Document Title: Noyes-IES-Sep05.shtml
Article Title: Isokinetic profile and differences in tibial rotation strength between male and female athletes 11 to 17 years of age
Authors: Frank R Noyes and Sue D Barber-Westin
Publication: Isokinetics and Exercise Science
Date: September 2005
Volume 13, Number 5, pages 1-9
Keywords: Isokinetics, female-athlete knee-injury prevention, ACL injury prevention, male-female disparity, gender discrepancy, testing, screening, neuromuscular indices, tibial rotation isokinetic muscle strength, reference values.

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Comments: This penetratingly thought-provoking article found substantial differences in various kinesiological characteristics (as measured with a Biodex machine), both as a function of age and gender. But some of the attributes varied only with age, and then only in males. (With males, muscle strength was much greater in the 14-17 age group than in the 11-13 age group.) It was noted that males have faster times to peak torque, for internal rotation, compared to females. The study notes the importance of dynamic muscular stabilization of the knee joint in protecting the ACL. The authors also comment on the lasting and worrisome reduction in internal-rotation strength (ranging from 13% to a staggering 31%) that results from hamstring-type (semitendinosus-gracilis, hence STG/DLSTG) ACL-graft harvesting.

Abstract

Our objective was to examine age and sex associated development of isokinetic tibial rotation strength in 94 athletes aged 11 to 17 y. A calibrated Biodex system 3 was used to measure internal rotation (IR) and external rotation (ER) peak torque and time to peak torque (TPT) at 120 /s and 180 /s, and knee extension and fiexion peak torque at 180 /s. All data were normalized for body weight and ANOVA identified significant (p < 0.05) effects of lower limb dominance, age and gender. Males aged 14 to 17 y had significantly greater mean IR, ER, flexion, and extension peak torques than males aged 11 to 13 y. No such age-related effect existed in females. There was no difference between genders aged 11 to 13 y in isokinetic strength. Males aged 14 to 17 y had on average 17% greater IR strength, 28% faster time to reach IR peak torque, 17% greater extension strength, and 20% greater knee flexion strength than age-matched females. To conclude, no sex differences were found in peak torque or TPT in knee IR, ER, extension or flexion in athletes II to 13 y. Age related changes were found in these factors in males, but not in females.

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