dd8f1431_How_Heart_Rate_Zones_Work__Description
[Heart Rate Zone] Zone 3 Goals: Muscular EnduranceEnergy System: Oxidative, Glycolytic 86-95% [Description] 
During an endurance workout, your intensity may reach this zone on slight hills, or when you’re beginning to push the pace on flats. Your body is still primarily functioning aerobically, conversation is possible, and burning in the legs and shortness of breath is minimal, but you’re still “working”.A slight problem with this zone is that the intensity is too high for maximal stimulation of the slow-twitch muscle fibers and fat-burning. As intensity increases from zone 2 to zone 3, oxygen debt becomes greater, and since it takes more oxygen to burn one calorie from fat than from carbohydrate, more carbohydrate and less fat will be burned. Because this zone is high enough to get the physiological “runner’s high” and the satisfaction that you exercised with a slight amount of intensity, many athletes perform mile after mile in this zone, wear their bodies down, and never get significantly faster.On the flip side, this zone is, as you’ll learn later, the “money” zone for many distances in endurance sports, as it allows you to go relatively fast without dipping too significantly into your carbohydrate stores. This is why long interval training sessions or hill climbs in this zone can really help with race pace training and race preparation.Good for 8-20 minute intervals with short recovery periods between intervals.
How Heart Rate Zones Work
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