The effect of creatine loading on neuromuscular fatigue in women.

Abstract

PURPOSE:

This study aimed to examine the effects of intermittent isometric fatigue on maximal voluntary contraction (MVC) strength, percent voluntary activation (%VA), peak twitch force (PTF), peak rate of force development (PRFD), half relaxation time (HRT), and maximal compound action potential (M-wave) amplitude of the soleus and medial gastrocnemius muscles before and after creatine (Cr) loading.

METHODS:

Using a double-blinded, placebo-controlled, randomized design, 12 women were assigned to a Cr (n = 6; mean age ± SD = 23.3 ± 3.0 yr) or placebo (PL; n = 6; mean age ± SD = 21.3 ± 1.6 yr) group. Participants supplemented four times daily for 5 d with 5 g of Cr + 10 g of fructose or 10 g of fructose. At baseline and after testing, an isometric MVC and the twitch interpolation procedure were used before and after a 4-min isometric fatigue protocol of the plantarflexor muscles, which consisted of six intermittent duty cycles per minute (7-s contraction, 3-s relaxation) at 70% MVC.

RESULTS:

There were no interactions between the Cr and PL groups (P > 0.05) for any dependent variable. The fatigue protocol reduced voluntary strength (-17.8%, P < 0.001) and %VA (-3.7%, P = 0.005). Baseline PTF (P < 0.005) and PRFD (P < 0.001) values were less than those of all respective time points, but PTF value decreased from 3 min to 4 min and after testing (P < 0.005). HRT increased from baseline to minutes 1 and 2 and then returned to baseline at minutes 3 and 4 and after testing. The M-wave did not change (P > 0.05).

CONCLUSIONS:

Five days of Cr loading did not influence isometric force, %VA, evoked twitch properties, or the central and peripheral aspects of fatigue measured in this study.

• Authors: Abbie E Smith-Ryan, Eric D Ryan, David H Fukuda, Pablo B Costa, Joel T Cramer, Jeffrey R Stout
• Journal: Medicine and science in sports and exercise (Med Sci Sports Exerc) Vol. 46 Issue 5 Pg. 990-7 ( 2014) ISSN: 1530-0315 [Electronic] United States
• PMID: 24152706 (Publication Type: Journal Article, Randomized Controlled Trial)

Chemical References

• Sweetening Agents
• Fructose
• Creatine

Topics

• Adult
• Body Mass Index
• Creatine (administration & dosage)
• Dietary Supplements
• Double-Blind Method
• Female
• Fructose (administration & dosage)
• Humans
• Isometric Contraction (physiology)
• Muscle Fatigue (physiology)
• Muscle Relaxation (physiology)
• Muscle Strength (physiology)
• Muscle, Skeletal (physiology)
• Sweetening Agents (administration & dosage)
• Young Adult