The influence of midsole horizontal and vertical deformation on soft tissue vibrations and bone acceleration during running.

Increased midsole deformation can limit exposure to high impact and vibration magnitudes while running. The aim of this study was to evaluate the effect of shoes eliciting different midsole deformation on ground reaction forces, heel impact, soft tissue vibrations and bone vibrations. Forty-eight runners performed a 5-min running task on an instrumented treadmill at a self-selected pace with four different shoes. Midsole horizontal and vertical deformations were quantified with relative displacement of seven reflective markers placed on the midsole of the shoe and tracked by eight optoelectronic cameras. Heel impacts, soft tissue and bone vibrations of lower leg muscle groups, sacrum and head were quantified with tri-axial accelerometers. Continuous wavelet transform was used to assess magnitude and frequency of the acceleration data. Linear mixed models and non-parametric one-dimensional regressions between the accelerometer data and shoe deformation were performed. Greater horizontal and vertical deformations decreased the magnitude (up to 4.6% per mm) and frequency (up to 0.6 Hz per mm) of soft tissue vibrations and bone accelerations. Accelerations of the heel, tibia, gastrocnemius medialis and vastus lateralis were more influenced than the sacrum and head. Increasing midsole deformation could therefore mitigate the risk of injury, while increasing running comfort and smoothness.

Differences in head impact biomechanics between playing positions in Canadian high school football players.

The objective of this study was to compare head impact magnitudes and time between impacts among positions in Canadian high-school football. Thirty nine players from two high-school football teams were recruited and assigned a position profile: Profile 1 (quarterback, receiver, defensive back, kicker), Profile 2 (linebacker, running back), and Profile 3 (linemen). Players wore instrumented mouthguards to measure peak magnitudes of linear and angular acceleration and velocity for each head impact throughout the season. A principal component analysis reduced the dimensionality of biomechanical variables, resulting in one principal component (PC1) score assigned to every impact. Time between impacts was calculated by subtracting the timestamps of subsequent head impacts within a session. Significant differences in PC1 scores and time between impacts occurred between playing position profiles (ps<0.001). Post-hoc comparisons determined that PC1 was greatest in Profile 2, followed by Profiles 1 and 3. Time between impacts was lowest in Profile 3, followed by Profiles 2 and 1. This study delivers a new method of reducing the multidimensionality of head impact magnitudes and suggests different Canadian high-school football playing positions experience different head impact magnitudes and frequencies, which is important for monitoring concussion and repetitive head impact exposure.

Measuring Gait Velocity and Stride Length with an Ultrawide Bandwidth Local Positioning System and an Inertial Measurement Unit.

One possible modality to profile gait speed and stride length includes using wearable technologies. Wearable technology using global positioning system (GPS) receivers may not be a feasible means to measure gait speed. An alternative may include a local positioning system (LPS). Considering that LPS wearables are not good at determining gait events such as heel strikes, applying sensor fusion with an inertial measurement unit (IMU) may be beneficial. Speed and stride length determined from an ultrawide bandwidth LPS equipped with an IMU were compared to video motion capture (i.e., the "gold standard") as the criterion standard. Ninety participants performed trials at three self-selected walk, run and sprint speeds. After processing location, speed and acceleration data from the measurement systems, speed between the last five meters and stride length in the last stride of the trial were analyzed. Small biases and strong positive intraclass correlations (0.9-1.0) between the LPS and "the gold standard" were found. The significance of the study is that the LPS can be a valid method to determine speed and stride length. Variability of speed and stride length can be reduced when exploring data processing methods that can better extract speed and stride length measurements.

Effect of a Commercially Available Footwear Insole on Biomechanical Variables Associated With Common Running Injuries.

OBJECTIVE: To determine whether Dr. Scholl's Active Series (DSAS) footwear insoles alter biomechanical variables associated with running injuries. DESIGN: Randomized, controlled experiment. SETTING: Sport medicine and biomechanics gait analysis laboratory. PARTICIPANTS: Fifteen healthy adults. INTERVENTIONS: The control condition was the participant's own athletic footwear. The experimental condition was the participant's own athletic footwear plus a DSAS insole. Participants completed running gait analysis trials with each condition. MAIN OUTCOME MEASURES: Peak vertical loading rates (VLRs), peak ankle eversion velocities (AEVs), peak ankle eversion angles (AEAs), and knee abduction angular impulses (KAAIs) were calculated and compared between the control and DSAS conditions because these variables have been associated with plantar fasciitis (VLRs), tibial stress syndrome (AEVs, AEAs), and patellofemoral pain syndrome (KAAIs). RESULTS: Dr. Scholl's Active Series insoles reduced VLRs across participants by 16% (P < 0.001) but had no consistent influence on AEVs, AEAs, or KAAIs. Participant-specific responses showed that most runners either experienced AEA and KAAI reductions or no change with the DSAS insole, whereas AEVs commonly increased with the DSAS insole. CONCLUSIONS: Dr. Scholl's Active Series insoles demonstrate efficacy in reducing VLRs, which are associated with plantar fasciitis. Biomechanical changes to variables associated with tibial stress syndrome (AEVs, AEAs) and patellofemoral pain syndrome (KAAIs) were inconsistent.

Influence of the composition of artificial turf on rotational traction and athlete biomechanics.

Artificial turf advances have enabled surfaces to behave like natural grass, however, debate remains as to whether artificial turf is as safe as natural grass. To reduce injury risk, sport surfaces should have low rotational traction with artificial surfaces having a potential advantage as components can be manipulated to change surface properties and traction. The purpose of this study was to investigate the influence that different components of artificial turf have on rotational traction and athlete lower extremity joint loading. Twelve surfaces underwent mechanical testing to determine the influence of fibre density, fibre length, infill composition and compaction on rotational traction. Following mechanical testing, Control, Low and High Traction surfaces were selected for biomechanical analysis, where sixteen athletes performed maximum effort v-cuts while kinematic/kinetic data were recorded on each surface. Mechanically, fibre density, type of infill and compaction of the surface each independently influenced traction. The traction differences were substantial enough to alter the athlete kinematics and kinetics. Low traction surfaces reduced ankle and knee loading, while high traction surfaces increased ankle and knee loading . Reducing the rotational traction of sport surfaces is possible through alterations of individual components, which may reduce the joint loading at the knee and ankle joint.

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

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.

Effect of a Compressive Garment on Kinematics of Jump-Landing Tasks.

de Britto, MA, Lemos, AL, dos Santos, CS, Stefanyshyn, DJ, and Carpes, FP. Effect of a compressive garment on kinematics of jump-landing tasks. J Strength Cond Res 31(9): 2480-2488, 2017-During jump-landing tasks, knee kinematics such as excessive valgus have been linked to knee injury in females. We determine the influence of a compressive garment on knee valgus during landing. Physically active women (n = 27, mean age 23 years) performed 4 different jump-landing tasks with 2 apparel conditions (compressive garment and regular sports shorts). Kinematic data were collected to determine knee flexion and valgus angles and the maximum jump height. Results showed that the compressive garment decreased knee flexion and knee valgus range of motion, without significant changes in the maximum jump height. As a practical application, we suggest that compression could be a strategy to reduce dynamic valgus without influencing jump performance, which motivates further study of its potential for knee injury prevention.

The effect of translational and rotational traction on lower extremity joint loading.

Previous studies have linked footwear traction to lower extremity non-contact injury; however, these studies mainly focussed on rotational traction exclusively. While studies have shown that increases in traction lead to increases in joint loading, represented by joint moments, these studies failed to determine how the individual components of rotational and translational traction affect joint loading. Therefore, this study investigated how each component of traction independently affects lower extremity joint loading. Traction testing was performed using a robotic testing machine on three shoes that had independent alterations of translational and rotational traction. All testing was conducted on a sample piece of artificial turf. Kinematic and kinetic data were then collected on 10 athletes performing two cutting movements in each shoe condition. As rotational and translational traction were independently altered, decreased rotational traction led to significant decreases in transverse and frontal plane joint loading at the ankle and knee joints, while increases in translational traction led to increases in frontal plane joint loading at the ankle and knee joints. Increases in joint loading in the transverse and frontal planes are one of the possible mechanisms of lower extremity non-contact injury. Both translational and rotational traction can independently alter the joint loading.

Effects of strengthening and stretching exercise programmes on kinematics and kinetics of running in older adults: a randomised controlled trial.

The aim of this study was to investigate the effects of strengthening and stretching exercises on running kinematics and kinetics in older runners. One hundred and five runners (55-75 years) were randomly assigned to either a strengthening (n = 36), flexibility (n = 34) or control (n = 35) group. Running kinematics and kinetics were obtained using an eight-camera system and an instrumented treadmill before and after the eight-week exercise protocol. Measures of strength and flexibility were also obtained using a dynamometer and inclinometer/goniometer. A time effect was observed for the excursion angles of the ankle sagittal (P = 0.004, d = 0.17) and thorax/pelvis transverse (P < 0.001, d = 0.20) plane. Similarly, a time effect was observed for knee transverse plane impulse (P = 0.013, d = 0.26) and ground reaction force propulsion (P = 0.042, d = -0.15). A time effect for hip adduction (P = 0.006, d = 0.69), ankle dorsiflexion (P = 0.002, d = 0.47) and hip internal rotation (P = 0.048, d = 0.30) flexibility, and hip extensor (P = 0.001, d = -0.48) and ankle plantar flexor (P = 0.01, d = 0.39) strength were also observed. However, these changes were irrespective of exercise group. The results of the present study indicate that an eight-week stretching or strengthening protocol, compared to controls, was not effective in altering age-related running biomechanics despite changes in ankle and trunk kinematics, knee kinetics and ground reaction forces along with alterations in muscle strength and flexibility were observed over time.

Incremental Testing Design on Slide Board for Speed Skaters: Comparison Between Two Different Protocols.

Piucco, T, O'Connell, J, Stefanyshyn, D, and de Lucas, RD. Incremental testing design on slide board for speed skaters: comparison between two different protocols. J Strength Cond Res 30(11): 3116-3121, 2016-The aim of this study was to investigate the effect of stage duration (Long-stage-LS: 3-minute, Short-stage-SS: 1-minute) on maximal and submaximal aerobic physiological variables during a simulated skating test performed on a slide board. Ten well-trained male speed skaters performed 2 maximal incremental tests on slide board until voluntary exhaustion. The second ventilatory threshold (VT2) was determined by the ventilatory equivalent method. All participants reached the criteria for maximal oxygen uptake (V[Combining Dot Above]O2max) attainment in both protocols. Maximal cadence (CADmax), V[Combining Dot Above]O2 at VT2 and cadence at VT2 (CADVT2) were significantly higher during SS protocol, but maximal heart rate was significantly lower for the SS protocol. V[Combining Dot Above]O2max was significantly correlated with CADmax for the SS (r = 0.62) and LS protocols (r = 0.61). Strong correlations were found between CADmax and CADVT2 during the SS (r = 0.83) and LS protocols (r = 0.76). The results of the present study suggest that either SS or LS slide board incremental protocol can be used to evaluate skaters, since they elicited maximal physiological responses. Additionally, slide board incremental skating tests may be considered as a more specific and practical alternative than laboratory-based tests, especially when a large number of athletes need to be assessed.

Influence of Compression and Stiffness Apparel on Vertical Jump Performance.

Compression apparel alters both compression of the soft tissues and the hip joint stiffness of athletes. It is not known whether it is the compression elements, the stiffness elements, or some combination that increases performance. Therefore, the purpose of this study was to determine how systematically increasing upper leg compression and hip joint stiffness independently from one another affects vertical jumping performance. Ten male athletes performed countermovement vertical jumps in 8 concept apparel conditions and 1 control condition (loose fitting shorts). The 8 apparel conditions, 4 that specifically altered the amount of compression exerted on the thigh and 4 that altered the hip joint stiffness by means of elastic thermoplastic polyurethane bands, were tested on 2 separate testing sessions (one testing the compression apparel and the other testing the stiffness apparel). Maximum jump height was measured, while kinematic data of the hip, knee, and ankle joint were recorded with a high-speed camera (480 Hz). Both compression and stiffness apparel can have a positive influence on vertical jumping performance. The increase in jump height for the optimal compression was due to increased hip joint range of motion and a trend of increasing the jump time. Optimal stiffness also increased jump height and had the trend of decreasing the hip joint range of motion and hip joint angular velocity. The exact mechanisms by which apparel interventions alter performance is not clear, but it may be due to alterations to the force-length and force-velocity relationships of muscle.

Effects of changing speed on knee and ankle joint load during walking and running.

Joint moments can be used as an indicator of joint loading and have potential application for sports performance and injury prevention. The effects of changing walking and running speeds on joint moments for the different planes of motion still are debatable. Here, we compared knee and ankle moments during walking and running at different speeds. Data were collected from 11 recreational male runners to determine knee and ankle joint moments during different conditions. Conditions include walking at a comfortable speed (self-selected pacing), fast walking (fastest speed possible), slow running (speed corresponding to 30% slower than running) and running (at 4 m · s(-1) ± 10%). A different joint moment pattern was observed between walking and running. We observed a general increase in joint load for sagittal and frontal planes as speed increased, while the effects of speed were not clear in the transverse plane moments. Although differences tend to be more pronounced when gait changed from walking to running, the peak moments, in general, increased when speed increased from comfortable walking to fast walking and from slow running to running mainly in the sagittal and frontal planes. Knee flexion moment was higher in walking than in running due to larger knee extension. Results suggest caution when recommending walking over running in an attempt to reduce knee joint loading. The different effects of speed increments during walking and running should be considered with regard to the prevention of injuries and for rehabilitation purposes.

Effects of cold water immersion on lower extremity joint biomechanics during running.

The purpose of this study was to identify the influence of cryotherapy on lower extremity running biomechanics. Twenty-six healthy male volunteers were randomised into two intervention groups: cold water (cold water at ~11°C) or tepid water (tepid water at ~26°C). They were required to run at 4.0 ± 0.2 m · s(-1) before and after they underwent water immersion for 20 min. Differences between pre- and post-intervention were used to compare the influence of water intervention during running. Peak joint angles, peak joint moments, peak ground reaction forces (GRF) and contact time (CT) were calculated using three-dimensional gait analysis. Independent t-tests were applied with a significant alpha level set at 0.05. Decreased peak propulsive and vertical GRF, decreased plantarflexion moments, increased hip flexion angle and longer CT were observed following cold water immersion. Although cold water immersion (cryotherapy) affected the running movement, none of the alterations have been related to running biomechanical patterns associated with injuries. Therefore, our results indicated that cold water immersion appears safe prior to running activities.

The effects of isolated ankle strengthening and functional balance training on strength, running mechanics, postural control and injury prevention in novice runners: design of a randomized controlled trial.

BACKGROUND: Risk factors have been proposed for running injuries including (a) reduced muscular strength, (b) excessive joint movements and (c) excessive joint moments in the frontal and transverse planes. To date, many running injury prevention programs have focused on a "top down" approach to strengthen the hip musculature in the attempt to reduce movements and moments at the hip, knee, and/or ankle joints. However, running mechanics did not change when hip muscle strength increased. It could be speculated that emphasis should be placed on increasing the strength of the ankle joint for a "ground up" approach. Strengthening of the large and small muscles crossing the ankle joint is assumed to change the force distribution for these muscles and to increase the use of smaller muscles. This would be associated with a reduction of joint and insertion forces, which could have a beneficial effect on injury prevention. However, training of the ankle joint as an injury prevention strategy has not been studied. Ankle strengthening techniques include isolated strengthening or movement-related strengthening such as functional balance training. There is little knowledge about the efficacy of such training programs on strength alteration, gait or injury reduction. METHODS/DESIGN: Novice runners will be randomly assigned to one of three groups: an isolated ankle strengthening group (strength, n = 40), a functional balance training group (balance, n = 40) or an activity-matched control group (control, n = 40). Isokinetic strength will be measured using a Biodex System 3 dynamometer. Running kinematics and kinetics will be assessed using 3D motion analysis and a force platform. Postural control will be assessed by quantifying the magnitude and temporal structure of the center of pressure trace during single leg stance on a force platform. The change pre- and post-training in isokinetic strength, running mechanics, and postural control variables will be compared following the interventions. Injuries rates will be compared between groups over 6 months. DISCUSSION: Avoiding injury will allow individuals to enjoy the benefits of participating in aerobic activities and reduce the healthcare costs associated with running injuries. TRIAL REGISTRATION: Current Controlled Trial NCT01900262.

Reduced knee joint loading with lateral and medial wedge insoles for management of knee osteoarthritis: a protocol for a randomized controlled trial.

BACKGROUND: Knee osteoarthritis (OA) progression has been linked to increased peak external knee adduction moments (KAMs). Although some trials have attempted to reduce pain and improve function in OA by reducing KAMs with a wedged footwear insole intervention, KAM reduction has not been specifically controlled for in trial designs, potentially explaining the mixed results seen in the literature. Therefore, the primary purpose of this trial is to identify the effects of reduced KAMs on knee OA pain and function. METHODS/DESIGN: Forty-six patients with radiographically confirmed diagnosis medial knee OA will be recruited for this 3 month randomized controlled trial. Recruitment will be from Alberta and surrounding areas. Eligibility criteria include being between the ages of 40 and 85 years, have knee OA primarily localized to the medial tibiofemoral compartment, based on the American College of Rheumatology diagnostic criteria and be classified as having a Kellgren-Lawrence grade of 1 to 3. Patients will visit the laboratory at baseline for testing that includes dual x-ray absorptiometry, biomechanical testing, and surveys (KOOS, PASE activity scale, UCLA activity scale, comfort visual analog scale). At baseline, patients will be randomized to either a wedged insole group to reduce KAMs, or a waitlist control group where no intervention is provided. The survey tests will be repeated at 3 months, and response to wedged insoles over 3 months will be evaluated. DISCUSSION: This study represents the first step in systematically evaluating the effects of reduced KAMs on knee OA management by using a patient-specific wedged insole prescription procedure rather than providing the same insole to all patients. The results of this trial will provide indications as to whether reduced KAMs are an effective strategy for knee OA management, and whether a personalized approach to footwear insole prescription is warranted. TRIAL REGISTRATION: NCT02067208.

Development and validation of a computerized visual analog scale for the measurement of pain in patients with patellofemoral pain syndrome.

OBJECTIVE: To develop a computerized visual analog scale (cVAS) system and determine if it could be used in place of the traditional 100-mm paper-based visual analog scale (pVAS) method for the measurement of pain in patients with patellofemoral pain syndrome (PFPS). DESIGN: Descriptive laboratory study. SETTING: Biomechanics laboratory. PARTICIPANTS: Thirty-six runners diagnosed with PFPS. INTERVENTIONS: A cVAS system was custom-coded for this study. Participants completed both the cVAS survey and a pVAS survey that measured usual knee pain during running, walking, prolonged sitting, stair ascent, stair descent, and squatting movements. Thus, 216 paired measurements were made in total. MAIN OUTCOME MEASURES: Pearson correlation coefficients and slopes of the line of best fit were calculated to assess the relationship between cVAS and pVAS scores, and Bland-Altman plots were constructed to determine cVAS agreement to pVAS scores. RESULTS: All cVAS measures were highly correlated to pVAS scores (all r values were >0.9), and slopes were always near 1.0. Bland-Altman plots demonstrated that there was good agreement between the 2 methods. CONCLUSIONS: The cVAS system that was developed is a valid method for measurement of pain in patients with PFPS. Further use of the cVAS for studies involving PFPS is supported.

The effects of wedged footwear on lower limb frontal plane biomechanics during running.

OBJECTIVE: Patellofemoral pain syndrome (PFPS), the most common running injury, has been associated with increased internal knee abduction angular impulses (KAAI). Wedged footwear can reduce these impulses during walking, but their effects during running are not well understood. The purpose of this study was to identify the effects of wedged footwear on KAAIs and describe the mechanism by which wedged footwear alters KAAIs during running. DESIGN: Controlled laboratory study. SETTING: Motion analysis laboratory. PARTICIPANTS: Nine healthy male subjects. INTERVENTIONS: Participants ran at a speed of 4 m/s with 7 different footwear conditions (3-, 6-, and 9-mm lateral wedges; 3-, 6-, and 9-mm medial wedges; neutral). MAIN OUTCOME MEASURES: Knee abduction angular impulses and 8 predictor variables were measured and compared by 1-way repeated measures analysis of variance (α = 0.05) with Bonferroni-adjusted 2-tailed paired t tests for post hoc analysis (α = 0.002). Correlation (α = 0.05) was used to determine the relationship between the mediolateral center of pressure to ankle joint center (COP-AJC) lever arm length and KAAIs. RESULTS: Laterally wedged conditions produced significantly lower KAAIs (P = 0.001) than medial wedge conditions. Peak knee abduction moments decreased (P = 0.001), whereas ankle inversion moments (P = 0.041) and the COP-AJC lever arms increased (P < 0.001) as wedges progressed from medial to lateral. KAAIs were negatively correlated with COP-AJC lever arm length (r = -0.50, P < 0.001). CONCLUSIONS: KAAIs are reduced with laterally wedged footwear because of lateral shifts in the center of pressure beneath the foot, which then increases ankle inversion moments and decreases peak knee abduction moments. Laterally wedged footwear may therefore offer greater relief to runners with PFPS than medially wedged footwear by reducing KAAIs.

Average torsion axis location of athletic movements: subject specific or movement specific?

Foot torsion angles have previously been studied for different athletic movements. Sport shoes often contain a torsion element even though the location of the rotation axis of the foot is unknown. Therefore, the purpose of this study was to quantify the torsion axis location and determine if the location is influenced by the movement or the subject. The torsion axis location was calculated using a modified finite helical axis approach, which allowed the calculation of the rotation axis between the forefoot and the rearfoot without the influence of forefoot flexion. The torsion axis location during the lateral jab was 9.72 mm below and 26.96 mm lateral to a marker located at the posterior, central heel, whereas the shuffle cut resulted in an axis location of 9.59 mm below and 26.19 mm lateral to the reference marker. There was no significant difference for the average axis location between movements. There was, however, a significant difference for the location between subjects, indicating a subject specificity of the torsion axis. The results of the current study are the first to quantify the torsion axis location of the human foot during athletic movements.

Influence of forefoot bending stiffness on American football performance and metatarsophalangeal joint bending angle.

Changes in forefoot bending stiffness have been shown to affect metatarsophalangeal peak bending angles as well as athletic performance. Increasing bending stiffness tends to reduce peak bending angles, which could potentially reduce hyperextension injuries such as turf toe. Limited information is available, however, on the efficacy of increasing forefoot bending stiffness on large-sized athletes such as those that participate in American Football, with prior studies being conducted on smaller athlete populations. Therefore, the purpose of this study was to determine the influence of increased forefoot bending stiffness on metatarsophalangeal joint extension and athletic performance of grid-iron football players. Ten varsity grid-iron football players performed four National Football League combine movements in a motion capture laboratory in three footwear conditions of varying bending stiffness: Soft (12.7 N/mm), Control (23.8 N/mm), Stiff (42.2 N/mm). None of the footwear conditions significantly altered the maximum metatarsophalangeal bending. Therefore, to reduce metatarsophalangeal hyperextension injuries in American football players a greater amount of forefoot bending stiffness may be required. Performance differences were present only during the five-metre sprint acceleration, with athletes having an improved performance in the Control and Stiff conditions. This improved performance was due to an increased horizontal impulse and improvements in power generation at the ankle joint.