Collections > Electronic Theses and Dissertations > The Time Course of Changes in Neuromuscular Function during and following Creatine Loading

The purposes of the present study were to determine the effect of Creatine (Cr) supplementation on 1) voluntary isometric and isokinetic strength and 2) active and passive range of motion (ROM) during loading and the subsequent washout period. The secondary purpose was to address any possible underlying neuromuscular mechanisms that might influence these changes. Using a double-blinded, placebo-controlled, matched-paired, randomized design, 40 males were assigned to a Cr (n=20, age: 20.3 ± 2.1 yrs,) or a placebo group (Pl; 20.4 ± 2.3 yrs) group. Participants supplemented four times daily for five days with 5g Cr + 20g dextrose or 20g dextrose. Testing was conducted prior to supplementation, during the loading phase (days 2, 4 & 6), and during the washout period (day 20 & 35). Muscular strength was examined with a maximal isometric and isokinetic (30, 90 & 120°*sec-1) muscle action of the plantar flexors on a calibrated isokinetic dynamometer. Muscle activation was determined by examining percent voluntary activation (%VA) and normalized electromyographic (EMG) amplitudes. Passive ROM , common and relative passive stiffness values were determined from a slow passive ROM assessment on a dynamometer. Active ROM was determined as the maximal dorsiflexion possible. Total body water, extracellular water, and intracellular water were measured with Bioimpedance Spectroscopy. Panoramic ultrasound imaging was used to address architectural changes in muscle cross sectional area, pennation angle, and fascicle length. Resting evoked twitch properties were performed to examine Cr-induced changes in Ca²+ kinetics. Magnetic resonance spectroscopy (MRS) was used to evaluate Cr uptake by the muscle in a subset of participants (Cr = 4; Pl = 4). Mass and fluid distribution for the Cr group did not significantly (P>0.11) differ from the Pl group over the course of the study. There was no significant interactions for all strength measures (P>0.36) or active and passive ROM (P>0.15), or any of the possible underlying mechanism (P>0.05). There were no changes in Cr stores (P>0.05). Overall, the results of this study suggest that Cr supplementation alone does not influence neuromuscular function or any of the underlying factors that could improve strength or limit ROM.