INTERVALS

The concept of interval training was first developed by a Czech runner 
called Zatopek.  He believed that as the heart was a muscle it could be 
trained like any other.  The best training he decided was a series of 
stress-rest repetitions where the heart rate was increased then allowed to 
recover.  He did this during the late forties and was way ahead of his 
contemporaries who were mostly favouring long, slow, distance (LSD) 
type running.  Zatopek's method's culminated in him winning the 
running triple crown (5000m, 10,000m and marathon) at the 1952 
Helsinki Olympic's.  A feat never again repeated by anyone.  Since 
Zatopek's time there have been much study and many variations of his 
methods.  Today however there are no top class runners who don't use 
interval training at some time during race preparation.

Intervals consist of a series efforts followed by active or passive rest 
usually at a pace faster than a continuous type training run.  There are 
four things that you can alter in an interval training session.  They are 
distance or time, rest time or distance, effort, and the number of 
repetitions.   Each of these can be varied to tailor the interval session to a 
persons individual goals.

Interval sessions are also quite stressful on the body.  They should be 
followed by a relatively easy training day and more than one of these 
sessions in a week should be left to the elite athletes.  Also as it is quite 
jarring on the feet/body the softer the surface the better off you are from 
an injury perspective.  Softer surfaces are also slower than hard surfaces 
so times will be affected.  Races are also usually on hard surfaces such as 
roads so a small percentage of your intervals should mimic race 
conditions.

I will briefly outline the some generic types of intervals and what they 
best train.  Many different coaches have different names for these types 
of sessions.  I will try and use the most common names.

Stride-Outs/Form Intervals
These are fairly short intervals of between 50m and 200m whose primary 
aim is to improve your running efficiency.  They get your body used to 
travelling much faster than you are going to race.  The theory is that if 
you continually do this then some adaptations will occur which mean that 
running slower will be easier.  They can be done at any time during a 
season but are common in the week leading up to a race with long rests 
to get your feet moving faster.

Rhythm Intervals
These are the most common form of intervals.  They are run at a pace 
just faster than race pace with a fairly short rest between each interval.  
Sets above 10 repetitions are not uncommon with Rhythm Intervals.  If 
you are training for a 10km event an example of a Rhythm interval 
session would be 8 x 400m with 1.5mins rest between each interval run 
at 5km race pace.  Although intervals ranging from 400m through to 
3000m can be used when training for any event, normally the longer the 
event you are training for the longer the length of the intervals you would 
do.  Marathon intervals are typically 800m, 1000m, and 1500m.

Power Intervals
These are directly aimed are increasing both the strength of your muscles 
and your VO2max and are designed to be run near your VO2max.  For 
these intervals you run quite fast (95%) and have a longer rest.  Also 
there are normally less repetitions than Rhythm interval sessions.  You 
may have as much as 5 minutes rest between each interval in a power 
session.  I prefer these sessions early on in the lead up to a race.  This is 
to have maximum effect on VO2max early.  Later on I switch to Rhythm 
intervals to fine tune the Anaerobic Threshold.

Hill Repeats
These intervals are vary hard and have significant effect on strength and 
power development within your leg muscles.    Most muscles have two 
types of fibres: - fast twitch and slow twitch.  The fast twitch are used 
when you run fast and to train them you can run fast, or..... research has 
shown that hill work strengthens them as well.   Fast twitch fibres are 
recruited by the amount of power exerted by the muscle not its speed.  
Hills and intervals both require a high power output.  They are also 
useful if your race will be on a hilly course.  Different muscles are also 
used in hill running compared to racing on the flat.  Strength is also 
more important in the hills.  The idea is to have a series of hard uphill 
efforts (say 6-8) jogging/walking down the hill in between each repeat.  
Remember to take it easy on the downhill,  the eccentric action required 
can cause injury.

The Interval Session
Intervals are much more fun if they are done with a group.  They are 
hard sessions and is helpful to have other people to pull you on and to 
provide moral support through the sometimes gruelling sessions.  They 
can also be made quite fun with many different variations possible on the 
main theme.  You should also be sure to both warm-up and cool down 
thoroughly and a do series of slow accelerations to ease you into the 
session.  Some people also stretch.

Fartlek
A discussion on Intervals would not be complete without mention of 
Fartlek.  This form of training was developed in Sweden and means 
Speed Play.  It is an unstructured form of intervals where you run fast 
and slow for as long as you like.  The length of the fast bits can range 
from 30 seconds to a few minutes.   It is typically done in a hilly country 
area with grass and dirt tracks where you can run with the wind being as 
playful as you can.
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