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As opposed to steady state aerobic-type exercise involving long duration, continuous, rhythmic, large muscle group activities that consume large volumes of oxygen, a resistance training set is brief, intermittent, uses multiple and isolated muscles, and is considered anaerobic in description. Because differences are evident between aerobic- and anaerobic-type exercise, it is proposed that the methods used for estimating resistance training energy expenditure should be different as compared with walking, jogging, cycling, etc. After a single set of weight lifting, for example, oxygen uptake is greater in the recovery from lifting as opposed to during the actual exercise; likewise, the anaerobic energy expenditure contribution to lifting may exceed exercise oxygen uptake. Recovery energy expenditure also does not appear well related to the anaerobic energy expenditure of the previous exercise. Based on this evidence, it is suggested that anaerobic-type exercise should not be based on aerobic-type models. In terms of excess postexercise oxygen consumption, a hypothesis is presented in regard to how non-steady-state energy expenditure in the immediate recovery from intense exercise should be properly quantified (e.g., in-between resistance training sets). The proposed concept is based on possible substrate or fuel use differences during intense exercise and aerobic recovery and the biochemistry and bioenergetics of glucose, lactate, and fat oxidation. It is proposed that immediately after a single weight lifting bout or in-between resistance training sets, as O2 uptake plummets rapidly back toward pre-exercise levels, a separate energy expenditure conversion is required for recovery that differs from non-steady-state exercise, that is, 1 L of recovery oxygen uptake = 19.6 kJ (4.7 kcal) (not the standard exercise conversion of 1 L of oxygen uptake = 21.1 kJ) (5.0 kcal).