Effects of Whole Body Vibration on Force Production in Young, Middle-aged, and Older Men

Abstract

PURPOSE: The purpose of this study was to examine the influence of age on the ability to exert muscular force following whole body vibration in healthy males between the ages of 18–25, 35–45, and 55–64 years. METHODS: 50 total subjects were assigned to one of three groups depending solely on age. The three groups were young (n=20; 22.75±1.74 years), middle-aged (n=15; 40.53±3.07years), andold(n=15; 58.07±2.40 years). All subjects participated in a 2-hour testing session which consisted of pre- and post-trials for both countermovement vertical jumps and a maximal isometric leg extension, with a whole-body vibration intervention in between. The vibration protocol was 3 sets, 30-seconds in duration, at a frequency of 30 Hz on a low-amplitude. From these tests, several variables were obtained including; peak power, peak rate of force development, rate of force development index, peak force, time to peak force, average time to peak force, and EMG amplitude values for both the vastus lateralis and rectus femoris. RESULTS: Examination of the pre- and post-vibration values for each measure indicated a non-significant decrease in average peak power, average peak RFD, average peak force, average time to peak force (young only) and average EMG amplitude for both the VL and the RF. There were non-significant increases in RFD index, and time to peak force (middle-aged and old only). There were significantly higher values for pre-vibration values compared to post-vibration values across age groups for average peak power, average peak RFD, average peak force, and EMG amplitude for both the VL and RF. The young showed significantly higher values for average peak power, average peak force, and RF EMG amplitude when compared to the old across pre- and post-vibration. One significant age group by trial interaction occurred in the EMG amplitude for the VL. The young group decreased significantly more than both the middle and older groups. CONCLUSIONS: These results suggest that there is no significant influence of age on the ability to exert muscular force following whole body vibration in healthy males, with each age group generally demonstrating a post-vibration depression in performance parameters.