High-intensity interval training (HIIT) has numerous external load control variables. The management of these variables makes the physiological responses and performance presented by athletes also modify. The present study aimed to assess the activity of CK and LDH enzymes, performance and metabolic responses caused by two HIIT protocols above the maximum in male recreational runners. Fifteen recreational male runners performed two HIIT protocols in randomized order with multiple conditions: 1) H15 ( n = 15), with a HIIT protocol of 15:15 work-recovery duration, and 2) H30 ( n = 15) with a HIIT protocol of 30:30 work-recovery duration. Both protocols were performed at similar intensity (130% vV̇O 2 max ), one set until voluntary exhaustion. Blood samples were collected and used to capture the levels and activities of blood lactate (BLac: mmol⋅L –1 ), glucose (GLU: mg⋅dL –1 ), creatine kinase (CK: U⋅L –1 ), and lactate dehydrogenase (LDH: U⋅L –1 ). BLac and GLU were collected at pre, five, and ten minutes after the H15 and H30 protocols were performed. Blood samples were used to measure the activities of CK and LDH enzymes, which were verified 24 h before and 48 h after the protocols. The distance traveled (m), total time (s), and bouts performed (rep) were also registered. Significant differences between conditions H15 and H30 were observed in the bouts performed ( p = 0.001; ES = 1.19). Several statistical differences were found over time for BLac [pre vs. post 5 (both conditions: p = 0.001), pre vs. post 10 (both conditions: p = 0.001), and post 5 vs. post 10 (H30: p = 0.004)], CK [pre vs. post 24 (H15: p < 0.001; ES = 0.97 and H30: p = 0.001; ES = 0.74) post 24 vs. post 48 (H30: p = 0.03; ES = 0.56)], and LDH [pre vs. post24 (H15: p = 0.008; ES = 1.07 and H30: p = 0.022; ES = 0.85). No statistical differences between conditions were observed for any blood parameter. Thus, the volunteers exhibited equal performance in both protocols, which resulted in a similar physiological response. Despite this similarity, in comparison to H15, the H30 protocol presented lower CK activity post 48 and lactate levels after 10 min post protocol.

RESUMOO objetivo desse estudo foi avaliar o impacto da reposição hídrica com água de coco sobre o estado de hidratação e cardiovascular drift durante o exercício. Treze voluntários do sexo masculino realizaram três sessões de exercício em cicloergômetro, submetidos a formas distintas de hidratação: grupo sem água (SA); grupo com água (CA); e grupo água de coco (CAC). O estado de hidratação foi determinado por alterações percentuais na massa corporal (∆ %MC) e urina. A frequência cardíaca (FC) foi registrada para avaliar o cardiovascular drift. Houve um aumento significativo da desidratação no grupo SA (∆ %MC = -1,43 ± 0,15), comparado aos grupos CA (∆ %MC = -0,68 ± 0,15) e CAC (∆ % MC = -0,70 ± 0,19). O grupo SA demonstrou aumentos significativos da FC comparado aos outros grupos. Conclui-se que a água de coco favoreceu a hidratação e a redução da FC, evitando o cardiovascular drift, mas com impacto similar à água. Palavras-chave: Desidratação. Exercício. Frequência Cardíaca. ABSTRACTThe purpose of this study was to evaluate the impact of fluid replacement with coconut water on the hydration status and cardiovascular drift during exercise. Thirteen male volunteers performed three sessions of exercise in bicycle ergometer, submitted to different forms of fluid replacement: no water intake (NW) group; with water intake (WW) group; and with coconut water (WCW) group. Hydration status was determined by percentage body mass changes (∆ % BM) and urine. Heart rate (HR) was recorded to evaluate the cardiovascular drift. There was a significant increase of dehydration in the NW group(∆ % BM = -1.43 ± 0.15) compared with WW(∆ % BM = -0.68 ± 0.15) and WCW groups(∆ % BM = -0.70 ± 0.19). The NW group showed significant increases in HR compared to other groups. It was concluded that coconut water promotes hydration and HR reduction, preventing cardiovascular drift, but similar to water impact. Keywords: Dehydration. Exercise. Heart Rate. IntroduçãoO cardiovascular drift é caracterizado pelo aumento exacerbado da frequência cardíaca (FC), acompanhado pela redução do volume de ejeção (VE) e fluxo sanguíneo para o músculo exercitado em estado de desidratação 1 . Sabe-se que tal condição pode promover alterações na prescrição do exercício e desempenho 2 . Obviamente, a intensidade, a duração do exercício, a aclimatação ao calor e o estado de hidratação vão ditar a extensão do cardiovascular drift 3 . Assim, manter uma hidratação adequada é importante para que não seja desencadeado o cardiovascular drift durante as sessões de exercícios, especialmente em atletas sob situações de estresse térmico 4 . Porém, independentemente do estresse térmico e do atleta, sabe-se que a manutenção do estado de hidratação adequado é fundamental para a saúde e desempenho de todos os praticantes de exercício 5 . O ideal seria definir estratégias de hidratação, para evitar o estado de desidratação cumulativo e progressivo 6,7 . A utilização de marcadores simples como alteração

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