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| ID | Type | Description | Link |
|---|---|---|---|
| MOST 111-2410-H-028-002-MY3 | Other Grant/Funding Number | National Science and Technology Council, Taiwan |
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Caffeine is widely used by rugby players for its performance-enhancing effects. The main questions it aims to answer are: (1) the impact of caffeine supplementation on various performance metrics, including distance covered at different speeds, acceleration, deceleration, collisions, and repeated high-intensity efforts; and (2) reactive agility, across four matches over two consecutive days in collegiate male rugby sevens players.A position-matched, double-blind, randomized crossover design was employed, with six male collegiate rugby players (mean height: 1.78 ± 0.09 m, mean weight: 81.3 ± 9.2 kg) participating in two trials. Each trial consisted of a two-day tournament, with two matches per day. Movement was monitored using global positioning system units.
This study employed a position-matched, double-blind, randomized crossover design. Pairs of participants with similar playing positions, specifically forwards or backs/scrum halves, were randomly assigned to either the caffeine or placebo trial. Each trial comprised a two-day rugby sevens tournament, with participants playing two matches per day. Following a 13-day washout period, participants switched to the alternate trial. Both the participants and the research personnel were blinded to the supplementation condition throughout the study period, with the assignment of supplements disclosed to research personnel only after all data analyses were completed.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Caffeine | Experimental | In the caffeine trial, participants ingested a capsule containing 3 mg/kg caffeine (Wako Pure Chemical Industries, Ltd., Osaka, Japan) 60 min prior to the match. |
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| Placebo | Placebo Comparator | In the placebo trial, participants ingested a capsule containing starch (Chung-Yu Biotech Co LTD, Taichung, Taiwan) at the same time point. |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Caffeine 6mg/kg | Dietary Supplement | In the caffeine trial, participants ingested a capsule containing 3 mg/kg caffeine 60 min prior to each rugby sevens match. There was 2 matches per day. So the total dosage is 6 mg/kg/ day |
| Measure | Description | Time Frame |
|---|---|---|
| Total Distance and Distance Covered in Speed Zones | This variable was measured with wearable global positioning system device during rugby sevens matches. Speed is divided into six zones: standing and walking (0-6 km/h), jogging (6-12 km/h), cruising (12-14 km/h), striding (14-18 km/h), high-intensity running (18-20 km/h), and sprinting (> 20 km/h). The distance covered in each speed zone and the total distance covered were recorded. | Each trial contained 2 days, with 2 matches on each day. Each participant completed 2 trials |
| Acceleration and Deceleration | This variable was measured with wearable global positioning system device during rugby sevens matches. For an activity to be included in the analysis, the movement speed must exceed 5 km/h, and the acceleration must be greater than 2 m/s² or the deceleration must be less than -2 m/s², sustained for more than 0.9 s. If the interval between two movements is less than 1 s, the subsequent movement will be combined with the previous one for analysis. The frequency and distance covered during these acceleration and deceleration phases were recorded. | Each trial contained 2 days, with 2 matches on each day. Each participant completed 2 trials |
| collision | This variable was measured with wearable global positioning system device during rugby sevens matches. Collision is defined as the number of times a participant accumulates 0.5 s standing after body contact resulting in a fall. Specific collision events include rucks, tackles, and instances where a player falls after contact | Each trial contained 2 days, with 2 matches on each day. Each participant completed 2 trials |
| Repeated High-Intensity Effort | This variable was measured with wearable global positioning system device during rugby sevens matches. A repeated high-intensity effort is defined as the completion of three or more high-intensity actions in succession, with rest periods of no more than 21 s between each action. The criteria for high-intensity actions include a movement speed of at least 14 km/h, an acceleration of at least 2 m/s², and a deceleration of at least -2 m/s² |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Affiliation | Role |
|---|---|---|
| Chen-Kang Chang, PhD | National Taiwan University of Sport | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| National Taiwan University of Sport | Taichung | 404 | Taiwan |
| PubMed Identifier | Type | Citation | Retractions |
|---|---|---|---|
| 23462927 | Result | Del Coso J, Portillo J, Munoz G, Abian-Vicen J, Gonzalez-Millan C, Munoz-Guerra J. Caffeine-containing energy drink improves sprint performance during an international rugby sevens competition. Amino Acids. 2013 Jun;44(6):1511-9. doi: 10.1007/s00726-013-1473-5. Epub 2013 Mar 5. |
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| ID | Term |
|---|---|
| D009043 | Motor Activity |
| ID | Term |
|---|---|
| D001519 | Behavior |
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| ID | Term |
|---|---|
| D002110 | Caffeine |
| ID | Term |
|---|---|
| D014970 | Xanthines |
| D000470 | Alkaloids |
| D006571 | Heterocyclic Compounds |
| D011688 | Purinones |
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2 types of Intervention: caffeine or placebo. Arm 1: Caffeine trial: Participants ingested a capsule containing 3 mg/kg caffeine (Wako Pure Chemical Industries, Ltd., Osaka, Japan) 60 min prior to the match.
Arm 2: Placebo trial: Participants ingested a capsule containing starch (Chung-Yu Biotech Co LTD, Taichung, Taiwan) at the same time point.
The capsules used in both trials were identical in appearance. The caffeine and placebo supplements were prepared by a laboratory technician who was independent of the study.
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The capsules used in both trials were identical in appearance. The caffeine and placebo supplements were prepared by a laboratory technician who was independent of the study.
| Placebo | Dietary Supplement | In the placebo trial, participants ingested a capsule containing starch 60 min before each rugby sevens match. There were 2 matches per day |
|
| Each trial contained 2 days, with 2 matches on each day. Each participant completed 2 trials |
| Reactive Agility | The participants sprinted with the ball, passing through a light gate, after which an indicator light immediately displayed a left or right direction. The participants had to respond by changing direction according to the indicator and continue moving until they passed the second light gate positioned 1.5 m away from the indicator. The fastest time from two attempts was used for analysis. | Each trial contained 2 days, with 2 matches on each day. Reactive agility was measured before each match. Each participant completed 2 trials |
| D011687 |
| Purines |
| D006574 | Heterocyclic Compounds, 2-Ring |
| D000072471 | Heterocyclic Compounds, Fused-Ring |