There has long been a separation between cardio training and building muscle. Cardio has historically been a tool to burn fat and reduce body weight in the bodybuilding/figure/bikini crowd. For the mainstream, cardio training is used for its ability to improve heart health, lower blood pressure, and control weight gain. A body that is cardiovascularly fit in general will function in every way much better than its untrained counterpart; it will be less likely to get sick, develop heart disease and will also feel better. However, High Intensity Interval Training (HIIT), and it’s derivative, Short Burst Cardio Training(SBCT) has been shown to provide numerous benefits above and beyond health and fat loss; they have been shown to assist in building muscle as well.
High Intensity Interval Training is a blanket term used to describe an exercise strategy alternating periods of short intense anaerobic exercise with less-intense recovery periods in rapid succession, with up to 12 cycles between high intensity and recovery. The intense portions usually last from 30 seconds to two minutes coupled with a minute or two of recovery in between. Short Burst Cardio Training is a form of conventional HIIT, however, the high intensity portions of the training last longer, from three to 10 minutes along with a two to four minute recovery period. SBCT uses just one to three cycles of high intensity and recovery intervals. By using longer high intensity frames, SBCT is able to further train and improve blood flow and energy expenditure over shorter high intensity intervals, leading to a number of benefits to building muscle:
- Increased capacity for intense training sets: For high level lifters, failure on a set often occurs as the result of exhausting the oxygen and fuel supply to the trained muscle. This is particularly true on compound movements involving multiple large muscle groups such as squats and deadlifts. While the muscle has the strength to push forward, it is limited by the cardiovascular systems ability to deliver fuel and oxygen during the set. SBCT greatly increases the blood and fuel flow to the muscle as well as how the body is able to efficiently utilize fuel, enabling more reps with more weight. Remarkably, SBCT even has the ability to increase the number of capillaries in the muscle tissue, further increasing blood flow to greater portions of the muscle and improving performance.
- Shortened refractory period between sets: Because of the increased oxygen and fuel delivery to the muscle, recovery time between sets is greatly improved with SBCT. The increased blood flow and energy deliver replenishes oxygen and fuel quicker, requiring less time in between sets as well as a more complete, less taxing recovery. This not only means your next set can come sooner, but usually means it will be better as well, as you are more capable of repetitive high intensity sets.
- Quicker and better recovery: Recovery also is improved with muscle repair in the hours and days post-workout. Increased blood exchange and fuel delivery allow the muscle to repair itself quicker as well as shuttle your post-workout nutrition to the affected areas more efficiently. Quicker recovery results in higher quality workouts more often, which results in a higher level of progress.
- Improved insulin sensitivity: A study published by Adams OP in February 2013 used a protocol very similar to SBCT (7.5 minutes ultra-high intensity, single session) and demonstrated a profound improvement in both insulin sensitivity and glucose usage. The study showed GLUT4 (insulin-regulated glucose transporter) which is responsible for insulin-regulated glucose transport into the cell, increased by a remarkable 369% from 48 to 72 hours post SBCT training. It also showed blood glucose levels improved by 13% over the same time period. Improved insulin sensitivity and blood glucose means less fat storage and a greatly improved ability to utilize the carbs we eat for fueling and repairing muscles.
Cardiovascular fitness is a boon to overall health, longevity and well-being. Many lifters often skip it or substantially limit it for fear of losing hard earned muscle. Incorporating less than 10 minutes of short burst cardio training per day, however, has the ability to not only improve your overall health and burn fat, but also to push through muscle-building plateaus and take you to the next level. It is recommended that SBCT be performed every other day at minimum to maintain the benefits ongoing. This duration and amount is all that is needed to reap the full benefits and short enough to avoid cannibalizing any muscle gains.