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- Coordination and variability in the elite female tennis serve. [JOURNAL ARTICLE]
- J Sports Sci 2014 Oct 30.:1-12.
Abstract Enhancing the understanding of coordination and variability in the tennis serve may be of interest to coaches as they work with players to improve performance. The current study examined coordinated joint rotations and variability in the lower limbs, trunk, serving arm and ball location in the elite female tennis serve. Pre-pubescent, pubescent and adult players performed maximal effort flat serves while a 22-camera 500 Hz motion analysis system captured three-dimensional body kinematics. Coordinated joint rotations in the lower limbs and trunk appeared most consistent at the time players left the ground, suggesting that they coordinate the proximal elements of the kinematic chain to ensure that they leave the ground at a consistent time, in a consistent posture. Variability in the two degrees of freedom at the elbow became significantly greater closer to impact in adults, possibly illustrating the mechanical adjustments (compensation) these players employed to manage the changing impact location from serve to serve. Despite the variable ball toss, the temporal composition of the serve was highly consistent and supports previous assertions that players use the location of the ball to regulate their movement. Future work should consider these associations in other populations, while coaches may use the current findings to improve female serve performance.
- Pushrim biomechanical changes with progressive increases in slope during motorized treadmill manual wheelchair propulsion in individuals with spinal cord injury. [JOURNAL ARTICLE]
- J Rehabil Res Dev 2014; 51(5):789-802.
The purpose of this study was to quantify the effects of five distinct slopes on spatiotemporal and pushrim kinetic measures at the nondominant upper limb during manual wheelchair (MWC) propulsion on a motorized treadmill in individuals with spinal cord injury (SCI). Eighteen participants with SCI propelled their MWC at a self-selected natural speed on a treadmill at different slopes (0, 2.7, 3.6, 4.8, and 7.1 degrees). Spatiotemporal parameters along with total force and tangential components of the force applied to the pushrim, including mechanical effective force, were calculated using an instrumented wheel. The duration of the recovery phase was 54% to 70% faster as the slope increased, whereas the duration of the push phase remained similar. The initial contact angles migrated forward on the pushrim, while the final and total contact angles remained similar as the slope increased. As the slope increased, the mean total force was 93% to 201% higher and the mean tangential component of the force was 96% to 176% higher than propulsion with no slope. Measures were similar for the 2.7 and 3.6 degrees slopes. Overall, the recovery phase became shorter and the forces applied at the pushrim became greater as the slope of the treadmill increased during motorized treadmill MWC propulsion.
- Normative data for modified Box and Blocks test measuring upper-limb function via motion capture. [JOURNAL ARTICLE]
- J Rehabil Res Dev 2014; 51(6):918-932.
Motion analysis is an important tool for examining upper-limb function. Based on previous work demonstrating a modified Box and Blocks (BB) test with motion capture to assess prosthetic performance, we collected data in 16 nondisabled participants to establish normative kinematics for this test. Four motions of the modified BB test were analyzed to establish kinematic data for upper-limb and trunk motion. The test was repeated for right and left arms in standing and seated positions. Data were compared using a nonparametric Friedman test. No differences were found between right- and left-hand performance other than for task completion time. Small but significant differences were found for standing and seated performance, with slightly greater ranges in standing for axial trunk rotation, medial-lateral sternum displacement, and anterior-posterior hand displacement. The kinematic trajectories, however, were very consistent. The consistency in our nondisabled data suggests that normative kinematic trajectories can be defined for this task. This motion capture procedure may add to the understanding of movement in upper-limb impairment and may be useful for measuring the effect of interventions to improve upper-limb function.
- Wearable inertial sensors in swimming motion analysis: a systematic review. [JOURNAL ARTICLE]
- J Sports Sci 2014 Oct 30.:1-14.
Abstract The use of contemporary technology is widely recognised as a key tool for enhancing competitive performance in swimming. Video analysis is traditionally used by coaches to acquire reliable biomechanical data about swimming performance; however, this approach requires a huge computational effort, thus introducing a delay in providing quantitative information. Inertial and magnetic sensors, including accelerometers, gyroscopes and magnetometers, have been recently introduced to assess the biomechanics of swimming performance. Research in this field has attracted a great deal of interest in the last decade due to the gradual improvement of the performance of sensors and the decreasing cost of miniaturised wearable devices. With the aim of describing the state of the art of current developments in this area, a systematic review of the existing methods was performed using the following databases: PubMed, ISI Web of Knowledge, IEEE Xplore, Google Scholar, Scopus and Science Direct. Twenty-seven articles published in indexed journals and conference proceedings, focusing on the biomechanical analysis of swimming by means of inertial sensors were reviewed. The articles were categorised according to sensor's specification, anatomical sites where the sensors were attached, experimental design and applications for the analysis of swimming performance. Results indicate that inertial sensors are reliable tools for swimming biomechanical analyses.
- Prevalence of heat and perspiration discomfort inside prostheses: Literature review. [JOURNAL ARTICLE]
- J Rehabil Res Dev 2014; 51(6):855-868.
People with limb amputation deal with thermal stresses in their daily activities. Unfortunately, in the majority of this population, all thermal transfer mechanisms, including convection, radiation, evaporation, and conduction, can be disturbed due to the prosthetic socket barrier, decreased body surface area, and/or vascular disease. The thermal environment inside prosthetic sockets, in addition to decreased quality of life and prosthesis use, comfort, and satisfaction, could endanger people with amputation with a high risk of skin irritations. The current review explores the importance of thermal and perspiration discomfort inside prosthetic sockets by providing an insight into the prevalence of the problem. The literature search was performed in two databases, PubMed and Web of Knowledge, to find relevant articles. After considering the review criteria and hand-searching the reference sections of the selected studies, 38 studies were listed for review and data extraction. This review revealed that more than 53% of people with amputation in the selected studies experienced heat and/or perspiration discomfort inside their prostheses. In spite of great technological advances, current prostheses are unable to resolve this problem. Therefore, more attention must be paid by researchers, clinicians, and manufacturers of prosthetic components to thermal-related biomechanics of soft tissues, proper fabrication technique, material selection, and introduction of efficient thermoregulatory systems.
- Influence of the Mechanical Environment on the Engineering of Mineralised Tissues Using Human Dental Pulp Stem Cells and Silk Fibroin Scaffolds. [JOURNAL ARTICLE]
- PLoS One 2014; 9(10):e111010.
Teeth constitute a promising source of stem cells that can be used for tissue engineering and regenerative medicine purposes. Bone loss in the craniofacial complex due to pathological conditions and severe injuries could be treated with new materials combined with human dental pulp stem cells (hDPSCs) that have the same embryonic origin as craniofacial bones. Optimising combinations of scaffolds, cells, growth factors and culture conditions still remains a great challenge. In the present study, we evaluate the mineralisation potential of hDPSCs seeded on porous silk fibroin scaffolds in a mechanically dynamic environment provided by spinner flask bioreactors. Cell-seeded scaffolds were cultured in either standard or osteogenic media in both static and dynamic conditions for 47 days. Histological analysis and micro-computed tomography of the samples showed low levels of mineralisation when samples were cultured in static conditions (0.16±0.1 BV/TV%), while their culture in a dynamic environment with osteogenic medium and weekly µCT scans (4.9±1.6 BV/TV%) significantly increased the formation of homogeneously mineralised structures, which was also confirmed by the elevated calcium levels (4.5±1.0 vs. 8.8±1.7 mg/mL). Molecular analysis of the samples showed that the expression of tooth correlated genes such as Dentin Sialophosphoprotein and Nestin were downregulated by a factor of 6.7 and 7.4, respectively, in hDPSCs when cultured in presence of osteogenic medium. This finding indicates that hDPSCs are able to adopt a non-dental identity by changing the culture conditions only. Also an increased expression of Osteocalcin (1.4x) and Collagen type I (1.7x) was found after culture under mechanically dynamic conditions in control medium. In conclusion, the combination of hDPSCs and silk scaffolds cultured under mechanical loading in spinner flask bioreactors could offer a novel and promising approach for bone tissue engineering where appropriate and rapid bone regeneration in mechanically loaded tissues is required.
- Comparison of the Clinical and Radiographic Results between Cervical Artificial Disc Replacement and Anterior Cervical Fusion: A Six-year Prospective Non-randomized Comparative Study. [JOURNAL ARTICLE]
- J Spinal Disord Tech 2014 Oct 28.
Prospective non-randomized comparative study.To compare the long-term clinical and radiographic results of cervical artificial disc replacement (CADR) and anterior cervical discectomy and fusion (ACDF), and to provide our evidence whether CADR could reduce adjacent segment degeneration (ASD).CADR is widely used in spine surgery today. In spite of the short-term results of it having been ascertained, the long-term results are still under observation. Meanwhile it is still debatable whether CADR could reduce ASD in the long run.Sixty-three patients with cervical myelopathy who underwent CADR (28) or ACDF (35) with a minimum follow-up of 68 months were included. JOA score, NDI and Odom's scale were used to evaluate the clinical outcomes. Radiographs, computed tomography and MRI were used to evaluate the radiographic outcomes.Both CADR and ACDF groups showed significant improvement on JOA scores and NDI, and there was no significant difference between two groups. The sagittal alignment was maintained for both groups. The C2-C7 ROM had no significant change for CADR group, whereas, it significantly decreased for ACDF group. The ROM at index level of CADR patients decreased from (9.5±3.7)° before surgery to (7.0±3.0)° at 3 months after surgery (P<0.001), and it was maintained to (6.6±4.1)° at last follow-up without significant decrease (P=0.448). We used radiographic data to evaluate ASD and we found the incidence of ASD was significantly lower for CADR group than ACDF group.The clinical and radiographic results of CADR over 6 years follow-up are basically satisfying. Compared with ACDF, CADR could better preserve physiological motion and biomechanics of cervical spine, and reduce the occurrence of ASD.
- Lower-Extremity Biomechanics and Maintenance of Vertical-Jump Height During Prolonged Intermittent Exercise. [JOURNAL ARTICLE]
- J Sport Rehabil 2014 Nov; 23(4):319-329.
Context: Potential biomechanical compensations allowing for maintenance of maximal explosive performance during prolonged intermittent exercise, with respect to the corresponding rise in injury rates during the later stages of exercise or competition, are relatively unknown. Objective: To identify lower-extremity countermovement-jump (CMJ) biomechanical factors using a principal-components approach and then examine how these factors changed during a 90-min intermittent-exercise protocol (IEP) while maintaining maximal jump height. Design: Mixed-model design. Setting: Laboratory. Participants: Fifty-nine intermittent-sport athletes (30 male, 29 female) participated in experimental and control conditions. Interventions: Before and after a dynamic warm-up and every 15 min during the 1st and 2nd halves of an individually prescribed 90-min IEP, participants were assessed on rating of perceived exertion, sprint/cut speed, and 3-dimensional CMJ biomechanics (experimental). On a separate day, the same measures were obtained every 15 min during 90 min of quiet rest (control). Main Outcome Measures: Univariate piecewise growth models analyzed progressive changes in CMJ performance and biomechanical factors extracted from a principal-components analysis of the individual biomechanical dependent variables. Results: While CMJ height was maintained during the 1st and 2nd halves, the body descended less and knee kinetic and energetic magnitudes decreased as the IEP progressed. Conclusions: The results indicate that vertical-jump performance is maintained along with progressive biomechanical changes commonly associated with decreased performance. A better understanding of lower-extremity biomechanics during explosive actions in response to IEP allows us to further develop and individualize performance training programs.
- TECHNICAL ACTIVITY PROFILE AND INFLUENCE OF BODY ANTHROPOMETRY ON PLAYING PERFORMANCE IN FEMALE ELITE TEAM HANDBALL. [JOURNAL ARTICLE]
- J Strength Cond Res 2014 Oct 28.
To determine the physical demands placed on female elite team handball players in relation to playing position and body anthropometry, female elite team handball primarily field players were monitored during match-play using video recording and subsequent computerized technical match analysis during five regular tournament match seasons. Technical match activities were distributed in 6 major types of playing actions (shots, breakthroughs, fast breaks, technical errors, defensive errors and tackles) and further divided into various subcategories (e.g., type of shot, hard or light tackles, claspings, screenings and blockings). Furthermore, anthropometric measurements were carried out.Each player had 28.3±11.0 (group means±SD) high-intense playing actions per match with a total effective playing time of 50.70±5.83 min. On average, each player made 2.8±2.6 fast breaks, gave 7.9±14.4 screenings, received 14.6±9.2 tackles in total and performed 7.7±3.7 shots while in offense, along with 3.5±3.8 blockings, 1.9±2.7 claspings and 6.2±3.8 hard tackles in defense. Mean body height, body mass and age in the Danish Premier Female Handball League were 175.4±6.1 cm, 69.5±6.5 kg and 25.4±3.7 years, respectively. Wing players were lighter (63.5±4.8 kg, p<0.001) and smaller (169.3±4.9 cm, p<0.001) than backcourt players (70.6±5.3 kg, 177.0±5.4 cm) and pivots (72.5±4.9 kg, 177.7±4.9 cm).In conclusion, the present match observations revealed that female elite team handball players during competitive games intermittently perform a high number of short-term, high-intense technical playing actions making modern female elite team handball a physically demanding team sport. No sign of technical fatigue were observed, since the amount of intense technical playing actions remained unchanged in the second half. Marked positional differences in the physical demands were demonstrated, with wing players performing more fast breaks and less physical confrontations than backcourt players and pivots. Body anthropometry differed substantially between different playing positions. Consequently, this should lead to an increase in physical training in modern female elite team handball directed at specific positions and individual physical capacity.
- Biomechanics and force system of butterfly arch: A device for three-dimensional controlling of upper molars. [Journal Article]
- J Dent Biomech 2014.:1758736014552149.
There are numerous intra-oral appliances that are used for many purposes in orthodontic practice. Some popular instances include those for anchorage preservation, distalizing plates, and expansion appliances. In maximum anchorage extraction cases, which are serious challenges for orthodontists, none of intra-oral devices can preserve the anchorage precisely. Butterfly arch with its unique design, configuration, and biomechanical properties is introduced here as a device that could enhance the posterior anchorage meticulously. In addition, there are several advantages mentioned here to present the importance of the appliance to preserve the vertical and transverse dimensions as well.