Influence of Caffeine on HRV and Exercise Performance in Spinal Cord Injury
Condition: Caffeine; Spinal Cord Injury
MeSH terms: Spinal Cord Injuries
Study type: Interventional

Summary: 
      The aim is to investigate the influence of caffeine on heart rate variability and on
      performance in a 3 min exercise test in different population groups (able-bodied, paraplegic
      and tetraplegic subjects).

      In general, the investigators are interested in the differences between the heart rate
      variability before and after caffeine supplementation and if the subjects exercise
      performance is enhanced using this type of supplementation. Another objective is to see
      whether there are differences between able-bodied and disabled subjects.

      Tetraplegic subjects showed in some previous studies no Low-Frequency-component (LF) for
      heart rate variability and no increase in catecholamines after the ingestion of caffeine.
      Therefore the investigators think, that tetraplegic subjects won't show any ergogenic effect
      in exercise performance after the intake of caffeine. On the other hand, paraplegic subjects
      should show similar differences of heart rate variability after the ingestion of caffeine as
      able-bodied subjects. Paraplegic subjects should benefit from caffeine supplementation in an
      increase in exercise performance.
    

Detailed description: 
      This study will be conducted in a placebo-controlled, double-blind and randomised study
      protocol. Every subject has to undergo three test session at the sports medicine in Nottwil.
      At the first visit, the investigators will check the subjects fitness using a health
      questionnaire with specific question about diseases and family health history. Additionally,
      subjects has to perform a maximal exercise test (ramp protocol at the arm crank ergometer) to
      measure maximal oxygen uptake, maximal heart rate and maximal power output. After a little
      break, subjects have to perform a familiarization trial at the arm crank ergometer. They have
      to perform exactly the same test as they have to perform later in the two test sessions.

      Minimum two days later the subjects visits the sports medicine Nottwil for the first test
      session. At first, they have to answer some specific question about sleep, recent training,
      recent nutritional intake and the actual health condition. Afterwards, they have to lie down
      for a 10min rest where after 9min blood pressure will be measured. With a heart rate monitor
      HRV will be measured during 5 min in supine position and afterwards during 6 min in sitting
      position. Metronomic breathing (15x/min) is mandatory and will be simulated through a
      metronome. During the HRV measurement also tidal volume will be measured. As the first HRV
      measurement session is finished, a blood withdrawal will be taken to measure catecholamine
      concentrations. Then, when all these measurements are completed, a supplement (either
      caffeine or the placebo) will be ingested in gelatine capsules. After the ingestion of these
      capsules, the subject has a 40 min break where they can read something or just relax. During
      these 40 min physical activity or the ingestion of any nutrition is prohibited.

      After these 40min, the second HRV measurement starts. The process of this measurement is
      exactly the same as for the first HRV measurement. They lay down for a 10min rest with blood
      pressure measurement after 9 min. Afterwards again a 5min HRV measurement in supine position
      and a 6min measurement in sitting position. Tidal volume is measured during this HRV
      measurement.

      When this second HRV measurement session is finished, a second blood withdrawal has to be
      taken. That means, one hour after the ingestion of either placebo or caffeine, catecholamine
      are analysed for a second time. If the blood is taken, the warm up can start. After the
      standardised warm up lactate concentration of the blood is analysed taking 10 ul of blood
      from the earlobe. The subject will be asked to evaluate the warm up with the rate of
      perceived exertion (following the Borg scale). If everything is in order, the 3min exercise
      test can start. During this test, respiratory parameters will be measured using an Oxycon Pro
      device (device to measure oxygen consumption). Just after having finished these 3 min of
      exercising, for a second time lactate concentration will be measured and again they have to
      rate the exertion using the Borg scale.

      After a short 5min break the third HRV measurement starts. Again HRV will be measured during
      a 5min time in supine position and a 6min time in sitting position. Tidal volume will be
      measured during the whole HRV measurement. With this HRV measurement the first test session
      is finished and a second test session will be conducted at least more than two days later in
      a randomised manner.

      The first session with the familiarization trial will be finished in around 75 min. For the
      two test sessions the subject has to be at the sports medicine for around 2 hours.

      In the following chart, the test sessions are visually displayed. The administrated dose of
      caffeine is defined to 6mg per kg bodyweight for all our subjects. Caffeine will be filled in
      gelatine capsules.

      Also the placebo (Mannitol) will be filled in gelatine capsules and the subjects have to
      ingest the same amount of capsules for both supplements.

      30 subjects will be tested in total. In each group 10 subjects will participate. That means
      10 healthy able-bodied subjects, 10 tetraplegic (C5-7, American Impairment Score (AIS) A) and
      10 paraplegic (sub Th8, AIS A) subjects will be tested. As it is not easy to find 10
      physically active, completely injured tetraplegic subjects, a number of 10 subjects should be
      sufficient for this pilot study.

      As the investigators know from previous studies conducted with disabled subjects, the level
      of the lesion is one critical point. Therefore, the investigators tried to include subjects
      with almost the same lesion level and all sensory and motoric completely lesioned. This could
      aid us to have more homogenous groups of different populations.

      Inclusion criteria: healthy, non-smoking men, minimal 3x45min physical activity per week,
      tetraplegic (C5 to C7) or paraplegic (sub Th8), complete lesion, more than 6 month after
      rehabilitation program Exclusion: drugs or supplements which influences heart rate
      variability, Diabetes
    

Intervention name(s): Caffeine; Placebo (Mannitol)
Intervention type(s): Dietary Supplement; Dietary Supplement
Intervention description(s): Caffeine will be filled in gelatine capsules and administrated in a dosage of 6mg per kg body mass; Mannitol filled in gelatine capsules
Intervention MeSH terms: Mannitol; Caffeine
Allocation: Randomized
Intervention model: Factorial Assignment
Masking: Double (Participant, Care Provider)
Primary purpose: Treatment
Keywords: heart rate variability; exercise performance