John Bateman, bg51sv@student.sunderland.ac.uk The Influence of Positional Biomechanics on Gross Efficiency within Cycling John Bateman, bg51sv@student.sunderland.ac.uk Faculty of Applied Sciences, University of Sunderland, Sunderland SR1 3SD. Results Introduction Gross efficiency can be described as the ratio of work generated against the total metabolic cost (Gaesser and Brooks, 1975). It plays a key role in endurance performance and has been described as one of three key performance factors alongside VO2 and the lactate threshold (Coyle, 1999). Small increases in efficiency can have a significant impact on performance (Jeukendrup and Martin, 2001), if a positive effect can be found, then the research can validate the Retul system for well-trained athletes. Research has found that manipulation of a single variable of bike-fit such as saddle height can improve performance within cycling efficiency (Peveler and Green, 2010). However, limited research exists concerning the biomechanical influences on gross efficiency, a key factor in endurance performance (Ettema and Lorås, 2009). Aims Investigate the hypothesis that differences may exist in a rider’s gross efficiency when comparing their preferred cycling set-up against a position composed of normative values provided by a bike fitting company, in this case, Retul. Methodology Six male competitive cyclists were recruited (mean ± SD: age, 30 ± 13.1 years (yr); height, 179.9 ± 5.7 cm; mass, 75.1 ± 8.1 kg; Wmax, 330 ± 19.1 W; VO2 max, 66.1 ± 10.3 mL.kg-1.min-1). Four tests were completed for each subject; VO2max Test, Retul bike fit, 2 x Submaximal tests – incremental test, 8 minutes at 3 intensities; 50%, 60%, 70% VO2max Max Power Output (MPO). HR, Blood lactate & continuous online gas analysis was recorded.  Figure 1. Data collection during the Retul bike fit. The Retul system reads the body in motion, in three dimensions while the cyclist pedals.   Figure 2. The distribution of subject’s age and GE during 3 incremental workloads of 50%, 60% and 70% Wmax, within pre and post Retül bike fit conditions. Discussion Higher % increases in GE than previous studies related to changes in GE over time (2.74% in the present study vs. 1-2% (Coyle, 1995). This suggests biomechanical changes can improve performance in well-trained cyclists. GE was seen to rise alongside an increase in % workload; this trend is in line with previous studies that have followed a similar methodology (Leirdal and Ettema, 2010, Ettema and Lorås, 2009). The distribution of efficiency values for each subject recorded across each test has shown there may be a trend within the group (figure 2). Results Significant changes were observed (p=0.037) during the post bike-fit condition within the 60% Wmax increment (16.78% vs.17.44%; p= .037). Increases were apparent within the 50% Wmax increment (16.27% vs. 16.44%; p= 0.565) and again within the 70% Wmax workload (17.60% vs. 18.18%; p= 0.111). Table 1. Absolute mean values for GE across pre and post bike fit test at workloads of 50%, 60% and 70% Wmax for all subjects. Key Points This study has found an increase in gross efficiency between pre and post bike-fit conditions. Possible trend within cycling experience and GE improvements within the participant group that would benefit from further investigation. References Coyle, E.F., 1995. Integration of the physiological factors determining endurance performance ability. Exerc Sport Sci Rev 23, 25–63. Coyle, E.F., 1999. Physiological determinants of endurance exercise performance. Journal of science and medicine in sport / Sports Medicine Australia, 2(3), pp.181–9. Ettema, G. and Lorås, H.W., 2009. Efficiency in cycling: a review. European journal of applied physiology, 106(1), pp.1–14. Gaesser, G. A., and Brookes, G. A., 1975 Muscular efficiency during steady-state exercise: effects of speed and work rate. Journal of Applied Physiology. 38. pp. 1132-1139. Jeukendrup, A.E. and Martin, J., 2001. Improving cycling performance: how should we spend our time and money. Sports medicine (Auckland, N.Z.), 31, pp.559–569. Leirdal, S. and Ettema, G., 2011. The relationship between cadence, pedalling technique and gross efficiency in cycling. European Journal of Applied Physiology, 111, pp.2885–2893. Peveler, W.W. and Green, J.A., 2010. Effects of saddle height on economy and anaerobic power in well-trained cyclists. The Journal of Strength and Conditioning Research, 25(3), pp.1–5. Mean (±SD) GE at % workload of Wmax Test 50% 60% 70% Pre fit 16.27 (±.82) 16.78 (±.54) 17.60 (±.71) Post fit 16.43 (±.88) 17.44 (±1.01) 18.18 (±.90)