The order in which you do cardio and weights isn’t random: if you want more strength, do weights first; if you want more endurance, do cardio first. If you want general fitness, separating them is (almost) always the best choice.
- Why does it matter? Training strength and endurance together creates an “interference effect”: the body receives conflicting signals and doesn’t know whether to adapt for strength or for endurance.
- Goal: STRENGTH / MUSCLE: Do WEIGHTS FIRST. You need 100% of your energy and glycogen stores to lift heavy loads. Doing cardio first “empties the tank” a bit.
- Goal: ENDURANCE (Running): Do CARDIO FIRST. You need fresh legs to run with the right technique. Lifting weights first would fatigue you, worsening the quality of your run.
- Goal: WEIGHT LOSS / FITNESS: The order is less crucial, but starting with WEIGHTS is often more effective. You burn sugars with strength training and then use cardio to “attack” fat stores.
- The Ideal Solution: If you can, SEPARATE the workouts. Do weights in the morning and cardio in the evening, or (even better) on completely different days.
The Eternal Gym Dilemma: Cardio Before or After Weights?
It’s the million-dollar question. You walk into the gym; you have one hour. Your plan says “30 min treadmill” and “30 min weight circuit.” Where do you start?
There are those who jump on the treadmill “to warm up” and end up working way too hard, arriving at the weights with no energy left. There are those who do weights, feel tired, and “skip” cardio because “hey, I already worked hard.” And there are those who do 10 minutes of one, 10 of the other, in a confusing loop, alternating everything.
The truth is that the order in which you do things isn’t a personal preference: it’s a choice that can influence your results.
The Science of the “Interference Effect”: Why Order Matters
To understand the answer, you first have to understand the problem. The problem is called the “interference effect” (or concurrent training).
Pensa al tuo corpo come a un operaio incredibilmente specializzato. When you lift a heavy weight, you’re telling it, “Danger! You need to build bigger, stronger muscles to survive next time!” (strength/hypertrophy adaptation).
When you run for a long time, you’re telling it, “Danger! We have to escape a predator for miles! You need to become more efficient, build more capillaries and mitochondria, and get lighter!” (endurance adaptation).
What happens when you give it both messages at the exact same time? The specialized worker gets confused.
The body doesn’t know whether it should build up or lighten up. The molecular signals for muscle growth (mTOR) and those for endurance (AMPK) conflict. The result non is that you get 50% of both; it’s that, very often, you get less of both.
The order, therefore, serves to tell your body which message is today’s priority.
The Right Answer Depends on Your Goal
Stop asking “what’s the right order?” Instead, ask “what is my goal?”
Goal #1: Do You Want to Increase Strength and Muscle Mass?
The answer is: WEIGHTS FIRST, ALWAYS.
This is the most non-negotiable rule of all. To lift a heavy load, to stimulate muscle growth, you need two things: maximum neural focus and maximum fuel (glycogen) in your muscles.
If you run for 30 minutes before doing squats, you’re “emptying the tank.” You’ll get under the barbell already tired, with less explosive energy and less strength. You’ll lift less, stimulate the muscles less, and increase your risk of injury because your form will break down.
Cardio? Do it after, and keep it light (in Zone 2). Or, as we’ll see, don’t do it at all that day.
Goal #2: Do You Want to Improve Endurance?
The answer is: CARDIO FIRST.
If your main goal is to become a better runner, to prepare for a 10k or a half marathon, the quality of your run is the priority.
If you do a heavy leg workout (squats, lunges) before getting on the treadmill for repeats, your legs will already be fatigued. Your running technique will be terrible, your pace slower, and your perceived effort through the roof. You’re training your body to run poorly.
Do your running session (especially if it’s a quality workout) fresh. If you have to do strength work, do it afterward, and maybe focus on your upper body or core exercises, which interfere less.
Goal #3: Do You Want to Lose Weight or Improve General Fitness?
The answer is: THE ORDER MATTERS LESS, BUT STARTING WITH WEIGHTS IS MORE STRATEGIC.
Here, the goal is to maximize total calorie burn and improve body composition. The order is less rigid, but there is a winning strategy:
Do STRENGTH first and CARDIO after.
Why? Strength training (like a metabolic circuit or weightlifting) primarily uses the glycogen (sugar) stores in your muscles. By doing it first, you “empty” that tank.
When you then move on to cardio (e.g., 20-30 minutes of slow, steady running), your body, having fewer sugars available, will be incentivized to tap more into fat stores for energy.
Plus, you get the benefit of doing the part that requires more technique (the weights) while you’re fresh, reducing risks.
The Ideal Solution (If You Can) Is to Separate the Workouts
Do you really want the best of both worlds with no interference? Don’t do them together.
The science is clear: the optimal solution to train both strength and endurance is to separate the sessions by at least 6-8 hours.
- Morning: Strength training (weights).
- Evening: Endurance training (running).
This way, the body has time to “reset” the molecular signals and (partially) recover its energy.
The even better solution? Different days.
How to Structure Your Perfect Week
Don’t complicate your life. If your goal is complete fitness, an ideal week might look like this:
- Monday: Strength (Total Body)
- Tuesday: Cardio (Running – Intervals/HIIT)
- Wednesday: Rest / Mobility
- Thursday: Strength (Total Body)
- Friday: Cardio (Running – Slow/Tempo Run)
- Saturday: Hybrid workout (e.g., MetCon circuit) or rest.
- Sunday: Rest
There is no single “right” answer. But there is a “right” answer for you. Choose your goal, establish your priority, and give your body a clear signal. Don’t drive it crazy.