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EFFECTS OF GUARANA COMPARED TO MATCHED DOSE CAFFEINE: EXERCISE PERFORMANCE BENEFITS?

Abstract

Alec Harp1, Eduardo Marcedo Penna2, Brian Hack1, Tyler Talik1, Mindy Millard-Stafford, FACSM1. 1Georgia Institute of Technology, Atlanta, GA. 2Federal University of Pará, Belem.

BACKGROUND: Effects of guarana (Paullinia cupana) seed extract, a Brazilian plant containing caffeine but with additional bioactive compounds, has been observed to positively affect cognitive tasks but evidence on exercise performance is limited. The purpose of this study was to assess acute effects of guarana (GUA) compared to a matched dose of caffeine (CAF) on exercise performance. METHODS: Eleven endurance athletes (age: 20 ± 4.7 y, ht: 180.2 ± 7.2 cm, body mass: 73.9 ± 8.8 kg, V̇O2max: 54.6 ± 7.8 ml/kg/min) participated in a randomized, double-blind, crossover experiment. All subjects completed three trials ingesting capsules containing: 1) 100 mg CAF; 2) 100 mg GUA, or 3) placebo (P) 60-min prior to a 75-min cycling trial (fixed load 60-min steady state [SS] + self-paced 15-min time trial [TT]). Maximal isometric quadriceps strength was assessed before and after cycling. RESULTS: During SS, no differences (p >0.05) in oxygen consumption (15 min blocks averaging ~70-75% V̇O2max), heart rate (HR), or respiratory exchange ratio (RER) were observed among trials. During SS, blood glucose tended to be higher (p=0.13) with CAF (4.6 ± 0.5 mmol) versus P (4.4 ± 0.4 mmol), and lactate higher (p=0.054) with GUA (2.7 ± 1.0 mmol) versus P (2.2 ± 0.9 mmol). During the TT, %HRpeak, (96.3 ± 2.3 vs. 94.1± 2.2 bt/min) and %V̇O2max (93.3 ± 8.6 vs. 89.1 ± 7.6%) tended to be higher (p=0.053, p= 0.11) with GUA versus P, respectively. Mean power was 6% higher (p=0.012) (269.4 ± 47.1 vs. 253.8 ± 51.5 W) averaged over the TT and 4% more work accumulated (241.3 ± 39.9 vs. 232.1 ± 46.6 kJ) with GUA vs. P, respectively. Post-exercise strength loss was not attenuated with GUA (-5.6% ± 8.5) or CAF (-8.3% ± 9.4) compared to P (-10.3% ± 5.1). An order effect was not found (p=0.88) for total work across trial 1 (236.2 ± 42.4 kJ), trial 2 (233.6 ± 46.2 kJ), and trial 3 (235.9 ± 41.1 kJ). CONCLUSION: High intensity cycling performance following ingestion of GUA is improved compared to P but not different from CAF. The potential ergogenicity of GUA does not appear related to changes in substrate oxidation or the maintenance of muscle strength related to fatigue and merits further investigation. Supported in part by the Fulbright Scholar Fellowship Program.

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