Cadenta corecta

Forţa necesară pentru a deplasa bicicleta pe şosea se măsoară în watts. Creşterea sau scăderea numărului de watts este dată de forţa+cadenţa, sau pe înţelesul tuturor bicicleta se deplasează mai repede cu cât forţa şi numărul de rotaţii pe minut sunt mai mari.

Exemplu:

Doi ciclişti, George şi Andrei, au aceeaşi greutate, au acelaşi tip de bicicletă şi acelaşi profil aerodinamic. Cei doi pedalează pe aceeaşi şosea, unul lângă celălalt. Cei doi merg cu aceeaşi viteză dar George are o cadenţă de 70 rpm iar Andrei învârte angrenajul cu o cadenţă de 110rpm. Stilul de pedalare al lui George îl face să apese cu mult mai multă forţă în pedale, în timp ce stilul de pedalare al lui Andrei îi permite să apese mai uşor dar îl obligă să învârtă angrenajul mult mai des.

Dupa cum se ştie există două tipuri de fibre musculare (aşa numitele fibre roşii/rapide şi cele albe/mai lente). Ceea ce este discutat mai puţin este însă proporţia între cele două tipuri de fibre. Această proporţie este de asemenea determinată genetic (cel puţin după cercetările ştiinţifice actuale). Proporţia fibre rapide/lente poate varia nu numai între indivizi ci chiar la aceeaşi persoană, de la un muşchi la altul, de unde şi dificultatea de a dezvolta anumite grupe musculare comparativ cu uşurinţa de a dezvolta alte grupe, la acelaşi individ.

Să vedem acum avantajele şi dezavantajele:

Fibrele albe (lente):

* Utilizează grăsimea ca şi “combustibil”.
* Sunt foarte rezistente la oboseală.
* Permit o recuperare rapidă când se intră în repaos.

Fibrele roşii (rapide):

* Utilizează glicogen ca şi “combustibil”. Glicogenul este depozitat în muşchi  (400g la un atlet de 75 kg; corpul produce standard 60g/h, dar corect ajutat de fructoza poate produce 90g/h) dar cantitatea înmagazinată este relativ mică, cca 2.000 de calorii pentru un sportiv foarte bine antrenat. Aceasta cantitate poate fi crescuta prin tehnici de carbo-loading: cu 3 zile înainte de eveniment se fac exerciții ușoare cu un sprint de 3 minute, după încălzire și recuperare cu nutriție adecvata (fructoza mai multa, 2:1)
* Oboseala apare mai uşor, nu sunt construiţi pentru a rezista mult timp.
* Timpul de recuperare este mai lung.

Mai precis, avem următoarele caracteristici:

Table 1: Characteristics of the Three Muscle Fiber Types
Fiber Type	Slow Twitch (ST)	Fast Twitch A (FT-A)	Fast Twitch B (FT-B)
Contraction time	Slow	Fast	Very fast
Size of motor neuron	Small	Large	Very large
Resistance to fatigue	High	Intermediate	Low
Activity used for	Aerobic	Long term anaerobic	Short term anaerobic
Force production	Low	High	Very high
Mitochondrial density	High	High	Low
Capillary density	High	Intermediate	Low
Oxidative capacity	High	High	Low
Glycolytic capacity	Low	High	High
Major storage fuel	Triglycerides (FAT)	CP, Glycogen	CP, Glycogen

Acum să ne imaginăm că avem o soba în care băgăm lemne. Avem butuci groşi care ard mocnit şi bucăţi de lemn de brad care ard rapid dar scot o flacără puternică. În funcţie de cum vrem să ardă focul aşa trebuie să folosim lemnele. Antrenamentele ne permit să creştem “magazia de lemne”. Turele scurte ne permit să folosim fibrele roşii(lemnul de brad) iar cele lungi necesita utilizarea fibrelor albe. Totul este bine atâta timp cât magazia nu se goleşte.

După atâtea figuri de stil să revenim la partea cea mai interesanta, la întrebarea care îi macină pe mulţi dintre cei care încep să pedaleze mai serios.

Ce cadenţă să folosesc?

Să spunem că pedalaţi pe un drum drept şi în faţă apare un deal. Pentru a ajunge în vârful dealului aveţi nevoie de 1 minut. Care sunt cele mai probabile situaţii:

1. O să schimbaţi pe viteza care vă convine. Vă simţiţi bine pe o cadenta de 60-70rpm aşa că o să mergeţi cu acea cadenţă, poziţionaţi undeva la mijlocul casetei de pinioane.

2. O să abordaţi căţărarea cu 60rpm pentru ca nu aveţi pinioane mari. Caseta de 11-21 este ideală pe plat dar iată că în acest moment nu vă permite să pedalaţi cu mai mult de 60rpm.

3. Un gând vă trece prin minte; “Dealul ăsta îmi ia doar un minut. Nu vreau să pierd timp aşa că o să mă ridic din şa şi o să pedalez în forţă. O să îmi revin pe coborâre.”

4. O să schimbaţi pe pinionul de 27 şi o să urcaţi dealul cu o cadenţă de 90-95rpm.

Să analizăm acum aceste lucruri

Opţiunea #1: cadenţa mica = forţa mai mare = utilizare fibre roşii = ardere glicogen de care probabil o să aveţi nevoie la finalul turei. Uitaţi termenul “pedalare în forţa” , forţa risipită nu înseamnă nimic, important este câţi watts se transferă angrenajului, roţii şi pe urmă pe şosea. Dacă puteţi urca un deal cu aceeaşi viteză la 60rpm ori la 90rpm, alegeţi 90rpm. Protejaţi rezervele din muşchi pentru perioade mai dificile.

Opţiunea #2: Încearcă să ai tot timpul în minte opţiunea#1 şi foloseşte întotdeauna combinaţia corecta de pinioane. Mulţi amatori au două seturi de pinioane, un 11-21 pentru plat şi un 12-27 pentru turele în munţi. Nu există căţărare care să vă reziste dacă aveţi o combinaţie corectă.

Opţiunea #3: Ridicat din şa = pedalare în forţă = utilizare fibre roşii = cunoaşteţi povestea deja. Este foarte posibil să vi se pară ok această abordare dar cu siguranţă o să simţiţi la sfârşitul turei că nu mai aveţi lemne de pus pe foc.

Opţiunea #4: Bingo! Cadenţa mare până în vârful căţărării, utilizarea fibrelor musculare de anduranţă, tot ce aveţi nevoie pentru a ajunge primul în vârf. Pentru a maximiza arderea grăsimilor trebuie folosita o intensitate de 60-80%. Intensitatea se măsoară după ritmul cardiac, maximul personal se determina prin relația 220 - vârsta în ani)

Care este până la urmă cadenţa ideala?

Până acum am înşirat o poveste şi avantajele cadenţei ridicate faţa de pedalarea în forţă. Care este totuşi cadenţa cea mai buna? Se pare ca majoritatea profesioniştilor pedalează cu o cadenţă de 88-95+rpm. Rusii au facut un studiu cu caţiva ani in urma si au ajuns la concluzia ca 92rpm este cadenţa ideală.

Atentie! Cadenta cu care abordati o catarare nu trebuie sa fie mult mai mare decat cadenta cu care mergeti pe plat. Daca ati pedalat cu o cadenta de 80rpm timp de doua ore si apoi vreti sa urcati un munte cu 90rpm o sa cereti de fapt picioarelor sa faca un efort imens.

Tineti minte! Dacă sunteţi începători este foarte probabil ca în acest moment pedalaţi sub cadenţa optimă. Antrenamentul, intervalele de spinning la frecvenţă mare dar şi experienţa, o să vă aducă la un nivel corect.

Încercaţi să vă antrenaţi în aşa fel încît să obţineţi un maxim de watts la o cadenţă specifică. Sugestia mea este să utilizati o cadenţă în jurul valorii de 90rpm (cei mai puţin experimentati chiar mai mult de atât).

sursa: http://ciclism.ro, comentata de Valentin Cornaciu

Trazitul intestinal

How long does food stay in my stomach? How long is it before a meal reaches the large intestine? The answer to such commonly-asked questions is not necessarily simple.

First, there is considerable normal variability among healthy people and animals in transit times through different sections of the gatrointestinal tract. Second, the time required for material to move through the digestive tube is significantly affected by the composition of the meal. Finally, transit time is influenced by such factors as psychological stress and even gender and reproductive status.

Several techniques have been used to measure transit times in humans and animals. Not surprisingly, differing estimates have been reported depending on the technique used and the population of subjects being evaluated. Some of the techniques used include:

• Radiography following a barium-labelled meal. Sequential radiographs can be used to determine when the front of the barium label reaches different regions of the digestive tube. Such meals are not very physiologic and the technique exposes the patient to repeated exposure to radiation.
• Breath hydrogen analysis. A number of carbohydrates are very poorly digested or absorbed in the small intestine, but readily fermented by bacteria when they reach the large intestine. Fermentation liberates hydrogen gas, which diffuses into blood and is exhaled in breath, where it can be readily measured. Thus, after consumption of a meal containing a non-absorbable carbohydrate (lactulose or, more commonly, baked beans), there is a large increase in exhaled hydrogen when the carbohydrate reaches the large intestine. This provides an estimate of pre-colonic (stomach plus small intestine) transit time.
• Scintigraphic analyses. Meals containing pellets or colloids labelled with a small amount of radionuclide (^99mTechnetium, ^113mIndium, etc.) are consumed, and the position of the radioactive label is sequentially monitored using a gamma camera.

Studies of gastrointestinal transit have clearly demonstrated two related phenomena important to understanding this process:

1. Substances do not move uniformly through the digestive system.
2. Materials do not leave segments of the digestive tube in the same order as they arrive.

In other words, a meal is typically a mixture of chemically and physically diverse materials, and some substances in this mixture show accelerated transit while others are retarded in their flow downstream.

An example of how ingested substances spread out in the digestive tube rather than travel synchronously is shown in the figure below. These data were obtained from a human volunteer that ingested a meal containing ¹¹¹Indium-labeled pellets, then measuring the location of the radioactive signal over time by scintigraphy. It is clear that parts of the meal are entering the colon at the same time that other parts are still in the stomach.

The discussion above should help to explain why it is difficult to state with any precision how long ingesta remains in the stomach, small intestine and large intestine. Nonetheless, there have been many studies on GI transit, and the table below presents rough estimates for transit times in healthy humans following ingestion of a standard meal (i.e. solid, mixed foods).

50% of stomach contents emptied	2.5 to 3 hours
Total emptying of the stomach	4 to 5 hours
50% emptying of the small intestine	2.5 to 3 hours
Transit through the colon	30 to 40 hours

Remember that these are estimtes of average transit times, and there is a great deal of variability among individuals and in the small person at different times and after different meals.

sursa: Author: R. Bowen

Starea noastra de spirit

Au nume interesante - dopamina, serotonina, endorfina, noradrenalina - si au capacitatea de a ne face sa vedem viata în roz. Sunt, de fapt, niste hormoni, neurotransmitatori, si sunt implicati în reglarea starii noastre de spirit. De noradrenalina depind dinamismul si capacitatea noastra de concentrare.

• Zvapaiata noradrenalina

Izvorâta din cortex - asa-zisul creier instinctiv, care vegheaza la supravietuirea speciei - noradrenalina este în primul rând hormonul dorintei. Ei i se datoreaza vitalitatea instinctiva, precum si pulsiunile sexuale. Fara aceasta seva a vietii, dorinta de a mânca, de a dormi si de a începe o noua zi, de a lupta pentru ceva n-ar exista. Dorinta sexuala ar fi, de asemenea, absenta. Problema este ca, în timp, rezerva de hormon se diminueaza, epuizându-se lent. Dificultatile cotidiene, situatiile solicitante repetate, stresul consuma cu o viteza mai mare sau mai mica aceasta comoara a dorintelor vitale. Din fericire, industria farmaceutica detine o serie de stimulente si substitute ale acestui hormon, la care, sub îndrumare medicala, se poate apela.
Si acum, hormonul care are ca sediu zona din creier destinata memoriei, afectului si umorilor.

• Dopamina, regina sentimentelor

Când dopamina someaza, libidoul (dorinta sexuala) lasa de dorit iar starea de spirit e la pamânt. Treptat se instaleaza depresia, diminuarea capacitatii de concentrare, dificultatea de a transpune ideile si hotarârile în practica. Iesirea din aceasta deriva e posibila, cel mai la îndemâna fiind alimentatia bogata în vitaminele B6, B9, B12, C, fier si magneziu.

• Serotonina, frâna agresivitatii

În timp ce noradrenalina face oficiul de accelerator al reactiilor, serotonina apasa pe frâna, pentru a crea un echilibru. De fapt, ea tine în frâu agresivitatea noastra. Pentru cel putin 25% din indivizi, aceasta sarcina nu este deloc usoara pentru ca ei se nasc cu acceleratorul mai puternic decât frâna, ceea ce înseamna ca violenta, nerabdarea, iesirile colerice, tendinta spre bulimie, angoasele etc. sunt mai greu de controlat. si pentru carenta de serotonina exista însa remedii: consumul controlat de glucide cu timp lent de metabolizare. Câte o tableta de ciocolata sau o doza mica de alcool este de asemenea acceptata de specialisti, desi recomandarea numarul 1 este cea legata de practicarea de activitati care pot depresuriza tensiunile interioare (sport, diferite hobby-uri). Iar consumul de alimente bogate în magneziu, ca si administrarea de suplimente farmaceutice pe baza de magneziu sunt deopotriva de luat în calcul, deoarece ajuta la reducerea stresului.

• Endorfina, miraculosul antistres

Moleculele de endorfina, descoperite în 1970, au o proprietate uimitoare, asemanatoare medicamentelor împotriva durerii, cum ar fi morfina. Ele aduc starea de liniste si confort interior. Cheia magica este sportul. Potrivit cercetarilor efectuate, cantitatea de endorfine poate fi crescuta de cinci ori daca se practica minimum 45 de minute de sport de anduranta, cum ar fi jogging, înot sau ciclism. Alte surse de endorfine sunt râsul, ciocolata si actul sexual. Având rol antistres, endorfinele favorizeaza recuperarea fizica si psihica, precum si somnul odihnitor. Fiind comparabile cu opiaceele, ele calmeaza durerile si migrenele.

Unde se gasesc?
Noradrenalina. În gelule farmaceutice
Dopamina. În drojdie de bere, germeni de grâu, nuci, seminte de floarea soarelui, cacao, migdale, ciuperci, ton, sardele, oua, lapte etc.
Serotonina. În glucidele lente (cereale, paste, cartofi, mere, struguri etc.).
Endorfina. În ciocolata si activitatile sportive.

Spune-ne ce te doare şi-ţi spunem ce sport să faci

Sportul nu este doar cea mai bună modalitate de a ne menţine în formă. Exerciţiile fizice ne ajută şi la tratarea bolilor.

Specialiştii spun că anumite tipuri de exerciţii fizice ne ajută să reducem simptomele afecţiunilor de care suferim, informează Daily Mail în ediţia electronică.

• Depresie - mersul pe jos, grădinăritul

Un studiu efectuat de cercetătorii americani sugerează că trei plimbări energice pe săptămână, de 30 minute fiecare, sunt mai eficiente în tratarea depresiei decât antidepresivele. Şi grădinăritul şi-a dovedit eficienţa în diminuarea depresiei.

• Diabet - exerciţii cu greutăţi, aerobic

De obicei, persoanele cu diabet tip 2 sunt sfătuite să efectueze exerciţii de aerobic (înot, alergări sau ciclism), pentru a reduce cantitatea de grăsime şi pentru a controla nivelul glucozei. Un studiu condus de profesorul Robin Marcus, de la American Physical Therapy Association, arată că exerciţiile cu greutăţi pot ajuta la scăderea indicelui de masă corporală.

• Migrene - ciclism

Activităţile de anduranţă, precum mersul cu bicicleta şi canotajul cresc concentraţia de endorfine, hormoni care acţionează în calitate de "analgezice" naturale. Ciclismul, spun cercetătorii, reduce frecvenţa migrenelor cu până la 90%, atunci când este efectuat 30 de minute, de 3-4 ori pe săptămână.

• Hipertensiune arterială - drumeţii

Fiziologii de la Institutul de Cercetare Oregon au constatat că mersul pe pietre a condus la reduceri semnificative ale tensiunii arteriale. În medicina chineză, se consideră că suprafeţele denivelate ar stimula anumite puncte de pe talpă, responsabile de reglarea tensiunii.

• Osteoporoza - alergare

Pam Hinton, profesor de nutriţie şi psihologie la Universitatea din Missouri, a comparat efectele alergărilor, ciclismului şi antrenamentelor cu greutăţi asupra densităţii osoase şi a descoperit că persoanele care aleargă în mod regulat au oase mai puternice. Medicii recomandă 30 de minute de alergări, de 3-5 ori pe săptămână. De asemenea, tenisul şi baschetul fac parte din activităţile care ajută la prevenirea osteoporozei.

• Sindromul de colon iritabil - yoga

Deşi nu se cunosc cauzele exacte ale bolii, gastroenterologii de la Universitatea British Columbia din Vancouver au descoperit că yoga este cea mai eficientă practică în cazul acestei afecţiuni. Medicii spun că, după o săptămână de yoga, pacienţii au înregistrat o ameliorare semnificativă a simptomelor. Un alt studiu al medicilor de la Universitatea din Birmingham a arătat că 30 de minute de activitate fizică (înot sau exerciţii acvatice), timp de cinci zile pe săptămână, reduc simptomele bolii.

• Dureri de spate - tehnica Alexander

Inventată de Frederick Matthias Alexander, un actor australian cu probleme de respiraţie, această metodă ajută corpul să obţină o postură corectă. Tehnica ne învaţă cum să ne utilizăm corect propriul corp - cum să ne mişcăm, să stăm drepţi, să respirăm, să învăţăm, cum ne organizăm concentrarea şi atenţia. Pe lângă această tehnică, mai puteţi încerca şi pilates - metoda care întăreşte muşchii spatelui.

• Afecţiuni gingivale - aerobic

Cercetătorii de la Western Reserve University Case din SUA au constatat că cinci sesiuni de activitate fizică moderată pe săptămână, combinate cu o alimentaţie sănătoasă şi un regim de sănătate orală, reduc riscul bolilor gingivale.

de Milena NIŢĂ | 14 SEPTEMBRIE 2009
sursa: gandul

CYCLING PERFORMANCE TIPS

EXERCISE PHYSIOLOGY - ENERGY REQUIREMENTS OF BICYCLING

The energy requirements for a ride are dependent on:

• the weight of the cyclist and equipment
• the distance
• the terrain (flat versus hilly)
• the speed of the ride
• headwinds or tailwinds

And the Calories to fuel the ride are supplied (via the intestinal tract)from food eaten just before or on the ride, or from the body's internal energy reserves (fat, glycogen) in the liver, fatty tissue, or in the muscle itself.

ENERGY - POWER, CALORIES & WATTS

Before we go any further, let's review the terms energy, force, power, Calories, and watts which are often used interchangeably. Energy is the ability to perform work. The presence of energy is revealed only when change takes place. Potential energy is stored energy (the energy which will let you roll down the hill on your bike, starting from a dead stop, without ever pedaling). Kinetic energy is the energy of motion (the energy contained in you - and your bike - when already rolling down that hill and evident if you run into someone while in motion). The measurement units for energy (either potential or released) are calories or Calories.

Force is the ability of that energy to make a change - to change the state of rest or motion in matter. When force is actually applied, work (force applied over some distance) is done. The same amount of work is done if the task is accomplished in 5 seconds or 5 minutes. The rate at which the work is done is power - the more work per minute or second, the more powerful the force applied to do that work. And watts are the units used to measure power. The more force applied to accomplish the task in a shorter period of time, the more work done and the more power required to do it.

Energy output can be expressed in absolute terms (time interval independent) or in as energy released over a specified or defined time interval (time interval dependent). The most common time independent energy unit used in the cycling literature is the Calorie. In the physical sciences (physics, chemistry), a calorie (small "c") is the quantity of energy required to raise the temperature of 1 gram of water 1 degree centigrade. As this unit is too small to easily express the energy needs of biologic systems, the Calorie (large "C"), which is equivalent to 1000 calories (small c again) or 1 kcal is often used. Unfortunately most nutritionists forget to capitalize the "C" when they are writing about "calories" (they really mean Calories), so don't get confused. If the energy released is measured over a set period of time, it is expressed in watts, and is a reflection of power.

Approximately 60% of the Caloric energy from the food we eat is lost as heat during the fabrication of ATP (adenosine triphosphate), the high energy, intermediary molecule actually used by the muscle cell to power muscle contraction. Additional energy, again reflected as heat production, is lost when ATP is metabolized in the actual mechanical work of muscle fiber contraction. The net result - only 25% of the Caloric energy in the food we eat is actually used to power the mechanical work of the muscle cells. The initial heat loss associated with the conversion of Calories in food into ATP occurs slowly over several hours and is easily compensated for by our body's temperature control mechanisms, but the heat produced with the metabolism of ATP to power muscle contraction is concentrated over a shorter period of time and is why our body temperature rises (and we sweat to compensate) when we are exercising.

Our bicycle, on the other hand, is very efficient in terms of energy loss. Over 95% of the muscle energy we use at the pedals is translated into forward motion and less than 5% is lost (again as heat) from the rolling resistance of the tires, bearing friction, etc. Some of the things we can do to increase the efficiency (decrease resistance losses) are:

• keep bearings and chain well lubricated
• use light oil in bearings and bottom bracket for time trials
• use light greases - paraffin gives more resistance than grease
• use tires with a small "footprint"
• keep tires maximally inflated to decrease rolling resistance
• use thinner, more flexible tires (less energy taken up in sidewall deformation)

Curt Austin has put together a nice calculator to estimate power output (in Watts - you enter your own parameters) on his website. As energy used in Watts is directly proportional to Calories, this calculator will let you play with the numbers for weight, position on the bicycle, road grade, and air resistance/wind which we will discuss below.

Here is an interesting question re the ability to "train" to increase power - with a f/u. It is annecdotal, without proof, but is worth considering.

Q. I have added a ballast of 5.5 kg's to my hydration pack (so my buds don't see) to see if I can train with it and then shed it on race day. I also always ride with my Sigma light and battery firmly secured in my water bottle cage(another kg at least) telling my mates its just too much trouble to take it off and put it back on again. I also have my race wheels that are 600g lighter than my traing wheels.

I have read a lot of hill training tips and routines but the underlying goal is to increase your power to weight ratio. So I figured that if I weigh 70KG's and upped that to 77 for training, then shed it on race days, I would be scoring an an increase in my P 2 W ratio which would help me get to the top of the hills in touch with the real climbers. What I have found is, that I don't notice the extra weight once I have the pack on and I'm riding. I just find that when we dice for the crest of the hills my legs are on fire and I may come second, but I am not even thinking about the extra weight. Slowly I have managed to get back to where I was in the ranks of my chain gang with carrying the extra weight. I don't have any power measuring equipment only HR and my HR on the climbs is +-8 BPM higher than before, depending on how steep the climb. I do manage to stay with my mates though. Do you think my plan has merit?

A. If one believes that training (cardio and strength) is the body responding to stress, then adding extra weight for training and shedding for the race should work. I'll be interested to hear about your results. It is the saem concept as doing intervals to increase your cruising speeds. Don't forget to let me know.

F/U Hi Dick, I had a great race today rode 2Hrs 29min 15secs for 100k's. There was no real wind to speak of. I did have some niggly feelings in my legs at about 95k's but no full blown cramps. If I can repeat this performance in November(19th), when I go up to ride the 94.7 in JHB, I'll be really chaffed. It is at an altitude 1500m higher than Cape Town and has a "sort of" climb in the middle of about 7k's 3.2% gradient. The rest of it is rolling hills. My goal there is a sub 2H30.

WEIGHT

The combined weight of the cyclist and equipment impact the energy requirements of a ride. This relationship is directly proportional i.e. a doubling of the weight on the bike doubles the number of Calories expended. And 2 pounds on a cyclist is just as much a problem as 2 pounds of equipment on the bike frame itself. Austin did a nice analysis on the effect of weight on performance. Here's his conclusion: I thought it would be interesting to see how weight would influence these curves. If I lost 10 lbs (about 5%), I would be able to go about 5% faster on the steepest hills, 0.4% faster on the level, and about 2% slower on the downhills. Over a simulated 20-mile closed-circuit ride with a variety of grades, a 10-lb difference produced a 33 second difference. This may or may not seem significant in the context of a time trial. On the other hand, there are two hills on this simulated route where the heavier rider falls back 14 seconds. That is, about 200 feet back and well-dropped. A two-lb difference that you can buy at a bike shop for $500 amounts to only 7 seconds on this circuit, but again, this could mean cresting a hill 50 feet behind your better-sponsored buddies.

HORIZONTAL DISTANCE

Horizontal distance. We all know that it takes more energy the further we carry any object. The same is true in cycling. On level terrain, the number of Calories expended is directly proportional to the distance and doubling the distance (weight remaining the same) will double the number of Calories required.

VERTICAL DISTANCE (hills)

Vertical distance, i.e. climbing a grade or hills requires additional energy as you overcoming gravity (essentially lifting the cycle/rider to a higher elevation). A common question is how speed on the flats compares to speed on an uphill slope. Using Austin's calculator, I first calculated the power output for a 170 pound cyclist & 22 pound bike on the flats at 20 mph. It was 210 watts. Keeping energy output steady (at 210 watts), I then calculated the speed on a 1% (17.25 mph), 2% (14.6), 3% (12.3) and 5% (9.0) grade.

What about descents and hilly terrain? How does weight factor into these riding conditions? You may have noticed that a heavier rider descends a hill faster (energy expenditures being applied to the pedals being equal) than a lighter one. This seems to fly in the face of a fact you learned in physics class about all objects falling at the same speed independent of their weight. But when going biking down a hill, the slope factor needs to be taken into account. The final speed down a long hill is the balance between the propulsive forces - total rider/bike weight x the sine {that's a trigonometric function} of the angle of the hill - and the resistive forces - wind resistance is the big one. And the heavier rider comes out ahead. If one does the exact calculations with twin brothers weighing 175 pounds, descending a medium slope hill, riding similar bikes, and in exactly the same aerodynamic positions, with one carrying 25 pounds of lead shot, the heavier one would go 26.73 mph while the lighter one would be slightly slower at 25 mph.

And what about rolling terrain?? With climbing, the lighter rider has a definite advantage over the heavier one. And in rolling terrain with repeated ups and downs, the lighter rider comes out ahead.

INERTIAL WEIGHT

Finally, weight is a factor in sprints where inertia (the resistance to setting an object into motion - why it is harder to get up to speed on a bike than to maintain that speed) comes into play. It definitely takes more energy to accelerate a heavier rider/bike combination in a sprint. And extra weight in some bike components (rims for example) may require twice as much energy to accelerate as an equal weight in the frame. This is a result of the fact that with rotational speed you are accelerating these components much more quickly. (Note: this means you should upgrade your tires, rims, crankset, and shoes before you spend your extra $$ to decrease your frame weight an equal amount).

The bottom line - the heavier you are, the greater the total energy requirements for your ride. And except for the special case of inertia, all weight is equal. So don't forget that the extra water bottle, the larger heavier tool set, and even that extra pancake you ate in the morning all require additional energy on the ride. And saving a few ounces by eating one less pancake will have as much impact on your performance as that expensive titanium item you've been saving to buy.

AIR RESISTANCE, WIND, AND DRAFTING

Along with the Calories needed to

• counter the effects of gravity
• over come the friction and rolling resistance in the bicycle

you also have to overcome air resistance. That's the resistance produced as we cycle (from the air molecules all around us).

Air resistance increases with your air speed (the velocity of our travel through that mass of air). Even with the best riding technique, a head wind will increase your energy expenditure per mile for any specific ground speed (the speed indicated on your bike computer). With the head wind, your air speed (and air resistance) is now GREATER than your computer indicates, the air resistance is higher than at a similar ground speed in calm conditions, and your energy needs are greater. Likewise a tailwind will decrease our air speed relative to your ground speed and make it easier to maintain any specific ground speed. And worst of all, this relationship is an "exponential" one which means that doubling our air speed MORE THAN doubles the Calories expended per mile traveled.(This graph visually demonstrates the fact.)

A headwind on an out and back course always results in a slower total ride time than for the same course ridden in calm conditions as the time gained on the return trip with a tail wind doesn't make up for the loss from grinding into the wind on the way out. For a 12 mph wind, total time will rise by about 7%.

Remember that the "speed" that determines your energy needs to overcome air resistance is your AIR speed, not the GROUND speed which is read from your computer. When you are calculating energy needs for a ride, it is the air speed that is used. A head wind should be added to your average ground speed to determine your air speed (and thus air resistance) while a tail wind should be subtracted from your ground speed. If you think about it, this makes sense - it is always easier to ride with a tail wind, ground speed staying the same.

At cycling speeds greater than 15 mph (24.1 km/h), the energy needed to overcome AIR RESISTANCE greatly exceed those of the rolling and mechanical resistance in your bike. For example, in going from 7.5 mph to 20 mph:

• mechanical resistance increases by 225%
• rolling resistance by 363%
• air resistance by 1800%.

This is why drafting (which cuts down air resistance) provides such an advantage in high speed events. At 20 mph, drafting a single rider reduced energy requirements (measured by VO2 needs) by 18% and at 25 mph by 27%.

In order to benefit from drafting, you've got to be in the drafting bubble behind the cyclist immediately in front of you. And in a crosswind the bubble will NOT be directly behind the rider in front but will be some angle away from them. The effectiveness of this bubble decreases with the distance, being the greatest if you draft closely and falling off until there is minimal benefit at 5 or 6 feet. The important fact is that you will get some benefit 3, or even 4 feet, back - and it's a lot safer than being directly on the rear wheel of the rider in front of you.

The rider being drafted also gains a slight advantage. This is explained by the fact that the low pressure behind the lead rider is increased in a pace line, giving the leader a slight "nudge" due to the pressure differential between the high pressure ahead and the low pressure behind. This is why a NASCAR racing car will go 1-2 mph faster when being drafted.

Since wind resistance plays such a great role in the overall resistance we get when riding, it makes excellent sense to draft. Better if closer, but that comes with practice and skill as well as trust in the front-rider's smoothness and consistency.

Your frontal surface area affects your air resistance. Wind tunnel results show that eliminating the drag created by projecting 4.5 inches of a pencil into the airstream will provide a 158 foot finish line advantage to a cyclist in a 25 mile time trial. That baggy jersey or upright position may be costing you minutes.

Let's review the factors in air resistance again:

Air resistance =.5*(rho/g)*Area*Cd*V^2

• rho=air density
• g=gravity
• area= frontal area of the rider and bike (scrunch down, less area, faster ride)
• Cd=coefficient of friction (smoother rider and helmet, and less protrusions from the bike, the lower the Cd. This also refers to the shape of the frame, wheels, etc. A tube, spoke, fork shaped like a wing has a lower Cd than round spokes, tubes,or forks.)
• V=air speed - which is squared (ie going from V=7mph to 21mph is a 3x increase in speed which is then squared and the force required is now 9x)

SHOCKS/SUSPENSION

Shocks, both front and rear, will affect your riding over uneven terrain on a mountain bike. Front shocks decrease vibration transmitted to the shoulders and allow more concentration on the course (no energy issues here). The older rear suspended bikes without a rigid rear triangle could absorb some pedal/rear wheel energy, but this is less of an issue with the newer rear suspensions. One study did compare rigid frame (RIG), front shock (FS), and fully suspended (FSR) mountain bikes using the same riders and course. The front suspended bikes finished 80 seconds ahead of the RIG and FSR bikes over a 31 minute course!

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THE BOTTOM LINE - HOW MANY CALORIES DO YOU "BURN" WHILE CYCLING?

To calculate the Caloric requirements of cycling, you need to total the Calories needed to maintain your basic life processes (your basal metabolic rate or BMR) which are needed even if you were not exercising and the Calories used for the physical activity itself. A third component called the "thermic effect of food" refers to the energy expended in digesting, absorbing, and transporting food energy to the cells in the body. Thus your total Caloric needs can be expressed as:

CALORIC NEED = CAL(bmr) + CAL(physical efforts) + CAL(thermic effect)

As a rule, the average American, pursuing the average recreational activities and chores of daily living (mowing the lawn, etc.), uses:

1. 23% of their Calories for physical activity
2. 10% of their daily Calories for the thermic effect
3. 67% of their Calories for the BMR

THERMIC EFFECT

This is a straight 10% of all the Calories you actually eat, so you can easily calculate it. (You add up CAL(bmr) and CAL(physical effort) that need to be replaced and add another 10% to cover the energy needs of digestion and absorption.)

ENERGY REQUIREMENTS IN A COLD ENVIRONMENT

It was mentioned that a cold environment does NOT increase the BMR but requires the expenditure of additional Calories to produce heat energy and thus maintain a constant body temperature. Generally this is from muscle activity and is most noticeable with shivering to generate extra heat energy when your core temperature is falling. While riding there will be some "waste" energy (from the inefficiency of converting eaten of stored Calories into power at the pedal) but then again, the wind chill effect from riding will accentuate heat loss and tend to counterbalance this effect. How many additional Calories are neededin the cold? At rest, roughly 16 Calories per day for every degree F below 98.6. Although one can argue about exact BMR and find different formulae to calculate basal Caloric requirements, the following gives an estimate of the approximate extra energy needs (again, per day): Additional Calories/day for a cold environment = (98.6 - ambient temperature in degrees F) x 16 which would then be added to the BMR calculation and Calories used for exercise.

Does exercising in the cold markedly increase Caloric needs? Probably not by a factor that is of any significance to a cyclist, but it once again demonstrates the multitude of variables that need to be considered as one estimates the Caloric needs of exercise and cycling.

QUESTIONS

Question:I have a heart rate monitor that calculates Calorie burn based on my activity level and I was wondering if I should feed just that number or add that number to my daily requirements. - WTD

Answer: I wouldn't calculate your Caloric needs from a HR monitor. For example, does a 200 pound muscular guy with a HR of 180 burn as many Calories as an out of shape 200 pounder at the same heart rate?? Watts expended relate to work done. Heart rate doesn't. If your basal is 1700 and you really burn 1000 with exercise, you need to eat 2700 between the 3 meals and supplements during that 24 hours.

sursa: http://www.cptips.com