All About Power

Let's face it, most of us don't have the time or the energy to commit to long cardio workouts. Hence the growing popularity of the time-efficient 30-minute sessions. But, how can we ensure that we get the most bang for our buck in 30 minutes? Studies have shown that EPOC (Excess Post-Exercise Oxygen Consumption) is driven by intensity, not volume. Since the number of calories we burn is dependent upon the amount of oxygen we consume, let's add intensity to our short training sessions!

Intensity is achieved by training with power. To train with power, we need to target our fast-twitch muscle fibers and their anaerobic energy systems. This can be done with a carefully planned HIIT (High Intensity Interval Training) format. I say, "carefully planned" because if enough time between intervals is not allowed for the anaerobic energy systems to replenish their ATPs, the purpose of the training is defeated due to diminished power output.

So, what's an appropriate HIIT format for power training? VIIT (Variable Intensity Interval Training) is a type of HIIT protocol that combines HIIT and CV (Cardiovascular) conditioning. This type of training targets the anaerobic energy systems using 30-second all-out power efforts followed by active recovery at a comfortable but challenging intensity. To understand the benefits of this type of training, it helps to understand how the anaerobic energy systems work. During the first few seconds of an all-out effort, our muscles use their immediate energy source, ATP (Adenosine Triphosphate), which is located on the myosin heads of the contractile proteins of the muscle fibers. Energy is released when ATP is broken down to ADP (Adenosine Diphosphate), Pi (Inorganic Phosphate) and H+ (Hydrogen Proton). As the effort continues, CP (Creatine Phosphate) is split by the enzyme, creatine kinase, and the energy released from that reaction is used to resynthesize ATP from ADP and Pi. When CP is depleted, anaerobic glycolysis takes over, breaking down glucose into pyruvate. Pyruvate converts to lactate by taking on the H+ produced during glycolysis, preventing the environment from becoming too acidic. Lactate is pushed from the muscle cells into the blood to be buffered. When we reach the point of breathlessness after our 30-second all-out effort, we know we have used our anaerobic systems because expiration of CO2 is a result of our buffering system.

So, what's the benefit of training this way? When we train anaerobically, our body oxidizes fat more rapidly, preparing for an eventual increase in its' usage. This rapidity equates to more calories being burned. Additionally, during active recovery of the anaerobic systems, we use our aerobic system to replenish ATPs. This is the only system in which fat is burned. It is comprised of the mitochondria, which encompasses the Krebs cycle, i.e. the fat-burning fireplace. Our muscle cells contain anywhere from 400-2000 mitochondria. Mitochondria have their own DNA and will adapt to VIIT by getting 35% bigger and replicating by 15-50%. More fat-burning factories and more calories burned by training consistently with power for just 30 minutes sounds pretty good to me!

Let's add intensity to our short training sessions!

References:
Comana, Fabio. "HIIT vs. HVIT." IDEA Health & Fitness Association.
Kravitz, Len. "Metabolic Conditioning: Myths, Mysteries and Monster Workouts." 2016 IDEA Health & Fitness Association.
Kang, Jie. "Bioenergetics Primer for Exercise Science." Human Kinetics, 2008.