One of the most common questions personal trainers get is, “Should I do cardio before or after weights?”

While the long answer is “it depends on, ”, most people will be better off completing cardio after weights whether their primary goal is muscle gain, strength gain, or fat loss.


7 Reasons To Do Cardio After Weights:


  1. Increased Energy For Lifting Weights

During exercise, the body uses stored energy in our muscles called glycogen. If glycogen levels are low, it affects our energy levels for workouts. For example, if you’ve ever gone on a low carb diet and experienced less energy during workouts, then you know what it feels like to have low glycogen levels. The same phenomenon happens if you do cardio before strength training – you use up your body’s preferred energy source for intense exercise. If you use up that energy, it won’t be available when you need to lift heavy weights, making a goal of building muscle, increasing strength, or maximizing calorie burn through weight lifting compromised.


  1. Favorable Changes in Blood PH

Completing cardio can make your blood more acidic. As you exercise, energy gets broken down and utilized to make lactic acid. Although lactic acid helps to replenish your fuel sources for continued exercise, it does so by creating excessive hydrogen ions. These hydrogen ions need to be buffered, which your body handles at an ineffective rate, lowering your pH (which makes your blood plasma more acidic). This acidic environment causes muscular fatigue and performance drops. So besides using the energy you need for heavy resistance training, doing cardio first also makes it harder for you to contract the muscles.


  1. Favorable Hormonal Changes

By completing cardio first, cortisol is released without a concurrent increase in testosterone. Cortisol breaks down muscle in order to give your body the continued energy to workout. This works fine when doing cardiovascular exercises and happens extensively in long duration cardio (think marathons), but is detrimental to building muscle if there’s not a concurrent increase in testosterone. For example, when you’re strength training, cortisol levels will go up but so will testosterone levels. This hormonal shift not only allows you to have energy for the workout but also helps to rebuild muscle after the session. Without these changes in hormonal profiles, it becomes much harder to gain muscle.


  1. Clear mTOR Pathways

Another nail in the coffin for doing cardio before strength training is the inhibition of the mTOR pathways. Many people have not heard of the mTOR pathway, but in essence, this is the pathway that tells your muscles to grow. In fact, one of the biggest genetic differences between those that gain muscle easily and those that really struggle to gain muscle size is due to the differences in expression for the mTOR pathway. In other words, “genetic freaks” have easy access to this pathway, whereas “hard gainers” don’t. When you do cardio with strength training and especially before strength training, this muscle building pathway becomes inhibited, making an already difficult situation that much harder.


  1. Greater Afterburn Effect

The workout that causes the largest afterburn effect will be the most effective for fat loss because you will

not only burn calories during your workout but also for up to 48 hours afterward. While the research is inconclusive (some studies show the afterburn effect to be greater with cardio before weights), an intense metabolic resistance training workout can create a very large afterburn effect and increase your cardiovascular health. A traditional bodybuilding workout, on the other hand, will not create a very significant afterburn effect so in that case, cardio before lifting may make sense from a fat loss perspective.


  1. Exercise Feels Harder Doing Cardio First

The “perceived exertion” rates (how hard exercise feels) is higher when you do cardio before strength training – even if the results you get from both routines are the same. This simply means that if you do the same routine, but do cardio first, it will feel much harder than if you did the same exact workout by doing the strength portion first. In other words, all of those reasons listed above truly do make your workouts feel harder. The sad part is that this method is not more effective for fat loss or muscle gain than if you simply did the strength first.


  1. Less Risk of Injury Due to Fatigue

If you try maxing out on squats after an intense cardio session, you may be mentally and physically fatigued, which increases the chance of injury. Besides needing the mental fortitude to put a heavy weight on your back after cardio, you will also need the help of a number of smaller “assistance muscles” to help with the movement. These may have become fatigued from the cardio beforehand. By tiring these stabilizer and assistance muscles before performing heavy strength training, you risk the chance of completing an exercise incorrectly or with improper form.


Why Not Combine Cardio and Weights?

If you’re truly pressed for time, you can combine strength and cardio movements. An example would be to complete two strength training exercises – think lunges and cable rows – followed by bike sprints for 30 seconds. By combining the strength and cardio portion, you are satisfying the need to create damage to the muscle, keep your heart rate high throughout the session and have more spikes to your heart rate creating a greater oxygen debt.


The Wrap Up

While there are several benefits for lifting weights before cardio, at the end of the day, the best fat loss plan is the one you will stick to and that continues to produce results. If you enjoy completing cardio first, then, by all means, go for it! I would caution using the “weights after cardio” approach, however, if your main goal is building muscle.