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Article Title

EFFECT OF HIGH INTENSITY INTERVAL TRAINING ON MAXIMAL FATTY ACID OXIDATION VERSUS STEADY STATE EXERCISE

Abstract

K. Beisel, E. Donahue, A. Kalafatis, K. Christison, C.L. Dumke, FACSM

University of Montana, Missoula, MT

Previous evidence suggests high intensity intervals and steady state exercise can enhance fat oxidation. These two stimuli have not been examined in the same exercise bout. PURPOSE: This study examines the effect of high intensity interval training (HIIT) on fatty acid oxidation compared to steady state at each individuals maximal fatty acid oxidation (MFAO). METHODS: Twelve fasted, uncaffeinated individuals (8 males, 4 females, average VO2max = 44.3±2.3 ml·kg-1·min-1, average age =23.8±0.8 years) underwent a randomized crossover design study with 2 trials; trial A included cycling for 60 minutes at MFAO workload (0.55±0.05 g·min-1; 58.6±1.1 % VO2max; 126.7±9.6 W) and trial B included 3 minute intervals at 90% and 30% of maximal workload during the first 30 minutes, and the last 30 minutes the subjects cycled at the MFAO workload. Total work was matched between the two trials. Heart rate (HR), respiratory exchange ratio (RER), rating of perceived exertion (RPE), absolute fat (FAO) and carbohydrate oxidation (CHOO) were recorded every 15 minutes, lactate and glucose taken every 30 minutes. Data was analyzed using a 2X2 repeated measures ANOVA and paired samples T-test for overall trial differences. RESULTS: There was a main effect of time on lactate (p=0.002), RPE (p=0.027), HR (45 min: 164.6±2.8 bpm vs. 60 min: 168.0±2.9 bpm, 45 min: 159.4±3.6 bpm vs. 60 min:159.8±4.6 bpm, p=0.028), and FAO (45 min: 0.55±0.05 g/min vs. 60 min: 0.66±0.06 g/min, 45 min: 0.62±0.04 g/min vs. 60 min: 0.63±0.04 g/min, p=0.044). There was a trial effect of RPE (45 min: 13.5±0.3 vs 60 min: 13.8±0.4, 45 min: 11.4±0.8 vs 60 min: 12.5±0.6, p =0.014), and sweat rate (0.91±0.07 L·min-1 vs 0.69±0.03 L·min-1, p=0.03) All listed values are trial A vs. trial B respectively. A trial by time interaction was found for lactate (pCONCLUSION:These data suggest as exercise endurance increases, MFAO is elevated. Despite elevated lactate in the HIIT trial FAO did not differ between trials. Despite matched work between trials, significant reductions in RPE, HR and SR, suggests subjects had reduced metabolic stress at MFAO workloads following HIIT.

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