Timing of Broccoli Sprout Intake to Improve Exercise Performance

Overview

This study examines how the timing of intake of a broccoli sprout-based drink (a natural source of isothiocyanates, ITCs) affects physiological responses, recovery, and performance after a standardized endurance cycling session. Healthy, endurance-trained adults (18-64 years) will complete four laboratory visits at the Swedish School of Sport and Health Sciences (GIH): one screening/physiology test visit and three intervention visits in a randomized, double-blind, placebo-controlled cross-over design. On intervention visits, participants will ingest either an active broccoli sprout drink (50 g sprouts) or a placebo drink based on alfalfa sprouts (50 g sprouts) according to randomization. The drink will be consumed either approximately 16 hours before exercise (the evening before) or approximately 3 hours before exercise (the morning of the test), enabling comparison of timing in relation to a standardized \~2-hour cycling protocol (individualized intensity) followed by a 10 km cycling time trial. Outcomes include measures of performance, heart rate, perceived exertion and recovery, blood glucose and lactate, and metabolic responses. Venous blood samples are collected at multiple time points before and after exercise and during the subsequent laboratory recovery period, and muscle biopsies are obtained at defined time points to assess muscle metabolism and recovery-related markers. Participants return \~24 hours after exercise for follow-up sampling after an overnight fast, including a glucose tolerance test

This is a randomized, double-blind, placebo-controlled cross-over study conducted at the Swedish School of Sport and Health Sciences (GIH), Stockholm, designed to isolate the effect of timing of isothiocyanate (ITC) intake from broccoli sprouts on exercise responses, recovery, and cycling performance. Each participant completes four laboratory visits: one screening/physiology visit and three intervention visits. The screening visit includes a health check and an incremental cycle test to determine maximal oxygen uptake and to individualize exercise intensities for subsequent visits; oxygen uptake is assessed by indirect calorimetry, and capillary fingertip samples are used to measure blood lactate and glucose during the test. A venous blood sample is collected at the screening visit. Intervention visits (three separate occasions) follow the same standardized test-day structure with different drink assignments according to randomization. The active drink consists of 50 g broccoli sprouts (ITC source) and the placebo drink consists of 50 g alfalfa sprouts. Drinks are administered to compare "subacute" intake (approximately 16 hours before exercise, the evening prior) versus "acute" intake (approximately 3 hours before exercise, the morning of the test day). The three intervention conditions are: (1) placebo at \~16 h plus placebo at \~3 h before the cycling protocol (control), (2) active at \~16 h plus placebo at \~3 h (subacute condition), and (3) placebo at \~16 h plus active at \~3 h (acute condition). Participants and investigators/test staff are blinded to drink identity at each visit. On each intervention test day, participants arrive to the laboratory (approximately 08:30) and compliance with pre-visit instructions is checked. Baseline samples are collected, including a muscle biopsy from vastus lateralis, venous blood, and saliva. Participants then complete a standardized, strenuous cycling protocol on an ergometer with individualized intensity based on the screening test (approximately 80% of VO2max). An example structure is repeated intervals around lactate threshold (e.g., 8 × 5 min work with short recovery), with physiological monitoring throughout. Heart rate is recorded continuously (smartwatch), and capillary blood lactate and glucose are measured at predefined time points during exercise. Oxygen uptake/energy metabolism may be monitored during portions of the protocol using indirect calorimetry. The exercise protocol includes a 10 km cycling performance test on the ergometer. In addition, approximately 4 hours after completion of the initial cycling bout (and following the relevant sampling time point), participants perform a second 10 km ergometer time trial in which they are instructed to perform as well as possible. Perceived exertion is recorded during exercise, and perceived recovery is assessed during the recovery period (e.g., Perceived Recovery Status Scale). Biological sampling is extensive to characterize acute and post-exercise recovery processes. At each intervention visit, venous blood is collected at 10 time points: pre-exercise, immediately post-exercise, and then once per hour during the subsequent 8-hour laboratory recovery period (approximately 4 mL per draw; \~40 mL per intervention visit). Muscle biopsies from vastus lateralis are collected at four time points per intervention visit: pre-exercise, immediately post-exercise, approximately 4 hours post-exercise, and approximately 24 hours post-exercise (separate incision sites; predetermined/randomized leg). Saliva sampling is also performed (including at baseline and at the end of the \~8-hour laboratory recovery period). During the 0-8 hour recovery period in the laboratory, standardized meals are provided. After approximately 8 hours in the laboratory, participants leave and return the next day (\~24 hours after exercise) for final sampling, including the last muscle biopsy. For the 24-hour visit, participants fast for at least 10 hours. A glucose tolerance test is performed at the 24-hour follow-up to assess post-exercise glucose regulation.