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Summary Previous work has shown that variable practice facilitates adaptation to novel visuomotor changes during throwing tasks and during obstacle avoidance on a solid floor. We asked if locomotor skill on an obstacle avoidance task on a compliant surface, and in a novel visuomotor environment, improved through training with variable practice on visuomotor changes. 61 normal adults practiced traversing the obstacle course; half the trials were done without visual changes, half the trials were done while wearing either sham or visual distortion lenses in single lens or multiple lens groups. Transfer tests on the obstacle course while wearing novel lenses showed significantly better scores with multiple lenses than sham; the single lens group did not differ from sham or multiple lens groups. Thus, performance in a novel visual environment, on a compliant surface improves most with variable practice training.

Temporary threshold shift (mean, 4.6 dB) was noted in R + 0 versus preflight conditions (P < 0.01). Small permanent threshold shifts (mean, 0.83 dB) were found at R + 3 and postflight follow-up compared with preflight in the lower frequencies (500 to 2000 Hz), and corresponding pure tone average (P < 0.001). Conclusions and significance The data indicate that a single Shuttle flight can induce a substantial temporary threshold shift and a small but statistically significant permanent threshold shift, particularly in the frequencies involved in speech reception. Although single-mission effects are small, cumulative effects over several missions may ultimately produce clinically significant hearing loss.

OBJECTIVES: The study goal was to determine whether a single Space Shuttle mission can induce decrements in astronaut hearing. STUDY DESIGN: We retrospectively compared audiogram information obtained from Space Shuttle astronauts at 10 days preflight, day of return (R + 0), 3 days after landing return (R + 3), and at a mean delayed postflight follow-up of 8 months. RESULTS: Temporary threshold shift (mean, 4.6 dB) was noted in R + 0 versus preflight conditions ( P < 0.01). Small permanent threshold shifts (mean, 0.83 dB) were found at R + 3 and postflight follow-up compared with preflight in the lower frequencies (500 to 2000 Hz), and corresponding pure tone average ( P < 0.001). CONCLUSIONS AND SIGNIFICANCE: The data indicate that a single Shuttle flight can induce a substantial temporary threshold shift and a small but statistically significant permanent threshold shift, particularly in the frequencies involved in speech reception. Although single-mission effects are small, cumulative effects over several missions may ultimately produce clinically significant hearing loss.