Objective To explore the optimal falling height parameters for single-leg drop jump,so as toaddress the bilateral imbalance in the lower limbs of athletes and provide a reference for coaches to design training plans accurately and effectively.Methods Twelve first-grade male athletes were re-cruited for the study,including five track and field sprinters and seven basketball players(age:20.41±1.11 years,height:189.19±9.15 cm,weight:83.50±12.08 kg).The vertical jump platform was used to test the optimal counter-movement jump(CMJ)height for the dominant and non-dominant sides of the subject's lower extremities,and to determine the three falling heights of the low height(medium height minus 5 cm),medium height(50%of the optimal unilateral lower-limb CMJ height)and high height(medium height plus 5 cm).Six parameters of the drop jump performance,including buffer time,leg stiffness,peak vertical ground reaction force(vGRFpeak),the rate of force development(RFD),power,root mean square(RMS)of surface electromyogram signals were collected synchronous-ly using the Vicon Motion Capture System(200 Hz),Delsys portable wireless telemetry EMG test sys-tem and Kistler three-dimensional force platform(1000 Hz).Results(1)At the medium height,the av-erage buffer time,leg stiffness,vGRFpeak,RFD,RMS and power of either leg were significantly bet-ter than at the other two heights(P<0.05),and the leg stiffness of the non-dominant leg was signifi-cantly inferior to the dominant leg(P<0.05).(2)At the high height,the average buffer time,vGRFpeak and RMS of the dominant leg were significantly better than at low height(P<0.05),while the average buffer time,leg stiffness,vGRFpeak,RFD,power and RMS of the non-dominant legs were significant-ly worse than the dominant legs(P<0.05).Conclusion Coaches or athletes can choose the medium height(50%optimal unilateral lower-limb CMJ height)designed in this study and schedule unilateral lower limb drop jump training to optimize the athletic performance of the dominant or non-dominant legs to the greatest extent.However,as the falling height increases,the gap in athletic performance between the bilateral lower limbs tends to become more pronounced(especially at high height),thus the training should focus on strengthening the eccentric contraction ability and stability of the non-dom-inant side to avoid bilateral imbalance.

In this study, a new Bacillus velezensis strain Bv-303 was identified and its biocontrol effect against rice bacterial-blight (BB) disease caused by Xanthomonas oryzae pv. oryzae (Xoo) was investigated. Cell-free supernatant (CFS) of strain Bv-303 under different growth conditions were prepared to test the antagonistic activity and stability against Xoo by the Oxford-cup method in vitro. The antibacterial effect of strain Bv-303 to BB disease in rice were further analyzed in vivo by spraying the cell-culture broth (CCB), CFS and cell-suspension water (CSW), respectively, on the rice leaves inoculated with Xoo. Additionally, rice seeds germination rate and seedling growth under the strain Bv-303 CCB treatment were tested. The results showed that the strain Bv-303 CFS significantly inhibited Xoo growth by 85.7%‒88.0% in vitro, which was also stable under extreme environment conditions such as heat, acid, alkali and ultraviolet light. As tested in vivo, spraying the CCB, CFS or CSW of strain Bv-303 on the Xoo-infected leaves enhanced rice plant resistance to BB disease, with CCB showing the highest increase (62.7%) in disease-resistance. Notably, CCB does not have negative effects on rice seed germination and seedling growth. Therefore, strain Bv-303 has great potential for biocontrol of the rice BB disease.
Oryza ; Fatigue Syndrome, Chronic ; Bacillus ; Xanthomonas ; Plant Diseases/microbiology*