Author(s): NULTY, C., DALTON, J., GRAMMENOU, M., Institution: SOUTH EAST TECHNOLOGICAL UNIVERSITY, Country: IRELAND, Abstract-ID: 2772

INTRODUCTION:
Youth athletes frequently report caffeine use as an ergogenic aid. The performance-enhancing effects of caffeine on maximal strength and power are well established, although delivery methods vary, including capsules, beverages, gels, and chewing gum. Caffeinated chewing gum has gained recent interest due to its rapid absorption through the buccal mucosa. However, the effects of different caffeine gum ingestion timings on resistance exercise performance in youth athletes have not yet been investigated.
METHODS:
Ten male League of Ireland academy soccer players (17.8±0.4 y, ≥1 y resistance training experience) took part in a single-blind, repeated measures crossover study. Each participant performed four full-body resistance training sessions between 18:00–20:00 h, separated by seven days. Session one served as a no-caffeine baseline, while the remaining three involved caffeinated chewing gum (4 mg·kg⁻¹) administered 0, 30, or 60 min before training in a randomised order; investigators were blinded to timing. Across all sessions, outcome measures included mean countermovement jump height (force plates), repetitions completed to failure at 90% 1-RM for bench press and back squat, and mean barbell velocity across all sets. Subjective sleepiness was assessed using the Karolinska Sleepiness Scale the morning following each session. Data were analysed by repeated measures ANOVA.
RESULTS:
Mean countermovement jump height (cm) differed between conditions (p = 0.014), with higher values observed in all caffeine conditions compared with no caffeine (No caffeine: 31.3±5.0 cm; 0 min: 31.8±5.5 cm; 30 min: 33.8±6.3 cm; 60 min: 33.1±5.6 cm). Back squat repetitions to failure at 90% 1-RM were greater following caffeine ingestion (0 min: 11±3; 30 min: 10±2; 60 min: 10±4 repetitions) compared with no caffeine (7±2 repetitions; p = 0.035), with no differences between caffeine timing conditions. Similarly, bench press repetitions to failure at 90% 1-RM were greater following caffeine ingestion (0 min: 5±2; 30 min: 6±2; 60 min: 5±2 repetitions) compared with no caffeine (4±2 repetitions; p = 0.004), with no differences between caffeine timing conditions. Mean barbell velocity (m·s⁻¹) decreased with increasing load in both exercises (back squat: 0.66 ± 0.01 at 60%, 0.56 ± 0.02 at 75%, 0.46 ± 0.01 at 90% 1-RM; bench press: 0.75 ± 0.01 at 60%, 0.53 ± 0.03 at 75%, 0.34 ± 0.01 at 90% 1-RM), with no effect of caffeine timing at any load (all p>0.05). Next-morning subjective sleepiness, assessed using the Karolinska Sleepiness Scale (AU), did not differ between conditions (No caffeine: 6.7±1.7; 0 min: 4.8±1.9; 30 min: 5.3±1.9; 60 min: 5.2±1.5 AU p=0.13).
CONCLUSION:
Caffeinated chewing gum enhances high-load muscular endurance and countermovement jump performance during a typical evening academy resistance training session in youth athletes, independent of ingestion timing. Barbell velocity was unaffected at any load, suggesting caffeine improved fatigue resistance rather than movement speed.