The objective of this trial is to determine the effects of dietary supplementation with the amino acids, L-arginine and L-citrulline, on endurance performance and mitochondrial respiration in healthy men compared to supplementation with L-arginine alone and a placebo supplement.
This study is a randomized, double-blind, cross over trial of L-arginine and L-citrulline supplementation, L-arginine supplementation alone and placebo supplementation in healthy men. The intervention period will be 8-11 weeks for each participant and a minimum of 15 individuals will be recruited and enrolled to complete the trial. Subjects will complete the experimental protocol described below over 3 individual 10 day supplementation periods, separated by washout periods of approximately 2 weeks. Subjects will ingest corn-starch as a placebo, L-arginine (3g/day) or L-arginine (1.5 g/day) + L-citrulline (1.5g/day). On day 7 of the supplementation period, a skeletal muscle biopsy and blood sample will be obtained from the subjects to investigate mitochondrial function and blood amino acid and nitric oxide levels. On day 10 of the supplementation period, subjects will complete a performance test on a cycle ergometer to investigate their endurance performance. These assessments will be performed to determine the effects of co-ingesting L-arginine and L-citrulline compared to L-arginine alone and placebo administration.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
DOUBLE
Enrollment
18
Dietary Supplement: L-arginine and L-citrulline supplement, L-arginine supplement, or placebo supplement (corn-starch) Subjects will complete 3 individual 10 day supplementation periods, separated by washout periods of approximately 2 weeks.
On day 10 of each supplementation period, subjects will complete a performance test on a cycle ergometer to investigate their endurance performance.
School of Sport, Exercise and Health Sciences
Loughborough, Leicester, United Kingdom
Change in Endurance performance on a cycle ergometer between L-arginine supplementation and placebo supplementation
On day 10 of the supplementation periods, subjects will complete a performance test on a cycle ergometer to investigate their endurance performance
Time frame: 8-11 weeks
Change in Endurance performance on a cycle ergometer between L-arginine + L-citrulline supplementation and placebo supplementation
On day 10 of the supplementation periods, subjects will complete a performance test on a cycle ergometer to investigate their endurance performance
Time frame: 8-11 weeks
Changes of mitochondrial function in skeletal muscle between L-arginine supplementation and placebo supplementation
On day 7 of the supplementation periods, a skeletal muscle biopsy sample will be obtained from subjects to investigate mitochondrial function.
Time frame: 8-11 weeks
Changes of mitochondrial function in skeletal muscle between L-arginine + L-citrulline supplementation and placebo supplementation
On day 7 of the supplementation periods, a skeletal muscle biopsy sample will be obtained from subjects to investigate mitochondrial function.
Time frame: 8-11 weeks
Changes of amino acid and nitric oxide biomarkers levels in plasma between L-arginine supplementation and placebo supplementation
On days 7 and 10 of the supplementation periods, a venous blood sample will be obtained from subjects to investigate amino acid and nitric oxide biomarkers levels in plasma.
Time frame: 8-11 weeks
Changes of amino acid and nitric oxide biomarkers levels in plasma between L-arginine + L-citrulline supplementation and placebo supplementation
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On days 7 and 10 of the supplementation periods, a venous blood sample will be obtained from subjects to investigate amino acid and nitric oxide biomarkers levels in plasma.
Time frame: 8-11 weeks
Changes in muscle oxygenation between L-arginine supplementation and placebo supplementation
On day 10 of the supplementation periods, skeletal muscle oxygenation will be assessed using near-infrared spectroscopy to reveal the tissue saturation index during exercise.
Time frame: 8-11 weeks
Changes in muscle oxygenation between L-arginine + L-citrulline supplementation and placebo supplementation
On day 10 of the supplementation periods, skeletal muscle oxygenation will be assessed using near-infrared spectroscopy to reveal the tissue saturation index during exercise.
Time frame: 8-11 weeks
Changes in subjective feeling during and after exercise between L-arginine supplementation and placebo supplementation
On day 10 of the supplementation period, subjective feeling during (using the 6-20 ratings of perceived exertion scale) and after (using a 100 mm visual analogue scale where 0 mm = no pain and 100 m = maximal pain) exercise will be assessed. Subjective feeling will also be assessed on the morning of day 11 of each supplementation period.
Time frame: 8-11 weeks
Changes in subjective feeling during and after exercise between L-arginine + L-citrulline supplementation and placebo supplementation
On day 10 of the supplementation period, subjective feeling during (using the 6-20 ratings of perceived exertion scale) and after (using a 100 mm visual analogue scale where 0 mm = no pain and 100 m = maximal pain) exercise will be assessed. Subjective feeling will also be assessed on the morning of day 11 of each supplementation period.
Time frame: 8-11 weeks