Author(s): MONTALVO ALONSO, J.J., DEL VAL MANZANO, M., FERRAGUT, C., VALADÉS, D., PÉREZ-LÓPEZ, A., Institution: UNIVERSIDAD DE ALCALÁ, Country: SPAIN, Abstract-ID: 2071

INTRODUCTION:
The ergogenic effect of caffeine on sports performance has been analyzed in numerous
studies, becoming one of the sports supplements with the greatest proven benefits. Scientific
evidence shows that acute caffeine intake improves muscle strength, power and endurance in
upper and lower body exercises. However, in these studies, female participants are
underrepresented, and consequently, we have limited evidence about the effect of caffeine on
women. Moreover, the sex differences in the ergogenic effect of caffeine on muscular
strength, power, and endurance performance have been scarcely explored.
METHODS:
Seventy-six resistance-trained participants (male/female: 38/38; age: 23±3 years; resistance
training experience: 2.7±2.0 years; 1RM/kg bench press: >1.0; 1RM/kg back squat: <1.2)
participated in a double-blind, placebo-controlled, cross-over and randomized study.
Participants were provided with either 3 mg/kg of body mass of caffeine or a placebo, and sixty
minutes after the ingestion, they performed muscular strength and power assessment for the
bench press and back squat exercises at 25%, 50%, 75%, and 90% 1-repetition-maximum
(1RM), performing 3, 2, 1 and 1 repetitions, respectively. Muscular endurance was then
assessed for both exercises at 65% 1RM, performing one set until task failure for each exercise.
RESULTS:
Compared to placebo, caffeine improved mean and peak velocity and power output (ANOVA
effect, P<0.001), but no supplement by sex effect was found for any of these variables.
Nonetheless, supplement by exercise type effect in Vmean (P=0.049). Caffeine increased Vmean
in the back squat exercise in males and females at 50%1RM (males and females, 4.5% and
4.6%, P=0.001), 75%1RM (5.2% and 5.7%, P=0.001) and 90%1RM (7.9% and 7.8%, P<
0.030). Similarly, in Wmean, supplement by exercise type by load was found (P = 0.045),
caffeine increased in the back squat exercise in males and females at 50%1RM (5.3% and
4.6%, P < 0.040), 75%1RM (5.7% and 5.5%, P<0.001) and 90%1RM (8.5% and 6.5%,
P<0.028) compared to placebo. In muscular endurance, a supplement effect was detected in
the number of repetitions (reps), Vmean, Wmean and Wpeak (ANOVA, P < 0.001). However, no
supplement by sex effect was found for any of these variables.
CONCLUSION:
Low doses of caffeine (3 mg/kg) cause a similar ergogenic effect on muscular strength, power
and endurance performance in upper- and lower-body exercises between male and female
resistance-trained participants. Moreover, caffeines effect was more pronounced at moderate-
high loads (>50%1RM) and according to muscle size groups (back squat vs. bench press) but
irrespective to sex, which indirectly reinforced the idea of the central mechanism of action of
caffeine.