Training Intensities - the Scientific Way

Marathon running is all about endurance and that means not to fatigue too early. Increased lactate levels in our blood is a objective measure of how fatigued we are. Hence we are looking for ways to keep the lactate accumulation low.

Oversimplified, we have two types of muscle fibres: slow twitch and fast twitch. While, the slow twitch muscles provide a solid, sustainable aerobic activity at a lower intensity over a long period of time. Slow twitch muscles use a combination of carbohydrates, protein and fat and large amounts of oxygen. Fast twitch muscles can contract more quickly and with greater force but can sustain only short, anaerobic bursts before the activity becomes painful. Fast twitch muscles use large amounts of glucose and little oxygen and produce large amounts of lactate acids.

Thresholds

Aerobic Threshold

Training at or below our aerobic threshold utilizes mostly slow twitch muscles, produces very little lactate acid and hence allows us to maintain the activity for a very long period of time.

We call it zone 1. Running a marathon is an activity at or around our aerobic threshold.

Lactate Threshold

As the intensity increases past the aerobic threshold fast twitch muscles are utilized more and lactate levels in our blood rise. Our body is able to maintain a elevated but stable level of lactates based on the intensity of the activity . At the lactate threshold our body is no longer able to maintain a balance and lactate level begin to rise uncontrollably until our muscles loose the ability to maintain the intensity and we have to stop.

We call the intensity around the lactate threshold zone 3, the intensity between the aerobic threshold and the lactate threshold is referred to as zone 2. Beyond the lactate threshold is zone 4. Exercising in zone 2 typically lets us fatigue within 20-60mins, e.g. a 10km race is run at this intensity. A 5km race can be run at a higher intensity, e.g. in zone 4.

VO₂max Threshold

VO₂max refers to the intensity at which we consume to maximum amount of oxygen. The VO₂max threshold provides an upper limit to zone 4 and is called zone 5. Exercising at the VO₂max threshold is only possible for a few minutes.

Training

For endurance sports like long distance running we rely mainly on aerobic exercise, hence a high aerobic threshold is very important. The good news is that through training we can improve the aerobic and lactate threshold, the VO₂max threshold is more or less fixed and largely determined by our genetics. Each of the thresholds acts as an upper limit to the thresholds below, i.e. we can only improve the aerobic threshold to the level of the lactate threshold and the lactate threshold is bound by the VO₂max threshold.

Training at the aerobic or lactate threshold level will help our muscles to adapt to a higher intensity and raise the respective threshold.

How to Find your Thresholds?

Unfortunately, the exact thresholds can only be determined taking small blood samples during a controlled exercise with levels of increasing intensity. This test is done in a lab environment. Peak Centre for Human Performance offers Lactate & VO₂max assessments and based on the test results individualized training plans.

The next best approximation to train at the thresholds is using a heart-rate monitor and determine the training intensity based on heart rate. 60-65% of your maximum heart rate is assumed as a good intensity for long and easy runs, 80-90% for the lactate threshold.

In the absence of a heart rate monitor we use your previous race performance to determine the appropriate pace group and your training intensity.