This article needs additional citations for verification .(March 2014) |
This article possibly contains original research .(November 2016) |
A cycling power meter is a device on a bicycle that measures the power output of the rider. Most cycling power meters use strain gauges to measure torque applied, and when combined with angular velocity, calculate power. [1]
The technology was adapted to cycling in the late 1980s and was tested in professional bicycle racing i.e.: the prototype Power Pacer (Team Strawberry) and by Greg LeMond with the SRM device. This type of power meter has been commercially available since 1989. Training using a power meter is increasingly popular.
Power meters generally transmit data wirelessly and can be paired to a bike computer, smartphone, or smartwatch. By providing instantaneous feedback to the athlete, and by allowing more precise analysis of rides, power meters can be a useful tool for training.
Older cycling power meters use a set of wires to transmit power information to a computer mounted on the bicycle; this system has a serious disadvantage of having fine electrical cables being run all over the bicycle, making it harder to clean as well as using a fair number of fasteners to hold them up. However, since 2009 there is a general trend to move towards wireless systems. Power meters generally transmit data over ANT+ or Bluetooth Low Energy protocols and can be paired to standard bike computers that display information about the power output generated by the rider.
This section possibly contains original research .(May 2017) |
Power meters provide an objective measurement of real output that allows training progress to be tracked very simply—something that is more difficult when using, for example, a heart rate monitor alone. Cyclists will often train at different intensities depending on the adaptations they are seeking. A common practice is to use different intensity zones. When training with power, these zones are usually calculated from the power output corresponding to the so-called lactate threshold or MAP (maximal aerobic power).
Power meters provide instant feedback to the rider about their performance and measure their actual output; heart rate monitors measure the physiological effect of effort and therefore ramp up more slowly. Thus, an athlete performing "interval" training while using a power meter can instantly see that they are producing 300 watts, for example, instead of waiting for their heart rate to climb to a certain point. In addition, power meters measure the force that moves the bike forward multiplied by the velocity, which is the desired goal. This has two significant advantages over heart rate monitors: 1) An athlete's heart rate may remain constant over the training period, yet their power output is declining, which they cannot detect with a heart rate monitor; 2) While an athlete who is not rested or not feeling entirely well may train at their normal heart rate, they are unlikely to be producing their normal power—a heart rate monitor will not reveal this, but a power meter will. Further, power meters enable riders to experiment with cadence and evaluate its effect relative to speed and heart rate.
Power meters further encourage cyclists to contemplate all aspects of the sport in terms of power because power output is an essential, quantitative link between physiological fitness and speed achievable under certain conditions. A cyclist's VO2 max (a proxy for fitness) can be closely related to power output using principles of biochemistry, while power output can serve as a parameter to power-speed models founded in Newton's laws of motion, thus accurately estimating speed. [2] The joint application of power meters and power models has led to increasingly more scientific analyses of riding environments and physical properties of the cyclist, in particular aerodynamic drag.[ citation needed ]
Dual-sided power meters, generally direct applied force or pedal power meters, can measure the power generated individually by the left leg and the right leg. The resulting data allow monitoring of the dominant/non-dominant leg ratio and observe how it varies in relation to different racing and fitness conditions. This can be useful to correct penalizing imbalances and in post-traumatic rehabilitation programs.
Most cycling power meters use strain gauges to measure torque applied, and when combined with angular velocity, calculate power. Power meters using strain gauges are mounted in the bottom bracket, rear freehub, or crankset. Certain newer devices do not use strain gauges and instead measure power through handlebar-mounted units that utilize the principles of Newton's Third Law by measuring a cyclist's opposing forces (gravity, wind resistance, inertia, rolling resistance) and combining these with velocity to determine the rider's power output.
Crank and spider based power meters measure the torque applied through both pedals via strain gauge/s positioned within the crank or crank spider. A calculation of power is derived from the deflection of the strain gauge/s and pedaling cadence. While most crank-based power meters measure the power output of one leg only or need a second sensor to measure the power output of both legs, the spider-based power meters always measure the total power output of both legs.
These units require specific cranks or cranksets but can be relatively simple to interchange between bikes, depending on compatibility.
Pedal-based power meters can be located either in the pedal axle or in the pedal body. This type of cycling power meter measures the cyclist’s force exactly where it is applied, through one or both pedals. Power meters with sensors on both pedals can provide a real dual-sided power measurement, that is power data gathered individually on both legs. This feature is useful to observe and correct penalizing differences in performance between legs.
Power meter pedals are easy to install and swap across bikes.
Bottom bracket power meters rely on the torsional deflection in the BB shaft. This is done by the shaft having a disc at each end with perforations. These perforations are detected using non-contact photo-electric sensors that detect when torque is applied to the left pedal and then doubled. Data is sent digitally to a handlebar mounted computer unit.
These units are difficult to interchange and require a different bottom bracket unit for each bike.
A freehub power meter uses the same strain gauges that are present in the crank power meters, but it is located in the rear wheel hub and measures the power at the rear wheel. The power measured by a freehub power meter will be slightly less than the power measured by a crank-based power meter due to power losses in the chain, pedals, and bottom bracket. Because freehub power meters are built into the rear wheel, it is simple to interchange them among bikes so long as the wheels are compatible.
At the heart of chain units is essentially a guitar pick-up that mounts to the cycle's chain stay. The pick-up detects chain vibration from which it calculates chain tension which, along with chain speed, gives power output. Finnish company Polar was the first to bring a chain-based power meter to market.
Opposing force power meters measure hill slope (gravity), bike acceleration (inertia), and sometimes, wind speed. From this, power can be indirectly calculated.
A bicycle, also called a pedal cycle, bike, push-bike or cycle, is a human-powered or motor-assisted, pedal-driven, single-track vehicle, with two wheels attached to a frame, one behind the other. A bicycle rider is called a cyclist, or bicyclist.
A tandem bicycle or twin is a form of bicycle designed to be ridden by more than one person. The term tandem refers to the seating arrangement, not the number of riders. Patents related to tandem bicycles date from the mid 1880s. Tandems can reach higher speeds than the same riders on single bicycles, and tandem bicycle racing exists. As with bicycles for single riders, there are many variations that have been developed over the years.
The crankset or chainset is the component of a bicycle drivetrain that converts the reciprocating motion of the rider's legs into rotational motion used to drive the chain or belt, which in turn drives the rear wheel. It consists of one or more sprockets, also called chainrings or chainwheels attached to the cranks, arms, or crankarms to which the pedals attach. It is connected to the rider by the pedals, to the bicycle frame by the bottom bracket, and to the rear sprocket, cassette or freewheel via the chain.
A bicycle chain is a roller chain that transfers power from the pedals to the drive-wheel of a bicycle, thus propelling it. Most bicycle chains are made from plain carbon or alloy steel, but some are nickel-plated to prevent rust, or simply for aesthetics.
Indoor cycling, often called spinning, is a form of exercise with classes focusing on endurance, strength, intervals, high intensity and recovery, and involves using a special stationary exercise bicycle with a weighted flywheel in a classroom setting. When people took cycling indoors in the late 19th century, whether for reasons of weather or convenience, technology created faster, more compact and efficient machines over time. The first iterations of the stationary bike ranged from strange contraptions like the Gymnasticon to regular bicycles placed atop rollers.
A track bicycle or track bike is a bicycle optimized for racing at a velodrome or outdoor track. Unlike road bicycles, the track bike is a fixed-gear bicycle; thus, it has only a single gear ratio and has neither a freewheel nor brakes. Tires are narrow and inflated to high pressure to reduce rolling resistance.
A stationary bicycle is a device used as exercise equipment for indoor cycling. It includes a saddle, pedals, and some form of handlebars arranged as on a (stationary) bicycle.
A fixed-gear bicycle is a bicycle that has a drivetrain with no freewheel mechanism such that the pedals always will spin together with the rear wheel. The freewheel was developed early in the history of bicycle design but the fixed-gear bicycle remained the standard track racing design. More recently the "fixie" has become a popular alternative among mainly urban cyclists, offering the advantage of simplicity compared with the standard multi-geared bicycle.
Gear ratios of bicycles are relative measures of bicycle gearing giving an indication of the mechanical advantage of different gears, which combined with the wheel diameter determines how far the bicycle advances per pedal or crank revolution.
A cyclocomputer, cycle computer, cycling computer or cyclometer is a device mounted on a bicycle that calculates and displays trip information, similar to the instruments in the dashboard of a car. The computer with display, or head unit, usually is attached to the handlebar for easy viewing. Some GPS watches can also be used as display.
On a bicycle, the cassette or cluster is the set of multiple sprockets that attaches to the hub on the rear wheel. A cogset works with a rear derailleur to provide multiple gear ratios to the rider. Cassettes come in two varieties, freewheels or cassettes, of which cassettes are a newer development. Although cassettes and freewheels perform the same function and look almost the same when installed, they have important mechanical differences and are not interchangeable.
Biopace is a tradename for a type of ovoid bicycle chain ring manufactured by Shimano from 1983 to 1993 The design was intended to help overcome the "dead zone" where the crank arms are vertical and riders have little mechanical advantage.
In cycling, cadence is a measure of rotational speed of the crank, expressed in units of revolutions per minute. In other words, it is the pedalling rate at which a cyclist is turning the pedals. Cadence is directly proportional to wheel speed, but is a distinct measurement and changes with gearing. In other words, the gearing changes the ratio of the crank's rotational speed (cadence) to that of the drive wheel's rotational speed.
A front freewheel or freewheel crank is a freewheel mechanism used on some bicycles which enables the drivetrain of the bicycle to continue spinning while the rider rolls, but stops pedaling. Unlike regular bicycles, a front freewheel can make it possible to shift gears using a derailleur while the rider is coasting if paired with a fixed rear hub or a freehub with a slight resistance in the freewheel mechanism, which causes the chain to continue to spinning with the wheel rotation.
Bicycle gearing is the aspect of a bicycle drivetrain that determines the relation between the cadence, the rate at which the rider pedals, and the rate at which the drive wheel turns.
Bicycle performance is measurable performance such as energy efficiency that affect how effective a bicycle is. Bicycles are extraordinarily efficient machines; in terms of the amount of energy a person must expend to travel a given distance, cycling is calculated to be the most efficient self-powered means of transportation.
Schoberer Rad Meßtechnik (SRM), or Schoberer Rad Messtechnik, is a company which created the first cycling power meter. Formed in 1986 by Ulrich Schoberer, the firm's name literally means "Schoberer’s bike measurement technology." The SRM Powermeter uses built-in strain gauges to determine the power, in Watts, that the cyclist outputs to the bicycle cranks and chainring.
Bicycle drivetrain systems are used to transmit power on bicycles, tricycles, quadracycles, unicycles, or other human-powered vehicles from the riders to the drive wheels. Most also include some type of a mechanism to convert speed and torque via gear ratios.
Stages Cycling is headquartered in Portland, Oregon, with manufacturing and R&D based in Boulder, Colorado. In 2012 Stages Cycling launched its first cycling power meter, where power is measured exclusively on the left-crank arm. Now they have a complete line of outdoor cycling power meters compatible with a range of cranks along with an indoor cycling bike.