Tarmast, Daniel
(2016)
Effects of commbined sago-soy supplementation on cycling time trial performance in the heat.
PhD thesis, Universiti Sains Malaysia.
Abstract
The effects of carbohydrate intake and a combination of carbohydrate and protein
intake on endurance performance have been studied by many researchers with equivocal
findings. In this study, local food products such as sago starch (containing 88%
carbohydrate) and a soy–protein isolate (containing amino acids) has been used. The purpose
of the current study was to examine the effects of sago, soy, and iso–caloric combination of
sago+soy supplementations during 90 minutes steady–state cycling at 60 % VO2max, on a
subsequent 20–km cycling time trial performance in the heat (~31 °C; 70 % relative
humidity). Twelve well–trained male cyclists (age: 19.0 ± 5.6 years, body weight: 60.1 ±
11.2 kg, height: 170.8 ± 7.6 cm, and VO2max: 56.5 ± 6.5 mL.kg-1.min-1) representing
Kelantan (state level) cycling team were recruited for this randomised single–blind placebo–
controlled crossover study. Following preliminary trials, to investigate the VO2max and to
determine workload of the steady–state cycling, participants performed four experimental
trials. The experimental trials consisted of a 90–minute steady–state pedalling at 60 % of
VO2max, followed by a 20–km cycling time trial. From the beginning of the experimental
trials and at 20–minute intervals during the steady–state cycling (0, 20, 40, 60, and 80
minutes), participants consumed 200 mL of either: 7.5 % Sago, 7.5 % Soy, 6.0 % Sago + 1.5
% Soy, or placebo.
No significant differences were found in time–to–complete the 20–km time trial
regardless of the drink ingested (p > 0.05). Metabolic responses including plasma
concentrations of glucose and insulin were increased during the steady–state cycling in the
sago and sago+soy trials compared with soy and placebo trials. At the end of the 20–km
cycling time trial, the plasma lactate concentration was increased significantly in all trials (p
< 0.001), and the plasma free fatty acids concentration was significantly higher in the
placebo and soy trials than the sago and sago+soy trials (p < 0.001). There were no
significant differences between the trials in plasma concentrations of creatine kinase and F2–
Isoprostanes after the experimental trials (p > 0.05). The present study demonstrated that
ingestion of sago, soy, and iso–caloric sago+soy combined supplementation did not improve
the 20–km cycling time trial performance in the heat despite the availability of a higher level
of plasma glucose and insulin. Hence, carbohydrate alone or a carbohydrate+protein
combined supplementation may not be beneficial in exercise performance, specifically in the
heat.
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