Effects of linear and undulating periodization of strength training in the acceleration of skater children

Aim: This study aimed to compare the effects of linear periodization (LP) and undulating periodization (UP) of strength training on acceleration in skater children. Methods: Twenty-nine girls (9.67±1.29 years-old, 34.47±8.06kg, 1.39±0.13m) were distributed into two groups: linear periodization group (LPG, n=14) and undulating periodization group (UPG, n=15). Six levels of progressive training were designed based on activities such as multi-jumps, plyometrics, sled towing, and facilitated exercises. The training lasted 16 weeks, with a 1-h session on three non-consecutive days per week. The acceleration was recorded by digital videography following the major trochanter of the femur, at four moments and under two conditions: static (SS) and dynamic start (DS) in a rectilinear path. Statistical significance was set at 5%. Results: ANOVA indicated group*moment interaction in SS and DS for velocity (F3,81=7.883; p<0.001; pη2=0.226; F3,81=2.36; p=0.078; pη2=0.08-trend, respectively) and acceleration (F3,81=3.96; p=0.011; pη2=0.128; F3,81=2.92; p=0.039; pη2=0.098, respectively). Both groups increased velocity in SS and DS (UPG/SS: 1st=4.07, 2nd=9.75, 3rd=8.91, 4th=9.25m/s; LPG/SS: 1st=4.27, 2nd=7.13, 3rd=7.61, 4th=7.99m/s; UPG/DS: 1st=8.30, 2nd=8.73, 3rd=8.12, 4th=9.27m/s; LPG/DS: 1st=8.20, 2nd=8.31, 3rd=7.90, 4th=8.96m/s) and acceleration (UPG/SS: 1st=2.00, 2nd=8.69, 3rd=4.71, 4th=5.02m/s2; LPG/SS: 1st=2.37, 2nd=3.39, 3rd=3.68, 4th=4.12m/s2; UPG/DS: 1st=1.78, 2nd=1.97, 3rd=1.65, 4th=2.46m/s2; LPG/DS: 1st=1.67, 2nd=1.70, 3rd=1.48, 4th=1.93m/s2). Conclusion: Both strength training periodization protocols were effective in developing acceleration and velocity in girl skaters over 16 weeks; however, UP was more efficient than LP for improving acceleration.(AU)

Evaluation of upper limb load intensity based on biomechanical methods / 中华劳动卫生职业病杂志

Objective@#To establish a model for evaluating the upper limb load intensity of workers based on biomechanical methods, and to verify its effectiveness.@*Methods@#15 male volunteers participated in lifting test of 3 kinds of external force load in March 2015. Volunteers’ operating postures, forces, and subjective load intensities were collected. The biomechanical models of lifting operation were established with the input of operating postures and forces, and to output joint torque of shoulder, elbow and wrist. The simulation results were normalized by the maximum torque of each joint, and the relative joint torque was obtained. Then the upper limb load intensity evaluation model, which related with relative joint torque of shoulder, elbow and wrist, was established based on analytic hierarchy process. In order to validate the validity of the model, the assessment results of the model and the subjective load intensities of the volunteers were contrasted.@*Results@#The weight of shoulder joint (0.56) was larger than the weights of elbow and wrist (0.27 and 0.17) in the influence factors of the upper limb load. Pearson correlation analysis showed that the upper limb load intensities of the model were significantly correlated with the subjective load intensities of volunteers (r=0.863, P<0.05) . There was no significant difference between the two groups (t=0.105, P>0.05) .@*Conclusion@#The evaluation model of the upper limb load intensity based on biomechanical methods could be used for predicting and evaluating the upper limb load intensities of workers.