Caffeine Supplementation do Not Prevent Induced Acute Strength Loss By Concurrent Exercise

The caffeine ingestion can delay neuromuscular fatigue and performance because it acts on the central nervous system affecting the rating of perceived exertion and propagation of neural signals between the brain and the neuromuscular junction. Furthermore, it is known that concurrent exercise (aerobic highintensity intermittent + strength exercises) may have a loss on the long-term development of strength. However, in the best of our knowledge, no data was found in literature investigating the effects of caffeine in concurrent exercise. Thus, the purpose is to determine the effects of caffeine supplementation on strength performance in concurrent exercise and, metabolic and inflammatory response. The method comprised in seven active males (27 ± 3 years old, 172 ± 0,06 cm, 70 ± 5 kg) undergoing in 3 interventions at least 7 days apart in a randomized, doubleblind, placebo-controlled, balanced trial. Participants ingested the placebo or caffeine (5 mg kg(-1) BW) 30 minutes before performing the strength exercises. Participants underwent three randomized session: 1) four sets of half-squat strength exercise until exhaustion at 80% 1MR (S), 2-3) 5-kilometer run in highintensity intermittent aerobic exercise at maximal intensity (Vmax) with the ingestion of placebo (P) or caffeine (C) before the strength exercise. The blood samples were collected at rest and immediately after the S, P and, C conditions and fatigue markers were analyzed. Data were analyzed using the Statistical Package for Social Sciences 18.0. The results showed a larger Uglucose in S than P condition (p = 0.040). There was a main effect of Ulactate (p < 0.001), with larger Ulactate in the S than in P and C conditions. There was no effect for UNEFA and UIL-6. The maximum number of repetitions was a main effect for the S condition (p = 0.002) with higher number of repetitions performed in S condition compared to P and C conditions (p < 0.001 for all comparison). Moreover, there was an interaction between condition and sets (p < 0.001), with higher maximum number of repetitions performed in set 1 in S condition than in set 1 in P and C conditions (p<0.001 for all comparison). Also a higher number in set 2 in S condition than during set 2 in P (p = 0.036) and C (9 = 0.048) conditions. The conclusion of this was that the caffeine supplementation did not improve strength performance in concurrent exercise in active males.

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