Monopodal postural stability assessment by wireless inertial measurement units through the fast fourier transform

Abstract

Objectives: The aims of the present study were: (i) to describe the FFT multi-joint as monopodal postural stability measurement in well-trained athletes, (ii) to compare the withinsubject FTT between laterality, joints and body segments, and (iii) to establish the within and between-subject relationship between joints. Methods: Twelve national-level basketball players participated voluntarily in this investigation. The participants performed two 60-second repetitions of a monopodal stability test (one repetition with each lower limb), separated by three minutes of active recovery. All tests were recorded by four WIMU PROTM inertial devices located on the ankle, knee, lumbar spine and thoracic spine. The main variable was total acceleration (AcelT), where the Fourier Transform (FFT) was applied. Results: The higher instability results were found in the ankle and in the non-dominant lower limb (dominant=1.136±0.81 a.u.; non-dominant=1.169±.108 a.u.). In the body segment analysis, the greater percentage of differences (%diff) were shown between lumbar spine and knee in the dominant (%diff=-2.989%; d=0.87) and non-dominant lower limb (%diff=-3.243%; d=0.90). Finally, great between-subjects variability was found in all joints and body segments. Conclusions: The described protocol is proposed for monopodal postural stability assessment, being useful to provide information about the stability of joints and the body segment between joints. Besides, a within-subject analysis is recommended and the FFT calculation will enable a linear analysis of each test .