Padilla J, Kowalchuk JM, Taylor AW, Paterson DH

Language: English
References: 39
Page: 151-165
PDF size: 657.70 Kb.

ABSTRACT

Introduction. The kinetic analysis of the VO₂ on transient response during moderate (M_OD) and heavy (H_VY) intensity (M_OD+H_VY = S_UB) exercise was compared by using several common modelling strategies to assess the best one. Material and methods. We compared the parameter estimate for the phase 2 VO₂ time constant (ԏΦ₂VO₂) in older male adults (n = 9; 71 (± 5) yrs; mean (± sd)). Subjects performed an incremental ramp test (12 W•min^-1) to the limit of tolerance to determine VO_2peak and the estimated lactate threshold (θ_L). Constant load cycle exercise was performed at 50 W (M_OD) and work rates corresponding to 80% (M_OD) and 120% θ_L(H_VY). Each transition in work rate lasted 6 min and was preceded by 6 min cycling at a baseline of 20 W; transitions at each intensity were repeated 4 6 times. VO₂ was measured breath by breath. Data from each transition were filtered, interpolated to 1 s intervals and ensemble averaged to yield a single response profile for each subject and intensity. Responses were modelled by means of nonlinear regression techniques with one (1C; fitting window 0.3333 min from exercise onset to either end M_OD or phase 2 3 transition H_VY, two (2C) and three component (3C) (fitting window from start exercise to end exercise) exponential models. In addition to this, data were placed into discrete time bins of 10 s (10 s bins VO₂ data) to be modelled using 1C exponential model. Results. The 1C,4P_{0.3333 → 3 min} best fitted Φ₂VO₂ data for S_UB and allowed us to characterize ԏΦ₂VO₂. The Φ₂VO₂ data were physiologically best fitted with models 2C,7P_{BaseLine_Start to End exercise} for M_OD and 3C,10P_{BaseLine_Start to End} for H_VY and they allowed us an intra modelling characterization of the ԏΦ₂VO₂. These ԏΦ₂VO₂ were similar to each other in our old male volunteers (Overall mean ± SD: ԏ_{second-by-second VO2 data}= 46 ± 15 s, ԏ_{10-s bins VO2 data}= 43 ± 7 s).

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