Author Identifiers

ORCID: 0000-0003-2050-7186

Date of Award

2018

Degree Type

Thesis

Degree Name

Master of Science (Sports Science)

School

School of Medical and Health Sciences

First Advisor

Dr Jodie L Cochrane Wilkie

Second Advisor

Professor Anthony J Blazevich

Third Advisor

Associate Professor Chris R Abbiss

Field of Research Code

110601, 110602

Abstract

The multidisciplinary sport of triathlon provides a good model for testing whether a secondary task can be negatively affected by a preceding task, especially when movement patterns are different. Research suggests that cycling exercise impairs subsequent running performance by altering a runner’s economy and various mechanics (or technique-related) parameters. However, this is not an unambiguous finding. Furthermore, movement patterns are self-optimised during cycling and running to minimise the energy cost, yet the relationship between running mechanics and economy are not clear when different locomotor tasks are performed in succession

Two research studies were conducted with the focus of describing and better understanding the influence of a prior cycle exercise on the economy and mechanics of running in 17, trained male triathletes. The first study aimed to investigate the differences in measures of running economy and other physiological and perceptual variables following a 60-min, simulated Olympic-distance cycling bout, compared to when cycling was not performed prior to running. Measures of running economy (i.e. aerobic energy cost, oxygen cost and the rate of oxygen consumption) and all other physiological (e.g. heart and ventilation rates) and perceptual descriptors (perception of exertion and effort) were significantly impaired (p < 0.05) following the cycling bout. It is likely that the generation of both peripheral and central fatigue during cycling contributed to these impairments, yet further investigation is required to enhance our understanding of the influence of a prior task on perceptual (or anticipatory) responses influencing the pacing strategies of subsequent running. Strong agreement existed between the three methods of calculating running economy, yet the number of participants identified as having an impaired running economy differed depending on the method used. Different conclusions may therefore be drawn as to the influence of prior cycling on subsequent running depending on the calculation method of economy used. It is recommended that aerobic energy cost be calculated to provide more specific information regarding the substrate utilisation, which is not accounted for when calculating oxygen cost and V̇ O2.

The second study aimed to examine the differences in three-dimensional mechanical variables when running following a 60-min cycle exercise, compared to running without prior cycling, and to assess the relationship between differences in running mechanical variables and running economy. Findings indicated significant differences (p < 0.05) between pre-and post-cycling running stride parameters (i.e. velocity, flight time, stride length, vertical oscillation of the centre of mass and landing of the foot relative to the centre of mass), lower body joint kinematics (knee flexion during the support and swing phases, and anterior pelvic tilt) and joint extension power of the knee. Interestingly majority of these differences replicated profiles typically associated with economical running techniques. Parameters of the ankle, hip, pelvis and trunk remained unchanged. The changes in flight time, knee flexion during the support phase and the lateral pelvic flexion were significantly associated with the changes in running economy, yet large individual differences existed. Runners identified in Study One as having an improved economy following cycling (n = 6), indicted a greater change in mechanical variables (although not statistically significant). Therefore, it is suggested that triathletes either self-optimised their kinematics in an attempt to maintain movement economy following cycling, or as an effective pacing strategy decreased their running velocity.

The results of this thesis confirmed a significant influence of a prior locomotor task (i.e. a cycling exercise) on the energy cost, perceptual responses and the biomechanics of a subsequent locomotor task (i.e. running) in most trained triathletes. However, 35% of the study cohort demonstrated an ability to run with better economy and presented with a trend towards lower increases in measured physiological and perceptual parameters. A single approach to identify an economical running technique, particularly when performed in immediate succession following a prior task, is therefore not adequate. Maintaining pre-cycling running mechanics might not be a main factor related to triathlon running performance as athletes appeared to self-optimise and adapt their running mechanics during the post-cycling condition, which was different to the pre-cycling, non-fatigued condition. It is recommended to make physiological testing procedures more task specific by including a cycling bout prior to running to assess and monitor individual adaptations, and to assist coaches in developing training to optimise this transition between cycling and running.

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