Pro Stergiou

Knee Angular Impulse as a Predictor of Patellofemoral Pain in Runners

Background Identification of mechanical factors associated with patellofemoral pain, the most prevalent running injury, is necessary to help in injury prevention, but unfortunately they remain elusive. Hypothesis Runners who develop patellofemoral pain have increased knee joint angular impulse in the frontal plane. Study Design Case control study; Level of evidence, 3. Methods A retrospective study compared knee abduction impulses of 20 patellofemoral pain patients with those of 20 asymptomatic patients. A second prospective study quantified knee angular impulses during the stance phase of running of 80 runners at the beginning of the summer running season. Epidemiologic data were then collected, recording the type and severity of injury of these runners during a 6-month running period. Results The patellofemoral pain patients in the retrospective study had significantly higher (P =. 026) knee abduction impulses (17.0 ± 8.5 Nms) than did the asymptomatic patients (12.5 ± 5.5 Nms). Six patients developed patellofemoral pain during the prospective study. The prospective data showed that patients who developed patellofemoral pain had significantly higher (P =. 042) knee abduction impulses (9.2 ± 3.7 Nms) than did matched patients who remained uninjured (4.7 ± 3.5 Nms). Conclusion The data indicate that increased knee abduction impulses should be deemed risk factors that play a role in the development of patellofemoral pain in runners. Clinical Relevance Footwear and running style can influence knee angular impulse, and the appropriate manipulation of these variables may play a preventive role for patients who are predisposed to patellofemoral pain.

Kinematic Changes After Fusion and Total Replacement of the Ankle Part 1: Range of Motion

Background: The purpose of this study was to determine how closely the present designs of ankle prostheses mimic the unique requirements of the foot and ankle. The three-dimensional range of motion (ROM) of the ankle joint complex, before and after ankle arthrodesis and after implantation of three currently used total ankle prostheses, was investigated. Methods: The three-dimensional ROM was determined in six fresh-frozen cadaver leg specimens using a 6-df device with an axial load of 200 N and a four-camera high-speed video system. A moment of 100 Nm was applied to the footplate to determine the ROM in the sagittal (dorsiflexion and plantarflexion) and frontal (inversion and eversion) planes. The same moment was applied to the tibia to determine the ROM for the internal and external tibial rotation. The measurements were performed for the normal ankle, the fused ankle, and the AGILITY, HINTEGRA, and S.T.A.R. prostheses. Results: Compared to the normal condition, the ROM for dorsiflexion and plantarflexion was changed for all surgical interventions. The changes were highest for the ankle arthrodesis. The changes due to the prostheses were significantly less than the changes due to ankle arthrodesis. Compared to the normal condition, the total ROM for inversion/eversion was slightly decreased by the fused ankle and not changed by the three-component prostheses (HINTEGRA, S.T.A.R.). However, the ROM for inversion/eversion was significantly higher for the two-component prosthesis, AGILITY. The ROM for internal and external tibial rotation was not altered by the AGILITY and HINTEGRA ankle, but it was significantly reduced by the ankle arthrodesis. S.T.A.R. showed a significant shift of the total ROM toward internal tibial rotation. Conclusions: The three tested ankle joint prostheses changed the ROM of the ankle joint complex less than ankle fusion did. Total ankle prostheses were shown to replicate normal joint ROM closely. However, ankle arthrodesis was found to reduce the ROM substantially in all three planes: the sagittal, frontal, and horizontal planes. Clinical Implications: With respect to the ROM, total ankle replacement changes the natural ankle joint condition less than ankle arthrodesis, which reduces the ROM in all three planes and might increase stress in adjacent structures. The prosthesis that replicated the normal ankle joint ROM best was the one with the most anatomical design.

The effect of material characteristics of shoe soles on muscle activation and energy aspects during running

The purposes of this study were (a) to determine group and individual differences in oxygen consumption during heel-toe running and (b) to quantify the differences in EMG activity for selected muscle groups of the lower extremities when running in shoes with different mechanical heel characteristics. Twenty male runners performed heel-toe running using two shoe conditions, one with a mainly elastic and a visco-elastic heel. Oxygen consumption was quantified during steady state runs of 6 min duration, running slightly above the aerobic threshold providing four pairs of oxygen consumption results for comparison. Muscle activity was quantified using bipolar surface EMG measurements from the tibialis anterior, medial gastrocnemius, vastus medialis and the hamstrings muscle groups. EMG data were sampled for 5 s every minute for the 6 min providing 30 trials. EMG data were compared for the different conditions using an ANOVA (alpha=0.05). The findings of this study showed that changes in the heel material characteristics of running shoes were associated with (a) subject specific changes in oxygen consumption and (b) subject and muscle specific changes in the intensities of muscle activation before heel strike in the lower extremities. It is suggested that further study of these phenomena will help understand many aspects of human locomotion, including work, performance, fatigue and possible injuries.

Kinematic changes after fusion and total replacement of the ankle: part 2: Movement transfer.

Introduction: The purpose of this in vitro study was to determine the biomechanical characteristics of the ankle based on the movement transfer between foot and leg before and after ankle arthrodesis, and after implantation of three currently used total ankle prostheses. Methods: A 6-df device with an axial load of 200 N and a four-camera high-speed video system were used for the measurement of the range of motion in six fresh-frozen cadaveric leg specimens. While the foot was moved through the range of dorsiflexion/plantarflexion, the resulting foot eversion/inversion and tibial rotation were recorded. Analogously, the resulting foot eversion/inversion from tibial rotation and, vice versa, the resulting tibial rotation from foot eversion/inversion were determined. The same measurements were performed for the normal ankle, the fused ankle, and after total ankle replacement by the AGILITY, HINTEGRA, and S.T.A.R. prostheses. Results: While in dorsiflexion/plantarflexion of the foot, ankle joint fusion increased the movement transfer to tibial rotation by a 2.4 factor and to eversion/inversion by a 18.5 factor, whereas, this movement transfer did not change for all prostheses conditions. The movement transfer between foot eversion and tibial rotation was found to decrease for all ankle prostheses, but more in the AGILITY and S.T.A.R. prosthesis than in the HINTEGRA. Conclusions: The three tested ankle joint prostheses changed the movement transferred within the ankle joint complex less than ankle fusion did, especially for dorsiflexion/plantarflexion movement of the foot. The closer the design was to the normal anatomy of the ankle, the closer the transfer of movement was shown to be replicated with respect to normal joint. It is suggested that success of total ankle arthroplasty depends on how successfully designs can mimic the movement transfer of the normal ankle, while dissipating the rotational forces and maintaining the stability of the joint.

Kinematic changes after fusion and total replacement of the ankle. Part 3: Talar movement

Introduction: The purpose of this study was to determine talar movement (e.g., talar rotation and talar shift during (dorsiflexion/plantarflexion) with respect to the tibia in the normal ankle, in the fused ankle, and in the replaced ankle by currently used prosthetic designs. Methods: A 6-df device with an axial load of 200 N and a four-camera high-speed video system were used for the measurement of the range of motion in six fresh-frozen cadaveri leg specimens. While moving the foot through the whole range of motion for plantarflexion/dorsiflexion, segmental motion of the marked bones of the foot and shank were measured dynamically. Rotation and medial-lateral shift of the talus were then calculated with regard to flexion position of the foot. Results: In the normal ankle, plantarflexion movement was coupled with talar inversion of 3.5°, and dorsiflexion movement with talar eversion of 1.0°, in totally accounting for 4.5° of talar rotation. While both the HINTEGRA and the S.T.A.R. prostheses did not show changes to the normal condition during the dorsiflexion/plantarflexion cycle (p <.05), talar rotation had a 60% decrease (p <.05) for the AGILITY prosthesis. In the normal ankle joint, a lateral talar shift of 1.4 mm was found to occur during dorsiflexion, and a lateral talar shift of 5.2 mm during plantarflexion. In both, the HINTEGRA and S.T.A.R. ankles, talar shift was converted into medial direction during dorsiflexion of the foot (difference to normal: p <.05), whereas talar shift in the lateral direction was found to occur during plantarflexion of the foot which was comparable to the normal ankle. The AGILITY ankle evidenced an 80% decrease of talar shift (p < .05) during the whole dorsiflexion/plantarflexion cycle. Discussion: The two-component ankle (AGILITY) obviously tends to restrict tremendously talar motion within the ankle mortise, whereas the three-component ankles (HINTEGRA, S.T.A.R.) seem to allow talar range of motion comparable to that in the normal ankle. It is suggested that such a restriction of talar motion results in an increase of stress forces within and around the prosthesis, leading to polyethylene wear and potential loosening at the bone–implant interfaces. Therefore, a successful prosthetic design for the ankle should consist of three components that are shaped as anatomically as possible to provide a normal range of motion and to allow the full transmission of movement transfer between foot and shank and unconstrained movement of the talus within the ankle mortise.

Improved footwear comfort reduces oxygen consumption during running

Footwear comfort has been shown to have an influence on injuries, but it was unknown whether comfort was related to performance. The current study examined the effects of footwear comfort on running economy. Thirteen male participants rated five pairs of shoes on perceived comfort. Oxygen consumption was assessed during steady state runs in the least and most comfortable shoes at slightly above the aerobic threshold. A paired t-test was used to compare running economy in the most versus the least comfortable shoe conditions. The findings of the study indicated a significant improvement in running economy, 0.7% on average, in the most comfortable shoe condition. It is suggested that future study of kinematic and kinetic reactions to footwear of different comfort will help to understand the mechanism for the observed performance improvement.

Validity of a portable force platform for assessing biomechanical parameters in three different tasks

Abstract The aim of this study was to determine the precision and accuracy of the vertical and anterior–posterior force components of the portable PASCO PS-2142 force plate. Impulse, peak force, and time to peak force were assessed and compared to a gold standard force plate in three different tasks: vertical jump, forward jump, and sprint start. Two healthy male participants performed ten trials for each task, resulting in 60 trials. Data analyses revealed good precision and accuracy for the vertical component of the portable force plate, with relative bias and root mean square (RMS) error values nearly the same in all tasks for the impulse, time to peak force, and peak force parameters. Precision and accuracy of the anterior–posterior component were lower for the impulse and time to peak force, with relative bias and RMS error values nearly the same between tasks. Despite the lower precision and accuracy of the anterior–posterior component of the portable force plate, these errors were systematic, reflecting a good repeatability of the measure. In addition, all variables presented good agreement between the portable and gold standard platforms. Our results provide a good perspective for using the aforementioned portable force plate in sports and clinical biomechanics.

Comparison of Polar M600 Optical Heart Rate and Ecg Heart Rate during Exercise

Purpose The purpose of this study was to evaluate the accuracy of the Polar M600 optical heart rate (OHR) sensor compared with ECG heart rate (HR) measurement during various physical activities. Methods Thirty-six subjects participated in a continuous 76-min testing session, which included rest, cycling warm-up, cycling intervals, circuit weight training, treadmill intervals, and recovery. HR was measured using a three-lead ECG configuration and a Polar M600 Sport Watch on the left wrist. Statistical analyses included OHR percent accuracy, mean difference, mean absolute error, Bland–Altman plots, and a repeated-measures generalized estimating equation design. OHR percent accuracy was calculated as the percentage of occurrences where OHR measurement was within and including ±5 bpm from the ECG HR value. Results Of the four exercise phases performed, the highest OHR percent accuracy was found during cycle intervals (91.8%), and the lowest OHR percent accuracy occurred during circuit weight training (34.5%). OHR percent accuracy improved steadily within exercise transitions during cycle intervals to a maximum of 98.5% and during treadmill intervals to a maximum of 89.0%. Lags in HR calculated by the Polar M600 OHR sensor existed in comparison to ECG HR, when exercise intensity changed until steady state occurred. There was a tendency for OHR underestimation during intensity increases and overestimation during intensity decreases. No statistically significant interaction effect with device was found in this sample on the basis of sex, body mass index, V˙O2max, skin type, or wrist size. Conclusions The Polar M600 was accurate during periods of steady-state cycling, walking, jogging, and running, but less accurate during some exercise intensity changes, which may be attributed to factors related to total peripheral resistance changes and pulse pressure.

Kinematic and kinetic analysis of overhand, sidearm and underhand lacrosse shot techniques

ABSTRACT Lacrosse requires the coordinated performance of many complex skills. One of these skills is shooting on the opponents’ net using one of three techniques: overhand, sidearm or underhand. The purpose of this study was to (i) determine which technique generated the highest ball velocity and greatest shot accuracy and (ii) identify kinematic and kinetic variables that contribute to a high velocity and high accuracy shot. Twelve elite male lacrosse players participated in this study. Kinematic data were sampled at 250 Hz, while two-dimensional force plates collected ground reaction force data (1000 Hz). Statistical analysis showed significantly greater ball velocity for the sidearm technique than overhand (P < 0.001) and underhand (P < 0.001) techniques. No statistical difference was found for shot accuracy (P > 0.05). Kinematic and kinetic variables were not significantly correlated to shot accuracy or velocity across all shot types; however, when analysed independently, the lead foot horizontal impulse showed a negative correlation with underhand ball velocity (P = 0.042). This study identifies the technique with the highest ball velocity, defines kinematic and kinetic predictors related to ball velocity and provides information to coaches and athletes concerned with improving lacrosse shot performance.

Validation of a mechanical method for golf footwear stability measurement

Golf swings are performed primarily in the frontal plane, and have been associated with a lateral shift of the body center of mass (Williams and Cavanagh 1983). Using high-speed cinematography, Williams and Cavanagh (1983) showed that, during the followthrough phase after ball impact, as the body center of mass continues travelling laterally toward the target, the front ankle of the golfer experiences a large amount of inversion. Thus, the authors suggested stability as an important feature for golf footwear. Footwear properties can be assessed using mechanical devices or human subjects. The advantages of using mechanical devices over human subjects are the higher repeatability and lower cost. However, in order to provide externally valid measurements, the outcome from a mechanical test must be verified using results from human assessments. To the authors’ knowledge, a validated mechanical testing device to evaluate the stability of golf footwear does not currently exist. Thus the purposes of the current study were to: (1) propose a mechanical device to measure the stability of golf footwear; (2) verify whether differences in footwear stability, measured during human testing, can be reproduced using this mechanical device.