Report

Individuals with a SCI display large inter-individual variation in caffeine absorption

Great inter-individual variability in wheelchair performance responses have been reported during a 1500 m time trial (Flueck et al., 2014), 4-min maximal push and repeated 20 m sprints following caffeine (Graham-Paulson et al., 2015), especially in individuals with a spinal cord injury (SCI).

Lead academic:
Dr Terri Graham-Paulson
Additional academics:
Professor Vicky Tolfrey
Funder:
The Peter Harrison Foundation
  • The authors highlighted the potential for slower caffeine absorption due to delayed gastrointestinal transit times and prolonged gastric emptying, especially in those with a cervical lesion level (Kao et al., 1999).
  • Both metabolic and physiological functions are altered in individuals with a SCI, and the level and completeness of injury has been shown to influence drug pharmacokinetics.
  • There is therefore reason to believe that caffeine absorption may also be delayed in persons with a SCI.

Methods

  • 24 healthy males (8 able-bodied, 8 individuals with paraplegia (PARA) and 8 with tetraplegia (TETRA)) consumed 3 mg∙kg-1 caffeine in a fasted state.
  • Plasma caffeine [CAF], glucose, lactate, free-fatty acid [FFA] and catecholamine concentrations were measured during a 150 min rest period.

Main findings and applications

  • Different patterns of absorption were evident between groups (see figure).
  • Greater peak [CAF] was observed in TETRA, which may reflect slow metabolism and renal clearance due to impaired liver and kidney function following SCI.
  • A reduced blood volume may also result in a falsely large peak.
  • Large inter-individual variance was seen in both SCI groups which likely reflects the heterogeneity of this population regarding level and completeness of SCI.
  • Increased [FFA] despite no significant increase in catecholamine concentrations indicates a direct effect of caffeine on adipocytes.
  • Low catecholamine concentrations support previous data and reflect impaired sympathetic activation of the nervous system in TETRA.
  • There were no differences between groups’ blood glucose or lactate concentrations.
  • For short-term exercise caffeine should be consumed 70-80 min prior to performance.
  • TETRA may consider using a lower dose to elicit similar [CAF] to able-bodied individuals but it remains to be investigated whether this is ergogenic.

Reference

Graham-Paulson, T.S., Paulson, T.A.W., Perret, C., Tolfrey, K., Cordery, P. and Goosey-Tolfrey, V.L. (2016). Spinal cord injury level influences acute plasma caffeine responses. Medicine and Science in Sports and Exercise. Medicine and Science in Sports and Exercise. 49(2): 363-370. DOI: https://doi.org/10.1249/mss.0000000000001108