Julie Culbertson

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

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

3. 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

4. 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)

5. 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

6. 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

7. 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

8. 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

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

10. 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

11. 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

12. Study Design – CRE and PLA

13. 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 60-70 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

14. 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-1 • 3-4 warm-up contractions before each set and 2 min of rest after each set • Torque, position, and velocity recorded

15. 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)

16. 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

17. 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

18. 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

19. Questions?

20. Thank You!