1 University of Chichester, Chichester UK Comparison of the energy system contribution during an exhaustive run at peak treadmill speed in junior and senior middle distance athletes. Andrew. T. West1, Simon Northcott1, David. M. Wilkinson1, Marcus. S. Smith1 1 University of Chichester, Chichester UK BASES Conference Nottingham, UK 29 – 30 November 2016 a.west@chi.ac.uk www.chi.ac.uk INTRODUCTION RESULTS Continued Middle-distance running (800 and 1500 m) is popular amongst children and adolescents[1]. Success in these events require a dynamic interplay between aerobic and anaerobic metabolic pathways[2], with an “immaturity” of the latter pathway frequently cited in junior populations[3]. Despite its popularity, little is known regarding the energy system interaction during middle distance running in well trained junior runners. * Purpose: To compare the contribution of aerobic and anaerobic metabolism to overall energy production during exhaustive high speed treadmill running in trained junior and senior athletes. 43.5 50.6 METHODS Participants - Following institutional ethics approval, 20 male middle distance runners volunteered (Table 1). Protocols – Participants completed an incremental test and ramp test to determine: (1) the relationship between running speed and the rate of oxygen uptake (VO2); (2) maximal rate of oxygen uptake (VO2max); and (3) peak treadmill speed (PTS). The relative aerobic and anaerobic contribution was estimated using the accumulated oxygen deficit (AOD) method during an exhaustive run at PTS. Data Analysis – Independent samples t tests were used to compare junior and senior responses with statistical significance set a priori (P<0.05). Mean differences ± 95% confidence intervals were calculated and the normalised differences were expressed as effect sizes (Cohen’s d), whereby differences were interpreted as small (0.1), moderate (0.3), large (0.5) and very large (0.7)[4]. Figure 1: The mean ± SD accumulated oxygen deficit during the exhaustive run at PTS. t(13.493)= 2.412, P = 0.03, d = 1.07. Table 1: Participant descriptive statistics. Age (years) Stature (m) Mass (kg) 800 m (s) Junior (n=10) 12.6 ± 0.6* 1.56 ± 0.07* 41.8 ± 6.7* 147.9 ± 6.5* Senior (n=10) 26.1 ± 5.5* 1.80 ± 0.05* 68.9 ± 5.8* 116.1 ± 2.4* *P < 0.05 29.8 % 27.0 % . . 73.0 % 70.2% Figure 2: The mean ± SD relative aerobic and anaerobic contributions to overall energy production during an exhaustive run at PTS. t(18) = -1.558, P = 0.14, d = 0.72. . These data show the accumulated oxygen deficit expressed relative to body mass is attenuated in junior (~13 yrs) athletes when compared with senior athletes. A reduced ability to generate energy via anaerobic pathways may partly explain the greater reliance on aerobic metabolism observed in junior athletes compared with senior athlete during an exhaustive run at peak treadmill speed. . RESULTS . The relative VO2 demand at PTS was not different between the groups (SEN, 115 ± 5 vs. JUN, 115 ± 4 %VO2max; P = 0.91). The mean relative contributions of the aerobic (senior, 70 ± 3 vs. junior, 73 ± 5 %) and anaerobic (SEN, 30 ± 3 vs. JUN, 27 ± 5 %) energy pathways were not different (P = 0.14), although an effect size of d = 0.72 is indicative of a practical difference [5]. . REFERENCES [1] Shibli, S., and Barrett, D. (2011) Bridging the Gap: Research to provide insight into the development and retention of young athletes. [2] Di Prampero, P.E., Capellie C., Pagliaro, P. et al. (1993). Energetics of best performances in middle distance running. Journal of Applied Physiology, 74(5), 2318-24. [3] Armstrong, Barker and McManus, 2015, British Journal of Sports Medicine, 49(13), 860-64. [4] Cohen J. (1998). Statistical Power Analysis for the Behavioural Sciences. 2nd ed. Hillsdale, NJ: Lawrence Erlbaum; page 567. [5] Hopkins, W.G. et al. (2009) Progressive statistics for studies in sports medicine and exercise science. Medicine and Science in Sports and Exercise. 41(3): 3-13. Table 2: The mean ± SD [95% CI] of performance and physiological responses during the exhaustive run at PTS. PTS (km/h) TTE (s) Distance (m) VO2max (ml∙kg⁻¹∙min⁻¹) Junior 18.1 ± 0.7* [17.7 to 18.6] 133 ± 16 [121.7 to 144.9] 673 ± 95* [605 to 741] 63.1 ± 2.0* [61.6 to 64.5] Senior 21.9 ± 1.0* [21.2 to 22.6] 133 ± 11 [125.4 to 140.5] 808 ± 68* [759 to 857] 66.3 ± 2.6* [64.4 to 68.1] PTS = Peak Treadmill Speed; TTE = Time to Exhaustion *P < 0.05 . ACKNOWLEDGEMENT We would like to acknowledge the contribution of our friend and colleague Dr. David Wilkinson to this research.