Effects of carbohydrate and caffeine mouth rinsing on strength, muscular endurance and cognitive performance | Journal of the International Society of Sports Nutrition

Strength (1-RM) performance

Condition x gender interaction was not detected either for bench press (p = 0.55, η² = 0.14) or squat (p = 0.87, η² = 0.02) 1-RM performance. There was no significant main effect for condition in bench press (p = 0.24, η² = 0.12) and squat (p = 0.84, η² = 0.01) 1-RM. As expected, males lifted significantly higher than females in bench press (p = 0.01, η² = 0.79) and squat (p = 0.01, η² = 0.39) (Fig. 2 A and B).

Muscular endurance (40% of 1-RM) performance

Condition x gender x set interaction was not detected for squat (p = 0.29, η² = 0.11) and bench press (p = 0.74, η² = 0.15) muscular endurance performance. Gender x set (p = 0.82, η² = 0.01; p = 0.72, η² = 0.04) and gender x condition interaction was not significant (p = 0.12, η² = 0.27; p = 0.29, η² = 0.18) in squat and bench press, respectively. There was a main effect for set and gender for squat (p = 0.01, η² = 0.97; p = 0.01, η² = 0.73) and bench press (p = 0.01, η² = 0.88 p = 0.01, η² = 0.64), respectively; as expected, number of repetitions decreased from first to third set and males performed more repetitions than females in both squat and bench press muscular endurance test. Condition x set interaction was significant for squat (p = 0.03, η² = 0.48) but not for bench press (p = 0.39, η² = 0.20). Post-hoc analysis revealed that significantly more repetitions were performed in CHOCAF condition compared to PLA in the first set (p = 0.02) but there was no difference between CHOCAF and CAF (p = 0.33) or CHOCAF and CHO (p = 0.40). Further, no significant difference was detected at the second and third sets among conditions (p > 0.05) (Figs. 3 and 4).

Mean (SD) repetition numbers for squat over the three sets. CHO: carbohydrate mouth rinsing; CAF: caffeine mouth rinsing; CHOCAF: carbohydrate and caffeine mouth rinsing; PLA: placebo mouth rinsing; * significantly different from PLA

Mean (SD) repetition numbers for bench press exercises over the three sets. CHO: carbohydrate mouth rinsing; CAF: caffeine mouth rinsing; CHOCAF: carbohydrate and caffeine mouth rinsing; PLA: placebo mouth rinsing

ICC for squat 1-RM were 0.97 and 0.95, for muscular endurance, 0.92 and 0.94 in the first set; 0.90 and 0.91 in the second set; 0.87 and 0.90 in the third set in males and females, respectively. ICC results from bench press 1-RM were 0.98 and 0.96, for muscular endurance 0.93 and 0.90 in the first set; 0.88 and 0.93 in the second set; 0.87 and 0.90 in the third set in males and females, respectively.

Cognitive performance

Results from the flanker task for response accuracy showed no significant condition x gender x time interaction (p = 0.89, η² = 0.01) or main effects for gender (p = 0.55, η² = 0.14), condition (p = 0.19, η² = 0.17) and time (p = 0.22, η² = 0.03) for the congruent test. Response accuracy in the incongruent test also showed no significant condition x gender x time interaction (p = 0.81, η² = 0.01) or main effects for gender (p = 0.33, η² = 0.04), condition (p = 0.13, η² = 0.10) and time (p = 0.68, η² = 0.02).

With regards to reaction time in the congruent test, there was no significant condition x gender x time interaction (p = 0.31, η² = 0.08) or main effects for condition (p = 0.39, η² = 0.15) and time (p = 0.21, η² = 0.12). However, there was a main effect for gender (p = 0.04, η² = 0.43) with males reacting faster than females in pre-rinse and post-rinse time points regardless of mouth rinsing. Although there was no condition x gender x time interaction (p = 0.79, η² = 0.03) for incongruent test, the reaction time showed a significant condition x time interaction (p = 0.03, η² = 0.45). Post-hoc analysis revealed that significantly faster reaction time was performed in CHOCAF (p = 0.02) condition compared to PLA in the post-rinse, whereas there was no difference between CHOCAF and CAF (p = 0.28) or CHOCAF and CHO (p = 0.32), respectively. Similarly, there was also a main effect of gender (p = 0.01, η² = 0.69) for the reaction time assessed at the incongruent test, with males performing better than females in the pre- and post-rinse time in all mouth rinsing conditions. Lastly, there was no significant main effect for time (p = 0.78, η² = 0.14) and condition for reaction time in the incongruent test (p = 0.63, η² = 0.18) (Table 2). ICC values for cognitive performance parameters ranged between 0.91 to 0.97.

Heart rate, glucose, felt arousal, RPE

Heart rate did not show significant gender x condition x time (p = 0.45, η² = 0.04), gender x condition (p = 0.27, η² = 0.07), gender x time (p = 0.12, η² = 0.13) and condition x time (p = 0.14, η² = 0.10) interaction. As expected, there was a main effect for time (p = 0.01, η² = 0.94) with increasing HR later in exercise.

Similarly, for blood glucose there was no gender x condition x time (p = 0.58, η² = 0.02), gender x condition (p = 0.19, η² = 0.04), gender x time (p = 0.73, η² = 0.02) or condition x time (p = 0.33, η² = 0.05) interaction.

As expected RPE increased throughout exercise (main effect of time; p = 0.01, η² = 0.79), but there was no gender x condition x time (p = 0.18, η² = 0.07), gender x condition (p = 0.70, η² = 0.02), gender x time (p = 0.31, η² = 0.12) or condition x time (p = 0.50, η² = 0.17) interaction.

Felt arousal increased over time (p = 0.01, η² = 0.94) and there was also a condition x time interaction (p = 0.03, η² = 0.89). Post-hoc analysis revealed significantly higher felt arousal scores after mouth rinsing in CHOCAF (p = 0.01) and CAF (p = 0.02) condition compared to PLA. However, no significant differences were observed for felt arousal in CHOCAF (p = 0.10) and CAF (p = 0.16) conditions compared to CHO. Lastly, felt arousal did not differ between gender (p = 0.31) and condition (p = 0.08) (Table 3).