A Cunliffe1, O A Obeid, J Powell-Tuck. 1. Department of Human Nutrition, St Bartholomew's and Royal London School of Medicine and Dentistry, Queen Mary and Westfield College.
Abstract
OBJECTIVE: To examine the effect of L-tryptophan administration on subjective and objective measures of fatigue in healthy volunteers. SUBJECTS:Six healthy volunteers (4M:2F) were recruited from staff and students at the College. SETTING: Department of Human Nutrition, St. Bartholomews and the Royal London School of Medicine and Dentistry. DESIGN: Subjects were tested for central and peripheral fatigue using a visual analogue scale, flicker fusion frequency, grip strength, reaction time and wrist ergometry. In addition, plasma free tryptophan concentrations and Trp:LNAA ratio were determined. Measurements were made before, and at 1, 2, 3 and 4 h after drinking one of two test drinks. The drinks were of either caffeine free diet Coca-Cola (placebo) or caffeine free diet Coca-Cola plus L-tryptophan (30 mg/kg: active drink). Each of the six subjects was tested after placebo and active drink with a one week washout period between test days. RESULTS:Subjective fatigue was significantly increased following tryptophan compared to placebo (P < 0.002), and objective measures of central fatigue were significantly increased by tryptophan compared to placebo (flicker fusion frequency: P < 0.001; reaction time P < 0.001). No significant changes in grip strength were found following tryptophan compared to placebo, but a significant increase in ergometric work output was seen (P < 0.001). CONCLUSION:Tryptophan ingestion in the quantity 30 mg/kg leads to increased subjective and central fatigue. Increases in work output observed following tryptophan may be as a result of a reduced perception of discomfort during ergometry.
RCT Entities:
OBJECTIVE: To examine the effect of L-tryptophan administration on subjective and objective measures of fatigue in healthy volunteers. SUBJECTS: Six healthy volunteers (4M:2F) were recruited from staff and students at the College. SETTING: Department of Human Nutrition, St. Bartholomews and the Royal London School of Medicine and Dentistry. DESIGN: Subjects were tested for central and peripheral fatigue using a visual analogue scale, flicker fusion frequency, grip strength, reaction time and wrist ergometry. In addition, plasma free tryptophan concentrations and Trp:LNAA ratio were determined. Measurements were made before, and at 1, 2, 3 and 4 h after drinking one of two test drinks. The drinks were of either caffeine free diet Coca-Cola (placebo) or caffeine free diet Coca-Cola plus L-tryptophan (30 mg/kg: active drink). Each of the six subjects was tested after placebo and active drink with a one week washout period between test days. RESULTS: Subjective fatigue was significantly increased following tryptophan compared to placebo (P < 0.002), and objective measures of central fatigue were significantly increased by tryptophan compared to placebo (flicker fusion frequency: P < 0.001; reaction time P < 0.001). No significant changes in grip strength were found following tryptophan compared to placebo, but a significant increase in ergometric work output was seen (P < 0.001). CONCLUSION:Tryptophan ingestion in the quantity 30 mg/kg leads to increased subjective and central fatigue. Increases in work output observed following tryptophan may be as a result of a reduced perception of discomfort during ergometry.
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