PHYSIOLOGY AND TRAINING FOR CYCLING TIME TRIALS

• Time Trials - The energy system.
• How does the human body cope?
  (the three energy systems).
• Measurement of aerobic and anaerobic power.
• How do I train effectively?
  • Types of training
  • Long continuous rides
  • Interval training
• Muscle and cardiovascular development.
• Warm up and warm down.

Time Trials - The energy system.

The anaerobic aspect is most important for events where very intensive effort is required for periods of 10 seconds up to 2 or 3 minutes, such as sprinting, short track events or bridging a small gap

A well trained aerobic base is crucial for time triallists, but it is also essential for creating a good anaerobic one. The largest proportion of even a sprinter's training is aerobic.

How does the human body cope?

The three systems are:

• ·         ATP/CP system - anaerobic.
• ·         Lactic acid (LA) system - anaerobic.
• ·         O2 system - aerobic.

1. The ATP/CP system.
This is sometimes called the anaerobic alactic system. It is anaerobic because whilst using it, oxygen is not supplied from the air breathed in. Adenosine triphosphate (ATP) is a compound necessary for muscular contraction. The compound is stored in the muscles and a very quick contraction, lasting only a fraction of a second uses it all. For an exercise lasting longer than this, another compound called creatine phosphate (CP) is used. CP can provide a muscle with virtually instant energy without the need for oxygen. It is the muscle's emergency system, but it is stored in only very small amounts and so is depleted very quickly.

In an untrained person ATP/CP is exhausted in about 8 seconds. Through proper training it can be made to last only a few more seconds.

Anything requiring short bursts of energy at maximum intensity relies heavily on this system.

It takes about three minutes of complete rest to get a fairly full restoration of ATP. Proper training to maximize ATP/CP would be short bursts of 15 seconds or less at maximum intensity, with rest periods between short bursts of three minutes or more.

It takes only two to three weeks to build up the ATP/CP system. However, it is also lost quickly through disuse. Because the system can be developed quickly it is usually the last of the three energy systems to be built up, with emphasis placed on it only in the last weeks before a major race.

The other two systems take longer to develop so work on them is typically started earlier in the training year.

2. The lactic acid system (or the anaerobic lactic system) - LA system.
This system can also supply the muscle with energy in the absence of oxygen. But it uses glycogen and because of the lack of oxygen, lactic acid is formed. Intense activity of a muscle causes this system to operate at a high level until eventually the build up of lactic acid inhibits the muscles action and causes it to slow down. The blood system removes lactic acid to the liver where it is detoxified. During a recovery period the muscle regains its ability to function. The period of time that the muscle can support this type of effort is up to two minutes.

The lactic acid system is trainable. The ability to function with high levels of lactic acid and to dissipate it quickly in rest intervals is best developed with intense efforts of 30 seconds up to 2 or 3 minutes. It can take 6 to 8 weeks of concentrated effort to build up the LA system. This is best carried out during the weeks leading up to a major race, working the LA system 3 or 4 times a week.

3. The aerobic system (O2 system).
This system utilizes breathed in oxygen in the muscle and thus interacts with the cardio respiratory system. The presence of oxygen in the muscle allows stored foodstuffs (mainly glycogen but also protein or fat for very long duration exercise) to be transformed into muscle energy by a series of reactions which avoid the production of lactic acid. The O2 process can therefore continue for as long as the energy demands of the muscle are within the capabilities of the oxygen delivery system and the food store. Lactic acid may well have been built up in previous work bouts because the LA system may have been used first. But in this case transferring from the LA system to the O2 system will allow the lactic acid to somewhat dissipate.

Appropriate training can increase the capabilities of all the components of the aerobic system;

• ·         The oxygen delivery system
• ·         The aerobic machinery within the muscle itself
• ·         The size of the glycogen store.

The aerobic system takes longer than the other two systems to produce energy, but once it starts it is by far the most efficient. Training of the system does however take longer, at least three to four months. For this reason it is best to start the yearly training cycle with emphasis on the O2 system. For the rest of the training year a minimum of 50% of training should still be devoted to the O2 system.

The common approach is to develop the aerobic (O2) system first, then the lactic acid (LA) system and finally the ATP/CP system. There is some evidence to suggest that it is necessary to do at least some LA and ATP/CP work throughout the year just to keep up the stroke rate.

Measurement of aerobic and anaerobic power.

VO2max is oxygen uptake during maximum exertion.  It is the largest amount of oxygen per unit of time that can be transported by the heart and lungs and used in active muscle tissue. VO2max can be expressed in litres of oxygen per minute, or related to body weight and expressed as millilitres per kilogram of body weight per minute.

During a VO2max exertion energy supply is aerobic and anaerobic. The anaerobic energy supply has only a limited capacity and so the person will be forced to cycle more slowly after a short period of time. As the athlete approaches his/her VO2max there is a point where the effort becomes anaerobic. This is called the anaerobic threshold and it is the point at which maximum exertion can be maintained in an aerobic state. Endurance loads, typical of a cycling time trial must therefore be at a level just below Vo2max, at the anaerobic threshold. In an untrained individual this may be at about 70% of VO2max, but in a well trained person this may be at 85% (or even more) of VO2max.

Under the influence of training, VO2max is increased. More importantly training significantly increases the percentage of VO2max at which the exertion can be maintained for a long time.

The aerobic system is excellent and can be trained until old age. Improvements of capacity of a factor of 50 have been recorded. The heart rate at the anaerobic threshold can be called the 'Optimum Heart Rate (OHR)' and training to maximize this is the key to success in time trials.

It is believed that the best way to improve the anaerobic threshold - to improve the amount of work that an athlete can do before he/she lapses into an anaerobic state - is to do a lot of training at the anaerobic threshold or at levels which alternate just below and just above the threshold.

How do I train effectively?

Each training session should have a clear objective, targeting specific energy system(s). A heart rate monitor enables the level of intensity to be monitored.Thus the athlete can ensure that the training session is carried out effectively. Generally, percentage of maximum hear rate (MHR) is used as a guide to the level of intensity.

The appropriate levels of intensity, as a percentage of MHR, used in 'Training for Cycling Time Trials’ are:

Long continuous rides at this intensity directly stimulate the aerobic system, without taxing the LA system. This creates a better oxygen transport system, by creating new capillary beds in the pedaling muscles and enlarging existing capillary beds. It also improves the efficiency of the heart, revealed by a lowering resting pulse rate.

Building a sound aerobic base is essential for endurance in races but also to prepare the body for the harder anaerobic threshold, and lactic acid training sessions that come later.

The two key factors in determining the amount of blood pumped are heart stroke and heart rate. Intermittent work improves heart stroke volume, the amount of blood pumped with each heart stroke. Achieving maximum heart stroke several times per workout provides a great stimulus for improving heart stroke.

However, interval training should be mixed with steady state continuous rides, firstly to prevent 'burn out' (interval sessions all the time would be too hard) but also because there is evidence to suggest that improvements to VO2max are not as long lasting if they are not based on a sound aerobic base.

The energy system targeted by interval training depends on the following 5 factors:

• Work interval duration
• Work interval intensity
• Rest interval duration
• Number of sets and repetitions
• Number of interval sessions per week

Work interval duration
The previous discussion on the body's three energy systems reveals how the work interval affects each of the systems.

Work intervals of longer than five minutes place major emphasis on the aerobic system (O2). The aerobic system is predominant in cycling time trials. Even for all out sprinters a good aerobic base is essential. So the development of the O2 system is a fundamental element in all athletes training schedules.

To emphasise the lactic acid system (LA) all out efforts of 40 to 150 seconds are required. This trains the body to operate at high levels of lactic acid, particularly work intervals of 90 to 150 seconds.

The ATP/CP system is targetted with all out sprints of 15 seconds, with rest intervals of 45 seconds up to but 4 minutes. This allows the ATP/CP system to be used over and over at maximum intensity without the build up of lactic acid. The longer rest enables the ATP/CP stores to be replenished before the next effort.

Work interval intensity
It is essential that the various work intervals are carried out at the correct intensity.

The 15 second sprints targetting the ATP/CP system must be carried out at the maximum intensity.

To target the lactic acid system work intervals should be over 85% of maximum heart rate.

The O2 system is best developed at levels 2 and 3 (extensive and intensive endurance levels). The O2 system is also developed by longer continuous rides at level 1, but development of the O2 system is faster at levels 2 and 3. However level 1 rides also train the body to metabolise fats as an energy source, develop muscle capilliary systems and to accustom the rider to longer periods in the saddle.

Rest interval duration.
The rest interval allows the body to recharge before another intense interval is attempted.

The rest interval allows the ATP/CP system to recover. This system recovers by:

• ·         50% in 30 seconds
• ·         75% in 60 seconds
• ·         88% in 90 seconds
• ·         95% in 120 seconds
• ·         99% in 180 seconds

In training the aerobic system (O2) the rest interval can be short because there is no great depletion of ATP/CP or build up of lactic acid. However the rest interval should be easy riding, since anything more could gradually produce lactic acid, such that subsequent work intervals will increasingly target the LA system.

Targetting the ATP/CP system requires longer rest intervals (up to 3 minutes) as this allows full recovery of the system before the next effort.

There are two approaches to the rest interval when targetting the lactic acid (LA) system.

1. A rest period over twice the length of the work period allows almost complete recovery. The rest interval is very easy pedalling so that the lactic acid is dissipated and the body is ready for the next intense effort.

2. A short rest interval (say, half the length of the work period) at a medium intensity partly blocks the full restoration of ATP/CP so that the next work intervals will be at increasing levels of lactate. Thus the LA system is stressed relative to capacity at the time of the exertion, not just relative to absolute capacity. This type of work out is very demanding and cannot be repeated too frequently (e.g. every day).

Number of sets and repetitions.
The number of repetitions is the number of times the high intensity/rest period process is repeated. Repetitions are grouped into sets, and a longer rest is taken between sets. This provides longer recovery such that more intensive work can be undertaken in the work intervals in the following set.

Determining the appropriate number of sets and repetitions has to be based on each individual’s capability. An elite athlete will be capable of more repetitions and sets than an intermediate or beginner. If the intermediate or beginner tries to do too much, too soon, then he or she can actually get worse.

The aim of training should be to start conservatively and to gradually increase the number and intensity of intervals over a reasonable period of weeks and months.

How does the individual know how many repetitions and sets he/she should undertake? Basically the developing athlete should strive to do as much as possible, but still recover from it. The elite athlete will probably have achieved a high number (over a number of years) and will simply maintain the high level year after year.

During a single interval session, when the performance in a single effort period falls by as much 5 to 10%, then the repetitions should be terminated – the body is not recovering from the efforts well enough to continue to train the relevant energy system. The performance can be assessed as the distance covered, or the average speed achieved during the effort period (ideally on a calibrated turbo trainer, but if the intervals are being carried out on the road allow for variations in road conditions and wind speed etc.).

Number of work intervals per week.
The number of interval sessions per week or month, again depends on the individual’s ability to recover. One method is to check the resting pulse rate every morning. If it is 5 or 6 beats above normal this is a strong indication that the body has not fully recovered and should not be put through a hard workout until the resting pulse comes down again. Otherwise the overtraining syndrome may start. Another indicator is just how the individual feels that day, it is said that ‘you should listen to your body’. If you feel sluggish and not up to a hard effort then you probably haven’t recovered enough. However, be honest with yourself!

Interval sessions – key points.
It is very important to understand the interrelationship between the 5 variables which make up interval training.

• Work interval duration
• Work interval intensity
• Rest interval duration
• Number of sets and repetitions
• Number of interval sessions per week

If the proper intensity or rest periods are not observed the wrong energy system may be emphasized.

The aim of training is to gradually increase the number and intensity of intervals. This is called progressive overload and can be achieved by:

• Increasing the pace of each effort session.
• Reducing the rest period between efforts.
• Increasing the number of work intervals in the session.
• Increasing the number of sets undertaken (up to three).
• A combination of all the above.

One method of determining when to increase the intensity is to check the heart rate after the last interval of the workout. The heart rate is taken one and a half minutes after the last effort session. If the heart rate is lower after several identical sessions it is time to increase the intensity. Another method is to check performance during the intensity intervals. If the distance traveled or average speed has increased after identical sessions then the intensity can be increased.

The method of increasing the intensity depends on the energy system being targeted. For example, if the aerobic system (O2) is being targetted by undertaking longer intervals (say 8 minutes) the intensity should be increased by gradually reducing the rest intervals. If however the ATP/CP system is targeted by undertaking 15 second all out efforts with rest intervals of up to 4 minutes then the intensity is increased by increasing the effort expended in the 15 seconds. If the rest interval is reduced the emphasis would move to training the LA (lactate) system.

Whilst it is easy to make mistakes in arranging all the variables and end up emphasizing a system you didn’t intend to, it is possible to do combination workouts in which two or more energy systems are worked in the same session, even in the same interval. For example a basically aerobic session could include some short accelerations of 15 seconds to work the ATP/CP system or longer sprints of 30 seconds up to 2 minutes to work the lactic acid system.

Muscle and cardiovascular development.
It is the combination of cardiovascular conditioning and muscle development that permits the intensity and volume of training necessary to maximize the body’s response to training.

Within the muscles there are two types of muscle fibre:

• “Slow twitch” – which support endurance efforts. These fibres require a steady supply of oxygen, stored for the onset of work, but quickly requiring replenishment from outside air. These fibres have access to oxygen through a highly developed network of capillaries, and are very resistant to fatigue.
• “Fast twitch” - supporting speed and power efforts. These fibres may be called upon instantly for speed and power without having to wait for the oxygen supply to be replenished. The more “fast twitch” fibres a rider has the faster he/she may fatigue, only being able to operate at top speed for a short period of time.

The proportion of each type of muscle fibre is determined at birth. Thus some athletes have greater potential to become sprinters whilst others are more suited to endurance events.

Continuous long rides improve the function of the slow-twitch muscle fibres, whilst short high intensity efforts focus on fast twitch muscle fibres.

Warm up and Warm Down.
An adequate warm up prepares muscles for work by supplying them with more blood and oxygen. The warmth increases the speed of the chemical reactions which liberate energy from within the muscles. A good warm up also reduces the resistance of muscles, tendons and ligaments to joint movements by increasing the pliability of the tissues.

If no warm up is carried out the muscles are shocked into sudden violent exertion without adequate oxygen. This forces the muscles to furnish energy from the anaerobic system, for the first two or three minutes. The body goes into oxygen debt and perceptible amounts of lactic acid are formed. The oxygen debt must be repaid in the following minutes forcing the athlete to slow down until recovery has taken place.

It is equally important to adequately warm down. The warm down (easy pedaling at a medium to low cadence) helps to dissipate lactic acid, built up during the race or training session, from the muscles and bloodstream. This accelerates recovery before the next session. Warm down stretching of the muscles also helps by restoring flexibility to the major pedaling muscles.