Extensive Intervals refer to a category of crucial workouts that are used for building aerobic power in middle distance runners. They are introduced in the general preparation period and emphasized during the specific preparation and pre-competitive periods. Aerobic power development requires many weeks of training because adaptations includes both bio-chemical and structural changes to the body. During tapering and peaking, Extensive Intervals are a small component of the competition period and are only prescribed to maintain the aerobic foundation developed in earlier training periods.
Extensive Interval workouts (also called Extensive Tempo workouts by some authors) are done directly at, or within a few percentage points of, vVO2 max date pace. If placed on an energy continuum, Extensive Intervals would occupy the range of 93%-109% of vVO2 max.
Many endurance scholars and coaches designate vVO2 max (velocity at present day max aerobic power) as the single most important marker of aerobic development and aerobic fitness. Aerobic power development requires 22-26 weeks of selective training in order to reach maximum aerobic fitness for that particular moment in time (chronological age, training age) for a middle distance runner.
Total volume of training (mileage) is an important factor in central aerobic power development, even if done at slow paces near the aerobic threshold. High training volume stimulates increased blood volume, increased erythrocyte population, angiogenesis, and the enlargement of left ventricle for greater stroke volume. However, complete aerobic power development also includes adaptations at the peripheral structures; that is changes to the components of the muscle cell. These changes include increased myoglobin volume, dramatic proliferation of mitochondria, increased size of mitochondria, and mitochondrial enzyme increases in volume and activity.
* Coaching Resource: The Mile: Successful Coaching Strategies
Most peripheral changes somewhat occur with a regular stimulus of high and slow volume, but at a lesser rate than central changes. Peripheral development requires a stronger stimulus then high volume runs done at the aerobic threshold to speed along adaptations: this explains the need for Extensive Intervals for middle distance runners.
Extensive Interval work is done in a range surrounding vVO2 max. By following the definition of intervals, the runner should be able to do a greater volume of total work for the session then if done in a single continuous run. In order to give peripheral aerobic power development the ideal stimulus, a session volume of 4800-9600 meters is required. High school runners with a training age of three or four should concentrate around 6400 meters for a session.
To do the work correctly, the runners must always remind themselves of these three important thoughts:
1) Since the workout pace is at or surrounding vVO2 max pace (two mile pace), the first half of the session will feel “easier” than the second half; much care must be taken to keep the first half work at the correct pace,
2) if done correctly, the real adaptive benefit of the work will be during the second half of the session where the pace will seem much more difficult, and the athlete will have to push hard to accomplish the target pace, and
3) enough rest interval will be given to ensure that the athlete can replicate the correct work pace over the entire session.
Most scholars and coaches agree a 1:1 ratio of work to recovery within an Extensive Interval session is the optimum stimulus for this type of work, especially for high school runners. Older and more elite runners can shorten the recovery by 25%.
When setting up Extensive Interval work session training goal times for a middle distance runner, use their present day vVO2 max marker as the index velocity and then do the math from that. For example, the workout idea is 8 x 800 meters. The target goal time for each runner will be 105% of their present day vVO2 max effort reduced to 800 meters.
Let’s say the runner has a vVO2 max of 5:00/mile or 300 seconds/mile. The math is 300/1.05 (105%) = 285 seconds divided by 2 to reduce to 800 meter training pace, which equals 142 seconds or 2:22 per 800 effort. The Extensive Interval work session for the day, for this runner, would be 8 x 800 meters at 2:22 with a 2:30 recovery interval between each repeated effort.
Table 1 describes some other Extensive Interval session examples. These are just suggestions. Effort, intensity, and number, can all be modified within the guidelines. The recovery interval is rigidly set. The shorter 400 and 800 meter efforts should most benefit the long sprinter moving up to middle distance, as they will greatly struggle with the longer efforts.
* Additional Teaching Resource: Every 800m – 1600m Workout For The Entire High School Season
However, it is through Extensive Intervals that aerobic power rather than aerobic capacity is achieved. In other words: how fast one can aerobically run rather than how far one can aerobically run. Both central and peripheral aerobic power development is required to achieve true aerobic fitness. One Extensive Interval session should be found in every microcycle of the appropriate training periods and be set up according to each individual runners vVO2 max profile.