Effect of different aerodynamic time trial cycling positions on muscle activation and crank torque D. M. Fintelman 1 , M. Sterling 2 , H. Hemida 2 , F.-X. Li 1 1 School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK, 2 School of Civil Engineering, University of Birmingham, Birmingham, UK Corresponding author: François-Xavier Li, School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. Tel.: +44 121 414 4114, Fax: +44 121 414 4121, E-mail: F.X.Li@bham.ac.uk Accepted for publication 23 March 2015 To reduce air resistance, time trial cyclists and triathletes lower their torso angle. The aim of this study was to investigate the effect of lowering time trial torso angle positions on muscle activation patterns and crank torque coordination. It was hypothesized that small torso angles yield a forward shift of the muscle activation timing and crank torque. Twenty-one trained cyclists performed three exercise bouts at 70% maximal aerobic power in a time trial position at three different torso angles (0°, 8°, and 16°) at a fixed cadence of 85 rpm. Measurements included surface electromyography, crank torques and gas exchange. A significant increase in crank torque range and forward shift in peak torque timing was found at smaller torso angles. This relates closely with the later onset and duration of the muscle activation found in the gluteus maximus muscle. Torso angle effects were only observed in proximal monoarticular muscles. Moreover, all measured physiological variables (oxygen consump- tion, breathing frequency, minute ventilation) were sig- nificantly increased with lowering torso angle and hence decreased the gross efficiency. The findings provide support for the notion that at a cycling intensity of 70% maximal aerobic power, the aerodynamic gains outweigh the physiological/biomechanical disadvantages in trained cyclists. Aerodynamic drag is the dominant resistance force during cycling on a flat road (Kyle & Burke, 1984; Debraux et al., 2011). To minimize drag, cyclists and triathletes adopt a time trial position and lower their torso angle to reduce frontal area (Lukes et al., 2005). However, conflicting results on the effect of torso angle on the physiological measures at submaximal intensity were presented in the literature. For example, while comparing different typical cycling positions (i.e., upright, dropped and time trial position), no position effects were found (Berry et al., 1994; Jobson et al., 2008; Dorel et al., 2009). In contrast, other studies dem- onstrated that riding in a time trial position negatively affects physiological measures (Evangelisti et al., 1995; Gnehm et al., 1997; Grappe et al., 1998). Remarkably, only a few studies have investigated the effect of posi- tion changes on the muscle recruitment and crank torques. Examples of studies examining the effect of position alterations on the muscular and mechanical factors are the investigations of Savelberg et al. (2003), Chapman et al. (2008), and Dorel et al. (2009). Savelberg et al. (2003) have observed changes in muscle recruitment in a fully vertical upright cycling position and a 20° forward and backward position. Likewise, Chapman et al. (2008) have found increased muscle activation during secondary muscle activity (muscle activity between primary bursts) and greater coactivity when cycling in a dropped position compared with an upright position. No changes were found in the leg or foot kine- matics between the two aforementioned positions. The only study that simultaneously recorded crank forces and muscle activations in the three typical cycling posi- tions (upright, dropped and time trial) is the study of Dorel et al. (2009). They observed increased muscle activation in the gluteus maximus (Gmax) in the time trial position compared with the upright and dropped positions. This was closely related to higher observed downstroke peak forces and later force application during the pedal stroke in the time trial position. The higher downstroke peak forces compensate for the lower negative upstroke peak forces observed in the time trial position. Dorel’s study has been focused on comparing different typical cycling positions and there- fore the torso angles examined were relatively large (> 21°). The analyzed positions in the latter study are consequently less optimal in terms of decreasing aero- dynamic drag. To reduce air resistance while riding in a time trial position, a horizontal torso has been recom- mended by Martin and Cobb (2002). Thus, although © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd 528 Scand J Med Sci Sports 2016: 26: 528–534 doi: 10.1111/sms.12479