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Vol. 54. Issue 202.
Pages 55-64 (April - June 2019)
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Vol. 54. Issue 202.
Pages 55-64 (April - June 2019)
Original article
Experimental principal component analysis of fatigue in cyclists who have taken an oral L-tryptophan supplement
Análisis experimental del componente principal de la fatiga en ciclistas a quienes se había administrado un suplemento oral de oral L-triptófano
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Ignasi de Yzaguirre Mauraa,
Corresponding author
ignasi.izaguirre@gencat.cat

Corresponding authors at: Sports Medicine Unit, Catalan Sports Council, Government of Catalonia. Carrer de Sant Mateu, 37-47, Esplugues de Llobregat, Barcelona, 08950, Spain.
, Casimiro Javierre Garcésb, Antoia Lizarraga Dallob, Ramon Segura Cardonab
a Sports Medicine Unit, Catalan Sports Council, Government of Catalonia, Spain
b Department of Physiological Sciences, Medical School, University of Barcelona, Barcelona, Spain
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Tables (5)
Table 1. Physiological profile of subjects.
Table 2. Evolution of plasma tryptophan levels from the start of the trial.
Table 3. The “p” statistics of different parameters analysed at rest, compared with the values at 80% at maximum intensity, discriminating the statistical significance “p” placebo vs. “p” tryptophan.
Table 4.
Table 5. Evolution of the hematocrit values a long the different steps of the trials. (The differences are not statistically significant – p≤0.4).
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Abstract
Background

Since the 1980s the role of tryptophan in modulating fatigue has been the subject of debate. According to some models, tryptophan delays the onset of fatigue. Conversely, in other models, this amino acid is implicated in generating fatigue. This study attempts to shed some light on the debate.

Method

Ten elite (non-professional) road racing cyclists took part in a double-blind study employing paired data under standardised dietary and training conditions. Each volunteer did two trials, one with tryptophan supplementation (TRP) and the other with placebo (PLB). Various body fuel, plasma amino acid and renal function parameters were analysed in relation to fatigue data obtained using the Borg test. Blood pressure, pupil size and haematocrit values were also monitored. The parameters obtained were used to examine the principal components of fatigue in said test.

Objective

To confirm that, under test conditions, oral L-tryptophan supplementation has a favourable influence on fatigue perception during exercise.

Results

The principal components of fatigue, as reflected by the Borg test in this study, fit the following model: Perception of fatigue attained=8.406050586+(0.126275247*% load intensity)(0.031521537*cholesterol mg/dl)+(0.051002322*HDL cholesterol mg/dl)(0.017130681*tryptophan mmol/ml)(0.004545865*glycinemmol/ml)+(0.082894085*methioninemmol/ml). (Multiple correlation coefficient=0.90; coefficient of determination R2=0.82; adjusted R2=0.81; standard error: 1.82; observations: 75).

Renal function

Urea: (TRP: 45.6±6.5mg/dl vs. PLB: 44.1±5.7; p<0.4); creatinine: (TRP: 90.4±12.0 vs. PLB: 88.4±11.8mg/dl; p<0.9); resting pupil size: (TRP: 0.38±0.07AU vs. PLB: 0.35±0.08AU; p<0.01); haematocrit: (TRP: 45.3%±1.5% vs. PLB: 46.1%±2.6%; p<0.40).

Conclusions

Higher tryptophan levels reduced the increased subjective perception of fatigue (SPF). In the component analysis the impact of tryptophan was estimated as 4% in our model. Tryptophan supplementation did not affect renal function. Tryptophan supplementation altered pupil size. At the dose used, tryptophan supplementation proved effective for the first 2h following the last intake of the tryptophan supplement.

Keywords:
Fatigue
Cyclists
Oral L-tryptophan supplement
Resumen
Antecedentes

Desde los años 80, el papel del triptófano para modular la fatiga ha sido objeto de debate. Con arreglo a algunos modelos, el triptófano demora el inicio de la fatiga. Por el contrario, en otros modelos, dicho aminoácido está implicado en la generación de fatiga. Este estudio trata de arrojar cierta luz al debate.

Método

Diez ciclistas de carretera de élite (no profesionales) tomaron parte en un estudio doble ciego utilizando datos pareados en condiciones dietéticas y de entrenamiento. Cada voluntario realizó dos pruebas: una con suplemento de triptófano (TRP) y otra con placebo (PLB). Se analizaron diversos parámetros en cuanto a energéticos corporales, aminoácidos en plasma y función renal, con relación a los datos sobre fatiga obtenidos mediante la prueba de Borg. También se supervisaron los valores de presión arterial, tamaño de la pupila y hematocrito. Los parámetros obtenidos se utilizaron para examinar los componentes principales de la fatiga en dicha prueba.

Objetivo

Confirmar que, en condiciones de prueba, el suplemento oral de L-triptófano influye favorablemente en la percepción de la fatiga durante el ejercicio.

Resultados

Los componentes principales de la fatiga, reflejados en este estudio mediante la prueba de Borg, se ajustaron al modelo siguiente: Percepción de fatiga obtenida=8,406050586+(0,126275247*% intensidad de carga)(0,031521537*colesterolmg/dl)+(0,051002322*HDL colesterol mg/dl)(0,017130681*triptófanommol/ml)(0,004545865*glicina mmol/ml)+(0,082894085*metionina mmol/ml). (Coeficiente de correlación múltiple=0,9; coeficiente de determinación R2=0,82; R2 ajustado=0,81; error estándar: 1,82; observaciones: 75).

Función renal

Urea: (TRP: 45,6±6,5mg/dl vs PLB: 44,1±5,7; p<0,4); creatinina: (TRP: 90,4±12 vs. PLB: 88,4±11,8mg/dl; p<0,9); tamaño de la pupila en reposo: (TRP: 0,38±0,07 AU vs. PLB: 0,35±0,08 AU; p<0,01); hematocrito: (TRP: 45,3%±1,5% vs. PLB: 46,1%±2,6%; p<0,4).

Conclusiones

Los niveles superiores de triptófano redujeron el incremento de percepción subjetiva de la fatiga (SPF). En el análisis de componente, el impacto del triptófano se calculó como un 4% en nuestro modelo. El suplemento de triptófano no afectó a la función renal, pero sí alteró el tamaño de la pupila. A la dosis utilizada, dicho suplemento de triptófano resultó ser efectivo durante las dos primeras horas siguientes a la última ingesta del mismo.

Palabras clave:
Fatiga
Ciclistas
Suplemento oral de L-triptófano

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