No abstract

The mechanisms regulating the bilateral coordination of gait in humans are largely unknown. Our objective was to study how bilateral coordination changes as a result of gait speed modifications during over ground walking. 15 young adults wore force sensitive insoles that measured vertical forces used to determine the timing of the gait cycle events under three walking conditions (i.e., usual-walking, fast and slow). Ground reaction force impact (GRFI) associated with heel-strikes was also quantified, representing the potential contribution of sensory feedback to the regulation of gait. Gait asymmetry (GA) was quantified based on the differences between right and left swing times and the bilateral coordination of gait was assessed using the phase coordination index (PCI), a metric that quantifies the consistency and accuracy of the anti-phase stepping pattern. GA was preserved in the three different gait speeds. PCI was higher (reduced coordination) in the slow gait condition, compared to usual-walking (3.51% vs. 2.47%, respectively, p=0.002), but was not significantly affected in the fast condition. GRFI values were lower in the slow walking as compared to usual-walking and higher in the fast walking condition (p<0.001). Stepwise regression revealed that slowed gait related changes in PCI were not associated with the slowed gait related changes in GRFI. The present findings suggest that left-right anti-phase stepping is similar in normal and fast walking, but altered during slowed walking. This behavior might reflect a relative increase in attention resources required to regulate a slow gait speed, consistent with the possibility that cortical function and supraspinal input influences the bilateral coordination of gait.

In the present study, we tried to determine the association between joint ranges of motion, anatomical anomalies, body structure, dance discipline, and injuries in young female recreational dancers. A group of 1336 non-professional female dancers (age 8-16 years), were screened. The risk factors considered for injuries were: range of motion, body structure, anatomical anomalies, dance technique, and dance discipline. Sixty-one different types of injuries and symptoms were identified and later classified into four major categories: knee injuries, foot or ankle tendinopathy, back injuries, and non-categorized injuries. We found that 569 (42.6%) out of the 1336 screened dancers, were injured.The following factors were found to be associated with injuries (P < 0.05): (a) range of motion (e.g. dancers with hyper hip abduction are more prone to foot or ankle tendinopathies than dancers with hypo range of motion; (b) anatomical anomalies (scoliotic dancers manifested a higher rate of injuries than non-scoliotic dancers); (c) dance technique (dancers with incorrect technique of rolling-in were found to have more injuries than dancers with correct technique); (d) dance discipline (an association between time of practice en pointe and injury was observed); and (e) early age of onset of menarche decreased risk for an injury. No association between body structure and injury was found. Injuries among recreational dancers should not be overlooked, and therefore precautionary steps should be taken to reduce the risk of injury, such as screening for joint range of motion and anatomical anomalies. Certain dance positions (e.g. en pointe) should be practised only when the dancer has already acquired certain physical skills, and these practices should be time controlled.

The aim of the present study was to assess the prevalence and types of injuries in 1336 young, non-professional female dancers (age 8-16 years) who participated in a descriptive mixed (cross-sectional/ longitudinal) cohort study. Previous and current injuries were diagnosed and later classified into seven major categories. Our results show that 569 (42.6%) of the dancers examined manifested an injury. Advanced age and increased exposure to dance yielded an equivalent increase in the prevalence of injured girls: from 1 of 10 girls in the 8-year-old age cohort (mean = 1.05 per 1000 h) to 1 of 3 girls in the 14-year-old age cohort (mean = 1.25 per 1000 h). Time elapsing between first and second injuries decreased with age. Among the youngest group of dancers (8-9 years) the most common injury was tendonitis (41%), while in adolescent dancers (14-16 years) knee injuries became the leading cause of complaints (33%). We conclude that young, non-professional dancers are at high risk of injury. Dancers who had been injured in the past were at higher risk for re-injury. Tendonitis in the foot or ankle joint was a common injury among the youngest dancers, while knee injuries were common among adolescent dancers. A routine screening of this dancer population by an expert in dance medicine will reduce the risk for an injury.