Date of Award

2001

Degree Type

Thesis

Degree Name

Bachelor of Science Honours

Faculty

Faculty of Communications, Health and Science

First Advisor

Dr Angus Burnett

Abstract

Anecdotal reports from triathletes highlight the transition from cycling to running as the most difficult due to the change from non-weight carrying cycling activity to weight hearing running activity. The aim of this study was to examine the effects of prior cycling on activation of lower limb muscles in running during an Olympic distance triathlon. Ten elite level triathletes underwent two conditions; a 40krn ride followed by a 2km run and a 10km run followed by a 2km run, at their Olympic distance race pace. Testing was carried out in the field with at least one week between tests. EMG data from selected lower limb muscles in addition to accelerometer data to determine heel strike and toe-off were collected using a portable data logger. The vastus Iateralis (VL), vastus medialis (VM), rectus femoris (RF), biceps femoris (BF), gastrocnemius (GS) and gluteus maximus (GM) were analysed due to their ease of measurement via surface electrodes and because of their important role in both running and cycling. Data was processed to provide both the level of activation and time of activation variables for all the above mentioned muscles in both conditions. RMS processing of the EMG signal was used to evaluate the level of activation with the signal being normalised to each subject's maximum and represented as a percentage. Time of activation was calculated from the ensemble average of the six measured strides in each of the three sections of time using a 10% of maximum activation threshold detector. A repeated measures ANOVA with two within subject variables was used to evaluate the statistical significances (p<0.05) between the conditions and across time for each muscle for both the flight and stance phases. The results revealed increases in level and time of activation during stance for the VL and VM and are seemingly related to the change from a non-weight bearing activity (cycling) to a weight bearing activity (running). A greater demand on these muscles is assumed to occur for stability of the knee joint. During flight it is thought that increases in the level and time of activation of the VL and VM are due to the changes associated with the change from a concentric muscle contraction in cycling to stretch shortening cycle in running. The greater magnitude in both level and time of activation of the BF for the run/run condition are considered to be due to a greater level of fatigue of this muscle during 10km running compared with 40km cycling. Change in the time of activation of the RF may be due to the difficulties in flexing the hip in flight and its synergistic role with the VL and VM in extension of the knee.

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