Reliability of a Barre-Mounted Dynamometer-Stabilizing Device in Measuring Dance-Specific Muscle Performance.

BACKGROUND: Hand-held dynamometry is considered an efficient, effective, and portable means of objectively measuring lower extremity strength; however, it has yet to be studied specific to dance-relevant muscle performance. Also, dynamometry is often criticized for variability in results based on tester strength and sex. Use of an external stabilizing device has been suggested to minimize differences in outcomes between male and female testers by reducing variability associated with tester strength limitations. Therefore, this study used a barre-mounted, portable dynamometer stabilizing device to improve consistency of results among different testers for assessing hip and lower extremity muscle performance in dance-relevant positions. OBJECTIVE: To assess the intra and inter-rater reliability of a barre-mounted dynamometer stabilizing device in measuring muscle performance in common dance maneuvers. METHODS: Two testers assessed muscle performance of three common dance maneuvers--développé en avant, à la secondé, and arabesque--on 11 pre-professional and professional dancers on two separate occasions to establish intra- and inter-rater reliability of the barre-mounted dynamometer stabilizing device. RESULTS: Intra-rater reliability was moderate to high and inter-rater reliability of the device was excellent, with intraclass correlation coefficients ranging from 0.527-0.851 and 0.834-0.953, respectively, for all positions. CONCLUSIONS: The barre-mounted stabilizing device shows promise in mitigating tester strength or fatigue in assessing muscle performance of dancers. Initial assessment of the device suggests further study may be indicated to improve generalizability to applications of larger-scale muscle performance screening and assessment in dancers or other athletic populations who engage in movements that require extensive hip range of motion and multi-joint stability. CLINICAL RELEVANCE: Using a portable, barre-mounted stabilizing device in assessing multi-joint lower extremity muscle performance in dancers improves consistency of testing results. Application of this testing device into wider scale screenings could assist in developing normative data for a population that is lacking.

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.

The feigned annoyance and frustration test to activate the sympathoadrenal medullary system.

When perceived as threatening, social interactions have been shown to trigger the sympathoadrenal medullary system as well as the hypothalamic-pituitary-adrenal axis resulting in a physiologic stress response. The allostatic load placed on human health and physiology in the context of acute and chronic stress can have profound health consequences. The purpose of this study was to develop a protocol for a lab-based stress stimulus using social-evaluative threat. While several valid, stress-stimulating protocols exist, we sought to develop one that triggered a physiologic response, did not require significant lab resources, and could be completed in around 10 min. We included 53 participants (29 men and 24 women) and exposed them to a modified version of the Stroop Color-Word Interference Task during which the participants were made to feel they were performing the task poorly while the lead researcher feigned annoyance and frustration. After exposure to this Feigned Annoyance and Frustration (FAF) Test, both the men and women in this study demonstrated a statistically significant and clinically meaningful increase in subjective stress on the visual analog scale. Additionally, the men in this study demonstrated a statistically significant increase in heart rate and salivary α-amylase concentrations after exposure to the test. The women in this study did not demonstrate a statistically significant increase in the physiologic stress biomarkers. This protocol for the FAF Test shows promise to researchers with limited time and resources who are interested in experimentally activating the sympathoadrenal medullary system.

Individuals With Recurrent Low Back Pain Exhibit Significant Changes in Paraspinal Muscle Strength After Intramuscular Fine Wire Electrode Insertion.

OBJECTIVE: To examine how insertion and presence of intramuscular fine-wire electromyography electrodes (IFWEs) in lumbar multifidus affect paraspinal muscle strength, endurance, and activation in persons with and without recurrent lower back pain (RLBP) during activities that require high levels of muscle contraction. DESIGN: Case-control with randomization of conditions. SETTING: Clinical research laboratory. PARTICIPANTS: Forty participants age 18 to 40 years were recruited (18 female; mean age = 25.5 years); 20 with a history of RLBP were compared to a matching control group of 20 without RLBP. INTERVENTIONS: Each participant was tested under three conditions over three sessions. On Session 1, the baseline condition, we assessed muscle performance without IFWE insertion. On Sessions 2 and 3, participants were randomly alternated between two experimental conditions: (1) wire-in, in which the IFWE was inserted and remained within the muscle during testing; and (2) wire-out, in which the IFWE was inserted and immediately removed. MAIN OUTCOME MEASUREMENTS: Lumbar spinal extensor peak strength, endurance, and normalized electromyography (EMG) amplitude during the endurance test. RESULTS: Individuals with RLBP showed a significant decrease in peak strength during conditions that involved IFWE insertion and tend to experience more pain during muscle testing. Both groups exhibited similar levels of performance and muscle activation during the endurance test. CONCLUSION: Our findings indicate that individuals with RLBP exhibited reduced lumbar extensor strength in response to IFWE insertion to the deep paraspinal muscles. This behavior is different from those without RLBP. Researchers should carefully consider the use of IFWE in individuals with RLBP during high exertion activities.