maximum heart rate) can be used. Due to the short duration of most intervals, heart rate does
not give an accurate measure of intensity and trainees will have to subjectively estimate
intensity level.
In most cases, recovery in between intervals should be performed at low intensities,
around 50-60% of maximum heart rate. The recovery should almost always be active. After a
maximal sprint on a bike, recover with light spinning instead of stopping completely. This will help
with recovery between intervals by allowing the body to remove lactic acid from the muscles.
Time
The duration of a given interval may be anywhere from fifteen seconds to five minutes or
more. Generally, the shorter the interval the higher the intensity which is used and vice versa.
Fifteen second intervals are done at maximal effort while a five minute interval may be done just
above lactate threshold. The recovery time between intervals can be measured one of two ways:
- Relative to the work interval: With this method, the duration of rest is expressed in some ratio
of time to the work interval. A 90 second interval might have a rest interval of 2:1 meaning that
twice as much rest (180 seconds or 3 minutes) would be given. A five minute interval would
require a 1:1 rest interval (5’). - When heart rate returns to 120 beats per minute: this method is more individual and takes
fitness level into account. However it requires some method of measuring heart rate during
exercise.
Total interval time
The total amount of intervals which should be done in any given workout ranges from 5 to
25 minutes of high intensity work not counting recovery. Obviously, this is affected by the length
of the interval done. A cyclist doing 1 minute repeats would need to do from 5 to 25 total repeats.
A sprinter might need to do 50 repeats of 15 second intervals.
In general, beginners should start with the low number of intervals and increase the
number of intervals before increasing the intensity. Once the high number of intervals is reached,
intensity can be further increased.
Type of activity
Intervals can be done on any type of equipment or outdoors. For individuals carrying extra
bodyweight who wish to incorporate intervals to hasten fat loss, non-impact activities such as
cycling or the stair climber are preferable to activities such as sprinting which may impose too
much pounding on the joints. Athletes will need to perform intervals in their particular sport.
Table 2 provides guidelines for interval training. Trainees should always warm-up and cool-down
for at least 5 minutes at low intensities prior to interval training.