Caffeine (CAF) ingestion leads to ergogenic effects in high-intensity and endurance exercise in able-bodied (AB) athletes. To date, it is unclear whether such an effect could be detected in wheelchair
athletes as well due to impaired sympathetic nervous system activation.
The study investigated the effects of CAF on upper body performance in para- (P) and tetraplegic (T) compared to AB participants. Additionally, heart rate variability (HRV), blood pressure (BP) and
tidal volume (VT) were assessed to gain more information about sympathetic activation.
17 AB (median [minimum; maximum]; VO2peak 39.9ml/min/kg [23.6; 57.6]), 10 P (VO2peak 34.4ml/min/kg [19.5; 48.8]) and 7 T participants (VO2peak 13.6ml/min/kg [8.6; 16.3]) participated in this
double-blind, placebo-controlled and randomized study. Participants performed twice a 3min all-out arm crank test 1 hour after the ingestion of either 6mg/kg CAF or placebo (PLC). Plasma CAF,
epinephrine (EPI) and norepinephrine (NOR) concentrations were analyzed pre- and post-ingestion. Pre- and 40min post-ingestion, HRV, VT during HRV measurement and BP were assessed.
There was no significant increase in peak and mean power over 3min after the ingestion of CAF compared to PLC in the three groups. The median for peak power showed an increase of 46W (AB), 21W (P) and
2W (T) after CAF ingestion compared to PLC. Performance in the first 30s and 60s of the test after CAF ingestion was significantly enhanced in P (p=0.028) but not in the other groups (AB: p=0.44, T:
Plasma CAF concentration significantly increased in all three groups (AB: p=0.005; P: p=0.008; T: p = 0.018) post CAF ingestion. A significant increase from pre to post CAF ingestion in EPI was found
in AB (p=0.002) and in P (p=0.032) but not in T (p=0.63). Most HRV parameters did not change post CAF ingestion compared to PLC, whereas LF/HF ratio was significantly reduced in P (p=0.028) and total
power significantly increased in AB (p=0.023). VT significantly increased post CAF ingestion in AB (p=0.021) and P (p=0.036) but not in T (p=0.34). Systolic and diastolic BP increased significantly
post CAF ingestion in the AB (SBP: p=0.003; DBP: p=0.021) and T (SBP: p=0.043; DBP: p=0.042) but not in P (SBP: p=0.09; DBP: p=0.33).
CAF seemed to enhance performance between 30 and 60s in P but not in AB and T. However, a clinically relevant increase in peak power occurred in AB and P. VT increased from pre to post CAF ingestion
in AB and P possibly due to an increase in plasma EPI. Furthermore, CAF ingestion seems to elevate blood pressure in all three groups.