Effects of creatine loading on muscular strength and endurance of female softball players.
OBJECTIVE
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 degrees and 60 degrees /s. Thereafter, the subjects of the Cr2 and Cont.2 groups performed resistance exercises with 10 RM and cycling with 0.01 kg x kg-1 body weight, alternately during the 1(st) week. During the 2(nd) 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 3(rd) and 4(th) weeks. The subjects of the Cont.1, 2 groups ingested the same amount and taste of placebo during the 1(st) to 4(th) weeks. This study was undergone in double blind fashion. The similar measurements, to which the subjects performed the 1(st) day, were carried out on the final day of the 2(nd), 3(rd) and 4(th) 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 4(th) measurement (p<0.01). The mean torque of the 1(st) to 10th knee contractions at 60 inverted exclamation mark /s was significantly decreased from the 2(nd) measurement in the Cont.1, 2 groups, compared with that in the 1(st) measurement (p<0.01). In the Cr groups, the significant decrease was detected from the 3(rd) in the Cr1 and in the 4(th) measurement in the Cr2 group. The mean torque of the latter 20 contractions at 180 inverted exclamation mark /s was significantly increased in the Cr2 group (p<0.001). In the 1(st) 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 2(nd) measurement.


CONCLUSIONS
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.
Ayoama
R
R
Human Performance Laboratory, Department of Sports Sciences and Management, School of Human Science, Osaka International University, Osaka, Japan.
Hiruma
E
E
Sasaki
H
H
D000293:Adolescent; D000328:Adult; D001484:Baseball / Q000502:physiology; D003401:Creatine / Q000494:pharmacology*; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000187:drug effects*; D007717:Knee / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects*; D010807:Physical Endurance / Q000187:drug effects*; D019415:Torque
D003401:Creatine