BikeArkansas

This morning I was riding a group event in the flat area East of the city. The winds were fairly stong with much of the ride in a crosswind situation. Anyway, the group was over 20 riders so we were in a double pace line. I had taken my time pulling, went to the back and had rotated to within about 4 slots from pulling again. We were 15 miles into the ride and holding a speed of 22 to 22 1/2 MPH when a couple of guys took the lead and jumped the speed to 24 1/2 MPH.

I immediately went from riding comfortably to suffering. Just 2 MPH made that much difference. After about a mile or so I was not dropped. I was flung off the back. I just could not hold the pace. Fortunately about 6 others had the safe fate at that speed difference, so we started our own paceline.

Actually, I was feeling very good on today's ride, so I found it amazing that my body found THAT much difference. However, I guess the old saying about "the straw that broke the camel's back" is true. There is that one point where everything changes. I know the gage is not the speed, because if you are pedaling directly into a strong headwind the amount of effort to hold 15 MPH could be more that the effort to hold a much higher speed with no wind. What was so interesting this morning was how close the difference between comfortable and suffering.

Mobile 155

Found this formula to express just what you said.

175 W for a 90 kg bike + rider to go 9 m/s (20 mph or 32 km/h) on the flats (76% of effort to overcome aerodynamic drag), or 2.6 m/s (5.8 mph or 9.4 km/h) on a 7% grade (21% of effort to overcome aerodynamic drag).

• 300 W for a 90 kg bike + rider at 11 m/s (25 mph or 40 km/h) on the flats (83% of effort to overcome aerodynamic drag) or 4.3 m/s (9.5 mph or 15 km/h) on a 7% grade (42% of effort to overcome aerodynamic drag).

• 165 W for a 65 kg bike + rider to go 9 m/s (20 mph or 32 km/h) on the flats (82% of effort to overcome aerodynamic drag), or 3.3 m/s (7.4 mph or 12 km/h) on a 7% grade (37% of effort to overcome aerodynamic drag).

• 285 W for a 65 kg bike + rider at 11 m/s (25 mph or 40 km/h) on the flats (87% of effort to overcome aerodynamic drag) or 5.3 m/s (12 mph or 19 km/h) on a 7% grade (61% of effort to overcome aerodynamic drag).

berner

https://bikecalculator.com/veloUS.html
There are a number of calculators on the web that, given initial parameters of some variables such as weight, slope, aero bars and others, will predict speed or power required, calories burned and other variables. My favorite calculator is out to lunch today but the one linked to above works fine.

If you play around with it you will find that power required for a given speed varies as the square of the speed, I believe. This means that to go twice as fast requires four times the power. This being so, a seemingly small increase in speed,say from 22 MPH to 24 MPH requires a surprisingly large increase in power output. The big lesson here is that as speed increases to near the top of our individual range, we need to be extra stingy about using up our available power and endurance.

This is all very interesting and an exercise in discipline. I find I get sucked into going too fast repeatedly. I hope you are a better learner than I am.

merlin55

Nope, power increases as a cube of the speed. Double the speed and the power goes up by 8 times. To go from 20 to 22 mph is a 10% increase in speed, but a 33% increase in power (1.1 x 1.1 x 1.1 = 1.331)

Dudelsack 

I'm going just the opposite. I have so many last places on Strava that I'm asking them to give me a special Lantern Rouge award.

OldsCOOL

That is why I dont care about headwinds in a training ride. Century's yes, training rides on hills, intervals and personal TT's....let it blow, baby.

CraigB

2 mph is a pretty darned big increase for anyone who's already at or near the top of their comfort range, regardless of what that comfortable speed is. 13 to 15 is big, 18 to 20 is big, 26 to 28 is big.

Hermes

Typically, drafting reduces the power required to hold pace by approximately 30% and that assumes tight formation. Cross winds change the equation such that the benefit of drafting is reduced. Also, as the speed increases, riders tend to allow more margin (space) between riders and begin to lose formation. Once that happens in a crosswind, even slightly gapped riders see the benefit of drafting reduced even more such that they may require as much power as the leaders to hang on.

The way to compensate for crosswind is by forming an echelon and angle behind the rider in front to stay shielded from the wind. In practice, it is hard to echelon across a road that is open to car traffic. However, staying in tight formation and riding low in the drops helps.

Phil85207

That would be a big jump for me. The last Tour de Mesa was very windy and pace lines were code of the west. There was a big very bad crash with several pros going to the hospital when a cross wind gust got wheels crossing. I would never get in a double pace line in high cross winds for sure.

OldsCOOL

Would the 2mph difference have more impact as total miles-per-ride increases? Sure does for me. (sorry if I dragged this offtopic)

TomD77

[QUOTE=berner;14155961

If you play around with it you will find that power required for a given speed varies as the square of the speed, I believe. [/QUOTE]

Correctly stated, the wind FORCE goes up by the square of the speed. But power is different than force, power is force X the distance that it is exerted over. Very simply stated, if you use a force of 5 pounds to push an object over a distance of 10 feet you have done twice the work than if you pushed it 5 feet. The result is that power requirements go up by the cube of the speed.

Hermes

It sure will if you are fatiguing more than the rest of the riders. Once you are riding at threshold power, any increases above threshold require you to burn a match (expression of power spikes above threshold). How many and how long they will burn is a function of your interval training. If you do 10 x 5 minute VO2 Max intervals, you have a lot of matches that can be used. If you do 3 x 3 minute VO2 max intervals, it is less.

As fatigue sets in the ability to produce threshold power decreases and matches shorten in duration and strength. So it is easy to see why riders get dropped so easily. It just takes 30 seconds at 20% more power than an rider can produce to pop him off the back.

The other aspect is skill. Reading the pack and focus on staying in tight formation helps a lot. Any gaps will dramatically increase power requirements on any accelerations or increases in speed by the group.

BikeArkansas

Reading the comments is quite interesting. I do not understand some of it, but it appears I was probably close to my comfort limit when the speed increase occurred. Add to the speed increase is the fact that the speed did spread the formation somewhat which caused a loss of protection from the wind and a loss of the draft effect. As I said earlier, there were 6 more riders off the back with me, so the formation did break apart. I know the physical science of this situation explains it, but I still find it amazing how 'absolute' the cut-off was for me in that 2 MPH differce. I felt like I could ride the entire 40 mile route we were on at 22+ MPH, but buy moving up just 2 MPH I was completely winded in a little over a mile. Although I have tried any number of sports, I find cycling baffling at times, but an amazing sport.

asgelle

A little too simply. Power and work are not the same thing.

berner

Merlin, correction accepted, required power for a speed increase goes up as the cube of the speed. It sure felt like a cube requirement today on the club ride as we all attempted to bore a hole into the wind. I'm a slow learner and always go too fast in the beginning. But it sure felt good to speed along at a good pace - for a while - until I began to cramp up. It's great to be human. I would not trade the experience for anything. Today's ride was awesome under a cristal clear blue sky and crisp air.

chasm54

Don't be amazed. Think about some of the comments above and it all makes perfect sense.

First, power goes up as the cube of the speed. So a 10% increase in speed requires a 30% increase in power. That's enough to get you off the back, if you're anywhere near your limit. Then add the fact that being in the bunch was saving you around 20%. So once off the back, your speed is going to drop. To get back on at the higher speed is going to need something like 50% more power than you felt comfortable maintaining. You're toast. If a gap develops, close it immediately or you are frigged.

Mort Canard

From a bit more of a physiological point of view, what happened to you was that your lungs couldn't keep up and your muscles kicked over from aerobic to anaerobic activity. Aerobic exercise burns both fat and sugars together in an efficient and fairly clean process. When your muscles need more oxygen than your lungs can provide the muscles start kicking into anaerobic mode. The muscles switch to burning mostly sugars and generate lactate which causes your muscles to burn and can cause some nausea. The longer you stay in anaerobic mode the more lactate the muscles generate and the greater the discomfort. Fortunately, in a fit person, the body can clear excessive lactate fairly rapidly when the activity level falls back to the place where the respiratory system can provide enough oxygen to keep up.

asgelle

There is absolutely no reason to believe this is true and good reason to believe it isn't. Taking the premise that the muscles weren't able to generate the required power primarily through aerobic metabolism, it doesn't follow that incomplete oxygenation of the blood was the reason. Other reasonable and more likely explanations would include insufficient stroke volume, inadequate difference between arterial and venous VO2, lack of intramuscular metabolic capacity, among others.

gregf83 

ftfy.

TomD77

Yeah, you have to introduce time as in force x distance with respect to time.

Dudelsack 

In summary, it's hard to go faster.

BigAura

AND --> There is ALWAYS someone else who IS faster.

Mort Canard

Yes my explanation was a little crude and I did lay a lot of the responsibility on the lungs for incomplete oxygenation when what I should have pointed to was general respiratory, circulatory and muscular efficiency. The problem, it seems to me was very likely was a shift to anaerobic metabolism.

Well let's see "insufficient stroke volume" suggests that the blood is fully oxygenated but that the heart can't pump it fast enough to supply the muscles. You are suggesting that the lungs are fully functional but the heart can't pump enough volume. Fair enough but the muscles are still not getting enough oxygen.

"Inadequate difference between arterial and venous VO2" is a result of the muscles not or not yet having removed enough oxygen from the blood supply. It results from not having enough slow twitch muscles with the needed capillaries to extract and process the oxygen.

"Lack of intramuscular metabolic capacity" would point to the slow twitch muscles having enough oxygen, fats and carbohydrates but not being able to process them. I assume you would suggest that this would be from not having enough of the slow twitch muscle fibers or that the ones our particular athlete has can't process all of the components fast enough. I have a little trouble with this one as the difference between 22.5 and 24.5 would not seem to matter that much to muscles having an adequate supply of fuel and oxygen. The fact that the OPs comfort returned fairly rapidly when he backed off marginally suggests to me that it would be a case of a problem with VO2max or Maximal Oxygen Capacity.

In short it seems to me that the OPs muscles were operating in oxygen deficit mode weather from inefficient lungs, heart or lack of capillary beds to supply the muscles. This whole collection of organs is designed to provide both fuel and oxygen to the muscles and it seems that the oxygen was in short supply.

Let me add that while I point to "inefficient lungs, heart or lack of capillary beds to supply the muscles", anyone who can keep up 22mph for a sustained period can't be that out of shape and I mean to cast no aspersions on Mr. BikeArkansas's fitness, merely the differential between him and the riders he was chasing.

I am open to hearing other explanations.