Acute Co-Ingestion of Caffeine and Sodium Bicarbonate on Muscular Endurance Performance

Abstract

Background: Caffeine and sodium bicarbonate individually enhance muscular endurance by delaying fatigue, but their combined effects have scarcely been studied. Objectives: This study aimed to evaluate the acute effects of co-ingesting caffeine and sodium bicarbonate on muscular endurance at different loads in bench press and back squat exercises. Methods: Twenty-seven recreationally trained participants (female/male: 14/14; age: 23 ± 3.6 years) were randomized to four conditions in a double-blind, crossover design: (a) sodium bicarbonate and caffeine (NaHCO₃ + CAF); (b) sodium bicarbonate (NaHCO₃); (c) caffeine (CAF); (d) placebo (PLA); ingesting 0.3 g/kg NaHCO₃, 3 mg/kg caffeine or placebo (maltodextrin). Participants performed two muscle endurance tests on bench press and back squat exercises at 65% and 85% 1RM, performing as many repetitions as possible in one set until task failure. Results: CAF increased the number of repetitions (p < 0.001; η_p² = 0.111), mean velocity (V_mean, p = 0.043, η_p² = 0.16), and mean power output (W_mean, p = 0.034, η_p² = 0.15) compared to placebo. These effects were observed in back squat exercise at 65%1RM in V_mean (3.7%, p = 0.050, g = 1.144) and W_mean (5.2%, p = 0.047, g = 0.986) and at 85%1RM in V_mean (5.4%, p = 0.043, g = 0.22) and W_mean (5.5%, p = 0.050, g = 0.25). No ergogenic effects were found in NaHCO₃ + CAF) or NaHCO₃ conditions. Conclusions: CAF increased muscular endurance performance in male and female participants by increasing the number of repetitions, mean velocity, and power output; however, when NaHCO₃ was ingested, these effects were not detected.

Keywords: caffeine; ergogenic aids; load-power relationship; resistance exercise; sodium bicarbonate; sport nutrition.

Figure 1

Experimental protocol.

Figure 2

Number of repetitions performed after the four supplementation protocols at different intensities. Note: Number of repetitions performed in the bench press at 65%1RM in males (a) and females (b) and at 85%1RM in males (c) and females (d); and back squat exercise at 65%1RM in males (e) and females (f) and at 85%1RM in males (g) and females (h). * p < 0.05 CAF compared to PLA in male participants; # p < 0.05 CAF compared to PLA in female participants. Abbreviations: CAF, caffeine; NaHCO₃, sodium bicarbonate; NaHCO₃ + CAF, sodium bicarbonate plus caffeine; PLA, placebo.

Figure 3

Mean velocity (V_mean) performed after the four supplementation protocols at different intensities. Note: V_mean performed in the bench press at 65%1RM in males (a) and females (b) and at 85%1RM in males (c) and females (d); and back squat exercise at 65%1RM in males (e) and females (f) and at 85%1RM in males (g) and females (h). * p < 0.05 CAF compared to PLA in male participants; # p < 0.05 CAF compared to PLA in female participants. Abbreviations: CAF, caffeine; NaHCO₃, sodium bicarbonate; NaHCO₃ + CAF, sodium bicarbonate plus caffeine; PLA, placebo.

Figure 4

Mean power output (W_mean) performed after the four supplementation protocols at different intensities. Note: W_mean performed in the bench press at 65%1RM in males (a) and females (b) and at 85%1RM in males (c) and females (d); and back squat exercise at 65%1RM in males (e) and females (f) and at 85%1RM in males (g) and females (h). * p < 0.05 CAF compared to PLA in male participants; # p < 0.05 CAF compared to PLA in female participants. Abbreviations: CAF, caffeine; NaHCO₃, sodium bicarbonate; NaHCO₃ + CAF, sodium bicarbonate plus caffeine; PLA, placebo.