Exercise intensity

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Exercise intensity refers to how much work is being done when exercising. The intensity has an effect on what fuel the body uses and what kind of adaptations the body makes after exercise (i.e., the training effect).

Fuel used[edit | edit source]

The body uses different amounts of fuels (carbohydrate or fat) depending on the intensity and heart rate. The Heart Rate column below is an estimate for a 20 year old with a Max Heart Rate (MHR) of 200.

Intensity (%MHR)	Heart Rate (bpm)	% Carbohydrate	% Fat
65-70	130-140	40	60
70-75	140-150	50	50
75-80	150-160	65	35
80-85	160-170	80	20
85-90	170-180	90	10
90-95	180-190	95	5
100	190-200	100	-

Training Effect[edit | edit source]

The effect achieved by exercise is affected by the intensity.

Low Intensity (up to 80% MHR)[edit | edit source]

This has the effect of improving general fitness and improves the muscles' ability to use the oxygen delivered to them via the blood. Way of doing this is by increasing the number of capillaries in the muscle.

Medium Intensity (80-85% MHR)[edit | edit source]

This intensity is around anaerobic threshold (AT) and improves an individual's AT - allowing the body to work at a higher intensity while still working aerobically.

High Intensity (85-90% MHR)[edit | edit source]

The heart is a muscle and can be trained to be come stronger and more efficient. This intensity of exercise places a load on the heart causing it to become stronger so it can pump more blood in one contraction.

Flat Out (90-100% MHR)[edit | edit source]

In this region the body works completely anaerobically - causing a quick build up of lactate (lactic acid). This kind of training, despite being very painful, improves the body's anaerobic capacity - the production, removal, and tolerance to lactic acid.

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