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Background and Objective: Creatine is one of the most important and commonly used supplements athletes, although the molecular mechanisms of creatine and its side effects are less understood. The high level of the ceratin kinase enzyme and lactate dehydrogenase enzymes are considered to be a sign of cell damage. This study was done to determine the effect of creatine monohydrate supplementation on creatine kinase (CK) and lactate dehydrogenase (LDH) enzymes following a severe muscle contraction in female athletes.
Methods: In this double-blind clinical trial study, 30 female athletes were randomly divided into intervention (creatine supplementation 0.3 grams per body weight for 4 times duing 7 days and control (placebo, starch powder) groups. Blood sample was collected before supplementation (pre-test) and 24 hours after Cunningham exercise test (post-test) to measuring CK and LDH in each subject.
Results: After intervention, the level of CK (323±63 IU/L) and LDH (119±13 IU/L) in intervention group had no significant difference in compared to control group (CK: 328±44 IU/L and LDH: 122±14 IU/L).
Conclusion: The usage of a 7-day course of creatine supplement did not significantly change the CK and LDH levels following a severe muscle contraction in female athletes.

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Background and Objective: Genu varus deformity is associated with changes of lower limb muscle co-contraction and running economy. This study was done to evaluate the effect of using of brace in three different knee flexion angles on running economy and lower limb muscular co-contraction in individuals with genu varus.
Methods: This quasi-experimental study was done on active soccer male students including 15 healthy subjects (average age of 22.86±1.55 years) and 15 subjects with genu varus (average age of 22.13±1.80 years). The amount of electrical activity of the muscles (tibialis anterior, medial gastrocnemius, vastus medialis, vastus lateralis, rectus femoris, biceps femoris, semi-tendinosus) were recorded by electromyography system during four conditions of with and without using knee brace. After that, directed and general co-contraction was computed during running. The angles of brace were 15, 30, and 60 degrees. The values of VO2 max were recorded using of gas analyzer system to compute running economy.
Results: The ratio of respiratory exchange was significantly more in the genu varus group than healthy group (P<0.05). However, the acute effect of brace was not significant on running economy and ratio of respiratory exchange. The main effect of brace was significant for general co-contraction of knee joint during the loading phase (P<0.05). Paired wise comparison revealed significant greater general knee co-contraction during brace conditions (P<0.05). However, the general knee co-contraction during loading phase reduced while using brace 15 degree. The main effect of “brace” for ankle joint general co-contraction during the push-off phase was significant (P<0.05). Paired wise comparison revealed significant greater general ankle co-contraction during brace conditions at push-off phase (P<0.05).
Conclusion: Knee brace did not change running economy. However, the using of brace 15 degree improved general knee joint co-contraction during loading phase.

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Background and Objective: Genu varum is a lower limb deformity. This study was done to evaluate the effects of shoe aging on the general and directional contraction of ankle muscles during running in females with genu varum.
Methods: This case-control study was done on 30 female students (15 individuals with genu varum degree 2 and 15 healthy individuals) using new and old sneakers for 6 months in the sports biomechanics laboratory of the University of Mohaghegh Ardabili, Iran. Each subject was given a new pair of sneakers, and after the initial data collection, the subjects were asked to use them in their daily activities for at least an hour a day for 6 months. Electrical muscle activity was recorded using surface electromyography.
Results: There was no significant difference in the general and directional contractions if ankle muscles during the running phases.
Conclusion: Shoe aging has no effect on ankle joint co-contractions.