Friday, March 07, 2008

Some Thoughts on Recreational Cycling

(Introductory material to the next couple of blog posts to start off 2008.)

Okay, I admit it, I used to be a bike racer. But that was many years ago, so don't hold my youthful antics against me. I hope that doesn't put too bad a taste in your mouth or drive you away from reading through this stuff... Then for many years I didn't even ride my bike at all. Got back into it (a long story which I'll save for a bottled evening) in the fall of 2002, and didn't it hurt! the first 5 km darn near kilt me, and me not even a Scot! Anyways, discovered how much I still enjoyed it and so have been spending more and more time each year on the thing(s: I have accumulated a few new steeds to complement my faithful old Banani).

So, for a few years I just rode around by myself, chalking up the km's and getting fitter. Then did some internet browsing and came across the Centennial Cycling Club website, and eventually managed to marry our schedules so as to attend a ride or two in late '06, and a number of rides in '07.

The impetus for this particular family or set of blog blurbs (this plus the next 2 below and maybe the odd other bit later) is some thinking that cycling with a recreational club has set me off on, plus having come to realize that I myself have been going about building my cycling fitness ineffeciently (some might say "all wrong" and I might tend to agree, but I have been getting more capable over the past few years, just probably not with the progress that I could have been making). I'm not sure how organized this set of blurbs will be, I seem to have lost my former knack for linear logic in writing, but stick with me and you may find something you might want to make use of... well, truthfully I am pretty sure this isn't very well organized at all.

Warning! I do talk about efficiency on the bike, which to many recreational cyclists may seem pointless. But really, think about it-- a bit of extra efficiency on the bike tour may mean a bit more distance covered each day, or a fresher start the next day (whether back on the bike or off to work), or less fatigue allowing more enjoyment of scenery and ride (and bedroom).

And another wee caution, I am writing about stuff that I am not an expert in, just a "user". In the interests of simplicity/clarity and approachability I do leave things out and summarize. There is no attempt deliberately to mislead, and if I do mislead anyone with this I do apologize! Further reading of the real experts is encouraged of course.

Last, before wading into the meat of it all, I encourage use of the the "Comments" facility of the blog when you have comments which may be pertinent to other readers of the material.


Bicyclist's Best Buddy

A spare inner tube?

Perhaps a pump?

Food and drink?

A chain tool?

All of those in it's time or place, but my really best bicycling buddy is a Heart Rate (HR) Monitor.

One of the things I did the first spring after I dusted off the bike again was to buy a HR Monitor: just a basic creature which showed me my current heart rate and kept track of the amount of time spent above, in or below a target zone which I could program into it; the time data could be retrieved at the end of a ride (just 3 numbers, nothing fancy). It didn't keep track of the maximum rate I drove the poor thing up to though, which turned out to be something I think now I should have had; it would at the time have required going one model up-market, for about another $30.

Initially I bought it because I was arriving home from rides in a pretty stressed state, physically. (I live on top of what was then a very significant hill which I used to charge up, about 50m high as near as I could tell from a map, although later when I had an altimeter I found out it was only 30m high; and prior to returning to the bike I had a fairly sedentary lifestyle, at least as far as aerobic activity was concerned). (the hill is still as significant, it just doesn't kill me to ride up it anymore: I have learned how to defeat it). With the HR monitor I found out that when I came up that thing I was exceeding the theoretical maximum HR for my age by about 15%! So I stopped attacking the hill so hard and probably the HR monitor saved my life; I guess that was worth the hundred bucks (some might argue that, but you'll have to feed me wine to get me into that conversation).

Well, maybe it was just me, and the rest of you are more sedate in your approach to the last hill of the day: but my brain was stuck at 18, while my body certainly wasn't. Nor could I now push the gears uphill that my old racing bike of the early '70's came with-- that was before the days of mountain biking and mountain bike gears. I should also admit that I got the HR monitor because it was a current tool of the racer training, and if they had been available in my teen years I would have wanted one; I just have to have all the gadgets I can manage -- this will be a recurring theme here... So with the HR monitor, initially a bit of any eye opener.
I still consider the HR monitor, whether a basic or a more complex model, to be the cyclist's most important tool, maybe even ahead of a pump, wrench, screwdriver, and odometer.

Two years ago I decided that I wanted to know about hill heights and wanted to look at HR data after a ride, so I got a HR unit with a heap of features (overkill, really, if one is allowed to use that expression in a discussion of heart rates!!): an onboard memory which could be downloaded to my PC after a ride. (also a power meter add-on of some sort). It's a gadget, so of course... Anyways... It did provide me with the graphic data that I use in these articles.

Youngsters will probably laugh themselves silly at the low power and HR numbers seen on the graphs, but hey, it's the best I can do just now.

With the more sophistocated HR monitor came some literature and website info that got into the whole "HR as a training tool" issue, and from that I did some more reading and researching. Now, most of what I came across is not particularily relevant to the average Recreational Cyclist, but some of it turns out to be very much relevant, in my opinion. That's what I'm going to discuss here.

First a bit of physiology, as I understand it, and condensed by me.

Aerobic vs Anaerobic effort: Aerobic effort is when the physical activity is taking place at a rate which allows sufficient oxygen to get to the muscles for them to "burn fuel" cleanly, that is without producing toxic waste products. Aerobic cycling is a Good thing. Anaerobic effort is when the blood stream cannot supply sufficient oxygen to the muscles for clean burning, and so a different chemical process results and toxic byproducts such as the dreaded lactic acid build up in the muscles. And this is a Bad thing. Logically, one would expect the body to scream foul when one drives it hard enough to go anaerobic, but it doesn't really scream loudly enough until one has either been mildly anaerobic for an extended period or is quite heavily anaerobic for a short period. In terms of Heart Rate, the changeover between aerobic and anaerobic occurs somewhere around 90% of a person's maximum HR. A person putting out an effort slightly above the Anaerobic Threshold can only maintain it for 30-45minutes, after which pain and fatigue force reduction to aerobic levels of effort. (Trained athletes can work at their maximum HR for only 2 minutes or less.)

(The literature sort-of treats the Aerobic/ Anaerobic threshold like a switch, ie either one or the other, but that doesn't quite compute to me and I personally think of it as both processes going on together during a changeover zone. In practice this might mean that some muscles are being overworked and under-oxygenated earlier than others, for whatever reason)

Once a body has worked anaerobically and then returns to aerobic rate of effort, the byproducts of the anaerobic period are cleaned up by the body; how long that takes depends on the concentration of byproducts in the blood and muscles, and the level of effort that the body has dropped to. That is: if you keep cycling along at a HR just under the point where you become anaerobic there is little slack in the body engine for cleanup, whereas if you are proceeding at a much more sedate "Recovery Rate", cleanup is more rapid. In a fairly fit individual, one minute of maximum effort (ie close to his/her maximum HR) requires at least 10 minutes at a Recovery rate for complete recovery.

Recovery HR is at or below about 55% of the HR at which anaerobic activity starts (called the Anaerobic Threshold, or Lactate Threshold). More usefully, it's at about 60% of maximum HR. In terms of power output, it is much less than half of the power output at the Anaerobic Threshold. So one really does need to go sedately when recovering from a big hill.

While I'm on that, physically the worst place to stop cycling is at the top of a hill. Easy pedalling for several minutes after an exertion helps blood circulation in the leg muscles, whereas stopping abruptly somewhat reduces the blood to the muscles and thus the recovery. Unfortunately, the best views tend to be from hilltops. So for the recreational rider, a tradeoff can be to ease off on the pedalling shortly before cresting a hill (racers would cringe at the thought of this, they tend to try the opposite if they can). Or better still go up the hill at an aerobic pace if possible; this means slower pedalling in a lower gear. It is interesting to note that a 5% slope can be climbed at a walking pace with only 40watts of power output in windless conditions, and that's still fast enough to control the bike and not fall over; the same climb at 10kph takes about 100watts. 40watts is probably in or below the Recovery HR range for most of us in the CCC and not much above it for the rest. Flat terrain at 20kph takes about 60watts on a windless day (at 25kph, about 120w; at 40kph about 400w). That's not just a string of numbers, but rather hints for riding strategies.

Another little aside:
Recovery: There are about 4 main stages of recovery, as I see it. First is what we might call HR recovery, which happens when you back off from an effort and after awhile your HR starts to drop until it reaches the rate appropriate for your activity level. If you are at a work rate higher than that at which you can go to the next stage of recovery, any little increase in effort will result in an immediate increase in HR-- you are basically riding a tight-rope there and your blood components are in a steady-state. That next level of recovery is sort of a System recovery (my term for it, you probably won't read this elsewhere in the same words)during which you are working at a rate at which your body can burn off the toxic effects of anaerobic activity; the lower your work rate, the faster the cleanup. Third is Resting recovery, essentially an overnight activity, during which repair to muscle fibre etc which has been strained during the ride is possible. Fourth is sort of Enforced Rest which is necessary if you really overstrain your cardio-vascular system, a state which used to be called burnout (which was treated by coaches yelling at you louder and giving you extra work as punishment for "bad attitude") but which is now known as Overtraining Syndrome (treated by, you guessed it, enforced rest)

Is there more to this anaerobic activity than just tiring the muscles faster and requiring a longer recovery? Well, yes: in the worst case your muscles will actually weaken from the exercise rather than strengthening. The by-products of anaerobic activity are toxic, and at high work rates the body engine can choose to use muscle protein for fuel in preference over more usual forms of fuel like carbohydrate derivatives and (at relatively low levels of effort) fat. So unless there is a trophy or a goodly prize purse at the end of the ride, why would you want to do this to your body, knowing what you do now?

The converse of this is that muscles are better strengthened when worked at aerobic rates so there is a double bonus to keeping the heart rate down. The trick to strengthening the leg muscles on the bike is to work them as hard as possible without becoming anaerobic. This is tricky to do without a HR monitor; I find that I either go too hard or else feel like I am working at just the right pace when in fact I am quite a bit more relaxed than necessary or optimal.

Within the aerobic range you will (hopefully) find a work rate which you can maintain for quite awhile without getting weaker: a slight increase over that, while still aerobic, will result in slowly losing power over time without the heart rate falling off.
Does it matter to the recreational cyclist if their legs get stronger over time, or if their strength gradually reduces during a long ride? Well, apart from the obvious get-there-faster or -earlier thing which may not matter on any given day, it turns out that the more sustainable power you can put into your legs the less weight there is on your bike saddle! Yes, it's true; your feet support part of your body weight when you pedal, and the more force on the pedals the less on the sit bones. That can matter a lot...

Riding at a sedate pace does have an interesting side-effect hinted several paragraphs ago: it turns out that the fuel of choice of the aerobic engine at the lower range of aerobic activity (65-80% of one's maximum HR) is fat, not carbohydrates. Some fat will still be burned at higher heart rates, but it is a secondary fuel then.

A couple of other miscellaneous points on this subject... research has found that at the start of exercising it takes about 10 or more minutes to kick-start the aerobic engine and get it burning efficiently. During that first short period the body operates essentially in anaerobic mode. Ah-ha! the mythical "second wind" is no myth at all, it is a real physiological event.

This probably goes a long way towards explaining why those first few kilometers after our extended lunch breaks always feel like death is imminent (well, it does to me!). For me, improvement in power output vs heart rate continues for about a half hour or so before my engine is really ticking over optimally. The graph shows me at the start of a ride session; notice how after an initial peak HR drops off while power continues to increase.

Second, by alternating short periods of anaerobic affort with longer periods of aerobic effort just below the anaerobic threshold, the body can be trained to become more efficient at flushing anaerobic byproducts. Important to racers, but this is type of training is hard on the body and for the recreational cyclist it is probably better to try to avoid that anaerobic bit, or if unavoidable take a nice long slow recovery period afterwards. Finally for what it's worth, like all body functions, a person's Anaerobic Threshold drifts a bit from day to day and even from hour to hour, depending on how rested the body is.

Also of note, the consensus seems to be that no amount or type of training can change an individual's maximum HR or HR at Anaerobic Threshold significantly (at least not in a positive direction!). That is, at least as concerns the adult body; I haven't come across anything on whether or not they can be affected in childhood. The objective of the cyclist seeking to improve, whether professional or casual, is to increase power output at any given HR, i.e. stronger legs for more fun. On which, for those who say that as recreational cyclists they do not train, I'm of the opinion that every time you ride a bike you are training for your next bike ride just by making the pedals go...

Is there a way to tell when you are crossing into anaerobic effort, from the "feel" of your body? Unfortunately, at least in my own case, not until things are fairly well along: that is, significant lactic acid buildup has already occured. Possible tell-tale signs:
- heavy breathing? Not really, my breathing seems equally laboured (or unlaboured) once I reach a rhythm, whether 20 beats per minute (bpm) below my Anaerobic Threshold or 10 bpm above it. However, when I am gasping for air uncontrollably then I know that I am near or at my maximum HR and need to ease off considerably to recover from the effort, but by then the damage to my endurance is done.
- "burning" feeling in the leg muscles? Definitely, yes: the burning sensation is caused at least in part by lactic acid buildup, but again one doesn't really feel it until there is more than a bit of it. It's possible too to get a minor burn for a short period after starting an increased effort even if the effort is not anaerobic once you settle into it.
- legs feeling "heavy" or engorged? Yes, could be an indication of a lower level of lactic build-up before getting to the burn stage. But could also be an indication that you need to take in some fuel or even water.
- if the slope of the road hasn't changed or the wind increased and you have felt like you have been riding at the same effort but your speed is decreasing "significantly", that could indicate increasing lactic acid levels, or might mean you need fuel or water. But this is Nova Scotia where the road never holds a consistant slope and the wind is always shifting direction and speed, so I think that's a non-starter as an indicator!
- a Heart Rate monitor does give a very good and reliable indicator of when you are working at an anaerobic rate. I'll explain how to make use of one a bit further on.

By accident I have bumped into a description of some readily discernable physiological effects generally experienced at some of the effort rates:
- a thing called the "gossip threshold": at a "minimal" activity rate, up to 80% of maximum HR, it's possible to carry on a chat without getting out of breath. But approaching this 80% probably can't sing Mozart opera; maybe a bit of Gilbert & Sullivan "patter" song, soto voce.
- at a "light" activity rate, 80-90%, conversation isn't possible but control of breathing technique is possible despite having to breathe deeply. At the upper end of this range, one is flirting with anaerobic effects. Fit folks should be able to maintain this activity rate for over 30 minutes.
- above 90% is the anaerobic zone; one cannot control one's breathing; rather, the need to breath controls the rider. (on a personal note, though, I find I can yell at charging dogs [or rude/ inattentive motorists] regardless of my HR zone-- but I guess that's an adrenalin thing!)

Some, if not most!, people are probably more in tune with their body responses than I am, and may be able to tell the onset of anaerobic effort more readily than I can. But I think they can only do that if they have a milestone to learn from. Which means riding with a HR monitor for awhile and paying attention to it.
Of course some of you have been riding long enough that you can perhaps set a pace which you can maintain all day without problem. I used to "know" that I could, until I ran into more information and started paying attention to it this fall. Yes, I could spend the whole day riding and still get up the hill to home (not just the final 30m rise but the whole 200m above Windsor), but with hindsight I know now that going through the Rawdon Hills early in the day put me into oxygen debt which I never really got out of, and every subsequent hill reversed some of the recovery that I had somehow managed.

Using the HR Monitor

So how might a recreational cyclist make use of a HR monitor?

First off, you really don't need to know exactly what your Anaerobic Threshold is; racers like to so they can maximize their power output for the race, whether that means going above it for a few periods or not; but recreational riders should probably avoid getting that close to the edge.

So, when you buy a basic HR monitor it should come with a booklet including charts of reasonable exercise zones for varying levels of fitness and age and sex. These will have been approved by the manufacturer's legal department, so tend to be on the conservative side. But for non-competitive activity conservative is great. (The booklet that came with my first, basic, HR monitor recommended 50-70% of HR max for Beginner users, and 70-80% for Advanced users (also 80-100% for Competitive users)).

Start off by calculating your theoretical maximum HR. A popular formula for this is a medical standard, so the industry uses it with impunity. It is nicely straightforward, 220 minus your age in years. There are some slightly different formulas out there though; the one that came with my first HR monitor (Sigma Sport) is 210 minus half of age with a small adjustment for weight (minus 0.11 x weight) and a slight fudge factor for men (it seems the ladies have better hearts but we mostly knew that already anyways, right guys?). For me, the latter formula gives a higher number over the simpler formula, by about 6 at this point in my life.

Next, there are a couple of numbers to determine, based on a percentage of your theoretical maximum HR.
- exercise Target Zone. This will be easily aerobic, and for average non-competitive folk will be about 65-80%, or the 50-70% mentioned earlier if you prefer. Well, cycling at a HR lower than the bottom of the range is still useful aerobics too. I think there is a bottom end to the target zone so that folks sweating in a gym will feel they are getting their money's worth out of it. So let's just say under 80%.

- approximate Anaerobic Threshold: use 85% of maximum initially (90% if you are fairly fit-- not to imply that your threshold will be higher if you are fit, just that you will be better able to deal with the stress of going to or over it); if this turns out to be too high or too low you can adjust it downward. This is a HR to avoid reaching whenever possible. But keep in mind that your HR response will lag your physical effort by 30 seconds to a minute so you really need to start easing up on your pedals and/or gear down some time before that number pops up on your HR monitor! Experience will teach you how much time depending on how hard you're working. From the perspective of endurance, better to slow down early and sneak up on the maximum rate you've set yourself rather than going past it by accident and having to drop back and recover from it.

- your Recovery zone, to follow up those occasions when you can't avoid going a bit anaerobic. Use 60% of maximum as the upper limit. Or even less if you want (not too much less or you'll need to have a hammock with you).

This graph shows how the effort required to maintain a work rate increases dramatically as HR increases. Remember the old "10 percent rule" in which 90 percent of the effort goes into the last 10 percent of quality of the final output? Well, there it is again. Of passing interest, at zero heartrate one just ain't making an effort...
For the curious including George, the numbers 1-5 on the curve itself refer to the lower limits of an example of HR Zones for use in training or riding: Zone 1: Maximum intensity, Zone 2: Hard intensity, Zone 3: Moderate intensity, Zone 4: Light intensity, Zone 5: Very light intensity. Different coaching/training philosophies use different Zone heirarchies but the effort v percent of HR curve remains the same.

The bottom line in all this is that a large exertion to get up a hill a few minutes faster could very likely end up costing you more time (and energy) over the duration of a long ride than what you gain on that hill. The first few minutes of over-exertion will produce an increased power and speed, but before too long your power output will be at best only slightly greater than if you had kept a more reasonable speed, but your heart will still be pounding away like heck and your exertion level will be still be high. Here are two charts showing this effect.
These compare my outputs on two rides over the same simulated terrain on the I-magic trainer (the pale green shading shows the terrain; looks pretty severe but the maximum elevation equivalent is not really all that high, only about 50m if I recall correctly). The first graph shows the entire route, the second one zooms in on a small segment. The rides were about 3 months apart so aren't really directly comparable but the trends are shown clearly enough. The solid lines are from the most recent ride, in which I tried to keep my HR around 135 at all times (for reference, at 130 I am able to recover slowly or maintain a steady power output for over an hour, at 137 I have poor recovery and lose power during an hour). The dotted lines are data of the first run, during which I tried for HR 130 on the flats and 155 on the "climbs". Note how power output (the green line) is about the same on all the flats in the solid run, but is lower and lower in the flats after each hill set in the dotted run. Note the extra effort of the dotted run results in a shorter overall time by only 1 minute over a total time just under 70 minutes. In fact, both riders start the first hill set at the same time, the dotted rider comes back on the flats a few hundred metres ahead of the solid one, but by the foot of the second set of hills has almost been completely caught except for about 20m (you can't see this on the graph, but you can see the differences in the blue lines, speed, between the two).

(For inquiring minds: Bike racers are subject to the same problem, except that being more fit and properly trained (in theory) they recover faster, and it is worth their while to turn themselves inside-out to keep up with the rest of the race because at their speeds (even up mountains) there is a great advantage to riding in someone else's slipstream. Plus they don't get to stop for lunch at interesting places.)

There's nothing wrong with recreational cyclists pushing their body into anaerobic efforts if you know that you're doing it, limit the duration, recover reasonably, and have some kind of a plan or objective. But I'd suggest that for most the best time to do it is not the first hill of the day but rather towards the end of a group ride or shortly before the lunch stop (the sprint for the table with a view). Remembering of course to take time and distance to cool down gradually before actually stopping.

Now, if you still don't think a HR monitor can help you ride more enjoyably and with less strain, I didn't do a very good job of explaining myself... (no news there, some might say). Finally, I will now come clean and tell you that I do not work for, or in any way benefit from sales of, any brand of HR monitor!

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Monday, March 03, 2008

To Pedal Fast or Pedal Slow?

Pedalling Cadence

This is a topic somewhat fraught with controversy, contradiction, and personal preference, not to mention habit and dare one say stubborness. On my part as much as anyone else's. Better minds than mine have studied this issue, and there are probably formal scientific studies still being written up, and started, even now. However it seems to me to be a multi-faceted problem (if it can be called a problem!) which earlier studies at least, seem to have simplified into only a few facets. Whether or not I have anything to add to the debate, I've tried to present some of the aspects of this subject here; it's somewhere between a summary and an analysis, and not the best organized thing I've written either, but hopefully you can pick out the more relevent points to your style.

Perhaps part of the two-sidedness of the debate stems from the differing objectives of different cyclists. Obviously, racers have different objectives to recreational cyclists, but rec riders too may have different objectives. For example, if you just ride for the freedom of the road and want to conserve as much energy as possible, you might want to adopt a slower cadence. If your objective is cardiovascular improvement or just general fitness, the slower cadence is less useful. Other objectives which should cause reflection might be: distances you will be covering; whether or not building stronger leg muscles is the prime consideration; or perhaps something else. Frequency of riding might be a factor: if one only rides a couple of times per week, micro-scale muscle damage caused by grinding low cadences has lots of time to repair itself between rides, whereas if one spends several hours every day on the bike muscle damage becomes cumulative when it cannot repair fully between rides.

One of the things that struck me when I started riding with the CCC was the wide range of riding styles. What I found most curious was the slow pedalling of high gears used by many of you, by preference. Having grown up with one of the single-gear coaster-brake bikes, the only way to go fast was to pedal like mad, a quality that stood me in good stead when I got into racing. Racers like to spin the pedals at a high cadence, partly because they have to at the speeds the race goes, and partly for the pedalling efficiency and better accelerations this gives them. Even racers who are reknowned for slow cadences and high gears are still working in the range of 85 rpm give or take a bit, on flats or hills.

Anyways, without making any judgements on the even slower cadence of the recreational cyclist, I tried first to find out more about the advantages or disadvantages of spinning vs stomping. Of course most of the literature on this subject is written for or by racers, but during one of the rides this past summer Gary mentioned an article in a cycling mag that had concluded that a cadence of about 60rpm provided a touring cyclist with the best efficiency that is, distance covered for nutrition requirements (ie needed to eat less). I suppose in some way that compares to the most economical ride, similar to the speed at which a motor vehicle gets the best gas mileage.
This article has the problem, for me, of not specifying the duration of the test rides. The various types of tests and analyses are interesting if you're into that sort of thing (which I am if you haven't already noticed!), but what I found more interesting and enlightening was the discussion of biomechanical issues (ie muscle and joint interactions) tucked away in the last half of the webpage, based on computer modelling which at the time may or may not have been as valid as what can be done today. Worth looking at.

It's also worth keeping in mind that on group rides the speed of the group you're in may be such that one has a choice between riding in a gear which gives a slower cadence than preferred, or the next gear down which will give a cadence higher than preferred; the temptation is of course to opt for strolling along in the higher gear/ lower cadence because settling into a cadence a bit higher than optimum is initially a bit uncomfortable.

60rpm seemed awfully low to me. (I tend to fall into a natural cadence of about 90-95 if I can find the right gear for it, but sometimes as low as the mid-80's or up around 100 feels right at the time.) But I didn't want to espouse an argument without having derived some kind of basis for it.

How to do that? (Keep in mind that I didn't do any literature research until later, and didn't have Gary's link at that point either.)

Well, I thought that with the beginning of winter and my shift from outdoor riding to my indoor trainer I might be able to prove something by comparing equal rides using the instrumentation of my trainer. I thought I would be able to see some effect on my Heart Rate caused by changing the cadence.

Note: feel free to skip the graphs if you're inclined to; they're there for anyone interested in seeing what I'm talking about but aren't necessary to
understanding it (or at least I don't think so!)

Test "protocol": first attempt. My first attempt was to try several cadences for short segments all in one ride (following a warmup period, of course). The objective was to hold a steady speed of 25kph no matter what, the cadence determined by the gear selected. Each segment consisted of 4 sections: first about 1 minute at a slope of -1 during which I switched to the new gear and settled into the new cadence. Then about 2 minutes at a slope of +1, about a minute at a slope of +3 (to apply a bit of stress), and then back to slope +1 for another 2 minutes. I chose 25kph speed and the slope value of +1 rather than zero to make sure that I would be working hard enough to create a difference. The gearing on my bike gave me the following cadences, tested in the order listed: 54rpm, (101rpm*), 57 rpm, 92rpm, 62rpm, 84rpm, 66rpm, 76rpm, 53rpm, and 92rpm. To cover for the case of being insufficiently warmed up I repeated the lowest and second highest segments at the end. I didn't repeat the highest segment* because I couldn't maintain the 25kph test speed in the lowest test gear.

[Graph of heart rate, power, cadance and slope during the first run; speed 25kph throughout most. In following runs the cadence and speed were held constant and the slope program was the same as here.]

There were no obvious trends in the data. When I graphed analysis,
the general shape of the resulting curves could be interpretted as showing that something optimal happens between cadences of 70-90rpm. Alternatively one could say that it looked like the lower the cadence the better things looked. Can that be right? Nah- more testing required.

Test "protocol": second attempt. It seemed obvious that I was going to have to ride at each cadence for an extended period. I decided to use the same "ride profile" as for the initial test, for each of the repeat tests. That is, for each cadence I would ride a warmup and then 10 segments of -1, +1, +3, +1 slopes. I ended up doing the tests in pairs, on day 1 I would do a lower cadence test, day 2 a higher cadence test, then a few days of rest or other riding to keep my interest alive-- this grinding out 25kph at a constant cadence for over an hour was awfully boring despite the slope changes, especially at lower cadences!

Here's an example of raw data, for runs at 52 and 84rpm:

And here, zoomed into the last two slope cycles.

What I was hoping to see was a difference in the change of HR going into and out of the +3 slope segment, or in the smoothness of the power output at the slope changes. Nothing significant that I could see. Darn!

Results were mixed. That is, what the numbers were showing me was not, for the most part, what my body was feeling like. It was a great strain to do the runs at the lower cadences whereas the higher cadence runs were much easier, but yet my average HR was lower at the lower cadences, which should indicate a lower effort. The minimum HR's were at a cadence of 62 rpm, which correlated with what Gary had read.

At first brush, the "Energy expended" (Kcal) per run was steady across all runs. That makes sense, because the Energy data (blue line in the next graph) I was looking at was recorded by my I-magic trainer Catalyst software, which measures the actual work done by the back wheel to rotate a spindle and small flywheel against an electromagnetic brake. So this pick-up sees only the speed of the spindle and the resistance of the brake (set by the Slope function, here). However, most HR monitors for athletes on the move (as opposed to on stationary equipment) incorporate a calculation of "Energy expended" (E) which is calculated from the HR data, as a reasonable approximation. I also had these numbers available ("Polar" curve, pink in the graph below), and when I looked at them of course the 62rpm run gave the lowest E, while the more comfortable higher cadences gave the highest E. However I was also feeling physically somewhat better on the day of the 62rpm run so maybe that minimum is a bit more minimum than it should normally be; still, the trend is there in the 57 and 67 rpm runs.

So that should be the end of discussion, right?

Uh, no.

First there is the immensely subjective, qualitative issue of how the various cadences felt to my legs and body (always bearing in mind that I am used to the higher cadences by choice). Notes made at the time of each run:

  • 52rpm: Thighs tight and tightening; Knees and lower back bothered by it, also neck and shoulders from deathgrip on handlebars for much of the ex. A bit of a struggle after 7th group (of 10). No muscle fatigue or stiffness the next day though.
  • 57rpm: (no notes made but essentially felt the same as at 52)
  • 62rpm: HR's low the last 2 days, I am better rested somehow. Kind of messes up the project?
  • 67rpm: A minor struggle to keep the pedals turning.
  • 75rpm: Thighs, Knees and Lwr back good. Got a bit harder on the quads after about the hour mark, otherwise a comfortable slow cadence.
  • 83rpm: (no notes; this cadence is well within my comfort zone so all felt normal and easy)
  • 92rpm: a good roll but tired from prev day and today activities (off the bike). So HR higher than I think it should be. Quads painless.

Some of those notes might lead one to believe that a few runs should be redone. Well, the protocol is only loosely repeatable (certainly not to scientific standards!) because I didn't follow a consistent activity plan or diet for the duration of the test period (17Nov to 3Dec). Nor did I drink at the same times in each run (I always have a bump in HR for about 30 sec after drinking on the bike!). However, the significance of the Energy output minimum at about 62rpm deserves a better look, in view of the noted aberation.

From the feeling of my thighs during the lower cadence runs, I think that if I had continued for an even longer effort, maybe 2 hours, they would have been sufficiently fatigued to cause a change in HR, whereas at 83rpm I know that the numbers would have been about the same after 2 hours. Maybe next winter...

One of the numbers the Polar instrumentation on my bike (separate from the Imagic gadget the bike sits on) gives me is a thing called Pedalling Index (PI). Basically, the feet do not apply equal force to the pedals during the entire 360degrees of the revolution; PI gives an indication of how distributed the force is. A higher PI means the force is applied more evenly and occurs during a larger arc of the pedal stroke; a smaller PI correlates to a jerky pedal motion with large force of shorter duration. When I went back and looked at PI data for the various runs, I found the following:
[In the graph, the averages are the more useful numbers than the maximums. "slope3 avg" is the average PI of a single representative 1-minute interval at Slope of +3 (I used the same time interval from each run)].

What I find interesting in the graph is how the overall average (entire 70-minute run) is about as good at 75rpm as 83 and 92, but the slope3 avg for 75rpm is as bad as for the slower cadences. This seems to tell me that to optimally handle the little dips in the road and gusts of wind, a cadence of 83 or slightly lower is best (for me at least; the question remains just how "average" am I in this regard?). There is also a pretty large difference in the average run PI between the lower cadences and the higher ones.

Let's examine this a bit more closely. Although it seems like the bike maintains a steady speed while being pedalled at a cruising rate, in fact it is constantly accelerating at each pedal stroke and decelerating between them. During each test I was going the same speed and the power outputs were always the same for each slope setting regardless of cadence. That means that where the PI was low I was exerting a relatively greater force on the pedals for a small arc and then not much force for the rest of it, whereas at a higher PI the peak force in each revolution was smaller but it was spread over a larger arc. In effect, when the PI is low the larger force is required to accelerate the bike back up to speed, but the legs cannot maintain that level of force for very long and so ease off from that maximum very quickly, although they never relax to the same degree as they do at higher cadences. So the bike is continually speeding up and then slowing down as it goes along the road. At higher PI less effort is needed to accelerate back up to speed, partly because of the lower gearing and partly because the bike has not had as long to slow down (faster pedal rpm's and less of each revolution without much power).

On the trainer, I am working with the momentum of my back wheel plus a small flywheel whereas on the road there would be the entire momentum of bike plus rider. The trainer actually slows down faster than I would from the same speed on the road, but it speeds up much more quickly. So on the road the alternating slowing and accelerating of the bike would have the result that the force required at lower cadences would be larger, the rider's legs would tire sooner.

If you are ever riding on the road with someone who has knobby tires on their bike, you will be able to hear this (the speeding and slowing, not the tiring of the legs! but maybe that too) in the sound the tires make, the sound increasing in pitch with the accelerating part of the pedal stroke and decreasing in pitch when decelerating. If you can get the rider to try different gears while staying at the same speed you will hear the different amounts of deceleration.

In practice this means that if I were to re-do all these tests on the road, I would expect to see higher energy output per test on the road compared to on the trainer, but significantly higher at the lower cadences while only marginally higher at the higher ones. I think that this would shift the cadence at which the minimum effort occured to something higher than the 62rpm.

Physiological effects at lower cadences: we've seen, unexpectedly, that the HR during low cadence runs was less than at higher cadences even though the power measured at the trainer roller was the same in both cases. At the same time, my qualitative notes are telling me that my legs were more tired and less likely to last for hours at the lower cadences. So what's going on here? In a (hopefully) educated guess, I think we're looking at reduced blood circulation due to the leg muscles being tighter from the stronger forces they are producing, essentially like a weight-lifter's muscles get "pumped up". Less blood flow, less oxygen, therefore more premature lactic acid production in the muscles. But the reduced blood flow masks the extent of lactic build-up because less waste products are getting into the blood stream (to signal that more oxygen is required). So the body goes merrily on its way with an aerobic-zone HR, even though anaerobic activity is going in in the muscles. The cardiovascular system lacks correct feedback and produces a false effort (HR). Possibly there is a blood pressure issue involved as well. In contrast, at higher pedal rpm the lesser contractions but greater relaxations of the leg muscles probably enhance the blood flow through the muscles, not only perhaps assisting the heart in actual pumping but also keeping the blood vessels more open. So the cardiovascular system may be able to respond with great efficiency at detecting muscle combustion by-products. At ridiculously high cadences and low gearing there is so much blood rushing around that the HR gets much higher than the power output warrants.

Since doing those tests on the bike, I've noticed that (on the trainer) whenever I shift gears there is an almost instant small but transient shift in my HR (only a few beats per minute, but there nonetheless, for a short while. When shifting to a higher gear (slower cadence) my HR drops, and when shifting to a lower gear (higher cadence) my HR increases. The increases generally last longer than the decrease but I haven't timed them. The fact that the effect is almost instantly seen indicates to me that it probably has more to do with a circulation issue (blood pressure or some such) than to heart rate increase due to a change in work rate.

I noticed some hints about the above effects in some training exercises prescribed for competitive cyclists. (Chris Carmichael: "The Ultimate Ride"). For basic aerobic system development workouts, he directs the rider to use a cadence of 85-95. Interspersed therein come sub-exercises of various sorts (don't use the following as basis for training; there are detailed instructions on use of them for best results which should be read first):

  • Fast Pedal: short intervals at 105 to 130+ rpm, with equal recovery periods between them. "heart rate will climb during intervals, but should not be used as an indicator of intensity"
  • "MuscleTension"(TM) Intervals: hard pushing at low cadence, 50 to 55rpm. Maximum duration of 12 minutes (max 4 repeats with recovery between) and at least 48 hours between sessions. "This is a muscular workout, so heartrate is not a good indicator of intensity and should remain low".

There are also a number of other workout types of which 2 seem to offer some insight here:

  • Recovery rides: Cadence 75-85 (with low gearing and low HR).
  • "Tempo"(TM) riding: this is a bit of a complicated and hard workout, targeting a HR close to anaerobic. But the salient points as far as this discussion are concerned are: uses a cadence of 70-75rpm; trains the body for "better fuel utilization during long races or rides"; strengthens leg muscles; duration up to 2 hours, and at least 36 hours between sessions.

There are essentially two movement types of getting power to the pedals: using a circular foot motion, or linearly using the legs as pile-drivers with essentially up-down motion. How can that work, you ask, since the pedals go in a circle. In the circular case, power is applied tangentially to the crankshaft, first by straightening the knee deliberately when the crank is vertical upwards, then progressively adjusting the angle of attack as the crank progresses around, pulling back through the bottom of the stroke and finally lifting its own weight on the up-stroke; this gives a high Pedalling Index. (Easier said than done, requiring concentrated practice.) At higher cadences the momentum of the foot performing a circularly-driven pedal stroke adds to the muscular effort to enhance the efficiency. In the pile-driver case, the rider is just concerned with a big downstroke and some energy is dissipated in fighting the fore-and-aft vector of pedal motion; low Pedalling Index. The momentum of the circular foot motion is lost. This motion can also be hard on the hamstrings which function in decelerating the leg, because this pedalling motion requires hard decelerations rather than the softer ones of the circular motion. I find that a more circular pedalling motion (but certainly not a perfect one by a long shot) comes naturally to me at higher cadences, and that at lower cadences I really have to think about what I'm doing to avoid being a pile-driver. Circular pedalling also stabilizes the pelvis to some degree (or vice versa?), whereas linear pedalling often results in the body rocking along from the hips and even the shoulders (fighting with the bike). The cyclist is most efficient when the upper body can relax, and any tension and motion of the upper body takes energy away from the power available for pedalling. Ironically, body-rocking is more likely when the rider is fatigued, a time at which efficiency is most desired but hardest to achieve. Having said all that, if one watches the Tour de France on tv one can see some pros doing quite nicely with what looks like very inefficient style. So in the end, it boils down to "whatever works best for you".

I did run across one medical perspective in my reading (Bernard Hineault: "Road Racing Training and Tactics): "When spinning is not smooth and regular, the cyclist puts excessive demands on the lumbo-sacral muscles which in turn subject the lumbar-sacral joint to extreme and abnormal stress." This can result in back pain.

As always, there is certainly a time and a place for grinding along at a slow cadence to build leg strength, but I think it is better done towards the end of a group ride rather than earlier, or when solo.

Time for an anecdote, maybe. At about the time that I got back on my bike after 13 years off it, I had a high-school kid working for me in the nursery who rode some BMX. Some of the work involved going a few km down the road to check on plants at a "remote" location (that commute is what got me back on the bike, rather than waste gas going such a short run in my van). Several times I took him along on a mountain bike, and over the next couple of years we did a few road and off-road rides. Anyways, to get to the point, he was initially very much a "power" rider, high gear/ low cadence and very set in his ways, but after watching me a bit and being surprised by the out-of-shape old guy beating him up the hills while he gasped and wheezed, I noticed that eventually he started using gears and cadences much like mine with better results, and did not go back to his previous style, at least while riding with me.

So what's the bottom line for the touring cyclist in all this cadence stuff? First, everyone has their own comfort zone in cadence. But your comfort zone may be one that you've fallen into by default, without trying anything else, and there may be a more comfortable and more efficient or useful cadence zone for you if you look around for it. Second, any attempts to change any aspect of your riding style should only be done gradually. So if you want to try to increase your cadence work into it a bit at a time. Third, definitely try a higher cadence, with lower gearing, when climbing hills or fighting a headwind. Apart from rationing leg-power, I personally find a psychological benefit from pedalling lightly with rapid leg motion into adverse conditions (ie strong winds or up hills); the speed of the legs makes it seem like there is more progress even if the ground is just creeping past. When leg muscles start to burn even a little bit or have become heavy, slow down and gear down and open up your cadence and let your heart rate back into the gossip zone so that the rest of the ride remains pleasant. And I think it is helpful to change cadence from time to time during a ride anyways, just to keep your legs interested, in much the same way as you change the position of your hands on the bars from time to time to keep your upper body more comfortable.

I find it is useful to change to a faster cadence for a few minutes every now and again, say about every 10-15 minutes. I may "lose ground" during the little spin, because I do slow down a bit, but maybe in the long run I might make it up again. And a high cadence the last few minutes before the end of the ride also helps start your legs into recovery by getting the blood moving.

When cresting a hill and starting down, instead of immediately changing clunk-clunk-clunk into a high gear and grinding down, spin out each gear before changing to the next lower (that is stay in a gear and just keep pedaling faster until you reach a fairly high cadence, say about 100rpm or when you start bouncing on the saddle, whichever comes first). You should find the down-shifting much easier on the legs because they won't be jarred by such a sudden increase in resistance. And actually you can accelerate faster that way too, if that matters.

But of course it's all about having fun, at the end of the day.

And here's a related curiosity. Suppose you are pedalling first up a hill in a small gear at 80rpm cadence at a work rate of 150watts, and later you are going down a hill in a big gear also at 80rpm and 150watts, obviously at a higher speed, will the pedalling feel the same to your legs? Logically, same rpm same work output, should feel the same but in fact No!! For me, the high gear segment will feel harder on the legs, and different, than the low gear segment. And apparently it's not just me. Don't know why, haven't seen an explanation for it, but it just is. If anyone out there feels the opposite, I'd be curious to know of it.

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