Acute tyrosine ingestion is thought to improve aerobic endurance, muscle strength and endurance, and anaerobic power of men undergoing severe physiologic stress. In a double-blind, crossover study, 20 men (32 ± 1 y old) underwent 2 loadcarriage treadmill sessions, 1 after taking tyrosine (150 mg/kg L-crystalline tyrosine) and 1 after taking placebo. Tyrosine dosage was based on subject weight and ingested 30 min before load carriage. A physical performance battery was administered after the load carriage: maximal and submaximal handgrip, pull-ups, and stair stepping with weight. Total time on treadmill was not significantly lengthened with ingestion of tyrosine (118.9 ± 1.4 min) as compared with placebo (119.2 ± 1.2 min). Total power for stair stepping (tyrosine 223 ± 8 watts, placebo 216 ± 9 watts) and muscle strength and endurance (handgrip) was not significantly improved by tyrosine ingestion. The results indicate that acute ingestion of tyrosine by healthy men has no measurable effect on endurance, muscle strength, or anaerobic power.
Erin E. Sutton, M. Regina Coll, and Patricia A. Deuster
Melissa R. Taylor, Erin E. Sutton, Wiebke S. Diestelkamp, and Kimberly Edginton Bigelow
The goal of this study was to examine the effects of 3 factors and their interactions on posturography: a period of time to become accustomed to the force platform before the initiation of data collection, presence of a visual fixation point, and participant talking during testing. The postural stability of 30 young adults and 30 older adults was evaluated to determine whether any observed effects were confounded with age. Analysis of variance techniques were used to test all possible combinations of the 3 factors. We hypothesized that all 3 factors would significantly affect postural stability. For both participant groups, the results suggest that a period of time to become accustomed to the force platform before the initiation of data collection and a visual fixation point significantly affect postural control measures, while brief participant talking does not. Despite this, no significant interactions existed suggesting that the effects of these factors, which may occur in clinical testing, do not depend on each other. Our results suggest that inconsistencies in posturography testing methods have the potential to significantly affect the results of posturography, underscoring the importance of developing a standardized testing methodology.