Why You Should Not Train Strength & Cardio At The Same Time

Do you train for strength and cardio at the same time?

If you do, you may be making mistakes with your workouts that lead to poor training outcomes. Even though training for strength and cardio appears to achieve two goals at once, research shows that the body becomes confused by the multiple activation patterns, eradicating strength gains.

This is a concept known as the interference phenomenon, which means that adaptation mechanisms in the body compete and interfere with one another. The end result is poor performance and less than expected body composition outcomes.

In simple terms, athletes who lift weights and do aerobic exercise don’t see the strength, muscle and power gains they’d expect.

Typically, interference only goes one direction. That is, strength, muscle, and power are compromised by endurance exercise, but endurance performance is enhanced by strength and power training.

A recent review provides strategies to avoid making programming errors that will keep you from reaching your potential. Researchers analyzed all the previous studies that reviewed the effect of concurrent strength and conditioning training on strength, power, hypertrophy, endurance performance, and body fat. This is what they found:

#1: Concurrent training leads to reduced muscle and strength compared to strength training alone.

Strength and muscle mass gains are significantly compromised by concurrent training that combines endurance exercise with lifting. The magnitude is large and related to the intensity of endurance exercise.

Concurrent training reduces muscle mass the most when low-intensity exercise is performed more than 3 times a week for at least 20 minutes.

Very high-intensity training in the form of repeated sprints avoids this. It also has a positive effect on body composition, reducing body fat.

Take Away: To maximize muscle mass with concurrent training, choose high-intensity modes such as sprints or strongman exercise. Limit conditioning workouts to less than 3 days a week.

#2: Glycogen depletion and protein breakdown likely cause interference.

Logically, the adaptations of strength training and endurance exercise are vastly different and in many cases conflicting. For example, muscle adapts to each mode differently: Endurance exercise increases the body’s ability to use oxygen, whereas strength training increases protein synthesis in the muscle fiber.

In addition, gene signaling pathways are differently affected by each training mode. Strength training activates the mTor muscle building pathway, but this pathway is impaired when strength training is done after glycogen depleting exercise.

Separating strength training and conditioning workouts so as to allow for glycogen replenishment may reduce the negative effects. Strength capacity is impaired more in workouts that combine weight training and endurance exercise in the same session and the effect is greatest when strength training follows cardio.

Take Away

Try to schedule strength and conditioning on alternate days. Never do strength training after conditioning and avoid training them in the same session.

#3: Use cycle sprints instead of running sprints to reduce interference.

Strength training performed concurrently with running produces a greater decrease in muscle mass and strength than lifting in conjunction with cycling.

Researchers think this has to do with the fact that cycling is more biomechanically similar to the free weight exercises performed in most concurrent training programs.

In addition, running has an eccentric component, whereas cycling is principally a concentric exercise. Eccentric motions causes more muscle damage, which, when combined with weight training, may compromise strength and hypertrophy.

Take Away

If you’re training for strength and muscle but need conditioning, do cycle sprints or another concentric-only type of training, such as weighted sled sprints.

#4: Lose body fat with a combination of high-intensity sprints and weight training.

The most intriguing outcome is that the greatest fat loss occurs in response to high-intensity endurance exercise (such as sprint intervals) combined with weight training. Fat burning is maximized in response to low-intensity exercise but this doesn’t maximize fat burning and metabolic rate over the long term.

Rather, metabolic rate in the post-workout period increases exponentially with increasing intensity. Further, sprint interval-type exercise leads to increased activity of an enzyme that enhances the rate of fat burning.

Take Away

Do concurrent training that combines sprint workouts and weight training performed on separate days (to ensure recovery) to reduce body fat.

#5: Power is compromised the most by concurrent training—much more than strength or hypertrophy is.

The performance factor that suffers the most from concurrent training is power output—the ability to generate force quickly.

The drop in power output corresponds to the length of the endurance exercise. Lower intensity conditioning leads to a much greater loss of power. Because force at high velocities is negatively affected by concurrent training more than force at low velocities, researchers suggest power is compromised either due to impairments in velocity or rate of force development.

Take Away

Pure power athletes such as throwers or baseball players should avoid concurrent training entirely. Power athletes who require conditioning should stick to very high-intensity, short duration intervals such as the 6 to 10 repeats of 35-meter all-out cycle sprints with 10-seconds rest.

#6: Anaerobic training modes such as sprint intervals and weight lifting will benefit endurance athletes.

Performing strength training won’t compromise endurance performance or affect maximal oxygen uptake (VO2 Max). It also won’t result in significant or even measurable hypertrophy if it is done in conjunction with regular endurance training. Instead, the proportion of type 2A muscle fibers increases, allowing for a faster rate of force development.

A strength-type resistance training program with loads of 80 percent of the 1RM or heavier and a relatively low volume is indicated by the research in order to increase short- and long-term endurance capacity.

Take Away

Improve endurance by training a strength-type, heavy, lower volume weight program to increase speed and work capacity. You won’t gain muscle or increase body weight but performance will improve.

#7: Concurrent training negatively affects hormone levels, compromising performance.

We’ve known for some time that high-volume endurance exercise leads to chronic reductions in androgen hormones such as testosterone. On the other hand strength training leads to no change or a slight increase in testosterone.

It’s only recently that a study compared the effect of endurance alone, strength alone, and concurrent training on hormone levels in wrestlers. Results showed that testosterone levels decreased in both the concurrent and endurance groups—by 30 percent in the endurance-only group and by 41 percent in the concurrent training group. In the strength-only group testosterone increased slightly by the end of the study.

Another negative effect of chronic endurance exercise is that it elevates the stress hormone cortisol, whereas when strength training is performed alone it may be protective against stress. Anaerobic forms of exercise may reset the hypothalamic pituitary axis so that it becomes more responsive and cortisol balance improves.

Take Away

Endurance athletes will benefit from strength training because it offsets the catabolic nature of endurance exercise. Strength and power athletes should favor anaerobic conditioning and be mindful of the need for proper recovery and stress reduction.

Final Words

In a review of the appropriateness of aerobic exercise for anaerobic athletes, sports scientist Charles Pfeiffer says it best: “The consequences of aerobic exercise are too detrimental to be considered an effective training modality for anaerobic athletes; let alone a necessary one.”

For the general public, anaerobic training is also preferable for achieving body composition changes and overall health. Power and functional ability are maximized with anaerobic training and it is ideal for older individuals who need to maintain bone and muscle as they age.