A systems model approach to the ventilatory anaerobic threshold

Abstract

An analogue systems model of whole-body human bioenergetics predicts a change in kinetics of VO2 time series values as a result of exercise levels above an anaerobic threshold. Plotted VO2 results from exercising subjects appear to confirm this change. The purpose of this study is to describe the background to the systems model analogue of the anaerobic threshold and a test procedure devised to estimate this threshold. The estimate so obtained has the dual advantages of being based on model theory and of not being subject to the sort of ambient variations inherent in a single-test determination. A non-homogeneous group of eight subjects comprising a full replicate of a 2(3) factorial experimental design, with factors age, sex and training status, took part in the study. On one hand the results indicate acceptance of the systems model theory. On the other, the analogue threshold measure possesses corresponding properties to the conventional anaerobic threshold. It is higher for trained (155-214 W) than for untrained subjects (108-158 W), higher for males (149-214 W) than for females (108-170 W), and displays no evident interaction effects. Results for the VO2 time constant and for the work efficiency, display similar effects except for an interaction in the latter between age and training status. These experimental findings are regarded as confirmatory of the nature of the analogue threshold measure.

The critical power and related whole-body bioenergetic models

“…This ''elbow'' can be deduced from a breath-by-breath VO 2 plot and is the commencement of the VO 2 ''slow component'' (Gaesser and Poole 1996). In other words, the crossing of the anaerobic threshold can be modelled using the hydraulic model (Morton and Gass 1987). What happens is that at this delay point VO 2 dynamics change from monoexponential to bi-exponential as has since been empirically verified by Barstow and Mole (1991).…”

Oxygen deficit and blood lactate in prepubertal boys during exercise above the anaerobic threshold

“…The use of second-order functions for our data did not provide additional accuracy even for work intensities in the range above the anaerobic threshold. Admittedly, however, the increase in 702 values after the onset of a constant-load work seen in these boys did not appear to be that typically dual phase as Whipp and Wasserman [37] and Morton and Gass [21], for instance, demonstrated for constant-load ~?O2 values above the anaerobic threshold in adults. One property of the function we applied (which could also be formulated as X?O2 (ml/min/ kg) = fi0 (1 -131. e-N' t(min))) is that it does not necessarily pass through zero.…”

Validity of Dynamic Prediction Model for Oxygen Uptake during Supra Maximal Intermittent Load Exercise

“…O 2 dynamics modeling, and its characteristics to the workload have been explained (Pool, et al, 1994;Morton & Gregory, 1987;Miyamoto & Niizeki, 1990;Hughson, et al, 1991;Swanson & Hughson, 1988;Bell, et al, 1999;Cabrera, et al, 1999;Bahr, et al, 1992, Perrey, et al, 2002. Because the dose-response relationship between workload and V…”

“…O 2 are regarded as the first order system to the workload or energy demand (Pool, et al, 1996;Morton & Gregory, 1987;Miyamoto & Niizeki, 1990;Hughson, et al, 1987). Accordingly, the DP model was described as the following:…”

“…However, individual variation of approximately ±20 sec is known according to gender, age, muscular fiber composition and exercise habit in the time constant τ (Morton & Gregory, 1987;Barstow, et al, 1996;Perrey, et al, 2002). For applying the DP model to females, children, middle-aged and elderly people, individual estimation should be prepared for the time constant τ of V 4 O 2 dynamics.…”