There are 3 major energy pathways in the human body, known as the aerobic, anaerobic and ATP/PC pathways. They can and often do work simultaneously, but the demand on each depends on the intensity and duration of exercise.
To understand the use of the energy systems it helps to consider, if you start paddling slowly, and then progressively increase pace for 15 minutes until you are doing a maximum sprint, which can only be maintained for a few seconds.
In the first few minutes all the energy is produced by the aerobic pathway, that is energy produced ‘with oxygen’. As the pace goes up clearly more energy is required, we start to breathe more heavily and this extra energy comes from greater use of the aerobic pathway. As the pace goes up again, more and more energy is demanded of the aerobic energy pathway, however it can only supply energy at a maximum rate, and when we reach a pace that could only be sustained for about 8 minutes then the aerobic pathway is working at maximum.
Further increases in pace are possible but the additional energy is supplied by the anaerobic pathway, that is energy produced ‘without oxygen’. However, this energy pathway has some nasty side effects, notably lactic acid is given off and causes fatigue. If the pace goes up again it requires more anaerobic energy, and thus quicker build up of lactic acid and increasingly intense fatigue.
Finally if the paddler sprints all out the extra energy for this really high intensity work comes from ATP and PC, which are small very short-term stores of energy in the muscle.
(N.B. The aerobic pathway will continue supplying energy at its maximum rate right to the end of the sprint, its just that it cannot supply all the energy demanded, and other pathways must contribute at these high speeds.)
Training for the 3 energy pathways is considered below. The energy
pathways involved in an event represent just one part of the myriad
factors important for physical training and competition. The period of
training given is just an indication to achieve a reasonable level of
fitness for each. Of course we can (and some people do!) spend a
lifetime continually trying to improve each of these qualities.
8.2.1 The Aerobic Pathway
Also known as the O2 system, aerobic means "with oxygen", this pathway
is used when sufficient oxygen is available to meet the energy needs.
In this case the fuels fatty acids and glycogen are metabolised with
oxygen to provide the energy (ATP) for muscle contraction. Typically
the aerobic pathway is used for long periods of low to medium
intensity. This is the endurance system and you can use it almost
indefinitely. A marathon runner trains and races at a relatively low
intensity (they do go fast, but that’s just because they are very fit!)
all the energy for their exercise will be produced by the aerobic
pathway. It is the most efficient of the three systems for converting
fuel into energy.
During easy exercise this system will also dissipate any lactic acid
built up in the muscles from higher intensity bouts using the anaerobic
energy system.
It takes 3 to 4 months of steady training to develop aerobic fitness.
To improve aerobic fitness it takes 3 to 6 sessions per week and to
maintain existing aerobic fitness it takes 2 to 3 sessions per week.
You should also include 1 speed session per week to keep up some speed.
There are 3 main ways to develop aerobic fitness:
Training sessions that are a minimum of 45 minutes of steady-paced
effort and preferably over an hour. During these sessions the intensity
should not be tiring, but it is the duration that leads to fatigue.
This training is primarily for the aerobic ability of the muscles, and
you should be able to talk to people while doing this type of training,
not be gasping for breath. This type of training is particularly good
for general fitness, health and weight loss without being too hard.
Repeated hard efforts of between 3-6 minutes. These sessions develop
the maximum rate of the aerobic system. As they are hard efforts there
will be some anaerobic metabolism, but this is required to work the
heart and lungs to a high level. At the end of these efforts you will
be breathing very hard and it may take a minute or so for this to come
back to normal.
Threshold training 20-40 minutes of hard effort, where the pace is very
close to maximum for the distance. This trains the aerobic system just
at the point where noticeable amounts of anaerobic energy are produced,
and thus the aerobic pathway adapts to working well even if there is
some lactic acid and fatigue. During this type of training you will be
breathing quite hard, but if you stopped your breathing would come down
to normal quickly.
8.2.2 The Anaerobic Pathway
Used for limited periods of fairly high intensity effort. It is the
major energy pathway for events lasting from 10 to 90 s. For sports
events of this duration the intensity is too high for purely the
aerobic pathway (which can only supply energy at limited rate) and most
of the energy comes from the anaerobic pathway, which involves the
metabolism of glycogen "without oxygen". This reaction has a by-
product of lactic acid, which causes fatigue – basically the intense
burning sensation and failure of muscle contraction at the end of a
400m running race as the legs turn to jelly. The higher the rate of
energy supply from this anaerobic pathway the faster the build up of
lactic acid and the quicker the onset of fatigue.
This energy system is most important for long sprints (10 –90 s), but also important for middle distance events (90 – 360 s).
The ability of muscles to work with lactic acid build up and the
consequent fatigue can be trained using interval training, typically
reapeated efforts of 30 seconds to 2 minute. It takes 6 to 8 weeks of
training to develop the anaerobic system. To improve fitness it takes 2
to 4 sessions per week and to maintain existing fitness it takes 1 to 2
sessions per week.
You normally start to train the anaerobic system about 8 weeks before
the event, and between 6 and 2 weeks prior to the event your training
should be at its most intense. It is important to maintain your aerobic
fitness as well.
A typical anaerobic session would be:
(2 min on, 2 min off) * 10
10, 20,-----90, 100, 90,------20, 10 stroke pyramid
sprints for the length of the pontoon
{(40 on, 20 off) *3, (80 on, 40 off) *3, (40 on, 20 off) *3} *3
8.2.3 The ATP/PC Pathway
Used for very short periods of maximum intensity effort. ATP (Adenosine
triphosphate) and PC (phospho-creatine) are energy stores in the
muscles that last for less than 10 seconds of all-out maximum
sprinting. It takes ~2 min of rest or easy work before these stores are
replenished. This is the main energy pathway for a 60-m running sprint
(<7s). This energy pathway does not require oxygen or produce any
nasty by-products.
This energy system is most important for very short sprints (<10 s), but also medium sprints (10 – 30 s).
Training is thought to increase the rate of energy supply from ATP-PC
i.e. faster maximum speed and extend the time it lasts for by a few
seconds.
This system can be trained in 3-4 weeks and is lost in a similar time, so tends to be trained in the month before the event.
A typical ATP/CP session would be:
10 second effort every 2 minutes *20
10 second sprints during a long steady paddle
practising starts from standstill
When planning training schedules, try to spread the types of training
out. If you have a hard interval session one day, have a steady aerobic
session the next day etc.
