Caffeine ingestion attenuates diurnal variation of lower-body ballistic performance in resistance-trained women

ABSTRACT

The present study investigates the effect of an acute intake of caffeine on the diurnal variation of neuromuscular performance in resistance-trained women. A total of 15 resistance-trained women participated in the current triple-blind, placebo-controlled, crossover experimental study. We assessed neuromuscular performance (i.e. ballistic (countermovement jump [CMJ] height and bench press throw [BPT] peak velocity), maximal strength (squat and bench press [BP] one-repetition maximum [1RM]), and strength-endurance [average velocity of the set during squat and number of repetitions-to-failure in BP]) four times at within 7 days. The participants ingested an acute dose of caffeine (3 mg/kg) or a placebo at 9–11 am and/or 17–19 pm. CMJ height (P = .016) and BP peak velocity (P = .012) were higher in the afternoon than in the morning. Compared to placebo, caffeine intake increased CMJ height by 3.1% in the morning and 1.6% in the afternoon (P = .035), but it had no effect on BPT peak velocity (P = .381). Maximal strength and strength-endurance performances were not affected by the time-of-day or caffeine intake (all P > .3). No significant interaction (time-of-day x substance) was observed in any of the above-mentioned outcomes (all P > .1). In conclusion, an acute dose of caffeine in the morning was effective to restore CMJ performance to levels found in the afternoon, while this effect was not observed neither in BPTpeak velocity nor in lower- and upper-body maximal strength and strength-endurance performance. Moreover, lower- and upper-body ballistic performance were greater in the afternoon than in the morning in resistance-trained women, while the acute intake of caffeine was only effective to increase CMJ height.

Highlights

• Ballistic performance is probably higher in the afternoon than in the morning in resistance-trained women.

• An acute intake of caffeine is effective to increase countermovement jump performance.

• The ingestion of an acute dose of caffeine in the morning restored countermovement jump performance to levels found in the afternoon.

KEYWORDS:

• Musculoskeletal
• resistance
• strength
• training
• physiology

Acknowledgments

We are grateful to the participants of this study for having performed maximal efforts until muscular fatigue. This study was part of a Ph.D. thesis conducted at the University of Granada, Spain.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The study was supported by the University of Granada Plan Propio de Investigación 2016 (Excellence actions: Unit of Excellence on Exercise and Health [UCEES]), by the Junta de Andalucía, Consejería de Conocimiento, Investigación y Universidades, by the European Regional Development Fund (ERDF), ref. SOMM17/6107/UGR and by Redes Temáticas de Investigación Cooperativa RETIC grant Red SAMID RD16/0022.