Strength & Cardio: Which Should I Do First?

As a trainer, one of the most common questions I get surrounds the order of exercises. There is a lot of competing information out there, with plenty of experts (and laymen!) who will champion Cardio First, Strength First, or sometimes Donuts First! (I hope I made that last one up.) Today lets talk about the four major factors which you should be considering when deciding what order is right for you.

What’s the best use of your Energy?

This is the most common area where I see people differing in regards to exercise order. Common theories state that the aerobic energy system, which is primarily responsible for fueling your cardio sessions, only kicks in after using up all of your short term “burst” energy. While it’s true that the body does move through the energy systems step by step, what is usually glossed over is the amount of time it takes to recover the used energy. Lets take a brief look at the three systems and a few key details.

System Step 1: Phosphagen Step 2: Glycolysis Step 3: Aerobic
Type Short-term, burst energy system used to fuel your heavy lifts. Medium-term, sprint energy system used to fuel your interval training (Tabata, HIIT) Endurance energy system used to fuel your longer term cardio (5k, etc)
Output Very Fast Production, Very High Power Fast Production, High Power Very fast production, high energy, low power
Fatigue Tires quickly; good for ~10 seconds of all-out effort Tires fairly quickly; good for 30-120 seconds of all-out effort Tires moderately slowly; can be trained at intervals of 5 to 60+ minutes
Recovery Typically 3-5 minutes Rest twice as long as you worked (2:1 rest to work ratio) Aim for a 1:1 ratio of “work” to “rest’ time

Your heavy lifting (i.e. Strength work) uses the Phosphagen system, because you only need a few seconds of strong power output to lift the bar 1-5 times.It is generally recommended that during a strength workout, you allow 3 minutes or more of recovery time for a given muscle group between sets. It’s no coincidence that this matches up to the Phosphagen recovery window.

When most people say “cardio”, they’re talking about longer distance/time running, cycling, etc., and those activities are fueled by the Aerobic system. Normally you have a one to one work/rest ratio, meaning it takes about as much resting time as it does working time to make up the energy used. Keep in mind that this doesn’t mean you can’t continue with your cardio work, because your body can produce a ton of energy from what you’ve got stored away. Unless you’re running a marathon (or equivalent), you don’t typically need to worry about rest periods here. Your body will recover fine.

So, if we just base our decision on the energy systems being used, which order is best? Assuming that your nutrition is on par, the answer is that it doesn’t really matter!

The main goal here is to manage your Time (how long it takes you to complete something) and Timing (how you string different movements together). A solid strength session can take 15-60 minutes and a good cardio workout can take about the same. You should be giving yourself 10-15 minutes of active rest (i.e. stretching, light yoga, a little walking, etc.) between the two, to ensure that your shorter term systems are recovered enough to move on. The longer term Aerobic system will be fine regardless of order, because it only gets put into play when we actually do longer term work.

What are your Goals?

Even though your energy systems might technically work the same regardless of order, there is a psychological advantage to exercising in a different order. Here we need to make a distinction between what your body can actually do (your capacity) and what your mind/emotions tell you is your limit (how you feel). Typically, you will be able to coax yourself into exerting more effort when you feel less tired. A general feeling of fatigue can induce less work even when capacity remains undiminished. Because this happens, it becomes important to know what your goals are for exercising.

If you want to focus more on gaining strength, power, and muscle then you should be putting your strength work first. You will be working in a fresher state of mind, which will give you a mental edge to push harder. Likewise, if you want to focus more on cardiovascular development and fat loss, then you should put cardio at the beginning for the same reason. Managing your psychological state during a workout is just as important as managing your physical state.

But what if you want to build both strength and cardio? Alternate! If you workout 6 days a week on a split routine, with some kind of complementary cardio each day, start alternating which comes first. Lets say you do the following basic routine each week:

  • Mon/Wed/Fri (MWF): Legs, Back, Swimming
  • Tue/Thu/Sat (TRS): Chest, Abs, Running
  • Sun: Rest

Over the course of a month, you can alternate your cardio and strength like this:

  • Week 1: Cardio > Strength (MWF) and Strength > Cardio (TRS)
  • Week 2: Strength > Cardio (MWF) and Cardio > Strength (TRS)
  • Week 3: Cardio > Strength (MTW) and Strength > Cardio (TFS)
  • Week 4:  Strength > Cardio (MTW) and Cardio > Strength (TFS)

Change up your splits periodically, and cycle routine order to best adapt to an overall goal of general fitness.

Where do you get the most Enjoyment?

This one is similar to the question of Goals, but has the reverse effect. You will put in more effort on the things you like versus the things you don’t like, even if your capacity is the same. The danger here is that people tend to do what they like first, giving a lot of effort and causing feelings of fatigue to set in, and then when they move on to the things they don’t like, they get a double whammy of “I don’t want to do this” and “I’m too tired to work as hard as I could otherwise”.

My advice here is to put the thing you don’t like first in your workout. If you hate to run, and it’s a running day, then run before you lift. Tell yourself that giving full effort on the thing you don’t like is rewarded by doing the things you do like. Said another way, you want to positively reinforce yourself for working on skills you need to improve but don’t necessarily enjoy. This tends to have two interesting side effects, other than being able to do more work.

First, you start to associate an exercise you don’t like (e.g. running) with positive feelings of accomplishment. The human brain is wired to like being positively reinforced and you benefit from basic conditioning. You may never come to love running, but you will dislike it less.

Second, practicing a skill makes you better at that skill, even if you don’t like doing it. When you become good at something, you are more inclined to practice it, which then makes you better at it yet again.

Think of these two things as “The Gains Loop”, where doing it makes you like it a little more because you associate with something you like AND makes you more likely to do it because you’re getting better at it.

What gets you Results?

Everyone’s body is different. We can give lots of general advice about how your physiology theoretically functions, but a lot of factors can jump in at any time. Things like sleep, nutrition, injury, current fitness level, personal history, genetic differences, and many others can affect how you physically, mentally, and emotionally react to different exercise routines. You need to be listening to your body to determine what split works the best for you, taking your preference and goals into account. What this point really boils down to is: listen to your body and adjust accordingly.

Some examples:

  • If you are consistently unable to make progress on your strength work when you do cardio first, then switch the order and see what happens.
  • If you always get migraines when you run and do heavy leg work on the same day, don’t pair those two things in that order.
  • If you always strain your hamstring when mixing box jumps (explosive power) with swimming no matter the order, then don’t pair them at all.

Be on the watch for these kinds of situations. You can make this sort of adjustment easier by taking notes on every workout, including what you did (moves, reps, sets, times) as well as how you felt (great, strong/weak on certain moves, sick to your stomach, etc.). Once you know your body, everything becomes easier.