The effects of creatine supplementation and three days of isokinetic training on muscle strength, power output, and neuromuscular function Julie Culbertson

Objectives Background Information Purpose Research Questions and Hypotheses Study Design Methods Data Analysis Assumptions, Delimitations, and Limitations Practical Applications

Definition of Terms Rate of Velocity Development (RVD) – the acceleration of the limb during a maximal, voluntary, concentric isokinetic muscle action Peak Torque (PT) – the highest torque achieved during the muscle action Mean Power Output (MP) – average power generated during the muscle action Electromyography (EMG) – recording of the muscle action potentials Mechanomyography (MMG) – recording of the lateral oscillations produced by contracting muscle fibers

EMG and MMG EMG Amplitude Reflective of the number of motor units recruited EMG Frequency Reflective of the muscle action potential conduction velocity of the activated motor units MMG Amplitude Directly related to motor unit recruitment, inversely related to muscle stiffness MMG Frequency Provides information on the average motor unit firing rate (rate coding)

Short Term Resistance Training Prevost et al. Increase in strength in as few as 2 sessions at a fast velocity (4.71 rad·s -1 ), with a similar training velocity No change in muscle hypertrophy Thus, strength increases suggested to be due to neural adaptations

Short Term Resistance Training Brown and Whitehurst Showed a decrease in RVD after 2 training sessions without an increase in strength Decreases in RVD were velocity-specific Suggesting that training is more effective when at the velocity of the actual activity No increase in muscle cross-sectional area RVD changes may be explained by neural adaptations

Creatine Supplementation Creatine monohydrate increases muscle strength and performance following training Kambis and Pizzedaz showed increased MP and a decreased time to PT after 5 days of supplementation, without increases in body weight or thigh circumference. Creatine can delay the onset of neuromuscular fatigue (Stout et al.) Larger amounts of creatine in the muscles, therefore increasing phosphocreatine resynthesis

Purpose To examine the effects of 3 days of isokinetic resistance training at 150°·s -1 in combination with oral creatine monohydrate supplementation and placebo on: PT MP RVD Time and frequency domains of surface EMG and MMG

Research Question Does the combination of resistance training and creatine monohydrate supplementation enhance muscle strength and neuromuscular performance?

Hypotheses Training-induced increases in PT, MP, RVD and EMG and MMG amplitude will be independent of creatine supplementation PT, MP, and RVD increases will be greater with supplementation, than placebo

Study Design Double-blind, placebo controlled, parallel design Subjects will be randomly assigned to 1 of 3 groups: CRE – Treatment drink (n=12) 68g CHO, 10.5g creatine monohydrate, 280 kcal PLA – Isocaloric placebo drink (n=12) CON – control group, no drink, no training (n=8) Days 1-6 – drinks given twice per day Days 7-8 – only one drink serving per day

Study Design – CRE and PLA

Methods Strength Testing (All 3 groups) Testing will occur on day 1, prior to training, and on day 9, after all training and supplementation. 5 min warm up on stationary cycle ergometer at 50 W and rpm 3 maximal voluntary concentric isokinetic leg extension muscle actions at 3 randomly ordered velocities 30, 150, and 270°·s -1 2 min rest between velocities Torque, position, velocity, EMG and MMG recorded

Methods Training Protocol (CRE and PLA groups) 3 training sessions, with 48 hours between – days 3, 5, and 7 5 min warm-up on stationary cycle ergometer 3 sets of 10 maximal, voluntary, concentric isokinetic leg extensions at 150°·s warm-up contractions before each set and 2 min of rest after each set Torque, position, and velocity recorded

Data Analysis Seven 3-way mixed factorial ANOVAs for PT, MP, RVD, EMG and MMG amplitude and median power frequency Time (pre- vs. post-training) x Group (CRE vs. PLA vs. CON) x Velocity (30°·s -1 vs. 150 °·s -1 vs. 270 °·s -1 ) Type I error rate set at 5% (p≤0.05)

Assumptions, Delimitations, Limitations Assumptions Theoretical Subjects will accurately answer the health history Subjects will not discuss testing, training, or experiences with subjects in other groups Subjects will put forth a maximal effort for each testing and training session Subjects will come in at the same time each day for supplements and training Statistical Population is normally distributed Homogeneity of variance Sample is randomly selected and randomly assigned to groups All data is based on the parametric scale

Assumptions, Delimitations, and Limitations Delimitations 32 males between 19 and 35 years of age Physically active – 1-5 hrs/week of structured or recreational exercise, not competitive athletes No medication that can interfere with exercise performance No nutritional supplements for at least 3 months prior to participation Limitations Subjects recruited from departmental courses and advertisements in PEB and ACT, therefore subject selection is not truly random No control group to undergo testing and training without supplementation

Practical Applications The potential to enhance muscle strength and performance after short term training and supplementation has implications for allied health professionals. Physical rehabilitation treatments are often limited in number, therefore if this protocol can enhance muscle gains more quickly, patients can reduce the risk of re-injury or prevent the need for alternative or more expensive treatments