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Cycling: Physiology And Training

Irvin E. FariaHuman Performance Laboratory

California State University, SacramentoSacramento, CA 95819

USA

This paper examines the sport of cycling as approached

from the perspectives of history, physiology, biochemistry,

ergometry, biomechanics, aerodynamics, and training. The

physiological and anatomical determinants of cycling are

briefly explored. Aerodynamics of cycling is considered with

particular reference to the rider, equipment and bicycle.

Finally, the impact of training methods on acute and chronic

physiological responses are examined.

HISTORICAL EVENTS

The concept of the bicycle dates back to 2300 BC, when in

China, and later Egypt and India, the bicycle was envisioned.

Count Médé de Sivrac of France, in 1790, built 2 wheels linked

by a narrow wooden bride which was driven by alternate pushes

of the feet on the ground. Baron Karl Friedrich Von Drais, in

1816, added a steering device to the hobby horse-like machine.

Two years later Von Drais, riding this primitive bicycle,

established the first world cycling record. He covered the

distance between Beaune and Dijon at the speed of 9 miles per

hour.

MacMillan, an Englishman, connected 2 rods to the axle of

the rear wheel of the hobby horse-like bicycle. Through

piston movements, onto the rods, the rider using short foot

thrusts turned the bicycle wheels. A few years later

Lallement, in 1855, attached pedals to the front wheel of the

machine which became known as the "boneshaker". This was the

first attempt to apply the concept of gearing to the bicycle

by increasing the diameter of the drive wheel. This wheel

ratio concept was then applied to the "ordinary" or "penny

farthing" bicycle. The penny farthing bicycle was

characterized by a very large diameter front wheel of

approximately 60 inches.

By 1867, the bicycle was constructed of steel tubing and

wheels with iron rims causing it to weigh 110.25 pounds. The

stronger construction allow greater speeds which, in 1869,

stimulated an interest in racing. The first race took place

in France in 1869 covering a distance of 20.4 miles. The

winner, Letourd, cycled the distance in 3 hours and 9 minutes,

for an average speed of 6.46 miles per hour. In the quest

for greater speed, by 1878 the use of wooden rims, tangential

spokes, and a frame built of tubes reduced the bicycle weight

to 66 pounds.

In the late 1880s the watchmaker, Guilmét, conceived the

idea of attaching a metal chain to the bicycle's rear wheel.

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This chain resulted in the multiplication of turns on the

drive wheel, thus eliminating the need for the exaggerated

high front wheel. Four years later, in 1884, the diamond

frame was built by the Englishman Thomas Huber. The first

gear change system was employed in the 1932 world road racing

championships. Binda and Bertoni, two Italian cyclists, using

the new gearing system, won first and second place.

While the bicycle remained the primary means of rapid

transportation in third world countries, it became a toy for

children in the industrialized world. Following World War II,

use of the bicycle gave way to automobile. In general, little

attention was directed toward bicycle technology. In the

early 1950s industrialization provided large populations with

leisure time to invest in hobbies and sport interests.

Consequently, the use of bicycle regained popularity. Energy

was directed toward building a better bicycle for general

leisure time use and for racing. The goal was and remains

that of enhancing human movement efficiency.

Through improved design and the use of alloys for frame

and components cycling economy was greatly enhanced. For

example, the unaided walking person consumes about 0.75

kilocalories (kcal) per kilometer. When riding a bicycle,

however, the energy consumption for a given distance is

roughly 0.15 kcal.km-1. Each year streamlined aerodynamically adapted bicycles continue to reach higher speeds. Modern

bicycle technology proceeds contribute to the both the leisure

cyclist and racing enthusiast.

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The sport of bicycling attracts more world wide

participation, from commuter to sport tourists and serious

racer, than any other exercise modality. Ironperson triathlon

events and mountain trail cycling have more recently

contributed to the flourishing interest in bicycling.

The physiological and biomechanical aspects of bicycling

have been investigated for nearly nine decades. New materials

for the construction of lighter, more durable and streamlined

bicycles and components coupled with modern technology

portends the prospect of constructing a bicycle that affords

cyclists of a given county the "competitive edge" in

international competition. Until the past decade, little was

known or written about how the cyclist applied forces to the

pedals or drive train. Dr. Peter Cavanagh, of the

biomechanics laboratory, at Pennsylvania State University was

among the first biomechanical engineers to study such forces.

His work, along with the many other scientists who followed,

revolutionized the sport of cycling. Like Dr. Cavanagh, Dr.

Chester Kyle, one of the founders of the International Human

Powered Vehicle Association, an aerodynamics expert, pioneered

the design of aerodynamic bicycles. His untiring efforts

influenced radical change in bicycle frame and component

design as well as body apparel of the cyclist.

High-speed cameras, strain gauges, digitizing computers,

dynamometers, and wind tunnels are employed in an attempt to

catch the elusive component of successful cycling. Exercise

physiologists, biomechanists, and psychologists continue the

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search to identify the variable (s) which will, when

controlled, shave a few thousandths of a second from a rider's

time on the track and road. Most have come to recognize and

accept the fact that to optimize cycling performance the still

elusive factor and the most dependent variable lies in the

human power component. For the elite cyclist, championship

success rests on the human qualities of physiologic capacity

and mental toughness.

Metabolic Cost Of Cycling

The cyclist's energy expenditure is measured by the

oxygen consumed and expressed in liters of oxygen consumed per

minute of exercise and translated into a kilocalorie (Kcal)

cost value. Per liter of oxygen consumed the approximate

calorific transformation equals 5 kilocalories. The following

is an example calculation of cycling energy expenditure.

• Assume a 150 lb (68 kg) cyclist works at 80% of maximal

oxygen consumption of 70 ml.kg-1.min-1 (milliliters per kg body weight per minute) for four hours.

• The energy expenditure would be: 56 ml.kg-1.min-1 x 0.85 = 47.60 ml.kg-1.min-1 x 68 kg = 3236.80 ml.min-1.

• Converting to liters and Kcal then: 3.24 L.min-1 x 5

kcal = 16.2 kcal.min-1.

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• The total energy expenditure becomes: 16.2 kcal.min-1 x

240 minutes (4 hr x 60 min) = 3888.0 kcal or 972.0

kcal.h-1. (Note: 0.85 represents the thermal

equivalent of oxygen for non-protein respiratory

quotient, including percent Kcal and grams derived from

approximately 50% carbohydrate and 50% fat.)

A MET, an acronym that stands for "Metabolic Equivalent

T" which is equal to 3.5 ml.kg-1.min-1 serves as a convenient expression of energy expenditure at rest. For the above

example an equivalent MET cost is (56 ml.kg-1.min-1 ÷ 3.5 ml.kg-1.min-1) 16 METs.min-1 or 16 times rest. This energy cost is equal to running on the flat at 10.5 mph or at

approximately a six minute mile pace.

In order to cycle at speeds common to road racing, the

endurance cyclist must increase the rate of muscular energy

production by more than 20 times rest. The elite racing

cyclist is capable of using 30.7 kcal.min-1 at 25 mph at a gross energy use efficiency of approximately 19% to 29%.

Figure 1 presents the relationship between cycling speed and

Kcal cost.

Oxygen Cost and Cycling Economy

Maximal oxygen consumption (.O2max) is defined as the

highest amount of oxygen an individual can use during physical

work while breathing air at sea level. Oxygen consumed during

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cycling consists of three components: (1) that necessary to

maintain the body in position on the bicycle and for the

physiological maintenance work; (2) that required to move the

legs at zero load through the prescribed pattern of movement;

and, (3) that necessary to overcome the resistive load.

A moderately high oxygen consumption capacity is required

for successful competition at the national and international

level. Figure 2 summarizes the mean maximal oxygen

consumption values of several national cycling team members.

It can be observed that even elite cyclists vary considerably

in their maximal oxygen consumption values. Although

important, maximal oxygen consumption is not the final

variable for successful endurance performance. The submaximal

oxygen consumption per unit body weight (.O2 submax) required

to perform a given task (i. e., cycling a certain speed) is

equally crucial for success. It is considered a measure of

the cyclist's cycling economy.

Economy is defined as the submaximal oxygen use per unit

of body weight required to perform a given task. Economy

then, is the physiological criterion for "efficient"

performance. Conceptually economy of work is a very useful

measure for the evaluation of cyclist's ability to sustain a

high intensity of effort for a given time period.

Two factors influence cycling economy: (1) the cyclist's

maximal capacity to consume oxygen as reflected by the .O2max,

and (2) the maximal level for steady rate cycling as indicated

by the cycling intensity at the lactate threshold (TLA). The

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oxygen use at the TLA is expressed as percent of .O2max. The

TLA represents the point at which lactic acid is produced at a

greater rate than it can be metabolized.

The cyclist who has the highest .O2max plus the highest

LAT plus the highest cycling economy plus the greatest ability

to tolerate metabolic acidosis has the leading potential for

winning. The combination of hereditary endowment and training

emphasis determine which of these variables will prevail.

Indices Of Cycling Potential

The cyclist's ability to perform at the highest potential

appears to depend on five factors: (1) .O2 at blood lactate

threshold (L.min-1), r2 = 0.86; (2) percent of slow-twitch oxidative muscle fibers, r2 = 0.91; 2) calf circumference, r2

= 0.92; (3) mid-thigh circumference, r2 = 0.95; and (4) muscle

myoglobin concentration, r2 = 0.97. The five factors which

best predict time-trial performance include: (1) average

absolute work rate for 1 hour performance, r2 = 0.78; (2)

muscle capillary density (capillaries per mm2) r2 = 0.94; (3)

muscle PFK (Phosphofructosekinase) activity, r2 = 0.97; (4)

lean body weight, r2 = 0.98; and, (5) .O2max at lactate

threshold (1.min-1), r2 = 0.99. Elite-national class cyclists are capable of cycling at

90 ±1% .O2max for 1 hour. Factors which distinguishes the

elite class from the "good-cyclist", include the %.O2 at the

LAT and a higher absolute .O2 at LAT

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(l.min-1). The LAT may, therefore, be an effective criterion

for predicting performance. Muscle fiber type plus specific

enzyme presence contribute to the latter abilities. A high

muscle capillary density contributes to augmented lactate

removal from the muscle.

The reliability and validity of heart rate monitors has

made it possible to carefully structure a scientific training

program. Knowing the heart rate will allow the prediction,

with reasonable accuracy, of the oxygen cost of a given

cycling effort. Heart rate and oxygen consumption tend to be

linearly related throughout a large portion of the aerobic

range. Figure 3 illustrates this relationship of percent of

maximal heart rate to percent of maximal oxygen consumption.

Because this relationship is known the exercise heart rate can

be used to

estimate oxygen consumption and TLA during road cycling.

If only an estimation of the cyclist's aerobic power is

of concern a cycle ergometer may be employed. When gas

analysis is not possible the following formula is used to

estimate the oxygen consumption from cycle ergometer exercise

data.

.O2(ml.min-1)={( x )+(3.5 ml.kg-1.min-1 x kg (BW)}

Where: = the last minute of work performed on the ergometer.

POWER OUTPUT

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The term force effectiveness is often used in cycling to

quantify the relationship between the force "applied" (Fr) by

the rider and the force "used" (Fe) in propulsion (force

applied perpendicular to the crank). Force effectiveness is

expressed by: Force effectiveness = Fe ÷ Fr

Direct measurement of these quantities using a force

measuring pedal has shown that the index of effectiveness

during the propulsive phase of cycling in elite riders is only

76%. This fact suggests that 24% of the applied force, during

cycling, is used to deform the cranks and other parts of the

bicycle. Thus, the conventional method of applying force to

common bicycle transmission is an inefficient process.

However, increased force effectiveness has not been found to

account for higher power output . Rather high power output is

attributed to higher peak vertical forces and torque during

the cycling downstroke. The standard cycling position,

compared to prone and supine, is clearly superior for power

development. Elite compared to "good-class" cyclist have been

shown to generate more power by producing higher peak vertical

forces and crank torque during the down-stroke. This greater

magnitude of vertical force results in more work per

revolution. In terms of equal RPM, this means a larger power

output. Therefore, it might be concluded that effective

vertical force is essential for superior performance. The

latter, however, is not necessarily the case. It has been

observed that the larger the proportion of the resultant force

applied to the pedal does not necessarily create propulsive

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torque. Clearly then a measure of cycling effectiveness

cannot be based solely on the orientation of applied pedal

forces.

Cyclists may reduce the negative torque during the

upstroke by pulling up on the pedal. However, at high power

outputs, increased peak torque during the downstroke is more

responsible for increased power output than is reduced

negative torque during the upstroke.

Pursuit cyclists have registered power outputs ranging

from 331 to 449 watts with cadences between 103 and 126 rev

min-1. Competitive cyclists can maintain a power output of

more than 300 watts for one hour (0.4 horsepower). Eddy

Merckx, one of the world's greatest cyclists, has registered

the highest power output of 440 watts (0.6 horsepower) for

one hour.

Muscle Fiber Recruitment

Successful cycling performance may be a matter of cycling

technique including ineffective use of muscle fiber

recruitment. Fiber recruitment is influenced by contractual

needs and fiber type availability. Genetic as well as

training influence muscle fiber type.

Human skeletal muscles differ widely in their speed of

contraction, fatigue threshold, and response to different

rates of stimulation. Three distinct fiber types have been

identified. Slow-twitch oxidative (SO) fibers (Type I)

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possess a greater quantity of mitochondria and contain

correspondingly greater amounts of Krebs Cycle and electron

transport system enzymes than other identified fibers. When

oxygen is provided, these fibers have a great potential to

produce adenosine triphosphate (ATP). Slow-twitch oxidative

fibers have a greater ability for fatty acid and ketone body

utilization than do less oxidative fibers. In contrast, fast-

twitch glycolytic (FG) fibers (Type IIa), possess high

myofibrillar ATPase and have a lesser oxidative potential but

exhibit greater anaerobic capacity to produce ATP than the SO

fibers. The FG fibers rely heavily on carbohydrates in the

form of glycogen as a substrate. Fast-twitch oxidative-

glycolytic (FOG) fibers (Type IIb) are considered to be

intermediate in character because their fast contraction

ability is combined with a moderately well developed potential

for both aerobic and anaerobic energy transfer.

Trained cyclists display a wide range of muscle fiber

types which compose their knee extensor muscles. Type SO

fibers have been shown to occupy 32 to 76 percent of road

racing cyclist's knee extensor muscles. The vastus lateralis,

one of the knee extensors, of the majority of racing cyclist

is high in SO fibers. Type FG fibers comprise the next largest

portion of the remaining fibers while FOG fibers are fewest in

number.

Increased years training and racing possibly has an

influence on the percentage of SO fibers in the vastus

lateralis and other major cycling muscles. Long term chronic

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overloading of these muscles possibly enhances the presence of

SO fibers. Endurance athletes possess a higher percentage of

SO fibers in their trained muscles yet a normal percentage of

SO fibers in their untrained muscles. Figure 4 presents a

comparison of muscle fiber type between competitive, elite,

and untrained cyclists. Leg muscles of world-class sprint

cyclists, however, may show a predominance of FOG and FG

fibers. While a high percentage of one fiber type may suggest

potential for a specific mode of cycling, fiber type dominance

has not been shown to a determinant of success.

Pedaling Efficiency

Optimal pedal rates selected by different cyclists are

often a factor of cycling experience and skill level. Racing

cyclists tend to acquire the skill to ride at a cadence above

90 rev.min-1, whereas, recreational or novice cyclists tend to prefer lower pedal rates. The highly skilled cyclists

working at a constant power output (75% .O2max) at varying

pedal rates of approximately 70, 95 and 126 rev.min-1 are most economical with a preferred range of 80 to 120 rev min-1. At

80% of .O2max the most economical pedaling rate has been shown

to be slightly below 90 rpm. It has been suggest that

pedaling at 90-100 rpm may minimize peripheral forces and

therefore peripheral muscle fatigue even though such a rate

may result in a higher oxygen uptake.

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Among the variables that affect pedaling efficiency,

pedaling rate is the most sensitive, followed by the crank arm

length, seat tube angle, seat height and longitudinal foot

position on the pedal. Seat tube angle decreases as the

cyclist size increases. A decreased tube angle shifts the hip

axis backward relative to the crank axis. Consequently, the

taller cyclist, with larger leg segments, will benefit from

shifting to a more rearward position. Conversely, the

shorter cyclist whose leg segments are smaller will benefit

from shifting to a forward position. Longitudinal foot

position increases with the cyclists size. Taller cyclists

will benefit from placing their foot further back on the

pedal. The seat angle should be adjusted to the cyclist to

realize minimum joint moments.

At a 120 rpm the duration of a crank cycle is 500

milliseconds (ms); half of the crank cycle lasts 250 ms.

Coincidentally the duration of twitch response of the

quadriceps muscle is about 250 ms. The relaxation time of

the quadriceps muscle after electrical stimulation is 103 ms.

When pedaling at 120 rpm the relaxation time represents a

crank rotation of 72 degrees. The inability of the muscle to

contract and relax more rapidly could explain why the force

continues further into the crank cycle than is desirable.

The forces applied to the pedals become less optimally

directed as the pedaling rate is increased. The average for

the effectiveness index, the ratio of the force applied

perpendicular to the crank arm to the force applied to the

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pedals, decreases from 0.5 to 0.35 as the pedaling rate is

changed from 40 to 90 rpm at a power output producing 60% of

.O2max. The relationship that exists between the velocity

(speed) of muscle shortening and the tension it is able to

generate is an important constraint, or limiting factor in the

performance of rapid pedaling rates. Racing cyclists

typically spin at about 90 rev min-1 in cruising situations.

The tension a muscle is able to exert decreases as the speed

of muscle shortening increases. According to the force-

velocity relationship, the force that a muscle can exert is

inversely related to the speed of shortening. Thus, the

possible limitation set by the force-velocity relationship is

noteworthy when trying to apply large forces to rapidly

turning bicycle pedals.

Speed of limb movement has a marked effect on the gross

efficiency of work output. Efficiencies of 19.6% to 28.8%

have been reported in the literature. At high power output a

decrease in efficiency is not evident when pedal rate is

increased while holding power output constant. There appears

to be a significant advantage in employing a high pedaling

rate at high power output. Even at a pedal rate of 130 rev

min-1 a 22% gross efficiency has been observed.

Peak muscular efficiency generally occurs at a velocity

of approximately one-third of the maximal shortening velocity

in both SO fibers and FG fibers. SO fibers have been shown

to work most efficiently at a shortening velocity of about one

fiber length per second. A knee extension at 200° per second

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requires the vastus lateralis muscle to shorten at about 90 mm

per second. The average muscle fiber length in the vastus

lateralis is about 72 mm, therefore a fiber shortening at 90

mm per second would be equal to approximately 1.2 fiber

lengths per second.

When pedaling at 80 rpm the knee extension velocity is

approximately 200° per second which is the velocity of peak

efficiency in SO fibers. Therefore, the 80 rpm pedaling speed

is close to the estimated peak efficiency in SO fibers. FG

fibers of endurance athletes are at their velocity of peak

efficiency when contracting at approximately 3 fiber lengths

per second. It has been predicted that efficiency is

approximately two-fold higher in SO compared with FG fibers

when cycling at 80 rpm. This thesis is supported by the

observation that SO muscle fibers are 2-3 times more efficient

than FG fibers. It should be made clear, however, that during

pedaling at high rpms almost all fibers, regardless of type

are recruited and share in the force generating effort. The

percent of SO fibers involved appears to relate positively to

a desired pedaling of 80 rpm.

Shoe and Pedal Merits

Cycling shoe design reflects the nature of forces applied

by the cyclists to the pedal-crank system of the bicycle.

Efficient pedaling action is a circular motion with a

repeating pattern of force application. The magnitude of the

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force and the angle at which the force is applied vary

continuously throughout the pedal-crank rotation.

Crank rotation is dependent upon forces applied

perpendicular to the crank. At the bottom of the stroke the

total force is quite large, however, it is applied almost

parallel to the crank arm representing wasted force. At 90

degrees after top dead center (TDC) the force is applied

approximately perpendicular to the crank. At this point the

effective component is much larger. When the force is not

perpendicular to the crank, it is wasted. Pedal-crank

motion throughout the second 180 degrees of rotation often

results in force applied opposite to the desired direction.

During this "recovery phase" the goal is to introduce as much

positive effective force as possible. That is, to retain the

propulsive phase as long as possible. To do so, requires that

shoe and pedal design as well as cycling technique be given

special attention. Not only must the shoe ensure comfort and

safety but its interface between the cyclist's foot and

bicycle pedal provide effective transmission of force.

Negative peak torque represents lifting the foot during

the recovery phase by the opposite pedal. Experienced

cyclists do not significantly pull up on the pedal during the

upstroke. Rather, the larger peak torque observed during high

power output is attributable to recruitment of a larger

quantity of leg muscle per crank revolution.

While pushing down onto the pedal the major pressures

occur in the forefoot. The primary load bearing areas are

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first metatarsal head region and the hallux. During steady

speed cycling, the most important interaction of the pedal

with the foot occur at the first metatarsal head, the lesser

metatarsal heads and the hallux.

Positive peak torque occurs within the range of 90° to

110° of the power phase of pedaling. A posterior foot

position instead of an anterior position decreases the

dorsiflexing ankle load moment and increases the gluteus

medius and rectus femoris activity. At the same time, there

is a decrease in soleus muscle activity but the hip and knee

moments are not changed.

CRANK LENGTH

Crank lengths between 165-180- mm at 2.5 mm increments

result in different energy costs. Cost function increases

with body size because a taller cyclist requires greater

kinematic joint moments than others to move the crank due to

the increased mass. Also, the moments of inertia of the

larger lower limb segments increase the cost. Optimal crank

arm lengths are seen to increase with increased body size. A

taller rider requires a longer crank arm than a shorter or

average cyclist. As the crank arm length increases, cadence

decreases as the rider's size increases. The longer crank

length requires low pedal forces resulting in a decrease in

static moments. Yet, a longer crank arm demands more motion

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from leg segments. Thus, crank arm length and pedaling rate

effects are opposite.

Muscle Recruitment

Electromyographic (EMG) studies have been used to

identify the specific muscle involvement during the power and

recovery phase of pedaling. For a review of muscle

involvement see Faria and Cavanagh, 1978. The muscles which

are employed in cycling include the rectus femoris, vastus

lateralis and medialis, semimembranosus, biceps femoris,

tibialis anterior, gluteus maximus and gastrocnemius. The

illiopsoas like the rectus femoris, is partly responsible for

the motion of the leg during the recovery phase of the pedal

path. The vastus medialis and lateralis of the quadriceps

group extend the knee. The rectus femoris , part of the

quadriceps group, crosses both the hip and knee joints. Thus,

it both flexes the hip and extends the knee. The biceps

femoris long head, part of the hamstring group, crosses the

two joints, and by doing so serves to extend the hip and flex

the knee. The semimembranosus also crosses two joints, the

hip and knee, thereby it functions to both extend the hip and

flex the knee.

Lying in front of the knee joint is a small, flat and

triangular shape bone, the patella or knee cap which slides

along in a groove at the end of the femur. The efficiency of

the knee extensors is radically improved by the presence of

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the patella. These muscles, the one-joint vasti group and the

two-joint rectus femoris, together make up the quadriceps;

all of these muscles terminate in the same tendon, which may

be felt just above the knee cap when tensing the quadriceps.

The patella increases the turning effect of the quadriceps by

moving the line of action of their force further from the

center of rotation of the joint.

Muscle activity is seen to increase with increased pedal

speed. However, there is a lack of increase in the gastroc

activity at higher pedal loads. The lack of a marked decrease

throughout the maximum activity regions in quadriceps is seen

at lower pedal loads. It is clear that the onset of muscle

activity for all muscles in the quadriceps group occurs well

before 0° or TDC. The rectus femoris begins its activity

close to the middle of the recovery phase (200° to TDC) only

to terminate contraction at about 120-130°. Its greatest

activity is observed from just prior to TDC, which is greater

than 50% maximum, for a brief period between 30° before TDC to

30 after. The onset of activity of the vasti appears later

than that of the rectus femoris. Both vasti muscles exhibit

greatest activity between 340° and 100°. At about 40-50°

later than the rectus femoris the vasti muscles turn on.

Quadriceps group activity terminates at about the same angle.

The biceps femoris region of greatest activity is between 80°

and bottom dead center (BDC). While the greatest activity for

the other hamstring occurs in the region from 60° to 240°.

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The gluteus maximus is active from TDC to about 130°.

This activity is within the region of the power stroke (25-

160°). It greatest activity (>50%) has been observed between

10° and 110°. This represents the power stroke when the hip

is being extended. Just after TDC the biceps femoris and

semimembranosus exhibit the largest region of activity to the

middle of the recovery phase. In the lower leg, the tibialis

anterior muscle is active in the second half of the recovery

phase from about 280° to just past TDC. At about 30° the

gastrocnemius begins to contract and terminates at about 270°.

Activity of the gastrocnemius begins a few degrees after

termination of the tibialis anterior. Gastrocnemius activity

terminates a few degrees prior to the onset of the tibialis

anterior. It is interesting to observe that the gastrocnemius,

a knee flexor, active when the quadriceps are extending the

knee (45° to 110°) quadriceps and hamstrings. Consequently,

there is little co-contraction of agonist/antagonist muscles.

From TDC to 90° the active muscles include the gluteus

maximus, the muscles of the quadriceps group, and

gastrocnemius. From 90° to 270° the active muscles are

limited to the gastrocnemius and the hamstrings. Active

muscles from 270° to TDC include the tibialis anterior and

rectus femoris.

During pedaling, the hip and knee are very different in

their actions. Hip movement is extensor. Knee movement is

first extensor and then flexor. There appears to be dominance

of knee extensors over hip extensors in the first quadrant of

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the pedal revolution. In the second quadrant of pedal

revolution substantial reduction of knee extensor activity is

observed. Muscle activity during pedaling is characterized

by little co-contraction of agonist/antagonist muscles. This

is especially true for the gastrocnemius/tibialis anterior and

at the ankle and hamstrings/quadriceps at the knee. If the

knee extensor muscles were to develop moments in excess of the

flexor moment generated at the knee by the two joint extensors

it would created an extremely uneconomical metabolic event.

Saddle Height

The saddle height should be 97% to 100% of trochanteric

leg length and 109% of the symphysis pubis height. Trochanter

length is the distance measured from the greater trochanter to

the floor with the subject standing straight-legged on bare

feet. Seat height is the distance from the top of the seat to

the top surface of the pedal platform, measured along the seat

tube with the crank arm in the down position but parallel to

the seat tube. These heights result in the most efficient use

of available energy. A lower seat results in greater

quadriceps force and thus higher muscle activity.

Aerodynamics Of Cycling

Air resistance is the major retarding force affecting

cycling. Wind forces of just 10 miles per hour begin to

significantly load the racing cyclist. A cyclist traveling at

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20 mph typically displaces approximately 1,000 pounds of air

per minute. At that speed about 70 percent of the power

consumption is due to the air's resistance to the rider and 30

percent to the air's resistance to the bicycle. However, if

the cyclist bends the elbows and crouches with the torso

nearly parallel to the ground, the wind resistance is lowered

by approximately 20 percent. When a rider assumes a position

of hands on center of upper handlebars, chin resting on the

hands, and the crank parallel to ground, the wind resistance

is lowered by about 28 percent.

A bicycle moving through still air leaves a trial of

moving air, and loses the energy taken to set this air in

motion. Drag is the force that transfers this energy from the

bicycle to the air. Drag is very costly, for example, at 10

mph, 50 percent of a cyclist's energy goes into cutting

through the air; at 30 mph, 90 percent of energy is spent over

coming drag.

The rough-edged shape of the human body is an ideal model for

generating drag. The cyclist and bicycle are affected by two

forms of aerodynamic drag: First, when the flow of air fails

to follow the contours of the moving body, pressure drag is

created. When air is separated of from the body the

distribution of air pressure is changed. This separation

occurs toward the rear of the body. The air pressure at that

location becomes lower than it is on the forward surface,

resulting in drag. Second, skin-friction drag results from

the viscosity of the air. Friction is caused by the layer of

23

air immediately next to the body. Projecting objects from the

bicycle frame or cyclist, cause airflow to separate from the

surfaces. Newly created low-pressure regions form behind the

projections result in pressure drag. However, air flows

smoothly around a streamlined shape closing in behind as the

body passes.

Head winds, tail winds, and crosswinds significantly

influence both aerodynamic drag and the power requirements.

For example, a cyclist traveling at 18 mph in still air must

increase the power output by 100 percent to maintain that

speed against a head wind of 10 mph. This change in power

output is best accomplished through changing gears. A tail

wind makes the bicycle go faster. A pure tail wind or head

wind will speed up or slow down the rider slightly more than

half the wind speeds. A rider going 20 mph with a 10 mph tail

wind is capable of traveling about 26 mph. A 10 mph head wind

will slow the same rider to about 14 mph. Overall, wind will

speed up or slow down a bicycle by about half the wind speed.

Though when drafting in the wake of another rider the power

requirements of the drafting rider are reduced by about 30

percent, tandem riders use 20 percent less power per rider

than two separate cyclists.

Aerodynamic drag increases as the square of the

velocity. Power is proportional to the product of the drag

force and velocity, so that the power needed to drive an

object through the air increases as the cube of the velocity.

Therefore, a small increase in speed requires an enormous

24

increase in power. The rider who suddenly doubles power

output, while traveling at 20 mph, will increase speed to only

26 mph. The point is that high speeds require extremely high

aerodynamic efficiency.

Four methods are effective in decreasing the wind

resistance of bicycling: 1) Reduce the frontal area of the

rider and bicycle; 2) Improve airflow around the shoe by

eliminating straps and toe clips. A drag decrease of about

0.08 pounds at 30 mph results from a cleaner shoe profile.

Spandex shoe cover reduces drag by 0.12 pound. With

particular streamlined shoes, drag may be reduced from 0.25 to

0.40 pounds. 3) Reduce air turbulence of the bicycle parts.

Aero tubing reacts better in cross wind than standard tubing.

Smaller wheels, fewer spokes, narrower tires, narrow hubs,

aero rims, covered wheels and aero spokes all lower drag; and,

4) Streamline the accessories. Even an inefficiently

streamlined water bottle adds almost 0.2 pounds of drag at 30

mph to the bicycle system. Sheathed cable adds about 0.03

pound per foot of drag if it is crossed to the wind. Bare

wire adds much less. A faired wheel has a much lower drag,

about one-quarter that of the plain wheel. Clothing can

significantly affect drag. A one-piece, full-length suit of

Lycra Spandex material with an aero hood will reduce overall

wind drag by about 11 percent. A streamlined helmet reduces

drag by 7%. From a practical view point, a 0.02 pound

decrease will lower the time for a 4000-meter pursuit by about

0.3 seconds. The maximum drag decrease possible, using

25

traditional equipment as standard, is about 1 pound at 30 mph.

A 1 pound decrease will result in 13 seconds faster for 4000

meters.

When riding in groups, cyclists behind consume less

energy by being partially shielded from the wind. Therefore,

the use of pace lines becomes an important race tactic. Even

touring cyclists of equal ability riding in a group can travel

from 1 mph to 3 mph faster than any lone rider. Cyclists

traveling in the wake or "slipstream" of those in front may

lower their wind resistance significantly. This is

accomplished by taking advantage of an artificial tail wind.

That is, the air is already moving forward when they reach it.

For example, two cyclists in a pace line at 24 mph, the front

cyclist consumes the same energy as if riding alone. However,

the cyclist following requires about 33% less power output.

At this speed, reduction in wind resistance is about 38%.

However, since rolling resistance is unaffected by

slipstreaming, the decrease in external power required is

smaller (33%).

The closer one cyclist follows another, the greater the

drag reduction. The total wind resistance decline averages

44% for 1.7 m between riders or a zero wheel gap, and only

about 27% average for 3.7 m between riders on a 2 m wheel gap.

Implications For Training

Lactate Threshold Training

26

The production of force by muscles used for cycling is

dependent upon a steady supply of energy. The form of energy

used for all the muscles' operations is the compound produced

inside the fibers, adenosine triphosphate (ATP). Possible

sources of ATP include the ATP stored in the muscles, that

produced from the aerobic breakdown of carbohydrates and fats,

and ATP produced anaerobically from muscle glycogen. Because

the quantity of ATP stored in the muscle is limited, enough

for three to five seconds of maximum effort, it must be

continuously manufactured.

Carbohydrates, fats, and protein, when broken down,

provide the energy bound into the ATP molecule. Within the

muscle cells special structures called mitochondria use

foodstuffs and oxygen (aerobic production) to produce large

amounts of ATP. The muscle can also produce ATP without

oxygen (anaerobic production), however, this method is

inefficient and limited for exercise of 20 to 60 seconds.

In order to speed the rate of energy production,

aerobically and anaerobically, the muscle cell employs

specialized proteins called enzymes. High intensity cycling

raises the muscle's lactic-acid level. Lactic acid is a

strong acid that ionizes and releases hydrogen ions. These

hydrogen ions can exert a powerful effect on other molecules

due to their small size and positive charge. Hydrogen ions

attach to molecules thereby altering the molecule's original

size and shape. The altered size and shape disrupts the

normal function of the molecule (enzyme) and therefore

27

negatively influences normal metabolism of the cell.

Increased intramuscular hydrogen ion concentration can impair

exercise performance by reducing the muscle cell's ability to

produce ATP by inhibiting key enzymes involved in both

anaerobic and aerobic production of ATP. The hydrogen ions

released by lactic acid block the breakdown of glucose. Also,

hydrogen ions compete with calcium ions for binding sites on

the muscle's contracting units, thereby hindering the

contractile process.

High lactic-acid levels, however, can be a good sign

because it indicates the capability of producing a lot of

energy "anaerobically" and the potential for high speed

cycling is excellent. If not controlled, however, the

increased muscle cell acidity has the potential to eventually

reduce muscle contraction resulting in fatigue. The muscle

and blood acidity level is expressed numerically in units of

"pH" which represents the concentration of hydrogen ion. The

pH of body fluids must be regulated (i.e., normal arterial

blood pH = 7.40± .02) in order to maintain homeostasis. Heavy

exercise can present a serious challenge to hydrogen ion

control systems due to lactic acid production. During high

intensity exercise acids accumulate inside the muscles which

can drop the pH to 6.9, then to 6.8 or even 6.6 during which

the muscle is unable to produce energy or contract

effectively. These acid-induced slow downs are avoidable if

the buffering capacity of the muscle is sufficiently high. A

buffer resists pH change by removing hydrogen ions when the

28

hydrogen ion concentration increases, and releasing hydrogen

ions when hydrogen ion concentration falls. The ability of

buffers to resist pH change rests on the individual buffers

ability to act as a buffer and the concentration of the buffer

present. The greater the concentration of a particular

buffer, the more effective the buffer may be in preventing pH

change. As the body's buffering capacity is improved the

ability to sustain a punishing sprint pace the last 400 to 800

meters to the finish will be enriched.

The training necessary to improve buffering is called

lactic-acid (LAT) training and is unique and different from

that used to enhance the lactate-threshold. The purpose of LAT

is to promote a "tolerance" for lactic acid or the ability to

continue to cycle fast even though the muscle cells increase

their production of acid. The goal is to gain the ability to

produce some lactic acid without suffering from large drops in

muscle pH. This tolerance enhances the ability to suddenly

sprint for a "breakaway" without suffering the consequences

sudden fatigue.

The principle of LAT training is to cycle for a short

period of time, raising the muscle-lactate level and lowering

muscle pH. The muscles are then allowed to recover for a

brief period of time followed by a repeat of high intensity

cycling. This sequence is repeated several times during a

training session. LAT results in enhanced buffering capacity

through the increase in the muscle cells creatine phosphate, a

high-energy compound which is also a buffer, and the

29

augmentation of special buffering proteins inside the muscles.

The muscles' ability to produce bicarbonate, an effective

buffer, is enhanced as is the muscle cells' ability to diffuse

lactate acid into the blood. LAT training will also result

in an increase in concentrations of phosphofructokinase, a key

muscle enzyme involved in anaerobic energy production.

Three LAT protocols appear to be effective: 1) 60-second

work intervals at close to top speed, with 2.5 minutes of

recovery between intervals; 2) 90-second work intervals at

close to maximal intensity, with 4 minutes of recovery; 3)

120-second near-top-speed intervals, with 5 minutes of

recovery between each. It is important not to extend the work

interval beyond two minutes. A longer work interval lowers

the intensity leading to a lower lactic-acid production, small

reduction in muscle pH, and an attenuated stimulus to enhance

buffering capability. Equally important is the recovery

interval. In general, the recovery interval should be about

two to three times as long as the work periods in order to

allow enough recovery so that work intervals remain at a very

high intensity. Four to 12 minutes of near-maximal cycling

per LAT training session is recommended. This time includes

only the work interval and not the recovery period. A

training session, for variety, may include a mix of 60-, 90-,

and 120-second LAT intervals.

Since LAT is so intense no more than one LAT session per

week is recommended and only after a solid mileage base has

been established. LAT should not be included during tapering

30

periods. Moderate quantities of LAT will help road cyclists

cope with race surges in intensity, accelerations during

longer racers, and sprints to the finish.

LAT training is ideal for the track racer, however, for

endurance cyclists, especially whose muscles are mainly

composed of slow-twitch muscle fibers, LAT should be limited.

There is a limited amount of energy and fuel available for

muscle use which may be channeled into improving buffering

capacity and anaerobic power. The resources for maximally

enhancing aerobic power, aerobic structure and enzymes could

then be reduced. Therefore, too much LAT performed by the

endurance athlete might reduce cycling economy.

Hill training sessions enhance both economy and .O2max.

The type of hill training which increases economy is quite

different from the inclined workouts which bolster the aerobic

qualities of the quadriceps. Both long, gently sloping hills

at 8 to 10 percent grade, and those of 20% or more incline

should be included in training. The hills may vary in length

from 200 meters to several miles. The ideal site is a six- or

seven-mile course with nonstop undulations of the flat-ground

portion no more than 25-30 percent of the total cycling.

A method of establishing intensity during the hill

sessions is to train at a pace that feels about as hard as

when cycling at anaerobic threshold speed, even though the

actual pace will be slower. Alternatively, the heart rate,

which should be about 85-87 percent of maximum during the last

two-thirds of the session (85% of maximum corresponds with 76-

31

percent .O2max intensity). The first few climbs should not be

excessively fast, rather intense to the level that each

successive climb may be equally intense. The goal is to train

at steady-state intensity. Six weeks of hill training can

increase the concentrations of enzymes in the quad muscles by

approximately 10 percent. An alternative to this steady-

intensity hill training is to alternate two minutes of hard

cycling at a pace that feels like a race pace or faster with

two minutes of easy cycling, and continue this pattern for

five to six miles. Over a period of several weeks, gradually

reduce the length of each easy-cycling period to only one

minute.

To enhance economy choose a fairly steep, 300- to 800-

meter hill, and surge up the incline at close to full speed on

every other repetition. Coast down the hill after each ascent

and then circle until rested enough to charge up the slope

again. A minimum of three of these type of training sessions

per month is suggested.

Recent evidence from the Netherlands suggests that two

weeks of super high-intensity training can be very rewarding.

The protocol is to, during two weeks, increase the total

training time 5 hours per week and the quantity of high-speed

interval training 7 hours per week. The overall intensity

training should represent 63% of the total workout time. The

intense intervals should be carried out at 90-100 percent

.O2max (93-100 percent of maximal heart rate), with one-to

three-minute work and rest intervals and five to 30 work

32

intervals per training session. Following the two weeks of

super intense training expect to experience negative feelings

of tiredness. However, two weeks after the over training

sessions have ended new performance peaks may be expected.

Expected modifications include increase in maximal power, less

lactic acid during top-speed cycling, and about a 4 percent

improvement in performance.

Aerobic Training

Aerobic conditioning should represent the bulk of the

road cyclists' training. The concept employed is sizable

volumes of continuous, long-distance cycling at below race

pace. The pace should allow conversation while cycling.

Training sessions may last 2 hours or more.

Aerobic conditioning is typically performed at 60% to 75%

of maximal oxygen uptake (.O2max) pace. This pace is equal to

a training heart rate of approximately 70% to 80% of heart

rate reserve, i.e., [(Max HR - Rest HR) x (.75) + (Rest

HR)]. Cycling slower than 60% of .O2max pace results in little

measurable aerobic improvement. Cycling faster than 75%

.O2max pace may causes excessive glycolytic (anaerobic)

activity.

The focus of aerobic training is the engagement, as much

as possible, of fatty acid metabolism. Short rides of 10 to

20 miles and longer rides from 30 to 60 miles are recommended.

The goal of this training is to improve oxidative capabilities

in cardiac and skeletal muscle cells.

33

The purpose of this training is to increase the quantity

of stored fuels (carbohydrates and fatty acids) as well as the

number and size of mitochondria in the stimulated muscle

cells. Through increasing blood volume and capillary density

in trained muscles improved oxygen delivery and carbon dioxide

removal results.

This form of aerobic training will stimulate primarily

the slow- twitch skeletal muscle motor units. In response to

training, during a ride fewer motor units are required to

maintain a given pace while those activated do not need to

work as hard as before for the same given maximum work output.

Their training response is reflected in their ability to work

at a given submaximal intensity with less fatigue. The result

is improved cycling economy because less muscle activity is

required and thus less oxygen consumption is required in

producing movement.

The benefits of aerobic training include: 1) An increase

in oxidative and glycolytic enzymes in working muscles; 2)

Activation of additional slow twitch muscle fibers that were

not stimulated by less intense training; and, 3) A small

increase in blood buffering capacity.

Anaerobic Threshold Training

Anaerobic threshold training is aimed at raising the

anaerobic threshold. In addition, it serves to train those

muscles involved in high pedal rates. Effective

34

aerobic/anaerobic conditioning requires a pace range from just

slower than road race pace to a pace just beyond

lactate/ventilatory threshold (Tvent). To be effective this

pace or work intensity is beyond that which blood lactic acid

begins to accumulate at an increasing rate. Training at a

pace slightly faster than the Tvent level optimally stimulates

those physiological mechanisms responsible for the anaerobic

threshold enhancement. The reward is ability to sustain a

faster pace for a longer period of time.

Exercise physiology laboratories are equipped necessary

to measure an individual's anaerobic threshold (AT). Once the

AT is determined the oxygen uptake value at the AT is divided

by the maximal oxygen uptake in order to determine the percent

relationship. For the trained endurance cyclist, the AT .O2

should be at least 80% the .O2max.

The heart rate at the AT may be used as a guide for

training intensity. An effective training protocol is to

cycle at the AT HR for anywhere from 15 to 30 minutes. The

training heart rate should represent between 80-90% of the

.O2max. An example training session would be a 20 minute ride

at the AT HR followed by a mile recovery and a 15-min ride at

the AT HR. This faster paced training should be sustained for

a period long enough to initiate physiological adaptation, yet

not so long that needless training discomfort occurs. Cycling

intervals of 4 to 10 minutes are also very beneficial. The

key to success in aerobic/anaerobic interval training is to

manipulate the rest intervals so that repeated work intervals

35

are performed at racing speed with rests of only 30 to 45

seconds. Limit this type of training to 2 or 3 times per

week.

It is difficult and impractical to measure oxygen uptake

during training, however, it is important to know at what

percentage of maximum oxygen uptake training intensity

represents. Intensity monitoring can be accomplished with the

use of a heart rate monitor or simply counting the pulse while

cycling. An effective method used to establish the training

intensity is the application of the relation between percent

.O2max and percent max heart rate. Figure 3 shows that in

order to train at 85% .O2max the corresponding intensity is 90%

heart rate max. For example, if an individual with a maximum

heart rate of 195 beats.min-1 wished to train at 85% of .O2max the training heart rate would equal approximately 176

beats.min-1.Tapering for Competition

Most athletes know that the optimal way to taper for

competition is to reduce dramatically the intensity and

duration of training sessions and consume plenty of

carbohydrates and liquid. Proper tapering periods relieve

fatigue and enhance certain performance-related variables,

such as lactate-threshold and cycling speed. An investigation

of several tapering protocols reveals that a six-day tapering

procedure produces impressive results. The six-day tapering

protocol is the following: Day 1- 40 minutes of exercise;

36

Day 2 - complete rest; Day 3 - 40 minutes of exercise; Day 4

- 20 minutes of exercise; Day 5 - 20 minutes of exercise; Day

5 - 20 minutes of exercise; Day 6 - complete rest. The

intensity of training during the taper should be maintained at

the same exertion level utilized during the regular training.

Thus, only the volume of training is reduced between 60-70

percent during tapering.

Through following this tapering protocol several

advantages can be realized. Lactate threshold may be higher

than it has been prior to the taper, muscle-enzymes

concentrations remain high, muscle glycogen stores are

significantly enhanced. The implications for the six-day

taper are clear: First, it is an effective way to improve

lactate threshold. Second, tapering periods may be

effectively used during regular training. For example, a one-

week tapering period might follow each six-week training

period in order to realize the benefits of the taper.

Finally, prior to race day not only is a sense of physical

recovery evident but lactate threshold is higher, muscle

glycogen is higher, and muscle enzyme levels remain high all

of which will enhance overall performance capacity.

References

1. Burke, E. R., I.E. Faria, and J.A. White, Cycling. In:

Physiology of Sports (Ed.) Reilly, T., Secher, N., Snell, P.

and Williams, C. New York: E. & F. N. Spon, 1990.

37

2. Coyle, E. F., M. E. Feltner, S. A. Kautz,, M. T. Hamilton,,

S. J. Montain,, A. M. Baylor,, L. D. Abraham,, and G. W.

Petrek, Physiological and biomechanical factors associated

with elite endurance cycling performance. Med. Sci. Sports

Exerc., 23:93-107, 1991.

3. Davis, R., M. and Hull. Measurement of pedal loading in

bicycling: II. Analysis and Results. J. Biomechanics

14:857-872, 1981.

4. Faria, I.E. Applied Physiology of Cycling. Sports Med.

1:187-204, 1984.

5. Faria, I.E. Energy Expenditure, Aerodynamics and Medical

Problems in Cycling - An Update. Sports Med. 14:43-63,

1992.

6. Faria, I.E., and P. R. Cavanagh, The Physiology and

Biomechanics of Cycling. New York: John Wiley and Sons,

1978.

7. Garnevale, T. G. and G. A. Gaesser, Effects of pedaling

speed on the power-duration relationship for high-intensity

exercise. Med. Sci. Sports Exerc., 23:242-246, 1991.

8. Kyle, C. R. The Mechanics and Aerodynamics of Cycling, In:

Burke, E. R. (Ed), Medical and Scientific Aspects of

Cycling, Champaign, IL: Human Kinetics Books, 1988, pp. 235-

251.

9. Lafortune, M. and P. Cavanagh, Effectiveness and efficiency

during bicycle riding. In: Matsui, H. and Kobayashi, K.,

(Eds), Biomechanics VIIIB, 928-936,Champaign, IL: Human

Kinetics, 1983.

38

10. Patterson, R. P. and M. I. Moreno, Bicycle pedaling

forces as a function of pedaling rate and power output.

Med. Sci. Sports Exerc. 22:512-516, 1990.

11. Whitt, F. R. and Wilson, D. G. Bicycling Science.

Cambridge, MA.: MIT Press, 1982.

39

FIGURE LEGENDS

Figure 1 - The relationship between cycling speed and

kilocalorie cost per minute.

Figure 2 - Summary of the mean maximal oxygen consumption

values (ml.kg-1.min-1) of several national and international

cycling team members.

Figure 3 - The relationship between the percent of maximal

heart rate (beats per minute) and percent of maximal oxygen

consumption. Five example points are plotted.

Figure 4 - The variability of percent of slow-twitch oxidative

(SO), fast-twitch glycolytic (FG) and fast-twitch oxidative

glycolytic (FOG) thigh muscle fiber types found for

competitive and elite road cyclists and untrained riders.

40