Over the decades many coaches and trainers have recommended against doing cardio and weightlifting in the same workout.
This is because of the “Interference Effect”.
These two types of training benefit the body in entirely different ways.
- Resistance Training builds myofibrils – increasing strength, power, and hypertrophy.
- Cardio Training builds mitochondria – increasing endurance and VO2 max.
One type of training builds myofibrils and one builds mitochondria.
Doing both types of training in the same workout, called concurrent training, can cause conflict since the adaptations are different.
Is this true 100% of the time?
I’ll discuss after a short music break.
The music theme for this article?
Solo artists performing hits from bands they were part of after their bands broke up.
(Susanna Hoffs “The Bangles”. Pretty much every guy in Generation X had a huge crush on her. Who am I kidding? We all STILL have a crush on Susanna.)
The most comprehensive research is from 2011 and it examines 21 studies on concurrent training called:
Concurrent Training: A Meta-analysis Examining Interference of Aerobic and Resistance Exercises.
Here are some of my main takeaways.
Resistance Training Alone is Best for Getting Bigger and Stronger Legs
If you follow your leg workout with cardio, your legs won’t gain strength and size as much as if you did weight training alone.
I’m fine with maintaining leg strength.
I do think strong legs are good to a certain point…
…but I also believe that pushing too hard on lower body lifts can destroy the spine
Ronnie Coleman, one of the most successful bodybuilders of all-time, can’t walk on his own anymore.
Yes, he is an extreme example.
I believe that anyone testing their limits in squats or deadlifts for 20+ years is risking long-term pain.
You only get one spine.
The temptation is strong to always beat your personal best in a lift.
I call this the dark side of weight training…
This is when you are constantly aiming for larger numbers instead of lifting in a way that makes you look and feel healthier.
(David Byrne “Talking Heads”. The story he talks about in the beginning makes the lyrics to this song hilarious.)
Here’s an interesting finding.
Cardio after resistance training doesn’t affect upper body strength and size.
This is dose-dependent.
If large amounts of cardio are added it can have a small effect on upper body strength and size.
Cardio mainly just interferes with the lower body.
Running is the type of cardio that interferes with lower body strength and size the most.
The research found running had a negative effect on gaining size in the lower body.
This can be either a good or bad thing depending on your goals.
I got my start in fitness by training fashion models (both men and women).
Many of them wanted to lose a little bit of muscle mass in their lower body in order for clothes to fit better.
(Johnny Marr “The Smiths”. He wasn’t even the main singer, but his magical guitar playing made that band. Considered one of the best ever.)
For those with bulky legs, I coached them to perform “marathon cardio”…
Running at a medium to fast pace for 30-60 minutes on a treadmill.
This works well and it is cool that the study backs this method I’ve been using all of these years.
In fashion, being slim is the top priority.
I’m not saying that everyone should be as slim as possible.
Some people look great with a decent amount of muscle.
…but if your lower body is bulkier than you would like, add in 30-60 minutes of running after your weight training session.
It’s nice to have this knowledge.
Legs feel bulky?
Focus on jogging on a treadmill for a few months.
Legs looking skinny?
Focus on HIIT on a stationary bike for a few months.
(David Gilmour “Pink Floyd”. You don’t even have to be high to like this one… although a large portion of the fans in the crowd typically are.)
My bonus tip?
I feel that the StepMill maintains leg size and definition while making the butt look great.
For more butt knowledge read my article about Dead Butt Syndrome.
D.B.S is a sad condition that is sweeping the nation.
Concurrent training has a greater fat loss effect than strength training or cardio alone.
Resistance training alone helps you lose fat.
Cardio alone helps you lose fat.
When you combine the two you get a synergistic effect.
(Noel Gallagher “Oasis”. This song came out over 20 years ago and I never get tired of it.)
Here’s a study with a surprising finding:
Concurrent Resistance and Aerobic Exercise Stimulates Both Myofibrillar and Mitochondrial Protein Synthesis in Sedentary Middle-aged Men
This one compared three different workouts.
- 1 hour of Resistance Exercise
- 1 hour of Aerobic Exercise
- 30 minutes of Resistance Exercise followed by 30 minutes of Aerobic Exercise.
The combined workout had the same aerobic capacity adaptation as 1 hour of aerobic exercise alone.
30 minutes of cardio had the same VO2 max benefits as 1 hour of cardio, just as long as it was combined with 30 minutes of resistance training.
So probably no reason to cardio alone.
A quick summary.
It makes sense follow your strength training routine with a bit of cardio if fat loss is your goal.
The only exception?
If you are trying to gain as much strength and size on your lower body.
If you are actually trying to lose a bit of size on your lower body run for 30-60 minutes after lifting.
As a former fitness coach to fashion models, I can teach you how to increase muscle definition without adding size.
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