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Caffeine Increases Work Done above Critical Power, but Not Anaerobic Work


Medicine & Science in Sports & Exercise: January 2018 - Volume 50 - Issue 1 - p 131–140
doi: 10.1249/MSS.0000000000001408
Applied Sciences

Purpose The assumption that the curvature constant (W′) of the power–duration relationship represents anaerobic work capacity is a controversial, unresolved question. We investigated if caffeine ingestion could increase total work done above critical power (CP), and if this would be accompanied by greater anaerobic energy expenditure and by an enhanced maintenance of maximal oxidative metabolic rate.

Methods Nine men (26.6 ± 5.3 yr, V˙O2max 40.6 ± 5.8 mL·kg−1·min−1) cycled until exhaustion at different exercise intensities on different days to determine the CP and W′. On separated days, participants cycled until exhaustion in the severe-intensity domain (136% ± 7% of CP) after ingesting either caffeine (5 mg·kg−1 body mass) or a placebo.

Results Time to exhaustion was 34% longer with caffeine compared with placebo, and this was accompanied by a greater work done above CP (23.7 ± 5.7 vs 17.5 ± 3.6 kJ; 130% ± 30% vs 95% ± 14% of W′, P < 0.01). Caffeine increased the aerobic energy expenditure (296.4 ± 91.0 vs 210.2 ± 71.9 kJ, P < 0.01), but not anaerobic lactic, anaerobic alactic, and total anaerobic (lactic + alactic) energy expenditure. The end values of heart rate and ventilation were higher with caffeine, but the V˙O2 end was similar between conditions and was not different from V˙O2max. Caffeine did not change time to reach V˙O2max but increased time maintained at V˙O2max (199.3 ± 105.9 vs 111.9 ± 87.1 s, P < 0.05).

Conclusions Caffeine increased total work done above CP, but this was not associated with greater anaerobic work. Rather, this was associated with a higher tolerance to maintain exercise at maximal oxidative metabolic rate.

1Sport Science Research Group, Department of Physical Education and Sports Science, Academic Center of Vitoria, Federal University of Pernambuco, Vitoria de Santo Antao, Pernambuco, BRAZIL; 2Institute of Sport, Exercise and Active Living, College of Sport and Exercise Science, Victoria University, Melbourne, Victoria, AUSTRALIA; 3School of Medical and Health Sciences, Edith Cowan University, Joondalup, Western Australia, AUSTRALIA; 4Endurance Performance Research Group (GEDAE-USP), School of Physical Education and Sport, University of São Paulo, Sao Paulo, BRAZIL; and 5Human Performance Research Group, Academic Department of Physical Education, Technological Federal University of Parana, Curitiba, Parana, BRAZIL

Address for correspondence: Adriano Eduardo Lima-Silva, Ph.D., Sport Science Research Group, Department of Physical Education and Sports Science, Academic Center of Vitoria, Federal University of Pernambuco, Alto do Reservatorio Street, Bela Vista, Vitoria de Santo Antao, Pernambuco, Brazil; E-mail:

Submitted for publication March 2017.

Accepted for publication August 2017.

© 2018 American College of Sports Medicine