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Original articles  SPORT NUTRITION AND SUPPLEMENTATION


The Journal of Sports Medicine and Physical Fitness 2003 December;43(4):481-7

Copyright © 2009 EDIZIONI MINERVA MEDICA

lingua: Inglese

Effects of creatine loading on muscular strength and endurance of female softball players

Ayoama R., Hiruma E., Sasaki H.

Human Per­for­mance Labor­a­tory, Depart­ment of ­Sports Sci­ences and Man­age­ment, School of ­Human Sci­ence, Osaka Inter­na­tional Uni­ver­sity, Osaka, ­Japan


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Aim. The pur­pose of ­this ­study was to deter­mine the ­effects of Cr sup­ple­men­ta­tion on ­muscle ­strength and endu­rance of the ­trained ­females, the ­effect of anaer­obic exer­cises per­formed ­before the sup­ple­men­ta­tion and dis­ap­pear­ance of the ­effects on the per­for­mance.
­Methods. ­Twenty-six col­le­giate ­female soft­ball ­players ­were ­divided ­into the Cr1, 2, Con­trol (­Cont.)1 or 2 ­group, ran­domly. ­They per­formed max­imal 2-iso­metric and 30-iso­ki­netic ­knee exten­sions at the ­angular veloc­ities of 180° and 60°/s. There­after, the sub­jects of the Cr2 and ­Cont.2 ­groups per­formed resis­tance exer­cises ­with 10 RM and ­cycling ­with 0.01 kg . kg-1 ­body ­weight, alter­nately ­during the 1st ­week. ­During the 2nd ­week, the sub­jects of the Cr1 and 2 ­groups ­ingested 20 g Cr a day for 1 week. There­after, the sub­jects in the Cr2 ­group con­tinued 3 g Cr inges­tion a day for 2 weeks ­while the Cr1 ­group ­ingested the ­same ­amount of pla­cebo ­during the 3rd and 4th ­weeks. The sub­jects of the ­Cont.1, 2 ­groups ­ingested the ­same ­amount and ­taste of pla­cebo ­during the 1st to 4th ­weeks. ­This ­study was under­gone in ­double ­blind ­fashion. The sim­ilar meas­ure­ments, to ­which the sub­jects per­formed the 1st day, ­were car­ried out on the ­final day of the 2nd, 3rd and 4th ­weeks.
­Results. ­Though max­imal iso­metric ­strength did not ­differ in ­intra- and ­inter­groups, the iso­ki­netic ­peak ­torque in the Cr1 ­group was sig­nif­i­cantly ­decreased in the 4th meas­ure­ment (p<0.01). The ­mean ­torque of the 1st to 10th ­knee con­trac­tions at 60°/s was sig­nif­i­cantly ­decreased ­from the 2nd meas­ure­ment in the ­Cont.1, 2 ­groups, com­pared ­with ­that in the 1st meas­ure­ment (p<0.01). In the Cr ­groups, the sig­nif­i­cant ­decrease was ­detected ­from the 3rd in the Cr1 and in the 4th meas­ure­ment in the Cr2 ­group. The ­mean ­torque of the ­latter 20 con­trac­tions at 180°/s was sig­nif­i­cantly ­increased in the Cr2 ­group (p<0.001). In the 1st meas­ure­ment, the ­mean ­torque in the Cr1 ­group was sig­nif­i­cantly ­higher ­than ­that in the Cr2 ­group (p<0.05). How­ever, the dif­fer­ences ­between Cr1 and 2 ­groups ­were not ­detected ­from the 2nd meas­ure­ment.
Con­clu­sion. Twenty g Cr sup­ple­men­ta­tion a day for a ­week to the ­trained ­females ­improves not the max­imal ­static ­strength and ­dynamic ­peak ­torque but the ­mean ­strength and endu­rance of ­repeated con­trac­tions. How­ever, the ­effects on ­females are not so ­great as ­that ­ever ­found in ­males. The ­effects are ­enhanced by anaer­obic exer­cises per­formed ­before the sup­ple­men­ta­tion and ­would dis­ap­pear in a ­week if the sup­ple­men­ta­tion ­were ­stopped.

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