Experiments were designed to examine the visual contributions to performance of back aerial double somersaults by collegiate acrobats. Somersaults were performed on a trampoline under three visual conditions: (a) NORMAL acuity; (b) REDUCED acuity (subjects wore special contacts that blocked light reflected onto the central retina); and (c) NO VISION. Videotaped skill performances were rated by two NCAA judges and digitized for kinematic analyses. Subjects' performance scores were similar in NORMAL and REDUCED conditions and lowest in the NO VISION condition. Control of body movement, indicated by time-to-contact, was most variable in the NO VISION condition. Profiles of angular head and neck velocity revealed that when subjects could see, they slowed their heads prior to touchdown in time to process optical flow information and prepare for landing. There was not always enough time to process vision associated with object identification and prepare for touchdown. It was concluded that collegiate acrobats do not need to identify objects for their best back aerial double somersault performance.
Jan M. Hondzinski and Warren G. Darling
Jan M. Hondzinski, Li Li and Michael Welsch
We examined the effects of aging and lower limb sensory deficits (LLSD) on whole body control. Performances of a reaching task involving a step were measured in subjects with LLSD and young and older controls. Having LLSD was accompanied with greater reach errors and variability in lateral step deviations. Aging effects explained the smaller step deviations and longer movement times. These results suggest that older adults with LLSD have performance declines associated with deficits of the disease and aging that often differ, at least for this goal-directed discrete task. Furthermore, longer MT for older controls and shorter MT for LLSD subjects were associated with greater movement coupling. Longer movement periods likely offered older controls time to use sensory feedback to maintain good endpoint accuracy. Evidently, somatosensations from the limbs used during performance of whole body movements are required for the most accurate goal-directed control.