Abstract: BACKGROUND: A large number of studies have investigated the effects of whole body vibration training at different frequencies on muscle strength, but less is reported on the differences in the efficacy of vibration training at different frequencies on patellar tendinopathy.
OBJECTIVE: To explore the effect of eccentric training of quadriceps combined with different frequency of whole body vibration training on patellar tendinopathy.
METHODS: From April to June 2022, 48 patients with patellar tendinopathy were recruited from Wuhan Sports University and randomly divided into eccentric training group (n=12), 30 Hz group (n=12), 40 Hz group (n=12), and 50 Hz group (n=12). The eccentric training group only completed eccentric training of the quadriceps. The 30 Hz, 40 Hz and 50 Hz groups performed the whole body vibration training with the amplitude of 2 mm and frequencies of 30 Hz, 40 Hz and 50 Hz respectively on the basis of the eccentric training of the quadriceps. The intervention lasted for 8 weeks, three times a week. Before and after the intervention, the patients' surface electromyography signals of the quadriceps, kinematics and dynamics data of knee joint at the time of landing in deep jump and the time of peak vertical ground reaction, Visual Analogue Scale score, Victorian Institute of Sports Assessment-Patellar score were evaluated.
RESULTS AND CONCLUSION: After 8 weeks of intervention, compared with the eccentric training group, the median frequency of the lateral and medial femoris muscles were significantly higher in the 40 Hz and 50 Hz groups (P < 0.05). At the time of landing, the knee joint flexion angle and external rotation moment in the 40 Hz and 50 Hz groups were significantly lower than those in the eccentric training group (P < 0.05), while the knee joint flexion angle in the 50 Hz group was significantly lower than that in the 30 Hz group (P < 0.05). At the peak moment of vertical ground reaction, the knee extension torque in the 40 Hz group was significantly lower than that in the eccectric training group (P < 0.05); the knee flexion angle and knee extension torque in the 50 Hz group were 
significantly lower than those in the eccentric training group (P < 0.05). The Visual Analogue Scale scores in the 50 Hz and 40 Hz groups were significantly lower than those in the eccentric training group (P < 0.05). The Victorian Institute of Sports Assessment-Patellar score in the 50 Hz group was significantly higher than that in the eccentric training group and 30 Hz group (P < 0.05). To conclude, eccentric training of the quadriceps combined with 50 Hz whole body vibration training can significantly improve quadriceps’ strength, endurance and activation rate of the vastus lateralis muscle, reduce the pain of knee joint, and improve the function of the knee joint in patients with patellar tendinopathy.

Key words: patellar tendinopathy, eccentric training, whole body vibration training