Hsin-Yi Kathy Cheng

Finite element analysis of plantar fascia under stretch—The relative contribution of windlass mechanism and Achilles tendon force

Stretching plays an important role in the treatment of plantar fasciitis. Information on the internal stresses/strains of the plantar fascia under stretch is useful in enhancing knowledge on the stretch mechanisms. Although direct measurement can monitor plantar fascia changes, it is invasive and gathers only localized information. The purpose of this paper was to construct a three-dimensional finite element model of the foot to calculate the stretch effects on plantar fascia and monitor its stress/strain distributions and concentrations. A three-dimensional foot model was developed and contained 26 bones with joint cartilages, 67 ligaments and a fan-like solid plantar fascia modeling. All tissues were idealized as linear elastic, homogeneous and isotropic whilst the plantar fascia was assigned as hyperelastic to represent its nonlinearity. The plantar fascia was monitored for its biomechanical responses under various stretch combinations: three toe dorsiflexion angles (windlass effect: 15 degrees , 30 degrees and 45 degrees ) and five Achilles tendon forces (100, 200, 300, 400 and 500N). Our results indicated that the plantar fascia strain increased as the dorsiflexion angles increased, and this phenomenon was enhanced by increasing Achilles tendon force. A stress concentration was found near the medial calcaneal tubercle, and the fascia stress was higher underneath the first foot ray and gradually decreased as it moved toward the fifth ray. The current model recreated the position of the foot when stretch is placed on the plantar fascia. The results provided a general insight into the mechanical and biomechanical aspects of the influences of windlass mechanism and Achilles tendon force on plantar fascia stress and strain distribution. These findings might have practical implications onto plantar fascia stretch approaches, and provide guidelines to its surgical release.

Effects of active fatiguing movement versus passive repetitive movement on knee proprioception

BACKGROUND Proprioception can be affected by many factors such as age, gender, injury, disease, exercise, and fatigue. To date, the mechanisms or pathways by which fatigue influences proprioception have not been elucidated. Generally, it is accepted that local muscular effects occurred during fatigue state may negatively affect proprioception. Research has indicated that metabolic acidosis resulting from active muscle activities, along with tissue stretching and joint laxity resulting from repetitive joint movements, are likely related to proprioceptive deterioration. So far, little direct evidence or research supports these statements. The purpose of this study was to examine the effects of fatigue exercises (repetitive active movement) and repetitive passive movements on knee proprioception. METHODS A quasi-experimental design with repeated measure on proprioception following two forms of knee joint movement (repetitive active/passive movement in 120 degrees /s with 60 repetitions over a 10 degrees -100 degrees range) was conducted. Fifteen healthy volunteers underwent two forms of movement intervention in two consecutive days in a counter-balanced manner. Knee joint repositioning errors were measured before and after the movement intervention. FINDINGS Study results showed a statistically significant increase in absolute repositioning error following repetitive active movement, but a decrease following repetitive passive movement intervention. INTERPRETATION This study concluded that a repetitive passive movement protocol was capable of improving knee joint position sense. Meanwhile, the negative effect from the muscle receptors following the repetitive active movement overwhelmed the positive effect from the repetitive passive movement intervention. It supports the clinical utilization of repetitive passive movement to promote proprioception. This utilization can be implemented for proprioceptive training in sports activities, plus injury prevention and rehabilitation.

Muscle strength enhancement following home-based virtual cycling training in ambulatory children with cerebral palsy

This study is the first well-designed randomized controlled trial to assess the effects of a novel home-based virtual cycling training (hVCT) program for improving muscle strength in children with spastic cerebral palsy (CP). Twenty-eight ambulatory children with spastic CP aged 6-12 years were randomly assigned to an hVCT group (n=13) or a control group (n=15). Outcome measures, including gross motor function of the Bruininks-Oseretsky Test of Motor Proficiency (BOTMP) and muscle strength (isokinetic torque of knee extensor and flexor muscle), were administered before and immediately after the 12-week intervention. Analysis of covariance (ANCOVA) at post-treatment showed that, compared to the control group, the hVCT group had significantly higher isokinetic torque in the knee extensor and flexor muscles at 60°/s and 120°/s angular velocities (p<0.05). At post-treatment, the hVCT group also showed greater isokinetic strength improvement in the knee flexor than in the knee extensor at 60°/s (knee flexor: 41%; knee extensor: 19%) and at 120°/s (knee flexor: 36%; knee extensor: 30%). However, the BOTMP scores at post-treatment did not differ between the two groups. Although the proposed 12-week hVCT protocol does not improve gross motor function, it enhances knee muscle strength in children with CP. The protocol obtains larger gains in the knee flexor than in the knee extensor at different angular velocities. The study findings will help clinicians to provide more effective and efficient strategies for muscle strength training in children with CP.

Rapid repetitive passive movement improves knee proprioception

BACKGROUND Proprioception can be affected by many factors including exercise. Most exercises involve certain degrees of repeated passive movements, and different velocities of these movements might affect proprioception differently. The purpose of this study was to evaluate the influences of different angular velocities of repeated passive movement on knee proprioception via active repositioning and kinesthesia measurement. METHODS A quasi-experimental design with repeated measure on movement velocity (0°/s, 2°/s, 90°/s, and 150°/s). Sixteen healthy young adults participated in the study. All of them received 30 times repeated passive knee movement intervention in four different knee angular velocities - 0°/s, 2°/s, 90°/s, and 150°/s - with counter-balanced sequence in four successive days. Knee active repositioning and kinesthesia were measured with error scores before and after the intervention. FINDINGS The results revealed a decrease in error scores in both active repositioning and kinesthesia measurement with the velocities of 90°/s and 150°/s (p<0.05); however no significant change was seen with the static condition (0°/s ) or with the velocity of 2°/s. INTERPRETATION We concluded that repeated passive movement with rapid angular velocities was capable of improving knee proprioception, specifically in active repositioning and kinesthesia measurements. These results would provide information on the effects of different movement velocities onto knee proprioception. Along with further investigations, the findings could potentially enhance our knowledge on knee injury prevention, treatment, and rehabilitation.

Effects of whole body vibration on spasticity and lower extremity function in children with cerebral palsy.

AIM The aim of this study was to evaluate the effect of whole body vibration (WBV) on lower extremity spasticity and ambulatory function in children with cerebral palsy (CP) with a complete crossover design. METHOD Sixteen participants aged 9.8(2.3) years received a 20-min WBV and a control condition in a counterbalanced order on two separate days. Change scores of each outcome variable were used to show the improvement. RESULTS Repeated-measures analyses revealed significant differences in condition scores among variables including active range-of-motion (active ROM, increased), relaxation index (RI, increased), Modified Ashworth Scale (MAS, decreased), timed up-and-go (TUG, decreased), and Six Minute Walk Test (6MWT, increased). Significant differences were also found in time change scores for MAS and 6MWT. Correlation results revealed that TUG was significantly correlated with RI (r=-.512, p=.042), and 6MWT (r=-.700, p=.003). INTERPRETATION This study suggested that WBV intervention can control the spasticity, enhance ambulatory performance and increase active ROM. Along with previous results, data from this study revealed the potential use of WBV in clinical rehabilitation in children with CP. Future investigations should focus on finding the combination of treatment frequency and duration to achieve an ideal result.

Altered Co-contraction of Cervical Muscles in Young Adults with Chronic Neck Pain during Voluntary Neck Motions.

[Purpose] Muscle co-contraction is important in stabilizing the spine. The aim of this study was to compare cervical muscle co-contraction in adults with and without chronic neck pain during voluntary movements. [Subjects and Methods] Surface electromyography of three paired cervical muscles was measured in fifteen young healthy subjects and fifteen patients with chronic neck pain. The subjects performed voluntary neck movements in the sagittal and coronal plane at slow speed. The co-contraction ratio was defined as the normalized integration of the antagonistic electromyography activities divided by that of the total muscle activities. [Results] The results showed that the co-contraction ratio of patients was greater during flexion movement, lesser during extension movement, slightly greater during right lateral bending, and slightly lesser during left lateral bending compared with in the controls. [Conclusion] The results suggested that neck pain patients exhibit greater antagonistic muscle activity during flexion and dominate-side bending movements to augment spinal stability, while neuromuscular control provides relatively less protection in the opposite movements. This study helps to specify the changes of the stiffness of the cervical spine in neck pain patients and provides a useful tool and references for clinical assessment of neck disorders.

Long-term effects of therapeutic exercise on nonspecific chronic neck pain: a literature review

[Purpose] Nonspecific neck pain is a common musculoskeletal disease. Therapeutic exercise has been shown to improve pain and disability in short-term and midterm follow-ups. This study performed a literature review of the long-term effects of therapeutic exercise on subjects with nonspecific chronic neck pain. [Subjects and Methods] The databases of the CINAHL, MEDLINE, PEDro and PubMed were used. Randomized controlled trials (RCT) published from January 2000 to January 2014 and explicitly including a one-year follow-up were identified. [Results] Only six articles were included in this review. They had scores of 5 to 8 points on the PEDro scale, and the level of evidence was grade I. The study results show that the main exercises used were cervical strengthening and endurance training exercise. Short-term exercises (10 to 12 weeks) helped to improve the body function, structure, activity and participation immediately after the intervention, but not at the long-term follow-up. On the other hand, long-term interventions (1 year) resulted in improvements in body function and structure at the 3 year follow-up. [Conclusion] The results of the six high-quality studies suggest that long-term exercise have long-term benefits for patients with nonspecific neck pain in terms of body function and structure.

Nonlinear Finite Element Analysis of the Plantar Fascia due to the Windlass Mechanism

Background: Tightening of plantar fascia by passively dorsiflexing the toes during walking has functional importance. The purpose of this research was to evaluate the influence of big toe dorsiflexion angles upon plantar fascia tension (the windlass effect) with a nonlinear finite element approach. Materials and Methods: A two-dimensional finite element model of the first ray was constructed for biomechanical analysis. In order to imitate the windlass effect and to evaluate the mechanical responses of the plantar fascia under various conditions, 12 model simulations - three dorsiflexion angles of the big toe (45 degrees, 30 degrees, and 15 degrees), two plantar fascia properties (linear, nonlinear), and two weightbearing conditions (with body weight, without body weight) - were designed and analyzed. Results: Our results demonstrated that nonlinear modeling of the plantar fascia provides a more sophisticated representation of experimental data than the linear one. Nonlinear plantar fascia setting also predicted a higher stress distribution along the fiber directions especially with larger toe dorsiflexion angles (45 degrees > 30 degrees > 15 degrees). The plantar fascia stress was found higher near the metatarsal insertion and faded as it moved toward the calcaneal insertion. Conclusion: Passively dorsiflexing the big toe imposes tension onto the plantar fascia. Windlass mechanism also occurs during stance phase of walking while the toes begin to dorsiflex. From a biomechanical standpoint, the plantar fascia tension may help propel the body upon its release at the point of push off. Clinical Relevance: A controlled stretch via dorsiflexing the big toe may have a positive effect on treating plantar fasciitis by providing proper guidance for collagen regeneration. The windlass mechanism is also active during the stance phase of walking when the toes begin to dorsiflex.

Work-related musculoskeletal disorders and ergonomic risk factors in early intervention educators.

BACKGROUND Early intervention educators who serve children with special needs often suffer from physical strains. The objectives of this study were to investigate the prevalence of work-related musculoskeletal disorders in this population, and to evaluate the relationship between work-related musculoskeletal disorders and personal/ergonomic risk factors. METHODS A self-designed questionnaire consisting three domains (demographics/prevalence of work-related musculoskeletal disorders/ergonomic risk factors) was delivered to educators who work in early intervention institutions. RESULTS Ninety-four percent of early intervention educators suffered from musculoskeletal disorders. Logistic regression revealed that some work-related ergonomic factors were highly associated with symptoms on lower back, shoulder and neck, with odds ratios ranging from 0.321 to 4.256. CONCLUSION High prevalence of work-related musculoskeletal disorders impacts this occupation negatively. Further regulations to the institutions regarding workplace health promotion and environment modification, as well as training to the employees for body mechanics, should be implemented to prevent injury occurrence.

Effects of an eight-week whole body vibration on lower extremity muscle tone and function in children with cerebral palsy

The aim of this study was to evaluate the effect of an eight-week whole body vibration (WBV) on lower extremity spasticity and ambulatory function in children with cerebral palsy with a complete crossover design. Sixteen participants aged 9.2 (2.1) years participated in this study. Half of the participants received a 10-min WBV, 3 times a week for 8 weeks. Then a 4-week washout period followed, after which they received a sham WBV 3 times a week for 8 weeks. The other half received the intervention in a reversed order. The participants were evaluated via variables measuring range-of-motion, muscle tone, and ambulatory function before, immediately after, 1 day after, and 3 days after each intervention. Repeated-measures analyses revealed significant beneficial effects on most variables expect the passive range-of-motion measurement. Significant correlations were found between timed up-and-go and relaxation index, and between timed up-and-go and six-minute walk test. The results suggested that an 8-week WBV intervention normalized muscle tone, improved active joint range and enhanced ambulatory performance in children with cerebral palsy for at least 3 days. These indicated that regular WBV can serve as an alternative, safe, and efficient treatment for these children in both clinical and home settings.