Don: Cycling Tech
Ironman Lake Placid has a rich, long history and is an event attractive to both first-time long course athletes and multi-long course finishers. The bike course has a reputation of being very difficult, and depending on where you do most of your riding, the course can be characterized anywhere from rolling to mountainous. The profile of the bike course is as follows (rumor has it that the swim predominately is flat). See: http://www.mapmyride.com/us/lake-placid-ny/ironman-lake-placid-bike-course-route-403905
I've ridden and raced this course many times. If you ride in central and northern New England, you won't have much difficulty with the climbs at Lake Placid. Mt. Wachusetts is considerably harder than any climb at IMLP, and the ride around Quabbin Reservoir also is much more challenging. The difficulty of Lake Placid is one of pacing. The first significant climb is only two miles out of town, so it can be tempting to let adrenalin and excitement take over and ride too hard. Similarly, a lot of athletes get into trouble when they try to make up time pushing big gears hard on the downhills. Most of the potential loss of gain in time will occur in the middle twenty miles or so, and on the gradual stretches of the final climb.
All things being equal, riders should shoot for negative splits on multi-loop courses. Lake Placid, long finish hill and occasionally windy conditions, make negative splits more challenging. A good race strategy would be to use RPE to monitor your pacing, with heart rate and power data being used to provide additional secondary feedback.
The key to keep in mind that the course itself can be divided into a series of segments that roughly can be defined as follows, based on significant climbs:
S1: ~2.1 miles to 7.4: Opening pitch is steep, but once past pull-off area, grade decreased significantly. The bottom is the hardest part of this climb. Start the climb in an easy gear and try to keep well below threshold. Use any slight downhills for recovery--and remember, they are not steep enough to go into a big gear and really push. (Overall RPE 3-4 on the steepest sections)
S2: ~7.8 miles to 14.5: Primarily downhill, some parts fast. Use this stretch for recovery, hydration, fueling, etc. On the steeper downhills, go into a bigger gear and soft pedal to keep the legs moving. HR and watts should drop significantly on this segment. (RPE 1-2)
S3: 14.5 to 23.2. Rolling, but generally trending downhill. Cadence self-selected around normal long course race RPMs. You're mostly racing this segment. RPE ~3.
S4: ~23.2 to 25.4 and 26.4 to 27.8: These are two steep poppers. Gear down for the climb and use the descent between them to recover, fuel, and hydrate. The key for these two climbs it to adopt a relatively steady cadence--don't gear down so much that you carry a high cadence, which will later impact your run. RPE 4-5 on the climbs.
S5: ~27.8 to 42.25: Mostly rolling, with a 200' / 1.5% climb at 37.8. Pay attention to respiratory/HR and cadence. If your heart rate and respiratory rates become labored--difficult to hold a conversation, then go one gear harder and drop cadence by ~5 RPM. This is another segment in which you are consciously racing, and not focusing so much on recovery. RPE 3-4.
S6: ~42.5 to 55: This is your final climb. In general, it's shallower than the opening climb, though there is a steeper pitch ~46.7 to 47.6. View this segment as a long headwind stretch in which you focus on HR and cadence. At the 48 mile mark, the course still trends upward, but at a grade similar to 42 to 46 miles. RPE ~3-4.
Good luck to all who are racing IMLP. Preparing for a race of this nature is an accomplishment in itself. When in doubt, be conservative, always cross reference any pacing schedules or on the bike data with your RPE scale, and (most importantly!) enjoy your race!
[good breakdown of the bike course]
Lake Placid Guide
I've been getting a
number of questions regarding affordable carbon race wheels, so I thought that
I'd share some information with the group.
Industry leaders in carbon wheels include Zipp, Hed, Reynolds, and Enve. These companies make excellent wheels that
have a solid track record. They are
relatively expensive, but their cost is, in part, tied to their
research and development, as well as customer support. If something goes wrong with them, you'll
have direct access to the manufacturer or its authorized representatives. Carbon clincher rims represent sophisticated material design and manufacturing, and these mainstream vendors pioneered the use of carbon fiber in this application.
Most of these wheels
are manufactured in the East Asia, and the wheels are built using each
company's proprietary molds. There are
two manufacturers in China, however, that also sell generic, unbranded carbon
wheelsets. While they don't have the
name cache associated with the mainstream wheel manufacturers, they do offer
very good value for the consumer. These
wheels normally include some of the latest design cues that are common today,
such as wide rim widths to help decrease rolling resistance, toroidal
aerodynamic profiles to help decrease rolling resistance, and structural carbon
builds (rather than attaching a thin carbon fairing to a standard rim, the
fairing is a structural part of the wheel).
Normally, these generic carbon wheels also come with carbon-specific
brake pads and lightweight quick release skewers. These are solid, workman-like wheels--while
other manufacturers might offer hubs that are a bit better in quality, most
users will be satisfied with the generics--and you can't beat the prices, which
run approximately $450 - $500, shipped and delivered. So, for about one-quarter the price, you'll get 90-95% of the performance of high cost, name-brand wheels. The trade-off is that you are dealing with a vendor who is located overseas, without a local representative.
wheels are available via Ebay and are built to order (you'll have your choice
of hub and spoke colors, etc.) and normally are delivered within two
weeks. Vendor communication tends to be
excellent, and your Ebay's terms of agreement protects your purchase in the
unlikely event that something goes wrong with the transaction. While most of the high-end manufacturers will
offer a replacement cost for wheels damaged in use, these are so inexpensive
that you can purchase an entire new set if you damage one of your wheels.
An Ebay search for "carbon clincher wheels" will yield pages of results. I look for a seller with several hundred transactions associated with his/her Ebay identity. In terms of offerings, a very fast wheelset combination would be an 88mm rear wheel, paired with a 60mm front. This will give a fantastic balance of aerodynamics and handling. A more conservative pairing would be 60mm front and rear, 50mm front and rear, or 38mm front and rear. The shallower wheels tend to be lighter, while the deeper wheels tend to be faster. I prefer to run a deeper rear wheel than the front, which stabilizes handling in cross winds.
Other details to consider--most of you will be using SRAM or Shimano for your drivetrain, so make sure that you purchase SRAM/Shimano-compatible rear hubs. Otherwise, double-check to make sure that you are purchasing clincher wheels, or you'll have to buy special tires and glue them to the rims.
Here's a typical listing on Ebay--in fact, I bought this very set of wheels for testing :
Also, check for delivery times and shipping costs. Sometimes shipping is included in the purchase price, while other times it is not. Shipping usually will run approximately $60. Also note delivery times tend to be very conservative and you'll likely receive the wheels well before the stated delivery date.
Generic carbon wheels are a viable option for cost-sensitive cyclists who are looking for good values in their equipment upgrades.
(Note: Click on the images below for close-up view)
There are a good number of tools such as BestBikeSplit, which can help athletes and coaches establish an appropriate pacing strategy for the cycling segment of an upcoming event. These tools are a good start in developing a strategy, but too often they are used as a definitive guide on race day; if any of the original assumptions about variables change or are proven to be inaccurate, then the entire model can result in a less than optimal race performance. A sound pacing methodology will rely on a number of inputs, including day of event record of perceived exertion and likely weather conditions.
BestBikeSplit bases its predictions on a number of data entry elements that helps it create a model
used to predict race day performance.
For the bike, values such as wheel type, wheel width, tire type and
rolling resistance, and riding style all are entered; based on these inputs,
drag coefficients can be calculated for a variety of yaw angles.
These are important numbers, for when placed into the context of rider weight, functional threshold power, and course profile, a predictive strategy can be modeled, the accuracy of which directly depends on the quality of the data entered. While default values for tire rolling resistance and drag coefficient (CdA) can be accepted, more accurate data can be entered based on specific tire testing (each model of tire will have its own rolling resistance value) and wind tunnel or field test aerodynamic data (there is a big variation among riders in efficiency of their aero position).
After these basic inputs are entered, a course can be selected (in this case, Ironman Coeur d'Alene) on which the entered data is run. In addition to equipment, rolling resistance, and CdA details, factors such as rider weight, road surface, likely weather, and functional threshold power are factored into day of the race modeling. The model itself is remarkably detailed and provides such information as anticipated bike split, average yaw angle (useful for specific equipment selection), and anticipated power values:
Additionally, based on its profile, the course itself is broken into specific segments, each with a specific pacing target:
BestBikeSplit is a fantastic tool that presents a large amount of remarkably granular data. And while I have a good amount of confidence in the data returned by this tool, I do not want to confuse precision with accuracy. BestBikeSplit relies on day of event data elements, but it does not take into account the cumulative effect of training on race day performance.
Training is a greater determiner of race day performance than equipment variables (though one can ruin an event with especially poor equipment selection), and the variables that factor into peak event performance are many and need to be recorded over time. There are a number of excellent tools that track short and long term training stresses and training adaptations to help predict the time and duration of a taper leading up to an important event. Phil Skiba's Apollo software enables users to determine their responses to training and predict performance ability on any given day, based on aggregated data. Like BestBikeSplit, the data is remarkably detailed, though its accuracy directly depends on the quality of information collected on an ongoing basis. Users of TrainingPeaks also have access to retrospective and predictive performance data in the form of its Performance Management Chart, though the user will need to place this information within context:
BestBikeSplit, Apollo, and TrainingPeaks all are fantastic tools, and each has their own unique advantages. The value and utility of each, however, directly depends on both the quality of the data used, the size of the data set, and (most importantly) the interpretation and contextualization of the results offered to the user. But establishing a pacing strategy for an upcoming race need not be all that complicated, and what follows are some simple strategies that can be used to help establish a pacing model that you can use the day of your big event.
A key concept to understand is threshold, whether it is heart rate at threshold or power at threshold. The short definition is that threshold is the maximum heart rate (HR) or power that one can sustain over the course of one hour. Most performance calculations are keyed to threshold values. If your race is shorter than sixty minutes, then it is possible to perform above your HR or power values, with the percentage above threshold increasing as the event duration decreases. If your event is longer than 60 minutes, then the percentage of threshold that you should race will decrease as the event increases in duration.
Based on historical data (and adjusted to specific athlete considerations), most Ironman-distance races can be paced between 72-75% of power at threshold value (FTP). A similar range can be established for HR pacing, though HR response is more volatile to heat, hydration, and fatigue. (HR can be used, but with greater generality than power.) Now, all of this sounds easy--if an athlete has a functional power threshold of 285, then setting an average pace of 215 watts should result in a good bike split, while enabling a good run afterward. There are a number of easy to use speed-distance-time calculators (see MachineHead Software and Analytic Cycling) that will predict your event time, assuming that there are relatively few variations in course grade. Throw in hills and wind, calculations can get pretty complicated (see BestBikeSplit, above); add in athlete condition day of the event (tired, sick, well-rested and peaked, etc.), planning becomes even more complex.
Suppose an athlete was preparing for a moderately hilly Ironman event, such as Coeur d'Alene. Further suppose that the athlete is interested in used data to help establish race day pace rather than having specific values dictate pace, believing that a successful performance is predicated on the ability to adapt to changing race conditions.
The first step is to
review the course profile:
The course itself is not horrible--there are some shorter, steep hills, but we are talking about 500 feet of gain. The profile looks way worse than it rides. Two laps will make pacing a bit easier, as the rider can shoot for negative spits. (In this case, negative splits mean that the second lap of the course will be faster than the first. ) The course profile is such that the athlete cannot simply try to average n-watts as a pacing strategy, as watts will be above this value on the climbs, and well below it on the descents. Overall, the athlete will want to average a certain power, but at any given extended period during the ride, power values will vary greatly from this overall average.
Our athlete has a FTP of 285 watts, which means that ideally (assuming adequate rest and recovery) he will average between 215 and 220 watts for the overall ride (this athlete is on the advanced/elite end of the continuum, so he may be able to maintain a pace closer to 80% of FTP (this would be a tough ride and I would not recommend this for his first lap!).
Our next step is to define the median bike split of the top 40 competitors in this athlete's age group. The tight distribution of finish times--notwithstanding the first two outlier performances--are clustered in a tight group, which is indicative of a strong field. Also note that the finish times are relatively slow as compared to the time predicted by the date entered into BestBikeSplit. A snapshot of the 2012 results shows the following splits for this athlete's age group, sorted in ascending order by time:
Checking the results from 2012 suggests that the times--and therefore the conditions of 2013 were not anomalous:
The median split for the top 40 age-specific group performance for 2013 is 5:20:00. This is approximately 12 minutes slower than the prediction made using BestBikeSplit, which is fine--remember, most tools will take into account data at a specific moment in time, which may or may not have a high degree of accuracy.
The historic average high for Coeur d'Alene day of the race is 86F, with a low of 57F. Right now the forecast for 2014 is for sun and 87F, with the low of 68F (Accuweather). The athlete will need to factor in the heat in anticipation for his run, but a lot will depend on humidity day of the event, too.
(Following is from WeatherSpark) Median humidity is approximately 45%, so not a major factor, either. A better measure is dew point--short version is that the athlete should not worry too much about humidity, based on forecast data as of now.
Median cloud cover late June is <10%. There should be a lot of sun. Median wind speed for late June should be ~8mph, which at ground level will read less than 5mph. This low wind speed will impact his cooling, but also will result in low yaw angles (which is good for aerodynamics). Daily max wind velocity is approximately 15mph. Wind should not be a factor.
Based on historic data, a SE wind should be anticipated:
On the course route
itself, the athlete should experience a light quartering headwind, which will
place a premium in holding an aerodynamic position.
Major variations in power output will be associated with elevation changes. In order to achieve a finish time at or below historic medians for his specific age group, the athlete should strive for an overall normalized power of 220, keeping in mind that downhills will depress his power averages. This said, power demands will escalate during the relatively short, but steep climbs, and it is recommend that the athlete does not exceed FTP thresholds beyond 120% when climbing these hills. The course profile can be divided into four segments:
Pacing should be based by segment, with A and C representing segments in which steady output is possible. Using the lap function/average power (or average normalized power) on the athlete's computer and watch will make it easier for him to track power data for pacing. For segments A and C, the athlete should attempt to maintain an average value of 220 watts, normalized power. On segments B and D, the hilly segments, the athlete should not exceed more than 120% of FTP on the steepest of climbs; in these segments, special consideration should be given to using downhill sections for recovery.
Given the fitness level of this athlete, a 5:15 minute bike split is an appropriate goal. As a two lap course, ideally, this athlete will ride a second lap faster than the first. To achieve this split with equal lap times would yield 2:37:30; for the purposes of this race, the athlete is recommended to set 2:40 as a first lap split, and then pick up the pace to realize a 2:35 minute split for lap two. If he is feeling good, he can pick up the pace a bit more for the second lap. In terms of miles per hour--again, used to provide a holistic sense of this pace--a 2:40 split would yield an average speed of 21 mph, while a 2:35 minute split would yield an average speed of 21.7. The ratios of these splits can be adjusted relative to each other, too. And if the athlete is feeling strong, then increasing the speed a full mile per hour the second lap is a possibility (keeping in mind the following marathon, of course!).
Data collection and review is critical during competition, but such information should be used to check trends and to make sure that intensity does not drift too high, thus negatively impacting performance. While data elements such as HR and power offer utility for pacing, perceived exertion still is one of the best ways to monitor performance day of the event, as it accounts for the impact of different levels of intensity.
There are a number of different perceived exertion scales; what matters is that a scale is referenced consistently during workouts leading to one's important event and that the subjective values of the Rate of Perceived Exertion (RPE) scale are cross-referenced to specific HR, power, and other quantitative performance data. In other words, quantitative performance data is used to normalize and adjust one's perceived sense of exertion. By keying in on physiological responses such as HR and respiratory rate, an athlete can establish an accurate sense of the relative cost of an effort. Below is a commonly used RPE scale:
For the first lap of CdA, an RPE of 3-4 is recommended; if the athlete is feeling strong and confident, then lap two's RPE can be bumped to 4 or even low 5 (though low 5 would be risky for the upcoming run). By monitoring breathing patterns, the athlete can establish an effective pace keyed to his specific physiological response day of--and even more importantly, during--the event. Targeting numbers alone might not account for fatigue, nutrition, or hydration concerns, so any numeric value associated with power, HR, speed, or cadence should be placed in one's immediate physiological context. Use the numbers to track trends and for overall patterns (crap, I'm suffering and my watts are way low--I'm very tired!), but focus on consistency in RPE.
For the hills, bumping RPE to 5-6 may be necessary on the steeper and longer hills. But for every instance of a high RPE, there needs to be a corresponding period in which RPE is lower than normal to achieve some level of recovery.
Given the high financial and emotional cost associated with long course events such as Lake Placid or Coeur d'Alene, it is natural to look for assurances wherever possible to maximize one's chances for success. It is important to look at both quantitative and qualitative data when establishing a pacing strategy, and successful athletes are those who are able to adjust their strategies to meet unforeseen situations.
Several of you will be doing Syracuse 70.3 this coming weekend and I thought that I'd share some suggestions regarding the bike course. I grew up north of Syracuse and I raced for many years in the area. I know the course pretty well. There approximately 1,700 feet of climbing on this course--about half of what's on the Quabbin loop--and most of the elevation gain happens in the first twelve miles.
Here's the official course profile:
I've divided the course into three distinct segments: a: the opening climb that runs to the twelve mile mark; b: the middle rolling section, which has some climbs, but none of which are as challenging as the opening twelve miles; c: the final run-in to the finish, which is all downhill.
The first two miles of the course are a gradual descent into the town of Jamesville. You'll cross some railroad tracks--I believe that there are two sets--and turn onto Rt. 173, which is the beginning of the climb.
The climb itself is a series of steps that alternate between 10% and 5%; the actual climb is about 9.5 miles long and tops out on Pompey Hill. (This hill brings back so many memories!) The good news is that most of your elevation gain takes place here, so if you get through the first twelve miles, the rest of the course will be easy ;) You'll know that you're approaching the opening climb when you cross Rt. 20. Again, view this climb as a series of harder efforts for which you'll have some opportunity to recover. The Central New York Triathlon Club has an excellent log of the course's details, which I encourage you to review and print out. You can find it here:
Now, I would approach this course very conservatively. I'd use the first two miles as an opportunity to spin my legs and adapt to the transition from the swim to the bike. I don't want to go too hard, as the climb occurs so close to the start. For the climb, I'd try to keep a relatively comfortable cadence and not push too big of a gear, as I'll want to save my strength for later in the ride. (Try not to let your cadence drop below the low seventies, very high sixties, for instance.) Whenever there is a flat or brief downhill on the climb, I'll recover by soft pedaling a bit--I won't go into a bigger gear right away, even if I get passed. At times, RPE might bump to 6-7 or so; whenever this happens, I try to compensate by doing a stretch at RPE of 2-3. Remember, when you're climbing, sit up, slide back on your seat, open your hips, and relax your upper body.
Once I get to the top the Pompey Hill and consider the remainder of the course, I'd go into a big gear and soft pedal down the steeper, extended stretches of road. As you go, you'll hit some 10% poppers (which will be way easier than 10% on the Computrainer), so gear down to save strength. But when you gear down, don't adopt a ridiculously high cadence--keep it below 90-95.
This segment represents the bulk of your course and it's the segment in which you actively race. Segment A is a matter of conserving energy and minimizing potential loss. For this segment, increase the intensity of your ride, shooting for a RPE of 5-6, which is hard enough for you to be breathing deeply, but you would still be able to speak some sentences. Pay close attention to your respiratory and heart rates, as well as your cadence and how your legs feel. Let your body self-select cadence and don't set an artificial goal for this variable. Rather once you get over the climb and begin cruising on Segment B, take a general note on the cadence that seems most comfortable to you. As you ride, go to a slightly harder gear and slightly lower cadence to lower your heart rate; if your legs start to burn and feel heavy, easier gear and slightly higher cadence. Use this strategy to more evenly apportion your effort.
This is the fun part of the course, as the last 10 miles or so are all downhill. . For a good portion of this segment, I'd be in a relatively big gear and pedal with moderate force. Most likely, my cadence will be slightly lower than on the middle section of the course and my goal is to minimize variations of effort. On the steep downhills, don't feel that you have to stay in your aerobars--you can get pretty aero on your base bars if you drop your upper body down toward your stem. With a couple of miles to go, I'd start preparing for the transition to the run. Don't go into a small gear and significantly increase your cadence, as some might recommend; this only engages your hip flexors, hamstrings, and other cycling-collateral muscles that you'll need to run. Instead, stay in a moderate gear, slow your cadence a bit, and apply more gentle force to the pedals. This will both rest your legs and enable your heart rate to drop.
A number of athletes have expressed concern about the hills in Syracuse, but in truth, the terrain really isn't all that different from Worcester County. In short, if you can do a ride in the Mt. Wachusetts area, you won't have problem with the climbs.
Related to the climbs, a lot of riders ask if they should go with lighter race wheels. In truth, equipment weight lends itself to marginal gains at best and is subordinated in the vast majority of use cases by aerodynamics. The short version is this: always use your most aerodynamic wheels possible, based on weather and wind conditions, even if your aero wheels are much heavier than your light weight climbing wheels. In this line of thought, always use a rear disc if you have one--a rear disc will not be impacted negatively by wind, and you'll always get an aero benefit, even if you're a slower rider.
Today, Elaine completed an interval session that was comprised of four VO2 efforts, followed by one strength-endurance effort. VO2 efforts are short, intense efforts that expend a significant amount of anaerobic power. Both power (expressed in watts) and heart rate are at levels above threshold. By definition, anaerobic efforts don't last long and emphasize energy pathways very different from what are used in aerobic intervals, which take place below threshold. Think of VO2 intervals as well-paced, extended sprints that last no longer than three minutes.
Below is Elaine's HR and power data from the morning's session:
(click for larger view)
Note that Elaine maintained consistent power for each of her VO2 efforts (intervals 1-4), which was approximately twenty-five watts above her normal threshold. (When you are as physically small as Elaine, twenty-five watts is huge.) What's interesting is how her heart rate responded to each of the VO2 efforts. For the first interval, her heart rate was below threshold; for the second and third, her heart rate was just below and just above threshold, respectively. For the fourth interval, her heart rate was clearly above threshold.
Also note how her heart rate slopes upward during the course of each interval. Heart rate response lags behind effort, and if Elaine tried to ping her heart rate near threshold in the first minute of her three minute effort, she would have started too hard and would not have been able to complete the full duration of the interval. The upward sloping heart rate curve is indicative of a properly paced VO2 effort. If the effort was done at a lower specified intensity, heart rate still would slope upward, but the curve would be much shallower.
Each VO2 interval was three minutes in length, and recovery (~60% of FTP) was five minutes. Given that her heart rate gradually escalated for each effort might suggest that recovery could have been lengthened by another minute. But because her power curves were consistent across all four intervals, the upward heart rate drift most likely can be attributed to a build of heat. (I've always have said that Elaine is hot!) Short version, I would not have changed any of the parameters associated with Elaine's VO2 intervals.
After the fourth VO2 effort, Elaine ended her session with an eight minute high resistance (100% FTP), low cadence (70-75 RPM effort). Note how there is minimal variation in power, as she's riding at a lower intensity (at FTP, not above); also note how her heart rate curve is shallower and peaks lower than those for her VO2 efforts. Again, this is a perfectly paced effort.
Looking at the data above, this was a successful session. Elaine worked on top-end power, as well as low-end strength. She gained the most benefit from VO2s 2-4, and her strength-endurance interval. Her first interval was important, but mostly as preparation for the following efforts.
We are in a golden age of options for cyclists interested in assessing performance and structuring workouts through the use of power. Not too long ago, power-guided training and racing was the province of a few: always very expensive and often difficult to use, power meters primarily benefited those who were willing to take the time to understand the quirks of their devices and able to ensure that they were properly configured and calibrated to improve their accuracy. Today, power meters are much simpler to use, they have gone down in cost, and they tend to be very reliable tools for even novice and intermediate cyclists. Power is an important metric for cyclists to track, as it provides insight into how much work was done on the bike and, when viewed over time, how fitness and performances are impacted by training.
While the cost of power meters has dropped significantly in the past three years, it still can be a barrier for many riders. New devices from Stages and PowerTap can be had for less than $800 (plus the cost of a computer/head unit); the average price point seems to have settled around $1,600, which is the cost of a decent new TT bike, or a very good-to-excellent used TT bike. And if a rider has multiple bikes, then the cost of ownership for training with direct force power meters goes up, either through the real cost of additional units or mounting hardware, or through time and labor associated with swapping power devices from one bike to the next. Not every rider will want to spend money for a dedicated power meter, but there are options available for those interested in receiving some of the benefits of training with power, without the high cost.
There are three categories of power-based training tools available today: direct force power meters; opposing force power meters, and virtual power calculations. It's important to understand the benefits and potential disadvantages of each system before making an investment in this area.
Direct force power meters represent "original" power measure technologies. Normally based on strain gauges or similar concepts, direct force power meters measure how a part on the bicycle deforms under force. This deformation can seen in how crank arms and pedal spindles bend, or how rear axles and bottom brackets twist when a rider presses down on the pedals. Direct force power meters represent mature technologies that are highly precise and accurate. While each manufacturer might implement their technology in a unique manner, all function in much the same way. SRM, PowerTap, Quarq, and Stages are among the main competitors in this area. In general, direct force meters are considered the gold standard in power meters.
SRM--the original power meter
Opposing force power meters take a different approach. Rather than directly measuring the deformation of a specific part on the bicycle, they instead calculate opposing forces on the rider, such as the grade of the road, the rolling resistance of the tires, the speed of the rider, and the force of the wind. While this approach is simple in concept--Newton describes it in the form of force = mass * acceleration--the difficulty is in the details. In order to get an accurate and repeatable measures of power based on opposing forces, many complex calculations need to be completed very quickly, and the quality of the calculations depends on the accuracy of initial assumptions. For example, for an opposing force power meter to work acceptably, the weight of the rider and bike must be factored in, as well as the aerodynamic drag of the rider's position (which can be problematic, as this value will change depending on the clothing a rider wears, equipment that is used, and position on the bike).
Fortunately, processing power today is inexpensive and modeling is sophisticated, so opposing force power meters do represent a viable alternative to their direct force cousins. For most riders, the biggest practical difference between direct force and opposing force power meters is granularity: direct force power meters are excellent at measuring short and variable duration of power, such as what occurs when sprinting, while opposing force power meters do better for longer, more sustained efforts. In other words, when properly configured, opposing force power meters are remarkably consistent with direct force models. iBike's Newton is state of the art in opposing force power meters, and its purchase cost and overall cost of ownership can be much lower than that of a direct force power meter.
iBike opposing force power meter
Virtual power meters take the general concepts associated with opposing force power meters and take them to a higher level of abstraction so that power is calculated based on mathematical assumptions. Services like Strava, TrainerRoad, and Tour de Giro all provide power calculations based on your performance. Virtual power meters tend to be most accurate when rider performance is steady and there are few environmental variations. For instance, it's relatively easy to calculate power associated with a steady climb, as speeds will be low (smaller aerodynamic impact) and effort steady; for long rides on variable terrain and/or in changing winds, calculations become less precise and more advisory. Factor in additional variables such as aerodynamics and rolling resistance, power calculations become more suggestive. Virtual power is a great option for providing a rider with a very general, high-level sense of overall performance, but it is not accurate enough or replicable enough to rely on exclusively for structured training.
Increasingly, serious riders are seeing the benefit of indoor structured training, and power calculation plays an important role in increasing the efficacy of a rider's sessions. A standard trainer and power meter can be used for structure interval workouts and guided tempo and threshold sessions; the same equipment that is used to measure power outdoors is used for indoor training. And if one does not have a direct force power meter, then all one needs to do to train with power indoors is to purchase an inexpensive Ant+ cadence and speed pickup to use in association with an indoor trainer. Most manufacturers provide what's called a power curve associated with their popular trainer models. A power curve is an estimation of the amount of power that needs to be generated to achieve a specific wheel speed as expressed in miles per hour. Power curves will vary with specific trainer settings, as well as with other variables such as tire inflation, the amount of pressure the trainer's roller applied to the wheel, and even the temperature of the air in the room in which training takes place.
Power curve for Cyclops SuperMagneto Pro trainer
Online services such as TrainerRoad and Tour de Giro base their power assumptions on the power curves of specific trainers, but these values should be seen at best as approximations, as they neither are accurate or replicable. This is not to say that TrainerRoad or Tour de Giro are not useful for indoor training--on the contrary, they offer the opportunity for highly structured workouts in a relatively consistent environment, provided that one understands that the data associated with the training sessions is descriptive and qualitative in nature. The data is not accurate or replicable enough to establish a precise value for thresholds or other training zones.
Another option for training with power indoors is a device like a Computrainer, which calculates power directly and which can be calibrated to zero out the importance of the trainer's press-on force at the rear wheel. What differentiates the Computrainer from riding a standard trainer with a direct force power meter or with virtual power is the ability to do ergometer-based efforts. What an ergometer will do is force a rider to produce a specified amount of watts, regardless of a number of variables: if an ergometer is set for 300 watts, then the rider must produce 300 watts, no matter the gear being used, cadence selected, or speed of the wheel. Think of ergometer workouts as training with power in reverse--rather than trying to hit specific power values, the rider is forced to perform at a certain level of intensity, no matter the motivation or focus. Power meter/trainer intervals have greater scope for variability during individual efforts, as the rider has to focus consciously to maintain an even pace at an appropriate output. In terms of return on exercise investment, it is difficult to beat ergometer-based interval sessions.
Computrainer--perhaps the best of the best in indoor power training
While all of this might sound complicated, the takeaways are relatively simple.
Like many things in life, take time to think about how you will use your power data. If you're looking for general trends and are not interested in using your power data for detailed performance testing or aerodynamic field testing, then virtual power may be worth a consideration. If you are on a relatively tight budget and are willing to take care in setup and configuration, then an opposing force power meter might be a good match. If you are seeking accuracy and precision to guide your training and assess your performance, then a direct force power meter or a more sophisticated indoor system like a Computrainer would be your best investment.
With the advent of relatively affordable power meters and a range of indoor trainers that directly measure force, it is easy to collect a large amount of data associated with individual training sessions. At first, this information can be daunting, but a general understanding of how this data might be viewed will go a long way toward demystifying the analysis of your performance.
The problem with training data, and especially when it includes power and heart rate (HR), is that the numbers appear precise, and we assume that the specificity of these numbers would be useful in understanding our workouts. While there are times in which precise numbers are important (for instance, in establishing thresholds), identifying and analyzing trends offer greater utility. Remember, a data point represents specific information at a specific period in time; what we want to track are patterns over time, which tell us how were are performing.
In the following example, a cyclist was asked to complete the following workout:
The cyclist reported that this was a strong session and uploaded his data file.
On first view, this graphical representation of the workout looks very complicated. But it really isn’t all that bad, especially if we peel away information that offers little value for analysis.
Here’s the color code for the different graphs:
As this session was performed indoors on a trainer, we don’t need to worry about altitude or temperature. Outside, these variables can have a big impact on performance, but indoors they can be removed. Here’s a clearer cut of the data, with altitude and temperature hidden:
Okay--this looks a little more manageable. Because this is an indoor trainer ride, we also don’t need to worry about wheel speed, which is removed from the following view:
What remains is data associated with cadence, heart rate, and power. Rather than looking at specific numerical values at this time, I first look for any patterns or outlying features. For example:
So far, then, the data tells me that the cyclist did a strong, consistent first interval at (or slightly above) AT, while he struggled a bit with the second. Because the level of intensity was lower for the third interval (as intended), variances in watts and cadence narrowed back down. What I know so far is that the cyclist did two strong intervals, but that the second interval was a little harder than the first.
While it’s fashionable for some cyclists to disregard HR data associated with their rides, it actually provides useful insight. In very simple terms, power is an expression of the work being done on the bike, while HR describes how we respond to this work. There are a good number of variables that help shape our HR responses, but when taken holistically, HR provides interesting insight.
The following has all data removed from the display, except for heart rate:
Note the HR curves associated with each interval. For the first interval, HR increases steadily for the effort. For the second, HR is almost at the same level as the conclusion of the first, and it rapidly rises for the duration of the effort. This rapid response (and particularly the sharp HR peak at the end of the second interval) suggests that the cyclist was only partially recovered from the first effort and that he struggled at the end to accelerate at the end of the interval to meet his target watts. The HR curve for the third interval is both flatter and lower, which is expected for the lower intensity prescribed for this effort. For the third interval, HR response is clear, but steady, and well below the levels of the first two; this was a perfect curve for the effort attempted.
I can confirm my observations by superimposing cadence curves (yellow) on HR (red):
In this view, the only items of note are that there was greater cadence variability in the second interval, as well as a slightly higher overall average cadence. Variations in cadence and overall RPMs impact HR: the greater the variations of cadence and the higher the RPMs, the greater the potential impact on HR. Note how steady both HR and cadence is for the final, lower intensity, lower cadence effort.
Finally, I can look at HR and power superimposed on the same graph:
Again, no surprise in this view. As the duration of the interval increases, HR also increases. For intervals one and three, power is relatively consistent and has low variability. Interval two is the one outlier in that there was greater variability in power (and remember from above, also in cadence) and a sharper increase in HR. My summary, then, is:
In all of the analysis above, note that there was no reference to specific data values and that we focused on trends and anomalies in the graphs. If we stopped at this point, we would have a useable (and useful!) understanding of a workout that can be used for future planning and assessment purposes.
Now, the next step for me would be to look at specific data values to deepening my profile of the session. This process also is straightforward, especially after a qualitative analysis of the same information. But this is a topic for another article.
Data analysis need not be complicated or scary. If you look for patterns in how the data is graphed, you’ll gain greater insight into your performance Remember, keep in mind that you always want to look at the big picture first. Even if you don’t go into more detail in your analysis, you will learn more about yourself and how to assess your training and race sessions.
I have written two earlier articles on the importance of crank length and the variables that one might consider when selecting a crankset that will help optimize performance. Until relatively recently, most cyclists would adopt a rough proportional scale when identifying appropriate crank lengths--tall riders used long cranks (normally between 175 - 180 millimeters in length), small riders used short cranks (normally between 165 - 170 millimeters), while those riders in-between used mid-length cranks (170 - 172.5 millimeters). Some riders further refined this rule of thumb, going to slightly longer cranks if they were going to be doing events that skewed toward big gear, high force efforts, such as time trials. More recently, researchers have begun examining crank length in the context of bike fit and physiological parameters. I wrote about the relationship between crank length and hip angles in an earlier post and discussed the benefits of short cranks in terms of body position and power production; in another, I discussed how crank length also can be related to type one and type two muscle fiber recruitment. This entry will take a look at the relationship between crank length and overall pedaling efficiency, and how crank length can positively impact power production in ways that initially might be seen as counterintuitive.
Okay--to start, we need to think about how power is produced. Power a measure of how much work we're doing on a ride--the higher the power (normally expressed in watts), the harder we're working. Power is based on the factor of two variables:
There are lots of way of generating power: you can push down very hard on the pedals at a relatively slow cadence, which privileges muscle strength over cardio fitness; or you can push down relatively lightly on the pedals, but turn them at a high cadence, which privileges cardio fitness over muscle strength. You can read more about cadence and power production here.
The goal of performance cycling is to product as much power as possible with as little physiological cost as possible. Riding exclusively at lower cadences can cause premature muscle fatigue, negatively impacting performance; riding at too high of a cadence can result in excessively high heart and respiratory rates, with lead to premature physiological fatigue. The key is figuring out how to balance the variables of force and cadence in a way that's sustainable for the duration of the event.
One of the best ways to visualize the relationship between pedal speed and crank length is to image a weight attached to the end of a two foot cord. The cord is spun in a circle at a constant rpm, say sixty revolutions per minute; if the weight is attached to a two foot cord, we can calculate the speed that the weight must travel to match the sixty rpm value. Next, imagine that the same weight now is attached to a six foot cord and is then spun at the same rpm. Because the cord is three times longer, the circle that the weight will travel has a radius that's also three times longer--in simpler terms, the longer the cord, the bigger the circle the weight will travel when spun 360 degrees.
Remember, though, in this example that while the length of the cords attached to the weight varies, the rpm of the spinning weight remains constant. So, in order for the weight to move at the same rpm, the weight on the long cord has to travel much faster than the weight attached to the short cord. Both weights have the same rpm, but each travels at a different speed to achieve this common value.
In terms of pedaling, we tend to focus almost exclusively on rpm, forgetting that pedal speed is another important factor in our calculations. For a given rpm, the pedal must travel faster when using long cranks than short; to pedal at 90 rpm on my 175mm cranks, my foot has to travel much more quickly than it would if I were to use 165mm cranks. Think of the pedal and crank relationship as we did the weight and cord, described above:
To achieve the same rpm, pedal A has to travel faster than pedal B.
In practice, this means that many riders experience an increase in cadence when they shift to shorter cranks. The reason for this is that they have adapted to the higher foot speed associated with longer cranks to achieve a given rpm; until full adaptation occurs with shorter cranks, cadence will be higher. Higher cadences also mean that less force needs to be applied to the pedals to achieve a given power value. Less force means that muscle strength--which fails more quickly than cardio fitness--is retained for a longer period of time.
Putting all of this together really isn't that complicated. Shorter cranks means that one can ride in an aggressively aero position without losing power; shorter cranks also are better suited to the recruitment of slow twitch muscle fibers, characteristic of most endurance athletes; and shorter cranks enable higher cadences, which can translate into increase power at lower muscular cost.
In the ideal world, one might consider training on long cranks and racing on short cranks as a way to maintain high pedal speed in competition. Short cranks are a viable option for most riders, and research has demonstrated that very short cranks will not negatively impact power production. Today, it is not uncommon to see elite athletes with crank lengths 165mm or shorter. Short cranks are worth consideration by age group competitors as well.
The single most important factor in achieving optimal aerodynamics on the bike is to focus on the position of your body. The latest and greatest wheels, frames, and helmets contribute no more than 20% of a rider's total aerodynamic drag under the best of conditions; before investing your funds on equipment that may or may not work for you, consider your bike fit first.
In general, there are no secrets to establishing a solid aerodynamic position on the bike: You want your head and shoulders low enough to reduce your front profile into the wind without significantly compromising your power and you want your hands and arms fairly close together. That’s it--sounds simple, doesn't it? The challenge is in how to meet these two objectives.
There are two physiological factors that impact on our aerodynamic positioning: our body size and morphology; our flexibility. In order to get down into a low aerodynamic position and still be able to ride powerfully, one needs to have fairly good hip, lower back, and hamstring flexibility. A critical component of this equation is the angle described by the top of a rider's thighs and his/her torso (this is called 'hip angle"). In the stick image below, the red arc indicates hip angle:
Now, the tighter one's hip angle, the more one feels constricted when riding in an aero position, and in extreme cases, a rider's thighs actually may hit the abdomen or chest while pedaling. Additionally, tight hip angles can reduce the amount of power generated by a rider because it is more difficult to move the crank over the top of the top of the pedal stroke (tight hip angle=less leverage).
Achieving an aero position on a road bike is difficult in that most road frames are designed to be ridden with the seat set back behind the cranks. This design works very effectively when riding with traditional handlebars--it really hasn't changed in over one hundred years--but it doesn't work so well when aerobars are added to the equation. Adding aerobars to a road bike significantly tightens the rider's hip angle:
While one can establish a remarkably aero position with aerobars on a road bike, the tradeoff most likely will be loss of power, lower back and hip pain, and potentially compromised bike handling.
The reason why triathlon bikes have steep seat angles (i.e., the seat is positioned much more forward of the crank than on road bikes) is to enable a rider to get down into a low aerodynamic position without constricting the angle of the hip. Try visualizing it like this: one can keep the hip angle the same when lowering the aerobars by moving the seat forward, which will rotate the entire body clockwise. Because the body itself is being rotated forward, the hip angle remains the same, while the arms drop lower:
Figure 2: Aero position on triathlon bike:
Figure 3: Aero position on a road bike:
In figures two and three, note the relatively positions of the seat and crank: the more forward the seat, the lower the aero position can be, while preserving a relatively open hip angle. The take away is relatively straightforward: in most instances, if one wants to use traditional aerobars and achieve a good aerodynamic position, then a triathlon frame with a forward seat position is a must. Putting aerobars on a standard road bike will result in either a significantly impinged hip angle (not great for power or comfort) or aerobars placed so high as to negate any aerodynamic advantage that they might offer.
But suppose you already have a triathlon bike and want to get lower to be more aerodynamic, or suppose you already have a pretty good aero position but want to get a little more power. The next variable to look at after seat position is crankarm length.
There are many studies that indicated that crank length in itself does not measurably impact power output. Traditionally, long crank arms have been used for time trials because they provide, the argument goes, more leverage than short crank arms; the more leverage one has, the bigger the gear one can push at a given cadence, which means more speed. The problem with long crank arms is that they describe a much bigger circle that a rider's legs must travel for each revolution of the crank; making this circle bigger effectively tightens the hip angle, as the leg must travel higher in relationship to the torso to complete one pedal revolution.
If an open hip angle is advantageous to power production and comfort, and if one wants to maintain or achieve a lower aerobar position, then it would make sense to go with a shorter crank arm length, especially as short cranks have little to no impact on overall power production. In other words, by moving from a long crank to a short crank, one can either open up the hip angle for one's current position, or realize some play to drop the aerobars for a more aggressive position. But in order to go the same speed with shorter cranks, the rider will need to slightly increase his/her cadence to compensate for the loss of gain.
This is where a little math is needed, but it's not so bad and you're almost there. Traditionally, riders have measured gear size by expressing it as a ratio (which is not too intuitive) or distance traveled per revolution of the crank (called "development"). For example, suppose that you're riding a bike with a 50 tooth chainring and a 25 tooth cassette cog; this combination can be expressed in a variety of ways:
The problem with each of the expressions above is that they don't take into account the effect that crank arm length has on gearing. The concept of gain ratio factors in the circle described by the crank; while the math is fairly simple, the real take away is that long cranks have a greater impact on overall gearing than short cranks. Here's an example based on my own riding:
I've been using 175mm cranks for lots of years for TTs; I prefer a large gear and a slower cadence (~75-80), which has tested well for me in terms of power and HR. I'm also 5'7" tall, which makes 175mm cranks long for me by most traditional standards.
Okay--if I figure out the gain ratios for 175 and 170 cranks, I get the following approximate values for a top gear:
What this tells me is that while the numbers say that I'd need to spin slightly faster for the same gearing to be at the same speed if I went to shorter cranks, the difference would only be 2%--which isn't very much.
But--by going with a shorter crank, I would reduce my hip angle, which means that I either can get lower in front for a more aero position (which I don't need to do), or I should be able maintain my current position, but push the same watts more efficiently. In other words, it looks like a shift to a shorter crank length for one my height might have more value than the benefits traditionally associated with using longer cranks for TTs.
What does all of this mean?
Again, there are many variables that factor into a good, aerodynamic bike position and it is worth the time and expense to visit a professional fitter to help you get started. One you have a solid baseline position, you'll be able to experiment with seat position and crankarm length to further optimize your performance.