Letters to the Editor

SJ. The differential effects of fatigue on reflex response timing and amplitude in males and females. Journal of Electromyography and Kinesiology. 2002; 12:351-360 Abstract:We examined the effects of fatigue on patellar tendon reflex responses in males and females. A spring-loaded reflex hammer elicited a standardized tendon tap with the knee positioned in an isokinetic dynamometer and flexed to 85°. We recorded vastus lateralis activity (SEMG) and knee extension force production at the distal tibia (force transducer). Reflex trials were performed before and after (immediate, 2, 4, and 6 min) an isokinetic fatigue protocol to 50% MVC (90°/s). For each event, pre-motor time (PMT), electromechanical delay (EMD), and total motor time (TMT) were obtained, as well as EMG amplitude (EMGamp), time to peak EMG (EMGtpk), peak force amplitude (Famp), time to peak force (Ftpk), EMG:force ratio (E:F), and rate of force production (Frate=N/ms). TMT increased significantly in females following fatigue, while males showed no change. The increased TMT was due to an increased EMD with fatigue, while PMT was unaffected. EMGamp and Famp were somewhat diminished in females yet significantly augmented in males following fatigue, likely accounting for the differential changes in EMD noted. Results suggest males and females may respond differently to isokinetic fatigue, with males having a greater capacity to compensate for contraction force failure when responding to mechanical perturbations.

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The differential effects of fatigue on reflex response timing and amplitude in males and females

Moore

Drouin

Gansneder

et al. 2002

Journal of Electromyography and Kinesiology

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The Effect of the Menstrual Cycle on Anterior Cruciate Ligament Injuries in Women as Determined by Hormone Levels

Wojtys

Huston

Boynton³

et al. 2002

Am J Sports Med

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317

264

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Anterior cruciate ligament injury rates are reported to be two to eight times higher in women than in men within the same sport. Because the menstrual cycle with its monthly hormonal fluctuations is one of the most basic differences between men and women, we investigated the association between the distribution of confirmed anterior cruciate ligament tears and menstrual cycle phase. Sixty-nine female athletes who sustained an acute anterior cruciate ligament injury were studied within 24 hours of injury at four centers. The mechanism of injury, menstrual cycle details, use of oral contraceptives, and history of previous injury were recorded. Urine samples were collected to validate menstrual cycle phase by measurement of estrogen, progesterone, and luteinizing hormone metabolites and creatinine levels at the time of the anterior cruciate ligament tear. Results from the hormone assays indicate that the women had a significantly greater than expected percentage of anterior cruciate ligament injuries during midcycle (ovulatory phase) and a less than expected percentage of those injuries during the luteal phase of the menstrual cycle. Oral contraceptive use diminished the significant association between anterior cruciate ligament tear distribution and the ovulatory phase.

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Letters to the Editor

Cited by 2 publications

References 4 publications

The differential effects of fatigue on reflex response timing and amplitude in males and females

The differential effects of fatigue on reflex response timing and amplitude in males and females

The Effect of the Menstrual Cycle on Anterior Cruciate Ligament Injuries in Women as Determined by Hormone Levels

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