Tyler Robbins Fitness

B.Sc. Biochemistry, Certified Strength and Conditioning Specialist (CSCS), Certified CrossFit Trainer (CCFT/CF-L3), USA Weightlifting Level 1

Aerobic Exercise During the Interset Rest Period

As part of my membership with the National Strength and Conditioning Association (NSCA), I am subscribed to the Strength and Conditioning Journal that publishes research studies on varying topics from the health and fitness field.

The latest addition has a brief review on an interesting topic that has piqued my interest, especially since I am currently making my way through my mass phase. Mohamed, Cronin, and Nosaka discuss "Maximizing Hypertrophic Adaptation - Possible Contributions of Aerobic Exercise in the Interset Rest Period." In laymen's terms, the potential for increased hypertrophy (muscular growth), by using light aerobic exercise between sets rather than just 'passive' rest.

The article discusses the factors involved in hypertrophy. Progressive overload, specific repetition ranges, muscular "time under tension", as well as interset rest periods. Some research has shown that decreased rest periods increase the metabolite buildup in the working muscles and blood stream, which can further increase the affinity for hypertrophy. By using a 1:1 to 1:2 work to rest ratio, individuals can increase their blood metabolite concentrations and force their bodies to not only adapt to the training stimulus, but to increase hypertrophy gains. The one downside to this technique, however, is that as individuals increase their workload or resistance levels, insufficient rest periods can result in decreased force production.

It does not take a rocket scientist to realize that by increasing rest periods between sets, individuals can therefore increase their force output. However, rest periods should be specifically designed to target a specific training goal, no different than repetition range goals, load goals, and "time under tension" intervals. If you were to do a set of chest presses, then go eat lunch and take an hour off, when you return to do a 2nd set of the very same chest press, your body will most certainly have recovered 100% to return and produce similar force outputs. This is not only an inefficient way of working out, but it is also not beneficial for muscular gains, especially in regards to hypertrophy.

Resistance training is a high-force output style of exercise, therefore most of us would be led to believe that the anaerobic energy systems supply 100% of the energy needed. This is simply not true, as triglyceride (fats) levels have been shown to decrease in muscle cells following resistance exercise (lipolysis - utilization of lipids/fats) indicating the fact that aerobic energy systems are at least part of the energy equation.

Although the aerobic energy systems are partially at work here, majority of the force produced during resistance training comes from anaerobic energy stores. This is the primary reason for interset rest, so that the body can 'top-up' its energy stores with 60-120 seconds of rest. Mohamed, Cronin, and Nosaka have studied and discussed the theory that light aerobic exercise between sets can have a number of positive effects on the human body, increasing the affinity for strength and hypertrophic gains. They present a table with proposed benefits to various systems in the body:

Mechanical - Optimize muscle temperature for greater force and velocity output, increase elasticity of muscle for increased work output (force x distance), and improve mechanical efficiency (ratio of energy turnover and mechanical output)

Metabolic - Improves lactate clearance rate and rate of energetic repletion

Hormonal - Greater total anabolic hormone production

Neural - Increase motor unit recruitment, firing frequency, synchronization and reflex potentiation, synergistic contribution, and co-contraction of antagonist

By using very light (50-60% maximum heart rate) aerobic exercise, it is possible to increase the efficiency of rest periods, allowing great hypertrophic gains. If one is to explore this avenue, then you should aim for aerobic exercise that targets the generalized area that has been worked on. For example, if you are training your legs, and have just come off of a set of heavy back squats, some light activity on an exercise bike or jogging can elicit this benefits. Similarly, if working the upper body, using a rowing machine or arm ergometer can improve recovery and circulation to the desired muscles.

This is definitely something that I will explore on my own and test out in my own workouts as the benefits gained sound very plausible.


Photo - http://www.kalisthenixfitnessblog.com/2008_09_01_archive.html