Cardio vs Strength:
Does Cardio Kill Strength Gains?

A question of cardio vs strength:

What happens if you are training for strength and power for your sport and you also do cardio workouts?

Strength athletes warm up with cardio, but will too much cardio kill strength gains and muscle mass development?

The topic of compatibility of exercise training programs answers these questions. Hickson and other sport scientists conducted studies on concurrent training, or simultaneous training of both aerobic performance and strength development.  The results and applications are critical to athletes whose goals include strength and power development.

Research on Cardio vs Strength Training

If you look into studies that use high levels of training frequency and/or intensity for both endurance and strength, you find that:

  • Strength, power, high velocity muscle actions, and anaerobic performance can be compromised from endurance training.

But, 

  • Maximal oxygen consumption is not hurt when heavy resistance and aerobic training are performed together and
  • Endurance capabilities (time to exhaustion at submaximal intensities) are not affected by strength training.

So, a training program that includes both strength and aerobic training may limit strength gains, but improvements in cardiovascular fitness and performance are the same as if endurance training is performed alone.

Why does this happen?

It has to do with muscle fibers used for each type of training.  Muscle fibers have the dilemma of trying to adapt to aerobic function and at the same adding contractile proteins to build strength.  In summary:

  • When training to develop strength, all muscle fibers increase in size.
  • When only cardio work is performed, Type I fibers atrophy but no changes occur in Type II fibers.
  • With concurrent raining, no changes occur in the size of Type I fibers, but increases in size occur in Type II fibers.

The bottom line is that an athlete is not able to adapt optimally to both modes of training. 

Applications for Strength and Power Training

To answer the question of cardio vs strength, the total training program has to be designed around sport demands. To make sure that the volume of exercise is not counterproductive to optimal physiological adaptations for your sport, Kraemer et al. (2012) suggest these steps:

  1. Prioritize the goals of the training program and avoid performing high-intensity and high-volume strength and endurance training together.
  2. Allow for adequate recovery by using periodized programs.
  3. Strength and power athletes should limit high intensity aerobic work. Low intensity aerobic training is okay, but high oxidative stress negatively affects power development.

If you're interested in learning more about the effect of strength training on distance running, this Systematic Review of Resistance Training on Endurance explains.  This is just the abstract.  The full article is in the Journal of Strength and Conditioning Research.

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