What is your goal? Is it to increase your endurance or build muscle? This will determine which is more important. The first thing you need to realize is they are conflicting signals. If you do too much weight lifting but you are trying to become a long distance runner, it is going to hinder your aerobic capacity. If you are trying to get stronger and build muscle, doing too much cardio is going to hinder the maximum amount of muscle you can gain.
Cardio
Cardio is the easiest form of exercise to jump into. It requires nothing other than maybe a pair of shoes and the open road. It’ll strengthen your heart, improve your stamina, and increase your lung capacity. Within a given session, cardio will burn the most calories. There are also different types of cardio you can choose.
NEAT - Non-Exercise Activity Thermogenesis, is basically all the extra movement you do throughout the day beyond what keeps you alive. Any time you fidget, and get up and move that is your NEAT. For most of my clients I will always start by increasing their NEAT.
It’s not as intense as HIIT or steady state cardio, but it's the most sustainable. If you are someone trying to lose weight, increasing cardio will only last so long. The problem most clients have isn’t losing weight, but keeping it off 6-12 months after. The main reason being is the client never learned what it actually takes to lose weight and keep it off. They chose or were given short term solutions to burn the most calories and eat the least amount within a short time frame. No one can keep that up. What instead happens is, clients add more and more cardio running themselves into the ground. Your body gets more and more efficient at burning less calories the longer you do cardio. This is why months into a diet, you’ll find yourself doing the same amount of running, yet no change on the scale. You have to keep producing more and more effort to get the same caloric burn. Inevitably you’ll give up and stop doing cardio altogether and put the weight back on.
By focusing on NEAT, now you are slowly introducing more movement into your day as part of your routine vs. a specific time allotted to the gym. By adding 3,000 or so steps on top of what you are doing, you can now look for ways to incorporate more movement throughout the day. This can be in the form of playing with your kids, or walking for 10 minutes after each meal. Clients find this WAY easier to adhere to in the long run.
HIIT - High Intensity Interval Training is a 15-20 minute cardio session including a series of 10-30 second all out sprints. It’s a much shorter session than steady state cardio yet burns the same amount of calories due to the intensity. This will work better in terms of preserving muscle as the power to do the sprints requires more muscle than a jog. The caveat I will say is, once again, don’t risk doing too much. If you are doing more than 2-3 days of HIIT a week, you are going overkill. More is not better. Anything past 3 days, I would suggest switching to adding more NEAT.
Steady State Cardio - Bodybuilders used this as a low intensity way to get their extra caloric burn in while also preserving muscle because it is so low intensity. This is fine, and somewhat similar to NEAT, but a little more directed in terms of a specific amount of time allotted on a treadmill or cardio device. Unless building endurance is your goal, once again I wouldn’t go past 2-3 days.
Weightlifting Builds Your Metabolism
When it comes to weightlifting you don’t burn as many calories in a given session, but the more muscle you put on, the more calories you burn at rest. Muscle is calorically expensive to have, so it requires more calories to keep it on your frame. So unlike cardio, which burns muscle the more you do it, weightlifting adds more muscle. You don’t need to be a bodybuilder’s size to need to do weightlifting. 2-3 days is how often I’d recommend for everyone ideally.
Resistance training goes far beyond just adding muscle. It prevents injury, and it increases bone density. These are two things you absolutely don’t want to lose the older you get, yet so many people fall victim to it because they prioritize cardio over weight lifting. Aiming to do 5lbs more or one rep more than the week before, allows you to provide a muscle building stimulus that tells your body to keep what muscle you do have (during a diet), or grow more muscle (when eating in a surplus).
Check out my article on 3 Basic Tips for Someone Who Hasn’t Lifted Weights Before.
BOTH are Important
At the end of the day people should be incorporating both. I like to tell my clients to first start with 2-3 full body days in the gym. This allows you to frequently hit the muscles and optimize the muscle building signal. If you would like to add cardio to increase your cardiovascular health, start with increasing your step count by 3,000. Do it through daily activities so that you can find ways to sustain that movement. In order to keep the body you strive for, you need to adopt new habits to maintain it.
If you are dieting, you may have to keep increasing your NEAT to see the scale go down. Add more as necessary and if you hit a point you can’t hit your goal through daily movement, only THEN should you start to add steady state or HIIT cardio. By following it this way, you learn to see cardio as a tool towards achieving a lifestyle rather than a quick fix.
Be sure to check out my article What are the Best Exercises for Men Who Want to Pack on Muscle and Weight Training for Beginners - Start With Full Body.
