Does cardio kill gains? There is a common belief in the fitness community that cardio inhibits “gains” or muscle growth, and research shows conflicting evidence in terms of the potential for resistance exercise or cardio to inhibit muscle adaptations brought about by training of resistance.
To help make sense of the research and science on the potential downsides of concurrent training: doing cardio and Weight training (opens in a new tab) together in a training session: We spoke with Heather Hart, ACSM-Certified Exercise Physiologist, RRCA-Certified Running Coach, and Co-Owner of Hart Strength and Endurance Training (opens in a new tab).
So whether you like to run, ride a bike, or use one of the best rowing machines (opens in a new tab) To get a good sweat, read on to learn how to maximize your results in the gym.
Does cardio inhibit muscle gains?
Hart says the evidence is mixed when it comes to whether or not cardio can impede muscular adaptations to weightlifting and other strength training.
“Numerous studies have shown that simultaneous training (cardio and strength training together) can result in decreased strength, power, and muscle hypertrophy, while other studies show that adding cardio to resistance training may not inhibit strength. or muscle gains,” says Hart.
For example, a recent review in Sports medicine (opens in a new tab) of studies examining the possible deleterious effects of concurrent training on muscle and strength adaptations concluded that concurrent training is only detrimental to explosive strength, but not to overall muscle hypertrophy or strength development.
And a 2018 review published in the Sports (opens in a new tab) Journal found that certain types of cardio exercise, such as HIIT, appear to show less or no negative effect on resistance training-induced muscular adaptations.
Why might cardio inhibit gains in muscle strength and size?
Hart explains the possible underlying mechanisms by which cardio can counteract some of your hard work in the gym. She says the first potential reason is that cardiovascular exercise can interfere with molecular pathways responsible for adaptations to strength training.
“Our bodies have two pathways for metabolism and cell growth when it comes to making adaptations to exercise: the mTOR pathway, which is typically activated during anaerobic exercise like resistance training, and the AMPK pathway, which is typically activated during aerobic exercise (cardio),” says Hart. “With concurrent training, the AMPK pathway can downregulate or inhibit the mTOR pathway. Downregulation of mTOR could inhibit protein synthesis, or the process by which our bodies build muscle.”
Hart says this means that combining aerobic or cardiovascular exercises and strength training in the same workout or close together can eventually lead to decreased returns from your resistance training, including inhibition of muscle hypertrophy.
“Another theory is that by combining cardio and resistance training, people become fatigued and deplete energy stores to the extent that they don’t lift weights at the same volume or frequency as they would if they just did resistance training; therefore, inhibiting their potential earnings”, syas Hart.
Essentially, if you’re trying to do too much in one training session or without adequate rest between workouts, especially if you’re not taking in enough calories, you won’t be able to put as much effort into your body and reap the same benefits. you would have been fresh and fully recovered.
“Prolonged cardio (longer than 90 minutes) significantly increases the likelihood that your body will start using protein as an energy source, which speeds up the breakdown of muscle protein,” says Hart. “While post-exercise muscle protein synthesis replenishes lost protein (in the presence of protein and/or amino acids consumed through food), this generally only returns muscle protein balance to neutral, rather than neutral. net positive”.
Translation: you’re not losing muscle mass, but you’re not gaining it either.
How to combine cardio and weights without sabotaging your progress
Hart says it’s possible to successfully combine cardio and weights without inhibiting your gains. Here are his top tips for concurrent training:
- Space your workouts: Instead of doing your cardio and resistance training back-to-back in one session, space them out by at least six hours, although 24 hours is ideal.
- Prioritize the type of exercise based on your goals: Hart says that when you need to do cardio and weights in the same workout, the order matters. “If increasing muscle strength or size is your priority, you’ll want to lift weights before completing your cardio,” she says. “If your goal is muscle hypertrophy, cardio should not exceed 90 minutes in a single session, as this is the point at which protein breakdown increases.”
- Correct fuel: Cardio can compromise muscle growth and strength gains if you’re not eating enough calories or getting the right nutrients. “Not only will you need to increase your caloric intake to provide enough energy to complete both workouts, but you’ll also need the additional ‘materials’ to help repair and build muscle,” says Hart. She adds: “For people who usually focus on strength training, this may mean consuming more carbohydrates to support additional cardio. For cardio fanatics like runners or cyclists, adding strength training may mean consuming more protein to support hypertrophy.”
Can fasted cardio inhibit muscle growth?
What about exercising on an empty stomach? it does fast (opens in a new tab) cardio affect muscle growth?
According to Hart, potentially. “Our body’s preferred source of energy during constant aerobic exercise is glycogen, or carbohydrates stored within our bodies,” she says. “When glycogen is low, our bodies are able to break down (muscle) protein into amino acids, which are then converted to glucose to provide energy, contributing more than 18% of energy requirements.”
She explains that protein synthesis, or the rebuilding, repair and growth of muscles, is inhibited during exercise but is elevated immediately after a workout. In most cases, by consuming protein after exercise, you can replenish the protein used during exercise. But this picture changes a bit during fasted cardio.
“Studies show that after fasted cardiovascular exercise, it becomes more difficult to replace the protein that was lost, as muscle protein breakdown is likely greater due to the fasted state,” says Hart. “For muscle hypertrophy to occur, muscle protein synthesis must exceed muscle protein breakdown. This cannot happen without sufficient food intake.”
Hart cites the AMPK metabolic pathway that is activated during states of energy depletion, such as steady-state cardiovascular exercise, particularly when performed in the fasted state. This could, in turn, downregulate the mTOR pathway and thus inhibit muscle growth.
This article is not intended to offer medical advice and readers should consult their physician or health care professional before adopting any diet or treatment.
Food to go
While it’s possible that cardio can inhibit gains in muscle strength, size, and power, Hart cautions against using fears of sabotaging progress lest it get in the way of maintaining your workouts.
“Both cardio and resistance training are essential and necessary for optimal health, and the health benefits they provide far outweigh any potential ‘negatives’ when it comes to your sport or your specific performance goal,” He says.
In other words, if doing cardio and weights back to back is all your schedule allows, go for it, especially if you don’t do it every time. Just be sure to eat right before, during, and after your workout, listen to your body, and do your main type of exercise first.
This article is not intended to offer medical advice and readers should consult their physician or health care professional before adopting any diet or treatment.
