Factors related to intra-tendinous morphology of Achilles tendon in runners

The purpose of this study was to determine and explore factors (age, sex, anthropometry, running and injury/pain history, tendon gross morphology, neovascularization, ankle range of motion, and ankle plantarflexor muscle endurance) related to intra-tendinous morphological alterations of the Achilles tendon in runners. An intra-tendinous morphological change was defined as collagen fiber disorganization detected by a low peak spatial frequency radius (PSFR) obtained from spatial frequency analysis (SFA) techniques in sonography. Ninety-one runners (53 males and 38 females; 37.9 ± 11.6 years) with 8.8 ± 7.3 years of running experience participated. Height, weight, and waist and hip circumferences were recorded. Participants completed a survey about running and injury/pain history and the Victorian Institute of Sport Assessment-Achilles (VISA-A) survey. Heel raise endurance and knee-to-wall composite dorsiflexion were assessed. Brightness-mode (B-mode) sonographic images were captured longitudinally and transversely on the Achilles tendon bilaterally. Sonographic images were analyzed for gross morphology (i.e., cross-sectional area [CSA]), neovascularization, and intra-tendinous morphology (i.e., PSFR) for each participant. The factors associated with altered intra-tendinous morphology of the Achilles tendon were analyzed using a generalized linear mixed model. Multivariate analyses revealed that male sex was significantly associated with a decreased PSFR. Additionally, male sex and the presence of current Achilles tendon pain were found to be significantly related to decreased PSFR using a univariate analysis. Our findings suggested that male sex and presence of current Achilles tendon pain were related to intra-tendinous morphological alterations in the Achilles tendon of runners.

Achilles tendon morphology assessed using image based spatial frequency analysis is altered among healthy elite adolescent athletes compared to recreationally active controls

OBJECTIVES

Although expected, tendon adaptations in adolescent elite athletes have been underreported. Morphologically, adaptations may occur by an increase in collagen fiber density and/or organization. These characteristics can be captured using spatial frequency parameters extracted from ultrasound images. This study aims to compare Achilles tendon (AT) morphology among sports-specific cohorts of elite adolescent athletes and to compare these findings to recreationally active controls by use of spatial frequency analysis.

DESIGN

Cross-sectional observational study.

METHOD

In total, 334 healthy adolescent athletes from four sport categories (ball, combat, endurance, explosive strength) and 35 healthy controls were included. Longitudinal ultrasound scans were performed at the AT insertion and midportion. Intra-tendinous-morphology was quantified by performing spatial frequency analysis assessing eight parameters at standardized ROIs. Increased values in five parameters suggest a higher structural organization, and in two parameters higher fiber density. One parameter represents a quotient combining both organization and fiber density.

RESULTS

Among athletes, only ball sport athletes exhibited an increase in one summative parameter at pre-insertion site compared to athletes from other sport categories. When compared to athletes, controls had significantly higher values of four parameters at pre-insertion and three parameters at midportion site reflecting differences in both, fiber organization and density.

CONCLUSIONS

Intra-tendinous-morphology was similar in all groups of adolescent athletes. Higher values found in non-athletes might suggest higher AT fiber density and organization. It is yet unclear whether the lesser structural organization in young athletes represents initial AT pathology, or a physiological adaptive response at the fiber cross-linking level.

Movement variability response to change in the rate of hopping

Movement variability is often considered undesirable, but growing evidence demonstrates positive aspects of variability. During unipedal hopping, control of limb stiffness and limb length are paramount.

PURPOSE

The purpose of this study was to compare two methods of measuring movement variability that provide information at the task level, and their capacities to illuminate the neuromotor control system's response to change in hopping rate.

METHODS

The typical task-level movement variability measure of the standard deviation of vertical limb length was compared to uncontrolled manifold analysis. We examined the relationship between change scores in deviation from spring-mass model-type behavior and these two variability measures for the shift from typical (2.3 Hz) to slow (1.7 Hz) hopping.

RESULTS

The change scores for deviation from spring-mass model-type behavior and vertical limb length standard deviation demonstrated no correlation ( p = 0.784, R = 0.051). In contrast, the change scores for deviation from spring-mass model-type behavior and the uncontrolled manifold analysis measure demonstrated a moderate correlation ( p = 0.004, R = 0.502).

CONCLUSIONS

Uncontrolled manifold analysis considers not just variability in the sense of error, but illustrates how the neuromotor control system distributes movement variability into performance-irrelevant and performance-destabilizing subspaces. As such, this type of analysis may be more effective at illuminating global control aspects of movement variability than the typical variability measure of limb length standard deviation.

Interlimb Force Coordination in Bipedal Dance Jumps: Comparison Between Experts and Novices

Bipedal tasks require interlimb coordination that improves with practice and acquisition of skills. The purpose of this study was to compare interlimb force coordination during dance-specific rate-controlled consecutive bipedal jumps (sautés) between expert dancers and nondancers. To analyze coordination of vertical ground reaction forces recorded under each leg, the vector coding approach was used. Although there were no differences in the patterns of interlimb force coordination between groups, the dancers exhibited less variability of interlimb force coordination during the transition phase from weight acceptance to propulsion as well as during the propulsion phase itself. The interlimb force coordination variability was associated with task performance only during the transition phase, which highlights the potential importance of control during this phase. In conclusion, expert dancers were better at reducing interlimb force coordination variability during the task-relevant transition phase, which was related to better performance at maintaining jump rate and jump height consistency.

Heeled Shoes Increase Knee Work Demand During Repeated Hopping in Dancers

AIMS

Dancers have high injury rates of the lower extremity. External factors such as footwear likely alter the work demands placed on the lower extremity joints when performing dance-style movements. Research on pedestrians shows an increase in knee work demand when wearing heels, which may occur in dancers as well. The purpose of this study was to assess the effect of heeled shoes on lower extremity joint work demand during a basic dance-specific jump (sauté) in dancers when compared to barefoot.

METHODS

Ten healthy, female dancers (age 25.6±4.7 yrs; height 1.7±0.1 m; weight 64.9±9.2 kg; mean years of dance training 17.6±6.4) performed repetitive vertical bipedal dance jumps (sautés) barefoot as well as wearing heeled dance shoes. Sagittal plane hip, knee, and ankle kinetics were calculated. Percentages of work done by these joints were calculated in comparison to the work done by the leg as a whole and compared between the two conditions.

RESULTS

During a dance-specific jump, the percent contribution of energy absorption was significantly different at the ankle and knee between the two conditions. The ankle contribution decreased from 50.7±6.1% in the bare condition to 34.9±5.3% in the shod condition (p=0.002), and the knee contribution increased from 38.6±3.9% barefoot to 55.1±2.8% shod (p=0.002). The same pattern was seen for energy generation, with the ankle contribution decreasing from 48.1±7.3% to 35.6±6.9% and the knee contribution increasing from 43.3±5.6% to 56.4±6.1% in the bare vs shod condition (both p=0.002). There was no significant difference in the percent contribution from the hip.

CONCLUSION

With heeled shoes, there is a shift in work demand from the ankle to the knee with no change at the hip as compared to barefoot.

Changing one's focus of attention alters the structure of movement variability

Substantial evidence supports the beneficial effect of an external (vs. internal) focus of attention on task performance during goal-directed movements. Counter-intuitively, an external focus has also been shown to increase joint-level movement variability.

OBJECTIVE

To determine whether shifting attentional focus can alter the structure of movement variability, thereby offering a probable mechanistic explanation for how adopting an external focus of attention might confer its benefits.

METHODS

Thirty-five healthy adults (age 23-55) performed unipedal hopping under three different attentional foci: natural (no directed focus), internal focus, and external focus. Uncontrolled manifold analysis was used to examine the structure of movement variability with respect to stabilization of leg orientation and vertical leg length during hopping. Takeoff/landing event bin and stance phase integrals of performance-irrelevant and performance-destabilizing variability were compared across focus conditions.

RESULTS

Accuracy of hopping in place improved with both external and internal foci compared to the natural condition (.004 ≤ p ≤ .035). External focus, to a greater degree than internal focus, destabilized leg orientation at takeoff and landing compared to the natural condition (.001 ≤ p ≤ .038). External focus increased - but internal focus decreased - leg length stabilization throughout stance compared to the natural condition (p < .001).

CONCLUSION

External focus was superior to internal and natural focus conditions in terms of increasing flexibility within the system to orient the leg differently at takeoff and landing to compensate for unintentional drift during hopping. An external focus increased leg length stabilization in stance by preferentially increasing the subset of variability that explores multiple successful performance options. These results provide an understanding of the mechanism underlying external focus benefits - improving movement variability/coordination.

Characterizing the balance-dexterity task as a concurrent bipedal task to investigate trunk control during dynamic balance

The purpose of the study was to characterize the Balance-Dexterity Task as a means to investigate a concurrent bipedal lower-extremity task and trunk control during dynamic balance. The task combines aspects of single-limb balance and the lower-extremity dexterity test by asking participants to stand on one limb while compressing an unstable spring with the contralateral limb to an individualized target force. Nineteen non-disabled participants completed the study, and performance measures for the demands of each limb - balance and dexterous force control - as well as kinematic and electromyographic measures of trunk control were collected. Given five practice trials, participants achieved compression forces ranging from 100 to 139 N (mean 121.2 ± 12.3 N), representing 14.4-23.0% of body weight (mean 18.7 ± 2.4%), which were then presented as target forces during test trials. Dexterous force control coefficient of variation and average magnitude of the center of pressure (COP) resultant velocity were associated such that greater variability in force control was accompanied by greater COP velocity (R = 0.598, p = 0.007). Trunk coupling, quantified as the coefficient of determination (R²) of a frontal plane thorax and pelvis angle-angle plot, varied independently of any measure of balance or dexterous force control. The Balance-Dexterity Task is a continuous, dynamic balance task where bipedal coordination and trunk coupling can be concurrently observed and studied.

Distributed representation of pelvic floor muscles in human motor cortex

Human motor cortex can activate pelvic floor muscles (PFM), but the motor cortical representation of the PFM is not well characterized. PFM representation is thought to be focused in the supplementary motor area (SMA). Here we examine the degree to which PFM representation is distributed between SMA and the primary motor cortex (M1), and how this representation is utilized to activate the PFM in different coordination patterns. We show that two types of coordination patterns involving PFM can be voluntarily accessed: one activates PFM independently of synergists and a second activates PFM prior to and in proportion with synergists (in this study, the gluteus maximus muscle - GMM). Functional magnetic resonance imaging (fMRI) showed that both coordination patterns involve overlapping activation in SMA and M1, suggesting the presence of intermingled but independent neural populations that access the different patterns. Transcranial magnetic stimulation (TMS) confirmed SMA and M1 representation for the PFM. TMS also showed that, equally for SMA and M1, PFM can be activated during rest but GMM can only be activated after voluntary drive to GMM, suggesting that these populations are distinguished by activation threshold. We conclude that PFM representation is broadly distributed in SMA and M1 in humans.

The influence of divided attention on walking turns: Effects on gait control in young adults with and without a history of low back pain

The cognitive control of gait is altered in individuals with low back pain, but it is unclear if this alteration persists between painful episodes. Locomotor perturbations such as walking turns may provide a sensitive measure of gait adaptation during divided attention in young adults. The purpose of this study was to investigate changes in gait during turns performed with divided attention, and to compare healthy young adults with asymptomatic individuals who have a history of recurrent low back pain (rLBP). Twenty-eight participants performed 90° ipsilateral walking turns at a controlled speed of 1.5m/s. During the divided attention condition they concurrently performed a verbal 2-back task. Step length and width, trunk-pelvis and hip excursion, inter-segmental coordination and stride-to-stride variability were quantified using motion capture. Mixed-model ANOVA were used to examine the effect of divided attention and group, and interaction effects on the selected variables. Step length variability decreased significantly with divided attention in the healthy group but not in the rLBP group (post-hoc p=0.024). Inter-segmental coordination variability was significantly decreased during divided attention (main effect of condition p <0.000). There were small but significant reductions in hip axial and sagittal motion across groups (main effect of condition p=0.044 and p=0.040 respectively), and a trend toward increased frontal motion in the rLBP group only (post-hoc p=0.048). These findings suggest that the ability to switch attentional resources during gait is altered in young adults with a history of rLBP, even between symptomatic episodes.

Lower Extremity Biomechanical Demands During Saut de Chat Leaps

In dance, high demands are placed on the lower extremity joints during jumping tasks. The purpose of this study was to compare biomechanical demands placed on the lower extremity joints during the takeoff and landing phases of saut de chat leaps.

METHODS

Thirty healthy, experienced dancers with 20.8±4.9 yrs of dance training performed 5 saut de chat leaps. A three-dimensional motion analysis system and force plates were used to collect kinematic and kinetic data. Ground reaction force (GRF) peaks and impulse and sagittal plane kinematics and kinetics of the hip, knee, ankle, and metatarsophalangeal (MTP) joints were calculated for the takeoff and landing phases of each leap.

RESULTS

Saut de chat takeoffs demonstrated greater braking GRF impulse (p<0.001), while landings demonstrated greater peak vertical GRF (p<0.001). During takeoff, greater kinetic demands were placed on the MTP (p<0.001) and ankle (p<0.001) joints, while during landing greater kinetic demands were placed on the hip (p=0.037) joint.

CONCLUSIONS

Both the takeoff and landing phases of saut de chat leaps place significant demands on a dancer's body. Takeoff involves greater demands on the more distal joints and requires more braking forces, while the landing phase involves greater demands on the more proximal joints of the lower extremity and requires the dancer to absorb more vertical force. These demands, combined with extensive repetition of movements during training, may contribute to the high number of chronic injuries seen in dance.

Changes in water content in response to an acute bout of eccentric loading in a patellar tendon with a history of tendinopathy: A case report

OBJECTIVE

This case-based report assessed resting water content and exercise-driven water exchange within a tendon with a history of tendinopathy and compared the response to that of a healthy uninvolved tendon.

DESIGN

Case Report.

SETTING

University imaging center.

PARTICIPANT

The participant was a 27-year-old female basketball player 39 months following knee trauma. Patellar tendinopathy developed 12 months after the injury episode and was treated with eccentric exercises. Eighteen months from the beginning of the first eccentric training bout, the participant reported full resolution of symptoms and returned to her pre-injury sport participation without symptoms.

INTERVENTION

Eccentric decline squat exercise.

MAIN OUTCOME MEASURES

Tendon water content obtained from magnetic resonance imaging (MRI).

RESULTS

MRI acquired 39 months post-injury demonstrated increased resting water content of the involved tendon (involved: 91.1% vs. uninvolved: 84.6%). Immediately after the eccentric squat maneuver, water content decreased on both involved and uninvolved tendons (involved: 89.5% vs. uninvolved: 83.3%).

CONCLUSIONS

Elevated resting water content of the involved tendon found in this report may be indicative of reduced tendon stiffness. A similar amount of water content reduction was observed on both sides following mechanical loading, suggesting that the involved tendon may respond to the eccentric exercise similarly to the uninvolved tendon. Future investigations are needed to study the relationships among tendon water exchanges, mechanical properties, patient symptoms, and tissue injuries.

How should we teach lumbar manipulation? A consensus study

BACKGROUND

Spinal manipulation is an effective intervention for low back pain, yet there is little consistency in how this skill is taught.

OBJECTIVES

The purpose of this study was to identify what educators and clinicians believe are important characteristics of the patient and operator position prior to side-lying lumbar manipulation and the patient position and operator motion during the manipulative thrust.

DESIGN

A multi-disciplinary correspondence-based Delphi method.

METHODS

Three rounds of questionnaires were sent to physical therapists, osteopaths and chiropractors. Consensus was established in Round 3 if at least 75% of respondents identified a characteristic as very important/extremely important on a 5-point Likert scale.

RESULTS

265 educators and clinicians completed the three rounds of questioning. There was consensus that localization to target segment, patient comfort, table height, and logrolling the patient towards the operator are important characteristics of patient position during the preparatory phase. During the manipulation phase, respondents agreed that it is important to maintain localization to the segment and rotate the patient's pelvis and lumbar spine. For the operator characteristics, consensus was reached for the following items; moving up and over the patient, maintaining contact using forearms, and close contact between the operator and patient (preparatory phase); generating force through the body and legs, dropping the body downwards, maintaining localization, and providing a high-velocity and low-amplitude thrust (manipulation phase).

CONCLUSIONS

This Delphi study successfully identified key characteristics of patient position and operator position and motion for effective delivery of side-lying lumbar spine manipulations.

Trunk-pelvis coordination during turning: A cross sectional study of young adults with and without a history of low back pain

BACKGROUND

During steady-state locomotion, symptomatic individuals with low back pain demonstrate reduced ability to modulate coordination between the trunk and the pelvis in the axial plane. It is unclear if this is also true during functional locomotor perturbations such as changing direction, or if this change in coordination adaptability persists between symptomatic episodes. The purpose of this study was to compare trunk-pelvis coordination during walking turns in healthy individuals and asymptomatic individuals with a history of low back pain.

METHODS

Participants performed multiple ipsilateral turns. Axial plane inter-segmental coordination and stride-to-stride coordination variability were quantified using the vector coding technique. Frequency of coordination mode and amplitude of coordination variability was compared between groups using Wilcoxon signed-rank tests and paired t-tests respectively.

FINDINGS

During stance phase of the turn, there was no significant difference in either inter-segmental coordination or coordination variability between groups. Inter-segmental coordination between the trunk and the pelvis was predominantly inphase during this part of the turn. During swing phase, patterns of coordination were more diversified, and individuals with a history of low back pain had significantly greater trunk phase coordination than healthy controls. Coordination variability was the same in both groups.

INTERPRETATION

Changes in trunk-pelvis coordination are evident between symptomatic episodes in individuals with a history of low back pain. However, previously demonstrated decreases in coordination variability were not found between symptomatic episodes in individuals with recurrent low back pain and therefore may represent a response to concurrent pain rather than a persistent change in motor control.

Ultrasound-Based Tendon Micromorphology Predicts Mechanical Characteristics of Degenerated Tendons

The purpose of this study was to explore the relationship between tendon micro-morphology quantified from a sonogram and tendon mechanical characteristics measured in vivo. Nineteen adults (nine with unilateral Achilles tendinosis) participated. A commercial ultrasound scanner was used to capture longitudinal B-mode ultrasound images from the mid-portion of bilateral Achilles tendons and a custom image analysis program was used to analyze the spatial frequency content of manually defined regions of interest; in particular, the average peak spatial frequency of the regions of interest was acquired. In addition, a dynamometer and a motion analysis system indirectly measured the tendon mechanical (stiffness) and material (elastic modulus) properties. The peak spatial frequency correlated with tendon stiffness (r = 0.74, p = 0.02) and elastic modulus (r = 0.65, p = 0.05) in degenerated tendons, but not healthy tendons. This is the first study relating the mechanical characteristics of degenerated human Achilles tendon using a non-invasive micro-morphology analysis approach.

Kinematic and kinetic analyses of the toes in dance movements

Due to the significant amount of time dancers spend on the forefoot, loads on the metatarsophalangeal joints are likely high, yet vary between dance movements. The purpose of this study was to compare joint motion and net joint moments at the metatarsophalangeal joints during three different dance movements ranging in demands at the foot and ankle joints. Ten healthy, female dancers (27.6 ± 3.2 years; 56.3 ± 6.9 kg; 1.6 ± 0.1 m) with an average 21.7 ± 4.9 years of dance training performed relevés (rising up onto the toes), sautés (vertical bipedal jumps), and saut de chat leaps (split jumps involving both vertical and horizontal components). Metatarsophalangeal joint kinematics and kinetics in the sagittal plane were calculated. Total excursion and peak net joint moments during rising or push-off were compared between the three dance movements. Greater extension of the metatarsophalangeal joints was seen during relevés compared to sautés or saut de chat leaps, and the largest metatarsophalangeal net joint moments were seen during saut de chat leaps. The metatarsophalangeal joints frequently and repetitively manage external loads and substantial metatarsophalangeal extension during these three dance movements, which may contribute to the high rate of foot and ankle injuries in dancers.

Physical therapists' role in prevention and management of patellar tendinopathy injuries in youth, collegiate, and middle-aged indoor volleyball athletes

Patellar tendinopathy is highly prevalent in all ages and skill levels of volleyball athletes. To illustrate this, we discuss the clinical, biomechanical, and ultrasound imaging presentation and the intervention strategies of three volleyball athletes at different stages of their athletic career: youth, middle-aged, and collegiate. We present our examination strategies and interpret the data collected, including visual movement analysis and dynamics, relating these findings to the probable causes of their pain and dysfunction. Using the framework of the EdUReP concept, incorporating Education, Unloading, Reloading, and Prevention, we propose intervention strategies that target each athlete's specific issues in terms of education, rehabilitation, training, and return to sport. This framework can be generalized to manage patellar tendinopathy in other sports requiring jumping, from youth to middle age, and from recreational to elite competitive levels.

Toe Flexor Strength, Flexibility and Function and Flexor Hallucis Longus Tendon Morphology in Dancers and Non-Dancers

Tendinopathy of the flexor hallucis longus (FHL), colloquially referred to as "dancer's tendinitis," is a common condition in dancers and attributed to high demand on this muscle in positions of extreme ankle plantarflexion and metatarsophalangeal (MTP)) flexion and extension. Despite such a high prevalence, there has been little research into preventative or nonsurgical interventions. As a means to identify potential targets for prevention and intervention, this study aimed to characterize toe flexors in dancers by measuring strength, flexibility, function, and FHL tendon morphology. Dancers (n=25) were compared to non-dancers (n=25) in toe flexor isometric strength, first MTP joint range of motion, foot longitudinal arch flexibility, balance ability, endurance during modified heel raises without use of the toes, and FHL tendon thickness, cross-sectional area, and peak spatial frequency. Significant differences were found in functional first MTP joint extension (dancers 101.95°, non-dancers 91.15°, p<0.001), balance ability during single-leg stance on the toes (dancers 11.43 s, non-dancers 5.90 s, p=0.013), and during modified heel raises (dancers 22.20 reps, non-dancers 28.80 reps, p=0.001). Findings indicate that dancers rely on toe flexors more than non-dancers to complete balance and heel raise tasks. Efficacy of using this modified heel raise task with the toes off the edge of a block as a means to train larger plantarflexors and as a nonsurgical intervention should be studied in the future. Improving interventions for FHL tendinopathy will be impactful for dancers, in whom this condition is highly prevalent.

The neuromechanical adaptations to Achilles tendinosis

KEY POINTS

Achilles tendinosis is a localized degenerative musculoskeletal disorder that develops over a long period of time and leads to a compliant human Achilles tendon. We demonstrate that the compliant Achilles tendon elicited a series of adaptations from different levels of the human movement control system, such as the muscle-tendon interaction, CNS control and other muscles in the lower leg. These results illustrate the human body's capacity to adapt to tendon pathology and provide the physiological basis for intervention or prevention strategies. Human movement is initiated, controlled and executed in a hierarchical system including the nervous system, muscle and tendon. If a component in the loop loses its integrity, the entire system has to adapt to that deficiency. Achilles tendon, when degenerated, exhibits lower stiffness. This local mechanical deficit may be compensated for by an alteration of motor commands from the CNS. These modulations in motor commands from the CNS may lead to altered activation of the agonist, synergist and antagonist muscles. The present study aimed to investigate the effect of tendon degeneration on its mechanical properties, the neuromechanical behaviour of the surrounding musculature and the existence of the CNS modulation accompanying tendinosis. We hypothesize that the degenerated tendon will lead to diminished tissue mechanical properties and protective muscle activation patterns, as well as an up-regulated descending drive from the CNS. Strong evidence, as reported in the present study, indicates that tendinotic tendons are more compliant compared to healthy tendons. This unilateral involvement affected the neuromuscular control on the involved side but not the non-involved side. The muscle-tendon unit on the tendinotic side exhibits a lowered temporal efficiency, which leads to altered CNS control. The altered CNS control is then expressed as an adapted muscle activation pattern in the lower leg. Taken together, the findings of the present study illustrate the co-ordinated multi-level adaptations to a mechanical lesion in a tendon caused by pathology.

Exploring Active and Passive Contributors to Turnout in Dancers and Non-Dancers

OBJECTIVE

Lower-extremity external rotation, or turnout, is a fundamental skill in dance. Active standing turnout has previously been measured using low-friction turnout disks. Turnout is influenced by passive range of motion (ROM) and strength, with passive ROM a function of bony morphology and ligamentous/capsular restraints.

PURPOSE

Our study explored the relationship between standing active turnout and femoral bony morphology, hip passive ROM, and strength among dancers and non-dancers.

METHODS

Cross-sectional cohort study. Twenty-three female dancers and 13 female non-dancers aged 18 to 30 yrs were recruited. Standing active turnout on reduced-friction disks, ultrasound images of femoral version, supine passive turnout, and hip abductor and external rotator strength were collected.

RESULTS

Dancers demonstrated greater standing turnout (107° ± 18°) than non-dancers (92° ± 28°), but the difference was not statistically significant (p=0.054). A significant difference was found for femoral version (p<0.001), 4.7° ( ± 2.8°) for dancers vs 12.1° ( ± 4.6°) for non-dancers. Dancers demonstrated greater supine turnout, 102.7°±18.8°, compared to non-dancers, 84.3° ± 30.4° (p=0.031). Dancers were able to achieve greater peak force in turnout compared to non-dancers: 2.44 ± 0.44 N/kg and 1.72 ± 0.59 N/kg, respectively (p<0.0001). Supine total turnout was the best predictor of active turnout, contributing 48% of the variance (r=0.696, p<0.001).

CONCLUSION

Our findings suggest supine turnout is the largest predictor for standing turnout. Investigating dancers and non-dancers independently, our finding were similar to previous studies suggesting the femoro-acetabular complex may be influenced by dance training, contributing to differences in bony morphology between dancers and non-dancers. Although strength did not significantly contribute to active standing turnout, dancers demonstrated greater peak force compared to non-dancers.

GABA system as a target for new drugs

4-Aminobutyric acid is an inhibitory neurotransmitter involved in the control of neuronal activity in the mammalian central nervous system. There is considerable direct and indirect evidence that impaired activity of GABAmediated inhibitory synapses may be an important causative factor in experimental and clinical seizure disorders. This review is focused on the recent development of compounds which can influence GABA neurotransmission by affecting the GABA receptors, the plasma-membrane GABA transporters (GATs) and catabolic enzyme GABA-transaminase (GABAT). These compounds have been primarily investigated in relation to epilepsy, but it has also been found that a decrease in GABA neurotransmission appears to be involved in the aetiology of several neurological disorders such as insomnia, spasticity, neuropathic pain, anxiety and other mental disorders.

Pointing the foot without sickling: an examination of ankle movement during jumping

The sauté is a relatively simple dance jump that can be performed by both highly skilled dancers and non-dancers. However, there are characteristics of jumping unique to trained dancers, especially in terms of foot and ankle movement during flight. Dancers are trained not to "sickle, " or to avoid the anatomically coupled ankle inversion that occurs with plantar flexion, maintaining the appearance of a straight line through the lower leg and foot. The purpose of this study was to examine ankle movements in elite dancers compared to non-dancers. Twenty healthy females, 10 with no prior dance training and 10 professional dancers, performed 20 consecutive sautés while three-dimensional kinematic data were collected. Sagittal and frontal plane kinematics were calculated and vector coding methods were used to quantify coordination patterns within the ankle in the sagittal and frontal planes. This pattern was chosen for analysis to identify the avoidance of a sickled foot by trained dancers. Peak ankle positions and coordination patterns between groups were examined using independent t-tests (a <0.05). Dancers demonstrated greater peak plantar flexion (p<0.01) and less change in ankle angle during the flight phase (p= 0.01), signifying holding the pointed foot position during flight. There was no statistically significant difference in sagittal and frontal plane ankle coupling (p= 0.15); however, the Cohen's d effect size for the difference in coupling was medium-to-large (0.73). Dynamic analysis of the foot and ankle during jumping demonstrates how elite dancers achieve the aesthetic requirements of dance technique.