Effect of different aerodynamic time trial cycling positions on muscle activation and crank torque

Abstract

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 consumption, breathing frequency, minute ventilation) were significantly 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.

Influence of upright versus time trial cycling position on determination of critical power and W′ in trained cyclists

“…Exercise intensity and torso angle have been shown to affect stroke volume, cardiac output muscle blood flow, deoxygenation and gross efficiency (Fintelman et al, 2016;Foster et al, 1999;Hettinga, Konings, & Cooper, 2016). Recently, Fintelman et al (2016) showed that lowering torso angle whilst cycling at 70% maximal aerobic power increased oxygen consumption, breathing frequency, minute ventilation and decreased gross efficiency. In speed skating, where athletes also adopt 'aggressive' aerodynamic positions with low torso angles, similar observations have been made.…”

Riding against the wind: a review of competition cycling aerodynamics

“…This was identified in an early wind tunnel study conducted by Kyle and Burke [3] which led them to propose a three-tier hierarchy for reducing cycling resistance: (1) the position of the rider, (2) the geometry of the bicycle (or more generally cycling equipment), and (3) the methods for minimising the rolling resistance and drive-train friction losses. Although the biomechanics and physiological efficiency of cycling are outside the scope of this review, when optimising cycling performance, the power output and fatigue characteristics of cyclists must also be weighed up against any apparent gains in the aerodynamic performance through adjustment to position [47][48][49]. Any changes to rider posture must also be considered along with current UCI rulings on legal rider positions.…”

Gross and delta efficiencies during uphill running and cycling among elite triathletes

“…Based on fundamental physics, these deceleration/acceleration phases are associated with a significant energy cost; however, the relative energy-cost contribution related to translational kinetic energy decreases during uphill running, because on inclines the braking forces at the foot plant decrease (Gottschall and Kram 2005). In cycling, the fluctuation in speed during the pedal cycle is lower than in running due to the continuous supply of power (Fintelman et al 2016;van Ingen Schenau et al 1990). The described energyexpenditure differences between the exercise modes result in a reduced biomechanical efficiency during running compared to cycling, which is the major factor explaining the lower GE during running.…”