- Title
- Physiological and mechanistic characteristics of all-out running using the critical speed concept
- Creator
- Kramer, Mark
- Subject
- Aerobic exercises
- Subject
- Physical fitness Running Exercise
- Date Issued
- 2019
- Date
- 2019
- Type
- Thesis
- Type
- Doctoral
- Type
- PhD
- Identifier
- http://hdl.handle.net/10948/40511
- Identifier
- vital:36178
- Description
- The studies described in this thesis, as far as could be ascertained, were the first to investigate the physiological and mechanistic characteristics of all-out running using the critical speed concept specifically applied to field-sport athletes. In the first study the oxygen uptake (𝑉̇𝑂2) kinetics of linear and shuttle all-out running were investigated. The 𝑉̇𝑂2 kinetic parameters were also related to parameters derived from a graded exercise test. No differences were observed in all 𝑉̇ 𝑂2 kinetic parameters between all-out linear and shuttle running, even though differences in all-out testing parameters were evident. The study was novel in that it was, as far as could be ascertained, the first to implement and investigate differences in 𝑉̇𝑂2 kinetics applied to all-out running. The second study investigated whether the parameters derived from all-out linear and shuttle running were representative of aerobic fitness, and the extent to which the all-out test (AOT) related to already established evaluations of aerobic fitness (e.g., graded exercise test [GXT] and the Yo-Yo intermittent recovery test [YYIR1]). It was also investigated whether the parameters from the AOTs could be used to predict the time to completion (tLIM) of shuttle-based performances. The outcomes of this study showed that both the linear and 50-m AOTs were indeed valid for the aerobic assessment of fitness by showing high correlations with maximal pulmonary oxygen uptake (𝑉̇𝑂2𝑚𝑎𝑥). Both the linear and 50-m AOT could therefore be used as surrogates for the evaluation of aerobic fitness. Interestingly, in terms of the tLIM prediction, the 25-m AOT showed the greatest utility. This study was novel on several fronts in that it was the first to: (1) investigate the physiological link between linear and shuttle AOTs and the GXT, (2) investigate the difference between AOTs and the YYIR1, and (3) investigate the application of the AOT methodology to field-based athletes such as rugby players. The third study investigated the energetic cost (EC) of locomotion as well as the metabolic power (𝑃̇) required to run at given speeds. The energetic approach provides a more robust evaluation of the differences between linear and shuttle running due to the all-out nature of the tests. Conventional methods of energy assessment often fall short due to the preclusion of a physiological steady-state, hence requiring more robust mathematical models to evaluate all-out running performance. The results of this study showed that differences between linear and shuttle AOTs are more likely neuromuscular as opposed to physiological. Peak EC and 𝑃̇ were significantly greater for shuttle running compared to linear running, showing clear non-linear increases with each successive increase in running speed. However, the mean EC and 𝑃̇ were not different, showing that all-out shuttle running ‘balances’ the lower running speeds (implying a lower physiological load compared to linear running) with the higher metabolic load imposed by the intense directional changes. This study was novel as it was, as far as could be ascertained, the first to apply the energetic approach to all-out running as well as investigate the differences in energetics between linear and shuttle AOTs. The fourth study provided a means by which the speed-time characteristics of all-out running could be objectively quantified. A novel bi-exponential model was applied to both the linear and shuttle speed-time curves and allowed various mechanistic aspects of the speed-time curve to be characterized. Conventional assessment of the AOT allows for the derivation of only two key parameters, namely critical speed (CS) and the finite distance achievable at speeds exceeding CS (D’). The application of the bi-exponential model expands the number of useful parameters that can be derived from an AOT to seven. The additional useful parameters include: maximum speed [𝑆𝑚𝑎𝑥], time to maximum speed [𝑡𝑐], amplitude of the difference between 𝑆𝑚𝑎𝑥 and CS [𝐴𝑑], curvature constant of the exponential decay [𝜏𝑑] and the asymptote of the exponential decay function [𝑆0], fatigue index showing the percent decline between 𝑆𝑚𝑎𝑥 and CS [FI%], and the finite capacity for running at speeds exceeding CS [D’; representing the area under the curve that is above CS]. The CS and D’ parameters derived from the bi-exponential model were not different to the CS and D’ parameters derived using the conventional method of analysis, thereby showing that the bi-exponential model is a valid means of assessing the curvature characteristics of the AOT, as well as providing additional information that cannot be gleaned from the traditional approach.
- Format
- xxvi, 236 leaves
- Format
- Publisher
- Nelson Mandela University
- Publisher
- Faculty of Health Sciences
- Language
- English
- Rights
- Nelson Mandela University
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