Caffeine decreases neuromuscular fatigue in the lumbar muscles – a randomized blind study

Abstract

ABSTRACTBackgroundErgogenic evidence for caffeine is robust in sports and isolated limb tasks. Our objective was to evaluate a possible ergogenic effect on postural muscles, still unknown, through the Biering-Sørensen’s lumbar extension test.MethodsA double-blind, controlled placebo, crossover study. Fifty-one healthy, physically inactive male subjects (18-25 years) with average body mass (BMI 18.5 – 24.9 kg/m2) were recruited. The subjects received oral caffeine (6 mg/kg) and saline (0.3%) in two cross-evaluations separated by one week. The primary outcome was the time in the Biering-Sørensen test after 1 hour of treatment. The secondary outcomes were peak lumbar extension force, rating of perceived exertion, EMG’s median frequency and muscle recruitment of multifidus spinae and transversalis/interne oblique muscles, and cardiovascular variables (heart rate and blood pressure).Results27 subjects were blindly treated with caffeine and saline. Caffeine was ergogenic during the Biering-Sørensen test. It increased lumbar extension time (d = 0.34, P<0.05), but not peak force. The perception of effort decreased with caffeine (d = 0.37, P<0.05). Caffeine increased muscle stimulation frequency (P<0.05) and recruitment (η2 = 0.49, P<0.05) of multifidus spinae. In the transversalis/interne oblique muscles, caffeine increased the median frequency η2 = 0.13, P<0.05) and the distribution of higher frequencies (P<0.05). Caffeine also increased muscle recruitment in the transversalis/interne oblique muscles η2 = 0.13, P<0.05) Tachycardia and increased blood pressure at the lumbar test were higher in the caffeine condition (P< 0.05).ConclusionsOur results show that caffeine is ergogenic for postural muscles. Decreased RPE and improved muscle activity suggest central mechanisms of caffeine.Trial registrationUTN U1111-1234-2079.BULLET POINTSCaffeine increases the extension time of the lumbar spine in the Biering-Sørensen test.Caffeine decreases perceived exertion during the Biering-Sørensen test.Caffeine increases muscle stimulation and recruitment of the multifidus spinae during the Biering-Sørensen test.Caffeine increases muscle stimulation of the transversalis/interne oblique muscles during the Biering-Sørensen test.