The study aimed to determine which of the five classical ballet positions is the most demanding regarding muscular activity, values of external rotation in the hip joints, angular values of foot progression as well as the inclination (tilt) of the pelvis in the sagittal plane. Methods: In this cross-sectional study, 14 female pre-professional ballet dancers (aged 11–16) participated. Participants were tasked with the sequential adoption of five classical ballet positions (CP1–CP5). The electromyographic activity of the muscles of the trunk and the lower limb was recorded with surface electrodes. Kinematic data including hip and knee external rotation, foot progression angle and pelvic tilt were collected using a motion capture system. Results: Symmetric positions CP1 and CP2 were not as demanding as asymmetric CP3–CP5. Higher values of hip and foot external rotation without greater muscular effort in CP2 than CP1 was noticed. Considering asymmetric positions, CP3 did not trigger a greater activity of hip or foot muscular groups than CP4 and CP5. CP4 was characterised by the greatest pelvic anterior tilt and the lowest activity of GM in the forward lower limb. In CP5, forward lower limb entailed a higher activity of muscles supporting the foot than in the remaining positions. Conclusion: In terms of biomechanics, the most demanding classical ballet position in pre-professional dancers is CP4, followed by CP5, CP3, CP1 and CP2. This finding can be applied in educational methodology of dancers, figure skaters, synchronized swimmers, acrobatic gymnasts, rhythmic gymnasts or cheerleaders.
Purpose: Chronic low back pain is a common disorder affecting about 80% of the population, caused by a disorder in the muscular system. The main aim of this study was to assess muscle fatigue during the Biering–Sorensen Test in people with chronic low back pain who underwent the McKenzie treatment. Methods: Tests were conducted on 19 men (mean age of 41.4 years) with chronic non-specific lumbar-sacral pain syndrome, working in the seated position in front of a computer. Assessment of changes in fatigue of erector spinae, gluteus maximus and biceps femoris using surface electromyography during the Biering–Sorensen Test and subjective pain assessment using Visual Analog Scale were conducted on three test dates. Time-frequency representation of the electromyographic signal (Fourier transform) was used for the examination of muscle fatigue. The McKenzie method of diagnosis and therapy was applied before and between the tests. Results: The McKenzie therapy resulted in increased endurance (test duration) of the examined spinal muscles between the 1st and 3rd test date (p = 0.043), and a systematic decrease in pain assessment on the three test dates (p = 0.000–0.004). Correlations were obtained between slope coefficients of the simple regression of median frequency of electromyographic signals on the one hand and duration of the BST (p = 0.000–0.012) and anthropometric parameters (body mass, height and body mass index, p = 0.001–0.020) on the other. Conclusions: The McKenzie method is an effective tool in reducing the level of lumbar pain and improving muscle endurance.
The main purpose was to determine the values of spatio-temporal parameters and ground reaction forces during the swingthrough crutch gait. Methods: Eighteen male patients with unilateral injury within the foot, ankle or shank (age: 25.4 ± 7.7 years, body height: 1.79 ± 0.06 m, body mass: 76.1 ± 11.5 kg) participated in the study. In the experiment, 6-camera optoelectronic motion capture system and force platform were used. The measurements of spatio-temporal parameters and ground reaction force (GRF) were performed for uninjured lower extremity (ULE), crutch on the ULE side (CrU) and crutch on the injured lower extremity side (CrI). Results: Analysis demonstrated a significantly longer stance phase and a significantly shorter swing phase for ULE than crutches ( p < 0.05), and a significantly longer first, compared to the second, double support phase ( p < 0.05). Comparisons showed also significantly higher maximum values of the vertical GRF and extreme values of the horizontal antero-posterior GRF for ULE than crutches ( p < 0.05) as well as for CrI than CrU ( p < 0.05). Conclusions: The present study provides biomechanical data related to the spatio-temporal parameters and GRFs for the swing-through crutch gait in patients with the lower extremity injuries.
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