Middle distance events in track and field consist of races between 800 and 2000 meters because any races within this range share common energy demand characteristics. The three most common events found in this spread include runs of 800 meters, 1500 meters, and 1600 meters, with the anaerobic contribution of these three races varying between 25-40% at exhaustive pace. While the aerobic contribution from the energy system increases as races get longer (because aerobic processes are many and aerobic intermediary compounds have to be moved into mitochondria in stages which all takes more time) is crucial, there is no denying that anaerobic energy derived mainly from glycolysis (less chemical process steps, no mitochondria) is important for middle distance success. Today we consider intensity – can it be too much for middle distance training?
For coaches, understanding the energy system characteristics and demands of middle distance races direct the training program of the runners they train. Simply stated: middle distance runners require a strong mix of aerobic and anaerobic training stimuli to fully develop through a macrocycle. Middle distance runners need much more anaerobic work than 3200 and 5000 meter runners because these longer events are much more aerobic in demand.
The tricky parts of authoring a middle distance training program is in finding the optimum balance between aerobic and anaerobic stimuli, and then in understanding proper recovery intervals before the stimulus is applied again. This applies to both within the training session and the days between similar sessions.
Because middle distance races all have a duration of 90 seconds or more, they are mostly aerobic in the percentage of total energy supplied. This fact directs coaches to develop the most complete aerobic infra-structure that is possible at any particular moment in time. Aerobic development includes greater blood volume, greater capillarization, increased hematocrit, increased cardiac output, increased myoglobin & hemoglobin proteins, and an increase in proliferation, size, and enzyme activity of mitochondria.
The ability to aerobically run far (capacity), fast (power), and efficiently (economy) is a training goal of all middle and long distance runners as it measures their aerobic fitness. Ultimately, aerobic fitness is structurally based and requires weeks, months, and years of time to reach full development, and even then, is highly influenced by the runner’s genome and pace of maturation.
Anaerobic development is not linked to much structural change in the body of the runner. Rather, anaerobic workout stimuli are directed toward changing the biochemistry of inter-cellular and intra-cellular fluids that are vital to the muscle cells environment. The only real change in structure is at the cell level and is an adaptation directed toward opening more gated channels (pores) in the cell membrane to speed the drainage of hydrogen ions and lactate ions out of the cell and into the blood.
Hydrogen and lactate (often inaccurately called “lactic acid”) are byproducts of glycolysis after the energy has been harvested. They both must be disposed of or neutralized in some manner; with the emphasis on hydrogen much higher. If not dealt with, the build-up of hydrogen ions will be the main cause of middle distance fatigue.
The muscle cells ability to handle hydrogen ions is determined by the runner’s anaerobic fitness and is accomplished in two ways. First, by creating more drainage opportunities out of the cell, and the best training stimulus for this adaptation are frequent lactate threshold (LT) and tempo runs where the hydrogen ion build-up is just slightly greater than can be disposed of natively. LT and tempo runs are just strong enough stimuli to turn on specific genes that direct protein synthesis in the ribosomes to open more gated channels.
Once the positively charged hydrogen ions leave the cell they are mainly buffered by hemoglobin in the blood, thus delaying fatigue. The middle distance challenge of LT and tempo runs alone are not enough load to adapt to the really high hydrogen ion build-up on myosin muscle filaments that occurs in a muscle cell running at intense middle distance racing speeds.
This strong build-up of hydrogen at specific race pace will really cause fatigue to advance quickly toward exhaustion. For the hydrogen adaptation at race pace to occur, hydrogen tolerance (often inaccurately called “lactate tolerance”) must also be a focus of anaerobic training for middle distance runners.
* Coaching Resource: The Mile: Successful Coaching Strategies
Hydrogen tolerance work involves occasionally running at a velocity that is between 92-97% of a runner’s maximum velocity. A runner can only do this sort of intense work for 600 meters or less before exhaustion occurs. For that reason, these types of work sessions are set up as interval-style work where the coach directs enough recovery time between the bouts of work so that the session can continue at about the same intensity.
The recovery interval varies with athlete fitness and training focus. As one can imagine, since most of the energy produced in this type of work is a product of glycolysis, the hydrogen ion build-up is tremendously high. Some runners can handle more than others, but all runners have a ceiling of hydrogen that they can tolerate.
The more workouts done at this very high intensity the greater the tolerance adaptation that occurs. This tolerance is mainly an intra-cellular build-up of sodium bicarbonate which is an ion that buffers hydrogen.
Human muscle cells store very little of this buffering molecule natively, but specific training stimuli at sea-level to 1500 meters will direct much more into the muscle cell. The greater the lactate tolerance, then the greater the delaying of fatigue in a middle distance race. There must be a catch to this training or a coach would focus on this intense, high hydrogen ion producing type of work most of the time.
Yes, there is a catch to high intensity anaerobic training for middle distance runners. Too much intensity is very risky in any distance training. Here is why. For every work session that pushes the hydrogen ion build-up to a very high level in the muscle cell there is corresponding damage to mitochondria. The low pH levels resulting from high hydrogen ion amounts cause damage to mitochondrial enzymes rendering the mitochondria incapable of important aerobic respiration for a time. Mitochondria will eventually recover, but it will take several days.
If a coach comes back too soon with another high intensity session, more mitochondrial damage on top of that will occur. It has been shown that one session of 8 x 400 meters done at 94% of a runner’s max velocity, with three minutes interval recovery, will damage 8% of the cell’s mitochondria.
This of course compromises the very important aerobic portion of the energy system. This is the dominate side of energy production for middle distance runners. Further studies have shown that a “somewhat” intense session, such as 4 x 500 meters done at 90% of max velocity, with two minutes interval recovery, will damage 5% of mitochondria. (This workout is less intense because the recovery is shorter.) This is all problematic to mixed aerobic and anaerobic development.
* Additional Teaching Resource: The Training Model for High School Middle Distance
High intensity anaerobic work sessions are very important to achieving maximum middle distance fitness. There is no other way of maximizing hydrogen tolerance capacity. Be very careful so that these types of sessions are well spaced in a middle distance training plan so that the aerobic side of energy production does not begin to drop due to long-term mitochondrial damage. This is the surest sign of middle distance performance plateaus.