Effects of Food Intake Sequence on Substrate Utilisation and Endurance Performance

Summary

The goal of this clinical trial is to understand how consuming a pre-exercise meal in different food intake sequences affects substrate utilisation and endurance exercise performance in healthy trained athletes. Specifically, the main questions it aims to answer are:

* Does consuming the pre-exercise meal in different food intake sequences alter the whole-body utilisation of fat and CHO at rest and during prolonged exercise at moderate to heavy intensities?
* Does consuming the pre-execise meal in different food intake sequences alter time-trial performance?
* Does consuming the pre-exercise meal in different food intake sequences alter other metabolic and physiological responses before, during or after exercise (i.e., blood glucose, blood lactate, heart rate (HR), ratings of perceived exertion (RPE), appetite)?

To address these questions, researchers will compare eating the dietary sources of rapidly absorbed CHO at the end (CHO-last meal pattern) or at the start (CHO-first meal pattern) of a standardised pre-exercise meal, in a randomised, counterbalanced, crossover design. Two hours after starting the pre-exercise meal, participants will perform a 60-min submaximal test on a cycling ergometer at two different intensities (30 min at 90% of the ventilatory threshold (VT) 1 and 30 min at 50% VT1-VT2), followed by a 10-km cycling time trial (TT).

In the screening visit participants will:

* Be screened for cardiometabolic conditions
* Perform an 8-12-min graded exercise test to determine their maximal pulmonary oxygen uptake (VO2max) and non-invasive submaximal anchors of performance (VT 1 and VT 2)
* Be familiarised to the experimental procedures

In experimental visits participants will:

* Follow guidelines pertaining to dietary intake, exercise and sleep in the previous 24 hours
* Have a standardised test meal in either the CHO-last or CHO-first food intake sequence
* Have 3 drops of capillary blood (0,9 µL in total) collected to measure glucose and lactate pre-meal, 15, 30, 45, 60, 90 and 120 min post-meal, every 15 min during submaximal exercise and post-TT
* Breathe into an indirect calorimetry mask for 5 min pre-meal, 15, 30, 45, 60, 90 and 120 min post-meal, every 15 min during submaximal exercise and post-TT
* Wear a HR monitor continuously during submaximal exercise and the TT
* Rate their appetite on visual analogue scales pre-meal, 15, 30, 45, 60, 90 and 120 min post-meal, and 30 min post-TT
* Rate their perceived exertion on RPE scales every 15 min during submaximal exercise, post-TT and 30 min post-TT.

Data will be compared within-participant between food intake sequences using linear mixed-effects models with random intercepts, to account for repeated measurements, interindividual variability, and potential missing data.

Conditions

• Substrate Metabolism
• Healthy Participants
• Endurance Exercise

Interventions

OTHER

Carbohydrate-last meal pattern

Skyr yoghurt, whey protein and almonds over \~5 min, immediately followed by white bread, strawberry jam, banana and pulp-free orange juice over \~10 min.

OTHER

Carbohydrate-first meal pattern

White bread, strawberry jam, banana and pulp-free orange juice over \~10 min, immediately followed by skyr yoghurt, whey protein and almonds over \~5 min.

Sponsors & Collaborators

• Portuguese Football Federation

  collaborator OTHER

• Fundação para a Ciência e a Tecnologia

  collaborator OTHER

• Universidade do Porto

  lead OTHER

Principal Investigators

• Rita Giro · FCNAUP, University of Porto; Federação Portuguesa de Futebol

Study Design

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

SINGLE

Model

CROSSOVER

Eligibility

Min Age

18 Years

Max Age

64 Years

Sex

MALE

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2026-04-01

Primary Completion

2026-06-09

Completion

2026-06-09

Countries

• Portugal

Study Locations