Why circuit training is overrated part two

    In part one I deep dived circuit training and how it does not elicit the intended strength adaptations. In today's post I'll deep dive how the circuit training aerobic adaptations do not meet the intended aerobic adaptations. 

    We covered neural adaptations, muscle tissue adaptations, and connective tissue adaptations. Now, it is time for the aerobic adaptations. To start we have to go over some vocabulary; heart rate is how many times you heart beats in a minute. Stroke volume is how much blood is pumped per beat. Cardiac Output is the product of heart rate and stroke volume. Blood pressure is the amount of force is produced by the heart. That was a break it down barney style definitions. A more detailed account of the heart pertaining towards exercise can be found here. During the concentric phase (when your muscles contract....i.e. during a bicep curl) your blood pressure increases. Now when the eccentric portion is performed (i.e. lower the weight during a bicep curl) your stroke volume and cardiac output increases. When the Valsalva maneuver is used (process of "holding" your breath to build intra domanial pressure in the abdomen for bracing) your stroke volume and stroke volume will increase at a faster rate. The nonlinear aspect of blood flow is dependent on how many muscles are being activated during the lift. A smaller muscle will not illicit a significant change in blood pressure. On the other hand, a larger muscle will. Due to the eccentric phase (more difficult phase of lifting) the venous return (blood flow returning back to the heart) is initially limited. This is why your heart rate is higher after completion of the set then during the set. During heavy resistance training (20% of maximal voluntary contraction) blood flow is limited to the active muscle due to the contraction of the muscle restricting capillaries. After the completion of the set (rest periods) blood flow is increased resulting in reactive hyperemia. This is a stimulate for muscle growth. 

    The amount of blood flow during a training session is dictated on a few factors: 1) The intensity of the resistance (how much weight are you lifting), 2) Length of time of the effort (how many repetitions) and 3) Size of the muscle activated (Chest vs calf raises). Lifting heavy weights for multiple repetitions generally gives the best results in terms of aerobic response to resistance training. Key word in this style of training is heavy. Performing light bicep curls at the gym in order to get "toned" isn't a thing. Circuit training with lighter weights with the expectations of improving is not the most idea training. Only lifting heavy weights results in the aerobic improvement sought out by circuit training. Aerobic wise the improvements seen aren't as much as strictly performing aerobic exercises.