Year

2022

Degree Name

Doctor of Philosophy

Department

School of Medicine

Abstract

The purpose of this thesis was to investigate and quantify how eccentric (ECC) cycling influences the modulation of the underlying neuromotor mechanisms.

Study one investigated post-exercise changes in global corticospinal excitability (CSE) by eliciting a motor-evoked potential in a non-exercised upper limb muscle following concentric (CON) and ECC cycling. No significant differences in global CSE were shown between CON and ECC cycling. However, individual responses of global CSE varied between cycling modes and time points. The variability likely related unfamiliarity with non-specific workload prescription of, and limited controllability of muscle actions during, ECC cycling.

Study two addressed the controllability of ECC cycling through modification of a semi-recumbent ECC cycle ergometer to isolate ECC contractions during ECC cycling. The regenerative braking capacity of the built-in electric servo motors were programmed to function as a ‘trip’ mechanism, isolating ECC muscle actions to the opposing (OPP) phase of ECC cycling. Laboratory testing demonstrated the effectiveness of the ‘trip’ mechanism in isolating ECC muscle actions during ECC cycling. These results support using this modified ECC cycle ergometer among unfamiliarised participants performing novel ECC cycling.

Study three developed a reliable peak ECC resistance test specific to semi-recumbent ECC cycling. Participants performed six peak ECC torque protocol (PETP) tests on an isokinetic dynamometer in a replicable semi-recumbent ECC cycling position. The PETP test was reliable in determining peak torque (ICC > 0.90) and peak power output (ICC > 0.90) during a single session. The PETP test is the first known maximal test specifically developed for ECC cycling and could be used to more effectively prescribe ECC cycling workloads, due to specificity of measurement compared within commonly used CON cycling tests.

Study four aimed to develop a single-session familiarisation protocol for submaximal ECC cycling, based on naïve participants producing reliable muscle activation patterns at a PETP test-prescribed power output. Participants produced reliable (ICC > 0.50) and lowly variable muscle activation patterns of the primary active muscles, within a single 15 min ECC cycling session. Overall, naïve participants were capable of becoming familiarised with ECC cycling during a single 15 min session.

Study five implemented the newly developed methods, described in studies two, three and four, to investigate modulation of neuromotor excitability in an exercised (i.e., local) and non-exercised (i.e., global) muscle following ECC cycling. The main result showed that neuromotor excitability is differentially modulated by ECC cycling. Specifically, global neuromotor excitability increases following ECC cycling. Alternatively, local neuromotor excitability decreases, likely due to spinal inhibition. The outcomes of this study provide evidence of active neural coupling between the upper and lower limbs during ECC cycling that could be beneficial for neurorehabilitation.

To conclude, this thesis presents new knowledge about the modulation of neuromotor mechanisms following ECC cycling and provides researchers and clinicians new methods with which to control ECC cycling and therefore, improve the application of future findings.

FoR codes (2008)

1106 HUMAN MOVEMENT AND SPORTS SCIENCE

Download

Share

COinS
 

Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.