Year of Publication

2019

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Education

Department

Kinesiology and Health Promotion

First Advisor

Dr. Haley Bergstrom

Second Advisor

Dr. Mark Abel

Abstract

The very short-term resistance training (VST) model, utilizing only 2-3 training sessions, has been used to examine early phase skeletal muscle, neural, and performance adaptations. The VST model has previously been used to examine these early phase adaptations in bilateral and unilateral, isometric, isokinetic, and dynamic muscle actions in the limbs of the upper- and lower-body. The bilateral deficit (BLD) is a phenomenon in which the sum of the forces produced unilaterally is greater than the force produced bilaterally during maximal contraction of the limbs. The appearance of a bilateral deficit has been be related to various factors; including training status and mode of training (bilateral versus reciprocal muscle actions). No previous study, however, has examined the effects of VST on the BLD. The VST model has potential implications for examining acute changes in strength and neuromuscular responses of the trained muscles. These adaptations, however, may be specific to unilateral or bilateral training. Therefore, the purposes of this study were to: 1) examine one repetition maximum (1RM) strength and neuromuscular responses (EMG AMP, EMG MPF, MMG AMP, MMG MPF) during the measurement of bilateral and unilateral leg extension exercise before and after dynamic constant external resistance (DCER) VST; 2) examine the magnitude of the BLD; 3) examine the effect of bilateral versus unilateral training on the BLD; and 4) use the neuromuscular responses measured bilaterally and unilaterally to infer about the motor unit activation strategies that may underlie the BLD and changes in 1RM strength. Twenty-four (14 males, 10 females) subjects (mean ± SD age: 23.0 ± 3.2 yr; height: 174.7 ± 8.5 cm; body mass: 75.4 ± 14.1 kg) with no resistance training experience within the last three months were randomly assigned to either the bilateral (BL) training group or the unilateral (UL) training group. The subjects completed a total of seven visits, consisting of a familiarization, pre-test visit, three training visits, and one post-test visit. The pre-test visit was used to record the subject’s electromyographic (EMG) and mechanomyographic (MMG) responses from the right and left vastus lateralis (VL) during bilateral and unilateral seated maximum isometric voluntary contractions (MVIC) and 1RM. Visits four through six were the training sessions, with each subject preforming 5 sets of 6 repetitions utilizing 65% of the 1RM for resistance where the BL group trained both limbs (right and left) at the same time and the UL group trained both limbs separately. Visit seven was the post-test and the same testing procedures as the pre-test visit were followed. Statistical analyses consisted of four-way and three-way mixed model ANOVAs, with follow up three-, two- and one-way repeated measures and/or mixed model ANOVAs, Bonferroni corrected paired, and independent samples t-tests when appropriate. An alpha level of P ≤ 0.05 was considered statistically significant for all ANOVAs. The BL group demonstrated a significant increase (p = 0.006; 6.8%) in BL1RM pre- to post-test, but no change in unilateral summed (US1RM = right + left limb; p = 0.726) 1RM strength. The UL group demonstrated an 8.7% increase in BL strength collapsed across testing mode (BL1RM and US1RM) (p = 0.0001) and UL strength (p = 0.0001) collapsed across limb (UL left + UL right/2) from pre- to post-test. The BL group had a significant (p = 0.001) increase in the BI (indicating a decrease in the BLD) from pre- to post-test, but there was no significant change for the UL group. The BL group demonstrated a significant (p = 0.029) decrease in the EMG mean power frequency (MPF) measurement pre- to post-test, however the UL group showed no change. The unilateral movement, collapsed across limbs (unilateral left and unilateral right) also showed a significant (p = 0.022) decrease in the MMG MPF measurement pre- to post-test, whereas the BL movement showed no change. These findings indicated that BL and UL DCER training increased strength after 3 training sessions. The bilateral DCER training resulted in bilateral, but not unilateral strength increases and unilateral DCER training resulting in both bilateral and unilateral strength increases. However, bilateral training was the only mode of training that significantly decreased the BLD.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2019.405

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