The following question has been asked to me many times. If an individual is doing both resistance training and cardiovascular exercise, which one should be done first? For body composition, it makes little difference. Resistance training depletes glycogen stores, so it makes sense to train it first to begin burning fat at the very beginning of the cardiovascular session. When the cardiovascular session is completed first, aerobic metabolism is reached at approximately ninety seconds. The ATP-PC system lasts about ten seconds. The net result is eighty more seconds of fat burning. These eighty seconds are never the reason a program is successful in getting lasting results, improving body composition, or overall health. It is beneficial to include both resistance and cardiovascular training for a well-balanced, comprehensive program to improve body composition, health, and quality of life. The exercise order for the reason mentioned previously is not extremely important.
All energy systems do affect each other and work in concert with one another. Intuition shows that if someone does a one repetition maximum on a squat that will influence the ability to run a marathon later and vice versa. If the energy systems did not work together, this would not be the case. The take home lesson is to do both cardiovascular exercise and resistance training in any order. The eighty seconds you may lose makes very little difference in the long run for a lifetime of health.