energy required to clmb a hil....
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Was out riding with a lady yesterday in the snow. Her first time mtbing. We did a 10km ride took 2 hours :oops: . (I'm, about 5-8kg heavier than her.) she is in the 60th percentile of weight to age according to the bmi calc and I'm in the 30th. Our fitness levels are chalk and cheese.
we used different computers, but broadly the same capabilities
Her avg hr was 148bpm for the ride against pre-ride of 68bpm, she peaked at 165bpm
mine was 65bpm against pre-ride of 44bpm, I peaked at 100bpm
there has to be something different going on in our bodies more that a few % here and there.0 -
Well, lets see. You're fitter than her. Anything else you might infer from that data you could just as easily get from tea leaves or a horoscope.
Lets use the Ferrari/Yaris analogy again. When doing 105mph, presumably in a Yaris the driver's accelerator would be on the floor and the engine doing 4000-5000 revs. The Ferrari would probably be doing 2000 with the accelerator barely depressed. Using your logic, we'd draw a conclusion we know is wrong.
Obv, this might not be a good analogy for humans riding bikes, but its an illustration of where attempts at logic without evidence go wrong.0 -
May be she was riding the machine from Burn After Reading0
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I'm not taking sides in this debate (as far as I can find out it seems to be genuinely controversial even amongst the experts), but I think it's important to make a clear distinction between efficiency of energy use and the ability to use more energy. The latter is what we normally think of as fitness - a fit person can put out more power, i.e. put out more energy per second, whereas efficiency is the percentage of total energy used that goes into propelling the bike, which is always going to be a small fraction of total energy consumed, mainly due to metabolic inefficiency. As I understand it, using more o2 and glucose with each heart stroke, increased mitochondrial density etc represents the ability to use energy at a greater rate (more glucose is oxidised / more ATP consumed), and doesn't necessarily say anything about what percentage of this energy is converted to physical work (as opposed to being released as heat).Wily-Quixote wrote:
You could read my comments earlier, most efficiency gains are produced by using more of the available o2and glucose that the heart can deliver with each stroke. There's many other factors, such as increased blood volume, myoglobin content in muscles, mitochondrial density, increased blood delivery, clearance of waste products etc.not all of which are efficiency gains per se, more quantitative gains in energy utilisation. But as this means less recycling of energy substrates per heart beat, these technically are additive to overall efficiency.Froomes Edgar wrote:Do we have any evidence for and/or quantification of this possible higher efficiency of the fitter rider? Thought not.
Except that it isn't obvious - training allows you to use energy (convert it from one form to another) more rapidly, not necessarily to do so more efficiently (convert more of it to mechanical energy rather than heat). This doesn't come into conflict with the principle of conservation of energy,It's pretty obvious that a trained cyclist is more efficient, biomechanically or metabolically -how else do you explain the value of training in light of the principle of conservation of energy?
For the record, I think it's pretty inevitable that a trained cyclist is going to be at least slightly more mechanically efficient (more of the mechanical energy produced by the muscles is going to be converted into motion), but the difference is probably not huge. Metabolic efficiency (amount of chemical energy consumed that is released as muscular mechanical energy) may or may not be something that responds to training, as I say, it seems to be controversial.0 -
Here's another slant. Two cyclists are on turbo trainers each linked to a generator which feeds electricity back into the mains. They don't even have to be the same weight or height.
Assuming they both wanted to generate 100w output for an hour every day for a year.......would their energy intake cost.....ie cost of food.....be exactly the same or could one be "more efficient" and need less food bought to generate the 100wh (x365s)?
I realise of course that whether that efficiency is natural or can be improved by training is another question.0 -
Te efficiency gains lie in the ability to access the glucose and O2 available in a given quantity of blood passing the cell. As you say, there a gains in the quantity of mitochondria etc ( bigger engine). But there are gains in efficiency because with a fitter athlete for every 100 ml of blood being ejected in a heartbeat 10% more of the glucose and oxygen may be being up taken ( this figure is plucked not accurate) over that of a non trained person. This next sentence is the key: In one heart beat this is not a gain in efficiency it is merely adding more fuel (like a turbo). Where the efficiency gain is made is in the next heartbeat, where the blood can gain 10% more oxygen and 10% more glucose and pass it around continuing the cycle. This is where the car analogy fails, because in a car unused fuel and unused oxygen in an engine cycle is not transported back around the system.neeb wrote:
I'm not taking sides in this debate (as far as I can find out it seems to be genuinely controversial even amongst the experts), but I think it's important to make a clear distinction between efficiency of energy use and the ability to use more energy. The latter is what we normally think of as fitness - a fit person can put out more power, i.e. put out more energy per second, whereas efficiency is the percentage of total energy used that goes into propelling the bike, which is always going to be a small fraction of total energy consumed, mainly due to metabolic inefficiency. As I understand it, using more o2 and glucose with each heart stroke, increased mitochondrial density etc represents the ability to use energy at a greater rate (more glucose is oxidised / more ATP consumed), and doesn't necessarily say anything about what percentage of this energy is converted to physical work (as opposed to being released as heat).Wily-Quixote wrote:
You could read my comments earlier, most efficiency gains are produced by using more of the available o2and glucose that the heart can deliver with each stroke. There's many other factors, such as increased blood volume, myoglobin content in muscles, mitochondrial density, increased blood delivery, clearance of waste products etc.not all of which are efficiency gains per se, more quantitative gains in energy utilisation. But as this means less recycling of energy substrates per heart beat, these technically are additive to overall efficiency.Froomes Edgar wrote:Do we have any evidence for and/or quantification of this possible higher efficiency of the fitter rider? Thought not.
Except that it isn't obvious - training allows you to use energy (convert it from one form to another) more rapidly, not necessarily to do so more efficiently (convert more of it to mechanical energy rather than heat). This doesn't come into conflict with the principle of conservation of energy,It's pretty obvious that a trained cyclist is more efficient, biomechanically or metabolically -how else do you explain the value of training in light of the principle of conservation of energy?
For the record, I think it's pretty inevitable that a trained cyclist is going to be at least slightly more mechanically efficient (more of the mechanical energy produced by the muscles is going to be converted into motion), but the difference is probably not huge. Metabolic efficiency (amount of chemical energy consumed that is released as muscular mechanical energy) may or may not be something that responds to training, as I say, it seems to be controversial.
Effectively, every heartstroke in an athlete allows greater utilisation which is then NOT inefficiently transported around the system in the next stroke.... The efficiency is per heartbeat. Other efficiency gains are created by increased heat clearance (a better radiator) and better waste clearance ( a better exhaust system). Same as pimping your ride, when you tRain you pimp your body.
Ever wondered why your heart rate is 20 beats lower than the fat guy sitting next to you at work? Your cardiovascular system is operating more efficiently.
In saying this,my understanding is that these efficiency gains are not huge and are proportionally less than the 'bigger engine' concept, in terms of performance.0 -
That's exactly the metabolic efficiency thing I was talking about above. The energy for the power output all comes ultimately from food, you can quantify exactly how much food (how many calories) goes into producing that 100w for an hour. But the amount of food energy needed to do this will always be about 4 times more than that due to metabolic inefficiency. One kilocalorie (Calorie with a big C) is exactly 4.184 kilojoules of energy, but to produce one Calorie's worth of mechanical energy you need to burn about 4 Calorie's worth (or more) of food energy. The rest is released as heat.YIMan wrote:Here's another slant. Two cyclists are on turbo trainers each linked to a generator which feeds electricity back into the mains. They don't even have to be the same weight or height.
Assuming they both wanted to generate 100w output for an hour every day for a year.......would their energy intake cost.....ie cost of food.....be exactly the same or could one be "more efficient" and need less food bought to generate the 100wh (x365s)?
I realise of course that whether that efficiency is natural or can be improved by training is another question.
People seem to vary a bit as to weather it is 4x, 5x or whatever - but the question is whether this variation is something you are born with or if it responds to training. So your two cyclists would probably need slightly different amounts of food, but that may or may not be anything to do with how fit they are.0 -
Some of the efficiency of the human energy would be dictated by genetic factors and some training gains would make the requirement for food less in one of the humans. As I have stated above, the efficiency gains are not large and may be less than genetic differences, I suspect. For example, cadel Evans has a notoriously high vo2 max, much of which is genetically determined. This means his ability to use o2is greater per minute, some of which leads to gains in efficiency ( his carburettor is better). The efficiency gain lies in his ability to use more O2 in a cardiac cycle(heartbeat) replace this O2 via his lungs and transport more O2 in the next heartbeat. His use of energy substrates is at a higher rate per physiological cost ( energy required to move the o2 around).YIMan wrote:Here's another slant. Two cyclists are on turbo trainers each linked to a generator which feeds electricity back into the mains. They don't even have to be the same weight or height.
Assuming they both wanted to generate 100w output for an hour every day for a year.......would their energy intake cost.....ie cost of food.....be exactly the same or could one be "more efficient" and need less food bought to generate the 100wh (x365s)?
I realise of course that whether that efficiency is natural or can be improved by training is another question.
When you're operating at 180 bpm up a col I imagine this makes a difference.0 -
All very interesting stuff!0
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I'm completely out of my depth i this conversation. But thought I'd chuck in a observation that might shed some light?
When i'm on my exercise bike it shows calories burnt - i assume as a direct correlation to power produced.
I also wear a HRM which also calculates calories burnt, presumably from some calculation based on how "hard" I'm working.
The HRM total is always way lower than the bikes (about 2/3rd I noticed today after a 1.5 hour session)
And interestingly to this debate, over time as I have got fitter the gap between the two seems to be increasing.
I have assumed that this is because as i get fitter it's taking me fewer heart beats per minute to deliver the same power?
I'd also assumed that the difference is because who ever made the bike calibrated it to a non-cyclists metabolism.
I've not been recording what the bike has been calculating so this is an impression only - I've no hard data I'm afraid.0 -
Ah, OK, I see what you are saying now. This is a subtly different type of efficiency from what I was talking about, but yes, it will lead to a greater percentage of total energy consumed being converted into muscular energy in the legs, because slightly less muscular energy in the heart and lungs is being used for each unit of energy available to the legs.Wily-Quixote wrote:His use of energy substrates is at a higher rate per physiological cost ( energy required to move the o2 around)..
True chemical/metabolic efficiency may still be the same - the same amount of energy may be "wasted" as heat, but of the remainder that is available to do mechanical work, a slightly greater percentage could go into making the legs work as opposed to making the heart and lungs work..
Efficiency has many levels...
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The HRM estimate of Calories burned will probably be very inaccurate, it is just making wild assumptions about energy used based on your weight and heart rate which may be out by a long way. And yes, as you get fitter you will produce more power at lower heart rates, so your HRM, which doesn't know how much power you are producing, will just assume you are burning less Calories.philwint wrote:I'm completely out of my depth i this conversation. But thought I'd chuck in a observation that might shed some light?
When i'm on my exercise bike it shows calories burnt - i assume as a direct correlation to power produced.
I also wear a HRM which also calculates calories burnt, presumably from some calculation based on how "hard" I'm working.
The HRM total is always way lower than the bikes (about 2/3rd I noticed today after a 1.5 hour session)
And interestingly to this debate, over time as I have got fitter the gap between the two seems to be increasing.
I have assumed that this is because as i get fitter it's taking me fewer heart beats per minute to deliver the same power?
I'd also assumed that the difference is because who ever made the bike calibrated it to a non-cyclists metabolism.
I've not been recording what the bike has been calculating so this is an impression only - I've no hard data I'm afraid.
Assuming that the exercise bike is measuring power correctly, it will be converting power over time into kilojoules of energy (which can be done exactly), and then probably assuming that the number of Calories burned equals the number of kilojoules of energy measured. It so happens that one Calorie equals 4.184 kilojoules (so you should really divide kilojoules by 4 to get Calories), but because you are burning around 4 times more energy than reaches the cranks, this about cancels out, so kilojoules measured approximately equals Calories burned. This is nicely explained in the Allen & Coggan book, "training and racing with a power meter" (which is where I learned about it..). The accuracy of the Calories estimate will depend on how close your personal metabolic efficiency is to 25%.0 -
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neeb, absolutely - and succintly put.neeb wrote:
Ah, OK, I see what you are saying now. This is a subtly different type of efficiency from what I was talking about, but yes, it will lead to a greater percentage of total energy consumed being converted into muscular energy in the legs, because slightly less muscular energy in the heart and lungs is being used for each unit of energy available to the legs.Wily-Quixote wrote:His use of energy substrates is at a higher rate per physiological cost ( energy required to move the o2 around)..
True chemical/metabolic efficiency may still be the same - the same amount of energy may be "wasted" as heat, but of the remainder that is available to do mechanical work, a slightly greater percentage could go into making the legs work as opposed to making the heart and lungs work..
Efficiency has many levels...
i don't know if there are other efficiencies to be gained, its a long time since i've looked at the science behind fitness, I'll have a look today to see if I can find anything that's not straight off the top of my head.0 -
In this post I'm defining efficency as:
'The ratio between mechanical work and the energy consumed to do the work is defined as mechanical efficiency (Winter 1990)'
Some factors leading to increased efficiency in trained endurance athletes:
1.training leads to a higher preponderance of Type 1 mucle fibres (slow twitch) which operate at greater efficiency than type 2 fibres " possibly because of a lower ATP turnover during contraction shortening" (Hawley, 2002), this percentage of type 1 fibres is relative to the number of years of endurance training. In a study by Coyle et al studying efficiency of bicycling at a constant rate (in watts) it was determined that presence of Type 1 muscle fibres was the greatest factor influencing efficiency of cycling. Furthermore, Hawley (2002) states:
"Because type I fibres possess a higher capillary density and oxidative potential than type II fibres, it not surprising to find that a high proportion of type I fibres in the vastus lateralis muscle is associated with a lower submaximal oxygen cost (i.e. a greater gross efficiency) during exercise, possibly because of a lower ATP turnover during contraction shortening. Furthermore, the energy cost per unit force per cross-sectional area is greater in type
II than type I muscle."
2. switch to fat burning pathway in aerobic exercise. Chavarrel (1999) states:
"The efficiency of muscular contraction reflects the product of phosphorylation effciency with which chemical energy from carbohydrate and fat is converted to adenosine triphosphate, and the contraction-coupling effciency with which the energy released during ATP hydrolysis is converted in mechanical energy through muscle shortening"
essentially trained athletes can convert food-energy with less waste: efficiency
3.increased buffering (neutralisation) of metabolic acids in trained individuals, this means that energy utilisation is hampered in untrained individuals - they cannot maintain a given effort due to impairment of glucose/fatty acid metabolism by mitochondria in the presence of acids. Ettema (2009) states that there is little reliable evidence to state that elite athletes are more efficient, except at higher work rates - this is consistent with principle 3.
Finally,
: from Hopker in: Medicine & Science in Sports & Exercise
Issue: Volume 41(4), April 2009, pp 912-919
"...the effect of long-term endurance training on GE (GE=gross efficency energy/O2 ratio). Coyle (8) observed an 8% increase in GE over a 7-yr period in one elite cyclist. Others (11,16) have also demonstrated significant increases in GE as a result of training, albeit in untrained individuals. Consistent with the present study, Barbeau et al. (1) found that elite cyclists' V·O2 was lower at 250 W during the months of May and July, thus demonstrating an adaptation from the high-volume phase of training. "
"A putative mechanism for the increase in GE is a transformation of muscle fiber type characteristics (8). Riders with a high percentage of Type I fibers are able to produce significantly more work for a given V·O2 (18).
Muscle typology is unlikely to be the sole determinant of GE though. Several studies have found that the changes in economy or GE could be induced by alterations in muscle recruitment and pedaling strategies (5,20,36). A reduction in ventilation (VE) could also contribute to an increase in GE, and an inverse correlation between these variables was found in the current study. Reducing the metabolic demand of the respiratory muscle has been shown to decreases the O2 cost of exercise (12)."
hope this helps.0 -
Finally,
: from Hopker in: Medicine & Science in Sports & Exercise
Issue: Volume 41(4), April 2009, pp 912-919
Yep - and thank you for posting the references.
I think the question has been answered. Shame we don't have numbers for the untrained individual only the elite, but I am assuming in the context, "significant" is substantially more than 8%.0 -
Good question, I guess initially the motor gets bigger, then more efficient as Type 1 muscle proportion increases. Finally, incremental gains would be experienced as neuromuscular conditioning is fine tuned.
The 8% gain in efficiency in one cyclist over 7 years is interesting... i wonder if this is from further morphological changes or neuromuscular efficiencies - 'souplesse'? either way it fits the picture of young riders maturing and becoming better stage racers as the years progress.
I read a paper comparing efficiency of cycling in normal individuals and anaesthetised individuals with the leg muscles stimulated by electrical transmission! Not surprisingly, efficiency is also a factor of synchronised neuromuscular activity.As you'll see when you see a newbie stomping the pedals up a hill.0 -
Unless I'm misunderstanding that lot, they appear to define efficiency as energy_output/oxygen_consumed (certainly 1 & 4 do - 2 doesn't and 3 explicitly states that there is no evidence that elites are more efficient except at higher intensity - where presumably the anaerobic pathway comes into play). Whilst this is a more more useful definition of efficiency, I'm not sure it answers the question asked - i.e. how does energy_output/energy_input vary with training?0
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@Froomes Edgar - I think Wily-Quixote answered that on page 5, where he/she talks about the inefficiency of recycled energy in the blood. The untrained/unfit rider is wasting energy pushing fuel around his/her body that he cannot use, because his/her "engine" cannot suck any more fuel out the system. Using the analogy of a car engine, it is more like two engines with different sized radiators. In both engines the energy required to pump the coolant and fan the radiator is broadly the same, but the engine with the bigger rad will get more cooling. Thus if engine temp is the key factor, the engine with the smaller rad will not perform as efficiently or will have to pump the coolant faster or run the fan faster to achieve the same.0
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Interesting debate (despite what some might think who have blacklisted one side of the argument). I think people are confusing whether the less fit rider requires more energy with will the less fit rider find it harder going. All other things being equal (weight, air resistance etc.) the power required to get to the top will be the same. Power is energy per second so therefore other than the minor internal discrepancies regarding efficiency (some of which may be controllable through better riding technique, others will be dependent on your natural physiology) both riders use the same energy. However, the less fit rider may have to work at (say) 95% of their maximum whilst the fitter rider is only at (say) 80% and will therefore fatigue more quickly. This is the reason a trained athlete will manage the climb more easily, it's nothing to do with using more energy.
i suspect the confusion arises out of the misuse of the word energy. You often hear people say they have run out of energy but I doubt they have, what they mean is they are lacking fitness.0 -
I think after about page 2 we'd moved on from discussing energy in pure physics (mass, distance, speed, elevation) terms and more about the biological processes to turn input (food/air) in to output.
The debates is thus:
1. its broadly the same because study X says...
2. its substantially different because study Y says..
for me 2 seems to be convincing, purely because we have seen substantially less references for 1. But I am open to both.0 -
Surely it's all about efficiency?
The rider will gain the same gravitational potential energy but the efficiency in which that is gained is different for each rider and is in fact a completely separate thin.
If you extrapolate the argument, what takes more energy - driving up the mountain or getting a helicopter up? This is directly analogous to the situation being discussed but as far as I know the helicopter would use MUCH more fuel than the car right?
So, to reiterate, the final resting state (i.e. height up the mountain, and potential gravitational energy) has no real relation on the energy expended to get there but merely state the MINIMUM energy required to meet that state.
It's been a long time since I did A-level physics (and chemistry degree) but to me it seems fairly obvious?Cannondale CAAD 10 Ultegra
Kinesis Racelight Tiagra0 -
nawty wrote:Surely it's all about efficiency?
The rider will gain the same gravitational potential energy but the efficiency in which that is gained is different for each rider and is in fact a completely separate thin.
If you extrapolate the argument, what takes more energy - driving up the mountain or getting a helicopter up? This is directly analogous to the situation being discussed but as far as I know the helicopter would use MUCH more fuel than the car right?
So, to reiterate, the final resting state (i.e. height up the mountain, and potential gravitational energy) has no real relation on the energy expended to get there but merely state the MINIMUM energy required to meet that state.
It's been a long time since I did A-level physics (and chemistry degree) but to me it seems fairly obvious?
Yes, it is all about efficiency i.e. the input energy required to achieve the output energy. But the output energy is directly related (but not exactly the same due to air resistance/friction etc) to the potential energy gained by ascending the hill. That potential energy gained is directly related to the mass of the item you are moving up the hill.
So if the helicopter and car were the same weight and ascended at the same rate....relative efficiency? The helipcopter's blades are overcoming a much greater force from air resistance due to their very high speed. But the car has to overcome some friction due to the contact with the ground. The different designs of engine have a bearing on it too. I'd say the helicopter is much less efficient but that's an assumption, not calculated.0 -
@Froomes Edgar: I probably was a little unclear, when I stated that elites are no more efficient I was referring to one authpr's interpretation of the evidence. other studies I read, some of which i quoted, certainly show that their are efficiency gains with training. I apologise if this appears blurry, but this is the nature of academic papers: results from a study aren't 'proof' they are just added bits of evidence to add to the overall picture and each individual study has constraints and limitations that limits their applicability to the real world. I am not a sports physiologist either, so this is not my area of expertise - although i work in the health sciences.
Also just to clarify: we have to be certain that we are talking about the same thing: efficiency to me is the measured as the conversion of glucose/fatty acids (energy substrates) per O2 per work output (joule), if the rate of work output is a constant (ie on an exercise bike at given speed) relative efficiency can be measured by glucose/O2: this is known in the literature as gross efficiency (GE) and is mentioned in the exerpts above.
The other form of efficiency often quoted is Delta Efficiency (DE) which is interesting because it measures efficency when a load changes, and is thought tomore accurately measure efficieny because it removes baseload metabolism from the equation, despite this most authors I read use GE as the measure.
The other confounding principle is mechanical efficiencies of the biomechanical structures and the internal musculotendinous structures themselves and other factors such as cadence, not specifically related to the discussion but i read some very intersting articles on cadence- topic for another discussion...
Anyway back to your question: :how does energy_output/energy_input vary with training"
Energy input into a system relates to energy consumed, either by blood glucose from ingested food or glycogen in muscles/liver converted to glucose or by fatty acids- I don't see that this relevant to the discussion, except to say that that glycogen stores increase in muscle tissue in the trained individual and combustion of glucose can occur more rapidly because of better O2 delivery (cardiovascular modification) and more oxygen present in the muscle itself (myoglobin) I don't see this as an efficieny difference in trained individuals more a delivery difference (turbocharging the engine).
If your question about input is: 'does a trained athlete need to eat less for a given energy output' the answer is yes: yes because their muscles work more efficiently (less energy/O2 consumed per output due to more efficient combustion within the mitochondrion of the cell), because less energy is wasted per cardiac stroke (as alluded to above and what DIY said), because wastes are cleared more quickly (exhaust system is better) and because they are more mechanically efficient (neuromuscular adaptation - efficient muscular recruitment leading to less energy wastage, seen as a smooth 'souplesse' pedalling motion).
The other part of your question asked about energy output varying with training. I can't answer this question as it is too large in scope: what is your definition of energy output? do you mean explosive sprint power? Endurance? Force of muscular contraction? I'll answer the question briefly as to how it's generally been posed in the original question: climbing ability. A trained athlete can output more power, obviously, the reason is the muscular and cardiovascular adaptations give the trined cyclist a bigger engine, this engine is more efficient also. In effect the trained rider can match pace with an untrained rider up a hill; and, all else being even (weight, bike, friction etc.etc.) the trained rider will have used LESS energy as the untrained rider. Why? because they are more efficient, they use less energy substrate and O2 for a given power output.0
