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

Silveira Rodrigo; Andrade-Souza, Victor Amorim; Arcoverde, Lucyana; Tomazini, Fabiano; Sansonio, André; Bishop, David John; Bertuzzi, Romulo; Lima-Silva, Adriano Eduardo
Medicine & Science in Sports & Exercise: Post Acceptance: August 21, 2017
doi: 10.1249/MSS.0000000000001408
Original Investigations: PDF Only

ABSTRACTPurposeThe 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.MethodsNine men (26.6 ± 5.3 years, 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. ResultsTime to exhaustion was 34% longer with caffeine compared to 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). ConclusionsCaffeine 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.

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 years, 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 to 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.

Address for correspondence: Adriano Eduardo Lima-Silva, Sports 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. ZIP CODE: 55608680. Phone/fax number: +55 81 35233351. E-mail address: adrianosilva@usp.br

Disclosure statement of funding received: No financial support was received. The authors declare no conflict of interest.

Accepted for Publication: 11 August 2017

© 2017 American College of Sports Medicine