Abstract
BACKGROUND: Maximal voluntary contraction (MVC) is widely regarded as signal of maximum grip strength and active muscle contraction in the forearm.
AIM: The aim of the study is to investigate the muscular performance and effects of anthropometric measurement on grip strength (GS) and endurance time (ET) of young college students before and after vibration therapy (VT) in supination forearm posture.
METHODS: A observational study design (4 days x 2 levels (before vibration exposure (BVE) and after exposure to vibration at frequency of 45 Hz, amplitude of 3g and duration of vibration exposure of 60 seconds) x 24 subjects) was used in this study. Changes due to intervention were assessed by measuring GS and ET at 50% MVC (before and after vibration training).
RESULTS: MANCOVA results showed vibration training frequency and training days significantly affect the GS (p<0.001) and ET (p<0.05). Compared with day 1 before vibration exposure (BVE) and day 4 after 45 Hz vibration training, MVC grip strength increased by 53.1% and endurance time increased by 37.07%. The Pearson correlation test showed that frequency of VT and days of exposure were not significantly associated with endurance time and grip strength.
CONCLUSIONS: Results showed a significant increase in GS and ET relative to VT frequency and training days. In addition, body weight and PL were the most important factors affecting ET, and palm circumference and forearm circumference are the most important factors affecting grip strength.

Key words: Supination posture, maximal voluntary contraction, grip strength, grip endurance time, and anthropometric measurements.