The goal of this clinical trial (randomised, double-blind, placebo-controlled crossover study) is to investigate whether supplementation with Ecklonia cava, a natural extract derived from brown seaweed, affects exercise performance and physiological responses in trained cyclists.

The main questions it aims to answer are:

Does Ecklonia cava supplementation improve cycling performance, including power output during steady-state exercise and short maximal sprints? Does Ecklonia cava supplementation influence physiological responses to exercise, such as blood glucose, blood lactate, heart rate, and oxygen consumption?

Researchers will compare Ecklonia cava supplementation to a placebo (a look-alike substance with no active ingredients) to determine whether the supplement has any effect on performance or physiological responses.

In this crossover design, all participants will receive both the Ecklonia cava supplement and the placebo on separate occasions, with a washout period between conditions.

Participants will:

Ingest either Ecklonia cava or a placebo 30 minutes before exercise testing Complete a 60-minute cycling protocol at a moderate intensity Perform repeated short-duration maximal sprint efforts following the steady-state exercise Attend laboratory testing sessions under both supplement and placebo conditions Undergo measurements of physiological responses, including blood glucose, blood lactate, heart rate, oxygen consumption, and respiratory exchange ratio Have exercise performance assessed through measures of power output during cycling

Inclusion Criteria:

• experienced in cycling (defined as completing at least four hours of cycle training per week with a minimum of two years of experience)

Exclusion Criteria:

• Smoker
• cardiovascular disease
• anti-hypertensive medication

Available on request.