Year

2015

Degree Name

Master of Science - Research

Department

School of Medicine

Abstract

Background: In triathlon, the ability to run efficiently after cycling is considered paramount to an athlete’s performance. However, it has been previously reported that when triathletes transition between cycling and running, termed the cycle-run transition, they are likely to experience noticeable levels of movement impairment and muscle activation disturbances. Previous research has specifically noted that prior cycling has a negative impact on neuromuscular control and increases the oxygen cost of subsequent running. Alternatively, research specifically observing the effects of prior exercise have reported a ‘speeding’ in oxygen uptake (V̇ O2) during the early phase of subsequent exercise. Interestingly, there has been a limited analysis of the early phase response of muscle recruitment activity and metabolic variables during triathlon the cycle-run transition. However, research has suggested a potential link between cycling-influenced change to muscle recruitment patterns and an increase in the metabolic cost of subsequent running. There is also evidence to suggest that changes to muscle recruitment patterns do reflect changes to the metabolic cost during exercise, however when looking at triathlon, a potential link is not well established.

Objective: Therefore, the overall aim of this study was to investigate the muscular recruitment patterns and physiological response that occurs following prior exercise, in the form of cycling, on the subsequent early phase of running compared to isolated running among a cohort of trained triathletes.

Design: Fifteen (n=15) elite level triathletes (25.3±6.9 years) were successfully recruited for the study. Following a prior familiarisation session, all athletes were required to complete a highly repeatable, non-fatiguing exercise protocol comprised of a 10 min isolated run (IR), 30 min of seated rest, then a 20 min varied cadence cycle, followed by a 30 min transition run (C-R). All running exercises were completed on an indoor laboratory treadmill at an individually self-selected speed. Cycling was carried out using a stationary trainer with athletes mounting their personal bikes to the apparatus. During the IR and C-R breath-by-breath V̇ O2 was recorded using a metabolic gas analysis and beat-by-beat heart rate was collected using a heart rate monitor strap. Muscle recruitment activity was measured at eight different muscle sites on the left leg using electromyography.

Results: Individual and group mean steady state V̇ O2 were not different (p=0.44) between the IR (34.6±4.9 ml.kg-1.min-1) and C-R (35.2±5.1 ml.kg-1.min-1) conditions. Steady state HR values for the IR (139±12 bpm) and C-R (145±15 bpm) conditions were also not different. Respective halftime and mean response time values for V̇ O2 were significantly different between the IR and C-R conditions (p

Conclusions: This study demonstrated that among elite level triathletes, prior cycling exercise does not adversely influence V̇ O2 or heart rate at steady state during subsequent running, compared to isolated running. However, during the early phase response, prior cycling exercise does appear to influence the k and MRT, suggesting a potential ‘speeding’ effect on V̇ O2 during the C-R condition compared to the IR. Our results also suggest that subsequent running muscle recruitment activity is not heavily affected by prior moderate intensity cycling, in spite of increased variability. Further, the absence of significant change to muscle recruitment activity, compared with V̇ O2 and HR values during the early periods of running after cycling suggests that during moderate intensity exercise, there exists no meaningful link between neuromuscular and physiological variables until steady state is achieved. Additional research is however necessary to improve the understanding of the effects of prior cycling on subsequent running performance at higher exercise intensities, that are more likely reflective of the competitive demands of triathlon.

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