W. Bertucci

Aerodynamic drag in cycling: methods of assessment

When cycling on level ground at a speed greater than 14 m/s, aerodynamic drag is the most important resistive force. About 90% of the total mechanical power output is necessary to overcome it. Aerodynamic drag is mainly affected by the effective frontal area which is the product of the projected frontal area and the coefficient of drag. The effective frontal area represents the position of the cyclist on the bicycle and the aerodynamics of the cyclist-bicycle system in this position. In order to optimise performance, estimation of these parameters is necessary. The aim of this study is to describe and comment on the methods used during the last 30 years for the evaluation of the effective frontal area and the projected frontal area in cycling, in both laboratory and actual conditions. Most of the field methods are not expensive and can be realised with few materials, providing valid results in comparison with the reference method in aerodynamics, the wind tunnel. Finally, knowledge of these parameters can be useful in practice or to create theoretical models of cycling performance.

Telic dominance influences affective response to a heavy-intensity 10-min treadmill running session

Abstract In this paper, we examine the hypothesis that telic dominance is one of the psychological variables that may influence the exercise–affect relationship according to the dual-mode model of exercise and affect (Ekkekakis, 2003). Thirty-three participants with high or low telic dominance rated their affect at 3-min intervals as they ran on a treadmill while the speed was adjusted to maintain their respiratory exchange ratio at a target value of 1.00 ± 0.02 for a period of 10 min. Compared with baseline scores (which were not statistically different between the two groups), the mean decline in pleasure at the end of the run was twofold greater in participants with high telic dominance. This was observed after having controlled for individual differences in aerobic fitness (as measured by [Vdot]O2max). We also detected an earlier onset of decreases in pleasure in high telic dominant participants. Our data extend the burgeoning research on variables influencing ones ability to continue exercising at an imposed intensity that can produce pain or discomfort (i.e. tolerance of exercise intensity). Additionally, results from this study support continued promotion of tailor-made prescriptions for maximizing positive affective outcomes during exercise, which ultimately may lead to increased adherence to an exercise programme.

New Method to Estimate the Cycling Frontal Area

The purpose of this study was to test the validity and reliability of a new method to estimate the projected frontal area of the body during cycling. To illustrate the use of this method in another cycling speciality (i.e. mountain bike), the NM data were coupled with a powermeter measurement to determine the projected frontal area and the coefficient of drag in actual conditions. Nine male cyclists had their frontal area determined from digital photographic images in a laboratory while seated on their bicycles in two positions:Upright Position (UP) and Traditional Aerodynamic Position (TAP). For each position, the projected frontal area for the body of the cyclist as well as the cyclist and his bicycle were measured using a new method with computer aided-design software, the method of weighing photographs and the digitizing method. The results showed that no significant difference existed between the new method and the method of weighing photographs in the measurement of the frontal area of the body of cyclists in UP (p=0.43) and TAP (p=0.14), or between the new method and the digitizing method in measurement of the frontal area for the cyclist and his bicycle in UP (p=0.12) and TAP (p=0.31). The coefficients of variation of the new method and the method of weighing photographs were 0.1% and 1.26%, respectively. In conclusion, the new method was valid and reliable in estimating the frontal area compared with the method of weighing photographs and the digitizing method.

Hand-arm vibration in cycling

Numerous workers are exposed to vibrations which can turn out to be fatal for the health. Athletes can be included in this population, in particular cyclists who are exposed to vibration due to the irregularity of the road. This nuisance depends of the duration of exposure and the range of vibrations. While the worker is mostly directly excited by a vibrating system, the cyclist is indirectly subjected to it. He undergoes the vibrations of an excited sub-structure which is the bicycle. So the bicycle plays the role of a vibration filter or amplifier. In this paper we propose to (i) study the transmission of vibrations to the cyclist after excitation on a paving road, (ii) calculate the limit time of exposure to this type of excitation rate by the use of the standard ISO 5349 and the European directive 2002/44/EC, and (iii) compare the weighting curve of the standard with a vibrations transmissibility curve obtained between the collarbone and the stem. For this particular case of an excited sub-structure, a weighting curve is proposed by considering the first modal frequency of the bicycle.

Relationship between the gross efficiency and muscular skin temperature of lower limb in cycling: a preliminary study

In cycling, the gross efficiency (GE, %), defined as the ratio of the power output to the metabolic power (total energy expended according to the time), is one of the main determinants of the performance (Ettema et al. 2009; Jobson et al. 2012). In the literature, the average GE values reported vary from10% to 25% (Faria et al. 2005). In this range, close to 75–90% of metabolic energy is not converted to mechanical energy, but is used to maintain metabolic equilibrium (from adenosine triphosphate hydrolysis) and released as heat. Tomaintain the central temperature close to 37.58C, this produced energy must be dissipated using a thermoregulation process. Infrared thermography measurements can be used to analyse this thermoregulation process and understand the way one part of the energy dissipates (Arfaoui et al. 2012). The aim of this studywas to analyse the relationships that may exist between the GE and the muscular skin temperature of the lower limb in cycling.

Interactive-Virtual Reality (IVR) Exercise: An Examination of In-Task and Pre-to-Post Exercise Affective Changes

In this research, we examine the influence of imposed vs. self-chosen interactive/virtual reality (IVR) exercise on affect response following, as well as during, exercise. Our sample included 131 university students who were assigned to one of three 10-min conditions: (a) self-selected interactive/virtual reality (IVR) exercise, (b) externally imposed IVR exercise, or (c) regular exercise. Exercise intensity was standardized in terms of metabolic benchmarks. Mood benefits were observed pre-to-post exercise regardless of condition. During exercise, however, higher pleasure ratings were reported by participants in the self-selected IVR exercise condition. The implications of the immediate mood effects of self-selected IVR exercise are discussed.

Validity and reliability of the G-Cog BMX Powermeter.

The aim of this study was to test the validity and reliability of the G-Cog which is a new BMX power meter allowing for the measurements of the power output (250 Hz) at the BMX rear wheel during actual cycling and laboratory conditions. Sprints in road cycling (6-8 s) from static start and incremental tests in the laboratory (100-400 W) have been performed to analyse the validity and reliability of the power output values by comparison with 2 devices: The PowerTap and the SRM which are considered as the gold standard. The most important finding of this study is that the G-Cog power output data were not valid and reliable during sprint and standardised laboratory tests compared with the SRM and the PowerTap devices. During the sprint and the laboratory tests the ratio limits of agreement of the power output differences between the SRM and G-Cog were 1.884×÷1.970 (95% CI = .956-3.711) and 12.126×÷16.281 (95% CI = 0.745-197.430), respectively. In conclusion, the G-Cog must be used with caution regarding the power output measurements. Nevertheless, the G-Cog could be used for the first time to analyse the determinants of the BMX performance from the pedalling profile.

Validity and reliability of the G-Cog device for kinematic measurements.

The aim of this study was to test the validity and the reliability of the G-Cog which is a new BMX powermeter allowing for the measurements of the acceleration on X-Y-Z axis (250 Hz) at the BMX rear wheel. These measurements allow computing lateral, angular, linear acceleration, angular, linear velocity and the distance. Mechanical measurements at submaximal intensities in standardized laboratory conditions and during maximal exercises in the field conditions were performed to analyse the reliability of the G-Cog accelerometers. The performances were evaluated in comparison with an industrial accelerometer and with 2 powermeters, the SRM and PowerTap. Our results in laboratory conditions show that the G-Cog measurements have low value of variation coefficient (CV=2.35%). These results suggest that the G-cog accelerometers measurements are reproducible. The ratio limits of agreement of the rear hub angular velocity differences between the SRM and the G-Cog were 1.010 × ÷ 1.024 (95%CI=0.986-1.034) and between PowerTap and G-Cog were 0.993 × ÷ 1.019 (95%CI=0.974-1.012). In conclusion, our results suggest that the G-Cog angular velocity measurements are valid and reliable compared with SRM and PowerTap and could be used to analyse the kinematics during BMX actual conditions.

Validity, Sensitivity, Reproducibility and Robustness of the Powertap, Stages and Garmin Vector Power Meters in Comparison With the SRM Device

A large number of power meters have been produced on the market for nearly 20 y according to user requirements. PURPOSE To determine the validity, sensitivity, reproducibility, and robustness of the PowerTap (PWT), Stages (STG), and Garmin Vector (VCT) power meters in comparison with the SRM device. METHODS A national-level male competitive cyclist completed 3 laboratory cycling tests: a submaximal incremental test, a submaximal 30-min continuous test, and a sprint test. Two additional tests were performed, the first on vibration exposures in the laboratory and the second in the field. RESULTS The VCT provided a significantly lower 5-s power output (PO) during the sprint test with a low gear ratio than the SRM did (-36.9%). The STG PO was significantly lower than the SRM PO in the heavy-exercise-intensity zone (zone 2, -5.1%) and the low part of the severe-intensity zone (zone 3, -4.9%). The VCT PO was significantly lower than the SRM PO only in zone 2 (-4.5%). The STG PO was significantly lower in standing position than in the seated position (-4.4%). The reproducibility of the PWT, STG, and VCT was similar to that of the SRM system. The STG and VCT PO were significantly decreased from a vibration frequency of 48 Hz and 52 Hz, respectively. CONCLUSIONS The PWT, STG, and VCT systems appear to be reproducible, but the validity, sensitivity, and robustness of the STG and VCT systems should be treated with some caution according to the conditions of measurement.

Effects of different types of tyres and surfaces on the power output in the mountain bike field conditions: a preliminary study

The performance (speed) in cycling is determined by the ratio of the cyclist power output (PO, W) and the total resistance to the motion (Rt, N). The Rt is composed by the aerodynamic drag, the gravitational force and the rolling resistance (Rr, N). The PO 1⁄4 [0.5 r·SCx·Va þ m·g sin(a) þ m·g·Cr]V, where r is the air density (kg/m), SCx the effective frontal area (m), m the mass of the cyclist-bicycle system (kg), g the gravity acceleration (m/s), a the slope of the road (8), Cr the rolling coefficient, Va the sum of the cyclist velocity (V) and the wind velocity (m/s). In mountain bike racing, the speed during the race was lower than the road cycling race (5–9 m/s in mountain bikes versus 11–14 m/s in road cycling). In this condition, the aerodynamic resistance in mountain bikes could have a lower importance than in road cycling. Thus, the Rr could have a higher importance in the performance. The Rr can be defined by the resistance to the motion of a wheel. The Rr is used to describe the resistance to the steady motion of the wheel caused by power absorption in the contacting surfaces of the wheel and the road. The cyclists give important attention to the tyre inflation pressure and to the choice of the type of tyre in the goal to decrease theRr and conserve a great adherence in the curve and in the trail with high slope. The aim of this preliminary study was to measure the PO and determine the Cr in mountain bikes on different surfaces with two different tyres and inflation pressures.