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1.
Cycling     
The resistance against a cyclist while riding on rollers is due mainly to rolling resistance produced by the deformation of the tyre as it rolls against small diameter drums. Resistance is then combined with wheel speed to set power output. The effect of tyre pressure and cross‐section on power was investigated by systematically altering the pressure (552 kPa, 690 kPa, and 827 kPa) in a 20c, 23c, 25c, and 28c tyre of the same design while riding at a wheel speed of 45 kph. Average power over 1 minute was measured with a Power Tap Hub (Tune Corporation, Cambridge, Massachusetts, USA) on five occasions. Statistical significance was evaluated at p < 0.05. Power requirements increased significantly with each reduction in tyre pressure for all tyres and pressures except the 25c between 690 and 827 kPa. The 20c tyre required significantly more power from the cyclist at each tested tyre pressure when compared to the other tyres (which were not different from each other). The differences in resistance from tyre size were not observed when ridden on the road. Additionally, a slightly different tyre design from the same manufacturer responded similarly in the 20c, but was significantly different in the 23c size. It was also observed that power requirements increased significantly when both the wheels were ridden on the rollers as compared to just the rear wheel. These results indicate that the power requirements may be significantly altered by the cyclist by adjusting tyre pressure, tyre cross‐section size, tyre type, and with the number of wheels contacting the rollers. However, the magnitude of these power requirements may not be suitable for intense workouts of trained cyclists.  相似文献   

2.
The rim width of cross-country mountain bike wheel sets has increased in recent years, but the effect of this increase on performance remains unknown. The aim of this study was to analyse the influence of rim width on rolling resistance and off-road speed. We compared 3 tubeless wheel sets: 25 mm inner width as baseline, 30 mm width with the same tyre stiffness, and 30 mm width with the same tyre pressure. Three riders conducted 75 rolling resistance tests for each wheel set on a cross-country course. We determined rolling resistance using the virtual elevation method and calculated off-road speeds for flat and uphill conditions using a mathematical model. Baseline rolling resistance (Cr) was 0.0298, 90% CI [0.0286, 0.0310], which decreased by 1.4%, [0.7, 2.2] with the wider rim and the same tyre stiffness and increased by 0.9%, [0.1, 1.6] with the wider rim and the same tyre pressure. The corresponding effects on off-road speed were most likely trivial (0.0% to 0.7% faster and 0.1% to 0.6% slower, respectively). Because the effect of rim width on off-road speed seems negligible, athletes should choose the rim width that offers the best bike handling and should experiment with low tyre pressures.  相似文献   

3.
ABSTRACT

The purpose of this study was to determine the influence of different wheel size diameters on indicators of cross-country mountain bike time trial performance. Nine competitive male mountain bikers (age 34.7 ± 10.7 years; stature 177.7 ± 5.6 cm; body mass 73.2 ± 8.6 kg) performed 1 lap of a 3.48 km mountain bike (MTB) course as fast as possible on 26″, 27.5″ and 29″ wheeled MTB. Time (s), mean power (W), cadence (revs · min?1) and velocity (km · h?1) were recorded for the whole lap and during ascent and descent sections. One-way repeated measure ANOVA was used to determine significant differences. Results revealed no significant main effects for any variables by wheel size during all trials, with the exception of cadence during the descent (F(2, 16) = 8.96; P = .002; P2 = .53). Post hoc comparisons revealed differences lay between the 26″ and 29″ wheels (P = .02). The findings indicate that wheel size does not significantly influence performance during cross-country when ridden by trained mountain bikers, and that wheel choice is likely due to personal choice or sponsorship commitments.  相似文献   

4.
Abstract

Aerodynamic and rolling resistances are the two major resistances that affect road cyclists on level ground. Because of reduced speeds and markedly different tyre-ground interactions, rolling resistance could be more influential in mountain biking than road cycling. The aims of this study were to quantify 1) aerodynamic resistance of mountain-bike cyclists in the seated position and 2) rolling resistances of two types of mountain-bike tyre (smooth and knobby) in three field surfaces (road, sand and grass) with two pressure inflations (200 and 400 kPa). Mountain-bike cyclists have an effective frontal area (product of projected frontal area and drag coefficient) of 0.357 ± 0.023 m2, with the mean aerodynamic resistance representing 8–35% of the total resistance to cyclists' motion depending on the magnitude of the rolling resistance. The smooth tyre had 21 ± 15% less rolling resistance than the knobby tyre. Field surface and inflation pressure also affected rolling resistance. These results indicate that aerodynamic resistance influences mountain-biking performance, even with lower speeds than road cycling. Rolling resistance is increased in mountain biking by factors such as tyre type, surface condition and inflation pressure that may also alter performance.  相似文献   

5.
马国强  刘茂  唐琪 《体育科研》2016,(4):91-94，99
自行车骑行效率通常被定义为自行车骑行过程中一定氧耗和能耗水平下的功率输出,自行车骑行能力的增强,多伴随骑行效率的提高。性别、年龄、骨骼肌纤维类型的差异会对骑行效率产生不同影响;而自行车骑行过程中踏蹬技术、身体姿态,甚至运动器材的变化,则可通过改变踏蹬过程中骨骼肌发力和能耗影响骑行效率;专业自行车运动员的骑行效率与训练强度呈正相关关系,阶段性的肌力或专项训练可能通过提高做功和能量节省化促进骑行效率的。  相似文献   

6.
This investigation sets out to assess the effect of five different models of mountain bike tyre on rolling performance over hard-pack mud. Independent characteristics included total weight, volume, tread surface area and tread depth. One male cyclist performed multiple (30) trials of a deceleration field test to assess reliability. Further tests performed on a separate occasion included multiple (15) trials of the deceleration test and six fixed power output hill climb tests for each tyre. The deceleration test proved to be reliable as a means of assessing rolling performance via differences in initial and final speed (coefficient of variation (CV) = 4.52%). Overall differences between tyre performance for both deceleration test (P = 0.014) and hill climb (P = 0.032) were found, enabling significant (P < 0.0001 and P = 0.049) models to be generated, allowing tyre performance prediction based on tyre characteristics. The ideal tyre for rolling and climbing performance on hard-pack surfaces would be to decrease tyre weight by way of reductions in tread surface area and tread depth while keeping volume high.  相似文献   

7.
ABSTRACT

This study aimed to investigate the influence of different mountain bike wheel diameters on muscle activity and whether larger diameter wheels attenuate muscle vibrations during cross-country riding. Nine male competitive mountain bikers (age 34.7 ± 10.7 years; stature 177.7 ± 5.6 cm; body mass 73.2 ± 8.6 kg) participated in the study. Riders performed one lap at race pace on 26, 27.5 and 29 inch wheeled mountain bikes. sEMG and acceleration (RMS) were recorded for the full lap and during ascent and descent phases at the gastrocnemius, vastus lateralis, biceps brachii and triceps brachii. No significant main effects were found by wheel size for each of the four muscle groups for sEMG or acceleration during the full lap and for ascent and descent (P > .05). When data were analysed between muscle groups, significant differences were found between biceps brachii and triceps brachii (P < .05) for all wheel sizes and all phases of the lap with the exception of for the 26 inch wheel during the descent. Findings suggest wheel diameter has no influence on muscle activity and vibration during mountain biking. However, more activity was observed in the biceps brachii during 26 inch wheel descending. This is possibly due to an increased need to manoeuvre the front wheel over obstacles.  相似文献   

8.
In long-distance competitive cycling, efforts to mitigate the effects of air resistance can significantly reduce the energy expended by the cyclist. A common method to achieve such reductions is for the riders to cycle in one large group, known as the peloton. However, to win a race a cyclist must break away from the peloton, losing the advantage of drag reduction and riding solo to cross the finish line ahead of the other riders. If the rider breaks away too soon then fatigue effects due to the extra pedal force required to overcome the additional drag will result in them being caught by the peloton. On the other hand, if the rider breaks away too late then they will not maximize their time advantage over the main field. In this paper, we derive a mathematical model for the motion of the peloton and breakaway rider and use asymptotic analysis techniques to derive analytical solutions for their behaviour. The results are used to predict the optimum time for a rider to break away that maximizes the finish time ahead of the peloton for a given course profile and rider statistics.  相似文献   

9.
Although a low rolling resistance is advantageous in mountain bike cross-country racing, no studies have used the virtual elevation method to compare tyres from different manufacturers as used in international competitions so far. The aims of this study were to assess the reliability of this method, to compare the off-road rolling resistance between tyres and to calculate the influence on off-road speed.

Nine 29-in. mountain bike cross-country tyres were tested on a course representing typical ground surface conditions 5 or 6 times. The coefficient of rolling resistance was estimated with the virtual elevation method by 3 investigators and corresponding off-road speeds were calculated.

The virtual elevation method was highly reliable (typical error = 0.0006, 2.8%; limits of agreement <0.0005, r ≥ 0.98). The mean coefficient of rolling resistance was 0.0219 and differed from 0.0205 to 0.0237 (P < 0.001) between tyres. The calculated differences in off-road speed amounted to 2.9–3.2% (0% slope) and 2.3–2.4% (10% slope) between the slowest and the fastest tyre.

The reliability of the method and the differences in rolling resistance between the tyres illustrate the value of testing tyres for important competitions on a representative ground surface using the virtual elevation method.  相似文献   


10.
In this study, methods for data acquisition, analysis, modelling, and simulation of performance parameters in road cycling on real tracks were developed and evaluated. A simulator was designed to facilitate the measurement in a laboratory environment. The simulation included real height profiles and a video playback that was synchronised with the cyclist’s current virtual position on the track, and online visualisation of course and performance parameters. Field data obtained on mountain tracks in this study were compared with the state-of-the-art mathematical model for road cycling power, established by Martin et al. (J Appl Biomech 14: 276–291, 1998), which accounts for the gradient force, air resistance, rolling resistance, frictional losses in wheel bearings and inertia. The model described the performance parameters accurately with correlation coefficients of 0.96–0.99 and signal-to-noise ratios of 19.7–23.9 dB. It was shown that the mathematical model could be implemented on an ergometer for simulating rides on real courses, providing similar quality measures when comparing field and simulator measurements.  相似文献   

11.
The speed attained by a track cyclist is strongly influenced by aerodynamic drag, being the major retarding force in track events of more than 200 m. The aims of this study were to determine the effect of changes in shoulder and torso angles on the aerodynamic drag and power output of a track cyclist. The drag of three competitive track cyclists was measured in a wind tunnel at 40 kph. Changes in shoulder and torso angles were made using a custom adjustable handlebar setup. The power output was measured for each position using an SRM Power Meter. The power required by each athlete to maintain a specific speed in each position was calculated, which enabled the surplus power in each position to be determined. The results showed that torso angle influenced the drag area and shoulder angle influenced the power output, and that a low torso angle and middle shoulder angle optimised the surplus power. However, the lowest possible torso angle was not always the best position. Although differences between individual riders was seen, there was a strong correlation between torso angle and drag area.  相似文献   

12.
The aim of this study was to describe and validate a new cycling ergometer with original characteristics that allow the measurement of biomechanical variables with position and crank inertial load used by the cyclist in field condition. The braking pedalling force, that permitted the simulation of the resistance to the cyclist in the field, is performed with a brushless electric motor. The validity and the reproducibility of the power output measurements were compared with the widely accepted SRM powermeter. The results indicate that taking into account a systematic error, the measurements are valid compared with the SRM, and the reproducibility of the power output measurements is similar to the SRM. In conclusion, this ergometer is the only one that allows at the same time for (1) valid and reproducible power output measurements at submaximal intensity, (2) utilisation of the personal bicycle of the cyclist, and (3) simulation of the inertial characteristics of the road cycling.  相似文献   

13.
This study analysed the evolution of the physical potential of a twice top-10 Grand Tour cycling finisher (Tour de France and Vuelta a España) whose training was monitored between the ages of 18 and 23 years. The world-class cyclist’s power output (PO) data and training indices were analysed over six years to determine the evolution of his record power profile and training load (TL), which were estimated by using the session rating of perceived exertion (RPE) method. The total annual duration and TL increased through six seasons by 79% and 83%, respectively. The record POs in all exercise intensity zones improved over the six years. The increases in TL, monotony (+34%) and strain (+162%) from the junior category to the world-class level significantly correlated with an improvement in his aerobic potential, which was characterised by an increase in the record POs between 5 min and 4 h. This case study of the performance level and training parameters of a world-class cyclist provides comprehensive insight into the evolution of a cyclist to the top level. Furthermore, determining the record power profile of this athlete over six competitive seasons illuminates the maturation of the physical potential of a top-10 Grand Tour finisher.  相似文献   

14.
This study investigates the rolling and drag resistance parameters and bicycle and cargo masses of typical urban cyclists. These factors are important for modelling of cyclist speed, power and energy expenditure, with applications including exercise performance, health and safety assessments and transportation network analysis. However, representative values for diverse urban travellers have not been established. Resistance parameters were measured utilizing a field coast-down test for 557 intercepted cyclists in Vancouver, Canada. Masses were also measured, along with other bicycle attributes such as tire pressure and size. The average (standard deviation) of coefficient of rolling resistance, effective frontal area, bicycle plus cargo mass, and bicycle-only mass were 0.0077 (0.0036), 0.559 (0.170) m2, 18.3 (4.1) kg, and 13.7 (3.3) kg, respectively. The range of measured values is wider and higher than suggested in existing literature, which focusses on sport cyclists. Significant correlations are identified between resistance parameters and rider and bicycle attributes, indicating higher resistance parameters for less sport-oriented cyclists. The findings of this study are important for appropriately characterising the full range of urban cyclists, including commuters and casual riders.  相似文献   

15.
在对第2届环青海湖国际公路自行车赛全体中、外参赛运动员比赛成绩进行统计处理和全面分析基础上,着重对成绩较好的中、外运动员进行相对成绩、平均排名、速度方差和相对速度方差各项指标的对比分析。结果显示:我国优秀运动员有与国外优秀运动员抗争的实力,而团队整体实力与国外强队仍有一定差距,处于中等水平;在全程速度分配上较为合理,但相对速度能力较差,关键性赛段波动较大,参与激烈竞争的能力远不如国外优秀运动员。  相似文献   

16.
The cadence that maximises power output developed at the crank by an individual cyclist is conventionally determined using a laboratory test. The purpose of this study was two-fold: (i) to show that such a cadence, which we call the optimal cadence, can be determined using power output, heart-rate, and cadence measured in the field and (ii) to describe methodology to do so. For an individual cyclist's sessions, power output is related to cadence and the elicited heart-rate using a non-linear regression model. Optimal cadences are found for two riders (83 and 70 revolutions per minute, respectively); these cadences are similar to the riders’ preferred cadences (82–92?rpm and 65–75?rpm). Power output reduces by approximately 6% for cadences 20?rpm above or below optimum. Our methodology can be used by a rider to determine an optimal cadence without laboratory testing intervention: the rider will need to collect power output, heart-rate, and cadence measurements from training and racing sessions over an extended period (>6 months); ride at a range of cadences within those sessions; and calculate his/her optimal cadence using the methodology described or a software tool that implements it.  相似文献   

17.
Competitive track cycling races are won by milliseconds, and the regulation of an athlete’s power output is an important factor in performance. The aim of this study was to use a mathematical model to predict finishing times for different pacing strategies for the individual pursuit (IP), to identify the optimal strategy in terms of fastest finishing time. Power profiles were generated for a number of common pacing strategies used in cycling, which were based on actual SRM power data for an elite, male, IP cyclist for whom the average power, maximum power, total work done and actual finishing time were known. The total work output was the same for all strategies and the finishing time was predicted using a mathematical model developed previously. The results showed that, of the strategies tested, an initial “all-out” high power acceleration phase followed by a lower constant power output produced the fastest finishing time for a 4,000 m IP event, and that the time spent in the initial high power acceleration phase had a significant effect on performance.  相似文献   

18.
Road cycling performance is dependent on race tactics and pacing strategy. To optimise the pacing strategy for any race performed with no drafting, a numerical model was introduced, one that solves equations of motion while minimising the finishing time by varying the power output along the course. The power output was constrained by two different hydraulic models: the simpler critical power model for intermittent exercise (CPIE) and the more sophisticated Margaria–Morton model (M–M). These were compared with a constant power strategy (CPS). The simulation of the three different models was carried out on a fictional 75 kg cyclist, riding a 2,000 m course. This resulted in finishing times of 162.4, 155.8 and 159.3 s and speed variances of 0.58, 0.26 and 0.29 % for the CPS, CPIE and M–M simulations, respectively. Furthermore, the average power output was 469.7, 469.7 and 469.1 W for the CPS, CPIE and M–M simulations, respectively. The M–M model takes more physiological phenomena into consideration compared to the CPIE model and, therefore, contributes to an optimised pacing strategy that is more realistic. Therefore, the M–M model might be more suitable for future studies on optimal pacing strategy, despite the relatively slower finishing time.  相似文献   

19.
The purpose of this study was to assess the power output of field-based downhill mountain biking. Seventeen trained male downhill cyclists (age 27.1 +/- 5.1 years) competing nationally performed two timed runs of a measured downhill course. An SRM powermeter was used to simultaneously record power, cadence, and speed. Values were sampled at 1-s intervals. Heart rates were recorded at 5-s intervals using a Polar S710 heart rate monitor. Peak and mean power output were 834 +/- 129 W and 75 +/- 26 W respectively. Mean power accounted for only 9% of peak values. Paradoxically, mean heart rate was 168 +/- 9 beats x min(-1) (89% of age-predicted maximum heart rate). Mean cadence (27 +/- 5 rev x min(-1)) was significantly related to speed (r = 0.51; P < 0.01). Analysis revealed an average of 38 pedal actions per run, with average pedalling periods of 5 s. Power and cadence were not significantly related to run time or any other variable. Our results support the intermittent nature of downhill mountain biking. The poor relationships between power and run time and between cadence and run time suggest they are not essential pre-requisites to downhill mountain biking performance and indicate the importance of riding dynamics to overall performance.  相似文献   

20.
自行车运动两人跟骑的空气阻力研究   总被引：5，自引：0，他引：5  
本文通过人、车实体风洞试验,测试两人跟骑空气阻力随风速、距离和侧面迎风跟骑的阻力变化,目的在于了解自行车运动员在骑行中不同骑行姿势的空气阻力变化情况,为自行车运动训练和比赛提供科学的参考依据。  相似文献   

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