Energy system contribution and VO2 response in track running

This thesis consists of six experimental studies from three separate data collection periods. The first two studies dealt respectively with the reliability and validity of the portable V&O2 measuring system (Cosmed K4b) and validity of the exercise protocol, both of which were utilised during the subsequent studies. Three of the final four studies dealt with quantifying the relative energy system contribution to track running events between 100-m and 3000-m using measures recorded during actual track running events. The final study examined the on-transient V&O2 response to middledistance 800-m, 1500-m and 3000-m track running events. Study 1 reported on the validity and reliability of a Cosmed K4b portable gas analysis system. Comparison of Cosmed K4b and Metabolic cart measurements revealed significantly (p<0.05) increased Cosmed system values of V&O2, V&CO2, FECO2 (except FECO2 at 10min) and lower values of FEO2 for each run duration (1, 3 and 10 min). Linear regression equations to predict metabolic cart results from Cosmed values were, respectively; cart V&O2 = 0.926 ⋅ Cosmed V&O2 – 0.227 (r = 0.84) and cart V&CO2 = 1.057 ⋅ Cosmed V&CO2 – 0.606 (r = 0.92). Bland –Altman plots and comparison of the test-retest Cosmed measurements revealed that the K4b system showed good repeatability of measurement for measures of V&E, V&O2 and V&CO2, particularly for 10 and 3 min tests (ICC = 0.7 – 0.9, p<0.05). Thus, while the Cosmed K4b portable gas analysis system recorded consistently higher V&O2 and V&CO2 measurements in comparison to a metabolic cart, satisfactory test-retest reliability of the system was demonstrated. Pr r e e f ffa a c c e e iii Study 2 reported on the comparison between a conventional linear method and a proposed non-linear regression (NLR) method of determining the accumulated oxygen deficit (AOD). No significant difference (p>0.05) was noted for the calculation of AOD between the linear regression (sub maximal) and NLR (supramaximal) methodologies. However, a weak, (but significant) correlation (r = -0.40, p<0.05) was obtained and the observed intra-subject difference in the calculated AOD was large (30.8 – 80.6 mlkg). As a result, it was concluded that the use of a NLR technique with supra maximal exercise to obtain a measure of AOD was not comparable to the conventional linear V&O2 – velocity technique. Hence, it was concluded that the conventional, linear measure remained the preferred option for the measurement of AOD. Results from Studies 3, 4, and 5 respectively determined the aerobic – anaerobic energy system contribution to track running events of 100-m through to 3000-m. Results from Study 3 indicated the aerobic – anaerobic energy system contribution to 1500-m (for males and females) as 77% 23% and 86% 14%, and for 3000-m as 86% 14% and 94% 6% respectively (AOD method). Study 4 determined the aerobic – anaerobic energy system contribution (AOD method) to track running events of 400-m (for males and females) as 41% 59% and 45% 55% and for 800-m events as 60% 40% and 70 30% respectively. Study 5 determined the relative aerobic – anaerobic energy system contribution (AOD method) (for males and females) as 21% 79% and 25% 75% for 100-m track events and 28% 72% and 33% 67% for 200-m events. Pr r e e f ffa a c c e e iv The data from these three studies concurs with recent laboratory research into the energetics of track events, while providing applied (in-race) data about both the role and interaction of the respective metabolic pathways throughout events of 100-m to 3000-m. Also, these studies highlight and confirm previous research outlining both the significance of and speed at which the aerobic energy system becomes involved in maximal exercise between 11 s and 10 min in duration. In addition, from all three studies, measured in-race physiological parameters that correlated with track performance were also identified. While one particular in-race measure was not uniformly associated with performance in all track events, a variety of individual measures did show relationships with performance in different events. Velocity at peak V&O2 (v-V&O2 peak) was correlated with male 3000-m performance (r= 0.89), while peak V&O2 and peak race V&O2 were associated with male 1500-m performance (r= -0.68 and -0.69 respectively). Anaerobic energy contribution (La/PCr) was associated with male 800-m and female 400-m performance (r= -0.77 and -0.87 respectively) while anaerobic energy contribution (AOD) was associated with female 200-m performance (r = -0.96). Finally, study 6 revealed that during 800-m, 1500-m and 3000-m middle-distance track running events, faster initial running velocities were associated with faster ontransient V&O2 responses (τ1) (r = -0.54 to –0.78, p<0.01, n = 26). Also, a trend was noted for faster τ values the shorter the event distance (14.0, 18.5 and 20.8 s for 800m, 1500-m and 3000-m events respectively). Furthermore, the relationship between τ1 and initial race velocity suggested that those individuals with a faster start had both a faster τ1 and a better performance. As such, performance in faster/shorter middlePr r e e f ffa a c c e e v distance events (especially the 1500-m event) was strongly correlated with a faster ontransient V&O2 response (r = 0.71, p<0.05, n = 8). Pr r e e f ffa a c c e e vi