Concurrent training is inclusion of both resistance and endurance training within the same training program. For example, if you lift weights on Monday and run a few miles on Tuesday, then repeat this pattern throughout the week or in the same day, you are training concurrently. This can be advantageous for reducing body fat compared to resistance or endurance training alone, as strength training typically does not yield decrements in body fat, and endurance training reduces lean body mass, strength, and power in trained individuals. However, concurrent training does not produce as great of an increase in muscle mass or strength as resistance training alone, nor does it produce as great of a loss of body fat as endurance training alone.
Progress may be halted by the large volume of work necessary to perform both modalities simultaneously by pushing the athlete into an overreached or overtrained status. However, those accustomed to higher workloads should be able to handle high volume. Therefore, it is more likely that stalled progress is due to competing adaptations. Wherein, resistance training adaptations (i.e. increased muscle mass, strength, power, and maintained oxygen consumption) compete with endurance training adaptations (i.e. reduced muscle mass, strength, power, and increased oxygen consumption). Much of this difference can be attributed to muscle size. It is advantageous for strength and power athletes to have large muscles, as larger muscles have higher force output, yet they also increase the diffusion distance for oxygen, making it more difficult for the mitochondria to receive oxygen to produce ATP (energy). Thus, it is beneficial for endurance athletes to have smaller muscles to oxygenate, and the longer duration you perform steady state cardio, the more muscle and strength you lose! Reduced muscle also reduces basal metabolic rate, making long term fat loss more difficult. At this point, you might be wondering, “what the hell do I do then? Concurrent training is bogus!”
For primarily anaerobic athletes such as football players, or those who just want to be huge and ripped, it is not worthwhile to perform much steady state cardio for the reasons listed above. Instead, cardiovascular activity for these sports should be primarily of very high intensity (90-100+ %) and short duration (10-30 sec) with fairly long rest periods (2-4 min). This type of cardio (also known as HIIT, or high intensity interval training) will impede resistance training adaptations less than steady state cardio. Of course, these athletes should weight train often, 3-7 days/week depending on training status.
For anaerobic and aerobic athletes such as basketball or soccer players who are active for a long duration, but also intermittently sprint, limited steady state cardio can be helpful. Although keep in mind that it will blunt increases in power from resistance training – don’t overdo it; once per week is sufficient for most individuals. The cardio train doesn’t stop there. Perform HIIT 2-5 days/week in addition to the steady state cardio depending on your sport and training status… then run through people like a train (this requires 3-5 days/week of resistance training).
For purely aerobic athletes such as marathoners, concurrent training is highly preferred! Rejoice! However, long duration steady state cardio should still only be performed once or twice per week with a focus on technique. HIIT, and other forms of higher intensity training such as fartlek and pace training, alone is very capable of increasing endurance, not only via increased oxygen consumption, but increased lactate threshold and/or lactate clearance. The maximal lactate steady state (MLSS) is arguably more important than maximal oxygen consumption for endurance athletes. MLSS can also be positively influenced by resistance training. Moreover, resistance training increases muscular tone. Increased muscular tone, when running, reduces energy lost to “rebounding” off the pavement, for example. In lax muscles, energy is required to absorb the force of contact with each step, yet tense muscles will absorb the force without expending as much energy. Weight training will also not blunt endurance adaptations if performed at a high intensity with low volume (i.e. without inducing muscle growth).
In summary, concurrent training reduces increases in strength, power, and muscle associated with resistance training. On the flip side, it enhances strength, power, muscle, and basal metabolic rate for endurance training alone. HIIT is recommended to reap the benefits of concurrent training without the drawbacks associated with steady state cardio.
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