Influences of Patellofemoral Pain and Fatigue in Female Dancers during Ballet Jump-Landing.

This study investigated the influence of patellofemoral pain (PFP) and fatigue on lower-extremity joint biomechanics in female dancers during consecutive simple ground échappé. 3-dimensional joint mechanics were analyzed from the no-fatigue to fatigue conditions. 2-way mixed ANOVAs were used to compare the differences of the kinematic and kinetic variables between groups and conditions. Group main effects were seen in increased jump height (p=0.03), peak vertical ground reaction force (p=0.01), knee joint power absorption (p=0.04), and patellofemoral joint stress (PFJS, p=0.04) for PFP group. Fatigue main effects were found for decreased jump height (p<0.01), decreased ankle plantarflexion at initial foot-ground contact (p=0.01), and decreased ankle displacement (p<0.01). Hip external rotation impulse and hip joint stiffness increased (both p<0.01) while knee extension and external rotation moment, and ankle joint power absorption decreased (p<0.01, p=0.02, p<0.01, respectively) after fatigue. The peak PFJS also decreased after fatigue (p<0.01). Female ballet dancers with PFP sustained great ground impact and loads on the knee probably due to higher jump height compared to the controls. All dancers presented diminished knee joint loading for the protective mechanism and endurance of ankle joint musculature required for the dissipation of loads and displayed a distal-to-proximal dissipation strategy after fatigue.

In-shoe loading in rearfoot and non-rearfoot strikers during running using minimalist footwear.

Recent trends promote a "barefoot" running style to reduce injury. "Minimalist" shoes are designed to mimic the barefoot running with some foot protection. However, it is unknown how "minimalist" shoes alter plantar loading. Our purpose was to compare plantar loads between rearfoot strikers and non-rearfoot strikers after 4 weeks of running in minimalist footwear. 30 females were provided Vibram(®) Bikila shoes and instructed to gradually transition to running in these shoes. Plantar loading was measured using an in-shoe pressure sensor after the 4 weeks. Multivariate analysis was performed to detect differences in loading between rearfoot and non-rearfoot strikers in different plantar regions. Differences in plantar loading occurred between foot strike patterns running in minimalist footwear. Pressure and force variables were greater in the metatarsals and lower in the heel region in non-rearfoot strikers. Peak pressure for the whole foot was greater in non-rearfoot strikers while no difference was observed in maximum force or contact time for the whole foot between strike types. Allowing time for accommodation and adaptation to different stresses on the foot may be warranted when using minimalist footwear depending on foot strike pattern of the -runner.

The effects of running cadence manipulation on plantar loading in healthy runners.

Our purpose was to evaluate effects of cadence manipulation on plantar loading during running. Participants (n=38) ran on a treadmill at their preferred speed in 3 conditions: preferred, 5% increased, and 5% decreased while measured using in-shoe sensors. Data (contact time [CT], peak force [PF], force time integral [FTI], pressure time integral [PTI] and peak pressure [PP]) were recorded for 30 right footfalls. Multivariate analysis was performed to detect differences in loading between cadences in the total foot and 4 plantar regions. Differences in plantar loading occurred between cadence conditions. Total foot CT and PF were lower with a faster cadence, but no total foot PP differences were observed. Faster cadence reduced CT, pressure and force variables in both the heel and metatarsal regions. Increasing cadence did not elevate metatarsal loads; rather, total foot and all regions were reduced when healthy runners increased their cadence. If a 5% increase in cadence from preferred were maintained over each mile run the impulse at the heel would be reduced by an estimated 565 body weights*s (BW*s) and the metatarsals 140-170 BW*s per mile run despite the increased steps taken. Increasing cadence may benefit overuse injuries associated with elevated plantar loading.

Comparison of estimated anterior cruciate ligament tension during a typical and flexed knee and hip drop landing using sagittal plane knee modeling.

Noncontact mechanisms, such as landing from a jump, account for over 70% of all anterior cruciate ligament injuries. Increased knee and hip flexion during landing has been suggested to decrease anterior cruciate ligament tension; however, current literature utilizing knee modeling approaches has not investigated this. Our purpose was to compare estimated anterior cruciate ligament tension in females between a typical and flexed knee and hip drop landing performance. A sagittal plane knee model based on kinematic, kinetic, electromyography, and cadaveric data was used to estimate forces on the anterior cruciate ligament during a typical and flexed drop landing for 23 females. Model estimated peak anterior cruciate ligament tension decreased by 10% during the flexed landing performance (p=0.008). This was accounted for by an increase in hamstring shear force by 6% of body weight and a reduction in patellar tendon shear force and femur-tibia shear force by 3% of body weight each. Results suggest that simple verbal cues for increased knee and hip flexion during landing may be effective in reducing anterior cruciate ligament tension and potential risk of injury during landing.

Lower extremity kinematics and kinetics of Division III collegiate baseball and softball players while performing a modified pro-agility task.

AIM: Females experience at least twice as many non-contact anterior cruciate ligament (ACL) injuries as males. The aim of this study was to investigate if males and females exhibited different characteristics while performing a modified pro-agility test. METHODS: Collegiate Division III male baseball (n=14) and female softball (n=13) players performed 4 trials of a modified pro-agility task, which consisted of running toward a force platform target for 5 steps, planting their right foot, and propelling themselves off of the target with their left foot. Kinematic and kinetic parameters were compared using a multivariate analysis of variance between gender with the level of significance set at P<0.05. RESULTS: Males and females exhibited similar knee valgus angles. Females had a greater maximum knee extension angle (10.14 degrees vs 17.43 degrees ), and greater knee range of motion (46.12 degrees vs 40.12 degrees ). Both groups reached maximum knee flexion at 52% of stance. Females had significantly more maximum hip flexion than males (28.86 degrees vs 22.75 degrees ). Females had significantly smaller minimum internal knee varus moments than their male counterparts (1.12 Nm/kg vs 1.55 Nm/kg). Vertical ground reaction forces as a percentage of bodyweight, and stance time, were not statistically different. The female group displayed an external knee rotation angle (2.49 degrees ) during the beginning of their stance, which was significantly different than the internal rotation angle (4.11 degrees ) in the male group. Early in stance knee rotation angle was highly correlated with the lack of internal knee varus moment (males R(2)=0.75, females R(2)=0.88). CONCLUSION: Females displayed knee moments and kinematics that may place them at greater risk for ACL injury during a stop-cut task. Females should be coached to perform stop cuts with more knee flexion and a more neutral knee rotation angle upon foot contact in an effort to reduce moments that may place the ACL at risk.

Electromyographic activity and applied load during seated quadriceps exercises.

PURPOSE: The aim of this study was to quantify and compare mean quadriceps muscle activity and applied load for eight seated quadriceps exercises using four types of resistance. METHODS: Using surface electromyography (EMG), the right rectus femoris (RF), vastus lateralis (VL), and vastus medialis oblique (VMO) muscles of 52 university students aged 23.5 +/- 3.4 yr (35 female and 17 male subjects) were examined during the exercises. Resistance devices included an ankle weight (78 N), blue Thera-Band tubing, a Cybex 340 isokinetic dynamometer, and an Inertial Exercise Trainer (IET). Electrogoniometer data were collected to determine the range of motion (ROM), angular velocity, and phase (concentric/eccentric) of exercise. Load cell data were analyzed to determine tubing and IET applied loads during exercise. A within-subjects criterion was used to improve intrasubject EMG reliability. All EMG values were normalized to a 100% maximum voluntary isometric contraction. Repeated measures ANOVAs with Bonferroni comparisons were used for statistical analysis. RESULTS: Within-subject effects of muscle and exercise were significant (P < 0.05) for both the concentric and eccentric muscle activity. The interaction effect of mean average EMG amplitude across exercises for the concentric phases of knee extension was significant (P = 0.001). No significant interactions were found for the eccentric phases of all seated quadriceps exercises. None of the exercises selectively isolated the VMO over the VL; however, the VMO/VL ratio was less (P < 0.05) during the concentric phases of the free weight and elastic tubing exercise when compared with the others. Eccentric phase VMO/VL ratios revealed that inertial resistance elicited greater muscle activity than other forms of resistance exercise. CONCLUSION: These findings suggest clinicians should consider biomechanical and resistance data when developing a strengthening program for the quadriceps muscle. Some seated quadriceps exercises may be more appropriate for certain rehabilitation goals than others.

Reliability and running speed effects of in-shoe loading measurements during slow treadmill running.

In-shoe measurement systems allow the clinician and researcher to examine the loading parameters within the shoe. This study sought to investigate the test retest reliability and speed effects of in-shoe loading parameters using the Pedar System (Novel GMBH Munich) during slow treadmill running. The results indicated good to excellent test retest reliability between the two days test-Intraclass correlation coefficients (ICC's) ranged from 0.84-0.99 depending on the plantar region and variable analyzed. All plantar loading variables increased (peak pressure, peak pressure time impulse, peak force, and force time impulse) with the exception of contact area when treadmill running speed was increased from 2.24 m/s to 3.13 m/s. Results indicate that control of running speed is essential in obtaining reproducible data using this system to measure in-shoe loading data.

Plantar loading and cadence alterations with fatigue.

PURPOSE: The purpose of this investigation was to identify changes in loading characteristics of the foot associated with fatigue during running. METHODS: Nineteen healthy subjects ranging from 20 to 30 yr (mean = 22.3, SD = 2.4) were equipped with the Pedar in-shoe measurement system (Novel GmbH) for the assessment of plantar loading. After acclimation to the treadmill, subjects were progressed through the Ohio State protocol for exercise testing until fatigue was reported using Borg's RPE scale. Six right footsteps were recorded at 150 Hz for each subject's comfortable running pace under normal and fatigued conditions. A series of repeated measures multiple analysis of variance was performed for all dependent variables analyzed in this study including peak force (PF), force-time integral (FTI), peak pressure (PP), and pressure-time integral (PTI) for all regions of the plantar surface. RESULTS: Decreased step time, significantly smaller values under the heel for PP, PF, FTI, CT, and PTI, and trends toward increased medial forefoot loading were identified while subjects were running under fatigued conditions (alpha < 0.05). CONCLUSION: These results suggest that subjects change running technique and plantar surface loading characteristics in response to fatigued conditions through increased cadence, decreased loading of the heel, and increased medial forefoot loading.

Seat interface pressures of individuals with paraplegia: influence of dynamic wheelchair locomotion compared with static seated measurements.

OBJECTIVE: To provide a comparison of the seat interface pressures between static seating and dynamic seating during wheelchair locomotion of individuals with paraplegia. DESIGN: Repeated measures multivariate analysis of variance (MANOVA) comparing two conditions: static seat and dynamic seat interface pressures. SETTING: University campus and clinic. PARTICIPANTS: Fifteen participants, each of whom propelled a manual wheelchair for at least 5 hours per week over the previous 6 months and functioned with a spinal cord injury/ disability level of T1 or below. MAIN OUTCOME MEASURES: Peak pressure (PP) and pressure time integral (PTI) as measured by the Novel Pliance System, which consists of a flexible 32 x 32 capacitive sensor mat (each sensor 1.5 cm2) interfaced with a PC, was sampled at 10Hz. The participants were measured in their own wheelchair with a new Jay Active seat cushion. RESULTS: The repeated measures MANOVA showed a difference in the PP and PTI between the static and dynamic measurements (Wilk's = .00, p < .05). Follow-up dependent t tests yielded a difference in PP (t = 5.40, p < 0.025) and no difference in the PTI between static and dynamic conditions (t = 1.45, p > 0.025). The PP during static seating (mean = 16.2 +/- 5.0 kPa [121 +/- 37.5 mmHg]) was less than during dynamic seat interface pressures during wheelchair locomotion (20.03 +/- 6.6 kPa [152.3 +/- 49.5 mmHg]). PP varied by up to 42% during the wheelchair locomotion cycle. The PTI was similar between static (30.1 +/- 9.3 kPa [225.75 +/- 69 mmHg]) and dynamic conditions (36.2 +/- 18.1 kPa [271 +/- 135.7 mmHg]). CONCLUSIONS: The results from this study are consistent with some of the previous work on the nondisabled and a single case study, but with greater external validity because of the nature of the sample chosen and the methodology employed. PPs were greater during dynamic wheelchair locomotion compared with static seating interface pressures, with the peak varying up to 42% during the wheelchair locomotion cycle. The PTI indicates that the cumulative effect of the loading was comparable between conditions. The question that remains is whether this dynamic loading, resulting in a change in PP throughout the cycle, has a significant effect on tissue health.

Reliability of an in-shoe pressure measurement system during treadmill walking.

We examined the reliability of in-shoe foot pressure measurement using the Pedar in-shoe pressure measurement system for 25 participants walking at treadmill speeds of 0.89, 1.12, and 1.34 meters/sec. The measurement system uses EMED insoles, which consist of 99 capacitive sensors, sampled at 50 Hz. Data were collected for 20 seconds at two separate times while participants walked at each gait speed. Differences in some of the loading variables across speed relative to the total foot and across the different anatomical regions were detected. Different anatomical regions of the foot were loaded differently with variations in walking speed. The results indicated the need to control speed when evaluating loading parameters using in-shoe pressure measurement techniques. Coefficients of reliability were calculated. Variables such as peak force for the total foot required two steps to achieve a coefficient of reliability of 0.98. To achieve excellent reliability (> 0.90) in the peak force, force time integral, peak pressure, and pressure time integral across the total foot and the seven regions, a maximum of eight steps was needed. In general, timing variables, such as the instant of peak force and the instant of peak pressure, tended to be the least reliable measures.

Taping and semirigid bracing may not affect ankle functional range of motion.

The comparative effects of adhesive tape and three semirigid ankle orthoses on ankle functional range of motion were studied on 11 college football athletes. Maximum plantar flexion and maximum dorsiflexion were measured under five conditions to determine functional range of motion. Testing conditions included: control (no supportive device), adhesive tape with moleskin, the Airstirrup "Training" orthosis, the Active Ankle "Trainer" orthosis, and the Ankle Ligament Protector. A 200-Hz video camera was used to record subjects' motions in the sagittal plane while they ran a series of 40-yd sprints. Videotape was analyzed with the Peak Performance Technology Motion Measurement System. Data were analyzed with a Repeated Measures MANOVA. Differences were found among treatments for maximum plantar flexion and functional range of motion. Follow-up analyses indicated that the Ankle Ligament Protector was the only supportive device that was significantly more restrictive than the control. The Airstirrup, Active Ankle, and adhesive tape with moleskin do not significantly affect functional range of motion during running.

Quadriceps angle and rearfoot motion: relationships in walking.

The purpose of this study was to describe the relationship between quadriceps angle (q-angle) and rearfoot motion in walking. Twenty women were videotaped with two cameras, one located behind the subject and one located in front providing both front and rear views of the frontal plane. Each subject was required to walk at a 1.5 mph pace on a treadmill while five consecutive right footfalls were videotaped. After walking, each subject was videotaped in a calibrated stance and a chosen stance. Leg length and hip width were measured. Arch index was measured to determine arch type of the subject. All subjects were required to walk barefoot during testing. All trials were digitized and analyzed using the Peak Performance Motion Measurement System. Q-angles and rearfoot angles were calculated and averaged over the five trials. The following group means were obtained: maximum pronation (MPRO) was -7.88 degrees, total rearfoot motion (TRFM) was 8.20 degrees, static rearfoot angle in a chosen stance (SRFCHOS) was -3.45 degrees, static rearfoot angle in a calibrated stance (SRFCAL) was -2.40 degrees, dynamic q-angle at heel strike (DQHS) was 16.13 degrees, dynamic q-angle at midstance (DQMS) was 16.00 degrees, static q-angle in a chosen stance (SQCHOS) was 18.32 degrees, static q-angle in a calibrated stance (SQCAL) was 17.42 degrees, hip width (HWIDTH) was 25.66cm, leg length (LLENGTH) was 85.76cm and arch index was 0.23cm2. Pearson product moment correlations were calculated between each of the variables. All of the q-angle variables, both static and dynamic, correlated poorly with rearfoot motion variables.(ABSTRACT TRUNCATED AT 250 WORDS)

Foot placement angle and arch type: effect on rearfoot motion.

The purpose of the study was to describe the relationship between foot placement angle, arch type, and rearfoot motion during running. Twenty women were filmed in the frontal plane at 100 fps. Subjects displaying a variety of foot placement angles were chosen. Before data collection, arch indices were calculated. Each subject ran five trials at a pace of 3.5 m/sec. All subjects wore the same type of shoe. All trials were digitized to determine rearfoot angles throughout foot contact. The following mean values were obtained: total rearfoot was 10.09 degrees, maximum pronation was -9.63 degrees, foot placement angle was 7.58 degrees and arch index (AI) was 0.23 cm2. Non-linear regression was used to predict the relationship between maximum pronation and total rearfoot motion using foot placement angle and AI. Foot placement angle was the best single predictor of total rearfoot motion. When using both foot placement angle and arch type as predictors of total rearfoot motion, r2 was .35. Less abduction was associated with more total rearfoot motion. Arch type exhibited a quadratic relationship with total rearfoot motion. Normal-arched individuals (.21 cm2 less than AI less than .26 cm2) exhibited less total rearfoot motion than high-arched (AI greater than .26 cm2) and flat-arched (AI less than .21 cm2) individuals. For maximum pronation, foot placement angle was the only significant predictor (r2 = .13). Greater foot placement angles (more abduction) were associated with less maximum pronation.