14 Sep 2007
It is important to understand that even though activities such as weight lifting, football, basketball, volleyball, baseball, tennis, alpine skiing, etc. may be played for several hours, the actual performance time of the activities generally falls within this period. When there's a break in the action, between plays, between sets, etc. the activity or performance stops and the body will begin to recover.
The rate of recovery is so rapid that half of the ATP used is re synthesized within 30 seconds. Ninety-eight percent (98%) of ATP is rebuilt within the first 3 minutes of rest. Therefore, when the action is stopped the body will start to rebuild and reuse ATP for fuel through its anaerobic pathways. This reduces the body's need to burn fat.
Time, therefore is the common denominator for distinguishing between sugar-burning (anaerobic) fat-burning (aerobic) exercises. Intermittent activities that last less than three minutes in continuous duration will always use ATP or Glucose as the primary fuel source.