bluuebunny/crossref_metadata_2025 huggingface dataset:
Altered Alignment of the Shoulder Girdle and Cervical Spine in Patients With Insidious Onset Neck Pain and Whiplash-Associated Disorder
Authors: Helgadottir Harpa , Kristjansson Eythor , Mottram Sarah , Karduna Andrew , Jonsson Halldor
Published: August 2016

Clinical theory suggests that altered alignment of the shoulder girdle has the potential to create or sustain symptomatic mechanical dysfunction in the cervical and thoracic spine. The alignment of the shoulder girdle is described by two clavicle rotations, i.e, elevation and retraction, and by three scapular rotations, i.e., upward rotation, internal rotation, and anterior tilt. Elevation and retraction have until now been assessed only in patients with neck pain. The aim of the study was to determine whether there is a pattern of altered alignment of the shoulder girdle and the cervical and thoracic spine in patients with neck pain. A three-dimensional device measured clavicle and scapular orientation, and cervical and thoracic alignment in patients with insidious onset neck pain (IONP) and whiplash-associated disorder (WAD). An asymptomatic control group was selected for baseline measurements. The symptomatic groups revealed a significantly reduced clavicle retraction and scapular upward rotation as well as decreased cranial angle. A difference was found between the symptomatic groups on the left side, whereas the WAD group revealed an increased scapular anterior tilt and the IONP group a decreased clavicle elevation. These changes may be an important mechanism for maintenance and recurrence or exacerbation of symptoms in patients with neck pain.
Ski Jumping Takeoff in a Wind Tunnel With Skis
Authors: Virmavirta Mikko , Kivekäs Juha , Komi Paavo
Published: August 2016

The effect of skis on the force–time characteristics of the simulated ski jumping takeoff was examined in a wind tunnel. Takeoff forces were recorded with a force plate installed under the tunnel floor. Signals from the front and rear parts of the force plate were collected separately to examine the anteroposterior balance of the jumpers during the takeoff. Two ski jumpers performed simulated takeoffs, first without skis in nonwind conditions and in various wind conditions. Thereafter, the same experiments were repeated with skis. The jumpers were able to perform very natural takeoff actions (similar to the actual takeoff) with skis in wind tunnel. According to the subjective feeling of the jumpers, the simulated ski jumping takeoff with skis was even easier to perform than the earlier trials without skis. Skis did not much influence the force levels produced during the takeoff but they still changed the force distribution under the feet. Contribution of the forces produced under the rear part of the feet was emphasized probably because the strong dorsiflexion is needed for lifting the skis to the proper flight position. The results presented in this experiment emphasize that research on ski jumping takeoff can be advanced by using wind tunnels.
Decreased Frontal Plane Hip Joint Moments in Runners With Excessive Varus Excursion at the Knee
Authors: Williams Dorsey Shelton , Isom Wesley
Published: August 2016

Knee varus position and motion have been correlated with increased medial knee loading during gait. The purpose of this study is to determine whether runners with excessive varus excursion (EVE) at the knee demonstrate frontal plane knee and hip kinetics that are different from those of runners with normal varus excursion (NVE). Twelve runners with EVE were compared with 12 NVE subjects using three-dimensional kinematics and kinetics. Frontal plane angles and moments were compared at the knee and hip. Runners with EVE had significantly greater abductor moment of the knee (p = .004) and lower peak abductor moment of the hip (p = .047). Runners with EVE demonstrate knee and hip mechanics thought to be associated with increased medial tibiofemoral loading. Further understanding of how changing hip abductor moments may affect changes in knee abductor moments during running may potentially lead to interventions that augment long-term risk of injury.
Effects of Vertical Loading on Arch Characteristics and Intersegmental Foot Motions
Authors: Powell Douglas W. , Long Benjamin , Milner Clare E. , Zhang Songning
Published: August 2016

The medial longitudinal arch plays a major role in determining lower extremity kinematics. Thus, it is necessary to understand the dynamics of the arch structure in response to load. The purpose of this study was to examine arch function in high- and low-arched feet during a vertical loading condition. Ten high- and ten low-arched females performed five trials in a sit-to-stand exercise. Ground reaction force (1200 Hz) and three-dimensional kinematics (240 Hz) were collected simultaneously. The high-and low-arched athletes had no differences in vertical deformation of the arch. High-arched participants were less everted than the low-arched athletes; furthermore, the high-arched athletes had smaller mid-forefoot eversion excursions. Differences between the high-arched and low-arched athletes occur through and motion at the mid-forefoot joint.
Pharmacological Treatment of Intermittent Claudication Does Not Have a Significant Effect on Gait Impairments During Claudication Pain
Authors: Yentes Jennifer M. , Huisinga Jessie M. , Myers Sara A. , Pipinos Iraklis I. , Johanning Jason M. , Stergiou Nicholas
Published: August 2016

Peripheral arterial disease (PAD) is a manifestation of atherosclerosis resulting in intermittent claudication (IC) or leg pain during physical activity. Two drugs (cilostazol and pentoxifylline) are approved for treatment of IC. Our previous work has reported no significant differences in gait biomechanics before and after drug interventions when PAD patients walked without pain. However, it is possible that the drugs are more efficacious during gait with pain. Our aim was to use advanced biomechanical analysis to evaluate the effectiveness of these drugs while walking with pain. Initial and absolute claudication distances, joint kinematics, torques, powers, and gait velocity during the presence of pain were measured from 24 patients before and after 12 weeks of treatment with either cilostazol or pentoxifylline. We found no significant improvements after 12 weeks of treatment with either cilostazol or pentoxifylline on the gait biomechanics of PAD patients during pain. Our findings indicate that the medications cilostazol and pentoxifylline have reduced relevance in the care of gait dysfunction even during pain in patients with PAD.
Kinematic and Kinetic Synergies of the Lower Extremities During the Pull in Olympic Weightlifting
Authors: Kipp Kristof , Redden Josh , Sabick Michelle , Harris Chad
Published: August 2016

The purpose of this study was to identify multijoint lower extremity kinematic and kinetic synergies in weight-lifting and compare these synergies between joints and across different external loads. Subjects completed sets of the clean exercise at loads equal to 65, 75, and 85% of their estimated 1-RM. Functional data analysis was used to extract principal component functions (PCF’s) for hip, knee, and ankle joint angles and moments of force during the pull phase of the clean at all loads. The PCF scores were then compared between joints and across loads to determine how much of each PCF was present at each joint and how it differed across loads. The analyses extracted two kinematic and four kinetic PCF’s. The statistical comparisons indicated that all kinematic and two of the four kinetic PCF’s did not differ across load, but scaled according to joint function. The PCF’s captured a set of joint- and load-specific synergies that quantified biomechanical function of the lower extremity during Olympic weightlifting and revealed important technical characteristics that should be considered in sports training and future research.
Dynamics of Seated Computer Work Before and After Prolonged Constrained Sitting
Authors: Madeleine Pascal
Published: August 2016

This laboratory study investigated seated computer work before and after prolonged constrained sitting. Discomfort ratings and kinetic and kinematics data were recorded in nine healthy males performing computer work for 5 min before and after 96 min of sitting. The displacement of the center of pressure (CoP) in anterior-posterior and medial-lateral directions and lumbar curvature (LC) were calculated. The root mean square, standard deviation, and sample entropy values were computed from the CoPs and LC signals to assess the magnitude, amount of variability, and regularity of sitting dynamics, respectively. The discomfort increased for the buttocks (p = .02).The standard deviation and sample entropy values of the CoPs and LC signals, respectively, increased (p < .04) and decreased (p < .004) whereas the root mean square remained unchanged (p > .15) after prolonged constrained sitting compared with before. This present study showed that during seated computer work, prolonged constrained sitting affected the amount of variability and the regularity of sitting postural control, whereas the magnitude was not affected. The importance of the dynamics of sitting control may challenge the idea of a static and ideal seated posture at work.
Relationships Between Glide Efficiency and Swimmers’ Size and Shape Characteristics
Authors: Naemi Roozbeh , Psycharakis Stelios G. , McCabe Carla , Connaboy Chris , Sanders Ross H.
Published: August 2016

Glide efficiency, the ability of a body to minimize deceleration over the glide, can change with variations in the body’s size and shape. The purpose of this study was to investigate the relationships between glide efficiency and the size and shape characteristics of swimmers. Eight male and eight female swimmers performed a series of horizontal glides at a depth of 70 cm below the surface. Glide efficiency parameters were calculated for velocities ranging from 1.4 to 1.6 m/s for female swimmers (and at the Reynolds number of 3.5 million) and from 1.6 to 1.8 m/s for male swimmers (and at the Reynolds number of 4.5 million). Several morphological indices were calculated to account for the shape characteristics, with the use of a photogrammetric method. Relationships between the variables of interest were explored with correlations, while repeated-measures ANOVA was used to assess within-group differences between different velocities for each gender group. Glide efficiency of swimmers increased when velocity decreased. Some morphological indices and postural angles showed a significant correlation with glide efficiency. The glide coefficient was significantly correlated to the chest to waist taper index for both gender groups. For the male group, the glide coefficient correlated significantly to the fineness ratio of upper body, the chest to hip cross-section. For the female group the glide coefficient had a significant correlation with the waist to hip taper index. The findings suggested that gliding efficiency was more dependent on shape characteristics and appropriate postural angles rather than being dependent on size characteristics.
Altering Footwear Type Influences Gait During Level Walking and Downhill Transitions
Authors: Stern Keith A. , Gottschall Jinger S.
Published: August 2016

The purpose of our study was to determine if altering the insoles within footwear or walking barefoot, as an attempt to increase or decrease cutaneous stimuli, would improve dynamic balance during a hill-walking task. We hypothesize that compared with foam insoles or iced bare feet, textured insoles or bare feet will result in greater speeds, longer step lengths, narrower step width, shorter stance time, and less tibialis anterior (TA), soleus (SOL), and lateral gastrocnemius (LG) activity during key gait cycle phases. Ten, healthy college students, 5 men and 5 women, completed the protocol that consisted of level walking and downhill transition walking in five different footwear insole or barefoot conditions. During level walking, conditions with the hypothesized greater cutaneous stimuli resulted in greater step length, which relates to a more stable gait. In detail, the texture insole condition average step length was 3% longer than the regular insole condition, which was 5% longer than the ice condition (p < .01). The same signals of increased stability were evident during the more challenging downhill transition stride. Step length during the barefoot condition was 8% longer than the ice condition (p < .05) and step width during the regular footwear condition was 5% narrower than the foam condition (p = .05). To add, during the preswing phase of level walking, TA activity of the textured insole condition was 30% less than the foam insole. Although our data show that footwear conditions alter gait patterns and lower leg muscle activity during walking, there is not enough evidence to support the hypothesis that textured insoles will improve dynamic balance as compared with other footwear types.
The Effects of Orthotic Heel Lifts on Achilles Tendon Force and Strain During Running
Authors: Farris Dominic James , Buckeridge Erica , Trewartha Grant , McGuigan Miranda Polly
Published: August 2016

This study assessed the effects of orthotic heel lifts on Achilles tendon (AT) force and strain during running. Ten females ran barefoot over a force plate in three conditions: no heel lifts (NHL), with 12 mm heel lifts (12HL) and with 18 mm heel lifts (18HL). Kinematics for the right lower limb were collected (200 Hz). AT force was calculated from inverse dynamics. AT strain was determined from kinematics and ultrasound images of medial gastrocnemius (50 Hz). Peak AT strain was less for 18HL (5.5 ± 4.4%) than for NHL (7.4 ± 4.2%) (p = .029, effect size [ES] = 0.44) but not for 12HL (5.8 ± 4.8%) versus NHL (ES = 0.35). Peak AT force was significantly (p = .024, ES = 0.42) less for 18HL (2382 ± 717 N) than for NHL (2710 ± 830 N) but not for 12HL (2538 ± 823 N, ES = 0.21). The 18HL reduced ankle dorsiflexion but not flexion-extension ankle moments and increased the AT moment arm compared with NHL. Thus, 18HL reduced force and strain on the AT during running via a reduction in dorsiflexion, which lengthened the AT moment arm. Therefore, heel lifts could be used to reduce AT loading and strain during the rehabilitation of AT injuries.
Effects of Fatigue on Kinematical Parameters During Submaximal and Maximal 100-m Butterfly Bouts
Authors: de Jesus Kelly , de Jesus Karla , Figueiredo Pedro A. , Gonçalves Pedro , Vilas-Boas João Paulo , Fernandes Ricardo J.
Published: August 2016

We aimed to analyze the effects of fatigue on kinematical parameters during submaximal and maximal butterfly. Seven female swimmers performed two randomized 100-m butterfly bouts, at submaximal velocity and at maximal velocity in 25-m pool. During the 1st and 4th laps of each 100 m, kinematic data were recorded by two video cameras (above and below water) on the sagittal plane. Velocity, stroke length, stroke frequency, intracyclic horizontal velocity variation, horizontal and vertical displacements of the hand and foot and stroke phases’ duration were computed for each stroke cycle. Velocity, stroke length, stroke frequency were lower for 4th than 1st lap, at both intensities. Dropped elbow and foot vertical amplitude of 1st and 2nd downbeats were higher for 4th than 1st lap, at both intensities. At submaximal and maximal intensity, swimmers spent more time during push and recovery phases. At submaximal intensity, swimmers experienced fewer difficulties to cope with fatigue between 1st and 4th lap, which allowed the maintenance of intracyclic velocity variation. However, at maximal intensity, swimmers were probably more fatigued and, as a consequence, less mechanically efficient, showing an increase in intracyclic velocity variation.
A Biomechanical Assessment of the Sliding Motion of Curling Delivery in Elite and Subelite Curlers
Authors: Yoo Kyoung-Seok , Kim Hyun-Kyung , Park Jin-Hoon
Published: August 2016

The present study examined the technical characteristics of sliding performance from push-off until stone release in curling delivery. Five elite performance level curlers (> 7 years experience) and five subelite level curlers (< 3 years experience) were analyzed during the action of delivery of a curling stone. The joint angles, angular velocities, and moments of the body center of mass (COM) were determined based on three-dimensional kinematic data. The plantar pressure data were measured using a validated in-shoe system. The results indicated that the gliding time and horizontal velocity of the mass center of the body during the sliding phase were not significantly different between the elite and subelite groups. However, there were significant differences in the gliding distance and the rate of changes in velocity profiles of body COM between the two groups. The moment of the body COM from its relative position to the ankle of the support limb in the anterior/posterior direction was positive in elite curlers and negative in subelite curlers. In addition, larger ankle dorsiflexion and greater contact area of the sliding foot were observed in elite curlers. These data suggest a superior ability of elite curlers to maintain a regulated movement speed and balance control during the performance of a curling stone delivery.
Muscle Preactivation Control: Simulation of Ankle Joint Adjustments at Touchdown During Running on Uneven Ground
Authors: Müller Roy , Siebert Tobias , Blickhan Reinhard
Published: August 2016

In locomotion, humans have to deal with irregularities in the ground. When they encounter uneven terrain with changes in vertical height, they adjust the geometry of their legs. Recent investigations have shown that the preactivation of the gastrocnemius muscle (GM) correlates with the ankle angle at touchdown, but it is as of yet unclear why these adjustments were achieved by the GM and not by the preactivation of the tibialis anterior (TA). To examine the differences between TA regulation and GM regulation regarding (1) ankle angle adjustment and (2) joint stiffness, we used a three-segment musculoskeletal model with two antagonistic muscles (GM, TA). During the GM regulation, the ankle angle was adjusted from 121° to 109° (dorsiflexion) by a 41% decrease in the GM activation. During the TA regulation, the activation of TA must be increased by about 52%. In addition, we found that the ankle stiffness was most sensitive to changes in activation of the GM and decreased by about 20% while adjusting the angle. In contrast, the ankle stiffness remains similar when using TA regulation. Thus, the GM regulation is more adequate for adjustment in the ankle joint, enabling sufficient regulation of angle and stiffness.
Estimates of Gastrocnemius Muscle Length During Simulated Pathological Gait
Authors: Rao Smita , Dietz Fred , Yack H. John
Published: August 2016

The purpose of this study was to compare estimates of gastrocnemius muscle length (GML) obtained using a segmented versus straight-line model in children. Kinematic data were acquired on eleven typically developing children as they walked under the following conditions: normal gait, crouch gait, equinus gait, and crouch with equinus gait. Maximum and minimum GML, and GML change were calculated using two models: straight-line and segmented. A two-way RMANOVA was used to compare GML characteristics. Results indicated that maximum GML and GML change during simulated pathological gait patterns were influenced by model used to calculate gastrocnemius muscle length (interaction: P = .004 and P = .026). Maximum GML was lower in the simulated gait patterns compared with normal gait (P < .001). Maximum GML was higher with the segmented model compared with the straight-line model (P = .030). Using either model, GML change in equinus gait and crouch with equinus gait was lower compared with normal gait (P < .001). Overall, minimum GML estimated with the segmented model was higher compared with the straight-line model (P < .01). The key findings of our study indicate that GML is significantly affected by both gait pattern and method of estimation. The GML estimates tended to be lower with the straight-line model versus the segmented model.
Alterations in Gait Initiation Are Present in Those With Posttraumatic Ankle Osteoarthritis: A Pilot Study
Authors: Wikstrom Erik A. , Anderson Robert B.
Published: August 2016

The purpose of this investigation was to determine if stereotypical patterns of gait initiation are altered in those with posttraumatic ankle osteoarthritis. Ten subjects, five with unilateral ankle osteoarthritis and five uninjured controls, participated. Subjects completed the SF-36 and Ankle Osteoarthritis Scale to quantify self-reported disability as well as 10 dual-limb static stance trials and 10 gait initiation trials with each leg. Center of pressure outcomes were calculated for static balance trials while the peak center of pressure excursions were calculated for each phase of gait initiation. The results indicate greater self-reported disability (P < .05) and worse static postural control (P < .05) in the ankle osteoarthritis group. Nonstereotypical patterns were also observed during the first and third phases of gait initiation in those with ankle osteoarthritis. The results of this pilot study suggest that supraspinal motor control mechanisms may have changed in those with posttraumatic ankle osteoarthritis.
The Effect of Fastball Backspin Rate on Baseball Hitting Accuracy
Authors: Higuchi Takatoshi , Morohoshi Jun , Nagami Tomoyuki , Nakata Hiroki , Kanosue Kazuyuki
Published: August 2016

The effectiveness of fastballs of equivalent speed can differ; for example, one element of this difference could be due to the effect of rate and orientation of ball spin on launched ball trajectory. In the present experiment, baseball batters’ accuracy in hitting fastballs with different backspin rates at a constant ball velocity of 36 m/s was examined. Thirteen skilled baseball players (professionals, semiprofessionals, and college varsity players) participated in the study. The movements of bat and ball were recorded using two synchronized high-speed video cameras. The Pearson product-moment correlation coefficient (r) was calculated and used to analyze the relationship between ball backspin rate and the vertical distance between ball center and sweet spot at the moment of ball-bat impact. Ball backspin rate was positively correlated with increases in the distance from the optimal contact point of the swung bat (sweet spot) to the actual point of contact (r = .38, P < .001). Batters were most effective at the usual backspin rate for the ball velocity used. The decrease in accuracy of the batter’s swing that was observed when the fastball’s backspin deviated from the usual rate likely occurred because experienced batters predict ball trajectory from perceived ball speed.
Gait Mechanics Are Different Between Healthy Controls and Patients With Multiple Sclerosis
Authors: Huisinga Jessie M. , Schmid Kendra K. , Filipi Mary L. , Stergiou Nicholas
Published: August 2016

Multiple sclerosis (MS) causes severe gait problems in relatively young individuals, yet there have been limited studies to quantitatively identify the specific gait parameters that are affected. The purpose of this study was to define any differences in biomechanical gait parameters between patients with MS and healthy controls. A total of 31 MS patients and 31 healthy controls were evaluated: joint torques and joint powers were calculated at the ankle, knee, and hip during the stance phase of gait. The self-selected walking velocity was used as a covariate in the analysis to ensure that group differences were not due to differences in walking velocity between the MS and healthy control groups. Reduced angular range, less joint torque, and reduced joint power were seen in patients with MS. We also found significant correlations between biomechanical gait parameters and EDSS score, which provides a clinical rating of disease severity. Our findings provide a quantitative assessment of the gait mechanics employed in patients with MS. The altered lower extremity mechanics observed in patients with MS reflect both a neurological and strength deficit compared with healthy controls during walking.
Humeral Head Translation After a Suprascapular Nerve Block
Authors: San Juan Jun G. , Kosek Peter , Karduna Andrew R.
Published: August 2016

Subacromial impingement syndrome is the most common shoulder disorder. Abnormal superior translation of the humeral head is believed to be a major cause of this pathology. The first purpose of the study was to examine the effects of suprascapular nerve block on superior translation of the humeral head and scapular upward rotation during dynamic shoulder elevation. The secondary purpose was to assess muscle activation patterns during these motions. Twenty healthy subjects participated in the study. Using fluoroscopy and electromyography, humeral head translation and muscle activation were measured before and after a suprascapular nerve block. The humeral head was superiorly located at 60 degrees of humeral elevation, and the scapula was more upwardly rotated from 30 to 90 degrees of humeral elevation after the block. The differences were observed during midrange of motion. In addition, the deltoid muscle group demonstrated increased muscle activation after the nerve block. The study’s results showed a compensatory increase in humeral head translation, scapular upward rotation, and deltoid muscle activation due to the nerve block. These outcomes suggest that increasing muscular strength and endurance of the supraspinatus and infraspinatus muscles could prevent any increased superior humeral head translation. This may be beneficial in reducing shoulder impingement or rotator cuff tears over time.
Kinematic and Kinetic Evaluation of the Stance Phase of Stair Ambulation in Persons with Stroke and Healthy Adults: A Pilot Study
Authors: Novak Alison C. , Brouwer Brenda
Published: August 2016

This study describes and contrasts the kinematics and kinetics of stair ambulation in people with chronic stroke and healthy control subjects. Three-dimensional motion data were collected from 10 persons with stroke (7 males) and 10 sex and age-matched older adults as they ascended and descended an instrumented staircase at self-selected speed with and without a handrail. Ankle, knee and hip joint angle and moment profiles were generated during stance and range of motion and peak moments were contrasted between groups, sides (stroke only) and condition. Cadence was lower in stroke than controls, although the kinematic profiles appeared similar during ascent and decent. Notable differences in joint kinetics were evident as the peak extensor moments were typically lower on the affected side in stroke compared with controls and the less affected side. These differences accounted for the lower magnitude net extensor support moment. The lower affected side hip abductor moments likely limited lateral stability. Handrail use tended to reduce the peak moments on the affected side only leading to more side-to-side differences than occurred without the handrail. The findings reveal differences in task performance between stroke and healthy groups that help inform rehabilitation practice.
Influence of Surface on Impact Shock Experienced During a Fencing Lunge
Authors: Greenhalgh Andrew , Bottoms Lindsay , Sinclair Jonathan
Published: August 2016

The purpose of this study was to investigate the effect of sports surface on the magnitude of impact shock experienced during a lunge movement. Thirteen experienced, competitive fencers (age 32.4 ± 4.6 years; height 178.4 ± 7.2 cm; mass 74.4 ± 9.1 kg) performed 10 lunges on four different surfaces: concrete with an overlaid vinyl layer (COVL), wooden sprung court surface (WSCS), metallic carpet fencing piste overlaid on the WSCS, and aluminum fencing piste overlaid on the WSCS. An accelerometer measured accelerations along the longitudinal axis of the tibia at 1000 Hz. The results identified a significantly (P < .05) larger impact shock magnitude was experienced during a lunge on the COVL (14.88 ± 8.45 g) compared with the WSCS (11.61 ± 7.30 g), WSCS with metallic carpet piste (11.14 ± 6.38 g) and WSCS with aluminum piste (11.95 ± 7.21 g). Furthermore, the two types of piste used had no significant effect the impact shock magnitude measured when overlaid on the WSCS compared with the WSCS on its own. The results of this investigation suggest that occurrences of injuries related to increased levels of impact shock may be reduced through the utilization of a WSCS as opposed to a COVL surface during fencing participation.
The Effects of Ankle Restriction on the Multijoint Coordination of Vertical Jumping
Authors: Arakawa Hiroshi , Nagano Akinori , Hay Dean C. , Kanehisa Hiroaki
Published: August 2016

The current study aimed to investigate the effect of ankle restriction on the coordination of vertical jumping and discuss the influence of energy transfer through m. gastrocnemius on the multijoint movement. Eight participants performed two types of vertical jumps: a normal squat jump, and a squat jump with restricted ankle joint movement. Mechanical outputs were calculated using an inverse dynamics analysis. Custom-made shoes were used to restrict plantar flexion, resulting in significantly (P < .001) reduced maximum power and work at the ankle joint to below 2% and 3%, while maintaining natural range of motion at the hip and knee. Based on the comparison between the two types of jumps, we determined that the ankle restriction increased (P < .001) the power (827 ± 346 W vs. 1276 ± 326 W) and work (92 ± 34 J vs. 144 ± 36 J) at the knee joint. A large part of the enhanced output at the knee is assumed to be due to ankle restriction, which results in the nullification of energy transport via m. gastrocnemius; that is, reduced contribution of the energy transfer with ankle restriction appeared as augmentation at the knee joint.
Effects of Age-Related Differences in Femoral Loading and Bone Mineral Density on Strains in the Proximal Femur During Controlled Walking
Authors: Anderson Dennis E. , Madigan Michael L.
Published: August 2016

Maintenance of healthy bone mineral density (BMD) is important for preventing fractures in older adults. Strains experienced by bone in vivo stimulate remodeling processes, which can increase or decrease BMD. However, there has been little study of age differences in bone strains. This study examined the relative contributions of age-related differences in femoral loading and BMD to age-related differences in femoral strains during walking using gait analysis, static optimization, and finite element modeling. Strains in older adult models were similar or larger than in young adult models. Reduced BMD increased strains in a fairly uniform manner, whereas older adult loading increased strains in early stance but decreased strains in late stance. Peak ground reaction forces, hip joint contact forces, and hip flexor forces were lower in older adults in late stance phase, and this helped older adults maintain strains similar to those of young adults despite lower BMD. Because walking likely represents a “baseline” level of stimulus for bone remodeling processes, increased strains during walking in older adults might indicate the extent of age-related impairment in bone remodeling processes. Such a measure might be clinically useful if it could be accurately determined with age-appropriate patient-specific loading, geometry, and BMD.
Electromyography Normalization Methods for High-Velocity Muscle Actions: Review and Recommendations
Authors: Ball Nick , Scurr Joanna
Published: August 2016

Electromyograms used to assess neuromuscular demand during high-velocity tasks require normalization to aid interpretation. This paper posits that, to date, methodological approaches to normalization have been ineffective and have limited the application of electromyography (EMG). There is minimal investigation seeking alternative normalization methods, which must be corrected to improve EMG application in sports. It is recognized that differing normalization methods will prevent cross-study comparisons. Users of EMG should aim to identify normalization methods that provide good reliability and a representative measure of muscle activation. The shortcomings of current normalization methods in high-velocity muscle actions assessment are evident. Advances in assessing alternate normalization methods have been done in cycling and sprinting. It is advised that when normalizing high-intensity muscle actions, isometric methods are used with caution and a dynamic alternative, where the muscle action is similar to that of the task is preferred. It is recognized that optimal normalization methods may be muscle and task dependent.
Validation and Repeatability of a Shoulder Biomechanics Data Collection Methodology and Instrumentation
Authors: Scibek Jason S. , Carcia Christopher R.
Published: August 2016

The purpose of our study was to establish criterion-related validity and repeatability of a shoulder biomechanics testing protocol involving an electromagnetic tracking system (Flock of Birds [FoB]). Eleven subjects completed humeral elevation tasks in the sagittal, scapular, and frontal planes on two occasions. Shoulder kinematics were assessed with a digital inclinometer and the FoB. Intrasession and intersession repeatability for orthopedic angles, and humeral and scapular kinematics ranged from moderate to excellent. Correlation analyses revealed strong relationships between inclinometer and FoB measures of humeral motion, yet considerable mean differences were noted between the measurement devices. Our results validate use of the FoB for measuring humeral kinematics and establish our testing protocol as reliable. We must continue to consider factors that can impact system accuracy and the effects they may have on kinematic descriptions and how data are reported.
Trunk Inclination Estimate During the Sprint Start Using an Inertial Measurement Unit: A Validation Study
Authors: Bergamini Elena , Guillon Pélagie , Camomilla Valentina , Pillet Hélène , Skalli Wafa , Cappozzo Aurelio
Published: August 2016

The proper execution of the sprint start is crucial in determining the performance during a sprint race. In this respect, when moving from the crouch to the upright position, trunk kinematics is a key element. The purpose of this study was to validate the use of a trunk-mounted inertial measurement unit (IMU) in estimating the trunk inclination and angular velocity in the sagittal plane during the sprint start. In-laboratory sprint starts were performed by five sprinters. The local acceleration and angular velocity components provided by the IMU were processed using an adaptive Kalman filter. The accuracy of the IMU inclination estimate and its consistency with trunk inclination were assessed using reference stereophotogrammetric measurements. A Bland-Altman analysis, carried out using parameters (minimum, maximum, and mean values) extracted from the time histories of the estimated variables, and curve similarity analysis (correlation coefficient > 0.99, root mean square difference < 7 deg) indicated the agreement between reference and IMU estimates, opening a promising scenario for an accurate in-field use of IMUs for sprint start performance assessment.
Peak Impact Accelerations during Track and Treadmill Running
Authors: Bigelow Erin M.R. , Elvin Niell G. , Elvin Alex A. , Arnoczky Steven P.
Published: August 2016

To determine whether peak vertical and horizontal impact accelerations were different while running on a track or on a treadmill, 12 healthy subjects (average age 32.8 ± 9.8 y), were fitted with a novel, wireless accelerometer capable of recording triaxial acceleration over time. The accelerometer was attached to a custom-made acrylic plate and secured at the level of the L5 vertebra via a tight fitting triathlon belt. Each subject ran 4 miles on a synthetic, indoor track at a self-selected pace and accelerations were recorded on three perpendicular axes. Seven days later, the subjects ran 4 miles on a treadmill set at the individual runner’s average pace on the track and the peak vertical and horizontal impact magnitudes between the track and treadmill were compared. There was no difference (P = .52) in the average peak vertical impact accelerations between the track and treadmill over the 4 mile run. However, peak horizontal impact accelerations were greater (P = .0012) on the track when compared with the treadmill. This study demonstrated the feasibility for long-term impact accelerations monitoring using a novel wireless accelerometer.
Unloading the Osteoarthritic Knee with a Novel Implant System
Authors: Gabriel Stefan M. , Clifford Anton G. , Maloney William J. , O’Connell Mary K. , Tornetta Paul
Published: August 2016

Medial knee osteoarthritis (OA) is a common disorder often associated with pathologic joint loading. Insoles, braces, and high tibial osteotomy are OA treatments aimed at reducing medial joint loads, but their use and effectiveness are limited. The KineSpring System implant also intends to reduce knee loads in OA patients while overcoming those limitations. The current study was undertaken to test the implant’s effect on loads at the knee. Six cadaver knees with Outerbridge Grade I-II medial OA were subjected to simulated gait using a kinematic test system. Knees were tested with and without the medial knee implant while thin film sensors measured medial and lateral femorotibial contact pressures. Significant medial compartment load reductions (134 ± 53 N [P= .002]) were found throughout the stance phase of gait in the treated knee. Significant total joint load decreases (91 ± 40 N [P= .002]) were also observed without substantial changes in lateral compartment loads. These significant reductions of medial and total intra-articular loads are also within clinically effective ranges of other unloading systems. This suggests that the KineSpring System could be a viable treatment for medial knee OA.
Force Application During Handcycling and Handrim Wheelchair Propulsion: An Initial Comparison
Authors: Arnet Ursina , van Drongelen Stefan , Veeger DirkJan , van der Woude Lucas H. V.
Published: August 2016

The aim of the study was to evaluate the external applied forces, the effectiveness of force application and the net shoulder moments of handcycling in comparison with handrim wheelchair propulsion at different inclines. Ten able-bodied men performed standardized exercises on a treadmill at inclines of 1%, 2.5% and 4% with an instrumented handbike and wheelchair that measured three-dimensional propulsion forces. The results showed that during handcycling significantly lower mean forces were applied at inclines of 2.5% (P < .001) and 4% (P < .001) and significantly lower peak forces were applied at all inclines (1%: P = .014, 2.5% and 4%: P < .001). At the 2.5% incline, where power output was the same for both devices, total forces (mean over trial) of 22.8 N and 27.5 N and peak forces of 40.1 N and 106.9 N were measured for handbike and wheelchair propulsion. The force effectiveness did not differ between the devices (P = .757); however, the effectiveness did increase with higher inclines during handcycling whereas it stayed constant over all inclines for wheelchair propulsion. The resulting peak net shoulder moments were lower for handcycling compared with wheelchair propulsion at all inclines (P < .001). These results confirm the assumption that handcycling is physically less straining.
Isokinetic Testing of Evertor and Invertor Muscles in Patients With Chronic Ankle Instability
Authors: David Pascal , Halimi Mohamad , Mora Isabelle , Doutrellot Pierre-Louis , Petitjean Michel
Published: August 2016

Ankle sprains are among the most common sport-related injuries and can lead to chronic ankle instability. Impaired sensorimotor function of the ankle musculature is often suggested as a cause. The current study sought to assess and compare the isokinetic performance and electromyographic patterns of evertor and invertor muscles in patients with chronic ankle instability and in a control group. Twelve patients with chronic ankle instability and twelve healthy subjects were included. Isokinetic eccentric and concentric testing at various angular velocities was performed for eversion and inversion movements. The corresponding myoelectric activities of the fibularis longus and tibialis anterior muscles were quantified from surface electromyographic recordings by computing average root mean square values. Patients had lower myoelectric activity of the evertor and invertor muscles than controls did; this difference could account for the eccentric weakness associated with ankle instability. Functional strength ratios revealed a dynamic strength imbalance in unstable ankle patients and that may contribute to recurrent injury. Our findings suggest that rehabilitation programs for unstable ankle patients must be focused on the motor control of eccentric contractions of the ankle evertors and invertors, to boost these muscles’ contribution to ankle stabilization.
Changes in Sprint Stride Kinematics with Age in Master’s Athletes
Authors: Hamilton Nancy
Published: August 2016

A study was undertaken to determine the kinematic nature of the decline in sprint velocity that has been found to occur with aging. Subjects included 162 Master’s sprinters ranging in age from 30 to 94 years. Data were collected at a national championship meet and a World Veterans Championships through use of videotape and the Peak Performance Motion Measurement System. From the digitized videotape data, measures of sprint stride velocity, stride length, stride period, support time, swing time, flight time, and hip, knee, and trunk range of motion were calculated. Velocity, stride length, flight time, swing time, and range of motion in the hip and knee all decreased significantly (p<.05) with age, whereas stride period and support time increased. Further, the proportional relationship between the components of the stride was significantly (p<.05) altered. From this it was inferred that as these sprinters aged there was a decreased ability to exert muscle force as well as a decreased ability to move quickly through a full range of lower extremity motion.
An Energy-Based Method for Testing Cushioning Durability of Running Shoes
Authors: Swigart John F. , Erdman Arthur G. , Cain Patrick J.
Published: August 2016

A new method for quantifying shoe cushioning durability was developed. This method used a computer-controlled, closed-loop materials testing system to subject the shoes to force-time profiles that were indicative of running. The change in the magnitude of the maximum energy absorbed by a shoe and the change in the magnitude of the energy balance of the shoe were quantified after the shoe had been worn running for a given distance. A shoe that changed very little in these quantities had a small energy wear factor and was deemed to have durable cushioning. The test method was roughly validated through comparison of three shoes of different midsole constructions with known relative durabilities. The shoes were tested at four simulated running speeds for energy properties when they were new and after they were run in for 161 km. The relative durabilities of the tested shoes were consistent with expectations based on the shoes' materials and constructions, showing that the new method has promise in predicting shoe cushioning durability, and thus more complete studies of the method may prove useful.
Effect of Plantar Flexor and Dorsiflexor Fatigue on Unilateral Postural Control
Authors: Lundin Thomas M. , Feuerbach Jon W. , Grabiner Mark D.
Published: August 2016

The purpose of this study was to determine the effect of plantar flexor and dorsiflexor fatigue on postural sway amplitude during unilateral, or one-legged, stance. It was hypothesized that plantar flexor and dorsiflexor fatigue would increase unilateral postural sway amplitude. Eight uninjured male subjects participated in pre- and postfatigue unilateral stability tests. Selected parameters describing medial-lateral (ML) and anterior-posterior (AP) postural sway were measured on a Chattecx Balance System before and after an isokinetic fatigue protocol. The fatigue protocol resulted in a significant increase in ML postural sway amplitude (p< 0.05) and an increase in AP sway amplitude (p= 0.065). Previously, links have been established between increased postural sway amplitude and ankle joint injury. Thus, fatigue of the plantar flexors and dorsiflexors, which increased postural sway amplitude, may render the ankle joint susceptible to injury. Induced ankle muscle fatigue may represent a valid paradigm to study the causes of traumatic ankle joint injury.
Stroking Characteristics of Front Crawl Swimming during Exercise
Authors: Keskinen Kari L. , Komi Paavo V.
Published: August 2016

The purpose of this study was to examine the differences in the relationships among the stroking characteristics between different phases of swimming exercises, and to determine whether these relationships would change in relation to enhanced swimming intensity. The experimental design consisted of the measurement of mean velocity (V), stroke rate (SR), stroke length (SL), and duration of different phases of a stroke cycle for each pool length in five to six 400-m swims and two 100-m swims. The results showed that the basic relationships among the stroke parameters during the test exercises were almost similar to those observed in competition. However, the relationships changed with enhanced swimming intensity. It is suggested that the degree of anaerobic lactacid metabolism may determine the characteristics of stroking while swimming. The reduction of SL above the lactate threshold would be connected to the accumulation of blood lactate, whereas SR would primarily be determined by the ability to maintain adequate neural activation.
Body Roll and Handpath in Freestyle Swimming: A Computer Simulation Study
Authors: Hay James G. , Liu Qi , Andrews James G.
Published: August 2016

The purpose of this study was to determine the effect that body roll has on the path followed by the hand during the pull phase in freestyle swimming. The trunk and right arm were modeled as two rigid segments joined at the shoulder by a simple hinge joint. The arm segment was assigned an elbow flexion angle, and the hand was made to move in a plane through the shoulder parallel to the sagittal plane of the rotating trunk. Shoulder extension and trunk roll occurred simultaneously at selected rates. Medial deviations of the hand to the midline of the trunk can be obtained with body roll alone and require less roll than is usually observed among competitive swimmers. When body roll exceeds the amount necessary to produce the desired medial deviation of the hand, the swimmer must move the arm away from, rather than toward, the trunk's midline.
Body Roll and Handpath in Freestyle Swimming: An Experimental Study
Authors: Liu Qi , Hay James G. , Andrews James G.
Published: August 2016

The purpose of this study was to determine the influence of (a) body roll, and (b) the motion of the arm relative to the trunk, on the medial-lateral component of the path followed by the hand during the pull phase in freestyle swimming. Ten male swimmers swam three trials of freestyle at a long-distance workout pace. Three-dimensional (3D) underwater videography was used to record the body roll angle-time history and the path followed by the hand during the pull phase. A mathematical model was used to characterize the motion of a swimmer's right upper limb in accord with 3D data from the videotape images, and to determine what the path of the hand would have been as a result of body roll alone. The contribution of body roll to the actual handpath was found to be nearly equal to the contribution of medial-lateral motions of the hand relative to the trunk.