Title

ACUTE EFFECT OF INTENSITY FLUCTUATION ON ENERGY OUTPUT AND SUBSTRATE UTILIZATION

Authors

Authors

J. Kang; G. T. Mangine; N. A. Ratamess; A. D. Faigenbaum;J. R. Hoffman

Comments

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Abbreviated Journal Title

J. Strength Cond. Res.

Keywords

intensity fluctuation; oxygen uptake; respiratory exchanged ratio; substrate oxidation; blood lactate concentration; recovery; POSTEXERCISE OXYGEN-CONSUMPTION; INTERVAL TRAINING INCREASES; INTERMITTENT EXERCISE; LIPID OXIDATION; FAT OXIDATION; RESPONSES; WOMEN; EXPENDITURE; METABOLISM; CYCLISTS; Sport Sciences

Abstract

Exercise routines in which intensity fluctuates, such as Spinning and Treading, are gaining in popularity in fitness industry. However, literature on how this dynamic protocol may affect the exercise metabolism is lacking. The present investigation was undertaken to examine the effect of intensity fluctuation and its magnitude on oxygen uptake and substrate utilization during exercise and recovery. Fifteen men and 15 women were randomly assigned into 1 of the 3 groups consisting of 10 participants of equal gender. Each group performed one of the three 30-minute exercise protocols that yielded the same total power output: (a) cycling at a constant power output of 75 W (P1), (b) cycling with power output alternating between 50 and 100 W every 5 minutes (P2), and (c) cycling with power output alternating between 25 and 125 W every 5 minutes (P3). Each exercise session was followed by a 25-minute recovery. Oxygen uptake ((V) over dotO(2)), carbon dioxide production ((V) over dotO(2)), and respiratory exchanged ratio were measured at rest and during exercise and recovery. Rates of carbohydrate (COX) and fat oxidation (FOX) were calculated based on (V) over dotO(2) and (V) over dotO(2) using the stoichiometric equations. (V) over dotO(2) in ml.kg(-1).min(-1) did not differ across the 3 protocols during exercise, but was higher (p <= 0.05) in P2 (4.92 +/- 0.51) or P3 (4.94 +/- 0.24) than P1 (4.17 +/- 0.19) during recovery. COX in mg.kg(-1).min(-1) was higher (p <= 0.05) in P3 (17.68 +/- 1.30) than in P1 (12.22 +/- 1.55) or P2 (12.06 +/- 1.47) during exercise and higher in P3 (4.17 +/- 0.45) than in P1 (2.60 +/- 0.36) during recovery. FOX in mg.kg(-1).min(-1) was lower (p <= 0.05) in P3 (2.61 +/- 0.47) than in P1 (4.30 +/- 0.60) or P2 (4.22 > 0.47) during exercise but remained similar across the 3 protocols during recovery. These data indicate that intensity fluctuation of sufficient magnitude can alter exercise metabolism independent of the total power output or overall intensity. The 2 variable intensity protocols used in the study (i. e., P2 and P3) are equally effective in augmenting postexercise (V) over dotO(2), but the protocol with a greater magnitude of fluctuation also elicits greater COX coupled with reduced FOX during exercise.

Journal Title

Journal of Strength and Conditioning Research

Volume

28

Issue/Number

8

Publication Date

1-1-2014

Document Type

Article

Language

English

First Page

2136

Last Page

2144

WOS Identifier

WOS:000340206400008

ISSN

1064-8011

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