Three Science-Based Cardio Mistakes that are Undermining your Muscle Gains.

Jul 11

5 min read

Can Cardio Hurt Muscle Building?

The answer depends on how you approach cardio. Performed correctly, cardio offers numerous health benefits and can even aid in fat loss, potentially complementing muscle growth. However, improper cardio integration can negatively impact your gains.

The Importance of Proper Integration

A 2012 study (1) revealed that poorly combining cardio and weight training can significantly hinder muscle growth (by about 31%) and strength gains (by roughly 18%).

This might lead you to believe that eliminating cardio altogether is the key to maximizing muscle building. However, the focus should be on how you integrate cardio into your routine, not whether you include it at all.

As long as you consume an adequate amount of calories and protein, cardio won't readily deplete muscle tissue. However, there are three common cardio mistakes that can sabotage your muscle-building efforts:

Mistake #1: Cardio Timing

Many people find it convenient to do cardio during their weightlifting sessions. If you choose this approach, prioritize weights first, followed by cardio. A 2016 study (2) demonstrated that participants performing 20 minutes of cardio before lifting weights experienced a significant decline in workout performance.

The study involved five resistance exercises (high pull, squat, bench press, deadlift, and push press) performed for three sets of 6-10 repetitions at 70-80% of their one-rep max (1RM). Compared to those who didn't do pre-workout cardio, participants who did cardio beforehand completed an average of 9.1-18.6% fewer reps. Additionally, average power and velocity per set were significantly lower for specific exercises (high pull, squat, bench press). Similar results have been observed in other studies (3, 4).

Pre-workout cardio can leave you fatigued, hindering your lifting performance and potentially slowing down your long-term progress. If your primary goal is to improve cardio performance, doing cardio before weights might be sensible.

The Best Time for Cardio

For moderate- to high-intensity cardio sessions (lasting longer than 30 minutes), it's best to separate them from your weightlifting workouts. A 2017 study (5) published in the Journal of Sports Science Medicine found that untrained lifters who performed a 30-minute moderate-intensity cycling session 24 hours after a bicep workout, as opposed to immediately after, experienced almost double the muscle hypertrophy.

The researchers suggest that systemic factors interfering with muscle hypertrophy might be at play when cardio is done right after a workout that induces muscle damage. This study suggests separating cardio and weight training might be more optimal for muscle growth. However, it's important to note that these results may not apply to shorter or less intense forms of cardio.

How Long to Wait After Lifting for Cardio?

Research (6) generally recommends waiting at least 6 hours between lifting weights and doing cardio. This means you could lift weights in the morning and do cardio at night, or vice versa. Alternatively, you could schedule your cardio session for the following day.

Cardio and Lifting Performance

A study (7) conducted at the University of Sao Paulo investigated how cardio affects lifting performance. Ten men were divided into three groups:

Group 1: Performed four sets of half squats for as many reps as possible with 80% of their 1RM.
Group 2: Did 30 minutes of high-intensity interval training (HIIT) cycling, followed by a leg workout.
Group 3: Did 30 minutes of HIIT running, followed by the same leg workout.

The researchers compared the total amount of weight lifted and reps performed across all three groups. Group 1, which didn't do cardio beforehand, unsurprisingly performed more total reps and lifted significantly more weight.

While this study doesn't directly address muscle hypertrophy, progressive overload is a key driver of muscle growth. Based on this, it's likely that Group 1 would experience greater gains over time.

Mistake #2: Choosing the Wrong Type of Cardio

Running is a popular form of cardio, but it might not be the best choice for muscle building. Running, along with other high-impact activities like jump rope and sprints, involve significant eccentric muscle contractions, which can cause substantial lower body muscle damage and require extended recovery time.

If your body is focused on recovering from high-impact cardio workouts, it can negatively impact your weightlifting performance, especially leg workouts.

The Best Cardio for Lifters

Lower-impact cardio is generally better suited for lifters because it requires less recovery time, minimising interference with weightlifting performance. This type of cardio allows you to achieve your physique goals without sacrificing your performance in the gym.

The Previously Mentioned Meta-Analysis (1) also revealed that cycling, when done concurrently with weight training, resulted in a significantly smaller decrease in lower body muscle growth compared to running.

Therefore, to minimise the negative impact of cardio on your gains, focus on lower-impact exercises with minimal eccentric components. Here are some examples of good choices:

Cycling
Elliptical trainer
Incline walking

While high-impact cardio isn't inherently bad, and you can certainly enjoy it if you prefer it, be mindful of how it affects your recovery.

Mistake #3: Doing Too Much Cardio

A common misconception is that more cardio equates to more fat loss. While cardio does burn calories, it's not necessarily the best approach for fat loss. You can achieve a very low body fat percentage without doing any cardio at all. However, if you consume too many calories, regardless of your cardio level, you won't lose fat.

The key lies in moderation. Drastically increasing your cardio volume for fat loss isn't sustainable for most lifters. Ideally, you want to maintain or even build muscle while losing fat. This means prioritising your weight training as if you were bulking muscle.

Adding some moderate cardio can allow you to eat slightly more, burn some extra calories, and potentially manage hunger, but it shouldn't be the primary driver of your fat loss. Focus on dietary adjustments for significant changes during a cutting phase.

Optimal Amount of Cardio

A 2013 meta-analysis of 21 studies (1) confirmed that more frequent and longer cardio sessions can hinder muscle and strength gains. This research suggests that cardio sessions exceeding three times per week and lasting longer than 20-30 minutes each might not be ideal. However, this is a general guideline, and the optimal amount of cardio for you will depend on your individual response.

Importantly, the study also showed that muscle gains were still possible even with the introduction of cardio. Therefore, incorporating moderate cardio into your routine likely won't significantly harm your progress if you follow a proper diet and weight training program.

In fact, when I work with clients who are cutting, I sometimes exceed the recommendations above to maximise fat loss while preserving muscle mass. However, if building muscle and strength is your primary goal, be aware that excessive cardio can hinder your progress.

Keep it Simple

In moderation, cardio likely won't burn muscle. However, excessive cardio can hinder your muscle growth potential.

Here's a summary of key takeaways for optimal muscle building while incorporating cardio:

Perform cardio after weightlifting, ideally at least 6 hours later.
Prioritize low-impact cardio like cycling, elliptical training, or incline walking to minimise recovery time and preserve energy for lifting.
Focus on weight training as the foundation of your routine.
Limit cardio to 2-3 sessions per week, lasting 20-30 minutes each, if your main goal is muscle and strength gains.