The Effect of Creatine Loading on Neuromuscular Fatigue in Women.

• Autores: Abbie E. Smith, Jeffrey R. Stout, Eric D. Ryan, Joel T. Cramer, David H. Fukuda, Pablo B. Costa
• Localización: Medicine & Science in Sports & exercise: Official Journal of the American College of Sports Medicine, ISSN 0195-9131, Vol. 46, Nº. 5, 2014, págs. 990-997
• Idioma: inglés
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• Resumen

  • AB 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.