Lower Limb and Trunk Biomechanics After Fatigue in Competitive Female Irish Dancers

Context: Because of the increasing popularity of participation in Irish dance, the incidence of lower limb injuries is high among this competitive population. Objective: To investigate the effects of fatigue on the peak lower limb and trunk angles as well as the peak lower limb joint forces and moments of competitive female Irish dancers during the performance of a dance-specific single-limb landing. Design: Cross-sectional study. Setting: Laboratory. Patients or Other Participants: Fourteen healthy, female, competitive Irish dancers (age = 19.4 ± 3.7 years, height = 165.3 ± 5.9 cm, mass = 57.9 ± 8.2 kg). Intervention(s): Participants performed an Irish dance–specific leap before and after a dance-specific fatigue protocol. During each landing movement, 3-dimensional lower limb kinematics (250 Hz) and ground reaction forces (1000 Hz) were collected. Paired t tests were performed to determine the differences (P ≤ .05) in lower limb and trunk biomechanics prefatigue and postfatigue. Main Outcome Measure(s): Peak lower limb and trunk angles as well as peak lower limb joint reaction forces and external moments. Results: Compared with the prefatigue trials, dancers landed with reduced ankle plantar flexion (P = .003) and hip external rotation (P = .007) and increased hip-adduction alignment (P = .034) postfatigue. Dancers displayed greater anterior shear (P = .003) and compressive (P = .024) forces at the ankle and greater external knee-flexion moments (P = .024) during the postfatigue compared with the prefatigue landing trials. Conclusions: When fatigued, dancers displayed a decline in landing performance in terms of aesthetics as well as increased ankle- and knee-joint loading, potentially exposing them to a greater risk of injuries.

Can the Weight of an External Breast Prosthesis Influence Trunk Biomechanics during Functional Movement in Postmastectomy Women?

Introduction. Recent papers indicate that one-side mastectomy can produce deleterious effects on the posture and musculoskeletal system. This study was conducted to better understand the underlying mechanisms involved in trunk motion in external prosthesis users.Objective. The aim was to evaluate the changes in surface electromyographic (SEMG) activity of the erector spinae muscles (ES) in postmastectomy women with and without breast prostheses during functional body movement tests.Methods. In 51 one-side postmastectomy women the SEMG muscle activity of bilateral ES was measured during symmetrical and asymmetrical dynamic activities in a counterbalanced manner with different weights of the breast prosthesis. Range-of-motion measurements were taken for forward bending, backward bending, lateral bending, and rotation.Results. The mean level of the ES activity in the lumbar region was not affected by the weight of the external breast prosthesis during most of the functional body tests (P>0.05). The activity of ES during functional body tests with and without different external breast prostheses did not differ between the two sides of the trunk (mastectomy and nonmastectomy) for most of the movement tests (P>0.05).Conclusion. The lumbar ES activity during functional tests is not associated with the weight of the external breast prosthesis in postmastectomy women.