the experimental shoe compared to the orthotic (+5.53°, p = 0.008) or neutral shoe (+6.20°, p = 0.008). In the midstance phase, midfoot supination was significantly higher in the orthotic compared to the neutral shoe (+2.79°, p = 0.006). Finally, supination was increased during the propulsive phase when wearing the experimental shoe compared to the orthotic (+7.43°, p = 0.010) or neutral shoe (+10.83°, p = 0.009). No significant (p < 0.05) differences in muscle activation were observed. These results suggest that increasing plantar sensory feedback to the medial aspect of the foot reduces midfoot pronation during an acute bout of walking. Further work is needed to explore whether these effects remain over longer time periods.

Estrogen receptors in skeletal muscle suggest a tissue-based mechanism for influencing neuromuscular control. This has important physiological implications for both eumenorrheic women with fluctuating estrogen levels and those with constant and attenuated estrogen levels, i.e., women using the monophasic oral contraceptive pill (MOCP). This study examined the effects of endogenous plasma estrogen levels on leg stiffness (K LEG) and foot center of pressure (COP) during hopping. Nineteen females (Age = 28.0 ± 4.2 years, Ht = 1.67 ± 0.07 m, Mass = 61.6 ± 6.8 kg) who had been using the MOCP for at least 12 months together with 19 matched, female, non-MOCP users (Age = 31.9 ± 7.3 years, Ht = 1.63 ± 0.05 m, Mass = 62.5 ± 5.9 kg) participated. Non-MOCP users were tested at the time of lowest (menstruation) and highest (≈ovulation) estrogen whilst MOCP users were tested at Day 1 and Day 14 of their cycle. At each test session, K LEG (N m−1 kg−1) and foot COP path length (mm) and path velocity (mm s−1) were determined from ground reaction force data as participants hopped at 2.2 Hz on a force plate. Statistical analysis revealed no significant (p < 0.05) differences for K LEG. In contrast, significantly higher COP path length (30%) and COP path velocity (25%) were identified at ≈ovulation compared to menstruation in the non-MOCP users. Whilst there was no evidence of an estrogen-induced effect on K LEG; significantly elevated estrogen at ≈ovulation presumably increased extensibility of connective tissue and/or diminished neuromuscular control. Consistent lower limb dynamics of MOCP users demands less reliance on acutely modified neuromuscular control strategies during dynamic tasks and may explain the lower rate of lower limb musculoskeletal injuries in this population compared to non-MOCP users.

"Study to characterise the biomechanical variability in different styles of initial foot contact during running." Footwear Science, 3(sup1), pp. S20–S21

Introduction: The mechanical effect of footwear construction and custom modification common to fast bowling in cricket is poorly understood. The aim of this study was to investigate the effect of three cricket shoes commonly used by elite male fast bowlers on lower limb biomechanics in the delivery stride, which included two bowling shoes from different lasts and a custom modified shoe. Methodology: Four male cricket fast bowlers were included in the study. A 20 camera VICON Mx system was used to collect three-dimensional kinematic data of the lower limb at 250 Hz. A 6DOF marker set was used to track and model the lower limb. Four 0.6 × 0.9 m piezoelectric force platforms (Type 9287 BA, Kistler) were positioned at both back and front foot strike to capture kinetic data. The force platform data were sampled at 1000 Hz. Six successful trials were analysed for each bowling condition. Each bowler bowled in three different shoes; 2 commercially available cricket shoes (ASICS 170no and ASICS Gel Strike Rate) and 1 modified Cross Trainer (ASICS Gel 490TR). Freidman two-way ANOVA with post hoc pairwise comparison was used to analyse the differences between shoes. Results: A significant difference was not identified between shoes for any backfoot strike variables. The peak front foot lateral GRF was significantly different between shoes (P < 0.05). Post-hoc pairwise comparison identified an increased lateral force of 0.7 BW in the 490TR relative to the 170no (P = 0.022). The front foot peak knee angular velocity in the sagittal plane and front knee varus/valgus angle at initial contact were both significant (P < 0.05) between shoes. Post-hoc pairwise comparison identified a significant decrease in coronal plane knee joint angle at initial contact between the 490TR and Strike Rate from a neutral knee joint angle by 3° towards varus (P = 0.008) and a significant decrease of 115°/s in maximum front knee sagittal plane angular velocity between the 490TR and the Strike Rate (P = 0.022). The peak front foot torsional knee joint moment was significantly different (P = 0.022) between footwear. Post-hoc pairwise comparison identified an increase in extension moment in the 490TR by 0.08 Nm/kg relative to the 170no (P = 0.008). Conclusion: This study presents pilot data for quantifying the effects of footwear on lower limb biomechanics during the fast bowling delivery stride. Further research is required to identify the clinical significance of these findings. Introduction: The mechanical effect of footwear construction and custom modification common to fast bowling in cricket is poorly understood. The aim of this study was to investigate the effect of three cricket shoes commonly used by elite male fast bowlers on lower limb biomechanics in the delivery stride, which included two bowling shoes from different lasts and a custom modified shoe. Methodology: Four male cricket fast bowlers were included in the study. A 20 camera VICON Mx system was used to collect three-dimensional kinematic data of the lower limb at 250 Hz. A 6DOF marker set was used to track and model the lower limb. Four 0.6 × 0.9 m piezoelectric force platforms (Type 9287 BA, Kistler) were positioned at both back and front foot strike to capture kinetic data. The force platform data were sampled at 1000 Hz. Six successful trials were analysed for each bowling condition. Each bowler bowled in three different shoes; 2 commercially available cricket shoes (ASICS 170no and ASICS Gel Strike Rate) and 1 modified Cross Trainer (ASICS Gel 490TR). Freidman two-way ANOVA with post hoc pairwise comparison was used to analyse the differences between shoes. Results: A significant difference was not identified between shoes for any backfoot strike variables. The peak front foot lateral GRF was significantly different between shoes (P < 0.05). Post-hoc pairwise comparison identified an increased lateral force of 0.7 BW in the 490TR relative to the 170no (P = 0.022). The front foot peak knee angular velocity in the sagittal plane and front knee varus/valgus angle at initial contact were both significant (P < 0.05) between shoes. Post-hoc pairwise comparison identified a significant decrease in coronal plane knee joint angle at initial contact between the 490TR and Strike Rate from a neutral knee joint angle by 3° towards varus (P = 0.008) and a significant decrease of 115°/s in maximum front knee sagittal plane angular velocity between the 490TR and the Strike Rate (P = 0.022). The peak front foot torsional knee joint moment was significantly different (P = 0.022) between footwear. Post-hoc pairwise comparison identified an increase in extension moment in the 490TR by 0.08 Nm/kg relative to the 170no (P = 0.008). Conclusion: This study presents pilot data for quantifying the effects of footwear on lower limb biomechanics during the fast bowling delivery stride. Further research is required to identify the clinical significance of these findings.