Search

The ankle is an important joint to understand in the context of dance because it is the connection between the leg and the foot that establishes lower extremity stability. Its function coordinates with the leg and foot and, thus, it is crucial to the dancer's ability to perform. Furthermore, the ankle is one of the most commonly injured body regions in dance. An understanding of ankle anatomy and biomechanics is not only important for healthcare providers working with dancers, but for dance scientists, dance instructors, and dancers themselves. The bony architecture, the soft tissue restraints, and the locomotive structures all integrate to allow the athletic artistry of dance. Yet, there is still much research to be carried out in order to more completely understand the ankle of the dancer. [ABSTRACT FROM AUTHOR]

Background: Gastrocnemius medialis (GM) and lateralis (GL) act at the ankle complex in the sagittal and frontal planes and there is evidence that their actions can be somewhat uncoupled from each other. Some independence of GM and GL from each other could be advantageous, e.g. to stabilise the ankle complex in unstable walking conditions. Given the compartmentalised structure of the Achilles tendon, the sub-tendons of GM and GL may exhibit different elongation during plantarflexion contractions, particularly with the foot in different frontal plane positions., Research Questions: METHODS: Sub-tendon elongation was determined from 18 participants during ramped isometric plantarflexion contractions to 70% of their maximum voluntary contraction (MVC) level with the foot in neutral, inversion and eversion. One-dimensional statistical parametric mapping was applied to determine elongation differences., Results: Elongation within a sub-tendon did not differ in the three foot positions. Elongation was similar between both sub-tendons at very low contraction levels, but GM sub-tendon elongation exceeded GL sub-tendon displacement significantly from 30% MVC. The elongation differences between the sub-tendons were not affected by foot position., Significance: Greater GM sub-tendon elongation is likely caused by the greater force production capability of GM but may also indicate that the sub-tendons of GM and GL have different mechanical properties, which is currently unknown. Elongation differences were contraction level dependent suggesting that contributions of GM and GL to plantarflexion torque may also be contraction level dependent., (Crown Copyright © 2019. Published by Elsevier B.V. All rights reserved.)

The triceps surae primarily acts as plantarflexor of the ankle joint. However, the group also causes inversion and eversion at the subtalar joint. Despite this, the Achilles tendon moment arm is generally measured without considering the potential influence of inversion/eversion of the foot during plantarflexion. This study investigated the effect of foot inversion and eversion on the plantarflexion Achilles tendon moment arm. Achilles tendon moment arms were determined using the centre-of-rotation method in magnetic resonance images of the left ankle of 11 participants. The foot was positioned at 15° dorsiflexion, 0° or 15° plantarflexion using a Styrofoam wedge. In each of these positions, the foot was either 10° inverted, neutral or 10° everted using an additional Styrofoam wedge. Achilles tendon moment arm in neutral foot position was 47.93 ± 4.54 mm and did not differ significantly when the foot was positioned in 10° inversion and 10° eversion. Hence, inversion/eversion position of the foot may not considerably affect the length of the Achilles tendon moment arm. This information could be useful in musculoskeletal models of the human lower leg and foot and when estimating Achilles tendon forces during plantarflexion with the foot positioned in inversion or eversion., Competing Interests: We declare we have no competing interests.

Objectives: This study set out to determine whether two potential protein-sparing modulators (eicosapentaenoic acid and vitamin D) would modulate the anticipated muscle functional and related blood vessels function deleterious effects of immobilisation., Design: The study used a randomised, double-blind, placebo-controlled design., Setting: The study took part in a laboratory setting., Participants: Twenty-four male and female healthy participants, aged 23.0±5.8 years., Intervention: The non-dominant arm was immobilised in a sling for a period of nine waking hours a day over two continuous weeks. Participants were randomly assigned to one of three groups: placebo (n=8, Lecithin, 2400 mg daily), omega-3 (ω-3) fatty acids (n=8, eicosapentaenoic acid (EPA); 1770 mg, and docosahexaenoic acid (DHA); 390 mg, daily) or vitamin D (n=8, 1,000 IU daily)., Measurements: Isometric and isokinetic torque, antagonist muscle co-contraction (activation profile), muscle fatigability indices, and arterial resting blood flow were measured before, at the end of the immobilisation period, and two weeks after re-mobilisation., Results: Muscle elbow flexion and extension isometric and isokinetic torque decreased significantly with limb immobilisation in the placebo group (P<0.05). Despite no significant effect of supplementation, ω-3 and vitamin D supplementation showed trends (P>0.05) towards attenuating the decreases observed in the placebo group. There was no significant change in muscle fatigue parameters or co-contraction values with immobilisation and no effect of supplementation group (P>0.05). Similarly, this immobilisation model had no impact on the assessed blood flow characteristics. All parameters had returned to baseline values at the re-mobilisation phase of the study., Conclusion: Overall, at the current doses, neither ω-3 nor vitamin D supplementation significantly attenuated declines in torque associated with immobilisation. It would appear that muscle function (described here in Part B) might not be as useful a marker of the effectiveness of a supplement against the impact of immobilisation compared to tissue composition changes (described in Part A).

Objectives: Muscle size decreases in response to short-term limb immobilisation. This study set out to determine whether two potential protein-sparing modulators (eicosapentaenoic acid and vitamin D) would attenuate immobilisation-induced changes in muscle characteristics., Design: The study used a randomised, double-blind, placebo-controlled design., Setting: The study took part in a laboratory setting., Participants: Twenty-four male and female healthy participants, aged 23.0±5.8 years., Intervention: The non-dominant arm was immobilised in a sling for a period of nine waking hours a day over two continuous weeks. Participants were randomly assigned to one of three groups: placebo (n=8, Lecithin, 2400 mg daily), omega-3 (ω-3) fatty acids (n=8, eicosapentaenoic acid (EPA); 1770 mg, and docosahexaenoic acid (DHA); 390 mg, daily) or vitamin D (n=8, 1,000 IU daily)., Measurements: Muscle and sub-cutaneous adipose thickness (B-mode ultrasonography), body composition (DXA) and arm girth (anthropometry) were measured before immobilisation, immediately on removal of the sling and two weeks after re-mobilisation., Results: Muscle thickness (-5.4±4.3%), upper and lower arm girth (-1.3±0.4 and -0.8±0.8%, respectively), lean mass (-3.6±3.7%) and bone mineral content (BMC) (-2.3±1.5%) decreased significantly with limb immobilisation in the placebo group (P<0.05). Despite no significant effect of group, ω-3 and vitamin D supplementation showed trends (p>0.05) towards attenuating the decreases in muscle thickness, upper/lower arm girths and BMC observed in the placebo group. The ω-3 supplementation group demonstrated a non-significant attenuation of the decrease in DXA quantified lean mass observed in the placebo group. Sub-cutaneous adipose thickness increased in the placebo group (P<0.05). ω-3 and vitamin D both blunted this response, with ω-3 having a greater effect (P<0.05). All parameters had returned to baseline values at the re-mobilisation phase of the study., Conclusion: Overall, at the current doses, ω-3 and vitamin D supplementation only attenuated one of the changes associated with non-injurious limb immobilisation. These findings would necessitate further research into either a) supplementation linked to injury-induced immobilisation, or b) larger doses of these supplements to confirm/refute the physiological reserve potential of the two supplements.

Background: Kinematic observations are inconsistent in predicting lower-extremity injury risk, and research suggests that kinetic variables may be more important in this regard. Before kinetics can be prospectively investigated, we need reliable ways of measuring them clinically. A measurement instrument was manufactured that closely mirrors a manual test used to clinically estimate supination resistance force. The reliability of the instrument and the validity of the clinical test were investigated., Methods: The left feet of 26 healthy individuals (17 men and 9 women; mean ± SD age, 25.9 ± 9.2 years; mean ± SD weight, 77.7 ± 13.3 kg) were assessed. Foot Posture Index (FPI-6), manual supination resistance, and machine supination resistance were measured. Intrarater and interrater reliability of all of the measurements were calculated. Correlations of the supination resistance measured by the device with FPI-6, the manual supination resistance test, and body weight were investigated., Results: Interrater reliability of all of the measurements was generally poor. The supination resistance machine correlated highly with the manual supination test for the rater experienced with its use. Supination resistance measurements correlated poorly with the FPI-6 and weakly with body weight., Conclusions: The supination resistance machine was shown to have sufficient limits of agreement for the study, but improvements need to be made for more meaningful research going forward. In this study, the force required to supinate a foot was independent of its posture, and approximately 12% of it was explained by body weight. Further work is required with a much larger sample size to build regression models that sufficiently predict supination resistance force and that will be of clinical use. The manual supination test is a valid clinical test for clinicians experienced in its use.

Background: Stature loss is a commonly used measure of spinal load. The aim of this study was to investigate the pattern of diurnal stature change in those with and without chronic low-back pain, over a 24-h period., Methods: Eight participants with chronic low-back pain (age 24.6 (SD 4.3) years, height 1.76 (SD 0.08) m, body mass 72.8 (SD 11.1) kg) and eight controls (age 21.8 (SD 2.0) years, height 1.75 (SD 0.10) m, body mass 71.8 (SD 11.6) kg) participated in this investigation. Twenty-four stature measurements were performed over a 24-h period., Findings: The trough to peak variation in stature of 17.9 mm (low-back pain group) and 17.6mm (control group) did not differ between groups (P>0.05). Both groups experienced greatest stature change in the 1st hour after rising (31.3% [low-back pain] and 44.6% [control] of total stature change). At approximately 18:00h the LBP group reached a plateau whilst the control group continued to lose stature. Between 14:00 and 18:00h both groups demonstrated a previously unreported recovery of stature. A significant correlation was found between low-back discomfort and stature change in the low-back pain group only., Interpretation: No significant difference existed between groups in relation to total stature loss; however the low-back pain group appeared to reach their nadir earlier, possibly exposing other spinal structures to loading for a greater duration. This is supported by the relationship found between stature loss and discomfort. The reversal in stature loss in the afternoon may be of clinical significance and warrants further investigation., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Dance is a high performance athletic activity that leads to great numbers of injuries, particularly in the ankle region. One reason for this is the extreme range of ankle motion required of dancers, especially females in classical ballet where the en pointe and demi-pointe positions are common. These positions of maximal plantar flexion produce excessive force on the posterior ankle and may result in impingement, pain, and disability. Os trigonum and protruding lateral talar process are two common and well-documented morphological variations associated with posterior ankle impingement in ballet dancers. Other less well-known conditions, of both bony and soft tissue origins, can also elicit symptoms. This article reviews the anatomical causes of posterior ankle impingement that commonly affect ballet dancers with a view to equipping healthcare professionals for improved effectiveness in diagnosing and treating this pathology in a unique type of athlete.

Aim: Loss of muscle strength and balance are main characteristics of physical frailty in old age. Postural sway is associated with muscle contractile capacity and to the ability of rapidly correcting ankle joint changes. Thus, resistance training would be expected to improve not only strength but also postural balance., Methods: In this study, age-matched older individuals (69.9+/-1.3 years) were randomly assigned to flywheel (n=12), or weight-lifting (n=12) groups, training the knee extensors thrice weekly for 12 weeks. The hypotheses were that owing to a larger eccentric loading of the knee extensors, flywheel training would result in (a) greater gains in quadriceps strength; (b) greater improvements in balance performance compared with weight-lifting training. Isokinetic dynamometry, B-mode ultrasonography, electromyography, percutaneous muscle stimulation and magnetic resonance imaging were employed to acquire the parameters of interest., Results: Following training, knee extensors peak isokinetic power increased by 28% (P<0.01) in the flywheel group with no change in the weight-lifting group. Adaptations of the gastrocnemius muscle also occurred in both groups. The gastrocnemius characteristic with the highest response to training was tendon stiffness, with increases of 54% and 136% in the weight-lifting and flywheel groups, respectively (P<0.01). The larger increase in tendon stiffness in the flywheel group was associated with an improvement in postural balance (P<0.01)., Conclusion: Quadriceps flywheel loading not only produces a greater increase in power than weight training but its physiological benefits also transfer/overspill to the plantarflexor muscle-tendon unit resulting in a significantly improved balance. These findings support our initial hypotheses.

Background: Stature reductions in asymptomatic individuals, caused by a set load, are lower later in the day when stature is in the trough of diurnal variation; hence most stature reduction investigations are conducted in the morning. Recent evidence suggests that it is not the reductions in stature, but the recovery of stature, that is of greatest importance. The aim of this investigation was to establish whether stature recovery is also affected by time of day and to determine if any differences exist between a chronic low back pain and asymptomatic group., Methods: Eleven chronic low back pain participants (age=32.8 SD 7.9 yrs, mass=74.4 SD 14.2 kg and height=1.73 SD 0.07 m) and 11 asymptomatic participants (age=31.0 SD 6.3 yrs, body mass=72.6 SD 11.5 kg and height=1.76 SD 0.09 m) underwent two 20 min loaded walking tasks (10% body mass), one in the morning (09:00) and one in the afternoon (14:00), followed by a 20 min unloaded recovery period. Measurements of stature were obtained throughout., Findings: The asymptomatic group experienced significantly less stature reduction (P=0.05; ES=1.1) and greater stature recovery (P=0.02; ES=0.9) in the afternoon compared to the morning. The chronic low back pain group experienced a similar pattern to the asymptomatic group, however no significant difference between sessions for changes in stature was evident P=0.07., Interpretation: Further investigations of stature recovery should be restricted to the morning when comparing individuals with and without chronic low back pain, as time of day appeared to have effect on stature recovery, particularly in the asymptomatic group. Time dependent differences in stature change between these two populations warrants further investigation.

Objective: To determine whether changes in stature recovery could be exhibited in an asymptomatic group through the use of functional electric stimulation (FES)., Design: A repeated-measures cohort study considering the effects of FES on stature recovery after a loaded walking task in a group of asymptomatic subjects. Each participant performed the 20-minute loaded walking task (at 10% of body mass) on 2 separate occasions followed by a 20-minute recovery period, once with FES and once without. Measurements of stature using a stadiometer were recorded throughout., Setting: A university laboratory., Participants: Eight asymptomatic male volunteers (age, 29.0+/-5.1y; mass, 80.7+/-8.4kg; height, 1.81+/-0.06m) with no history of chronic low back pain (LBP) were recruited through notices in the university and local communities., Interventions: Not applicable., Main Outcome Measures: Recovery of stature was assessed via stadiometry during the postexercise unloading periods., Results: Each participant experienced significantly better stature recovery (percentage of stature reduction) during the control session compared with the FES session, with mean stature recoveries of 104.6%+/-22.9% and 56.3%+/-27.4%, respectively (P=.01)., Conclusions: Use of FES correlated with significant reductions in stature recovery. Elevating paraspinal muscle activity may increase compression on the intervertebral disks and therefore diminish the ability to recover the reduction in height caused by the loaded walking task. This investigation offers further support to the theory that the raised paraspinal muscle activity exhibited by persons with chronic LBP leads to reduced stature recovery.

Measurements of reduction in stature have been used to compare spinal loading in chronic low-back pain (CLBP) and asymptomatic populations. Whether there are any differences in the repeatability of stature measurements, between those with and without CLBP, is not known. This investigation aimed to determine the repeatability of stature measurements in those with (n = 12) and without (n = 12) CLBP, and to establish if the ability to produce repeatable measurements is retained after a specific timeframe. Stature measurements were taken on two separate sessions that were 2 weeks apart, using a stadiometer accurate to 0.01 mm. All participants attained a mean SD of < or = 0.5 mm by the third measurement set taken on the first session of testing and no significant difference in mean SD was found between those with (0.37 mm) and without (0.40 mm) CLBP (p > 0.05). Intraclass correlation coefficients (ICC) demonstrated good levels of repeatability for all stature measurements obtained from the participants and the values for Standard error of the measurement (SEM) improved as the mean SD decreased with each measurement set. Investigators should have confidence in the ability of those with and without CLBP to produce equally repeatable stature measurements with appropriate prior practice. The second session of testing demonstrated that both groups had retained the ability to achieve the desired level of repeatability (SD < or = 0.5 mm) 2 weeks later without further practice.

Objective: To determine whether stature recovery and paraspinal muscle activity can be altered in individuals with and without chronic low-back pain by assuming different unloading positions., Design: A case-control study considering the effects of unloading position on stature recovery in individuals with and without chronic low-back pain., Background: Stature recovery has been documented to be lower in individuals with chronic low-back pain. Elevated paraspinal muscle activity subjects the spine to increased compression, which may delay stature recovery. However, the mechanism(s) causing prolonged stature recovery are yet to be explored., Methods: Eleven chronic low-back pain participants (age 33 yr (SD 12.2), height 1.72 m (SD 0.08), body mass 75.9 kg (SD 10.7)) and eleven asymptomatic participants (age 30.5 yr (SD 9.7), height 1.75 m (SD 0.10), body mass 73.3 kg (SD 11.7)) performed a loaded walking task (10% body mass) and adopted four unloading positions on separate occasions. Measurements of stature and muscle activity were recorded during each position., Findings: Individuals with chronic low-back pain exhibited higher paraspinal EMG and delayed stature recovery in all positions (P<0.05). Both groups experienced greatest stature recovery and least muscle activity during gravity inversion (P<0.05)., Interpretation: Elevated muscle activity was found in the chronic low-back pain group supporting the existence of this explanation for delayed stature recovery. The gravity inverted position resulted in the lowest EMG and the greatest stature recovery. Further research is required to determine whether improving stature recovery has clinical implications by reducing pain/disability.

Objectives: To further the understanding of stature recovery in subjects with and without chronic low back pain (CLBP) and to determine the relations among stature recovery, paraspinal muscle activity, and perceived pain and disability., Design: A case-control study in which stature loss and recovery were assessed in subjects with and without CLBP after a 20-minute loaded walking task (10% of body mass). Group differences in pain, disability, and paraspinal muscle activity were also assessed., Setting: A university laboratory., Participants: Twenty subjects with CLBP were matched (age, sex, body mass, physical activity level) with 20 controls who were recruited through notices in the university, general community, and local Primary Care Trust., Interventions: Not applicable., Main Outcome Measures: Stature changes and integrated electromyograms of the paraspinal muscles during a loading and unloading period were assessed., Results: Stature changes after loading did not differ between groups ( P <.05). Subjects with CLBP recovered significantly less stature during unloading than did the controls ( P <.05). Paraspinal muscle activity correlated negatively with stature recovery ( P <.05). Relations among stature recovery, pain, and disability were shown ( P <.05)., Conclusions: The elevated paraspinal muscle activity exhibited by the CLBP group increased compression on the intervertebral disks and diminished their ability to recover the height lost through loaded exercise. Further research is required to establish whether a change in paraspinal muscle activity is associated with corresponding changes in stature recovery, and if this has any clinical implications by reducing pain and disability.

The majority of time lost from work as a result of absenteeism is classified as due to sickness although only a small proportion of the total can be regarded as a result of unfitness for work for medical reasons. An occupational health service assists a business in minimizing absenteeism by promoting an early return to work, assists general practitioners and hospital specialists in tailoring return to work packages, and assists employees by liaising with both management and their medical specialists to facilitate a return to normal work.