Walk into any gym, and you’ll likely see the same routine: people hit the treadmill or elliptical first, then drag themselves to the weight rack. It seems logical—“warm up with cardio, then build muscle”—but here’s the truth: this order is wrong for most people, and 90% of fitness beginners (and even some seasoned gym-goers) are sabotaging their results without realizing it.
Let’s break down why cardio-first kills your strength gains. When you do cardio first, your body burns through its primary energy source: glycogen, stored in your muscles and liver. By the time you grab a dumbbell, your muscles are already low on fuel. This means you’ll lift lighter weights, struggle to finish sets, or sacrifice form—all of which slow muscle growth. A 2019 study in the Journal of Strength and Conditioning Research found that people who did cardio before strength training lifted 10-15% less weight than those who reversed the order. Even worse, poor form from fatigue increases your risk of injury—strained backs from rushed squats or tweaked shoulders from wobbly bench presses are far too common when energy runs low.
Worried about skipping your warm-up? You don’t have to. A 5-10 minute dynamic warm-up—arm circles, leg swings, bodyweight squats, or high knees—is enough to get blood flowing and loosen muscles. Save the cardio for after strength training, when your muscles are already fatigued but your heart is ready to push. This way, you’ll preserve energy for lifting, build more muscle, and still get the cardio benefits (like improved heart health and calorie burn). Plus, post-strength cardio can help flush lactic acid from your muscles, reducing soreness the next day—a win-win for anyone who hates that “can’t sit down” feeling after leg day.
What if you’re short on time and can only do one? Prioritize based on your goals. Want to build muscle or boost strength? Stick to strength first—muscle growth relies on progressive overload, which is hard to achieve when you’re already tired from cardio. Training for a marathon, 5K, or cycling event? Do cardio first 2-3 times a week to build endurance, but mix in 2-3 strength-first days to avoid losing muscle mass. Muscle helps with running efficiency and reduces joint stress, so ditching strength entirely is a mistake for endurance athletes too.
For those who love longer workouts (60+ minutes), there’s another option: split your cardio and strength. Do a 20-minute strength session in the morning, then a 30-minute walk or jog in the evening. This gives your body time to replenish glycogen between sessions, so you’re fresh for both. It’s also easier to fit into a busy schedule—short bursts of exercise are more sustainable than one long gym trip for many people.
The bottom line: The “cardio first” myth is holding you back. Next time you hit the gym, swap the order—you’ll feel stronger, lift heavier, and see better results faster. Whether you’re aiming for bigger biceps, a stronger core, or a faster 5K, getting the order right is the first step to success. Don’t be part of the 90% making this mistake—be the 10% getting it right, and watch your fitness goals become a reality.
