EFFECT OF SUSPENSION SYSTEMS ON THE PHYSIOLOGICAL AND PSYCHOLOGICAL RESPONSES TO SUB-MAXIMAL BIKING ON SIMULATED SMOOTH AND BUMPY TRACKS ABSTRACTThe aim of this study was to compare the physiological and psychological responses of cyclists riding on a hard tail (HT) bicycle and on a full suspension (SU) bicycle. Twenty male subjects participated in two series of tests. A test rig held the front axle of the bicycle steady while the rear wheel rotated against a heavy roller with bumps (or no bumps) on its surface. In the first test series, eight subjects (age 19-27 years, body mass 65-82 kg) were tested on both the SU and HT bicycles with and without bumps fitted to the roller. The second test series repeated the bump tests with a further six subjects (age 22-31 years, body mass 74-94 kg) and also involved an investigation of familiarisation effects with the final six subjects (age 21-30 years, body mass 64-80 kg). Heart rate (HR), oxygen consumption ( V ), rating of perceived exertion (RPE) and comfort were recorded during 10 min submaximal tests. Combined data for the bumps tests show that the SU bicycle was significantly different (P<0.001) from the HT bicycle on all four measures. V , HR and RPE were lower on average by 8.7, s=3.6 ml.kg-1 , 32.1, s=12.1 beats.min -1 and 2.6, s=2.0 units respectively. Comfort scores were higher (better) on average by 1.9, s=0.8 units. For the no bumps tests, the only statistically significant difference (P=0.008) was in , which was lower for the HT bicycle by 2.2, s= 1.7 ml.kg -1 .min -1 . These data indicate that the SU bicycle provides a physiological and psychological advantage over the HT bicycle during simulated sub-maximal exercise on bumps.

The aim of the work reported here was to investigate the potential benefits of rear suspension systems for mountain bikes and to develop numerical models that could be used in future to help with the design of improved suspension configurations. As the basis for a study of the effect of rear suspensions, two bicycles were chosen: one with full suspension and one with only front suspension (hard tail). Apart from the rear suspension, all other aspects of the bicycles were closely matched. In order to control the number of variables, a special rolling road test rig was used. Eight subjects were asked to ride each bicycle on the rig in random order. Measurements were taken of pedal torque and speed, rear wheel speed, forward thrust at front axle and vertical acceleration at the saddle and handlebars. Physiological measurements were also taken, but these are reported elsewhere. A DADS model of the rolling road rig, bicycle and rider was created and numerical simulations were performed. The results of the numerical simulations compared well with the experimental results. Unmeasured parameters predicted by the DADS model could therefore be used with reasonable confidence to aid the understanding of the suspension performance. Physiological results, mechanical measurements and simulation results all indicate that the full suspension bicycle shows a significant improvement in terms of comfort and energy expenditure when riding over regular bumps. The good correlation between measurement and simulation provides a tool that can be used in future for optimization of bicycle suspension design.

A significant distinction between competitive mountain bikes is whether they have a suspension system. Research studies indicate that a suspension system gives advantages, but it is difficult to quantify the benefits because they depend on so many variables, including the physiology and psychology of the cyclist, the roughness of the track and the design of the suspension system. A laboratory based test rig has been built that allows the number of variables in the system to be reduced and test conditions to be controlled. The test rig simulates regular impacts of the rear wheel with bumps in a rolling road. The physiological variables of oxygen consumption and heart rate were measured, together with speeds and forces at various points in the system. Physiological and mechanical test results both confirm a significant benefit in using a suspension system on the simulated rough track, with oxygen consumption reduced by around 30 % and power transmitted through the pedals reduced by 30 % to 60 %.