The effects of strength training on the neuromuscular characteristics of a stop-jump task in female recreational athletes Public Deposited

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  • March 21, 2019
Creator
  • Herman, Daniel Curtis
    • Affiliation: School of Medicine, UNC/NCSU Joint Department of Biomedical Engineering
Abstract
  • Objective: To examine the effects of strength training on lower extremity joint kinematics, kinetics, and muscle activation. Design and Settings: A randomized controlled experimental design was employed. Subjects performed 5 stop-jump tasks and 3-maximum voluntary isometric contraction (MVIC) tasks before and after completing either a 9-week lower extremity strength training program (intervention) or 9-weeks of abstinence from strength training (control). Subjects: A total of 66 females who were healthy, recreational athletes were randomly assigned to either the intervention (n=33, age=22.5±2.3 yrs, ht=1.67 plus or minus .07 m, wt=63.5 plus or minus 9.2 kg) or control (n=33, age=22.5 plus or minus 3.8 yrs, ht=1.67 plus or minus .06 m, wt=61.1 plus or minus 8.35 kg) group. Measurements: Three-dimensional videography, force plates, and telemetry EMG were used to record kinematic, kinetic, and muscle activation data during the stop-jump task. A hand-held dynamometer was used to collect the MVIC strength data. Dependent variables included knee anterior shear force (K-ASF); knee flexion, hip flexion, and knee valgus joint angles at K-ASF; knee extension, hip flexion, knee valgus, and hip abduction moments at K-ASF, and preparatory (200msec prior to footstrike) and landing phase EMG amplitudes of the vastus lateralis, vastus medialis, rectus femoris, biceps femoris, medial hamstrings, gluteus medius, and gluteus maximus. MVIC strength for quadriceps, hamstrings, gluteus medius, and gluteus maximus were also assessed. Statistical analyses were performed using a 2 [group] X 2 [time] repeated-measures ANOVA (alpha<.05). Post-hoc t-tests were performed to investigate significant interactions. Results: The intervention group increased in MVIC strength subsequent to the strength training protocol (p<.001 for all muscles). However, intervention group EMG amplitudes decreased in the vastus lateralis (p=.002), vastus medialis (p=.001), and rectus femoris (p=.004) during the preparatory phase and in the vastus lateralis (p=.008) during the landing phase. No significant differences were observed in subject kinetics or kinematics. Conclusions: The results indicate that a 9-week single-modality intervention program based on strength training is not sufficient to alter neuromuscular characteristics in female recreational athletes. Subject muscular strength increased significantly, but subjects may be compensating by decreasing muscle activation thereby maintaining similar motion kinetics and kinematics. Further research is needed to investigate the effects of strength training in different populations and in combination with other intervention modalities.
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  • In Copyright
Advisor
  • Padua, Darin A.
  • Yu, Bing
Degree granting institution
  • University of North Carolina at Chapel Hill
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