Timing of Meal and Caffeine Intake on Substrate Use and Exercise Efficiency
Condition: Healthy
Study type: Interventional

Summary: 
      During the past decades, considerable emphasis has been directed to analyzing the potential
      role of caffeine on substrate use and exercise performance. Research shows that caffeine
      ingestion prior to exercise has beneficial effects on submaximal exercise capacity and time
      trial protocols. This effect is mediated by an increase in plasma free fatty acids and
      intramuscular triglyceride utilization, preserving muscle and liver glycogen. Generally, a
      dose between 4 - 9 mg/kg body mass is administered to athletes in order to observe a positive
      or ergogenic effect. Caffeine ingestion (6 mg/kg) improved exercise performance in a long
      duration protocol (2 hours + ~ 30 min time trial) regardless of the administration time (1
      hour before or during exercise). Lower doses of caffeine (~ 1.5 mg/kg), when added to a
      carbohydrate solution increased exercise performance in a similar fashion. In rats, caffeine
      has been shown to have a biphasic action on postprandial glucose metabolism. When ingested
      before a meal, hepatic glycogenesis is blunted. Its ingestion during and after a meal allows
      glycogenesis to occur. Manipulating meal and caffeine timing before low intensity exercise,
      comparable to every-day life activities, is of great interest in assessing substrate use and
      muscular efficiency. it would be also interesting to see how this meal or caffeine timing
      manipulation influence the energetics of different phenotypes.
    

Detailed description: 
      Research shows that caffeine ingestion prior to exercise has beneficial effects on moderate
      to high exercise performance. Generally, a dose between 4 - 9 mg/kg body mass is administered
      to athletes in order to observe a positive effect.

      The aims of the study are the following: first, to investigate the effect of caffeine and/or
      meal on energy supply (% from fat and carbohydrate) during low intensity exercise. Second, to
      investigate the effect of timing and order of the above on energy supply before, during, and
      after exercise. Lastly, to assess exercise efficiency following the above protocols (work
      accomplished relative to the calories spent to accomplish the work).

      Healthy, untrained male and female subjects will be recruited for this study. Subjects will
      be excluded if they had a previous history of any limitation on physical ability,
      cardiovascular disease, taking supplements or medicine that might affect their metabolic
      rate, claustrophobic, or unstable bodyweight during the past 6 months. Subjects will be
      defined as sedentary, with a maximum of 30 minutes of moderate physical activity per day
      (assessed by questionnaire) excluding daily activities.

      During the first visit, participants will be informed about the experiment protocol, if
      agreed, they should give a written consent, answer a questionnaire (lifestyle), and get
      anthropometric and body composition measurements.

      On the day of testing, subjects will come to the laboratory at 08:00 fasted. All participants
      will be requested to avoid physical activity, caffeine, and dietary supplements in the 24h
      prior to testing.

      Energy expenditure is measured by indirect calorimetry. Briefly, participants will sit in a
      comfortable seat, using a ventilated hood with baseline energy expenditure. During this
      period, the participant is instructed to relax and avoid movements. Heart rate monitoring is
      included using a heart rate belt. Participants then complete the following protocols on five
      separate days (separated by at least 48 hours) in a randomized order:

      Protocol 1:

      A standardized meal (2 slices of toast bread + butter + Jam ~ 500 kcal) + caffeine (~200 mg)
      will be given to the participant. 2 hours later resting energy expenditure is measured using
      a facemask for 10 min while seated on a cycle ergometer. The participant will be asked to
      pedal at 60 revolutions per minute for 5 min per load at 20 watts (W), 35W, 50W, 65W, 80 W
      respectively.

      Protocol 2:

      A standardized meal will be given to the participant. 2 hours later caffeine will be given
      followed by the same protocol mentioned above.

      Protocol 3:

      Caffeine will be given to the participant. 2 hours later a standardized meal will be given
      followed by the same protocol mentioned above.

      Protocol 4:

      Caffeine will be given to the participant. 2 hours later the same protocol mentioned above
      will be applied.

      Protocol 5:

      A standardized meal will be given to the participant. 2 hours later the same protocol
      mentioned above will be applied.

      Manipulating meal and caffeine timing before low intensity exercise, comparable to every-day
      life activities, is of great interest in assessing energy supply and muscular efficiency in
      humans.

      There is no risks related to the study. Exercise is maintained at a low-to-moderate level
      comparable to everyday life. All data related to the subjects will be coded (# and initials,
      i.e. A001_ELIFAR) and kept confidential.
    

Intervention name(s): Caffeine
Intervention type(s): Dietary Supplement
Intervention description(s): Provide caffeine supplements with or without meal before exercise
Intervention MeSH terms: Caffeine
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Single (Participant)
Primary purpose: Other